CDK4 and colorectal carcinoma: Considering colorectal cancer (CRC) samples, one patient had mutations in RB1, PTEN, PIK3CA, NF1, and FBXW7 in one brain metastasis, but not in the primary tumor, while another patient showed mutations in CDK4 only, indicating that these patients might benefit from CDK and PIK/AKT/mTOR pathway inhibitors (Figure 2B).