thiostrepton and Melanoma

Forkhead box M1 (FoxM1) is a transcription factor that regulates cell-cycle progression and tumour progression, but limited information is available regarding its clinical significance in melanoma. The aim of this study was to investigate the potency of FoxM1 as a therapeutic target in melanoma.. We investigated 60 melanoma clinical samples and a melanoma WM266-4 cell line using immunohistochemical staining and molecular biological approaches. Patients with a FoxM1-overexpressing melanoma had significantly shorter survival [both for melanoma-specific survival (MSS) and disease-free survival (DFS)] than the other patients (P < 0.001, respectively). The FoxM1 overexpression was also an adverse prognostic factor for both MSS and DFS on the Cox multivariate analyses [hazard ratio (HR): 3.96, 95% confidence interval (CI): 1.12-14.27, P = 0.032; HR: 3.21, 95% CI: 1.08-9.67, P = 0.037, respectively). FoxM1 inhibition using siRNA and an inhibitor (thiostrepton) each suppressed the cell proliferation of the melanoma cell line. Furthermore, FoxM1 inhibition improved chemosensitivity to dacarbazine, whereas it reduced cell migration and invasion. These results suggest that FoxM1 plays important roles in tumour progression and the chemoresistance of melanoma.. We have shown the prognostic impact of FoxM1 on melanoma patients. FoxM1 inhibition may be a potential therapeutic option for advanced melanoma.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Cell Line, Tumor; Cell Movement; Cell Proliferation; Disease-Free Survival; Female; Forkhead Box Protein M1; Gene Expression Regulation, Neoplastic; Humans; Keratinocytes; Male; Melanoma; Middle Aged; Neoplasm Invasiveness; Prognosis; RNA, Small Interfering; Thiostrepton

Pharmacological induction of oxidative and proteotoxic stress has recently emerged as a promising strategy for chemotherapeutic intervention targeting cancer cells. Guided by a differential phenotypic drug screen for novel lead compounds that selectively induce melanoma cell apoptosis without compromising viability of primary human melanocytes, we have focused on the cyclic pyridinyl-polythiazolyl peptide-antimicrobial thiostrepton. Using comparative gene expression-array analysis, the early cellular stress response induced by thiostrepton was examined in human A375 metastatic melanoma cells and primary melanocytes. Thiostrepton displayed selective antimelanoma activity causing early induction of proteotoxic stress with massive upregulation of heat shock (HSPA6, HSPA1A, DNAJB4, HSPB1, HSPH1, HSPA1L, CRYAB, HSPA5, DNAJA1), oxidative stress (HMOX1, GSR, SOD1), and ER stress response (DDIT3) gene expression, confirmed by immunodetection (Hsp70, Hsp70B', HO-1, phospho-eIF2α). Moreover, upregulation of p53, proapoptotic modulation of Bcl-2 family members (Bax, Noxa, Mcl-1, Bcl-2), and induction of apoptotic cell death were observed. Thiostrepton rapidly induced cellular oxidative stress followed by inactivation of chymotrypsin-like proteasomal activity and melanoma cell-directed accumulation of ubiquitinated proteins, not observed in melanocytes that were resistant to thiostrepton-induced apoptosis. Proteotoxic and apoptogenic effects were fully antagonized by antioxidant intervention. In RPMI 8226 multiple myeloma cells, known to be exquisitely sensitive to proteasome inhibition, early proteotoxic and apoptogenic effects of thiostrepton were confirmed by array analysis indicating pronounced upregulation of heat shock response gene expression. Our findings demonstrate that thiostrepton displays dual activity as a selective prooxidant and proteotoxic chemotherapeutic, suggesting feasibility of experimental intervention targeting metastatic melanoma and other malignancies including multiple myeloma.

Topics: Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Cells, Cultured; Endoplasmic Reticulum Chaperone BiP; Epidermal Cells; Epidermis; Gene Expression Regulation; Heat-Shock Response; Heme Oxygenase-1; HSP70 Heat-Shock Proteins; Humans; Melanocytes; Melanoma; Multiple Myeloma; Oxidative Stress; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proto-Oncogene Proteins c-bcl-2; Thiostrepton; Tumor Cells, Cultured

We previously described the identification of a nucleoside analog transcriptional inhibitor ARC (4-amino-6-hydrazino-7-beta-D-ribofuranosyl-7H-Pyrrolo[2,3-d]-pyrimidine-5-carboxamide) and FoxM1 inhibitor, thiazole antibiotic Siomycin A that were able to induce apoptosis in cancer cell lines of different origin. Here, we report the characterization of these drugs on a panel of melanoma cell lines. We found that in contrast to the common anti-melanoma drug dacarbazine (DTIC), ARC and thiazole antibiotics, Siomycin A and thiostrepton, efficiently inhibited growth and induced cell death in melanoma cell lines in low concentrations. Overexpression of the antiapoptotic protein Mcl-1 protected melanoma cells from apoptosis induced by these compounds. Furthermore, we found that ARC and Siomycin A synergistically induce apoptosis in DM833 melanoma cell line suggesting that they may antagonize different anti-apoptotic pathways in melanoma cells. In general, these drugs may represent important candidates for anti-cancer drug development against melanoma.

Topics: Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Drug Synergism; Humans; Melanoma; Nucleosides; Peptides; Pyrimidines; Thiostrepton

Current standard chemotherapeutic regimens for malignant melanoma are unsatisfactory. Although in vitro studies of arsenic trioxide (ATO) have demonstrated promise against melanoma, recent phase II clinical trials have failed to show any significant clinical benefit when used as a single agent. To enhance the efficacy of ATO in the treatment of melanoma, we sought to identify compounds that potentiate the cytotoxic effects of ATO in melanoma cells. Through a screen of 2,000 marketed drugs and naturally occurring compounds, a variety of antibiotic inhibitors of mitochondrial protein translation were identified.. The mechanism of action for the most effective agent identified, thiostrepton, was examined in a panel of melanoma cells. Effects of combinatorial ATO and thiostrepton treatment on cytotoxicity, apoptosis, mitochondrial protein content, and reactive oxygen species (ROS) were assessed.. Thiostrepton (1 microM) sensitized three out of five melanoma cell lines to ATO-mediated growth inhibition. Treatment with thiostrepton resulted in reduced levels of the mitochondrial-encoded protein cytochrome oxidase I (COX1). Exposure to thiostrepton in combination with ATO resulted in increased levels of cleaved poly (ADP-ribose) polymerase and cellular ROS. The growth inhibitory and pro-apototic effects of addition of the ATO/thiostrepton combination were reversed by the free radical scavenger N-acetyl-L-cysteine.. Our data suggest that thiostrepton enhances the cytotoxic effects of ATO through a ROS-dependent mechanism. Co-administration of oxidative stress-inducing drugs such as thiostrepton in order to enhance the efficacy of ATO in the treatment of melanoma warrants further investigation.

Topics: Antineoplastic Agents; Apoptosis; Arsenic Trioxide; Arsenicals; Cell Line, Tumor; Drug Evaluation, Preclinical; Drug Resistance, Neoplasm; Drug Synergism; Electron Transport Complex IV; Humans; Inhibitory Concentration 50; Melanoma; Mitochondrial Proteins; Oxides; Poly Adenosine Diphosphate Ribose; Protein Biosynthesis; Protein Synthesis Inhibitors; Reactive Oxygen Species; Tetracyclines; Thiostrepton