Physical status of HPV types 16 and 18 in topographically different areas of genital tumours and in paired tumour-free mucosa

Abstract

HPV16 and HPV18 integration into host cell DNA contributes to malignant transformation. Viral physical status was compared among samples from different tumour areas, and from tumour and paired non-lesional adjacent epithelium, in order to evaluate the levels of HPV integration that could account for local recurrences. Fifty-nine surgical biopsies were collected from 24 women with HPV16 and/or HPV18-associated genital tumours, including 3 preinvasive and 21 invasive lesions. HPV integration was analysed by type-specific and multiplex PCRs for E6, E1 and E2 sequences. Nine tumours contained HPV16, 1 HPV18 and 14 both viruses. Intra-tumour heterogeneity occurred in 3 of the 10 tumours with multiple sampling (30%), including different HPV16 physical forms between core and periphery in 2 cases, and different type of HPV infection in 1 case. Almost all tumours contained integrated forms of either HPV16 and/or HPV18. Analysis of the 15 tumour-free tissues displayed 11 HPV-positive (73%) and 4 HPV-negative tissues. HPV16 was pure integrated in 1 case, mixed in 1 and episomal in 8, whereas HPV18 was integrated in all 6 positive tissues (100%). When compared to the corresponding tumour, the positive control mucosa contained the same HPV type and the same physical status as the tumour in 6 cases, whereas 5 samples contained different HPV16 physical forms, episomal DNA being more frequent than in the lesion. These data showing the presence of high-risk HPV integrated forms in normal mucosa, especially in HPV18-positive cases, indicate that the research of viral integration in the adjacent tumour tissues may be a valuable tool in assessing risk factors for local recurrences.