Instability of chromosome 17 and the p53 locus in non-familial colorectal cancer with multiple primary malignancies.

Recently, two different mechanisms of genetic instability have been demonstrated in the carcinogenesis of colorectal cancer. Microsatellite instability is an important genetic event for carcinogenesis in hereditary non-polyposis colorectal cancer, proximal colon cancer, and multiple colorectal carcinoma. To examine the association among chromosomal instability and multiple primary malignancies (MPM) in colorectal cancer, fluorescence in situ hybridization using a chromosome 17-specific probe, p53 cosmid probe, and/or an alpha satellite DNA probe was performed in 184 patients with colorectal cancer. The proportion of aneusomy 17 in MPM was significantly higher than that of single cancers (SC) (46.1+/-8.0% and 39.0+/-10.3%, respectively; p<0.01). Multiple numerical aberrations of chromosome 17 in MPM occurred more often than those of SC (64.3% and 22.9%, respectively; p<0.01). The mean frequency of p53 deletion was also higher in MPM (70.4+/-16.7%) compared with SC (53.4+/-18.1%, p<0.05). The frequency of chromosome 17 translocation was significantly greater in tumors with MPM (4/6; 67%) than in SC (3/23; 13%, p<0.05). The frequency of p53 locus translocation was also significantly greater in tumors with MPM (4/6; 67%) than in SC (0/23; 0%, p<0.01). These results suggested that numerical and structural aberrations of chromosome 17 and the p53 locus are important genetic events associated with carcinogenesis in non-familial colorectal cancer with MPM.