A HIGH-FREQUENCY OF HUMAN PAPILLOMAVIRUS DNA-SEQUENCES IN CERVICAL CARCINOMAS OF INDIAN WOMEN AS REVEALED BY SOUTHERN BLOT HYBRIDIZATION AND POLYMERASE CHAIN-REACTION

Ninety-six colposcopically directed biopsies from squamous epithelial carcinoma of the uterine cervix and 22 age-matched normal control biop sy specimens were examined by both Southern blot hybridization and pol ymerase chain reaction (PCR) for the presence of different human papil lomavirus (HPV) DNA types. Cancer of the uterine cervix, which is the most common malignant disease in Indian women, showed a high frequency (98%) of HPV as compared to those reported from other parts of the wo rld. HPV type 16 was found to be the dominant (64%) type while the fre quency of HPV type 18 was very low (3%). On individual typing of HPV, no biopsy was found to contain any other known HPV types under stringe nt conditions of hybridization except a single case of HPV type 11. On ly one case of double infection with HPV types 16 and 18 was recorded. Under low stringency conditions of hybridization with a mixed probe o f HPV types 16 and 18, 29 additional biopsies were found to be positiv e. Southern blot hybridization alone detected HPV DNA in 92% of the ca ses but none in the controls. By PCR, six (6.25%) more cases and four (18.18%) healthy women were found to be positive for HPVs. Analysis of the physical state of HPV 16 indicated integration in about 70% of ca rcinoma cases while 30% of them were in episomal form. The findings su ggest that infection with HPV is an important etiologic factor for the development of cervical cancer, that a number of such tumours may ari se without HPV infection, and that integration of the viral DNA into h ost genome is not always essential for malignant progression. Furtherm ore, the use of PCR provides an effective complementation of Southern blot hybridization for meaningful epidemiological studies of HPV infec tion.