Sixty-four colorectal carcinomas were evaluated for allelic loss of chromosomes 17p and 5q, as well as point mutation of the p53 tumor suppressor gene. Allelic loss of chromosomes 5q and 17p were found to be weakly associated, whereas point mutation of the p53 gene was found to be more strongly associated with chromosome 5q allelic loss. Carcinomas in which both alleles of p53 had been inactivated showed a strong association with allelic loss of chromosome 5q (p=2.3x10(-4)), a relationship confirmed by an association between allelic loss of chromosome 5q and immunostaining with the p53 monoclonal antibody pAb 1801 (p=9.4x10(-3)). In contrast, allelic loss of chromosome 5q was not associated with either the activation of the c-Ki-ras proto-oncogene, or with DNA aneuploidy. The association between allelic loss of chromosome 5q and the inactivation of both alleles of p53 was significantly associated with tumor dissemination (p=7.2x10(-3)). These results suggest that dissemination of colorectal neoplasia may require the coordinate inactivation of at least two suppressor genes.

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