CHEK1 and neoplasm: Tumors have abnormal proliferation and abnormal cyclin kinase expression leads to uncontrolled proliferation of tumor cells, which often have germline mutations in homologous recombination repair genes, so they depend on checkpoint proteins related to DNA damage, such as CHEK1, to induce G2 block and integrate threonine kinase (ATM and ATR) signals to repair damaged DNA.