Cell Death and Differentiation

Abstract

Intestinal epithelial cell (IEC) lines such as CACO-2 cells serve as important models for the investigation of metabolic and immunologic processes of enterocytes. Many studies are performed with CACO-2 cells adjacent to the bottom of polystyrene cell culture dishes. We therefore addressed the question whether the cultivation on trans-membrane inserts allowing polarized growth/differentiation of these cells alters intra-cellular signal transduction upon cytokine stimulation with cytokines such as interleukin-6 (IL-6). Using western blot techniques and electromobility shift assays we could demonstrate, that IL-6 induced STAT3 activation is almost completely abolished if cells cultured on polystyrene culture dishes, although the required signaling components -gp80 and gp130 receptor subunits and STAT3 protein -are expressed in high levels. Upon culture on microporous membranes IL-6 stimulation results in a strong STAT3 activation if cells are allowed to fully differentiate and stimulated from the basolateral compartment. However, if culture on microporous membranes is terminated as soon as these cells reach confluence stimulation with IL-6 leads only to a weak STAT3 activation which is most likely due to reduced expression levels of the gp80 receptor subunit in this stage of differentiation. In summary these data indicate that in CACO-2 cells appropriate IL-6 signaling only occurs under conditions allowing polarized growth and differentiation of these cells.