Since RB1–NUDT15 loss also contributes to the poor prognosis in UCEC (Figures S3C and S7A–C), we conducted similar experiments with HeLa cells, and observed that knocking‐down NUDT15 can sensitize the cells to 6MP in vitro and in vivo, without inducing body weight loss or leucopenia (Figures S14A–C and 6K), suggesting the ubiquitous effects of NUDT15 deficiency on 6MP sensitivity in different cancer types. Here, RB1 is linked to cancer.