We found that cyclin K expression was easily detectable in various human cancer cell lines regardless of their p53 status (wild-type p53 in HFF and HCT116, inactivated p53 in HeLa, and p53-null in H1299 and HCT116 p53−/−) (Fig. 1d and Supplementary Fig. 1a). This evidence concerns the gene CCNK and cancer.