Betulinic acid-doxorubicin drug combination synergistically supresses cell viability and enhances apoptotic death in acute myeloid leukaemia cell lines by increasing Bax/Bcl-2 ratio

Background Refractory acute myeloid leukaemia (AML) cells are difficult to eradicate with conventional drugs such as doxorubicin (Dox). Overexpression of the anti-apoptotic Bcl-2 protein family in these cells may contribute to the chemoresistance. Betulinic acid (BetA) has shown to cooperate with other chemotherapy drugs in sensitising cancer of epithelial origin to apoptotic death and it may work more efficiently in killing AML cells through combination with Dox. The main aim of this study was to investigate if BetA and Dox combination can induce selective cell death through apoptosis in AML cell line (MOLM13) via modulating the Bcl-2 protein family. Method The effect of BetA (20 μM) and Dox (0.5 and 1 μM) combination on MOLM13 cells and primary normal monocyte cells (NMC) viability was measured by CyQuant Direct assay. Anti-proliferative effect of the test compounds were determined by using CFSE cell labelling. Cell death populations were measured via flow cytometry (AnnexinV/PI) after 48 h cell treatments. The regulation of Bcl-2 protein family (Bax and Bcl-2) was examined by Western blot analysis. Results The study demonstrated that BetA alone and in combination with Dox was statistically potent in inhibiting cell viability of MOLM13 (p 0.05). The combination index (CI) of BetA (20 μM) and Dox (1 μM) showed that the inhibitory effect on AML cells was synergistic (CI>1). Combination treatments have shown to enhance the anti-proliferative effect and increased cell death via apoptosis more than the treatments alone. BetA-Dox combination markedly upregulated Bax protein levels while downregulated Bcl-2 protein levels. In addition, the Bax/Bcl-2 ratio was more elevated in the drug combination than in the single treatments. Conclusion Further studies are underway to investigate the induction of other cell death pathways such as autophagy and necroptosis in AML cells by modulating the Bcl-2 regulation via BetA-Dox drug combination to by-pass resistant cells. Milan Vu1,Milan Vu2,Nick Kassouf2,Celia Bell2,Sandra Appiah2