Role of p27Kip1 in human intestinal cell differentiation

Abstract

Background & Aims: Growth arrest and differentiation are generally considered to be temporally and functionally linked phenomena in the intestinal epithelium. Methods: To delineate the mechanism(s) responsible for the loss of proliferative potential as committed intestinal cells start to differentiate, we have analyzed the regulation of G1-phase regulatory proteins in relation to differentiation in the intact epithelium as well as in well-established intestinal cell models that allow the recapitulation of the crypt-villus axis in vitro. Results: With intestinal cell differentiation, we have observed an induction of the cell cycle inhibitors p21Cip, p27Kip1, and p57Kip2 expression with an increased association of p27Kip1 and p57Kip2 with cyclin-dependent kinase 2 (Cdk2). At the same time, there was an accumulation of the hypophosphorylated form of the pRb proteins and a strong decline in Cdk2 activity. Stable expression of a p27Kip1 antisense complementary DNA in Caco-2/15 cells did not prevent growth arrest induced by confluence, but repressed villin, sucrase-isomaltase, and alkaline phosphatase expression. Conclusions: Our results indicate that the growth arrest that precedes differentiation involves the activation of Rb proteins and the inhibition of Cdk2. Furthermore, intestinal cell differentiation apparently requires a function of p27Kip1 other than that which leads to inhibition of Cdks.GASTROENTEROLOGY 2001;120:423-438