Inhibition of the phosphatidylinositol 3-kinase pathway contributes to HT29 and Caco-2 intestinal cell differentiation

Abstract

Phosphatidylinositol 3-kinase (PI3K), an important mediator of intracellular signal transduction, has been shown to affect proliferation, differentiation, and apoptosis in a number of cells; the role of PI3K in intestinal cell differentiation is not known. The effect of PI3K inhibition on enterocyte-like differentiation of the human colon cancer cells, HT29 and Caco-2, was assessed using complementary approaches (i.e., chemical inhibition with wortmannin, transfection with a dominant negative p85 mutant, or overexpression of the tumor suppressor gene phosphatase and tensin homologue deleted on chromosome 10 [PTEN]). Brush-border enzyme (intestinal alkaline phosphatase [IAP] and sucrase) activities, IAP messenger RNA levels, and IAP promoter induction were measured. The PI3K inhibitor, wortmannin, in combination with sodium butyrate, synergistically induced IAP and sucrase enzyme activities and IAP messenger RNA levels in a time- and dose-dependent fashion. Consistent with these results, cotransfection using the dominant negative mutant of p85 (Deltap85) induced IAP promoter activity. Moreover, overexpression of PTEN, which antagonizes PI3K, significantly augmented the induction of IAP enzyme activity in HT29 and Caco-2 cells treated with sodium butyrate and in spontaneously differentiated Caco-2 cells. Our results show that inhibition of PI3K significantly enhances enterocyte-like differentiation of HT29 and Caco-2 cells. Taken together, our findings suggest a contributory role for the PI3K/PTEN pathway in intestinal cell differentiation.