HPRT1 and lung carcinoma: Several recent papers have demonstrated that classical "housekeeping" genes such as GAPDH, HPRT1, and ACTB (β-actin) are inaccurate to normalize different types of clinical samples [23,25-27] In the present study, we have analyzed the expression of a panel of 16 genes in lung cancer cell lines and biopsies, with the goal of identifying the most accurate candidate to be used as a reference gene.