CHEK1 and prostate cancer: Whereas TopBP1 is a well-established regulator of the ATR-Chk1 DDR pathway (Cimprich and Cortez, 2008; Yan and Michael, 2009), recent studies have demonstrated that TopBP1 promotes prostate cancer progression and that down-regulation of TopBP1 significantly suppressed the proliferation of prostate cancer 22RV1 and LNCaP cells via an apoptosis-mediated mechanism (Li et al., 2020).