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Antineoplastic drugs cause severe cytotoxicity for normal cells, especially hematopoietic stem cells (HSCs). However, bleomycin (BLM) is glycopeptide antibiotic that is effective on various cancers and has either low or no myelosuppression effects. The aim of the present study was to investigate the effect of BLM on 5-Azacitidine (5-AZA) induced cytotoxicity in bone marrow HSCs. 5-AZA reduced HSC cell viability in a time and dose-dependent manner with an IC50 value of 16 μM. However, pretreatment of the cells with BLM for 4 h induced an antagonistic cytotoxicity with an increased IC50 of 64 μM. 5-AZA decreased the colony formation ability of HSC cells in semi-solid agar culture and this effect was attenuated by BLM. 5-AZA significantly downregulated high mobility group Box1 (HMGB1) and Bcl-2 gene expression but upregulated Bax gene expression, while BLM impeded the action of 5-AZA. Pretreatment with BLM remarkably decreased HMGB1 release into culture media that was induced by 5-AZA. The cells were distribution at the sub/G1 phase. Annexin/PI staining of the cells, poly (ADP-ribose) polymerase (PARP) cleavage, and anion superoxide production indicated that BLM limited 5-AZA induced apoptotic cell death. In conclusion, BLM in combination with 5-AZA effectively reduces the adverse cytotoxic effects of 5-AZA on bone marrow hematopoietic stem cells, providing a new chemotherapeutic strategy.BLM reduced sensitivity of hematopoietic stem cells to 5-AZA and arrested the cells at sub-G1.BLM attenuated 5-AZA induced reduction of HMGB1 and Bcl-2 gene expression.Toxicity of 5-AZA on ROS production and PARP cleavage were decreased in combination with BLM.Sequential combination of 5-AZA and BLM, antagonistically reduced apoptotic cell death induced by 5-AZA.Combination of BLM and 5-AZA can be used as a therapeutic strategy to reduce side effects.