The five most stably expressed genes across the four melanoma cell lines were CASC3 (0.51 ± 0.09), PUM1 (0.44 ± 0.23), HPRT1 (0.77 ± 0.10), POLR2A (1.14 ± 0.04) and RPS2 (0.85 ± 0.04), as can be seen in Fig. 5b. This evidence concerns the gene HPRT1 and melanoma.