Induction of iNOS mRNA by interferon-gamma in epithelial cells is associated with growth arrest and differentiation

Induction of inducible nitric oxide synthase (iNOS) mRNA by interferon-gamma (IFNγ) is well established in various cell types. We observed earlier that this induction is differentiation-dependent in human keratinocytes. Since IFNγ-mediated growth arrest and differentiation are separable but interrelated processes in keratinocytes, iNOS might play a role in their regulation. We conducted a series of in vitro experiments on normal and transformed epithelial cells with different tissue origins. We found that immortalization and transformation can influence the IFNγ-mediated iNOS inducibility, but this process is tissue-specific as the induction correlates with the ability of the cells to differentiate.