Differentiation of an integrated and episomal HPV-16 DNA using real-time PCR in cervical specimens of women diagnosed with intraepithelial lesions and invasive cervical cancer

Abstract

Summary Persistent high-risk HPV infection, especially HPV-16, is considered to be an important step in the process of cervical carcinogenesis. Integration of viral DNA into the host genome through the destruction of HPV E2 sequences, increases the expression of viral proteins E6 and E7 and their participation in the transformation of cervical cancer. Objective: The aim of this study was to apply real-time PCR (RT-PCR) to assess the prevalence of integrated and episomal HPV-16 DNA and determine viral DNA load in women with cervical intraepithelial lesions and invasive cervical cancer. Material and Methods: A total of 84 women infected with HPV-16, including 44 with LSIL, 7 with HSIL and 33 with invasive cervical cancer, participated in the study. Cervical specimens were collected using the cytobrush. The presence of a sequence of E2 and E6 HPV-16 and human gene RNasy P was detected by quantitative RT-PCR. The viral load presented as the form of the virus genome copy numbers per 1,000 cells. Results: The integrated form of HPV-16 genome was found in 97% of women with cervical cancer. In women with LSIL and HSIL mixed form (simultaneous occurrence of an integrated and episomal form) of the viral genome (84% and 57%, respectively) prevailed. The frequency of the integrated HPV-16 DNA increased with progression of dysplastic lesions of the cervix (p<0.001). Statistically significant differences in average number of copies of the virus in women with LSIL and HSIL compared to patients with cancer (p <0.001) were observed. The highest viral load was detected in women demonstrating an integrated HPV-16 DNA. Conclusions: Quantitative analysis of the sequence of E2 and E6 HPV-16 tested by RT-PCR can be used to determine the degree of integration of the viral genome and quantitative evaluation of viral load in clinical material. It can also serve as an additional parameter defining risk of progression of transformation in the cervix.