kn-93 and Prostatic-Neoplasms

It has been suggested that the downregulation of AR expression should be considered the principal strategy for the treatment of hormone-refractory prostate cancer. We have previously shown that inhibition of AR induced PI3K-independent activation of Akt that was mediated by CaMKII. In this study, we found that the CaMKII inhibitor KN-93 has a broader effect on apoptosis than just inhibition of CaMKII: first, KN-93 inhibits AR activity and induces cell death in PCa cells after androgen deprivation when many other drugs fail to kill prostate cancer cells; second, KN-93 inhibits expression of the anti-apoptotic protein Mcl-1 and induces expression of the pro-apoptotic protein PUMA; third, KN-93-mediated cell death is p53-independent; and fourth, KN-93 induces the generation of ROS. The ROS induction allows KN-93 to circumvent the activation of Akt, which occurs in prostate cancer cells under androgen deprivation, since Akt could not inhibit ROS-mediated apoptosis. KN-93 also synergistically induces cell death in combination with low doses of doxorubicin and converts the phenotype of prostate cancer cells from TRAIL-resistant to -sensitive. These data suggest that KN-93 could be used for novel therapeutic approaches when hormonal therapy has failed.

Topics: Androgen Receptor Antagonists; Antibiotics, Antineoplastic; Apoptosis; Benzylamines; Blotting, Western; Caspases; Cell Proliferation; Doxorubicin; Drug Synergism; Electrophoretic Mobility Shift Assay; Flow Cytometry; Humans; Immunoenzyme Techniques; Luciferases; Male; Membrane Potential, Mitochondrial; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Sulfonamides; TNF-Related Apoptosis-Inducing Ligand; Transfection; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Notch signaling is associated with prostate osteoblastic bone metastases and calcium/calmodulin-dependent kinase II (CaMKII) is associated with osteoblastogenesis of human mesenchymal stem cells. Here we show that prostate cancer cell lines C4-2B and PC3, both derived from bone metastases and express Notch-1, have all four isoforms of CaMKII (alpha, beta, gamma, delta). In contrast, prostate cancer cell lines LNcaP and DU145, which are not derived from bone metastases and lack the Notch-1 receptor, both lack the alpha isoform of CaMKII. In addition, DU145 cells also lack the beta-isoform. In C4-2B cells, inhibition of CaMKII by KN93 or gamma-secretase by L-685,458 inhibited the formation of the cleaved form of Notch-1 thus inhibiting Notch signaling. KN93 inhibited down stream Notch-1 signaling including Hes-1 gene expression, Hes-1 promoter activity, and c-Myc expression. In addition, both KN93 and L-685,458 inhibited proliferation and Matrigel invasion by C4-2B cells. The activity of gamma-secretase was unaffected by KN93 but markedly inhibited by L-685,458. Inhibition of the expression of alpha, beta, or gamma-isoform by siRNA did not affect Hes-1 gene expression, however when expression of one isoform was inhibited by siRNA, there were compensatory changes in the expression of the other isoforms. Over-expression of CaMKII-alpha increased Hes-1 expression, consistent with Notch-1 signaling being at least partially dependent upon CaMKII. This unique crosstalk between CaMKII and Notch-1 pathways provides new insight into Notch signaling and potentially provides new targets for pharmacotherapeutics.

Topics: Amyloid Precursor Protein Secretases; Animals; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cell Line, Tumor; Cell Proliferation; Humans; Male; Mice; Mice, Nude; Prostatic Neoplasms; Receptor, Notch1; Signal Transduction; Sulfonamides

It has recently been shown that the androgen receptor (AR) is the main factor that required for prostate cancer cells survival. We show that knocking down AR expression by siRNA induces PI3K-independent activation of Akt, which was mediated by calcium/calmodulin-dependent kinase II (CaMKII). We further show, for the first time, that prostate cancer cells express beta,gamma and delta CaMKII genes, and the expression of these genes is under the control of AR activity: active AR in the presence of androgens inhibits CaMKII gene expression whereas inhibition of AR activity results in elevated level of kinase activity and in enhanced expression of CaMKII-beta and -gamma genes. Overexpression of CaMKII genes results in resistance to apoptosis induced by KN-93, a CaMKII inhibitor, or wortmanninn, a PI3K/Akt inhibitor, in combination with doxorubicin, thapsigargin and TRAIL. Moreover, overexpression of CaMKII increases secretion of prostate specific antigen and promotes cell growth of LNCaP in steroid-free condition. Our data show that there is cross-talk between AR- and CaMKII-mediated pathways. The results of this study suggest that CaMKII is an important player in prostate cancer cells ability to escape apoptosis under androgen ablation and facilitate the progression of prostate cancer cells to an androgen independent state.

Topics: Androgen Receptor Antagonists; Androgens; Androstadienes; Antibiotics, Antineoplastic; Apoptosis; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Doxorubicin; Drug Therapy, Combination; Enzyme Inhibitors; Humans; Immunosuppressive Agents; Isoenzymes; Luciferases; Male; Phosphatidylinositol 3-Kinases; Prostate-Specific Antigen; Prostatic Neoplasms; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering; Sulfonamides; Thapsigargin; TNF-Related Apoptosis-Inducing Ligand; Tumor Cells, Cultured; Wortmannin

Diindolylmethane (DIM), derived from indole-3-carbinol in cruciferous vegetables, causes growth arrest and apoptosis of cancer cells in vitro. DIM also induces endoplasmic reticulum (ER) stress, and thapsigargin, a specific inhibitor of the sarcoplasmic reticulum/ER calcium-dependent ATPase, enhances this effect. We asked whether elevated cytosolic free calcium [Ca2+]i is required for cytotoxicity of DIM and thapsigargin in two cancer cells lines (C33A, from cervix, and DU145, from prostate). [Ca2+]i was measured in real-time by FURA-2 fluorescence. We tested whether DIM, thapsigargin, and DIM + thapsigargin cause apoptosis, measured by nucleosome release, under conditions that prevented elevation of [Ca2+]i, using both cell-permeable and cell-impermeable forms of the specific calcium chelator BAPTA. DIM, like thapsigargin, rapidly mobilized ER calcium. C33A and DU145 responded differently to perturbations in Ca2+ homeostasis, suggesting that DIM induces apoptosis by different mechanisms in these two cell lines and/or that calcium mobilization also activates different survival pathways in C33A and DU145. Apoptosis in C33A was independent of increased [Ca2+]i, suggesting that depletion of ER Ca2+ stores may be sufficient for cell killing, whereas apoptosis in DU145 required elevated [Ca2+]i for full response. Inhibitor studies using cyclosporin A and KN93 showed that Ca2+ signaling is important for cell survival but the characteristics of this response also differed in the two cell lines. Our results underscore the complex and variable nature of cellular responses to disrupted Ca2+ homeostasis and suggest that alteration Ca2+ homeostasis in the ER can induce cellular apoptosis by both calcium-dependent and calcium-independent mechanisms.

Topics: Apoptosis; Benzylamines; Calcium; Calcium Signaling; Chelating Agents; Cyclosporine; Cytosol; Egtazic Acid; Endoplasmic Reticulum; Enzyme Inhibitors; Female; Humans; Indoles; Male; Prostatic Neoplasms; Sulfonamides; Thapsigargin; Uterine Cervical Neoplasms