Chromosome 17p allelic loss in colorectal carcinoma. Clinical significance

D. M. Takanishi Jr, I. Angriman, M. L. Yaremko, A. Montag, C. A. Westbrook and F. Michelassi
Department of Surgery, University of Chicago, Ill., USA.

OBJECTIVE: To correlate allelic losses on chromosomes 5q, 8p, 17p, and 18q in colorectal adenocarcinomas with histopathologic features of known prognostic significance. DESIGN: DNA was extracted from paired samples of 56 fresh-frozen colorectal adenocarcinomas (one classified as Dukes' stage A, 22 as Dukes' stage B, 27 as Dukes' stage C, and six as Dukes'stage D) and adjacent normal mucosa. SETTING: Specimens were resected at the University of Chicago (Ill) and the University of Padova (Italy) in 1991. PATIENTS: Samples were obtained from consecutive patients. INTERVENTIONS: Chromosomes 5q, 8p, 17p, and 18q were studied for loss of heterozygosity by means of Southern hybridization blot analysis of restriction fragment length polymorphisms, and the results were correlated with pathologic tumor stage, degree of differentiation, and lymphatic and/or vascular microinvasion. RESULTS: Chromosomes 17p and 18q exhibited the highest frequency of loss of heterozygosity (40.6% and 48.8%, respectively). Most of the allelic losses were found in advanced tumors (60% in Dukes' stages C and D combined). A statistically significant correlation was found between loss of heterozygosity on chromosome 17p and the presence of lymphatic and/or vascular microinvasion (P < .01, Fisher's Exact Test). CONCLUSIONS: There was a significant correlation between loss of heterozygosity on chromosome 17p and the presence of lymphatic and/or vascular microinvasion in colorectal adenocarcinoma, a known stage-independent negative prognostic risk factor. Detection of loss of heterozygosity on chromosome 17p may identify a group of patients who may benefit from more aggressive surgical and/or early adjuvant therapy.