Upregulation of P2Y2 nucleotide receptor in human hepatocellular carcinoma cells

Objective: To examine if hypoxia inducible factor-1 alpha (HIF-1 alpha) can induce the upregulation of the purinergic receptor P2Y2 (P2Y2) and thereby promote the viability of human hepatocellular carcinoma (HCC) cells under hypoxic conditions. Methods: Archival HCC tumour specimens and corresponding non-cancerous tissues were examined immunohistochemically for P2Y2 protein. A series of in vitro experiments were undertaken using HCC cell lines to determine the effect of hypoxia on HIF-1 alpha and P2Y2 levels, the effect of HIF-1 alpha upregulation on P2Y2 levels, and the effect of P2Y2 upregulation on cell viability under hypoxic conditions. Results: Human HCC specimens were positive for P2Y2. Hypoxia and upregulated HIF-1 alpha both upregulated the P2Y2 levels in HCC cell lines. P2Y2 upregulation using plasmid transfection resulted in enhanced cell viability under hypoxia. Treatment of HepG2 cells with the selective P2Y2 antagonist MRS2312 downregulated P2Y2 and reduced cell viability in five HCC cell lines. P2Y2 knockdown reduced HepG2 cell viability under hypoxia. Conclusions: These present results suggest that HCC cells upregulate P2Y2 levels during hypoxia, which in turn promotes their growth. P2Y2 could be a potential therapeutic target for treating HCC.