GENE EXPRESSION IN HUMAN COLON CANCER

We have developed unique methodology which permits quantitation of expression of each of many thousands of cDNA sequences in small biopsies taken from the human colonic mucosa. We have used this method to identify 8 sequences, one of which is subunit 3 of mitochondrial cytochrome c oxidase, whose level of expression changes in progression from normal mucosa to benign adenoma and on to colon carcinoma and whose expression is returned to the level characteristic of the normal mucosa when colon carcinoma cells are induced to differentiate in vitro. In addition, we have determined that high risk polyposis mucosa involves changes in expression of a far greater number of sequences. 29 clones were identified each of whose level of expression provides good discrimination between genetically high risk familial polyposis mucosa and genetically ow risk mucosa. Detection of risk has important practical implications for early detection and prevention. In addition, genetic and other predisposing risk for colon cancer may be more important in the development of colon cancer in the general population than previously appreciated. However, the mucosa at risk is essentially indistinguishable from normal mucosa. We therefore propose to study normal appearing mucosa from three genetic population groups identified epidemiologically as at risk for colorectal cancer (familial colon cancer families, heriditary non-polypotic colon cancer, and Utah pedigrees) and quiescent flat mucosa from patients with ulcerative colitis of >10 years duration. We will use the methodology we have developed and the clones identified, as well as analysis of expression of the genes for EGF, the EGFr, TGFa and the laminin receptor to identify a panel of sequences which can distinguish between genetically low risk flat mucosa and high risk, and amongst the high risk groups. Specific sequences will be selected from expression vector libraries we have made, analyzed further, and antisera developed to the encoded protein to study the changes in expression at the cellular level in biopsy tissue.