h-89 and Breast-Neoplasms

The efficacy of protein kinase inhibitors (PKIs) has been shown in clinical assays for cancer, but as isolated agents, they only have a modest effect. One of the most important characteristics of mitogen-activated PKIs is their ability to decrease the apoptotic threshold of cancer cells, sensitizing them to the action of other antiapoptotic agents. The secretory clusterin protein is an inhibitor of apoptosis with a cytoprotective function. We describe the use of clusterin-specific antisense oligonucleotides and siRNA to sensitize breast carcinoma cells to several PKIs. MCF-7 and MDA-MB-231 cells were treated with antisense oligonucleotide or siRNA to clusterin and the following PKIs: H-89, chelerythrine and genistein. The three inhibitors used in this study upregulated clusterin expression and treatments that included antisense oligonucleotide or siRNA to clusterin reduced the number of viable cells more effectively than did treatment with the drugs alone. Therefore, treatment with such combinations may benefit patients with breast cancer.

Topics: Benzophenanthridines; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Clusterin; Down-Regulation; Drug Resistance, Neoplasm; Drug Synergism; Female; Genistein; Humans; Isoquinolines; Oligonucleotides, Antisense; Protein Kinase Inhibitors; RNA, Small Interfering; Sulfonamides; Thionucleotides

Excessive local estrogen production in the breast promotes estrogen-dependent breast cancer. Aromatase is a key enzyme in estrogen biosynthesis. Aromatase inhibitors used in the treatment of breast cancer are very effective, but indiscriminately reduce estrogen synthesis in all tissues, causing major side‑effects. It is thus desirable to develop inhibitors that selectively block aromatase and estrogen production in breast cancer. To this end, it is important to identify the mechanisms by which aromatase is activated in the tumor microenvironment. Prostaglandin E2 (PGE2) and collagen are two important factors in the tumor microenvironment, which contribute to tumor development and progression. In this study, we show that collagen‑induced aromatase expression in adipose stromal cells (ASCs) was significantly reduced by inhibitors of phosphatidylinositide 3‑kinase (PI3K), IκB kinase (IKK), mitogen‑activated protein kinase kinase (MEK), c‑Jun NH2‑terminal kinase (JNK), protein kinase A (PKA), and by the knockdown of the JunB and AKT2 genes. In addition, PGE2‑induced aromatase expression was significantly inhibited by inhibitors of IKK, MEK, JNK, p38 and PKA. These results indicate that the PI3K/AKT/IKK and the mitogen‑activated protein (MAP) kinase pathways are involved in collagen‑ and PGE2‑induced aromatase expression, and also suggest that collagen and PGE2‑induced signaling pathways may crosstalk in regulating aromatase expression. This study enhances our understanding on the mechanism of regulation of aromatase expression by collagen and PGE2. Furthermore, this study provides a theoretical foundation for the development of specific inhibitors of aromatase by exploiting the signaling pathways identified herein in the context of breast cancer.

Topics: Adipose Tissue, White; Aromatase; Breast Neoplasms; Cells, Cultured; Dinoprostone; Enzyme Induction; Female; Humans; I-kappa B Kinase; Isoquinolines; MAP Kinase Signaling System; Molecular Targeted Therapy; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Stromal Cells; Sulfonamides

More than 70% of breast cancers in women require estrogens for cell proliferation and survival. 17β-estradiol (E2) effect on mammary target cells is almost exclusively mediated by its binding to the estrogen receptor-α (ERα) that joins chromatin where it assembles active transcription complexes. The proliferative and pro-survival action of estrogens is antagonized in most cases by retinoic acid (RA), even though the cognate retinoic acid receptor-α (RARα) cooperates with ERα on promoters of estrogen-responsive genes. We have examined at the molecular level the crosstalk between these nuclear receptors from the point of view of their control of cell growth and show here that RA reverts estrogen-stimulated transcription of the pivotal anti-apoptotic bcl-2 gene by preventing demethylation of dimethyl lysine 9 in histone H3 (HeK9me2). As we previously reported, this is obtained by means of E2-triggered activation of the lysine-specific demethylase 1 (LSD1), an enzyme that manages chromatin plasticity in order to allow specific movements of chromosomal regions within the nucleus. We find that E2 fuels LSD1 by inducing migration of the catalytic subunit of protein kinase A (PKA) into the nucleus, where it targets estrogen-responsive loci. RA rescues LSD1-dependent disappearance of H3K9me2 at bcl-2 regulatory regions upon the prevention of PKA assembly to the same sites.

Topics: Breast Neoplasms; Catalytic Domain; Chromatin; Colforsin; Cyclic AMP-Dependent Protein Kinases; Estrogens; Female; Flavonoids; Histone Demethylases; Histones; Humans; Isoquinolines; MAP Kinase Signaling System; MCF-7 Cells; Methylation; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-bcl-2; RNA, Small Interfering; Sulfonamides; Transcription, Genetic; Tretinoin

We have shown that alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, the first and rate-limiting enzyme in polyamine synthesis, has significant antiproliferative and antiinvasive effects in breast cancer cells. We have also reported that these antitumor effects are associated with activation of multiple signaling pathways, including STAT-3, STAT-1, Jun-N-Terminal kinase (JNK), and Mitogen activated protein kinase (MAPK), the latter being found to mediate its antiinvasive action in MDA-MB-435 cells. The present experiments were designed to test the effect of DFMO on the protein kinase A (PKA) pathway and determine its biological significance. We found that DFMO administration (1 mM) to MDA-MB-435 breast cancer cells significantly increased cAMP response element (CRE)-binding protein (CREB) phosphorylation as well as the transactivation of pCRE-luc, a CREB-dependent promoter activated by PKA. To determine the significance of this biochemical effect of DFMO, we used the PKA inhibitor H89 which, as expected, suppressed in a dose-dependent manner (1 and 10 microM) basal and DFMO-induced CREB phosphorylation in our system. Administration of H89 alone was able to suppress proliferation of MDA-MB-435 cells when used at a concentration (10 microM) shown to completely block basal CREB phosphorylation. At concentrations of 0.5 and 1 muM, H89 treatment, while having no antiproliferative effect of its own, potentiated in a dose-dependent fashion the growth inhibitory action of a suboptimal concentration of DFMO (0.01 mM). Ten micromoles of H89 reduced invasiveness of MDA-MB-435 cells in matrigel by approximately 40% (an effect similar to that of 1 mM DFMO). The combination treatment further reduced invasiveness by approximately 80% (P < 0.01 versus the individual treatments). H89 treatment (10 microM) partially reduced DFMO-induced phosphorylation of STAT-3 but not that of STAT-1, Extracellular regulated kinase (ERK), and JNK. In conclusion, our results indicate that PKA signaling exerts proproliferative and proinvasive effects in our experimental system. Therefore, its activation by DFMO represents a compensatory mechanism which should be blocked in order to maximize the antitumor action of the drug. Our data are also consistent with the notion that STAT-3 activation by DFMO is at least in part mediated through the PKA pathway.

Topics: Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cyclic AMP-Dependent Protein Kinases; Eflornithine; Enzyme Inhibitors; Humans; Isoquinolines; JNK Mitogen-Activated Protein Kinases; MAP Kinase Kinase 4; MAP Kinase Signaling System; Neoplasm Invasiveness; Phosphorylation; Promoter Regions, Genetic; Signal Transduction; Sulfonamides

Acquired resistance to tamoxifen (TAM) is a serious therapeutic problem in breast cancer patients, and Her-2/ErbB2 expression is associated with decreased sensitivity to TAM. We previously reported that cAMP-dependent protein kinase (PKA)-mediated activator protein-2 (AP-2) activation was responsible for the expression of Her-2/ErbB2 in p53-inactivated mammary epithelial cells (Yang et al., 2006). In the present study, we tested the hypothesis that PKA plays a role in the expression of ErbB2 in tamoxifen-resistant breast cancer cells. Treatment with H-89, a specific PKA inhibitor, suppressed 4-hydroxytamoxifen-induced ErbB2 expression in control MCF-7 cells. In contrast, PKA inhibition by H-89 or cAMP-dependent protein kinase inhibitor l gamma overexpression increased the expression levels of ErbB2 in TAM-resistant MCF-7 (TAMR-MCF-7) cells. Transcriptional regulation of the erbB2 gene depends on two transcription factors, AP-2 and polyomavirus enhancer activator3 (PEA3). H-89 decreased nuclear or total levels of PEA3 in TAMR-MCF-7 cells. Chromatin immunoprecipitation assay results revealed that H-89 treatment reduced PEA3 binding to the proximal Ets binding site of the erbB2 gene promoter. Reporter gene analyses using human erbB2 gene promoter supported the critical role of PEA3 in the overexpression of ErbB2 in TAMR-MCF-7 cells treated with H-89. This deregulated PKA signaling cascades required for the ErbB2 expression may be important for the differential response of TAM-resistant breast cancer cells to EGF/ErbB2 stimuli.

Topics: Antineoplastic Agents, Hormonal; Breast Neoplasms; Cell Line, Tumor; Cyclic AMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Humans; Intracellular Signaling Peptides and Proteins; Isoquinolines; Promoter Regions, Genetic; Protein Kinase Inhibitors; Receptor, ErbB-2; Signal Transduction; Sulfonamides; Tamoxifen; Transcription Factor AP-2; Transcription Factors; Transcription, Genetic; Transcriptional Activation; Transfection

Antagonists of growth hormone-releasing hormone (GHRH) inhibit growth of various human cancers including breast cancer, xenografted into nude mice or cultured in vitro. Splice variants (SVs) of receptors for GHRH have been found in several human cancers and cancer cell lines. The antiproliferative actions of GHRH antagonists could be mediated in part through these SVs of GHRH receptors. In this study we examined the expression of mRNA for GHRH and SVs of its receptors in human breast cancer cell lines MCF-7, MCF-7MIII, MDA-MB-231, MDA-MB-435, MDA-MB-468, and T47D. mRNA for GHRH was present in all lines tested. mRNA for SV1 isoform of GHRH receptors was found in MCF-7MIII, MDA-MB-468, and T47D; and for SV2 isoform in MCF-7MIII and T47D cell lines. In proliferation studies in vitro, the growth of T47D cells was stimulated by GHRH and dose-dependently inhibited by GHRH antagonist JV-1-38. H89 (protein kinase A inhibitor), bisindolylmaleimide I (protein kinase C [PKC] inhibitor) and verapamil (voltage-dependent calcium channel blocker) inhibited the GHRH-stimulated proliferation of T47D cells. The GHRH antagonist JV-1-38 suppressed the T47D cell growth in vitro stimulated by PKC activator (phorbol-12-myristate-13-acetate). The stimulation of T47D cells by GHRH was followed by an increase in cAMP production and GHRH antagonist JV-1-38 competitively inhibited this effect. Our results suggest that SVs of GHRH receptors could mediate the responses to GHRH and GHRH antagonists in breast cancer through Ca2+-, cAMP- and PKC-dependent mechanisms. The presence of SV1 of GHRH receptors in human cancers provides a rationale for antitumor therapy based on the blockade of this receptor by specific GHRH antagonists.

Topics: Alternative Splicing; Breast Neoplasms; Cell Division; Cyclic AMP; DNA Primers; Female; Growth Hormone-Releasing Hormone; Humans; Indoles; Isoquinolines; Maleimides; Receptors, Neuropeptide; Receptors, Pituitary Hormone-Regulating Hormone; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sulfonamides; Tumor Cells, Cultured; Verapamil

Estrogen acts to promote DNA synthesis in the MCF-7 human breast cancer cell line via its interaction with high levels of estrogen receptor. The primary mode of estrogen action has been considered to be through transcriptional activation of genes containing estrogen response elements, including the immediate early genes c-myc and fos. Recent reports have indicated that estrogen, acting through the estrogen receptor, is capable of inducing the mitogen-activated protein kinase (MAPK) cytoplasmic signaling cascade. In this study, specific small molecule inhibitors of MAPK and phosphatidylinositol 3-kinase activity were used to determine the influence of these cascades on estrogen-mediated mitogenesis. Phosphatidylinositol 3-kinase inhibitors, LY294002 and wortmannin, as well as inhibitors of MAPK kinase-1, PD098059 and U0126, decreased the fraction of cells entering DNA synthesis after treatment with 17beta-estradiol. These compounds did not inhibit expression of myc or fos. However, the drugs did prevent the accumulation of cyclin D1 and hyperphosphorylated retinoblastoma protein, indicating that the block occurred at, or prior to, this point in the cell cycle. Although these compounds were effective in preventing estrogen-mediated mitogenesis, the downstream kinases extracellular signal-regulated kinase 1, extracellular signal-regulated kinase 2, and protein kinase B were not activated over basal levels by estrogen treatment. These studies suggest that estrogen initiates mitogenesis by inducing the transcription of immediate early genes, but cytoplasmic signaling pathways play an important role in the control of subsequent events in the cell cycle.

Topics: Adenocarcinoma; Androstadienes; Breast Neoplasms; Butadienes; Chromones; Culture Media, Serum-Free; Cyclic AMP-Dependent Protein Kinases; Cyclin D1; Depression, Chemical; DNA Replication; Enzyme Activation; Enzyme Inhibitors; Estradiol; Estrogen Receptor Modulators; Estrogens; Female; Flavonoids; Fulvestrant; Humans; Isoquinolines; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Mitosis; Morpholines; Neoplasm Proteins; Neoplasms, Hormone-Dependent; Nitriles; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Retinoblastoma Protein; Sulfonamides; Wortmannin

Cyclic AMP (cAMP) elevation affects growth arrest and differentiation in a wide variety of breast cell lines; however, the mechanisms associated with this process are poorly understood. Previous studies linked cAMP-mediated growth arrest in breast tumor cells to increased levels of cyclin kinase inhibitor (CKI), p21. In the present study we examined the role of cAMP-dependent protein kinase (PKA) on p21 and p27 induction in the breast cancer cell line, MDA-MB-157. The induction of the CKIs by modulators of cAMP such as cholera toxin (CT) + 1-isobutyl-3-methylxanthine (IBMX) and lovastatin fluctuates with biphasic kinetics (although the kinetics of CKI induction with CT + IBMX treatment are different from that of lovastatin) and is depicted by the periodic accumulation of lower molecular weight forms of p21 and p27 which also correlate with fluctuations in CDK2 activity. Using three different approaches we show that the cAMP-mediated induction of CKIs is independent of PKA activity. In the first approach we treated MDA-MB-157 cells with a variety of cAMP modulators such as CT + IBMX, and forskolin in the presence or absence of H-89, a potent PKA inhibitor. This analysis revealed that the cAMP activators were capable of inducing p21 even though PKA activity was completely eliminated. In the second approach PKA dominant negative stable clones of MDA-MB-157 treated with CT + IBMX or forskolin also resulted in p21 induction, in the absence of any PKA activity. Last, treatment of MDA-MB-157 cells with lovastatin, another known cAMP modulator which also causes growth arrest, resulted in the induction of p21 and p27 without any increase in PKA activity. Collectively, the above results suggest that the induction of p21 by cAMP is through a novel pathway, independent of PKA activity.

Topics: 1-Methyl-3-isobutylxanthine; Breast Neoplasms; Cell Cycle Proteins; Cholera Toxin; Colforsin; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Cyclin-Dependent Kinases; Cyclins; Female; Humans; Isoquinolines; Kinetics; Lovastatin; Microtubule-Associated Proteins; Protein Processing, Post-Translational; Sulfonamides; Transfection; Tumor Cells, Cultured; Tumor Suppressor Proteins

Heat shock alters the susceptibility of tumor cells to chemotherapeutic agents. Cultured breast cancer MCF-7 and MDA-MB-231 cells that express high levels of heat shock protein 70 and 27 kDa are resistant to treatment with certain anticancer drugs. These findings indicate that expression of HSPs can negatively regulate the effectiveness of cytotoxic drugs. We conducted experiments to study the regulation of expression of heat shock proteins (HSPs) in human breast cancer MCF-7 cells exposed to heat shock by intracellular free Ca2+ and protein kinase C. Cells exposed to 44 degrees C for 20 min displayed increased expression of HSP-72 and GRP-94, that reached a maximum 4-5 h later and returned to baseline levels within 24 h. Levels of HSP-72 mRNA in cells exposed to heat shock increased, suggesting that the heat-induced increase in HSP-72 occurs at the transcriptional level. The synthesis of HSP-72 but not GRP-94 was inhibited when cells were exposed to heat shock in medium devoid of Ca2+ and attenuated by more than 50% when cells were pretreated with the calcium chelator BAPTA for 30 min prior to heat shock. HSP-72 synthesis was enhanced when cells were treated with the protein kinase C inhibitor, GF-109203X. These data indicate that Ca2+ and PKC are involved in regulation of HSP-72 synthesis. However, removal of external Ca2+ and treatment with BAPTA, GF-109203X, or exposure to sublethal heat shock protected cells from subsequent thermal injury. The intracellular free calcium concentration ([Ca2+]i) in resting fura-2-loaded MCF-7 cells was 156 +/- 16 nM (n = 29). Heat shock increased [Ca2+]i in a time- and temperature-dependent manner. Exposure of cells to 44 degrees C for 20 min increased [Ca2+]i by 234 +/- 13%, which subsequently returned to baseline levels within 120 min. Removal of external Ca2+ eliminated the increase, indicating that the increase in [Ca2+]i was due to Ca2+ influx. Pretreatment of the cells with BAPTA or GF-109203X for 30 min or a sublethal heat shock to allow HSP-72 overexpression led to an attenuation of the increase in [Ca2+]i by a subsequent heat shock. The results suggest that HSP-72 but not GRP-94 is regulated by [Ca2+]i and PKC activity. The cytoprotection produced by chelation of Ca2+, GF-109203X, or HSP-72 overexpression is probably due to their ability to attenuate the [Ca2+]i response to heating.

Topics: Breast Neoplasms; Calcium; Calcium Signaling; Chelating Agents; Cyclic AMP-Dependent Protein Kinases; Cytosol; Egtazic Acid; Enzyme Inhibitors; Female; Heat-Shock Proteins; Hot Temperature; HSP72 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Humans; Isoquinolines; Protein Kinase C; Receptors, Estrogen; Sulfonamides; Tumor Cells, Cultured

Breast cancer cells (BCC) have calcitonin (CT) receptors, yet the action of the hormone on these cells is largely unknown. We found that CT produced a strong and transient time- and dose-dependent increase in c-fos mRNA in BCC lines. This event was prevented by a protein kinase A (PKA) inhibitor, H89. CT alone did not influence the expression of c-jun and of the tissue inhibitors of metalloproteases (timp) -1 and -2 mRNAs; however, it reduced the induction of these mRNAs by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA), without apparent changes in the half-life of the mRNA (measured for c-jun). Along the same line, CT reduced the c-jun induction and T-47D growth stimulation by epidermal growth factor (EGF) and insulin. These effects were mimicked by forskolin and/or prevented by H89, suggesting that PKA activation was involved. These results indicate that CT modulates in BCC the mRNA levels of two important growth-related early response genes (c-fos and c-jun) and of two other genes (timp-1 and -2) involved in the control of metastatic events.

Topics: Blotting, Northern; Breast Neoplasms; Calcitonin; Carcinogens; Cell Division; Colforsin; Dose-Response Relationship, Drug; Drug Interactions; Epidermal Growth Factor; Female; Gene Expression Regulation, Neoplastic; Genes, fos; Genes, jun; Glycoproteins; Humans; Insulin; Isoquinolines; Metalloendopeptidases; Protein Biosynthesis; Protein Kinase Inhibitors; Proteins; Receptors, Calcitonin; RNA, Messenger; Sulfonamides; Tetradecanoylphorbol Acetate; Tissue Inhibitor of Metalloproteinase-2; Tissue Inhibitor of Metalloproteinases; Tumor Cells, Cultured