FIGURE 1.

Melanoma onset and growth are independent of pigmentation in TpN mice. (a) Diagram of homozygous alleles in the TpN model. Alleles include a melanocyte-specific, tamoxifen-inducible CRE transgene (Tyr::CreERT2), a conditional p16^INK4a knockout allele (p16^L), and an inducible, oncogenic Nras^61R allele (LSL-Nras^61R). Albino TpN mice are also homozygous for an inactivating tyrosinase gene mutation (G291T; Tyr^c-2j). (b) Breeding scheme used to generate experimental cohorts of black and albino mice. Note that mice heterozygous for the Tyr^c-2j allele (abbreviated Tyr^c in the figure) were not analyzed. (c, d) Kaplan–Meier curves showing the melanoma free (“c”) and overall (“d”) survival of black and albino TpN mice mock irradiated (no UV) or treated with a single dose of 4.5 kJ/m² UVB. Survival was compared among cohorts using log-rank tests. Average melanoma free (MFS) and overall (OS) survivals are shown in the table below each graph. (e) Average number of tumors per mouse at the time of euthanasia. Each dot represents a single mouse with the mean ± SD indicated. No groups were statistically different as determined by a Kruskal–Wallis test with multiple comparisons. (f) Average tumor growth rates for black and albino TpN mice. Each dot represents a single tumor with the mean ± SD indicated. Statistical significance was determined by an ordinary one-way ANOVA with multiple comparisons. *p < .05, ^‡p < .0001.