Activation of NF-κB binding in HT-29 colon cancer cells by inhibition of phosphatidylinositol 3-kinase

The ubiquitous transcription factor NF-κB, which is activated in cells by diverse stimuli including phosphatidylinositol 3-kinase (PI3-kinase), is a critical factor for cell survival and growth. Inhibition of PI3-kinase enhances enterocyte-like differentiation of the human colon cancer cell line HT-29. The purpose of our study was to determine whether PI3-kinase alters NF-κB in HT-29 cells. Wortmannin, a specific PI3-kinase inhibitor, stimulated NF-κB binding activity in HT-29 cells by 4 h after treatment. Activation of NF-κB occurred without degradation of IκBα, a protein that sequesters NF-κB in the cytosol. In addition to increasing NF-κB binding, either wortmannin or cotransfection with a dominant negative mutant of the p85 regulatory subunit of PI3-kinase (Δp85) induced NF-κB transactivation. Taken together, these results suggest that inhibition of PI3-kinase in HT-29 cells results in induction of NF-κB binding activity and transactivation which is independent of IκBα degradation. (C) 2000 Academic Press.