CHEK1 and acute myeloid leukemia: Additionally, ATG4B deficiency in AML cells significantly promoted the activity of the S‐phase checkpoint kinases‐CHK1 (Figure 7F,I,L) and increased the number of AML cells arrested in the S phase (Figure 7G,J,M; Figure S6F–H, Supporting Information), suggesting an enhanced S‐phase checkpoint response in ATG4B‐deficient AML cells.