CHEK1 and small cell lung carcinoma: Recently, the inhibitor of CHK1, prexasertib (LY2606368), was demonstrated to remarkably activate the STING/TBK1/IRF3 innate immune pathway and increase the expression of PD-L1, which contributes to the infiltration and activation of cytotoxic T lymphocytes and significantly potentiates the efficacy of ICIs in SCLC in vivo (7).