CHEK1 and acute lymphoblastic leukemia: The protein levels of CHEK1 were similar in all human T-ALL cell lines tested after 24 h of culture in unconditioned or conditioned media (Supplementary Figure S4B); whereas, paralleling the reduced gene expression levels observed, there were lower CHEK1 protein levels in Jurkat and Loucy T-ALL cells cultured for 48 h in ACM (Figure 3C).