Effects of different autophagy inhibitors on treatment with ATO/ATRA in KG-1 and HL-60 leukemia cells

Abstract Background : Few current autophagy inhibitors may have beneficial effects for acute myeloid leukemia (AML) patients in clinical phases. However, there is a strong need to figure out which settings should be activated or inhibited in autophagy pathway to prevail drug resistance and improve current treatment options in leukemia. This study aimed to compare the effects of 3 well-known inhibitors of autophagy (3-MA, BafA1 and HCQ) in human leukemia KG1 and HL-60 cells exposed to ATO and/or ATRA. Methods : Cell proliferation and cytotoxicity of KG-1 and HL-60 cells were examined by MTT assay. Autophagy was studied by evaluating the development of acidic vesicular organelles, and the autophagosomes formation was investigated by acridine orange staining and transmission electron microscopy. Gene and protein expression levels of autophagy markers ( ATGs , p62/SQSTM1 and LC-3B) were also performed by qPCR and western blotting, respectively. The rate of apoptosis (annexin-V/PI staining) and cell cycle were evaluated using flow cytometry. Result: We compared the cytotoxic and apoptotic effects of arsenic trioxide (ATO) and/or all-trans retinoic acid (ATRA) in KG1 and HL-60 cells, and demonstrated that some autophagy markers can be upregulated in this context. Also, autophagy blockers HCQ and/or BafA1 could potentiate the cytotoxic effects of ATO/ATRA, which were more pronounced in KG-1 cells compared with HL-60 cell line. Conclusion: This study showed the involvement of autophagy during treatment of KG1 and HL-60 cells with ATO/ATRA.also, this study propose was to propose that combination therapy of ATO/ATRA with the autophagy inhibitor HCQ can be considered as a more effective strategy for targeting leukemic KG-1 cells. Key words: Autophagy, AML, ATO, ATRA