HPRT1 and melanoma: To investigate the stability of eight of the most commonly used reference genes from different functional classes as recommended by Vandesompele and colleagues12 (ACTB, UBC, HMBS, SDHA, HPRT1, TBP, B2M and YHWAZ) within a hypoxic setting we set up an experiment containing two melanoma cell lines expressing high and moderately high endogenous CYGB levels, Malme-3M and A375, incubated under either normoxic or hypoxic conditions for 24 h.