Quantitative polymerase chain reaction-based detection of HPV 16 E6 and E7 DNA in oral squamous cell carcinoma

Although human papillomavirus (HPV) is considered as a causative factor in oral squamous cell carcinoma (OSCCs), its pathogenetic role is not well established. Moreover, a limited number of studies have compared the techniques of detecting the HPV infection in OSCC. This study aimed at the detection of HPV 16 E6 and E7 DNA in OSCC by quantitative polymerase chain reaction (qPCR) technique.

This retrospective study included 297 tissue sections obtained from histopathologically confirmed OSCC patients. The classification of tumors as poorly differentiated, moderately differentiated and well differentiated was performed by H&E staining following the WHO criteria for OSCC. The presence of HPV infection was detected by p16^INK4A expression, conventional PCR technique, HPV 16 E6, and E7 by qPCR and flow cytometry. All statistical analysis was performed using MedCalc software v.16.4.3. P < 0.05 is considered as statistically significant.

Of 297 samples, 128 samples were found to be HPV-positive by p16. Of total 128 HPV-positive samples, PCR, E6, and E7 qPCR were positive in 19, 97, and 98 samples, respectively. qPCR techniques were found highly significant in the detection of moderately differentiated (P < 0.0001) and widely differentiated (P < 0.0001) cases. The positivity of E6 qPCR increased as the p16 expression increased. A significant variation in E6 DNA copies was observed in different grades of p16 expression (P < 0.0001). However, overall E7 (5.4 × 10⁵ copies/μL) DNA copies were higher than E6 (7.7 × 10³ copies/μL).

qPCR detection of HPV infection is a fast, reliable, and accurate technique gives valuable information about the infection status in terms of viral load.