Moreover, we used three pairs of cancer cell lines with intact or mutant RB1 and further demonstrated that madrasin, isoginkgetin, UNC3230, PYR-41, a Skp2-inhibitor, and TAK243 exhibited selective effects against RB1-deficient cells, with UNC3230 and TAK243 exhibiting the most dramatic therapeutic window between control and RB1-deficient cells. Here, SKP2 is linked to cancer.