Effects of DNA Methylation Inhibitors on Molecular and Structural Changes in Chromatin Organization in Leukemia Cells.

DNA methylation inhibitors are widely used in treating myeloid malignancies, yet their precise effects on chromatin organization and nuclear architecture remain incompletely understood. Here, the integrated molecular, cellular, and biophysical approaches to investigate the impact of azacitidine (AZA) and decitabine (DEC) on chromatin structure and nuclear mechanics in AML-007 leukemia cells are presented. Confocal microscopy revealed drug-induced alterations in nuclear morphology and actin cytoskeleton organization, with DEC inducing significant nuclear enlargement and disorganization at lower concentrations (1.0 µM) compared to AZA (5.0 µM). Chromatin condensation assays demonstrated that DEC increased chromatin accessibility in a concentration-dependent manner, while AZA produced subtler effects. Optical tweezers measurements showed both agents reduced nuclear stiffness, with DEC exerting a greater impact. Spectroscopic analysis confirmed differential drug incorporation into DNA, with higher methylation loss and structural changes observed following DEC treatment. Refractive index mapping revealed chromatin decompaction, aligning with increased accessibility and nuclear softening. These findings demonstrate that DNA hypomethylating agents exert distinct, concentration-dependent effects on nuclear organization and chromatin structure, which can be quantified through molecular and biophysical readouts. This study underscores the value of integrative methods for revealing epigenetic drug effects on chromatin architecture in leukemia cells.