CHEK1 and small cell lung carcinoma: Because both SCLC and urologic malignancies (such as prostate cancer and bladder cancer are highly proliferative, prone to DNA damage, and highly express CHK1, they may respond similarly to CHK1/2 inhibitors in combination with ICIs (Doerr et al., 2017; Zheng et al., 2018; Twomey and Zhang, 2021).