MOLECULAR ANALYSIS OF RAS ONCOGENES IN CIN-III AND IN STAGE-I AND STAGE-II INVASIVE SQUAMOUS-CELL CARCINOMA OF THE UTERINE CERVIX

Aim-To examine the prevalence of genital type human papilloma virus (H PV) and mutations at codons 12, 13, and 61 in H, Ki, and N-ras in CIN III and early invasive squamous cell carcinomas of the cervix. Methods Prevalence of HPV was examined in 20 CIN III and 20 stage I and II ce rvical carcinomas, using non-isotopic in situ hybridisation (NISH) and solution phase polymerase chain reaction (PCR). In addition, mutation s at codons 12, 13, and 61 were examined in H, Ki, and N-ras in these CIN III and early invasive squamous cell carcinomas, to assess the pre valence of ras gene point mutations and to define where in the pathobi ology of squamous cell carcinoma such events occur. A non-isotopic PCR /RFLP assay was used to define these mutations. Results-Of the 20 CIN IIIs examined, 19 contained HPV 16 DNA sequences by PCR and MSH. Dual infection was not uncovered. The 20 early (stage I and Ii) invasive sq uamous cell carcinomas showed predominant HPV 16 positivity (17/20), w ith one case HPV 18 positive, confirmed on PCR and NISH. Activating mu tations were not identified in any of the CIN III cases. Only one stag e I, HPV 16 positive carcinoma showed an activating mutation in H-ras codon 12, which was not present in adjacent normal ectocervical mucosa from the same patient. Conclusions-ras Activation does not appear to occur in conjunction with HPV infection, particularly of HPV 16 infect ed high grade cervical intraepithelial neoplasia, or to occur commonly in early cervical squamous cell carcinoma. The postulated model of HP V linked carcinogenesis suggests malfunctional control of viral transc ription as a necessary component of neoplastic progression. It is also clear that host gene alterations are equally necessary for HPV linked carcinogenesis to occur.