Enhancement of NF-κB expression and activity upon differentiation of human embryonic stem cell line SNUhES3

NF-kappa B is involved in many biological processes including proliferation, survival, and differentiation. Because human embryonic stem (ES) cells have the potential to differentiate to various lineages, understanding mechanisms involved in stemness and lineage differentiation is an important issue. We investigated expression of NF-kappa B in the human ES cell lines SNUhES3 and MizhES4 and found that expression of NF-kappa B mRNA and protein in these two cell lines was significantly lower compared to those of other adult cell lines. However, when SNUhES3 cells were induced to differentiate by retinoic acid, expression levels of NF-kappa B significantly increased compared to undifferentiated SNUhES3 cells. As the components of tumor necrosis factor-alpha (TNF-alpha) signaling are expressed comparably in undifferentiated and differentiated SNUhES3 cells, we examined the responsiveness of SNUhES3 cells to treatment with TNF-alpha, an agonist of NF-kappa B signaling. Nuclear localization of NF-kappa B in response to TNF-alpha was evident in differentiated, but not undifferentiated, SNUhES3 cells. In agreement with this observation, induction of interleukin-8 (IL-8) in response to TNF-alpha was seen only in differentiated SNUhES3 cells. On the basis of an I kappa B kinase (IKK) inhibitor study, expression of IL-8 induced by TNF-alpha was dependent on NF-kappa B activity. Taken together, our results suggest that expression and activity of NF-kappa B is comparatively low in undifferentiated human ES cells, but increases during differentiation of the ES cells.