salubrinal and Prostatic-Neoplasms

Topics: Animals; Autophagy; Carcinogenesis; Cinnamates; Endoplasmic Reticulum Stress; Endoplasmic Reticulum-Associated Degradation; Gene Expression Regulation, Neoplastic; Heterografts; Humans; Macrolides; Male; Mice; Microtubule-Associated Proteins; Neoplastic Stem Cells; PC-3 Cells; Prostatic Neoplasms; Sequestosome-1 Protein; Serine Endopeptidases; Thiourea

Androgen deprivation therapy in prostate cancer is extremely effective; however, due to the continuous expression and/or mutagenesis of androgen receptor (AR), the resistance to antihormonal therapy is a natural progression. Consequently, targeting the AR for degradation offers an alternate approach to overcome this resistance in prostate cancer. In this study, we demonstrate that carnosic acid, a benzenediol diterpene, binds the ligand-binding domain of the AR and degrades the AR via endoplasmic reticulum (ER) stress-mediated proteasomal degradative pathway. In vitro, carnosic acid treatment induced degradation of AR and decreased expression of prostate-specific antigen in human prostate cancer cell lines LNCaP and 22Rv1. Carnosic acid also promoted the expression of ER proteins including BiP and CHOP in a dose-dependent manner. Downregulation of CHOP by small interfering RNA somewhat restored expression of AR suggesting that AR degradation is dependent on ER stress pathway. Future studies will need to evaluate other aspects of the unfolded protein response pathway to characterize the regulation of AR degradation. Furthermore, cotreating cells individually with carnosic acid and proteasome inhibitor (MG-132) and carnosic acid and an ER stress modulator (salubrinal) restored protein levels of AR, suggesting that AR degradation is mediated by ER stress-dependent proteasomal degradation pathway. Degradation of AR and induction of CHOP protein were also evident in vivo along with a 53% reduction in growth of xenograft prostate cancer tumors. In addition, carnosic acid-induced ER stress in prostate cancer cells but not in normal prostate epithelial cells procured from patient biopsies. In conclusion, these data suggest that molecules such as carnosic acid could be further evaluated and optimized as a potential therapeutic alternative to target AR in prostate cancer.

Topics: Abietanes; Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Cinnamates; Endoplasmic Reticulum Stress; Gene Expression Regulation, Neoplastic; Humans; Leupeptins; Male; Mice; Prostate-Specific Antigen; Prostatic Neoplasms; Proteolysis; Receptors, Androgen; Thiourea; Transcription Factor CHOP; Unfolded Protein Response; Xenograft Model Antitumor Assays

Tubeimoside-1 (TBMS1), a triterpenoid saponin extracted from the Chinese herbal medicine Bolbostemma paniculatum (Maxim) Franquet (Cucurbitaceae), has shown anticancer activities in various cancer cell lines. The aim of this study was to investigate the anticancer activity and molecular targets of TBMS1 in human prostate cancer cells in vitro.. DU145 and P3 human prostate cancer cells were treated with TBMS1. Cell viability and apoptosis were detected. ROS generation, mitochondrial membrane potential and cell cycle profile were examined. Western blotting was used to measure the expression of relevant proteins in the cells.. TBMS1 (5-100 μmol/L) significantly suppressed the viability of DU145 and P3 cells with IC50 values of approximately 10 and 20 μmol/L, respectively. Furthermore, TBMS1 dose-dependently induced apoptosis and cell cycle arrest at G0/G1 phase in DU145 and P3 cells. In DU145 cells, TBMS1 induced mitochondrial apoptosis, evidenced by ROS generation, mitochondrial dysfunction, endoplasmic reticulum stress, modulated Bcl-2 family protein and cleaved caspase-3, and activated ASK-1 and its downstream targets p38 and JNK. The G0/G1 phase arrest was linked to increased expression of p53 and p21 and decreased expression of cyclin E and cdk2. Co-treatment with Z-VAD-FMK (pan-caspase inhibitor) could attenuate TBMS1-induced apoptosis but did not prevent G0/G1 arrest. Moreover, co-treatment with NAC (ROS scavenger), SB203580 (p38 inhibitor), SP600125 (JNK inhibitor) or salubrinal (ER stress inhibitor) significantly attenuated TBMS1-induced apoptosis.. TBMS1 induces oxidative stress-mediated apoptosis in DU145 human prostate cancer cells in vitro via the mitochondrial pathway.

Topics: Acetylcysteine; Amino Acid Chloromethyl Ketones; Anthracenes; Apoptosis; Caspase 3; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Survival; Cinnamates; Cyclin E; Cyclin-Dependent Kinase 2; Dose-Response Relationship, Drug; Endoplasmic Reticulum Stress; G1 Phase; Humans; Imidazoles; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Kinase Kinase 5; Membrane Potential, Mitochondrial; Oxidative Stress; p38 Mitogen-Activated Protein Kinases; Prostatic Neoplasms; Proto-Oncogene Proteins c-bcl-2; Pyridines; Reactive Oxygen Species; Resting Phase, Cell Cycle; Saponins; Thiourea; Triterpenes

We have previously demonstrated the ability of lovastatin, a potent inhibitor of mevalonate synthesis, to induce tumor-specific apoptosis. The apoptotic effects of lovastatin were regulated in part by the integrated stress response (ISR) that regulates cellular responses to a wide variety of stress inducers. A key regulator of the ISR apoptotic response is activating transcription factor 3 (ATF3) and its target gene CHOP/GADD153. In our study, we demonstrate that in multiple lovastatin-resistant clones of the squamous cell carcinoma (SCC) cell line SCC9, lovastatin treatment (1-25 μM, 24 hr) in contrast to the parental line failed to significantly induce ATF3 expression. Furthermore, the SCC-derived cell lines SCC25 and HeLa that are sensitive to lovastatin-induced apoptosis also preferentially induce ATF3 expression compared to resistant breast (MCF-7) and prostate carcinoma (PC3)-derived cell lines. In HeLa cells shRNA targeting ATF3 expression as well as in ATF3-deficient murine embryonic fibroblasts, lovastatin-induced cytotoxicity and apoptosis were attenuated. In ex vivo HNSCC tumors, lovastatin also induced ATF3 mRNA expression in two of four tumors evaluated. Salubrinal, an agent that can sustain the activity of a key regulator of the ISR eIF2α, further increased the expression of ATF3 and demonstrated synergistic cytotoxicity in combination with lovastatin in SCC cells. Taken together, our results demonstrate preferential induction of ATF3 in lovastatin-sensitive tumor-derived cell lines that regulate lovastatin-induced apoptosis. Importantly, combining lovastatin with salubrinal enhanced ATF3 expression and induced synergistic cytotoxicity in SCC cells.

Topics: Activating Transcription Factor 3; Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Blotting, Western; Breast Neoplasms; Carcinoma, Squamous Cell; Cell Membrane Permeability; Cell Proliferation; Cinnamates; Drug Resistance, Neoplasm; Drug Synergism; Embryo, Mammalian; Eukaryotic Initiation Factor-2; Female; Fibroblasts; Flow Cytometry; Head and Neck Neoplasms; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Immunoenzyme Techniques; Lovastatin; Male; Membrane Potential, Mitochondrial; Mice; Phosphorylation; Prostatic Neoplasms; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Thiourea; Tumor Cells, Cultured