One of our goals is to understand how the regulatory pathways that drive terminal differentiation in the colon epithelium are altered in cancer cells. The HT-29 M6 in vitro differentiation model shows that while terminal differentiation is blocked in these cells, epithelial differentiation and the expression of certain differentiation markers is still conserved in a manner dependent on cell-to-cell contacts. Our results point to certain cell cycle proteins – e.g., the cyclin-dependent kinase inhibitor p27KIP1 – as critical regulators of the expression of several differentiation genes in colon cancer cells (Mayo et al., J Cell Physiol 2007, 212:42-50; work yet to be published). This research line, still ongoing, pursues the identification of regulatory links that may help to understand the critical steps of neoplastic transformation that lead to an impairment of the terminal differentiation process. They may also help to design novel strategies intending to induce differentiation phenotypes in tumor cells.
HT-29 M6 cell differentiation is dependent upon cell-to-cell contact and cell cycle exit in confluent cultures. A, expression of the apical membrane differentiation marker MUC1 in the confluent areas of cell colonies growing in culture (immunoperoxidase). B, apical membrane detection of DPPIV in epithelial monolayers of confluent cultures (immunofluorescence and confocal microscopy analysis). C, mRNA induction of the secreted mucin MUC5AC during the days of cell culture growth to confluence (Northern blot analysis). D, p27KIP1 protein induction as in C (Western blot analysis). E, ectopic expression of p27KIP1 in non-differentiating cells maintained in low-calcium medium (LCM) is sufficient to induce the expression of differentiation markers such as MUC5AC to levels similar to cells differentiated under standard-calcium medium (SCM) (luciferase reporter transcriptional assay using the MUC5AC gene promoter).
Contact: Xavier Mayol, xmayol@imim.es, tel 93.316.04.24, fax 93.316.04.10.
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