INOS over expression reduces K562 cell proliferation and promotes neutrophilic differentiation

Abstract

Abstract Nitric oxide (NO) is low molecular weight gaseous signalling molecule which modulates various immune functions, vasodilation, proliferation, differentiation and apoptosis. NO at low concentrations protects cells from apoptosis or induced proliferation, whereas at high concentration it inhibits cell growth and induces apoptotic cell death. Increasing evidences highlight the pro- and anti-tumorigenic effect of iNOS-derived NO depending on its concentration, redox environment, NO flux and the cell type. The present study was undertaken to assess the role of iNOS derived NO on K562 cell line (human myelogenous cell line). Stable over-expression of iNOS as confirmed by enhanced iNOS mRNA/protein expression also NO donor (DETA-NO) treatment exhibited cell cycle arrest, enhanced apoptosis. Apoptosis gene expression profiling indicated that iNOS over-expressed K562 cell line generated a broad set of alterations in the gene expression: Upregulated expression of apoptosis related genes - BCL10, LRDD, Death effector domains (DEDs), caspase 4, caspase 8, tumor necrosis factor (ligand) superfamily, member10 (TNFSF10), FADD as compared to control K562 cells. Using in vitro approach we further assessed the significance of iNOS in C/EBPα induced neutrophilic differentiation of K562 cells. May-Grünwald-Giemsa and hoechst staining demonstrated that ectopic expression of C/EBPα promotes rapid neutrophilic differentiation in K562iNOS cells as compared to K562 cells. Morphologic differentiation was further accompanied by up-regulation of myeloid-specific surface markers CD11b. Altogether, these results implicate that iNOS play a crucial role in cell cycle arrest, apoptosis and neutrophilic differentiation of K562 cells.