CHEK1 and breast cancer: For example, in human breast cancer cells, quercetin inhibits lapatinib-sensitive and -resistant breast cancer cell growth by modifying levels of factors that regulate cell cycle G2/M progression and apoptosis, such as cyclin B1, p-Cdc25c (Ser216), Chk1, caspase 3, caspase 7, and PARP [106].