Abnormal expression and mutation of p53 in cervical cancer - A study at protein, RNA and DNA levels

Abstract

Objectives: The objectives of this study are to document the status of p53 expression and mutation in cervical cancer at protein, RNA and DNA-levels and to relate this to the presence of HPV. Materials and methods: Biopsy specimens from one hundred and three squamous cell carcinoma of the cervix and histologically normal ectocervix were analysed. Fresh tissues were extracted for protein, RNA and DNA and flash frozen tissue cryostat sectioned for immunohistochemical staining. HPV DNA status was determined by PCR using L1 consensus primers and typed for HPV 16 and 18 with E6 specific primers. p53 expression was determined at the protein level by Western blotting on protein extracts and at RNA level by Northern blotting. Results: There was no p53 overexpression or mutation detectable in the protein extracts. Three of 65 (4.6%) of the carcinomas were positive for p53 by immunostaining with the polyclonal antibody CM1. Overexpression at the RNA level was detected in 2 of 32 (63%) carcinomas. p53 mutation was screened for by PCR/SSCP (single strand conformation polymorphism) followed by sequencing to define the site of mutation. Two of the cervical cancers (2.0%) showed mutation in p53 in exons 7 or 8. The mutation rate in HPV positive rumours was 1.2% (1/81) and in HPV negative tumours was 52% (1/19). Conclusion: p52 overexpression or mutation does not seem to play a significant role in cervical carcinomas.