CDK4 and colorectal carcinoma: Finally, PD023309, a CDK4/6 inhibitor, did not show KRAS selectivity in the CRC tumour cell lines tested (p = ns, two-way ANOVA) (Fig 7C, S10C Fig, S4 Table), although Barbacid and colleagues have previously demonstrated that PD023309 inhibits the proliferation of KRAS p.G12V-induced non-small cell lung cancer (NSCLC) cells [17].