Detection of integration status of human papillomavirus 16 in cervical precancerous lesions

Abstract

To investigate the prevalence of integration of human papillomavirus 16 (HPV16) DNA into the host genome in cervical squamous intraepithelial lesions (SIL). Multiplex PCR was used to detect the HPV/HPV16 infection and integration status of HPV16 in the surplus cells from liquid-based cytological samples from 108 patients with cervical cancer precursor lesions. Consensus primers GP5+/GP6+ were used to amplify a 150 bp long fragment in the conserved region of the HPV L1 gene so as to detect the presence pf HPV. Scion Image 4.0 electrophoresis image analysis soft was used to calculate the E2/E6 ratio so as to evaluate the episomal and integrated status of HPV16 infection: in episomal form, both targets should be equivalent, and in integrated form, E2 gene would be absent, while in mixed form of episomal/integrated mixed form, the copy number of E2 would be less than that of E6. Sixty-two out of the 108 patients (57.41%) had HPV infection. HPV16 were found in 32 of the 108 samples (29.63%). Among the 32 cases HPV16 DNA was exclusively episomal in 15 cases (46.88%), concomitant in 13 cases (40.62%), and integrated in 4 cases (12.50%). The prevalence of integrated and/or concomitant forms of HPV-16 DNA increased with progression of cervical disease. The prevalence of integrated form was 54.55% in the patients of CIN3 type, 50.00% in CIN2 type, 28.07% in CIN1 type, and 11.54% in the inflammatory type with significant differences between any 2 groups (all P < 0.01). HPV16 integration into the host genome is already present in some of CIN lesions. The multiplex PCR estimation of the HPV L1, HPV16 E2, E6 genes and E2/E6 ratio could be a simple method for detecting HPV/HPV16 infection and its integration status in liquid-based residual samples. It would be a helpful complementary tool for cytological screening to identify those patients at high risk of developing high-grade squamous intraepithelial lesions and cervical cancer.