Western blot analysis of the RB-proficient BC lines MCF7, MDA-MB-231 and HCC38, RB-shRNA knockdown lines (MDA-MB-231, HCC38) or RB-deficient lines MDA-MB-436 and BT549 revealed that E2F1 overexpression significantly induced non-glycosylated (ngPD-L1) and glycosylated (gPD-L1) PD-L1 in all lines compared to controls (Fig. 2E, Supplementary Fig. S4A–C). Here, E2F1 is linked to breast cancer.