RB1 and cancer: We therefore correlated CCNE1 and RB1 expression levels and CCNE1/RB1 ratio with palbociclib IC50 in a large dataset of cancer cell lines.20 In cell lines derived from different cancer types (pan-cancer dataset), these markers significantly correlated with higher IC50 values for palbociclib (Fig. 5a light gray bars, minimum |R| >0.27, maximum FDR = 5*10−14, correlation test) and among all drugs tested in the dataset20 palbociclib showed the strongest association with CCNE1/RB1 ratio (Fig. 5b, R = 0.41, FDR <10−30, correlation test).