Background and Aims: The human colon cancer-derived cell line HT29 displays a multipotent phenotype. A subclone of HT29 cells containing numerous mucous granules and termed HT29-18-N2 was studied to determine the cellular mechanisms underlying a switch to the differentiated phenotype. Methods: Northern (RNA) blotting, immunoblotting, and immunocytochemistry of HT29-N2 cells, grown under glucose-containing and glucose-free conditions with or without the use of the mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor PD98059, were performed. Results: Loss of activation of the MAP kinases ERK1 and ERK2 in HT29-N2 cells upon a change to glucose-free growth medium preceded the change in phenotype and upregulation of the goblet cell gene product intestinal trefoil factor (ITF). Long-term pharmacological MAP kinase inhibition with the MEK inhibitor PD98059 induced expression of the terminal differentiation markers ITF, sucrase-isomaltase, and the mucin gene MUC2. This was accompanied by morphological evidence of gland formation and mucin secretion and the appearance of discrete goblet cell and enterocyte populations. Induction of ITF and sucrase-isomaltase after MEK inhibition in HT29-N2 cells did not involve loss of MAP kinase responsiveness and was not mediated by receptor tyrosine kinases. Conclusions: Regulation of ERK activation may be a key biochemical switch responsible for terminal differentiation of components of the crypt-villus unit.
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