Moreover, normal neonatal melanocytes and also adult p16-deficient melanocytes will grow for 50 doublings or more under these conditions (Sviderskaya et al., 2003), while metastatic melanomas frequently do yield immortal cultures at ambient oxygen levels (Hsu et al., 2000; Semple et al., 1982). This evidence concerns the gene CDKN2A and metastatic melanoma.