CHEK1 and breast cancer: As we have demonstrated in this article, the combination of DNA-damaging agents such as platinum compounds or gemcitabine, but also topotecan and doxorubicin, with CHK1 inhibitors has a synergistic effect on basal-like breast cancer cells that is not observed when combined with agents targeting mitosis, for example, taxotere, eribulin, or vinorelbine.