EXPRESSION OF HLA CLASS-I ANTIGENS IN SPORADIC ADENOMAS AND HISTOLOGICALLY NORMAL MUCOSA OF THE COLON

The loss of HLA antigens by neoplastic cells is considered important f or tumor growth and metastasis, inasmuch as it may allow tumors to esc ape immune surveillance. We have observed reduced expression of HLA an tigens in sporadic colon cancer and adenomas from familial adenomatous polyposis patients. We now studied the expression of HLA class I anti gens in patients with sporadic adenomas, which are precursors of color ectal cancer. Expression of HLA class I antigens was studied by immuno histochemistry in (a) sporadic colon adenomas, (b) histologically norm al mucosa distant from the adenomas. (c) histologically normal colonic mucosa from patients with history of sporadic colon adenomas, and (d) colonic mucosa from normal subjects. HLA class I antigen expression w as moderately reduced in 56% and severely reduced in 44% of the adenom as; this reduction was significant when compared to controls (P 0.0001 ). The reduction of HLA class I expression in adenomas was related to the grade of dysplasia of the adenomas. HLA class I expression of norm al appearing mucosa was decreased in 76% of patients with adenoma (P < 0.0001) and in 54% of patients with history of adenoma (P < 0.005) co mpared to normal controls. These changes were antigen specific, inasmu ch as the expression of carcinoembryonic antigen, a surface antigen, w as not affected. Our findings suggest that reduced HLA class I express ion is an early event in the cell transformation process from normal t o neoplastic state, preceding in many cases the onset of histological changes. HLA class I could be potentially used as a premalignant marke r in the colon.