thiostrepton and Adenocarcinoma

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

Bortezomib is well-known for inducing cell death in cancer cells, specifically through the mechanism of proteasome inhibition. Thiostrepton, a thiazole antibiotic, has also been described for its proteasome inhibitory action, although differing slightly to bortezomib in the proteasomal site to which it is active. Previously we had shown the synergic effect of bortezomib and thiostrepton in breast cancer cells in vitro, where sub-apoptotic concentrations of both proteasome inhibitors resulted in synergic increase in cell death when combined as a treatment. Here, we administered such a combination to MDA-MB-231 xenograft tumors in vivo, and found that the effect of complementary proteasome inhibitors reduced tumor growth rates more efficiently than compared with when administered alone. Increased induction of apoptotic activity in tumors was found be associated with the growth inhibitory activity of combination treatment. Further examination additionally revealed that combination-treated tumors exhibited reduced proteasome activity, compared with non-treated and single drug-treated tumors. These data suggest that this drug combination may be useful as a therapy for solid tumors.

Topics: Adenocarcinoma; Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Boronic Acids; Bortezomib; Breast Neoplasms; Cell Line, Tumor; Drug Synergism; Female; Humans; Male; Mice; Mice, Nude; Nanocapsules; Proteasome Endopeptidase Complex; Pyrazines; Random Allocation; Thiostrepton; Tissue Distribution; Tumor Burden; Xenograft Model Antitumor Assays