A Study on the Loss of Heterozygosity of the p53 Gene in Primary Uterine Cervical Carcinomas

Kim, Jin Woo; Lee, Chun Geun; Sohn, Yeo Won; Min, Hong Ki; Han, Su Mi; Cho, Eun Young; Kim, Kyung Sook; Lee, Joon Mo; Namkoong, Sung Eun

Abstract

PURPOSE: Allelic deletion of p53 tumor suppressor gene have been observed frequently in a variety of human tumors. These losses are believed to contribute to the development of human cancers. But the loss of heterozygosity (LOH) data on chromosome 17p are rare and controversial with respect to cervical carcinomas. So, we tried to elucidate the frequency of p53 locus LOH in primary cervical carcinoma and compared the LOH data with clinicopathological parameters.
MATERIALS AND METHODS
In order to detect LOH within one of the well-known tumor suppressor gene, p53, three intragenic polymorphisms (exon 1, exon 4, and intron 6) and one microsatellite distal to the p53 gene (D17S5) were examined. Paired DNA samples from 55 primary uterine cervical carcinomas and normal bloods were studied for the chromosomal allelic loss of p53 gene locus by polymerase chain reaction (PCR), the presence of human papilloma virus (HPV), and the presence of p53 gene point mutation by PCR-single conformation polymorphism (SSCP) analysis. And the relationships between allelic losses of this gene and conventional clinicopathological parameters were evaluated.
RESULTS
We could increase the heterozygosity of the p53 gene up to 1 (100%). The observed allelic loss rate of the p53 locus in informative cases was 5.5% (3/55) and the observed allelic loss rate of the D17S5 locus in informative cases was 8.7% (4/46) . Only one of the four patients with LOH at the D17S5 locus showed a concomittant allelic loss of the p53 gene. The overall LOH incidence of the chromosomal region comprising 17p13.1 (p53) to 17p13.3 (D13S5) was 10.9% (6/55). All the samples contained at least one of the oncogenic HPV type 16 and/or 18 sequences. No shifted bands were observed in the PCR-SSCP analysis of the p53 gene. The LOH of the p53 gene was not related to other parameters including clinical stage, histological type, and degree of differentiation.
CONCLUSION
Concerning with the results above, we conclude that the allelic imbalance of the p53 gene itself is not implicated as a major contributing factor in the malignant transformation or the tumor progression in HPV-positive cervical cancers. Another putative tumor suppressor gene which has more important function than p53 gene in cervical carcinogenesis might exist between these two loci [p53 (17p13.1) and D17S5 (17p13.3)].