calpain and Colonic-Neoplasms

A number of viral and eukaryotic proteins which undergo a lipophilic modification by the enzyme N-myristoyltransferase (NMT: NMT1 and NMT2) are required for signal transduction and regulatory functions. We reported a higher expression of NMT2 in most of the cases of cancerous tissues compared to normal tissues by Western blot analysis. Furthermore, protein-protein interaction of NMTs revealed that m-calpain interacts with NMT1 while caspase-3 interacts with NMT2. Our findings provide the first evidence of higher expression of NMT2 in human colorectal adenocarcinomas and the interaction of both forms of NMT with various signaling molecules. In this review, we summarize the recent findings on NMT2 in human colon cancer in our laboratory.

Topics: Acyltransferases; Calpain; Caspases; Colonic Neoplasms; Humans; Protein Binding; Tumor Suppressor Proteins

Over-expression of calpains in tumor tissues can be associated with cancer progression. Thus, inhibition of calpain activity using specific inhibitors has become a novel approach to control tumor growth. In this study, the anticancer potential of cryptotanshinone in combination with calpain inhibitor had been investigated in colon cancer cells and tumor xenograft. Cryptotanshinone elicited an initial endoplasmic reticular (ER) stress response, whereas prolonged stress would result in the promotion of apoptosis. It was then discovered that cryptotanshinone could cause rapid and sustained increase in cytosolic calcium in colon cancer cells accompanied by early GRP78 overexpression, which could be attenuated by pre-treatment of the calcium chelator BAPTA-AM. Cryptotanshinone also facilitated an early increase in calpain activity, which could be blocked by BAPTA-AM or the calpain inhibitor PD150606. A dynamic interaction between GRP78 and calpain during the action of cryptotanshinone was unveiled. This together with the altered NF-[Formula: see text]B signaling could be abolished by calpain inhibitor. GRP78 knockdown increased the sensitivity of cancer cells to cryptotanshinone-evoked apoptosis and reduction of cancer cell colony formation. Such sensitization of drug action had been confirmed to be p53-dependent by using p53-mutated (HT-29) and p53-deficient (HCT116 p53

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Calcium; Calpain; Colonic Neoplasms; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Gene Expression; Heat-Shock Proteins; Homeostasis; Humans; Mice, Nude; Phenanthrenes; Phytotherapy; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Magnesium (Mg) plays important roles in maintaining genomic stability and cellular redox. Mg also serves as nature's physiological calcium (Ca) channel antagonist, controlling intracellular Ca entry. Because Ca is the most important second messenger, its intracellular concentration is tightly regulated. Excess intracellular Ca can activate aberrant signaling pathways leading to the acquisition of pathological characteristics and cell injury. Several epidemiological studies have linked Mg deficiency (MgD) and increased Ca:Mg ratios with higher incidences of colon cancer and increased mortality. While it is estimated that less than 50% of the US population consumes the recommended daily allowance for Mg, Ca supplementation is widespread. Therefore, we studied the effect of MgD, with variable Ca:Mg ratios on cellular oxidative stress, cell migration, calpain activity, and associated signaling pathways using the CT26 colon cancer cell line. MgD (with Ca:Mg ratios >1) elevated intracellular Ca levels, calpain activity and TRPM7 expression, as well as oxidative stress and cell migration, consistent with observed degradation of full-length E-cadherin, β-catenin, and N-terminal FAK. MgD was accompanied by enhanced degradation of IκBα and the transactivation domain containing the C-terminus of NF-κB p65 (RelA). MgD-exposed CT26 cells exhibited increased p53 degradation and aneuploidy, markers of genomic instability. By contrast, these pathological changes were not observed when CT26 were cultured under MgD conditions where the Ca:Mg ratio was kept at 1. Together, these data support that exposure of colon cancer cells to MgD with physiological Ca concentrations (or increasing Ca:Mg ratios) leads to the acquisition of a more aggressive, metastatic phenotype.

Topics: Calcium; Calpain; Colonic Neoplasms; Humans; Magnesium; Magnesium Deficiency; Oxidative Stress; Phenotype; Protein Serine-Threonine Kinases; TRPM Cation Channels; Tumor Cells, Cultured

Calpain-2 levels are higher in colorectal tumors resistant to chemotherapy and previous work showed calpain-2 inhibitor therapy reduced inflammation-driven colorectal cancer, but direct effects of the inhibitor on colon cancer cells themselves were not demonstrated. In the present study, five human colon cancer cell lines were directly treated with a calpain-2 inhibitor and results showed increased cell death in 4 of 5 cell lines and decreased anchorage-independent growth for all cell five lines. When tested for levels of calpain-2, three cell lines exhibited increasing levels of this enzyme: HCT15 (low), HCC2998 (medium), and HCT116 (significantly higher). This was consistent with gel shift assays showing that calpain-2 inhibitor reduced of NF-κB nuclear translocation most effectively in HCT116 cells. Ability of calpain-2 inhibitor to impede tumor progression in vivo was evaluated using intrarectal transplant of luciferase-expressing cells for these three cell lines. Results showed that calpain-2 inhibitor therapy reduced tumor growth and increased survival only in mice injected with HCT116 cells. These data suggest calpain-2 inhibitor treatment may be most effective on colorectal tumors expressing highest levels of calpain-2.

Topics: Animals; Antineoplastic Agents; Apoptosis; Calpain; Cell Nucleus; Colonic Neoplasms; Disease Progression; Down-Regulation; HCT116 Cells; Humans; Male; Mice; Mice, Nude; NF-kappa B; Survival Analysis; Treatment Outcome; Xenograft Model Antitumor Assays

Increasing evidence has suggested that Capn4 is upregulated and functions as a potential tumor promoter in several human cancer types. However, the potential biological roles and regulatory mechanisms of Capn4 in colorectal cancer (CRC) remains unclear. Here, we found that Capn4 expression was elevated in CRC tissues than adjacent noncancerous tissues. Additionally, we also found that overexpression of Capn4 is significantly correlated with tumor progression and poor survival in CRC patients. Furthermore, our experimental data revealed that increased expression of Capn4 was observed in CRC cell lines and ectopic expression of Capn4 significantly enhanced in vitro cell proliferation, whereas knockdown of Capn4 suppressed CRC cells growth in vitro and in vivo. Moreover, our results indicate that Capn4 promotes cell proliferation by increasing MAPK7 expression, which has been reported to control the proliferation of many cancers. Mechanistically, Capn4 upregulates MAPK7 expression through activation of the Wnt/β-Catenin pathway in CRC cells. Therefore, we identified a tumorigenic role of Capn4 in CRC and suggested a potential therapeutic target for CRC patients.

Topics: Adult; Aged; Aged, 80 and over; beta Catenin; Calpain; Cell Line, Tumor; Cell Movement; Cell Proliferation; Colonic Neoplasms; Female; Humans; Male; Middle Aged; Mitogen-Activated Protein Kinase 7; Wnt Signaling Pathway

The aim of this study was to explore whether LINC00657 can regulate cell proliferation and invasion by regulating the PI3K/AKT pathway and thus participate in the occurrence of colon cancer.. Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was applied to detect the expression levels of LINC00657 and E-cad in colon cancer tissues and corresponding adjacent tissues obtained from 80 patients, and the correlation was analyzed between LINC00657 expression and clinical information of patients such as prognosis, tumor size, tumor stage, and distant metastasis. The expression of LINC00657 and E-cad in colon cancer cell lines was also examined, and the effect of LINC00657 on tumor cell proliferation was evaluated by cell counting kit-8 (CCK-8) assay and colony formation experiments. Meanwhile, transwell assay was performed to evaluate the influence of LINC00657 and CAPN7 on cell invasive ability. In addition, the effect of LINC00657 on CAPN7 and PI3K/AKT pathway was detected by Western blot assay.. The expression levels of LINC00657 and E-cad in tumor tissues decreased remarkably, especially in patients who occurred distant metastasis. Compared with patients with highly-expressed LINC00657, the patients with lower level of LINC00657 had a worse prognosis and an advanced tumor size and TNM stage. Similarly, LINC00657 and E-cad also showed a decrease in colon cancer cell lines. After overexpression of LINC00657, cell viability and invasive ability decreased remarkably while cell apoptosis rate increased significantly. In addition, high expression of LINC00657 in an in vitro model significantly promoted CAPN7 expression and inhibited activation of PI3K/AKT pathway.. LINC00657 had a low expression in colon cancer tissues, which could accelerate cell proliferation and invasion by activating PI3K/AKT pathway and inhibiting CAPN7 expression.

Topics: Caco-2 Cells; Calpain; Cell Line, Tumor; Cell Movement; Cell Proliferation; Colonic Neoplasms; Down-Regulation; Gene Expression Regulation, Neoplastic; HCT116 Cells; Humans; Neoplasm Invasiveness; Neoplasm Metastasis; Neoplasm Staging; Phosphatidylinositol 3-Kinases; Prognosis; Proto-Oncogene Proteins c-akt; RNA, Long Noncoding; Signal Transduction

The chymotrypsin-like total proteasome activity and activity of 26S and 20S pools of proteasomes as well as calpain activitiy were found to be significantly increased in colon cancer tissue as compared to normal colon tissue. Patients with stage T2-4N1-3M0-lcolon cancer had higher activity level of the 26/20S proteasome and total calpain activities than patients with stage T2-4NOMO-1 colon cancer. The chymotrypsin-like total activity of proteasomes and the total activity of caplains in patients with stage T2-4N0-3M1 colon cancer were re- spectively 1.6 and 2.0-fold higher compared to those in patients with stage T2-4N0-3M0 colon cancer. Survival analysis of patients with colon cancer showed that the high level of chymotrypsin-like protesome activity in colon cancer and normal colon tissues (more than 72-1000 units/mg protein and 35-1000 units/mg protein, respectively) and the high level of total calpain activity in colon cancer and normal colon tissues (more than 100.5-1000 Units/mg protein and 52-1000 Units/ mg protein, respectively) were unfavorable factors in terms of 2-year metastasis-free survival.

Topics: Aged; Calpain; Colonic Neoplasms; Female; Humans; Male; Middle Aged; Neoplasm Metastasis; Neoplasm Proteins; Proteasome Endopeptidase Complex

Cancer cell motility is a key phenomenon regulating invasion and metastasis. Focal adhesion kinase (FAK) plays a major role in cellular adhesion and metastasis of various cancers. The relationship between dietary supplementation of calcium and colon cancer has been extensively investigated. However, the effect of calcium (Ca2+) supplementation on calpain-FAK-motility is not clearly understood. We sought to identify the mechanism of FAK cleavage through Ca2+ bound lactate (CaLa), its downstream signaling and role in the motility of human colon cancer cells. We found that treating HCT116 and HT-29 cells with CaLa immediately increased the intracellular Ca2+ (iCa2+) levels for a prolonged period of time. Ca2+ influx induced cleavage of FAK into an N-terminal FAK (FERM domain) in a dose-dependent manner. Phosphorylated FAK (p-FAK) was also cleaved in to its p-N-terminal FAK. CaLa increased colon cancer cells motility. Calpeptin, a calpain inhibitor, reversed the effects of CaLa on FAK and pFAK cleavage in both cancer cell lines. The cleaved FAK translocates into the nucleus and modulates p53 stability through MDM2-associated ubiquitination. CaLa-induced Ca2+ influx increased the motility of colon cancer cells was mediated by calpain activity through FAK and pFAK protein destabilization. In conclusion, these results suggest that careful consideration may be given in deciding dietary Ca2+ supplementation to patient undergoing treatment for metastatic cancer.

Topics: Calcium; Calcium Compounds; Calpain; Cell Adhesion; Cell Line; Cell Movement; Colonic Neoplasms; Focal Adhesion Protein-Tyrosine Kinases; HT29 Cells; Humans; Lactates; Phosphorylation; Signal Transduction; Wound Healing

Neoplastic cells accumulate magnesium, an event which provides selective advantages and is frequently associated with TRPM7 overexpression. Little is known about magnesium homeostasis in drug-resistant cancer cells. Therefore, we used the colon cancer LoVo cell model and compared doxorubicin-resistant to sensitive cells. In resistant cells the concentration of total magnesium is higher while its influx capacity is lower than in sensitive cells. Accordingly, resistant cells express lower amounts of the TRPM6 and 7, both involved in magnesium transport. While decreased TRPM6 levels are due to transcriptional regulation, post-transcriptional events are involved in reducing the amounts of TRPM7. Indeed, the calpain inhibitor calpeptin markedly increases the levels of TRPM7 in resistant cells. In doxorubicin-sensitive cells, silencing TRPM7 shifts the phenotype to one more similar to resistant cells, since in these cells silencing TRPM7 significantly decreases the influx of magnesium, increases its intracellular concentration and increases resistance to doxorubicin. On the other hand, calpain inhibition upregulates TRPM7, decreases intracellular magnesium and enhances the sensitivity to doxorubicin of resistant LoVo cells. We conclude that in LoVo cells drug resistance is associated with alteration of magnesium homeostasis through modulation of TRPM7. Our data suggest that TRPM7 expression may be an additional undisclosed player in chemoresistance.

Topics: Antibiotics, Antineoplastic; Blotting, Western; Calpain; Cell Line, Tumor; Colonic Neoplasms; Cysteine Proteinase Inhibitors; Dipeptides; Doxorubicin; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Homeostasis; Humans; Ion Transport; Magnesium; Protein Serine-Threonine Kinases; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; TRPM Cation Channels

The colon cancer tissues from DMH treated rats exhibited higher membrane potential, fluidity and changed lipid order as examined by Merocyanine 540 and 1,6-diphenyl-1,3,5-hexatriene, respectively. A transition from gel to liquid crystalline state was observed by Laurdan fluorescence and also reduced fluorescence quenching of NBD-PE as contributed in the decreased membrane lipid phase separation. With piroxicam, a traditional NSAID and c-phycocyanin, a biliprotein from Spirulina platensis, these effects were normalized. An augmented intracellular Ca(+2) had contributed to the drug mediated apoptosis which is supported by an elevated calpain-9 expression. Histopathologically, a large pool of secreted acid/neutral mucopolysaccrides as well as the presence of blood vessels and dysplastic crypts signifies invasive mucinous adenocarcinoma while both the drugs reduced these neoplastic alterations. Wnt/β-catenin pathway was also found to be up-regulated which served as a crucial indicator for cancer cell growth. A concomitant down regulation of PPARγ was noted in DMH treatment which is associated with tumor progression. The expression of PPARα and δ, the other two isoforms of PPAR family was also modulated. We conclude that piroxicam and c-phycocyanin exert their anti-neoplastic effects via regulating membrane properties, raising calpain-9 and PPARγ expression while suppressing Wnt/β-catenin signaling in experimental colon carcinogenesis.

Topics: 2-Naphthylamine; Animals; Apoptosis; Calcium; Calpain; Carcinogenesis; Colonic Neoplasms; Fluorescence Polarization; Fura-2; Intracellular Space; Laurates; Ligands; Male; Membrane Fluidity; Membrane Potentials; Phase Transition; Phosphatidylethanolamines; Phycocyanin; Piroxicam; PPAR gamma; Pyrimidinones; Rats, Sprague-Dawley; Up-Regulation; Wnt Signaling Pathway

Glucose-regulated proteins (GRP) are induced in the cancer microenvironment to promote tumor survival, metastasis and drug resistance. AST was obtained from the medicinal plant Astragalus membranaceus, which possesses anti-tumor and pro-apoptotic properties in colon cancer cells and tumor xenograft. The present study aimed to investigate the involvement of GRP in endoplasmic reticulum (ER) stress-mediated apoptosis during colon cancer development, with focus on the correlation between AST-evoked regulation of GRP and calpain activation.. The effects of AST on GRP and apoptotic activity were assessed in HCT 116 human colon adenocarcinoma cells. Calpain activity was examined by using a fluorescence assay kit. Immunofluorescence staining and immunoprecipitation were employed to determine the localization and association between calpains and GRP. GRP78 gene silencing was performed to confirm the importance of GRP in anticancer drug activities. The modulation of GRP and calpains was also studied in nude mice xenograft.. ER stress-mediated apoptosis was induced by AST, as shown by elevation in both spliced XBP-1 and CHOP levels, with parallel up-regulation of GRP. The expression of XBP-1 and CHOP continued to increase after the peak level of GRP was attained at 24 h. Nevertheless, the initial increase in calpain activity as well as calpain I and II protein level was gradually declined at later stage of drug treatment. Besides, the induction of GRP was partly reversed by calpain inhibitors, with concurrent promotion of AST-mediated apoptosis. The knockdown of GRP78 by gene silencing resulted in higher sensitivity of colon cancer cells to AST-induced apoptosis and reduction of colony formation. The association between calpains and GRP78 had been confirmed by immunofluorescence staining and immunoprecipitation. Modulation of GRP and calpains by AST was similarly demonstrated in nude mice xenograft, leading to significant inhibition of tumor growth.. Our findings exemplify that calpains, in particular calpain II, play a permissive role in the modulation of GRP78 and consequent regulation of ER stress-induced apoptosis. Combination of calpain inhibitors and AST could exhibit a more pronounced pro-apoptotic effect. These results help to envisage a new therapeutic approach in colon cancer by targeting calpain and GRP.

Topics: Animals; Antineoplastic Agents; Apoptosis; Astragalus Plant; Calpain; Colonic Neoplasms; Endoplasmic Reticulum Chaperone BiP; HCT116 Cells; HSP70 Heat-Shock Proteins; Humans; Membrane Proteins; Mice; Mice, Nude; Plant Extracts; Saponins; Signal Transduction; Up-Regulation

Higher levels of focal adhesion kinase (FAK) are expressed in colon metastatic carcinomas. However, the signaling pathways and their mechanisms that control cell adhesion and motility, important components of cancer metastasis, are not well understood. We sought to identify the integrin-mediated mechanism of FAK cleavage and downstream signaling as well as its role in motility in human colon cancer GEO cells. Our results demonstrate that phosphorylated FAK (tyrosine 397) is cleaved at distinct sites by integrin signaling when cells attach to collagen IV. Specific blocking antibodies (clone P1E6) to integrin alpha2 inhibited FAK activation and cell motility (micromotion). Ectopic expression of the FAK C-terminal domain FRNK attenuated FAK and ERK phosphorylation and micromotion. Calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal blocked FAK cleavage, cell adhesion, and micromotion. Antisense approaches established an important role for mu-calpain in cell motility. Expression of wild type mu-calpain increased cell micromotion, whereas its point mutant reversed the effect. Further, cytochalasin D inhibited FAK phosphorylation and cleavage, cell adhesion, locomotion, and ERK phosphorylation, thus showing FAK activation downstream of actin assembly. We also found a pivotal role for FAK Tyr(861) phosphorylation in cell motility and ERK activation. Our results reveal a novel functional connection between integrin alpha2 engagement, FAK, ERK, and mu-calpain activation in cell motility and a direct link between FAK cleavage and enhanced cell motility. The data suggest that blocking the integrin alpha2/FAK/ERK/mu-calpain pathway may be an important strategy to reduce cancer progression.

Topics: Biotinylation; Butadienes; Calpain; Cell Adhesion; Cell Line, Tumor; Cell Movement; Colonic Neoplasms; Cytochalasin D; Electric Impedance; Enzyme Activation; Enzyme Inhibitors; Focal Adhesion Protein-Tyrosine Kinases; Humans; Integrin alpha2; Mitogen-Activated Protein Kinases; Nitriles; Nucleic Acid Synthesis Inhibitors; Oligonucleotides, Antisense; Phosphorylation; Point Mutation; Precipitin Tests; Protein Structure, Tertiary; Signal Transduction; Substrate Specificity; Tyrosine

A number of viral and eukaryotic proteins which undergo a lipophilic modification by the enzyme N-myristoyltransferase (NMT: NMT1 and NMT2) are required for signal transduction and regulatory functions. To investigate whether NMT2 contributes to the pathogenesis of colorectal carcinoma, we observed a higher expression of NMT2 in most of the cases of cancerous tissues compared to normal tissues (84.6% of cases; P < 0.05) by Western blot analysis. Furthermore, protein-protein interaction of NMTs revealed that m-calpain interacts with NMT1 while caspase-3 interacts with NMT2. Our findings provide the first evidence of higher expression of NMT2 in human colorectal adenocarcinomas and the interaction of both forms of NMT with various signaling molecules.

Topics: Acyltransferases; Calpain; Caspases; Colonic Neoplasms; Gene Expression Regulation, Neoplastic; Humans; Peptide Hydrolases; Protein Binding; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Activation of protein kinase C delta (PKCdelta) is believed to be pro-apoptotic. PKCdelta is reported to be reduced in colon cancers. Using a colon cancer cell line, COLO 205, we have examined the roles of PKCdelta in apoptosis and of caspase-3 in the activation and inhibition of PKCdelta. PKCdelta activation with bistratene A and its inhibition with rottlerin induced apoptosis. Effects of PKC activators and inhibitors were additive, suggesting that PKCdelta down-regulation was responsible for the effects on apoptosis. Different apoptotic pathways induced PKCdelta cleavage, but the fragment produced was inactive in kinase assays. Caspase-3 inhibition did not block DNA fragmentation or PKCdelta proteolysis despite blocking intracellular caspase-3 activity. Calpain inhibition with calpeptin did not prevent TPA-induced PKCdelta cleavage. We conclude that in colonocytes, inhibition of PKCdelta is sufficient to lead to caspase-3-independent apoptosis. Caspase-3 does not cleave PKCdelta to an active form, nor does caspase-3 inhibition block apoptosis.

Topics: Acetamides; Acetophenones; Alkaloids; Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Benzophenanthridines; Benzopyrans; Calpain; Caspase 3; Caspase Inhibitors; Caspases; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Cysteine Proteinase Inhibitors; Dipeptides; DNA Fragmentation; Enzyme Activation; Enzyme Inhibitors; Flow Cytometry; Histones; Humans; Indomethacin; Kinetics; Phenanthridines; Phosphorylation; Protein Kinase C; Protein Kinase C-delta; Pyrans; Spiro Compounds; Tetradecanoylphorbol Acetate; Tumor Necrosis Factor-alpha

Beta-catenin is a multifunctional protein serving both as a structural element in cell adhesion and as a signaling component in the Wnt pathway, regulating embryogenesis and tumorigenesis. The signaling fraction of beta-catenin is tightly controlled by the adenomatous polyposis coli-axin-glycogen synthase kinase 3beta complex, which targets it for proteasomal degradation. It has been recently shown that Ca(2+) release from internal stores results in nuclear export and calpain-mediated degradation of beta-catenin in the cytoplasm. Here we have highlighted the critical relevance of constitutive calpain pathway in the control of beta-catenin levels and functions, showing that small interference RNA knock down of endogenous calpain per se (i.e. in the absence of external stimuli) induces an increase in the free transcriptional competent pool of endogenous beta-catenin. We further characterized the role of the known calpain inhibitors, Gas2 and Calpastatin, demonstrating that they can also control levels, function, and localization of beta-catenin through endogenous calpain regulation. Finally we present Gas2 dominant negative (Gas2DN) as a new tool for regulating calpain activity, providing evidence that it counteracts the described effects of both Gas2 and Calpastatin on beta-catenin and that it works via calpain independently of the classical glycogen synthase kinase 3beta and proteasome pathway. Moreover, we provide in vitro biochemical evidence showing that Gas2DN can increase the activity of calpain and that in vivo it can induce degradation of stabilized/mutated beta-catenin. In fact, in a context where the classical proteasome pathway is impaired, as in colon cancer cells, Gas2DN biological effects accounted for a significant reduction in proliferation and anchorage-independent growth of colon cancer.

Topics: Adenomatous Polyposis Coli Protein; Animals; Axin Protein; beta Catenin; Blotting, Western; Calcium-Binding Proteins; Calpain; Cell Adhesion; Cell Line; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Cytoskeletal Proteins; Genes, Reporter; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Green Fluorescent Proteins; Humans; Intercellular Signaling Peptides and Proteins; Mice; Mice, Inbred BALB C; Microfilament Proteins; Microscopy, Fluorescence; Models, Biological; Mutation; Plasmids; Proteasome Endopeptidase Complex; Repressor Proteins; RNA Interference; RNA, Small Interfering; Signal Transduction; Subcellular Fractions; Time Factors; Trans-Activators; Transfection; Wnt Proteins

Wild type (wt) p21 Bax was cleaved to generate p18 Bax during apoptotic processes by calpain, which was suggested to recognize a certain motif around amino acids 30-33 Phe-Ile-Gln-Asp (FIQD). In the present study, analysis of protein sequencing revealed that the cleavage site was between Gln28 and Gly29. The fragment lacking the NH(2)-terminal amino acids 1-28 (tBax(29)) was more apoptotic than wt Bax. The tBax(29)-induced apoptotic cell death was substantially resistant to Bcl-x(L)-mediated rescue, compared with wt Bax, in spite of the complex formation between these two molecules. Together, the tBax(29) would be valuable for the treatment of tumors with high levels of Bcl-x(L) as well as the understanding of Bax-mediated apoptotic processes.

Topics: Adenocarcinoma; Amino Acid Motifs; Apoptosis; bcl-2-Associated X Protein; bcl-X Protein; Calpain; Cell Line; Codon; Colonic Neoplasms; Humans; Kidney; Mutagenesis, Site-Directed; Peptide Fragments; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Substrate Specificity; Tumor Cells, Cultured

Bax is a crucial mediator of the mitochondrial pathway for apoptosis, and loss of this proapoptotic Bcl-2 family protein contributes to drug resistance in human cancers. We report here that the endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (THG) induces apoptosis of human colon cancer HCT116 cells through a Bax-dependent signaling pathway controlling the cytosolic release of mitochondrial apoptogenic molecules. Treating HCT116 cells with THG results in caspase-8 activation; Bid cleavage; Bax conformational change and mitochondrial translocation; the release of cytochrome c, Smac/Diablo, and Omi/HtrA2 into the cytosol; caspase-3 activation; and apoptosis. In contrast, knockout of Bax completely abrogates the full processing/activation of caspase-3 but has no effect on the processing of caspase-8 and the initial cleavage of caspase-3 to p24 fragment after THG treatment. The caspase-8-specific inhibitor z-IETD-fmk, as well as pan-caspase inhibitor z-VAD-fmk, but not the calpain inhibitor E-64d, prevents Bid cleavage, Bax conformational change, and subsequent caspase-3 processing and apoptosis. Caspase-8 processing is dependent on de novo protein synthesis; DR5 expression is strongly up-regulated by THG treatment. Moreover, the absence of Bax blocks THG-induced Omi and Smac release from mitochondria, and expression of cytosolic Omi (GFP-IETD-Omi) or Smac (GFP-IETD-Smac) restores the sensitivity of Bax-knockout HCT116 cells to apoptosis in response to THG treatment. Taken together, our results indicate that Bax-dependent Smac and Omi release plays an essential role in caspase-3 activation and apoptosis induced by THG in human colon cancer HCT116 cells.

Topics: Apoptosis; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; Calpain; Carrier Proteins; Caspase 8; Caspase 9; Caspases; Colonic Neoplasms; Enzyme Activation; Enzyme Inhibitors; High-Temperature Requirement A Serine Peptidase 2; Humans; Intracellular Signaling Peptides and Proteins; Mitochondria; Mitochondrial Proteins; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Serine Endopeptidases; Signal Transduction; Thapsigargin; Transfection; Tumor Cells, Cultured

Ordered cell cycle progression requires the expression and activation of several cyclins and cyclin-dependent kinases (Cdks). Hyperosmotic stress causes growth arrest possibly via proteasome-mediated degradation of cyclin D1. We studied the effect of hyposmotic conditions on three colonic (Caco2, HRT18, HT29) and two pancreatic (AsPC-1 and PaCa-2) cell lines. Hyposmosis caused reversible cell growth arrest of the five cell lines in a cell cycle-independent fashion, although some cell lines accumulated at the G(1)/S interface. Growth arrest was followed by apoptosis or by formation of multinucleated giant cells, which is consistent with cell cycle catastrophe. Hyposmosis dramatically decreased Cdc2, Cdk2, Cdk4, cyclin B1, and cyclin D3 expression in a time-dependent fashion, in association with an overall decrease in cellular protein synthesis. However, some protein levels remained unaltered, including cyclin E and keratin 8. Selective proteasome inhibition prevented Cdk and cyclin degradation and reversed hyposmotic stress-induced growth arrest, whereas calpain and lysosome enzyme inhibitors had no measurable effect on cell cycle protein degradation. Therefore, hyposmotic stress inhibits cell growth and, depending on the cell type, causes cell cycle catastrophe with or without apoptosis. The growth arrest is due to decreased protein synthesis and proteasome activation, with subsequent degradation of several cyclins and Cdks.

Topics: Apoptosis; Calpain; CDC2 Protein Kinase; CDC2-CDC28 Kinases; Cell Survival; Colonic Neoplasms; Cyclin B; Cyclin B1; Cyclin D1; Cyclin D3; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinases; Cyclins; Cysteine Endopeptidases; DNA Fragmentation; Flow Cytometry; G1 Phase; Giant Cells; Humans; Keratins; Lysosomes; Microscopy, Electron; Models, Biological; Multienzyme Complexes; Osmosis; Osmotic Pressure; Pancreatic Neoplasms; Proteasome Endopeptidase Complex; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; S Phase; Time Factors; 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