thiostrepton and Colonic-Neoplasms

Forkhead box transcription factor M1 (FOXM1) is a proliferation-associated transcription factor involved in tumorigenesis through transcriptional regulation of its target genes in various cells, including dendritic cells (DCs). Although previous work has shown that FOXM1 enhances DC maturation in response to house dust mite allergens, it is not known whether FOXM1 affects DC maturation in the context of tumor-specific immunity. In this study, we examined the central role of FOXM1 in regulating bone marrow-derived dendritic cell (BMDC) maturation phenotypes and function in pancreatic cancer and colon cancer. FOXM1 retarded maturation phenotypes of BMDCs, inhibited promotion of T-cell proliferation, and decreased interleukin-12 (IL-12) p70 in tumor-bearing mice (TBM). Notably, FOXM1 expression was epigenetically regulated by dimethylation on H3 lysine 79 (H3K79me2), a modification present in both tumor cells and BMDCs. Increased H3K79me2 enrichment was observed at the FOXM1 promoter in both BMDCs from TBM, and in BMDCs from wild-type mice cultured with tumor-conditioned medium that mimics the tumor microenvironment (TME). Furthermore, inhibition of the H3K79 methyltransferase DOT1L not only decreased enrichment of H3K79me2, but also downregulated expression of FOXM1 and partially reversed its immunosuppressive effects on BMDCs. Furthermore, we found that FOXM1 upregulated transcription of Wnt family number 5A (Wnt5a) in BMDCs in vitro; we also observed that exogenous Wnt5a expression abrogated BMDC maturation phenotypes by inhibiting FOXM1 and H3K79me2 modification. Therefore, our results reveal that upregulation of FOXM1 by H3K79me2 in pancreatic cancer and colon cancer significantly inhibits maturation phenotypes and function of BMDCs through the Wnt5a signaling pathway, and thus provide novel insights into FOXM1-based antitumor immunotherapy.

Topics: Adenocarcinoma; Adenosine; Animals; Bone Marrow Cells; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Culture Media, Conditioned; Dendritic Cells; Epigenesis, Genetic; Forkhead Box Protein M1; Gene Expression Regulation, Neoplastic; Histone-Lysine N-Methyltransferase; Histones; Humans; Lysine; Male; Methylation; Mice, Inbred BALB C; Mice, Inbred C57BL; Models, Biological; Pancreatic Neoplasms; Phenylurea Compounds; Signal Transduction; Thiostrepton; Wnt-5a Protein

Accumulating evidence shows that colorectal cancer stem cells (CRSCs) are largely responsible for the metastasis and relapse of colorectal cancer (CRC) after therapy. Hence, identifying new agents that specifically target CRSCs would help improve the effectiveness of current CRC therapies. To accelerate identification of agents targeting CRSCs, the Connectivity Map (CMap) approach was used. Among the top-ranked candidates, thiostrepton, a thiazole antibiotic, was selected for further investigation because of its known tumoricidal activity. Thiostrepton could selectively induce apoptosis in CRSC subpopulations in both parental HCT-15 and HT-29 human CRC lines as well as in EMT and chemoresistant clones derived from them. Further, we investigated its inhibitory effects on the sphere- and colony-forming capabilities of the aforementioned CRC lines. The in vitro inhibition of sphere and colony formation was associated with downregulation of various modulators of the stem cell phenotype. The combination of thiostrepton and oxaliplatin eradicated both CD44(+) HCT-15 and HT-29 cells more efficiently than either drug alone. FoxM1, an oncogenic transcription factor, was identified as a critical positive modulator of stemness and as the main target of thiostrepton in the CRC lines. This is the first report showing the selective killing of CRSCs by thiostrepton, which has been proposed to be a promising anti-neoplastic agent. On the basis of its synergism with oxaliplatin in killing CRSCs in vitro, if this activity is confirmed in vivo, thiostrepton may be a promising agent to be used clinically in combination with current chemotherapies to improve the efficacy of these regimens.

Topics: AC133 Antigen; Antigens, CD; Antineoplastic Agents; Apoptosis; Colonic Neoplasms; Glycoproteins; HCT116 Cells; HT29 Cells; Humans; Neoplasm Metastasis; Neoplasm Recurrence, Local; Neoplastic Stem Cells; Organoplatinum Compounds; Oxaliplatin; Peptides; Spheroids, Cellular; Thiostrepton; Tumor Cells, Cultured