RB1 and cancer: In addition to DMS-53 and MDA-MB-175, inhibition of S6 phosphorylation was also observed following abemaciclib treatment in cell lines of several other cancer types, including mantle cell lymphoma (MCL; Jeko-1), pancreas cancer (MiaPaCa2), osteosarcoma (U2OS), melanoma (SK-MEL-28), non-small cell lung cancer (NSCLC; A549), and even Rb-null triple negative breast cancer (TNBC; MDA-MB-468) (Supplementary Figure 1C, 1D).