Divergent phenotypic patterns and commitment to apoptosis of Caco-2 cells during spontaneous and butyrate-induced differentiation

Caco-2 cells differentiate spontaneously when cultured in confluence and on exposure to the physiologically relevant short-chain fatty acid, butyrate. This study aimed to compare the phenotype induced by these pathways and th eir relations to cell turnover. Caco-2 cells were treated with butyrate at a nontoxic concentration of 2 mM for 3 days, or allowed to spontaneously di fferentiate for 0-21 days. Brush border hydrolase activities and carcinoemb ryonic antigen (CEA) expression, transepithelial resistance and dome format ion, expression of components of the urokinase system, and cell turnover by flow cytometry, and the degree of DNA fragmentation were quantified. Butyr ate induced increases in alkaline phosphatase activity and CEA expression b ut not the activities of other hydrolases, while culture alone induced prog ressive increases in the activities/ expression of all markers. Butyrate in duced a significantly greater increase in transepithelial resistance (TER) than occurred during culture alone but the densities of domes were similar. Butyrate induced a ninefold increase in urokinase receptor expression and twofold increase in urokinase activity, while culture alone induced a signi ficantly smaller increase in receptor expression, an increase in plasminoge n activator inhibitor-1 but no change in activity. While both stimuli induc ed cell cycle arrest, only butyrate increased the proportion of cells under going apoptosis. In conclusion, differentiation of Caco-2 cells can proceed along multiple pathways but does not necessarily lead to apoptosis. The ph enotypic changes during spontaneous differentiation mimic those that occur in normal colonic epithelial cells in vivo during their migration from the crypt base to neck, while butyrate-induced effects more closely follow thos e occurring when normal colonic epithelial cells migrate from crypt neck to the surface compartment. J. Cell. Physiol. 183:347-354, 2000. (C) 2000 Wil ey-Liss, Inc.