Long non-coding RNA H19 is overexpressed in azacitidine-resistant K562 cells but does not significantly alter drug sensitivity

Abstract Resistance to azacitidine represents a major obstacle in the treatment of acute myeloid leukemia (AML). The molecular mechanisms underlying this resistance remain poorly understood. Long non-coding RNAs (lncRNAs) have been implicated in drug resistance, with H19 emerging as a promising candidate in AML. Here, we investigated the contribution of H19 to azacitidine resistance in K562 cells, a myeloid leukemia model widely used to study hypomethylating agent response. Prolonged azacitidine exposure generated resistant cells with sustained proliferation and viability and reduced apoptotic response to 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. H19 upregulation was confirmed in azacitidine-resistant HEL AML cells. However, neither H19 overexpression in sensitive K562 and KG1a cells nor its downregulation in resistant K562 cells significantly altered proliferation, apoptosis, or azacitidine response. As H19 silencing could not be achieved in HEL cells, functional validation was limited to a single resistant model. These results suggest that H19 upregulation may reflect epigenetic reprogramming during prolonged drug exposure rather than a driver of resistance, while highlighting the need to distinguish biomarkers of drug exposure from true mediators of resistance in AML.