Effects of BCL-2 and MCL-1 Inhibition on Apoptotic and Transcriptional Profiles in Acute Myeloid Leukemia

Background and Objectives: Acute myeloid leukemia (AML) is characterized not only by its heterogeneity but also by its high relapse rate. This results in limited treatment options, especially in elderly or therapy-refractory patients. It is known that inhibiting anti-apoptotic BCL-2 family proteins can be effective; however, cellular resistance mechanisms often limit the efficacy of this treatment. We studied the effects of the BCL-2 inhibitor ABT-737, the MCL-1 inhibitor S63845, and their combination on AML cell lines and primary AML patient cells. Materials and Methods: To analyze the effects of ABT-737 and S63845 treatment on cells, cell energy phenotype, apoptosis, and cell cycle were assessed, and gene expression by RT-qPCR and protein levels by Western blot analysis were measured. Results: Treatment with the BCL-2 inhibitor ABT-737, the MCL-1 inhibitor S63845, and their combination reduced AML cell viability and induced apoptosis. Dual treatment also altered the expression of epigenetic regulators, as the levels of DNMT1, EZH2, SUZ12, and HDAC1 were reduced, while histone acetylation was increased. An increase in pro-apoptotic markers (PARP cleavage, caspase-9) was observed, and the expression of oncogenes (MYC, WT1) was reduced in model cell lines and primary AML patient cells. Conclusions: BCL-2 and MCL-1 inhibition, alone or in combination, induced apoptosis and altered the expression of epigenetic regulators and oncogenes in AML cell lines and primary patient cells, with no consistent advantage of combined treatment over single agents. BCL-2/MCL-1 inhibition remains a promising approach for AML, and further work should clarify which patients or disease subtypes are most likely to benefit from combined versus single-agent treatment.