HPRT1 and neoplasm: The overexpression of hypoxanthine phosphoribosyltransferase 1 (HPRT1) can contribute to the formation of an immunosuppressive tumor microenvironment by significantly reducing the activation of immune cells (B cells, CD8 + T cells, CD4 + T cells, macrophages, and neutrophils) (Townsend et al., 2019).