calpain and Breast-Neoplasms

The calpains are a family of intracellular cysteine proteases that function in a wide array of cellular activities, including cytoskeletal remodelling, survival and apoptosis. The ubiquitously expressed micro (µ)-calpain and milli (m)-calpain are archetypal family members that require calcium for function and can be inhibited by their endogenous inhibitor calpastatin. This review describes the role of the calpain system in the prognosis of breast cancer and disease progression, in addition to the role of the calpain system in the response to breast cancer treatments, including chemotherapeutic, endocrine and targeted therapies.

Topics: Breast Neoplasms; Calcium-Binding Proteins; Calpain; Disease Progression; Female; Humans; Prognosis

Modulation of apoptosis is emerging as a promising strategy for prevention and treatment of breast cancer and obesity because removal of mammary cancer cells and mature adipocytes through this process will result in decreasing tumor size and produce long-term reduction in adipose tissue mass. The hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) triggers apoptosis in breast cancer cells and adipocytes via the induction of the apoptotic Ca2+ signal - a sustained increase in concentration of intracellular Ca2+. This signal acts as an apoptotic initiator that directly recruits Ca2+-dependent apoptotic effectors, calpain and caspase 12, in breast cancer cells and adipocytes. Normal mammary epithelial cells are resistant to 1,25(OH)2D3-induced, Ca2+-mediated apoptosis because the mechanisms regulating Ca2+ in these cells do not sustain Ca2+ increase at the apoptosis-inducing level. Induction of apoptosis with 1,25(OH)2D3 in adipose tissue, particularly in the tumor-surrounding adipose tissue involved in tumor progression, can contribute to the anticancer effects of the hormone. The 1,25(OH)2D3-Ca2+ link between obesity and breast cancer supports the rationale to include Ca2+-dependent apoptotic proteases as molecular targets for the discovery of new therapeutic and preventive agents for breast cancer and obesity; it also supports the recommendation to maintain adequate or increased vitamin D and calcium intakes as one of the possible ways to protect against breast cancer and decrease adiposity.

Topics: Adipocytes; Animals; Apoptosis; Breast Neoplasms; Calcium Signaling; Calpain; Caspase 12; Cell Line, Tumor; Epithelial Cells; Female; Humans; Obesity; Vitamin D

Calcium signals induced by the Ca(2+) regulatory hormone 1,25(OH)(2)D(3) may determine the fate of the cancer cell. We have shown that, in breast cancer cell lines, 1,25(OH)(2)D(3) induces a sustained increase in concentration of intracellular Ca(2+) ([Ca(2+)](i)) by depleting the endoplasmic reticulum (ER) Ca(2+) stores via inositol 1,4,5-trisphosphate receptor/Ca(2+) release channel and activating Ca(2+) entry from the extracellular space via voltage-insensitive Ca(2+) channels. In normal cells, 1,25(OH)(2)D(3) triggered a transient Ca(2+) response via activation of voltage-dependent Ca(2+) channels, which were absent in breast cancer cells. The normal cells, but not breast cancer cells, expressed the Ca(2+) binding/buffering protein calbindin-D(28k) and were capable of buffering [Ca(2+)](i) increases induced by a mobilizer of the ER Ca(2+) stores, thapsigargin, or a Ca(2+) ionophore, ionomycin. The 1,25(OH)(2)D(3)-induced sustained increase in [Ca(2+)](i) in breast cancer cells was associated with induction of apoptotic cell death, whereas the transient [Ca(2+)](i) increase in normal cells was not. The forced expression of calbindin-D(28k) in cytosol or increase in the cytosolic Ca(2+) buffering capacity with the cell-permeant Ca(2+) buffer BAPTA prevented induction of apoptosis with 1,25(OH)(2)D(3) in cancer cells. The sustained increase in [Ca(2+)](i) in breast cancer cells was associated with activation of the Ca(2+)-dependent apoptotic proteases, mu-calpain and caspase-12, as evaluated with antibodies to active (cleaved) forms of the enzymes and the fluorogenic peptide substrates. Selective inhibition of the Ca(2+) binding sites of mu-calpain decreased apoptotic indices in the cancer cells treated with 1,25(OH)(2)D(3), thapsigargin, or ionomycin. The mu-calpain activation preceded expression/activation of caspase-12, and calpain was required for activation/cleavage of caspase-12. Certain non-calcemic vitamin D analogs (e.g., EB 1089) triggered a sustained [Ca(2+)](i) increase, activated Ca(2+)-dependent apoptotic proteases, and induced apoptosis in breast cancer cells in a fashion similar to that of 1,25(OH)(2)D(3). The 1,25(OH)(2)D(3)-induced transient Ca(2+) response in normal mammary epithelial cells was not accompanied by activation of mu-calpain and caspase-12. In conclusion, we have identified the novel apoptotic pathway in breast carcinoma cells treated with 1,25(OH)(2)D(3): increase in [Ca(2+)](i)-->mu-calpain activation-->caspase-12 activa

Topics: Apoptosis; Breast Neoplasms; Calcium; Calcium Signaling; Calpain; Humans; Vitamin D

Inflammatory breast cancer (IBC) is characterized by numerous tumor emboli especially within dermal lymphatics. The explanation remains a mystery.. This study combines experimental studies with two different IBC xenografts with image algorithmic studies utilizing human tissue microarrays (TMAs) of IBC vs non-IBC cases to support a novel hypothesis to explain IBC's sina qua non signature of florid lymphovascular emboli.. In the human TMAs, compared to tumor features like nuclear grade (size), mitosis and Ki-67 immunoreactivity which show that IBC is only modestly more proliferative with larger nuclei than non-IBC, what really sets IBC apart is the markedly greater number of tumor emboli and distinctly smaller emboli whose numbers indicate geometric or exponential differences between IBC and non-IBC. In the experimental xenograft studies, Mary-X gives rise to tight spheroids in vitro which exhibit dynamic budding into smaller daughter spheroids whereas Karen-X exhibits only loose non-budding aggregates. Furthermore Mary-X emboli also bud dramatically into smaller daughter emboli in vivo. The mechanism that regulates this involves the generation of E-cad/NTF1, a calpain-mediated cleavage 100 kDa product of 120 kDa full length membrane E-cadherin. Inhibiting this calpain-mediated cleavage of E-cadherin by blocking either the calpain site of cleavage (SC) or the site of binding (SB) with specific decapeptides that both penetrate the cell membrane and mimic either the cleavage site or the binding site on E-cadherin, inhibits the generation of E-cad/NTF1 in a dose-dependent manner, reduces spheroid compactness and decreases budding.. Since E-cad/NFT1 retains the p120ctn binding site but loses the α-and β-catenin sites, promoting its 360° distribution around the cell's membrane, the vacilating levels of this molecule trigger budding of both the spheroids as well as the emboli. Recurrent and geometric budding of parental emboli into daughter emboli then would account for the plethora of emboli seen in IBC.

Topics: Animals; Breast Neoplasms; Cadherins; Calpain; Female; Humans; Inflammatory Breast Neoplasms; Neoplastic Cells, Circulating; Spheroids, Cellular

Orai3 calcium (Ca

Topics: Breast Neoplasms; Calcium; Calcium Channels; Calpain; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cell Shape; Female; Focal Adhesion Protein-Tyrosine Kinases; Humans; Protein Binding

Human epidermal growth factor receptor 2 (HER2) is composed of an extracellular domain (ECD), a lipophilic transmembrane region and an intracellular domain (ICD). The most commonly used method to determine the status of HER2 is immunohistochemistry. However, false‑negative results are sometimes given, which causes some patients to lose the opportunity for anti‑HER2 therapy. We found that calpain‑10 may prohibit HER2‑ECD into peripheral blood resulting in a HER2‑negative result by the immunohistochemical method. We enrolled 289 patients into our experiment to assess the relationship between sHER2‑ECD and calpain‑10. The results showed that there was a positive correlation between sHER2‑ECD and calpain‑10. Moreover, we also investigated the prognostic values of sHER2‑ECD and calpain‑10 in breast cancer patients. According to the follow‑up results, positive sHER2‑ECD and tissue calpain‑10 were indicative of a poor prognosis in breast cancer patients. Subsequently, we further validated the relationship between the two molecules in in vitro experiments. In the in vitro experiments, the level of HER2‑ECD in the culture medium was increased or decreased with a decrease or increase in calpain‑10 by transfection technology, showing an inverse association. The results indicated that sHER2‑ECD and tissue calpain‑10 levels were powerful factors to assess the status of HER2. In combination with tissue HER2 detection, the occurrence of false‑negative HER2 was reduced, providing patients with additional treatment opportunities. In conclusion, sHER2‑ECD and tissue calpain‑10 may be used as new prognostic indices for breast cancer.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Breast Neoplasms; Calpain; Cell Line, Tumor; Female; Gene Expression Regulation, Neoplastic; Humans; MCF-7 Cells; Middle Aged; Neoplasm Grading; Neoplasm Staging; Prognosis; Protein Domains; Receptor, ErbB-2; Up-Regulation

Breast cancer is a heterogeneous disease with different biological outcome and ability to acquire resistance to therapy. The calpain family of proteases and androgen receptor (AR) are implicated in breast cancer pathogenesis and progression and are potential targets for novel treatment regimens. The aim of this study was to investigate the expression of calpain-1 and AR in breast cancer and to correlate their expression with clinicopathological variables and prognosis of patients. In this study we enrolled 219 breast cancer patients with long term follow-up information available. Immunohistochemical methods on a tissue microarray were used to investigate expression of calpain-1 and AR in tumor cells. The expression of calpain-1 and AR both differed significantly between the tumor subtypes of patients (p = 0.002 and p = 0.042 respectively). High calpain-1 expression was associated with patient's age over 50 years (p = 0.005) and positive ER status (p = 0.009), but not with other clinicopathological variables. Women with AR negative breast cancers were more likely to be older (p = 0.016), to have bigger tumors (p = 0.032), higher stage of the disease (p = 0.026), presence of exulceration (p = 0.017), negative ER status (p = 0.007) and higher Ki-67 proliferative index (p = 0.027). Calpain-1 expression was not associated with breast cancer specific overall survival in the total cohort of patients, however low calpain-1 expression was associated with adverse survival (p = 0.018) in triple negative subgroup of patients. Low calpain-1 expression was also associated with significantly shorter 5-year disease-free survival in total cohort of patients (p = 0.03). AR status was not associated with overall and disease-free survival of patients. This study has demonstrated that the expression of calpain-1 and androgen receptors are associated with important clinicopathological variables. The expression of calpain-1 was associated with improved disease-free survival of all analyzed patients and with improved overall survival of triple negative breast cancer patients.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Breast Neoplasms; Calpain; Disease-Free Survival; Female; Gene Expression Regulation, Neoplastic; Humans; Immunohistochemistry; Ki-67 Antigen; Male; Middle Aged; Receptors, Androgen; Receptors, Estrogen; Receptors, Progesterone

The extracellular matrix protein fibronectin (FN) facilitates tumorigenesis and the development of breast cancer. Inhibition of the FN-induced cellular response is a potential strategy for breast cancer treatment. In the present study, we investigated the effects of the flavonoid baicalein on FN-induced epithelial-mesenchymal transition (EMT) in MCF-10A breast epithelial cells and in a transgenic mouse MMTV-polyoma middle T antigen breast cancer model (MMTV-PyMT). Baicalein inhibited FN-induced migration, invasion, and F-actin remodeling. Baicalein also suppressed FN-induced downregulation of the epithelial markers E-cadherin and ZO-1 and upregulation of the mesenchymal markers N-cadherin, vimentin, and Snail. Further investigation revealed that calpain-2 was involved in baicalein suppression of FN-induced EMT. Baicalein significantly decreased FN-enhanced calpain-2 expression and activation by suppressing its plasma membrane localization, substrate cleavage, and degradation of its endogenous inhibitor calpastatin. Overexpression of calpain-2 in MCF-10A cells by gene transfection partially blocked the inhibitory effect of baicalein on FN-induced EMT changes. In addition, baicalein inhibited calpain-2 by decreasing FN-increased intracellular calcium ion levels and extracellular signal-regulated protein kinases activation. Baicalein significantly decreased tumor onset, growth, and pulmonary metastasis in a spontaneous breast cancer MMTV-PyMT mouse model. Baicalein also reduced the expression of FN, calpain-2, and vimentin, but increased E-cadherin expression in MMTV-PyMT mouse tumors. Overall, these results revealed that baicalein markedly inhibited FN-induced EMT by inhibiting calpain-2, thus providing novel insights into the pharmacological action and mechanism of baicalein. Baicalein may therefore possess therapeutic potential for the treatment of breast cancer though interfering with extracellular matrix-cancer cell interactions.

Topics: Animals; Breast Neoplasms; Butadienes; Cadherins; Calcium; Calpain; Cell Line, Tumor; Epithelial-Mesenchymal Transition; Extracellular Signal-Regulated MAP Kinases; Female; Fibronectins; Flavanones; Humans; Kaplan-Meier Estimate; Mice; Mice, Transgenic; Nitriles; Up-Regulation; Zonula Occludens-1 Protein

Doxorubicin is commonly using chemotherapeutic agents for breast cancer. However, doxorubicin has limitations in clinical use because of dose-dependent cardiotoxicity and drug resistance. Despite of previously reported studies about mechanisms of doxorubicin resistance including overexpression of P-gp and abnormal expression and mutation of topoisomerase IIα, resistance to this agent still abundantly occur and is regarded as a major obstacle to successful treatment.. We have established doxorubicin resistant T47D cells. Intracellular calcium and ROS levels and calpain activity were measured using fluorometric experiments. Cell viability assay, cell cycle analysis, immunofluorescence and western blot analysis were performed to evaluate m-calpain specific truncation of topoisomerase IIα and molecular mechanism in doxorubicin resistant cells.. We observed that doxorubicin treatment increased intracellular calcium and ROS (Reactive Oxygen Species) in parental and doxorubicin resistant T47D cells. The increases in intracellular calcium and ROS were much greater in doxorubicin resistant T47D cells, which led to higher activity of calpains. Hyperactivated m-calpain, but not μ-calpain, specifically induced cleavage of topoisomerase IIα and accumulation of truncated topoisomerase IIα in the cytoplasm. The increase in cytoplasmic truncated topoisomerase IIα reduced the efficacy of doxorubicin. Doxorubicin resistant T47D cells, with hyperactivated m-calpain and truncated cytosolic topoisomerase IIα, obtained cross-resistance to other topoisomerase II-targeting drugs.. Hyperactivated m-calpain induced cytoplasmic accumulation of truncated topoisomerase IIα in doxorubicin resistant T47D cells.. These data provide a new mechanism of doxorubicin resistance and suggest a novel strategy for overcoming drug resistance in topoisomerase IIα-targeting therapy.

Topics: Breast Neoplasms; Calcium Signaling; Calpain; DNA Topoisomerases, Type II; Doxorubicin; Drug Resistance, Neoplasm; Enzyme Activation; Female; Humans; Neoplasm Proteins; Poly-ADP-Ribose Binding Proteins; Reactive Oxygen Species

Nuclear forkhead box protein P1 (N-FOXP1) expression in invasive breast cancer has been documented in the literature. However, the FOXP1 expression patterns at different stages of breast cancer progression are largely unknown, and the significance of cytoplasmic FOXP1 (C-FOXP1) expression in breast cancer has not been well illustrated. The aims of this study were to investigate FOXP1 expression patterns in invasive ductal carcinoma (IDC), ductal carcinoma in situ (DCIS), atypical ductal hyperplasia (ADH) and usual ductal hyperplasia (UDH), and to analyze the clinicopathological relevance of C-FOXP1 and its prognostic value in IDC.. N-FOXP1 and C-FOXP1 expression in cases of IDC, DCIS, ADH and UDH was determined using immunohistochemistry. The correlation between C-FOXP1 expression and clinicopathological parameters as well as the overall survival (OS) and disease-free survival (DFS) rates of patients with IDC were analyzed.. Exclusive N-FOXP1 expression was found in 85.0% (17/20), 40.0% (8/20), 12.2% (5/41) and 10.8% (9/83) of UDH, ADH, DCIS, and IDC cases, respectively, and exclusive C-FOXP1 expression was observed in 0% (0/20), 0% (0/20), 4.9% (2/41), and 31.3% (26/83) of the cases, respectively. Both N- and C-FOXP1 staining were observed in 15.0% (3/20), 60.0% (12/20), 82.9% (34/41) and 48.2% (40/83) of the above cases, respectively, while complete loss of FOXP1 expression was observed in only 9.6% (8/83) of IDC cases. Estrogen receptor (ER) expression in C-FOXP1-positive IDC cases (31/66, 47.0%) was significantly lower than that in C-FOXP1-negative cases (13/17, 76.5%) (p = 0.030). Calpain II expression was observed in 83.3% (55/66) of C-FOXP1-positive IDC cases, which was significantly higher than that in C-FOXP1-negative cases (9/17, 52.9%) (p = 0.007). Calpain II was significantly associated with pAKT (p = 0.029), pmTOR (p = 0.011), p4E-BP1 (p < 0.001) and p-p70S6K (p = 0.003) expression levels. The 10-year OS and DFS rates of the C-FOXP1-positive patients were 60.5% and 48.7%, respectively, both of which were lower than those of the C-FOXP1-negative patients (93.3, 75.3%). The OS curve showed a dramatic impact of C-FOXP1 status on OS (p = 0.045).. Cytoplasmic relocalization of FOXP1 protein was a frequent event in breast IDC. Calpain II might play an important role in nucleocytoplasmic trafficking of FOXP1 and the AKT pathway might be involved in this process. C-FOXP1 expression was inversely associated with ER expression and might be a predictor of poor OS in patients with IDC.

Topics: Adult; Biomarkers, Tumor; Breast Carcinoma In Situ; Breast Neoplasms; Calpain; Carcinoma, Ductal, Breast; Carcinoma, Intraductal, Noninfiltrating; Cytoplasm; Disease-Free Survival; Female; Forkhead Transcription Factors; Humans; Kaplan-Meier Estimate; Middle Aged; Prognosis; Protein Transport; Receptors, Estrogen; Repressor Proteins

We have previously described a novel pathway controlling drug resistance, epithelial-to-mesenchymal transition (EMT) and stemness in breast cancer cells. Upstream in the pathway, three miRs (miR-106b, miR-93 and miR-25) target EP300, a transcriptional activator of E-cadherin. Upregulation of these miRs leads to the downregulation of EP300 and E-cadherin with initiation of an EMT. However, miRs regulate the expression of many genes, and the contribution to EMT by miR targets other than EP300 cannot be ruled out.. We used lentiviruses expressing EP300-targeting shRNA to downregulate its expression in MCF-7 cells as well as an EP300-knocked-out colon carcinoma cell line. An EP300-expression plasmid was used to upregulate its expression in basal-like CAL51 and MDA-MB-231 breast cancer cells. Drug resistance was determined by short-term proliferation and long-term colony formation assays. Stemness was determined by tumour sphere formation in both soft agar and liquid cultures as well as by the expression of CD44/CD24/ALDH markers. Gene expression microarray analysis was performed in MCF-7 cells lacking EP300. EP300 expression was analysed by immunohistochemistry in 17 samples of metaplastic breast cancer.. Cells lacking EP300 became more resistant to paclitaxel whereas EP300 overexpression increased their sensitivity to the drug. Expression of cancer stem cell markers, as well as tumour sphere formation, was also increased in EP300-depleted cells, and was diminished in EP300-overexpressing cells. The EP300-regulated gene signature highlighted genes associated with adhesion (CEACAM5), cytoskeletal remodelling (CAPN9), stemness (ABCG2), apoptosis (BCL2) and metastasis (TGFB2). Some genes in this signature were also validated in a previously generated EP300-depleted model of breast cancer using minimally transformed mammary epithelial cells. Importantly, two key genes in apoptosis and stemness, BCL2 and ABCG2, were also upregulated in EP300-knockout colon carcinoma cells and their paclitaxel-resistant derivatives. Immunohistochemical analysis demonstrated that EP300 expression was low in metaplastic breast cancer, a rare, but aggressive form of the disease with poor prognosis that is characterized by morphological and physiological features of EMT.. EP300 plays a major role in the reprogramming events, leading to a more malignant phenotype with the acquisition of drug resistance and cell plasticity, a characteristic of metaplastic breast cancer.

Topics: ATP Binding Cassette Transporter, Subfamily G, Member 2; Breast Neoplasms; Calpain; Carcinoembryonic Antigen; Cell Plasticity; Cell Proliferation; Drug Resistance, Neoplasm; E1A-Associated p300 Protein; Female; Gene Expression Regulation, Neoplastic; GPI-Linked Proteins; Humans; Lentivirus; MCF-7 Cells; Neoplasm Metastasis; Neoplasm Proteins; Neoplastic Stem Cells; Paclitaxel; Proto-Oncogene Proteins c-bcl-2; Transforming Growth Factor beta2

In patients with breast cancer and lung cancer, chymotrypsin-like and caspase-like activities of proteasomes and total activity of calpains in the primary tumor nodes and lymphogenic metastasis are elevated in comparison with the corresponding normal tissues. The development of lymphogenic metastases of breast cancer and lung cancer was associated with opposite change in caspase-like activity of proteasomes. These results can be useful for the development of methods for evaluation of aggressiveness of breast and lung cancer.

Topics: Adult; Breast Neoplasms; Calpain; Female; Humans; Lung Neoplasms; Middle Aged; Neoplasm Metastasis; Proteasome Endopeptidase Complex

Impaired apoptosis is one of the hallmarks of cancer. Caspase-3 and -8 are key regulators of the apoptotic response and have been shown to interact with the calpain family, a group of cysteine proteases, during tumorigenesis. The current study sought to investigate the prognostic potential of caspase-3 and -8 in breast cancer, as well as the prognostic value of combinatorial caspase and calpain expression. A large cohort (n = 1902) of early stage invasive breast cancer patients was used to explore the expression of caspase-3 and -8. Protein expression was examined using standard immunohistochemistry on tissue microarrays. High caspase-3 expression, but not caspase-8, is significantly associated with adverse breast cancer-specific survival (P = 0.008 and P = 0.056, respectively). Multivariate analysis showed that caspase-3 remained an independent factor when confounding factors were included (hazard ratio (HR) 1.347, 95% confidence interval (CI) 1.086-1.670; P = 0.007). The analyses in individual subgroups demonstrated the significance of caspase-3 expression in clinical outcomes in receptor positive (ER, PR or HER2) subgroups (P = 0.001) and in non-basal like subgroup (P = 0.029). Calpain expression had been previously assessed. Significant association was also found between high caspase-3/high calpain-1 and breast cancer-specific survival in the total patient cohort (P = 0.005) and basal-like subgroup (P = 0.034), as indicated by Kaplan-Meier analysis. Caspase-3 expression is associated with adverse breast cancer-specific survival in breast cancer patients, and provides additional prognostic values in distinct phenotypes. Combinatorial caspase and calpain expression can predict worse prognosis, especially in basal-like phenotypes. The findings warrant further validation studies in independent multi-centre patient cohorts.

Topics: Adolescent; Adult; Aged; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Carcinoma; Caspase 3; Caspase 8; Cell Line, Tumor; Estrogens; Female; Genes, erbB-2; Humans; Kaplan-Meier Estimate; Middle Aged; Neoplasm Proteins; Neoplasms, Hormone-Dependent; Progesterone; Prognosis; Tissue Array Analysis; Young Adult

Multidrug resistance in cancer (MDR) occurs when tumours become crossresistant to a range of different anticancer agents. One mechanism by which MDR can be acquired is through cell to cell communication pathways. Membrane-derived microparticles (MPs) are emerging as important signaling molecules in this process. MPs are released from most eukaryotic cells and transfer functional proteins and nucleic acids to recipient cells conferring deleterious traits within the cancer cell population including MDR, metastasis, and angiogenesis. MP formation is known to be dependent on calpain, an intracellular cysteine protease which acts to cleave the cytoskeleton underlying the plasma membrane, resulting in cellular surface blebbing Objective: To establish the role of calpain in vesiculation in malignant and non-malignant cells by 1) comparing membrane vesiculation at rest and following the release of intracellular calcium, and 2) comparing vesiculation in the presence and absence of calpain inhibitor II (ALLM).. This study examines the differences in vesiculation between malignant and non-malignant cells using high-resolution Atomic Force Microscopy (AFM). HBEC, MBE-F, MCF-7, and MCF- 7/Dx cells were analysed at rest and following treatment with calcium ionophore A23187 for 18 hours. Vesiculation of calcium activated and resting malignant and non-malignant cells was also assessed after 18 hour treatment of calpain inhibitor II (ALLM).. We demonstrate that malignant MCF-7 and MCF-7/Dx cells have an intrinsically higher degree of vesiculation at rest when compared to non-malignant human brain endothelial cells (HBEC) and human mammary epithelial cells (MBE-F). Cellular activation with the calcium ionophore A23187 resulted in an increase in vesiculation in all cell types. We show that calpain-mediated MP biogenesis is the dominant pathway at rest in malignant cells as vesiculation was shown to be inhibited with calpain inhibitor II (ALLM).. These results suggest that differences in the biogenic pathways exist in malignant and non-malignant cells and have important implications in defining novel strategies to selectively target malignant cells for the circumvention of deleterious traits acquired through intercellular exchange of extracellular vesicles.

Topics: Breast Neoplasms; Calcium; Calpain; Cell Line, Tumor; Humans; Microscopy, Atomic Force

Calpain-1 is a ubiquitously expressed calcium-activated intracellular cysteine protease. Altered expression of calpain system proteins has been implicated in cancer progression and response to chemotherapy.. The aim of the current study was to confirm previous data that suggested that calpain-1 expression is associated with relapse-free survival in trastuzumab-treated breast cancer patients (n = 93). An expanded patient cohort from Nottingham (n = 194; including 72 of the previous cohort) and an independent patient cohort from Newcastle (n = 87) were used. All patients received trastuzumab following adjuvant therapy according to local guidelines with expression of calpain-1 investigated using standard immunohistochemistry. Results show that calpain-1 expression is associated with relapse-free survival in both the Nottingham (P = 0.01) and Newcastle (P = 0.019) cohorts, with high expression associated with adverse relapse-free survival. Expression was also associated with poor relapse-free survival when patient cohorts were combined (n = 281, P = 0.01). Calpain-1 remained, from multivariate analysis, an independent marker for relapse-free survival in the Newcastle cohort [hazard ratio (HR) = 5.169; 95% confidence interval (CI) 1.468-18.200; P = 0.011].. Calpain-1 expression is associated with poor relapse-free survival in breast cancer patients treated with trastuzumab. Further work is warranted to standardize and develop methodology with a view to potentially introducing assessment of this important biomarker into clinical practice.

Topics: Adult; Antineoplastic Agents; Biomarkers, Tumor; Breast; Breast Neoplasms; Calpain; Chemotherapy, Adjuvant; Cohort Studies; Disease-Free Survival; Female; Humans; Immunohistochemistry; Kaplan-Meier Estimate; Prognosis; Proportional Hazards Models; Recurrence; Tissue Array Analysis; Trastuzumab

CAPNS1 is essential for the stability and function of ubiquitous CAPN1 and CAPN2. Calpain modulates by proteolytic cleavage many cellular substrates and its activity is often deregulated in cancer cells, therefore calpain inhibition has been proposed as a therapeutical strategy for a number of malignancies. Here we show that CAPNS1 depletion is coupled to impairment of MCF7 and MCF10AT cell lines growth on plate and defective architecture of mammary acini derived from MCF10A cells. In soft agar CAPNS1 depletion leads to cell growth increase in MCF7, and decrease in MCF10AT cells. In both MCF7 and MCF10AT, CAPNS1 depletion leads to the enlargement of the stem cell compartment, as demonstrated by mammosphere formation assays and evaluation of stem cell markers by means of FACS and western blot analysis. Accordingly, activation of calpain by thapsigargin treatment leads to a decrease in the stem cell reservoir. The expansion of the cancer stem cell population in CAPNS1 depleted cells is coupled to a defective shift from symmetric to asymmetric division during mammosphere growth coupled to a decrease in NUMB protein level.

Topics: Animals; Breast Neoplasms; Calpain; Cell Proliferation; Cells, Cultured; Female; Humans; MCF-7 Cells; Mice; Neoplastic Stem Cells

Calpain is an intracellular Ca(2+)-regulated protease system whose substrates include proteins involved in proliferation, survival, migration, invasion, and sensitivity to therapeutic drugs. Genetic disruption of calpain attenuated the tumorigenic potential of breast cancer cells and hypersensitized cells to 17AAG, an inhibitor of the molecular chaperone HSP90. Calpain-1 or -2 overexpression rendered cells resistant to 17AAG, whereas downregulation or inhibition of calpain-1/2 led to increased cell death in multiple breast cancer cell lines, including models of HER2(+) (SKBR3) and triple-negative basal-cell-like (MDA-MB-231) breast cancer. In an MDA-MB-231 orthotopic xenograft model, calpain knockdown or 17AAG treatment independently attenuated tumor growth and metastasis, while the combination was most effective. Calpain knockdown was associated with increased 17AAG-induced degradation of the HSP90 clients cyclin D1 and AKT and multidrug resistance protein 2, which correlated with increased expression of antimitogenic p27(KIP1) and proapoptotic BIM proteins. Like other therapeutics, 17AAG can be effluxed by specific ABC transporters. Calpain expression positively correlated with the expression of P glycoprotein in mouse embryonic fibroblasts. Importantly, we show that calpain affects ABC transporter function and efflux of clinically relevant doxorubicin. These observations provide a compelling rationale for exploring the combination of calpain inhibition with new or existing cancer therapeutics.

Topics: Animals; Benzoquinones; Breast Neoplasms; Calpain; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Combined Modality Therapy; Female; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Humans; Lactams, Macrocyclic; Mice; Neoplasm Metastasis; Xenograft Model Antitumor Assays

The calpains are a family of intracellular cysteine proteases that function in a variety of important cellular functions, including cell signalling, motility, apoptosis and survival. In early invasive breast cancer expression of calpain-1, calpain-2 and their inhibitor, calpastatin, have been associated with clinical outcome and clinicopathological factors.The expression of calpain-1, calpain-2 and calpastatin was determined using immunohistochemistry on core biopsy samples, in a cohort of large but operable inflammatory and non-inflammatory primary breast cancer patients treated with neoadjuvant chemotherapy. Information on treatment and prognostic variables together with long-term clinical follow-up was available for these patients. Diagnostic pre-chemotherapy core biopsy samples and surgically excised specimens were available for analysis.Expression of calpastatin, calpain-1 or calpain-2 in the core biopsies was not associated with breast cancer specific survival in the total patient cohort; however, in patients with non-inflammatory breast cancer, high calpastatin expression was significantly associated with adverse breast cancer-specific survival (P=0.035), as was low calpain-2 expression (P=0.031). Low calpastatin expression was significantly associated with adverse breast cancer-specific survival of the inflammatory breast cancer patients (P=0.020), as was low calpain-1 expression (P=0.003).In conclusion, high calpain-2 and low calpastatin expression is associated with improved breast cancer-specific survival in non-inflammatory large but operable primary breast cancer treated with neoadjuvant chemotherapy. In inflammatory cases, high calpain-1 and high calpastatin expression is associated with improved breast cancer-specific survival. Determining the expression of these proteins may be of clinical relevance. Further validation, in multi-centre cohorts of breast cancer patients treated with neoadjuvant chemotherapy, is warranted.

Topics: Adult; Aged; Aged, 80 and over; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Female; Humans; Immunohistochemistry; Inflammatory Breast Neoplasms; Middle Aged; Neoadjuvant Therapy; Prognosis; Survival Analysis; Young Adult

Cleavage of adhesion proteins is the first step for physiological clearance of undesired cells during postlactational regression of the mammary gland, but also for cell migration in pathological states such as breast cancer. The intracellular Ca(2+)-dependent proteases, calpains (CAPNs), are known to cleave adhesion proteins. The isoform-specific function of CAPN1 and CAPN2 was explored and compared in two models of cell adhesion disruption: mice mammary gland during weaning-induced involution and breast cancer cell lines according to tumor subtype classification. In both models, E-cadherin, β-catenin, p-120, and talin-1 were cleaved as assessed by western blot analysis. Both CAPNs were able to cleave adhesion proteins from lactating mammary gland in vitro Nevertheless, CAPN2 was the only isoform found to co-localize with E-cadherin in cell junctions at the peak of lactation. CAPN2/E-cadherin in vivo interaction, analyzed by proximity ligation assay, was dramatically increased during involution. Calpain inhibitor administration prevented the cytosolic accumulation of truncated E-cadherin cleaved by CAPN2. Conversely, in breast cancer cells, CAPN2 was restricted to the nuclear compartment. The isoform-specific expression of CAPNs and CAPN activity was dependent on the breast cancer subtype. However, CAPN1 and CAPN2 knockdown cells showed that cleavage of adhesion proteins and cell migration was mediated by CAPN1, independently of the breast cancer cell line used. Data presented here suggest that the subcellular distribution of CAPN1 and CAPN2 is a major issue in target-substrate recognition; therefore, it determines the isoform-specific role of CAPNs during disruption of cell adhesion in either a physiological or a pathological context.

Topics: Animals; Breast; Breast Neoplasms; Calpain; Cell Adhesion; Female; Humans; Lactation; Mice

Activation of Epithelial-to-Mesenchymal Transition (EMT) is important for tumor metastasis. Although growth factors such as TGFβ and EGF have been shown to induce EMT in breast epithelial cells, the mechanism resulting in migration is not well understood. Herein, we provide evidence that Ca2+ entry into the cell, especially upon store-depletion, plays an important role in TGFβ-induced EMT by promoting cellular migration and potentially leading to metastasis. The increased migration by TGFβ in non-cancerous cells was due to the loss of E-cadherin along with a subsequent increase in N-cadherin levels. Importantly, TGFβ-treatment increases store-mediated Ca2+ entry, which was essential for the activation of calpain leading to the loss of E-cadherin and MMP activation. Inhibition of Ca2+ entry by using Ca2+ channel blocker SKF-96365, significantly decreased Ca2+ entry, decreased TGFβ-induced calpain activation, and suppressed the loss of E-cadherin along with inhibiting cell migration. Furthermore, TRPC1 function as an endogenous Ca2+ entry channel and silencing of either TRPC1 or its activator, STIM1, significantly decreased TGFβ induced Ca2+ entry, inhibited TGFβ-mediated calpain activation and cell migration. In contrast, overexpression of TRPC1 showed increased Ca2+ entry and promoted TGFβ-mediated cell migration. Moreover, increased TRPC1 expression was observed in ductal carcinoma cells. Together these results suggest that disrupting Ca2+ influx via TRPC1/STIM1 mechanism reduces calpain activity, which could restore intercellular junction proteins thereby inhibiting EMT induced motility.

Topics: Antigens, CD; Breast Neoplasms; Cadherins; Calcium Signaling; Calpain; Cell Line, Tumor; Cell Movement; Epithelial-Mesenchymal Transition; Female; Humans; Matrix Metalloproteinases; Membrane Potentials; Neoplasm Metastasis; Neoplasm Proteins; RNA Interference; Stromal Interaction Molecule 1; Time Factors; Transfection; Transforming Growth Factor beta; TRPC Cation Channels

Mounting in vitro, in vivo and clinical evidence suggest an important role for filopodia in driving cancer cell invasion. Using a high-throughput microscopic-based drug screen, we identify FDA-approved calcium channel blockers (CCBs) as potent inhibitors of filopodia formation in cancer cells. Unexpectedly, we discover that L-type calcium channels are functional and frequently expressed in cancer cells suggesting a previously unappreciated role for these channels during tumorigenesis. We further demonstrate that, at filopodia, L-type calcium channels are activated by integrin inside-out signalling, integrin activation and Src. Moreover, L-type calcium channels promote filopodia stability and maturation into talin-rich adhesions through the spatially restricted regulation of calcium entry and subsequent activation of the protease calpain-1. Altogether we uncover a novel and clinically relevant signalling pathway that regulates filopodia formation in cancer cells and propose that cycles of filopodia stabilization, followed by maturation into focal adhesions, directs cancer cell migration and invasion.

Topics: Animals; Breast Neoplasms; Calcium Channels, L-Type; Calpain; Cell Line, Tumor; Female; Gene Expression Regulation, Neoplastic; Humans; Integrins; Mice; Myosins; Neoplasm Invasiveness; Pseudopodia; Signal Transduction

The scaffolding protein, hematopoietic PBX-interacting protein (HPIP/PBXIP1), regulates cell migration necessary for cancer cell dissemination. However, the mechanism that governs this process remains unknown. We show here that HPIP expression is associated with stages of breast cancer where cell dissemination results in poor patient outcome. Our investigation finds a novel association of HPIP with focal adhesion kinase (FAK) regulating FA dynamics. Interestingly, this interaction that led to activation of FAK protein was mediated by the C-terminal domain of HPIP and not the typical integrin-binding motif. Further, short hairpin RNA-mediated knockdown of FAK expression significantly reduced HPIP-induced cell migration indicating participation of FAK pathway. Live-cell time-lapse imaging and biochemical analysis further established the role of HPIP in microtubule-induced FA disassembly. We also found that HPIP-mediated MAPK activation led to phosphorylation and subsequent activation of calpain2, and the activated calpain2 in turn proteolyses FA protein, talin. Interestingly, HPIP is also proteolysed by calpain2 in breast cancer cells. The proteolysis of HPIP and talin by calpain2, and the activation of calapin2 by HPIP-mediated MAPK phosphorylation, is a novel regulatory axis to modulate the cell migration signal. Together, we have determined HPIP as a novel activator of FAK and a new substrate of calpain2. These molecular interactions between HPIP and FAK, and HPIP and calpain2 regulate cell adhesion and migration through modulation of FA dynamics.

Topics: Breast Neoplasms; Calpain; Carcinoma, Ductal, Breast; Cell Adhesion; Cell Movement; Enzyme Activation; Female; Focal Adhesion Kinase 1; Focal Adhesions; Gene Expression; Humans; Intracellular Signaling Peptides and Proteins; Microtubules; Mitogen-Activated Protein Kinases; Phosphorylation; Protein Interaction Domains and Motifs; Protein Processing, Post-Translational

Up-regulation of the cytoskeleton linker protein ezrin frequently occurs in aggressive cancer types and is closely linked with metastatic progression. However, the underlying molecular mechanisms detailing how ezrin is involved in the invasive and metastatic phenotype remain unclear. Here we report a novel function of ezrin in regulating focal adhesion (FA) and invadopodia dynamics, two key processes required for efficient invasion to occur. We show that depletion of ezrin expression in invasive breast cancer cells impairs both FA and invadopodia turnover. We also demonstrate that ezrin-depleted cells display reduced calpain-mediated cleavage of the FA and invadopodia-associated proteins talin, focal adhesion kinase (FAK), and cortactin and reduced calpain-1-specific membrane localization, suggesting a requirement for ezrin in maintaining proper localization and activity of calpain-1. Furthermore, we show that ezrin is required for cell directionality, early lung seeding, and distant organ colonization but not primary tumor growth. Collectively our results unveil a novel mechanism by which ezrin regulates breast cancer cell invasion and metastasis.

Topics: Animals; Breast Neoplasms; Calpain; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cytoskeletal Proteins; Cytoskeleton; Extracellular Matrix; Female; Focal Adhesion Protein-Tyrosine Kinases; Focal Adhesions; HEK293 Cells; Heterografts; Human Umbilical Vein Endothelial Cells; Humans; Mice; Neoplasm Metastasis; Podosomes; Talin

Fulvestrant (ICI 182 780, ICI) has been used in treating patients with hormone-sensitive breast cancer, yet initial or acquired resistance to endocrine therapies frequently arises and, in particular, cancer recurs as metastasis. We demonstrate here that both 17-beta-estradiol (E2) and ICI enhance cell adhesion to matrigel in MCF-7 breast cancer cells, with increased autolysis of calpain 1 (large subunit) and proteolysis of focal adhesion kinase (FAK), indicating calpain activation. Additionally, either E2 or ICI induced down-regulation of estrogen receptor α without affecting G protein coupled estrogen receptor 30 (GPR30) expression. Interestingly, GPR30 agonist G1 triggered calpain 1 autolysis but not calpain 2, whereas ER agonist diethylstilbestrol caused no apparent calpain autolysis. Furthermore, the actions of E2 and ICI on calpain and cell adhesion were tremendously suppressed by G15, or knockdown of GPR30. E2 and ICI also induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), and suppression of ERK1/2 phosphorylation by U0126 profoundly impeded calpain activation triggered by estrogenic and antiestrogenic stimulations indicating implication of ERK1/2 in the GPR30-mediated action. Lastly, the E2- or ICI-induced cell adhesion was dramatically impaired by calpain-specific inhibitors, ALLN or calpeptin, suggesting requirement of calpain in the GPR30-associated action. These data show that enhanced cell adhesion by E2 and ICI occurs via a novel GPR30-ERK1/2-calpain pathway. Our results indicate that targeting the GPR30 signaling may be a potential strategy to reduce metastasis and improve the efficacy of antiestrogens in treatment of advanced breast cancer.

Topics: Breast Neoplasms; Calpain; Cell Adhesion; Collagen; Down-Regulation; Drug Combinations; Estradiol; Estrogen Antagonists; Estrogens; Female; Fulvestrant; Gene Silencing; Humans; Laminin; MAP Kinase Signaling System; MCF-7 Cells; Phosphorylation; Proteoglycans; Receptors, Estrogen; Receptors, G-Protein-Coupled; Signal Transduction

We have reported that the oncoprotein hepatitis B X-interacting protein (HBXIP) plays a crucial role in the promotion of migration of breast cancer cells. Lamellipodia and filopodia protrusions play fundamental roles, involving dynamic cytoskeleton reorganization in the metastasis of cancer. Here, we observed that the expression levels of both HBXIP and Calpain small subunit 1 (Capn4) were very high in clinical metastatic lymph nodes of breast tumor. Then, we found that HBXIP was able to up-regulate Capn4 at the levels of promoter, mRNA and protein in breast cancer cells through activation of ERK1/2. Moreover, we showed that HBXIP activated ERK1/2 through up-regulating MEKK2. In function, we revealed that HBXIP increased the filopodia formation through Capn4, resulting in cell migration. Thus, we conclude that the oncoprotein HBXIP enhances the migration of breast cancer through increasing filopodia formation involving MEKK2/ERK1/2/Capn4 signaling. Therapeutically, HBXIP may serve as a novel target in breast cancer.

Topics: Adaptor Proteins, Signal Transducing; Animals; Breast Neoplasms; Calpain; Cell Line, Tumor; Cell Movement; Female; Heterografts; Humans; Male; MAP Kinase Kinase Kinase 2; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; MCF-7 Cells; Mice; Mice, Inbred BALB C; Mice, Nude; Promoter Regions, Genetic; Pseudopodia; RNA, Messenger; Up-Regulation

The calpains are intracellular cysteine proteases that function in a variety of important cellular functions, including signalling, motility, apoptosis and survival. In breast cancer high calpain-1 and calpain-2 expression has been associated with adverse clinical outcome. Calpain-9 was thought to be exclusively expressed in the digestive tract; however recent studies have shown that this protein is also expressed in breast tissue.. We investigated the expression of calpain-9 in a large cohort of early stage breast cancer patients (n = 783) using immunohistochemistry on a tissue microarray. Patients had long-term follow-up information available for analysis.. Low expression of calpain-9 was associated with patients over 40 years of age (P = 0.025), smaller tumour size (P = 0.001), lower tumour stage (P = 0.009), a more favourable Nottingham Prognostic Index value (P = 0.002) and positive oestrogen receptor status (P = 0.014). Calpain-9 expression was not associated with survival in the total patient cohort, however low calpain-9 expression was associated with adverse survival in patients who received endocrine therapy (P = 0.033), which remained significant in multivariate Cox regression analysis accounting for potential confounding factors (hazard ratio (HR) = 0.56, 95% confidence interval (95% CI) = 0.36-0.89, P = 0.013). Low calpain-9 expression was also associated with adverse survival in patients with an intermediate Nottingham Prognostic Index value (P = 0.009), and remained so in multivariate analysis (HR = 0.54, 95% CI = 0.36-0.82, P = 0.003).. This study suggests that calpain-9 may play a role in breast cancer and that low expression is associated with poorer patient clinical outcome following endocrine therapy. Validation studies are warranted as determining expression of calpain-9 may provide important prognostic information.

Topics: Adult; Antineoplastic Agents, Hormonal; Biomarkers, Tumor; Breast Neoplasms; Calpain; Female; Humans; Immunohistochemistry; Middle Aged; Neoplasm Grading; Neoplasm Staging; Prognosis; Retrospective Studies; Treatment Outcome; Tumor Burden; Young Adult

Amiloride is a potassium-sparing diuretic that has been used as an anti-kaliuretic for the chronic management of hypertension and heart failure. Several studies have identified a potential anti-cancer role for amiloride, however the mechanisms underlying its anti-tumor effects remain to be fully delineated. Our group previously demonstrated that amiloride triggers caspase-independent cytotoxic cell death in human glioblastoma cell lines but not in primary astrocytes. To delineate the cellular mechanisms underlying amiloride's anti-cancer cytotoxicity, cell permeant and cell impermeant derivatives of amiloride were synthesized that exhibit markedly different potencies in cancer cell death assays. Here we compare the cytotoxicities of 5-benzylglycinyl amiloride (UCD38B) and its free acid 5-glycinyl amiloride (UCD74A) toward human breast cancer cells. UCD74A exhibits poor cell permeability and has very little cytotoxic activity, while UCD38B is cell permeant and induces the caspase-independent death of proliferating and non-proliferating breast cancer cells. UCD38B treatment of human breast cancer cells promotes autophagy reflected in LC3 conversion, and induces the dramatic swelling of the endoplasmic reticulum, however these events do not appear to be the cause of cell death. Surprisingly, UCD38B but not UCD74A induces efficient AIF translocation from the mitochondria to the nucleus, and AIF function is necessary for the efficient induction of cancer cell death. Our observations indicate that UCD38B induces programmed necrosis through AIF translocation, and suggest that its cytosolic accessibility may facilitate drug action.

Topics: Amiloride; Apoptosis; Apoptosis Inducing Factor; Breast Neoplasms; Calcium; Calpain; Caspases; Cell Cycle; Cell Death; Cell Line, Tumor; Cell Membrane Permeability; Cell Nucleus; Endoplasmic Reticulum; Female; Glycine; Humans; Protein Transport

Syk is a 72kDa non-receptor tyrosine kinase that is best characterized in hematopoietic cells. While Syk is pro-tumorigenic in some cancer cell types, it also has been reported as a negative regulator of metastatic cell growth in others. An examination of the RelA (p65) subunit of NF-κB expressed in MCF7 breast cancer cells indicated that either treatment with pervanadate or stable expression of Syk protected RelA from calpain-mediated proteolysis. Similar results were observed with the tyrosine phosphatase, PTP1B, another sensitive calpain substrate. The activity of calpain in MCF7 cell lysates was inhibited by both treatment with hydrogen peroxide and expression of Syk, the former due to oxidative inactivation of calpain and the latter to enhanced expression of calpastatin (CAST), the endogenous calpain inhibitor. The level of CAST was elevated in the cytosolic fraction of Syk-positive breast cancer cells resulting in more CAST present in complex with calpain in cell lysates. The high levels of CAST coincided with elevated basal levels of calcium-and of intracellular calpain activity-in Syk-expressing cells resulting from decreased levels of Bcl-2, an inhibitor of IP3-receptor-mediated calcium release. The inhibition of cellular calpain stimulated the Syk-mediated enhancement of NF-κB induced by TNF-α, enhanced tyrosine phosphorylation resulting from integrin crosslinking, and increased the localization of Syk to the plasma membrane.

Topics: Blotting, Western; Breast Neoplasms; Calcium; Calcium-Binding Proteins; Calpain; Cell Adhesion; Cell Movement; Cell Proliferation; Female; Fluorescent Antibody Technique; Humans; Hydrogen Peroxide; Immunoprecipitation; Intracellular Signaling Peptides and Proteins; NF-kappa B; Oxidants; Phosphorylation; Protein-Tyrosine Kinases; Proteolysis; Proto-Oncogene Proteins c-bcl-2; Subcellular Fractions; Syk Kinase; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

Breast tumor kinase (Brk), also known as protein kinase-6 (PTK6), is a nonreceptor protein-tyrosine kinase that has a close functional relationship with the human epidermal growth factor receptor 2 (HER2). High levels of Brk were found in HER2-positive tumor specimens from patients with invasive ductal breast cancer; however, the underlying mechanism of the co-overexpression of Brk and HER2 remains elusive. In the current study, we explored the mechanism of HER2 and Brk co-overexpression in breast cancer cells by investigating the effect of overexpression and knockdown of HER2 on the level of Brk in breast cancer cells. We found that Brk was more stable in HER2-elevated cells than in control vector-transfected cells and was less stable in HER2 siRNA-treated cells than in control siRNA-treated cells, suggesting that HER2 regulates Brk protein stability. Further studies indicated that degradation of Brk involved a calpain-1-mediated proteolytic pathway and indicated an inverse relationship between the level of HER2 expression and calpain-1 activity. We found that HER2 inhibited calpain-1 activity through upregulating calpastatin, an endogenous calpain inhibitor. Silencing of HER2 downregulated calpastatin, and the downregulation could be rescued by overexpression of constitutively active MEK. Together, these data offer novel mechanistic insights into the functional relationship between Brk and HER2.

Topics: Breast; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Enzyme Stability; Female; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Proteins; Protein-Tyrosine Kinases; Proteolysis; Receptor, ErbB-2; RNA Interference; RNA, Small Interfering; Up-Regulation

Overactivation of HER2 and crosstalk of other HER family members contribute to a survival pathway of breast cancer cells exposed to trastuzumab, the therapeutic inhibitor of HER2 and thus, decrease response and promote resistance. We have explored the involvement of the intracellular cysteine protease calpain4, the common partner of isoforms calpain1 and calpain2, in the regulation of cell survival and trastuzumab-response. Increase of calpain4 expression and isoform activities were detected in breast cancer cells and HER2-positive tumors. Molecular analyses of parent and resistant cells suggested that perturbation of regulations, induced by calpain4 and of activities of HER2 and HER3, was associated with trastuzumab-resistance. The suppression of calpain4 destabilized calpain1 and calpain2, however, did not prevent the activation of HER2 and HER3 or cell proliferation in the absence of trastuzumab. To understand the significance, the survival of parent and trastuzumab-resistant cells in which calpain4 was suppressed, was assessed in the presence of trastuzumab; survival in each cell type was decreased and associated with a loss of HER2 and HER3 activity. Taken together, by contributing to the activation and the crosstalk of HER2, calpain4 promotes the survival pathway of breast cancer cells, and therefore, its suppression enhances trastuzumab-response and decreases resistance.

Topics: Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Breast Neoplasms; Calpain; Cell Line, Tumor; Cell Proliferation; Cell Survival; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Humans; Protein Isoforms; Receptor, ErbB-2; Receptor, ErbB-3; Trastuzumab

In the current study, we investigated whether 17beta-estradiol (E2) induces cyclin E expression and triggers cyclin E processing via calpain in MCF-7 breast cancer cells. We found that E2 induced increased expression of cyclin E in a slow and persistent manner, and a rapid yet sustained processing of cyclin E. In addition, estrogenic ethanol was able to stimulate cyclin E truncation. Calpeptin or ALLN greatly suppressed the E2-triggered cyclin E processing and its expression, suggesting a calpain-mediated action for E2. Finally, the E2-induced effects could also be significantly suppressed by BAPTA or U0126, indicating involvement of calcium/ERK signaling. Taken together, these results show that estrogen may contribute to both up-regulation and proteolysis of cyclin E through calpain in MCF-7 cells.

Topics: Breast Neoplasms; Butadienes; Calcium; Calpain; Cell Line, Tumor; Chelating Agents; Cyclin E; Egtazic Acid; Estradiol; Extracellular Signal-Regulated MAP Kinases; Female; Humans; Nitriles; Signal Transduction; Up-Regulation

The purposes of this study were to investigate the role of Aplysia Ras Homolog I (ARHI) on cell growth, proliferation, apoptosis, and other biological characteristics of HER2-positive breast cancer cells. Our goal was to provide experimental evidence for the development of future effective treatments of HER2-positive breast cancer. A pcDNA3.1-ARHI eukaryotic expression vector was constructed and transfected into the human HER2-positive breast cancer cell lines SK-BR-3 and JIMT-1. Then, various experimental methods were utilized to analyze the biological characteristics of ARHI-expressing breast cancer cells and to examine the impact of expression of the ARHI gene on cyclin D1, p27(Kip1), and calpain1 expression. We further analyzed the cells in each group after treatment with trastuzumab to examine the effects of this drug on various cellular characteristics. When we compared pcDNA3.1-ARHI-expressing SK-BR-3 and JIMT-1 cells to their respective empty vector and control groups, we found that cell viability was significantly lower (p < 0.05) in the ARHI-expressing cells, and the proportions of G1 phase cells and apoptotic cells were significantly higher in the ARHI-expressing cells (p < 0.05). In all groups of SK-BR-3 cells, trastuzumab treatment significantly decreased cell growth (p < 0.05). The proportion of cells in G1 phase and the number of apoptotic cells in the pcDNA3.1-ARHI-expressing group were significantly higher than that in the empty vector group and the control group (p < 0.05). The growth of pcDNA3.1-ARHI-transfected JIMT-1 cells was significantly decreased (p < 0.05), while the proportion of apoptotic cells was significantly increased (p < 0.05). Cell growth, viability, and the percentage of apoptotic cells were similar between the JIMT-1 empty vector and control groups. ARHI expression inhibited cyclin D1 expression in SK-BR-3 cells and JIMT-1 cells, while it promoted p27(Kip1) and calpain1 expression in these cells. ARHI expression inhibits the growth and proliferation of HER2-positive breast cancer cells, while it also promotes apoptosis in these cells. ARHI expression also improves the sensitivity of JIMT-1 cells to trastuzumab by inducing apoptosis.

Topics: Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Calpain; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p27; Female; Gene Expression; Humans; PTEN Phosphohydrolase; rho GTP-Binding Proteins; Trastuzumab

The lymphovascular embolus is an enigmatic entity adept at metastatic dissemination and chemotherapy resistance. Using MARY-X, a human breast cancer xenograft that exhibits florid lymphovascular emboli in mice and spheroids in vitro, we established a model where the in vitro transition stages from minced tumoral aggregates to well-formed spheroids served as a surrogate for in vivo emboli formation. MARY-X well-formed spheroids and emboli exhibited strong similarity of expression. The aggregate-to-spheroid transition stages were characterized by increased ExoC5, decreased Hgs and Rab7, increased calpains, increased full-length E-cadherin (E-cad/FL), and the transient appearance of E-cad/NTF2, a 95 kDa E-cadherin fragment and increased Notch3icd (N3icd), the latter two fragments produced by increased γ-secretase. Both transient and permanent knockdowns of Rab7 in MCF-7 cells increased protein but not transcription of E-cad/FL and resulted in the de novo appearance of E-cad/NTF2, the presence of nuclear E-cad/CTF2, and increased Notch1icd (N1icd). Overexpression of Rab7 conversely decreased E-cad/FL, γ-secretase (PS1/NTF), and E-cad/NTF2. Overexpression of calpains did not alter PS1/NTF but decreased E-cad/FL and E-cad/NTF2 and increased N1icd. Well-formed spheroids showed increased Rab7, absent E-cad/NTF2, decreased PS1/NTF, increased E-cad/NTF1, and increased N3icd, the latter two fragments being the direct and indirect consequences, respectively, of increased calpains (calpain 1 and calpain 2). Inhibition of calpains decreased E-cad/NTF1 but increased E-cad/NTF2 showing that calpains compete with γ-secretase (PS1) for closely located cleavage/binding sites on E-cadherin and that increased calpains can shuttle even decreased levels of γ-secretase to Notch 3, resulting in increased Notch 3 signaling in the well-formed spheroids.

Topics: Amyloid Precursor Protein Secretases; Animals; Blotting, Western; Breast Neoplasms; Cadherins; Calpain; Cell Line; Cell Line, Tumor; Cell Transformation, Neoplastic; Endosomal Sorting Complexes Required for Transport; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Humans; Mice; Mice, SCID; Neoplastic Cells, Circulating; Oligonucleotide Array Sequence Analysis; Phosphoproteins; Proteolysis; rab GTP-Binding Proteins; rab7 GTP-Binding Proteins; Receptor, Notch3; Receptors, Notch; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Spheroids, Cellular; Transplantation, Heterologous

Basal-like and triple-negative breast tumours encompass an important clinical subgroup and biomarkers that can prognostically stratify these patients are required.. We investigated two breast cancer tissue microarrays for the expression of calpain-1, calpain-2 and calpastatin using immunohistochemistry. The first microarray was comprised of invasive tumours from 1371 unselected patients, and the verification microarray was comprised of invasive tumours from 387 oestrogen receptor (ER)-negative patients.. The calpain system contains a number of proteases and an endogenous inhibitor, calpastatin. Calpain activity is implicated in important cellular processes including cytoskeletal remodelling, apoptosis and survival. Our results show that the expression of calpastatin and calpain-1 are significantly associated with various clinicopathological criteria including tumour grade and ER expression. High expression of calpain-2 in basal-like or triple-negative disease was associated with adverse breast cancer-specific survival (P = 0.003 and <0.001, respectively) and was verified in an independent cohort of patients. Interestingly, those patients with basal-like or triple-negative disease with a low level of calpain-2 expression had similar breast cancer-specific survival to non-basal- or receptor- (oestrogen, progesterone or human epidermal growth factor receptor 2 (HER2)) positive disease.. Expression of the large catalytic subunit of m-calpain (calpain-2) is significantly associated with clinical outcome of patients with triple-negative and basal-like disease.

Topics: Adolescent; Adult; Aged; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Carcinoma, Ductal, Breast; Disease-Free Survival; Female; Humans; Kaplan-Meier Estimate; Middle Aged; Multivariate Analysis; Neoplasm Invasiveness; Neoplasms, Basal Cell; Proportional Hazards Models; Receptor, ErbB-2; Receptors, Estrogen; Receptors, Progesterone; Retrospective Studies; Young Adult

The calpain family, and their endogenous inhibitor calpastatin, has been implicated in cancer progression, and recent in vitro data have indicated a role in trastuzumab resistance. The aims of our study were to examine expression levels of calpastatin, calpain-1 and calpain-2 in breast tumours from patients treated with trastuzumab following adjuvant chemotherapy to determine their potential as biomarkers to predict therapeutic response. The expression of calpastatin, calpain-1 and calpain-2 was determined, using immunohistochemistry (IHC), in tumours from a series of 93 patients with primary breast cancer treated with surgery and adjuvant chemotherapy with or without trastuzumab followed by trastuzumab to complete 1 year of therapy. IHC was performed using tissue microarrays constructed from cores taken from intratumour and peripheral tumour areas. Expression was correlated with clinicopathologic variables and patient outcome. Calpastatin expression was correlated with Nottingham prognostic index (p = 0.003) and lymph node status (p = 0.007). Trastuzumab resistance was defined as disease relapse during therapy. Calpain-1 expression is associated with relapse-free survival (p = 0.001) and remained significant in multivariate analysis accounting for confounding pathological and treatment variables (hazard ratio 4.60, 95% confidence interval 1.05-20.25; p = 0.043). Calpain-1 may be a useful biomarker to predict relapse-free survival in breast cancer patients treated with adjuvant trastuzumab and chemotherapy. A larger verification study is warranted.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Biomarkers, Tumor; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Chemotherapy, Adjuvant; Disease-Free Survival; Female; Humans; Middle Aged; Prognosis; Trastuzumab

Metastasis of breast cancer is a major contributor to mortality. Histological assessment of vascular invasion (VI) provides important prognostic information and demonstrates that VI occurs predominantly via lymphatics in breast cancer. We sought to examine genes and proteins involved in lymphovascular invasion (LVI) to understand the mechanisms of this key disease process. A gene expression array of 91 breast cancer patients was analysed by an Artificial Neural Network (ANN) approach using LVI to supervise the analysis. 89 transcripts were significantly associated (p<0.001) with the presence of LVI. Calpastatin, a specific calpain inhibitor, had the second lowest selection error and was investigated in breast cancer specimens using real-time PCR (n=56) and immunohistochemistry (n=53). Both calpastatin mRNA and protein levels were significantly associated with the presence of LVI (p=0.014 and p=0.025 respectively). The data supports the hypothesis that calpastatin may play a role in regulating the initial metastatic dissemination of breast cancer.

Topics: Adult; Breast Neoplasms; Calcium-Binding Proteins; Calpain; Female; Humans; Immunohistochemistry; Lymphatic Metastasis; Lymphatic Vessels; Middle Aged; Neoplasm Invasiveness; Predictive Value of Tests; Real-Time Polymerase Chain Reaction

Type V collagen is known to be over-deposited in the stroma of ductal infiltrating carcinomas of the breast. When used as a substrate, type V collagen restrains growth and invasion, and affects gene expression of 8701-BC ductal infiltrating carcinomas cells. Here we supplement existing data by demonstrating type V collagen dependent upregulation of capn2 gene expression in 8701-BC cells through differential display-PCR and Western blot assays. Furthermore, we suggest that our data obtained by centrifugal sedimentation and electrophoresis strongly suggest a correlation between calpain overproduction and DNA fragmentation, since the incubation with calpain inhibitor partly reverts the latter.

Topics: Breast Neoplasms; Calpain; Cell Line, Tumor; Collagen Type V; DNA Fragmentation; DNA, Neoplasm; Female; Gene Expression Profiling; Gene Expression Regulation, Enzymologic; Humans; Polymerase Chain Reaction; Up-Regulation

CEACAM1-4S (carcinoembryonic antigen-related cell adhesion molecule 1) is a type I membrane protein with a short (12-amino acid) cytoplasmic tail. Wild type CEACAM1-4S-transfected MCF7 cells form glands with lumena when grown in 3D culture, while null mutations of two putative phosphorylation sites (T457A and S459A) in the cytoplasmic domain fail to undergo lumen formation. When gene chip analysis was performed on mRNA isolated from both wild type and T457A,S459A mutated CEACAM1-4S-transfected MCF7 cells grown in 3D culture, calpain-9 (CAPN9) was identified out of over 400 genes with a >2 log 2 difference as a potential inducer of lumen formation. Inhibition of CAPN9 expression in MCF7/CEACAM1-4S cells by RNAi or by calpeptin or PD150606 inhibited lumen formation. Transfection of CAPN9 into wild type MCF7 cells restores lumen formation demonstrating that calpain-9 may play a critical role in lumen formation. Additionally, we demonstrate that the apoptosis related kinase, PKC-delta, is activated by proteolytic cleavage during lumen formation exclusively in wild type CEACAM1-4S-transfected MCF7 cells grown in 3D culture and that lumen formation is inhibited by either RNAi to PKC-delta or by the PKC-delta inhibitor rottlerin.

Topics: Acrylates; Antigens, CD; Apoptosis; Blotting, Western; Breast Neoplasms; Calpain; Cell Adhesion Molecules; Cell Line, Transformed; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Dipeptides; Epithelial Cells; Female; Gene Deletion; Gene Expression Regulation; Humans; Models, Biological; Mutation; Oligonucleotide Array Sequence Analysis; Protein Kinase C-delta; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transfection

Resistance to anti-HER2 (human epithelial growth factor receptor 2) trastuzumab therapy occurs commonly in HER2-positive breast cancer and involves overactivation of HER2 and/or AKT1. Using the model of trastuzumab-sensitive or trastuzumab-resistant HER2-positive cells with wild-type PTEN, negative regulator of AKT1, we explore the involvement of cysteine protease calpain in mechanisms of trastuzumab resistance. Overexpression of calpain1 or activation of endogenous calpain during adhesion or trastuzumab treatment of trastuzumab-sensitive cells induces cleavage of cytoplasmic domains of HER2/phospho-HER2; cleavage occurs in HER2-positive tumors. Expression of the catalytically inactive mutant of calpain1 reduces the cleavage to enhance the activity of HER2, inactivates PTEN to enhance the activation of AKT1, induces desensitization to trastuzumab and promotes survival of trastuzumab-sensitive cells. In the model of trastuzumab resistance, constitutive overactivation of HER2 and AKT1 correlates with reduced activation of calpain. Moreover, inhibitors of the catalytic site of calpain reduce the increase in constitutive activity of AKT1 and survival of trastuzumab-resistant cells selectively. Together, by regulating the activation of HER2 and PTEN/AKT1, calpain regulates trastuzumab sensitivity and survival, and the deregulation of the activation of calpain promotes trastuzumab resistance. Trastuzumab-resistant cells activate AKT1 in a mechanism dependent on the residual calpain activity, inhibition of which restores trastuzumab sensitivity and rescues resistance. These data identify calpain as a new therapeutic target in HER2-positive breast cancer.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Breast Neoplasms; Calpain; Drug Resistance, Neoplasm; Female; Humans; Protein Kinase Inhibitors; Sensitivity and Specificity; Trastuzumab

A new water-soluble phthalocyanine derivative, 2,3,9,10,16,17,23,24-octakis(3-aminopropyloxy) phthalocyaninato zinc II (PoII) was studied as a photosensitizer for photodynamic therapy (PDT) in MCF-7c3 cells. We report here that PoII and red light induces apoptosis. However, the precise mechanism appears to differ from that induced by PDT with other known phthalocyanines. The present study provides evidence that in the case of PoII, caspases do not participate in the apoptotic response. PoII-PDT-treated cells exhibited chromatin condensation and phosphatidylserine (PS) externalization. In the absence of light activation, PoII had no detectable cytotoxic effect. An early event upon PoII-PDT was photodamage to lysosomes, suggesting that they are the primary sites of action. Moreover, the treatment induces Bid activation, mitochondrial swelling and translocation of apoptosis-inducing factor (AIF) to the nucleus. An atypical proteolysis of poly(ADP-ribose) polymerase (PARP) indicative of calpain-like activation was observed. These data support the notion that an alternative mechanism of caspase-independent apoptosis was found in PoII-photosensitized cells.

Topics: Apoptosis; Apoptosis Inducing Factor; BH3 Interacting Domain Death Agonist Protein; Breast Neoplasms; Calpain; Caspases; Cell Line, Tumor; Chromatin; DNA Fragmentation; DNA, Neoplasm; Enzyme Activation; Female; G1 Phase; Humans; Indoles; Lysosomes; Mitochondrial Swelling; Organometallic Compounds; Phosphatidylserines; Photochemotherapy; Photosensitizing Agents; Protein Transport; Solubility; Water

The actin cross-linking protein filamin A (FLNa) functions as a scaffolding protein and couples cell cytoskeleton to extracellular matrix and integrin receptor signaling. In this study, we report that FLNa suppresses invasion of breast cancer cells and regulates focal adhesion (FA) turnover. Two large progression tissue microarrays from breast cancer patients revealed a significant decrease of FLNa levels in tissues from invasive breast cancer compared with benign disease and in lymph node-positive compared with lymph node-negative breast cancer. In breast cancer cells and orthotopic mouse breast cancer models, down-regulation of FLNa stimulated cancer cell migration, invasion, and metastasis formation. Time-lapse microscopy and biochemical assays after FLNa silencing and rescue with wild-type or mutant protein resistant to calpain cleavage revealed that FLNa regulates FA disassembly at the leading edge of motile cells. Moreover, FLNa down-regulation enhanced calpain activity through the mitogen-activated protein kinase-extracellular signal-regulated kinase cascade and stimulated the cleavage of FA proteins. These results document a regulation of FA dynamics by FLNa in breast cancer cells.

Topics: Animals; Breast Neoplasms; Calpain; Cell Line, Tumor; Cell Movement; Contractile Proteins; Cytoskeleton; Disease Models, Animal; Female; Filamins; Focal Adhesions; Gene Expression Regulation, Neoplastic; Gene Silencing; Humans; MAP Kinase Signaling System; Mice; Mice, SCID; Microfilament Proteins; Mitogen-Activated Protein Kinase Kinases; Mutation; Neoplasm Invasiveness; Neoplasm Transplantation

Invasive cancer cells form dynamic adhesive structures associated with matrix degradation called invadopodia. Calpain 2 is a calcium-dependent intracellular protease that regulates adhesion turnover and disassembly through the targeting of specific substrates such as talin. Here, we describe a novel function for calpain 2 in the formation of invadopodia and in the invasive abilities of breast cancer cells through the modulation of endogenous c-Src activity. Calpain-deficient breast cancer cells show impaired invadopodia formation that is rescued by expression of a truncated fragment of protein tyrosine phosphatase 1B (PTP1B) corresponding to the calpain proteolytic fragment, which indicates that calpain modulates invadopodia through PTP1B. Moreover, PTP1B activity is required for efficient invadopodia formation and breast cancer invasion, which suggests that PTP1B may modulate breast cancer progression through its effects on invadopodia. Collectively, our experiments implicate a novel signaling pathway involving calpain 2, PTP1B, and Src in the regulation of invadopodia and breast cancer invasion.

Topics: Breast Neoplasms; Calpain; Carcinoma; Cell Adhesion; Cell Line; Cell Line, Tumor; Cell Movement; CSK Tyrosine-Protein Kinase; Down-Regulation; Extracellular Matrix; Female; Humans; Mutation; Neoplasm Invasiveness; Protein Tyrosine Phosphatase, Non-Receptor Type 1; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Pseudopodia; Signal Transduction; src-Family Kinases

The molecular mechanisms of genistein-induced apoptosis of human breast cancer MCF-7 cells were investigated. Genistein showed 50% cell growth inhibition at IC50=27.5+/-0.8 micromol/l in 24 h incubation under 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay conditions. Genistein is known to express both cell growth activity at nanomolar concentrations and anti-cell growth activity at micromolar concentrations. It was found that genistein at 100 micromol/l concentration effectively induced apoptosis of MCF-7 cells in 24 h. Genistein-induced apoptosis involved activation of calpain, caspase 7 and poly(ADP ribose) polymerase. Dantrolene, an inhibitor of Ca release from the endoplasmic reticulum, inhibited genistein-induced activation of calpain and caspase 7, in addition to effectively negating genistein-induced apoptosis. MCF-7 cells treated with genistein also showed increased phosphorylation of p38 mitogen-activated protein kinase, whereas no effect was observed for extracellular signal-regulating kinase 1/2. Phosphorylation of apoptosis signaling kinase 1, an upstream regulator of p38 mitogen-activated protein kinase, was also increased by genistein treatment. Genistein-induced phosphorylation of apoptosis signaling kinase 1 and p38 mitogen-activated protein kinase was diminished by the presence of dantrolene. These results suggest that genistein-induced apoptosis in MCF-7 cells is mediated through calpain-caspase 7 and apoptosis signaling kinase 1-p38 mitogen-activated protein kinase activation cascades that involve Ca release from the endoplasmic reticulum.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Breast Neoplasms; Calcium; Calpain; Caspase 7; Cell Line, Tumor; Cell Proliferation; Cell Survival; Endoplasmic Reticulum; Female; Genistein; Humans; MAP Kinase Kinase Kinase 5; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Signal Transduction

Resveratrol (RES), a natural plant polyphenol, has gained interest as a nontoxic chemopreventive agent capable of inducing tumor cell death in a variety of cancer types. However, the early molecular mechanisms of RES-induced apoptosis are not well defined. Using the human breast cancer cell lines MDA-MB-231 and MCF-7, we demonstrate that RES is antiproliferative and induces apoptosis in a concentration- and time-dependent manner. Preceding apoptosis, RES instigates a rapid dissipation of mitochondrial membrane potential by directly targeting mitochondria. This is followed by release of cytochrome c and second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI (Smac/DIABLO) into the cytoplasm and substantial increase in the activities of caspases-9 and -3 in MDA-MB-231 cells. In addition, live cell microscopy demonstrates that RES causes an early biphasic increase in the concentration of free intracellular calcium ([Ca2+]i), probably resulting from depletion of the endoplasmic reticulum stores in breast cancer cells. In caspase-3-deficient MCF-7 cells, apoptosis is mediated by the Ca2+-activated protease, calpain, leading to the degradation of plasma membrane Ca2+-ATPase isoform 1 and fodrin; the degradation is attenuated by buffering [Ca2+]i and blocked by calpain inhibitors. Mitochondrial permeability transition pore antagonists also blocked calpain activation. In vivo mouse xenograft studies demonstrate that RES treatment inhibits breast cancer growth with no systemic toxicities. Together, these results suggest a critical role for mitochondria not only in the intrinsic apoptotic pathway but also in the Ca2+ and calpain-dependent cell death initiated by RES. Thus, RES may prove useful as a nontoxic alternative for breast cancer treatment.

Topics: Animals; Apoptosis; Breast Neoplasms; Calcium; Calpain; Cell Line, Tumor; Female; Humans; Mice; Mice, Nude; Mitochondria; Resveratrol; Stilbenes; Xenograft Model Antitumor Assays

ARHI is a maternally imprinted tumor suppressor gene that is downregulated in 60% of ovarian and breast cancers. Loss of ARHI expression is associated with tumor progression in breast cancer and decreased disease-free survival in ovarian cancer. ARHI encodes a 26-kDa protein with 55-62% homology to Ras and Rap. In contrast to Ras, ARHI inhibits growth, motility, and invasion. ARHI contains a unique 34 amino-acid extension at its N-terminus and differs from Ras in residues critical for GTPase activity and for its putative effector function. Deletion of ARHI's unique N-terminal extension markedly reduces its inhibitory effect on cell growth. The gene maps to chromosome 1p31 at a site of LOH in 40% of ovarian and breast cancers. Mutations have not been detected, but the remaining allele is silenced by methylation in approximately 10-15 % of cases. In the remaining cancers, ARHI is downregulated by transcriptional mechanisms that involve E2F1 and E2F4, as well as by the loss of RNA binding proteins that decrease the half-life of ARHI mRNA. Transgenic expression of human ARHI in mice produces small stature, induces ovarian atrophy, and prevents postpartum milk production. Reexpression of ARHI in cancer cells inhibits signaling through Ras/Map and PI3 kinase, upregulates P21(WAF1/CIP1), downregulates cyclin D1, induces JNK, and inhibits signaling through STAT3. Marked overexpression of ARHI with a dual adenoviral vector induces caspase-independent, calpain-dependent apoptosis. When ARHI is expressed from a doxycycline-inducible promoter at more physiological levels, autophagy is induced, rather than apoptosis. Growth of ovarian and breast cancer xenografts is reversibly suppressed by ARHI, but expression of the NTD mutant produced only a limited inhibitory effect on growth of xenografts.

Topics: Animals; Apoptosis; Breast Neoplasms; Calpain; Down-Regulation; Female; Genes, Tumor Suppressor; Genomic Imprinting; Humans; Mice; Mice, Transgenic; Ovarian Neoplasms; rho GTP-Binding Proteins; Signal Transduction

The signaling cascades activated by insulin and IGF-1 contribute to the control of multiple cellular functions, including glucose metabolism and cell proliferation. In most cases these effects are mediated, at least in part, by insulin receptor substrates (IRS), one of which is insulin receptor substrate 1 (IRS-1). R-Ras is a member of the Ras family of GTPases and is involved in a variety of biological processes, including integrin activation, cell migration, and control of cell proliferation. Here we demonstrate that both R-Ras and BCAR3, a regulator of R-Ras activity that has been implicated in breast cancer, regulate the level of IRS-1 protein in estrogen-dependent MCF-7 and ZR75 breast cancer cells. In particular, expression of a constitutively activated R-Ras mutant, R-Ras38V, or of BCAR3 accelerates the degradation of IRS-1, leading to the impairment of signaling through insulin but not epidermal growth factor receptors. Moreover, knockdown of endogenous R-Ras levels in MCF-7 cells inhibits IRS-1 degradation induced by estrogen signaling blockade but not by long-term insulin treatment. Consistent with these results, both R-Ras38V expression and estrogen signaling blockade lead to the degradation of IRS-1, at least in part, through calpain activity. These findings show that R-Ras activity mediates inhibition of insulin signaling associated with suppression of estrogen action, implicating this GTPase in a growth-inhibitory mechanism associated with antiestrogen treatment of breast cancer.

Topics: 3T3-L1 Cells; Adaptor Proteins, Signal Transducing; Animals; Breast Neoplasms; Calpain; Down-Regulation; Enzyme Activation; Epidermal Growth Factor; Estrogens; Extracellular Signal-Regulated MAP Kinases; Female; Guanine Nucleotide Exchange Factors; Humans; Insulin; Insulin Receptor Substrate Proteins; Mice; Phosphoproteins; Protein Processing, Post-Translational; ras Guanine Nucleotide Exchange Factors; ras Proteins; RNA Interference; Signal Transduction; Tumor Cells, Cultured

Flavonoids, polyphenolic phytochemicals which include flavones and isoflavones, are present in the common human diet. It has been suggested that these compounds may exert anticancer activity; however, the mechanisms involved remain unknown. We have recently shown (Sergeev, 2004, Biochem Biophys Res Commun 321: 462-467) that isoflavones can activate the novel apoptotic pathway mediated by cellular Ca(2+). Here, we report that polymethoxyflavones (PMFs) derived from sweet orange (Citrus sinensis L.) inhibit growth of human breast cancer cells via Ca(2+)-dependent apoptotic mechanism. The treatment of MCF-7 breast cancer cells with 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone (5-OH-HxMF) and 3'-hydroxy-5,6,7,4'-tetramethoxyflavone (3'-OH-TtMF) induced a sustained increase in concentration of intracellular Ca(2+) ([Ca(2+)](i)) resulting from both depletion of the endoplasmic reticulum Ca(2+) stores and Ca(2+) influx from the extracellular space. This increase in [Ca(2+)](i) was associated with the activation of the Ca(2+)-dependent apoptotic proteases, mu-calpain and caspase-12, as evaluated with the calpain and caspase-12 peptide substrates and antibodies to active (cleaved) forms of the enzymes. Corresponding non-hydroxylated PMFs, 3,5,6,7,8,3',4'-heptamethoxyflavone (HpMF) and 5,6,7,3',4'-pentamethoxyflavone (PtMF), were dramatically less active in inducing Ca(2+)-mediated apoptosis. Our results strongly suggest that the cellular Ca(2+) modulating activity of flavonoids underlies their apoptotic mechanism and that hydroxylation of PMFs is critical for their ability to induce an increase in [Ca(2+)](i) and, thus, activate Ca(2+)-dependent apoptotic proteases.

Topics: Apoptosis; Breast Neoplasms; Calcium; Calcium Signaling; Calpain; Caspase 12; Cell Line, Tumor; Citrus sinensis; Endoplasmic Reticulum; Enzyme Activation; Female; Humans; Isoflavones

Activation of Src kinase plays important roles in the development of many neoplasias. Most of the previous Src studies focused on the deregulation of Src kinase activity. The deregulated Src protein synthesis and stability in mediating malignant phenotypes of cancer cells, however, have been neglected. While investigating the signal transduction pathways contributing to ErbB2-mediated metastasis, we found that ErbB2-activated breast cancer cells that had higher metastatic potentials also had increased Src activity compared with ErbB2 low-expressing cells. The increased Src activity in ErbB2-activated cells paralleled higher Src protein levels, whereas Src RNA levels were not significantly altered. Our studies revealed two novel mechanisms that are involved in Src protein up-regulation and activation by ErbB2: (a) ErbB2 increased Src translation through activation of the Akt/mammalian target of rapamycin/4E-BP1 pathway and (b) ErbB2 increased Src stability most likely through the inhibition of the calpain protease. Furthermore, inhibition of Src activity by a Src-specific inhibitor, PP2, or a Src dominant-negative mutant dramatically reduced ErbB2-mediated cancer cell invasion in vitro and metastasis in an experimental metastasis animal model. Together, activation of ErbB2 and downstream signaling pathways can lead to increased Src protein synthesis and decreased Src protein degradation resulting in Src up-regulation and activation, which play critical roles in ErbB2-mediated breast cancer invasion and metastasis.

Topics: Adaptor Proteins, Signal Transducing; Animals; Breast Neoplasms; Calpain; Carrier Proteins; Cell Cycle Proteins; Enzyme Activation; Enzyme Stability; Eukaryotic Initiation Factors; Female; Genes, Dominant; Humans; Lung Neoplasms; Mice; Mice, Inbred ICR; Mice, SCID; Neoplasm Invasiveness; Phosphoprotein Phosphatases; Phosphoproteins; Phosphorylation; Protein Biosynthesis; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins pp60(c-src); Receptor, ErbB-2; Signal Transduction; TOR Serine-Threonine Kinases; Tumor Cells, Cultured

Overexpression of cyclin E in breast tumors is associated with a poor response to tamoxifen therapy, greater genomic instability, more aggressive behavior, and a poor clinical prognosis. These tumors also express low molecular weight isoforms of cyclin E that are associated with higher kinase activity and increased metastatic potential. In the current study, we show that cyclin E overexpression in MCF7 cells transactivates the expression of calpain 2, leading to proteolysis of cyclin E as well as several known calpain substrates including focal adhesion kinase (FAK), calpastatin, pp60src, and p53. In vivo inhibition of calpain activity in MCF7-cyclin E cells impedes cyclin E proteolysis, whereas in vivo induction of calpain activity promotes cyclin E proteolysis. An analysis of human breast tumors shows that high levels of cyclin E are coincident with the expression of the low molecular weight isoforms, high levels of calpain 2 protein, and proteolysis of FAK. Lastly, studies using a mouse model of metastasis reveal that highly metastatic tumors express proteolyzed cyclin E and FAK when compared to tumors with a low metastatic potential. Our results suggest that cyclin E-dependent deregulation of calpain may be pivotal in modifying multiple cellular processes that are instrumental in the etiology and progression of breast cancer.

Topics: Animals; Breast Neoplasms; Calpain; Cell Line, Tumor; Cyclin E; Focal Adhesion Protein-Tyrosine Kinases; Gene Expression Regulation, Neoplastic; HCT116 Cells; Humans; Isoenzymes; Mice; Neoplasm Metastasis; Transcriptional Activation; Transfection

Arachidonic acid (AA) stimulation of adhesion of human metastatic breast carcinoma cells to collagen type IV depends on the protein kinase C (PKC) pathway(s) and is associated with the translocation of PKC mu from the cytoplasm to the membrane. In the present study, we have further explored the role of PKC mu in AA-stimulated adhesion. PKC mu activation site serines 738/742 and autophosphorylation site serine 910 are rapidly phosphorylated, and in vitro PKC mu kinase activity is enhanced in response to AA treatment. Inhibition of PKC mu activation blocks AA-stimulated adhesion. A phosphorylated, truncated species of PKC mu was detected in AA-treated cells. This 77-kDa protein contains the kinase domain but lacks a significant portion of the regulatory domains. Inhibition of calpain protease activity blocks generation of the truncated protein, promotes accumulation of the activated, full-length protein in the membrane, and blocks the AA-mediated increase in adhesion. p38 MAPK activity is also required for AA-stimulated adhesion. Activation of PKC mu and p38 are independent events. However, inhibition of p38 activity reduces calpain-mediated proteolysis of PKC mu and in vivo calpain activity, suggesting a role for p38 in regulation of calpain activity and a point for cross-talk between the PKC and MAPK pathways. These results support the hypothesis that AA stimulates activation of PKC mu, which is cleaved by calpain at the cell membrane. The resulting truncated kinase, as well as the full-length kinase, may be required for increased cell adhesion to collagen type IV. Additionally, these studies present the first evidence for calpain cleavage of a non-structural protein leading to the promotion of tumor cell adhesion.

Topics: Arachidonic Acid; Blotting, Western; Breast Neoplasms; Calpain; Cell Adhesion; Cell Line, Tumor; Cell Membrane; Collagen Type IV; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Inhibitors; Humans; Mitogen-Activated Protein Kinases; Models, Biological; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein Binding; Protein Kinase C; Signal Transduction; Subcellular Fractions; Time Factors

Genistein, a soy-derived isoflavone, has been suggested for breast cancer prevention; however, use of soy products for this purpose remains controversial. Genistein has been reported to regulate growth of tumor cells, although the involved molecular mechanisms are not defined. Here we report that genistein induces apoptosis in breast cancer cells via activation of the Ca2+ -dependent proapoptotic proteases, mu-calpain, and caspase-12. The treatment of MCF-7 breast cancer cells with genistein induced a sustained increase in concentration of intracellular Ca2+ resulting from depletion of the endoplasmic reticulum Ca2+ stores. This increase in Ca2+ was associated with activation of mu-calpain and caspase-12, as evaluated with the calpain and caspase-12 substrates and antibodies to active (cleaved) forms of the enzymes. Selective inhibition of Ca2+ binding sites of mu-calpain, forced increase of the cytosolic Ca2+ buffering capacity, and caspase inhibition decreased apoptotic indices in the genistein-treated cells. Our results suggest that Ca2+ -dependent proteases are potential targets for genistein in breast cancer cells and that the cellular Ca2+ regulatory activity of genistein underlies its apoptotic mechanism.

Topics: Apoptosis; Breast Neoplasms; Calcium; Calpain; Caspase 12; Caspases; Cell Line, Tumor; Genistein; Humans

Mutations in the NH(2)-terminal regulatory domain of the beta-catenin gene lead to aberrant stabilization and accumulation of the protein and increased TCF/LEF-dependent transcription. Although these mutations are common in some cancers, they are infrequent in prostate and breast cancer. We have found that metastatic prostate cancer specimens, obtained through a rapid autopsy tissue procurement program, expressed a novel M(r) 75,000 proteolytic fragment of beta-catenin (beta-cat(75)). beta-Cat(75) was also expressed in multiple prostate and breast cancer cell lines and was closely associated with the activity of the calcium-dependent protease, calpain. In a prostate cancer cDNA microarray, m-calpain RNA levels were found to be significantly increased in metastatic disease compared with normal prostate. We showed calpain-dependent generation of beta-cat(75) in cell culture and in vitro. Molecular mapping revealed that calpain cleavage removed the NH(2)-terminal regulatory domain of the beta-catenin protein. Treatment of MCF-7 cells with ionomycin led to increased accumulation of beta-cat(75) in the nucleus and TCF-dependent transcriptional activity. Overexpression of a similar beta-catenin fragment that lacks the NH(2)-terminal 132 amino acids and has transforming potential activated TCF-dependent transcription. Given the low frequency of mutation-induced activation of beta-catenin in prostate and breast cancers, proteolytic cleavage of beta-catenin by calpain may represent a novel mechanism by which the protein is activated during tumorigenesis.

Topics: beta Catenin; Breast Neoplasms; Calcium; Calpain; Cell Line, Tumor; Cell Nucleus; Cytoskeletal Proteins; DNA-Binding Proteins; Epithelial Cells; Female; Humans; Ionomycin; Male; Mutation; Prostatic Neoplasms; TCF Transcription Factors; Trans-Activators; Transcription Factor 7-Like 2 Protein; Transcription Factors; Transfection

Smac/DIABLO, a pro-apoptotic protein released from mitochondrial intermembrane space during apoptosis, promotes caspase activation by IAPs neutralization. The kinetics and molecular mechanism of Smac/DIABLO release from mitochondria has remained obscure. Homeostatic confocal microscopy, for the first time, showed the precise kinetics of Smac/DIABLO release from mitochondria during CPT-induced apoptosis in living MCF-7 cells. The time pattern of Smac/DIABLO escape from mitochondria comprised two phases: the initial phase of gradual protein release, followed by the second phase of plateau, appearing after 24 min of cell exposure to the drug. A similar pattern was observed during oxidative stress. The dynamics of Smac/DIABLO redistribution was confirmed by different methods: traditional confocal microscopy, immunoelectron microscopy and laser scanning cytometry. The inhibition of m-calpain prevented Smac/DIABLO release from mitochondria, which confirmed the involvement of Bax in the process. Acquired results indicate that CPT treatment triggers Bax-dependent release of Smac/DIABLO from mitochondria simultaneously with the efflux of cytochrome c.

Topics: Apoptosis; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; Breast Neoplasms; Calpain; Camptothecin; Carrier Proteins; Cytochromes c; Female; Green Fluorescent Proteins; Humans; Intracellular Signaling Peptides and Proteins; Kinetics; Laser Scanning Cytometry; Microscopy, Confocal; Microscopy, Immunoelectron; Mitochondria; Mitochondrial Proteins; Oxidative Stress; Proto-Oncogene Proteins c-bcl-2; Time Factors; Tumor Cells, Cultured

Abundant levels of the hyperactive low molecular weight (LMW) forms of cyclin E contribute to deregulation of Cdk2 in breast tumors, but the mechanism through which they arise is not fully understood. Here, we explored the hypothesis that post-translational processing by a protease generates the LMW forms of cyclin E in breast tumors. In ZR75 tumor cell lysates, calcium-induced cyclin E truncation into peptides corresponding in size with LMW forms of cyclin E in tumor tissues. Calpeptin inhibited calcium-stimulated cyclin E truncation, indicating that cleavage resulted from activity of the calcium-dependent protease, calpain. Consistently, calcium+calpain caused truncation of cyclin E immunoprecipitated from tumor cells and tissues. Calcium also caused truncation of the calpain regulatory subunit in tumor cell lysates, indicating that elevated calpain activity accompanies cyclin E truncation. Increased levels of the calpain small subunit were also observed in breast tumors, and significant amounts of its proteolyzed forms indicated increased calpain activity. While elastase also caused cyclin E truncation, the cleavage pattern was distinct from that generated by calpain, suggesting discrete mechanisms in regulating the formation of LMW cyclin E in breast tumors. Treatment of ZR75 cultures with calcium+A23187 recapitulated the formation of the calcium/calpain-induced LMW forms of cyclin E. Altered calcium homeostasis and/or inability of the endogenous calpain inhibitor to control the activity of high levels of the calpain small subunit may contribute to increased calpain activity in breast tumors, causing abundant levels of LMW cyclin E.

Topics: Breast Neoplasms; Calcium; Calpain; Cyclin E; Female; Humans; Precipitin Tests; Protein Processing, Post-Translational; Tumor Cells, Cultured

Various stimuli including anticancer drugs are capable of initiating the apoptotic death program in human tumor cells via activation of caspases. Mitochondria play an essential role for cell apoptotic commitment. Previous studies have shown a potential role of calpain activation in apoptosis, however, the involved molecular mechanisms remain to be defined. In the current study, we have examined the expression and activation of mitochondrial calpain in Jurkat T leukemia cells, MCF-7 breast carcinoma and LNCaP prostate cancer cells during apoptosis induced by an anticancer drug (VP-16, tamoxifen) or the specific p38 kinase inhibitor PD-169316. Our results suggest that increased expression and autolysis of the mitochondrial calpain small subunit are tightly associated with calpain activation in an early stage of apoptosis. In contrast, there were no correlations observed between the early calpain activation and changes in levels of mitochondrial calpain large subunit and the endogenous calpain inhibitor calpastatin. Furthermore, pretreatment with the specific pharmacological calpain inhibitor calpeptin blocked the drug-induced calpain small subunit autolysis and calpain activation in mitochondria and inhibited apoptosis-associated caspase-3 activation, demonstrating that mitochondrial calpain activation through small subunit cleavage is an essential step for inducing tumor cell apoptosis by various anticancer drugs.

Topics: Antineoplastic Agents; Apoptosis; Autolysis; Breast Neoplasms; Calpain; Cytochrome c Group; Enzyme Activation; Enzyme Inhibitors; Etoposide; Female; Humans; Imidazoles; Jurkat Cells; Male; Mitochondria; Mitogen-Activated Protein Kinases; p38 Mitogen-Activated Protein Kinases; Prostatic Neoplasms; Protein Subunits; Tamoxifen; Tumor Cells, Cultured

ARHI, an imprinted putative tumor suppressor gene, encodes a M(r) 26,000 GTP-binding protein that is 60% homologous to ras and rap but has a dramatically different function. ARHI expression is down-regulated in a majority of breast and ovarian cancers. Using a dual adenovirus system, we have reexpressed ARHI in ovarian cancer and breast cancer cells that have lost ARHI expression. Reexpression of ARHI inhibited growth, decreased invasiveness, and induced apoptosis. At 5 days after infection with ARHI adenovirus, 30-45% of MDA-MB-231 breast cancer cells and 5-11% of SKOv3 ovarian cancer cells were apoptotic as judged by a terminal deoxynucleotidyl transferase-mediated nick end labeling assay and by Annexin V staining with flow cytometric analysis. Although poly(ADP-ribose) polymerase could be detected immunohistochemically in the nuclei of apoptotic cells, no activation of the effector caspases (caspase 3, 6, 7, or 12) or the initiator caspases (caspase 8 or 9) could be detected in cell lysates using Western blotting. When gene expression was analyzed on a custom cDNA array that contained 2304 known genes, infection with ARHI adenovirus up-regulated 15 genes relative to control cells infected with LacZ adenovirus. The greatest degree of mRNA up-regulation was observed in a Homo sapiens calpain-like protease. On Western blot analysis, calpain protein was increased 2-3-fold at 3-5 days after infection with ARHI adenovirus. No increase in calpain protein was observed after LacZ adenovirus infection. Calpain cleavage could be detected after ARHI reexpression, and inhibitors of calpain, but not inhibitors of caspase, partially prevented ARHI-induced apoptosis. Consequently, reexpression of ARHI in breast and ovarian cancer cells appears to induce apoptosis through a caspase-independent, calpain-dependent mechanism.

Topics: Adenoviridae; Animals; Apoptosis; Breast Neoplasms; Calpain; Caspase Inhibitors; Caspases; Cell Cycle; Cell Division; Female; Genes, Tumor Suppressor; Genetic Therapy; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Ovarian Neoplasms; rho GTP-Binding Proteins; Signal Transduction; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

The active form of vitamin D(3) (1,25(OH)(2)D(3)) induces an increase in the intracellular free calcium ([Ca(2+)](i)) and caspase-independent cell death in human breast cancer cells. Here we show that the treatment of MCF-7 breast cancer cells with 1,25(OH)(2)D(3) or its chemotherapeutic analog, EB 1089, releases Ca(2+) from the endoplasmic reticulum. The increase in [Ca(2+)](i) was associated with the activation of a calcium-dependent cysteine protease, mu-calpain. Interestingly, ectopic expression of a calcium-binding protein, calbindin-D(28k), in MCF-7 cells not only attenuated the elevation in [Ca(2+)](i) and calpain activation, but also reduced death triggered by vitamin D compounds. Similarly, the inhibition of calpain activity by structurally unrelated chemical inhibitors increased the survival of the cells and reduces the amount of annexin V-positive cells. Despite the complete absence of effector caspase activation, transmission electron microscopy of MCF-7 cells treated with 1,25(OH)(2)D(3) or EB 1089 revealed apoptosis-like morphology characterized by the condensed cytoplasm, nuclei, and chromatin. Overall, these results suggest that calpain may take over the role of the major execution protease in apoptosis-like death induced by vitamin D compounds. Thus, these compounds may prove useful in the treatment of tumors resistant to therapeutic agents dependent on the classical caspase cascade.

Topics: Apoptosis; Breast Neoplasms; Calbindins; Calcitriol; Calcium; Calpain; Female; Humans; S100 Calcium Binding Protein G; Thapsigargin; Tumor Cells, Cultured

The Nuclear Factor (NF)-kappaB family of transcription factors controls expression of genes which promote cell growth, survival, and neoplastic transformation. Recently we demonstrated aberrant constitutive activation of NF-kappaB in primary human and rat breast cancer specimens and in cell lines. Overexpression of the epidermal growth factor receptor (EGFR) family member Her-2/neu, seen in approximately 30% of breast cancers, is associated with poor prognosis. Previously, Her-2/neu has been shown to signal via a phosphatidylinositol 3 (PI3)-kinase to Akt/protein kinase B (PKB) pathway. Since this signaling pathway was recently shown to activate NF-kappaB, here we have tested the hypothesis that Her-2/neu can activate NF-kappaB in breast cancer. Overexpression of Her-2/neu and EGFR-4 in Ba/F3 cells led to constitutive PI3- and Akt kinase activities, and induction of classical NF-kappaB (p50/p65). Similarly, a tumor cell line and tumors derived from MMTV-Her-2/neu transgenic mice displayed elevated levels of classical NF-kappaB. Engagement of Her-2/neu receptor downregulated the level of NF-kappaB. NF-kappaB binding and activity in the cultured cells was reduced upon inhibition of the PI3- to Akt kinase signaling pathway via ectopic expression of kinase inactive mutants, incubation with wortmannin, or expression of the tumor suppressor phosphatase PTEN. Inhibitors of calpain, but not the proteasome, blocked IkappaB-alpha degradation. Inhibition of Akt did not affect IKK activity. These results indicate that Her-2/neu activates NF-kappaB via a PI3- to Akt kinase signaling pathway that can be inhibited via the tumor suppressor PTEN, and is mediated by calpain rather than the IkappaB kinase complex.

Topics: Animals; Breast Neoplasms; Calpain; DNA-Binding Proteins; Female; Genes, Tumor Suppressor; Humans; I-kappa B Proteins; Mammary Neoplasms, Animal; Mice; Mice, Transgenic; NF-kappa B; NF-KappaB Inhibitor alpha; Phosphatidylinositol 3-Kinases; Phosphoric Monoester Hydrolases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Receptor, ErbB-2; Signal Transduction; Tumor Cells, Cultured; Tumor Suppressor Proteins

Tensin is a focal-adhesion molecule that binds to actin filaments and interacts with phosphotyrosine-containing proteins. To analyse tensin's function in mammals, we have cloned tensin cDNAs from human and cow. The isolated approx. 7.7-kb human cDNA contains an open reading frame encoding 1735 amino acid residues. The amino acid sequence of human tensin shares 60% identity with chicken tensin, and contains all the structural features described previously in chicken tensin. This includes the actin-binding domains, the Src homology domain 2, and the region similar to a tumour suppressor, PTEN. Two major differences between human and chicken tensin are (i) the lack of the first 54 residues present in chicken tensin, and (ii) the addition of 34- and 38-residue inserts in human and bovine tensin. In addition, our interspecies sequencing data have uncovered the presence of a glutamine/CAG repeat that appears to have expanded in the course of evolution. Northern-blot analysis reveals a 10-kb message in most of the human tissues examined. An additional 9-kb message is detected in heart and skeletal muscles. The molecular mass predicted from the human cDNA is 185 kDa, although both endogenous and recombinant human tensin migrate as 220-kDa proteins on SDS/PAGE. The discrepancy is due to the unusually low electrophoretic mobility of the central region of the tensin polypeptide (residues 306-981). A survey of human prostate and breast cancer cell lines by Western-blot analysis shows a lack of tensin expression in most cancer cell lines, whereas these lines express considerable amounts of focal-adhesion molecules such as talin and focal-adhesion kinase. Finally, tensin is rapidly cleaved by a focal-adhesion protease, calpain II. Incubation of cells with a calpain inhibitor, MDL, prevented tensin cleavage and induced morphological change in these cells, suggesting that cleavage of tensin and other focal-adhesion constituents by calpain disrupts maintenance of normal cell shape.

Topics: 3T3 Cells; Amino Acid Sequence; Animals; Blotting, Northern; Blotting, Western; Breast Neoplasms; Calpain; Cattle; Chickens; Cloning, Molecular; DNA, Complementary; Electrophoresis, Polyacrylamide Gel; Female; Gene Library; Glutathione Transferase; Humans; Male; Mice; Microfilament Proteins; Microscopy, Fluorescence; Molecular Sequence Data; Open Reading Frames; Prostatic Neoplasms; Protein Structure, Tertiary; Recombinant Fusion Proteins; Recombinant Proteins; Sequence Homology, Amino Acid; Tensins; Time Factors; Tissue Distribution; Transfection; Tumor Cells, Cultured

We have shown previously that rats can be cured from induced peritoneal colon carcinomatosis by injections of apoptotic bodies derived from tumor cells and interleukin 2. This curative treatment generated a tumor-specific cytotoxic T-cell response associated with a humoral response. Autoantibodies from sera of cured rats strongly recognized a Mr 67,000 protein from apoptotic bodies and weakly reacted with a protein of Mr approximately 97,000 in PROb parental cells. We now show that these autoantibodies are directed against BARD1, originally identified as a protein interacting with the product of the breast cancer gene 1, BRCA1. We demonstrate that the Mr 67,000 antigen is a cleaved form of BARD1 present in apoptotic bodies derived from rat and human colon and mammary carcinoma cell lines. Moreover, we show that the cleavage site of BARD1 is located NH2 terminally but downstream of the RING domain essential for BARD1 and BRCA1 protein interaction. In vitro studies using [35S]methionine-labeled human BARD1 and apoptotic cellular extracts derived from SW48 carcinoma cells indicate that BARD1 proteolysis occurs at an early stage of apoptosis and in a cell cycle-dependent manner. This hydrolysis is inhibited by EGTA, and the calpain inhibitor I, N-acetyl-leu-leu-norleucinal, but not by several caspases inhibitors, suggesting that BARD1 is hydrolyzed by the calcium-dependent cysteine proteases, calpains. Thus, the highly immunogenic form of cleaved BARD1 could contribute to the antitumoral response mediated by apoptotic bodies.

Topics: Amino Acid Sequence; Animals; Antibodies, Monoclonal; Apoptosis; Autoantigens; Blotting, Western; BRCA1 Protein; Breast Neoplasms; Calpain; Carrier Proteins; Cell Cycle; Cell Fractionation; Cloning, Molecular; Colonic Neoplasms; Cysteine Proteinase Inhibitors; DNA, Complementary; Egtazic Acid; Enzyme Inhibitors; Gene Library; Humans; Leupeptins; Mammary Neoplasms, Animal; Mice; Molecular Sequence Data; Precipitin Tests; Protein Binding; Protein Structure, Tertiary; Rats; Sequence Homology, Amino Acid; Tumor Cells, Cultured; Tumor Suppressor Proteins; Ubiquitin-Protein Ligases

The p53 tumor suppressor protein is activated in cells in response to DNA damage and prevents the replication of cells sustaining genetic damage by inducing a cell cycle arrest or apoptosis. Activation of p53 is accompanied by stabilization of the protein, resulting in accumulation to high levels within the cell. p53 is normally degraded through the proteasome following ubiquitination, although the mechanisms which regulate this proteolysis in normal cells and how the p53 protein becomes stabilized following DNA damage are not well understood. We show here that p53 can also be a substrate for cleavage by the calcium-activated neutral protease, calpain, and that a preferential site for calpain cleavage exists within the N terminus of the p53 protein. Treatment of cells expressing wild-type p53 with an inhibitor of calpain resulted in the stabilization of the p53 protein. By contrast, in vitro or in vivo degradation mediated by human papillomavirus E6 protein was unaffected by the calpain inhibitor, indicating that the stabilization did not result from inhibition of the proteasome. These results suggest that calpain cleavage plays a role in regulating p53 stability.

Topics: Adenosine Triphosphate; Adenylyl Imidodiphosphate; Amino Acid Sequence; Breast Neoplasms; Calpain; Carcinoma; Chelating Agents; Cysteine Proteinase Inhibitors; Edetic Acid; Humans; Molecular Sequence Data; Mutation; Oncogene Proteins, Viral; Papillomaviridae; Repressor Proteins; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Topics: Breast Neoplasms; Calpain; Female; Humans