In breast cancer cells, the deletion of KDM4B not only reduces the transcription of WEE1, CCND1, and CCNA1 (Yang et al., 2010), but also disrupts the estrogen-induced cell cycle G1-S phase transition (Shi et al., 2011), causing breast cancer cells to stall at the G2-M phase (Yang et al., 2010) or G1-S phase (Shi et al., 2011). Here, CCND1 is linked to breast cancer.