MCL-1 has been recognized as the major critical protein accounting for the resistance of leukemia cells against FDA-approved BH3 mimetic drugs, such as ABT-737 [38] that antagonizes BCL-2, BCL-xL, or BCL-w and venetoclax (ABT-199, the BCL-2 specific inhibitor) [41]. This evidence concerns the gene BCL2L1 and leukemia.