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

Background & Aims: Phosphatidylinositol 3-kinase (PI3H), an important media tor of intracellular signal transduction, has been shown to affect prolifer ation, differentiation, and apoptosis in a number of cells; the role of PI3 H in intestinal cell differentiation is not known, Methods: The effect of P I3H inhibition on enterocyte-like differentiation of the human colon cancer cells, HT29 and Caco-2, was assessed using complementary approaches Ii,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 (in testinal alkaline phosphatase [IAP] and sucrase) activities, IAP messenger RNA levels, and IAP promoter induction were measured. Results: The PI3K inh ibitor, wortmannin, in combination with sodium butyrate, synergistically in duced IAP and sucrase enzyme activities and IAP messenger RNA levels in a t ime- and dose-dependent fashion. Consistent with these results, cotransfect ion using the dominant negative mutant of p85 (Delta p85) induced IAP promo ter activity. Moreover, overexpression of PTEN, which antagonizes PI3K, sig nificantly augmented the induction of IAP enzyme activity in HT29 and Caco- 2 cells treated with sodium butyrate and in spontaneously differentiated Ca co-2 cells. Conclusions: Our results show that inhibition of PI3H significa ntly enhances enterocyte-like differentiation of HT29 and Caco-2 cells. Tak en together, our findings suggest a contributory role for the PI3K/PTEN pat hway in intestinal cell differentiation.