Siah2 Inhibitor and the Metabolic Antagonist Oxamate Retard Colon Cancer Progression and Downregulate PD1 Expression

Background: Solid tumors such as colon cancer are characterized by rapid and sustained cell proliferation, which ultimately results in hypoxia, induction of hypoxia-inducible factor- 1α (HIF-1α), and activation of glycolysis to promote tumor survival and immune evasion. We hypothesized that a combinatorial approach of menadione (MEN) as an indirect HIF-1α inhibitor and sodium oxamate (OX) as a glycolysis inhibitor may be a promising treatment strategy for colon cancer. Objectives: We investigated the potential efficacy of this combination for promoting an antitumor immune response and suppressing tumor growth in a rat model of colon cancer. Methods: Colon cancer was induced by once-weekly subcutaneous injection of 20 mg/kg dimethylhydrazine (DMH) for 16 weeks. Control rats received the vehicle and then no further treatment (negative control) or MEN plus OX for 4 weeks (drug control). Dimethylhydrazine-treated rats were then randomly allocated to four groups: DMH alone group and other groups treated with MEN, OX, and a combination of (MEN and OX) for 4 weeks. Serum samples were assayed for the tumor marker carbohydrate antigen (CA19.9), while expression levels of HIF-1α, caspase-3, PHD3, LDH, and PD1 were evaluated in colon tissue samples by immunoassay and qRT-PCR. Additionally, Ki-67 and Siah2 expression levels were examined by immunohistochemistry. Results: The combination of MEN plus OX demonstrated a greater inhibitory effect on the expression levels of HIF-1α, Siah2, LDH, Ki-67, and PD1, and greater enhancement of caspase-3 and PHD3 expression in colon cancer tissues than either drug alone. Conclusion: Simultaneous targeting of hypoxia and glycolysis pathways by a combination of MEN and OX could be a promising therapy for inhibiting colon cancer cell growth and promoting antitumor immunity. Few recent patents are also reviewed in this article.