Long non-coding RNA H19 is overexpressed in azacitidine-resistant K562 cells but does not modulate drug sensitivity [smallRNA-Seq]

Resistance to azacitidine represents a major obstacle in the treatment of acute myeloid leukemia (AML), yet the molecular mechanisms remain poorly understood. Long non-coding RNAs (lncRNAs) have been implicated in drug resistance across cancers, with H19 emerging as a promising candidate due to its oncogenic roles and association with adverse outcomes in AML. Here, we investigated whether H19 contributes to azacitidine resistance. Using K562 cells subjected to prolonged drug exposure, we established an azacitidine-resistant model that maintained proliferation and viability and resisted apoptosis under treatment. RNA sequencing revealed robust upregulation of H19 and its derived miR-675-3p/-5p in resistant cells, with similar induction of H19 in sensitive cells after extended azacitidine exposure. However, functional assays demonstrated that neither H19 overexpression in sensitive K562 and KG1a cells nor its downregulation in resistant cells altered proliferation, apoptosis, or drug response. These results suggest that H19 upregulation reflects epigenetic reprogramming during prolonged drug exposure but does not functionally drive resistance. Our findings refine the role of H19 in AML, highlighting the need to distinguish biomarkers of drug exposure from true mediators of resistance when identifying therapeutic targets in azacitidine-resistant AML. Overall design: K562 cells, which are originally sensitive to azacitidine, were continuously exposed to increasing concentrations of the drug for over four months to generate resistant cells. Resistance was validated by comparing the response of sensitive and resistant K562 cells to azacitidine treatment via viablity, proliferation and apoptosis assays. RNA was extracted and sent to Macrogen for Small RNA- sequencing with a coverage of 10M.