HPRT1 and urinary bladder cancer: Based on these observations, we have devoted to the identification of the most stable reference genes out of a panel of seven candidates, namely Hypoxanthine phosphoribosyltransferase-1 (HPRT), ACTB, 18 ribosomal RNA (18S), GAPDH, TATA-binding protein (TBP), Beta-2 microglobulin (B2M), and Succinate dehydrogenase complex flavoprotein subunit A (SDHA), to address the effect of hypoxia in the context of bladder cancer.