Identification of human papillomavirus type 16 integration sites in high-grade precancerous cervical lesions

Infection with oncogenic human papillomaviruses (HPV) is a prerequisite for the development of cervical cancer. In many cases of cervical cancer and all cervical cancer derived cell lines oncogenic HPV DNA is found to be integrated, indicating the importance of integration in disease development. In this study, 176 HPV 16 positive precancerous cervical lesions were analyzed for the physical state of viral genome to determine the sites of integration into a host cell DNA and to evaluate the incidence of the integration in different stages of cervical lesions.

The detection of integrated papillomavirus sequences (DIPS) method in combination with the amplification by polymerase chain reaction (PCR) of E1/E2 region was used to identify the physical state of HPV 16 genome. The site of integration within a host cell genome was determined by sequencing of unusual sized DIPS amplicons.

The combined results of DIPS and E1/E2 PCR revealed the integration of HPV 16 DNA in 7.4% samples. The integration was found only in high grade cervical lesions indicating that it is a late event in disease progression. Sequencing of 11 DIPS amplicons revealed HPV DNA from 6 samples (54.5%) to be integrated in cellular genes (VMP1, PVRL1, CHERP, CEACAM5, AHR, MRF-2) and also 6 (54.5%) within the common fragile sites (CFS).

Although, the HPV integration is known to be a random event, this study indicates that HPV 16 integrates more than by chance within or close to CFSs. As most of the genes affected by HPV 16 integration can be linked with some aspects of tumor formation, this indicates that the site of HPV DNA integration might play a role in the rate and the nature of tumor development.