CDK4 and colorectal carcinoma: Though the combination of CDK4/6 inhibitors and MEK inhibitors has previously been found to be effective in NRAS-mutant melanoma models [32], we felt that empirically assessing the efficacy of the combination in KRAS-mutant CRC models was necessary to justify consideration of clinical trials in patients with CRC, especially given the many distinctions between RAS-mutated melanomas and CRCs.