Study of p53 Mutation and Protein Expression in HPV Typed Uterine Cervical Cancer

Bang, Namchul; Lee, Seonkyung; Lee, Juhee; Jee, Sunggil; Kim, Seungbo

Abstract

Oncogenic human papillomavirus(HPV) infection has been implicated in the pathogenesis of cervical carcinoma. The HPV E6 and E7 oncoproteins are thought to play a crucial role in this process by their interactions with the p53 protein and the retinoblastoma suceptibility gene products respectively. The E6 protein binds to and stimulates the degradation of the p53 protein and mutations involving evolutionary conserved regions of the p53 gene also can alter p53 function, so both HPV E6 protein and p53 mutation may play a role in the carcinogenesis of cervical carcinoma. The purposes of this study are to examine the role of p53 gene in relation to the presence of HPV DNA in primary cervical carcinoma and to assess the prognostic value of the p53 gene and HPV infection in surgically treated cervical carcinoma. Formalin fixed, paraffin embeded blocks of 73 cervical carcinomas were evaluated for the status of oncogenic HPV infection by in situ hybridization, and the p53 overexpression by immunohistochemical staining. 43 cases out of 73 cervical carcinomas were evaluated for the HPV type by polymerase chain reaction (PCR)-Southern blot analysis, and the presence of mutations involving exon 4-10 of the p53 gene was examined by polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP), and then, confirmed by direct DNA sequencing. 48 cases of 73 cervical carcinomas showed oncogenic HPV DNA by in situ hybridization and 22 cases showed p53 overexpression by immuno-histochemical staining. There was inverse correlationship between HPV infection and p53 overexpression(p=0.03). HPV infection and p53 overexpression were not significantly correlated with clinicopathological parameters such as age, FIGO stage, histologic type, tumor size, lymph node metastasis, depth of invasion, and tumor differentiation. 32 cases of 43 cervical carcinomas showed oncogenic HPV DNA by PCR-Southern blot analysis. 30 cases(69.8%) of 43 cervical carcinomas showed HPV 16 DNA and 9 cases(20.9%) showed HPV 18 DNA and 11 cases(25.6%) showed no HPV 16/18 DNA. 8 cases of 43 cervical carcinomas showed p53 gene mutation in PCR-SSCP analysis. 7 cases of 8 mutations showed positive p53 overexpression and another 1 case showed negative p53 overexpression. 4 cases of 8 mutations had no HPV 16/18 infection and another 4 cases had HPV 16 and/or 18 infection. There was no significant correlation between p53 mutation and HPV infection. In 8 cases showing mutation, 4 cases showed point mutation, 3 cases showed frame shift mutation, and another 1 case showed deletion from codon 125 to 132. p53 mutations were located at exon 4, 5, 6, 7, and 8, highly conserved region. Oncogenic HPV DNA can be identified in most cervical carcinomas, and mutations involving highly conserved regions of p53 gene, although infrequent in cervical cancer, occur preferentially in tumors without HPV infection but indenpendently. Although HPV infection and p53 overexpression shows no prognostic values in our study, further investigation is required for clarifyng its prognostic value in gynecologic malignancies.