GENETIC ALTERATIONS IN HUMAN COLORECTAL T UMORS - DELETIONS AT CHROMOSOME-1 SHORT ARM AN EARLY EVENT

Cytogenetic anomalies described in cole-rectal tumors are numerous. De spite the complexity and the number of the anomalies observed, a combi ned study of their frequency and of the stage of prognosis of the tumo rs suggests that the evolution from colonic adenoma to carcinoma often follows a sequence of events comprising a 5q15-22 deletion (DCC), and a 17p deletion (P53). It even seems likely that in many cases, these events are not constant and that others might lead to the same phenoty pic transformation. Chromosome 1 involvement in structural rearrangeme nts has been demonstrated in numerous forms of cancers, malignant bloo d disorders and in solid tumors. In colorectal adenocarcinoma anomalie s have been described on short and/or long amis. In a case of adenoma, vith mild dysplasia a deletion of the distal part of the short arm of chromosome 1 rr as observed as an isolated cytogenetic anomaly suggest ing it would be an early, perhaps triggering, event for the tumour dev elopment. A cytogenetic study in a series of colo-rectal tumours, rese archs on loss heterozygoty and microsatellite instability lead to cons ider deletions at chromosome 1p as an early event in human colorectal tumourigenesis.