Genetic alterations in the region of the p53 gene on human chromosome 17 in colorectal cancer]

Most colorectal tumors are characterized, among other genetic alterations, by allele loss of the genes located on the short arm of chromosome 17 (17p13.1), including the p53 suppressor gene. In ovarian and mammary-gland tumors, deletions of another candidate tumor-suppressor gene, located in the 17p13.3 chromosome region, were observed. We analyzed allele losses in the loci of the short arm of chromosome 17 (YNZ22, MCT35.1, and the p53 gene) in colorectal-cancer patients from the former Soviet Union. Tumors with cytogenetic alterations in 17p and/or with a detected loss of heterozygosity at the YNZ22 (D17S30) locus were examined for allele losses in the p53 gene using two polymorphic sites. Different methods revealed alterations on 17p in 24 (48%) out of 50 patients with colorectal carcinomas. In all tumors with an allele loss of the YNZ22 marker (15 out of 44 informative cases), which was detected by means of PCR, allele loss of the p53 gene was found (12 out of 15 informative cases). In 5 out of 13 tumors with cytogenetic alterations in 17p, allele loss of the p53 gene was found, with the YNZ22 marker being unaffected. In one of these tumors, the i(17q) marker was found, and in the remaining four tumors, 17p translocations were detected. In 4 out of 5 tumors with translocations affecting 17p, the t(17;20)(q21;p12) translocation was detected. The informativeness of the screening for 17p translocations, using PCR for the YNZ22 locus, and the reasons for discrepancy between the data of PCR and cytogenetic analyses are discussed.