In comparison to the bigenic mice containing RXRα mutation and oncogenic mutant NRASQ61K or activated Cdk4R24C/R24C, which didn’t show melanoma formation unless chronically irradiated with UVB for 30 weeks [18], the present trigenic mice (RXRαep/−| Cdk4R24C/R24C| NRASQ61K) develop spontaneous melanoma and in the presence of a single neonatal UVB treatment there is a significant reduction in tumor latency and rapid melanoma progression. The gene discussed is RXRA; the disease is melanoma.