RXRA and melanoma: Increased expression of p21 and Cyclin D1 that is observed in the TAN skin of the RXRαep−/−|Tyr-NRASQ61K|Cdk4R24C/R24C mice before and after acute UVB treatment, is likely due to the loss of RXRα in the epidermis, thereby contributing to changes in the expression of signaling molecules in the melanoma microenvironment.