CDK4 and colonic neoplasm: Recently, several studies indicated that in addition to inhibiting cell proliferation, CDK4/6 inhibitors may upregulate genes encoding MHC-I and the antigen presentation pathway in breast or colon tumors [23], or alter the tumor microenvironment by suppression of regulatory T cell proliferation [23, 34, 35], or enhanced activation of tumor-infiltrating T cells [22, 24].