MUCIN GENES AND COLONIC CELL TRANSFORMATION

To develop better strategies for differentiation therapy for colonic cancer, mechanisms which generate lineages of differentiation and their relationship to mechanisms of transformation must be understood. In colonic cancer, mucinous tumors provide a superb clinical entity in which to investigate this question: though uncommon, the incidence is still greater than 15,000 new cases per year. Further, the tumor is characterized by the vast overexpression of a product similar to that which characterizes the lineages of normal goblet cell differentiation, and yet the prognosis foe patients with these tumors is poor. Thus, understanding the mucin and the mechanisms of deregulation of its synthesis in such tumors, and the link to increased aggressiveness and poor prognosis, will provide significant insight into the relationship of differentiation mechanisms to tumorigenesis and tumor behavior. We have demonstrated that mucinous tumors differ fundamentally from common moderately to well-differentiated colon tumors: they exhibit a small but frequent amplification of the c-myc gene and enormously overexpress a gene for a colonic mucin, a sequence which we have demonstrated can be regulated by TPA and forskolin in culture. They also have a lower frequency of 17P (the p53 gene) deletions (Kern et al, 1989). In this project, we will complete cloning, mapping and sequencing of a mucin core peptide and a link peptide gene; will determine whether these genes are structurally altered in mucinous tumors and tumor cell lines, and if so, define this structural alteration and identify other genes involved; and proceed to identify cis and possibly other regulatory sequences involved in mucin gene expression, and potential differences in these sequences in mucinous colonic tumors and cell lines as compared to normal tissue and non-mucin producing colonic cell lines and tumors. Having accomplished this, we will then be in a position to continue to dissect regulatory elements which lead to the vast constitutive overexpression of at least the core peptide gene in mucinous tumors.