CDK4 and melanoma: HSP90 is a chaperone protein that is crucially involved in the function and stability of many oncogene products and cell-signaling molecules, including CRAF, ERB-B2, BCR-ABL, CDK4, CDK6, AKT, mutated p53, MEK, VEGFR, and importantly to melanoma mutated (but not wildtype) BRAF.