CDK4 and melanoma: NRAS-mutation occurs in 15–20% of melanomas, and the approved ideal treatment for NRAS-mutant melanoma remains unknown, although several combinations of MEK inhibitors with Phosphoinositide 3-kinases (PI3K)–AKT (protein kinase B) pathway inhibitors [10] or CDK4/6 inhibition are proposed and under clinical investigation [11].