Recently, several groups took advantage of the loss-of-function CRISPR-Cas9 system to screen venetoclax-resistant AML cells and reported that acquired drug resistance is mainly dependent on the compensatory expression of anti-apoptotic proteins Mcl-1 and BCL-xl, which are rapidly elevated after exposure to ABT-199 23-26. This evidence concerns the gene MCL1 and acute myeloid leukemia.