thiostrepton and Cell-Transformation--Neoplastic

Aldehyde dehydrogenase 1 (ALDH1) is a cancer stem-like cell (CSC) marker in human cancers; however, the specific ALDH1-regulated function and its underlying signalling pathways have not been fully demonstrated. Here, we investigated the ALDH1-regulated function and its underlying signalling and tested whether all-trans retinoic acid (ATRA) can suppress ALDH1-regulated tumour behaviour in ovarian cancer cells. By modulating ALDH1 expression using flow cytometry enrichment and exogenous overexpression or knockdown, we showed that the ALDH1 activity is positively correlated with stemness in ovarian cancer cells according to measures such as sphere formation and CSC marker expression as well as tumourigenesis in a mouse xenograft model. The findings indicate that the ALDH1 directly regulates the functions of ovarian cancer cells. We also showed that ALDH1 can regulate the expression of FoxM1 and Notch 1, which are involved in the downstream signalling of ALDH1-mediated biofunctions. Inhibition of FoxM1 by Thiostrepton and of Notch1 by DAPT downregulated the sphere formation ability of cells. ATRA reduced ALDH1 expression, suppressed tumour formation and inhibited sphere formation, cell migration and invasion in ALDH1-abundant ovarian cancer cells. We conclude that ATRA downregulates ALDH1/FoxM1/Notch1 signalling and suppresses tumour formation in ovarian cancer cells.

Topics: Aldehyde Dehydrogenase 1 Family; Animals; Antineoplastic Agents; Cell Movement; Cell Transformation, Neoplastic; Dipeptides; Down-Regulation; Female; Forkhead Box Protein M1; Forkhead Transcription Factors; Humans; Isoenzymes; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Invasiveness; Neoplasm Transplantation; Neoplastic Stem Cells; Ovarian Neoplasms; Receptor, Notch1; Retinal Dehydrogenase; RNA Interference; RNA, Small Interfering; Spheroids, Cellular; Thiostrepton; Transplantation, Heterologous; Tretinoin; Tumor Cells, Cultured

Forkhead box M1 (FOXM1) is a typical proliferation‑associated transcription factor, which is overexpressed in many types of human cancer. We investigated the expression level of FOXM1 in patients with untreated acute leukemia (AL) and explored the correlation between expression levels and AL type. The relationship between the expression of the genes FOXM1 and mammalian target of rapamycin (mTOR) was determined after treatment of ML-2 cells with thiostrepton. The apoptosis, proliferation and cell-cycle progression of ML-2 lines were examined after treatment with metformin. We found that FOXM1 is expressed in the majority of AL patients and that its expression level was associated with the AL type. Thiostrepton is a specific inhibitor of FOXM1, and by inhibiting the FOXM1 expression via thiostrepton, we observed downregulatiion of mTOR; a significant correlation between FOXM1 and mTOR levels was observed. Thus, metformin may be involved in the downregulation of FOXM1. In addition, our study demonstrated that metformin promotes the apoptosis of ML-2 cells, induces cell-cycle arrest at the G0/G1 and G2/M phases, and inhibits proliferation. The potential role of FOXM1 in tumorigenesis renders it an attractive target for anticancer therapy, and metformin may represent a new agent for the treatment of leukemia.

Topics: Apoptosis; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Down-Regulation; Forkhead Box Protein M1; Forkhead Transcription Factors; Gene Expression Regulation, Neoplastic; Humans; Leukemia; Metformin; Thiostrepton; TOR Serine-Threonine Kinases

Nasopharyngeal carcinoma (NPC) is a head and neck malignant tumor rare throughout most of the world but common in Southern China. Forkhead box M1 (FoxM1) transcription factor has been shown to play important role in the development and progression of human cancers. We have previously found that FoxM1 was overexpressed in NPC patients and was associated with development of NPC. However, the exact functional significance of FoxM1 and its inhibitor thiostrepton in NPC is little known. The purpose of this study was to investigate in vitro activity of down-regulation of FoxM1 by thiostrepton or siRNA against NPC cell line. FoxM1 inhibition by thiostrepton or siRNA inhibited proliferation of NPC cells by down-regulation of cyclin D1 and cyclin E1. Transformation ability of NPC cells was suppressed by thiostrepton. FoxM1 inhibition by thiostrepton induced apoptosis of NPC cells by down-regulation of bcl-2, up-regulation of bax and p53, and inducing release of cytochrome c accompanied by activation of caspase-9, cleaved caspase-3 and cleaved PARP. In addition, FoxM1 inhibition by siRNA transfection also down-regulated expression of bcl-2 and up-regulated expression of bax, p53, cleaved caspase-3 and cleaved PARP. Furthermore, FADD and cleaved caspase-8 expression were up-regulated by thiostrepton or FoxM1 siRNA, and expression of cIAP1 and XIAP was inhibited by thiostrepton. At last, FoxM1 inhibition by thiostrepton reduced the expression of HIF-1α and VEGF, and transfection of FoxM1 siRNA decreased VEGF expression but not HIF-1α. Collectively, our finding suggest that FoxM1 inhibition by thiostrepton or siRNA suppresses proliferation, transformation ability, angiogenesis, and induces apoptosis of NPC.

Topics: Angiogenic Proteins; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Carcinoma; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Down-Regulation; Forkhead Box Protein M1; Forkhead Transcription Factors; Gene Expression Regulation, Neoplastic; Humans; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Neovascularization, Physiologic; RNA Interference; Thiostrepton; Time Factors; Transfection

Nanoparticle-encapsulated thiazole antibiotic, thiostrepton, has been shown to be an effective agent for inhibiting tumor growth in solid tumor models through the inhibition of proteasomal activity by the induction of apoptosis in cancer cells. Here, we show the efficacy of thiostrepton-micelles in inhibiting tumor growth in a DEN/PB-induced liver cancer model. We also demonstrate an enhanced anticancer effect of the combination treatment of thiostrepton with bortezomib, another proteasome inhibitor in this liver cancer model.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Boronic Acids; Bortezomib; Carcinoma, Hepatocellular; Cell Transformation, Neoplastic; Diethylnitrosamine; Disease Models, Animal; Liver; Liver Neoplasms; Mice; Phenobarbital; Pyrazines; Thiostrepton

Elevated expression or activity of the transcription factor forkhead box M1 (FOXM1) is associated with the development and progression of many malignancies, including breast cancer. In this study, we show that the thiazole antibiotic thiostrepton selectively induces cell cycle arrest and cell death in breast cancer cells through down-regulating FOXM1 expression. Crucially, our data show that thiostrepton treatment reduced FOXM1 expression in a time- and dose-dependent manner, independent of de novo protein synthesis and predominantly at transcriptional and gene promoter levels. Our results indicate that thiostrepton can induce cell death through caspase-dependent intrinsic and extrinsic apoptotic pathways as well as through caspase-independent death mechanisms, as observed in MCF-7 cells, which are deficient of caspase-3 and caspase-7. Cell cycle analysis showed that thiostrepton induced cell cycle arrest at G(1) and S phases and cell death, concomitant with FOXM1 repression in breast cancer cells. Furthermore, thiostrepton also shows efficacy in repressing breast cancer cell migration, metastasis, and transformation, which are all downstream functional attributes of FOXM1. We also show that overexpression of a constitutively active FOXM1 mutant, DeltaN-FOXM1, can abrogate the antiproliferative effects of thiostrepton. Interestingly, thiostrepton has no affect on FOXM1 expression and proliferation of the untransformed MCF-10A breast epithelial cells. Collectively, our data show that FOXM1 is one of the primary cellular targets of thiostrepton in breast cancer cells and that thiostrepton may represent a novel lead compound for targeted therapy of breast cancer with minimal toxicity against noncancer cells.

Topics: Antineoplastic Agents; Breast Neoplasms; Caspases; Cell Cycle; Cell Death; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Transformation, Neoplastic; Female; Forkhead Box Protein M1; Forkhead Transcription Factors; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Invasiveness; Promoter Regions, Genetic; RNA, Messenger; Thiostrepton