CHEK1 and lung adenocarcinoma: For example, Choi et al (25) reported that the protein expression level of ATM and Chk2 had no effect on the OS of stage I NSCLC patients, and Grabauskiene et al (26) identified that elevated Chk1 expression in early-stage primary lung adenocarcinoma (442 resected specimens) correlated with poor tumor differentiation and significantly diminished patient survival.