Head and neck cancer (HNC) is one of the most common malignancies worldwide. Oral squamous cell carcinoma (OSCC) is the sixth most common cancer and malignancy among HNC globally. Northeast India has one of the world’s highest incidences of oral cancer; it is the most common malignancy among head and neck cancers (HNC), accounting for approximately 30%−40%. Tobacco consumption, alcohol use, smokeless tobacco products human papillomavirus (HPV) infection and glutathione S-transferase (GST) gene polymorphisms are the major risk factors for oral cancer, with smoking and alcohol having synergistic effects. HPV infection has been a prime suspect in the aetiology of OSCC due to its morphological association with SCCs and its ability to immortalize oral keratinocytes and bring about transformation of epithelial cells. Further, mitochondrial DNA (mtDNA) alterations are associated with various cancers, suggesting that it may be a critical contributing factor in carcinogenesis. Here, we investigated the association of tobacco–betel quid chewing, HPV infection, GSTM1-GSTT1 genotypes and mitochondrial D-loop mutations with OSCC.
The mutations from matched tissue samples of OSCC patients with control subjects were used for PCR and direct sequencing. PCR-based detection was done for high-risk HPV using a consensus primer Gp5+/Gp6+ and My09/My11 for amplifying HPV L1 gene fragments, and multiplex PCR was done for detection of GSTM1-GSTT1 polymorphism using CYP1A1 as an internal control . DNA from cervical cancer cell lines infected with known HPV types was used as positive controls. PCR products were analyzed by electrophoresis on 2.5%agarose gels stained with ethidium bromide. All possible precautions like sample processing and PCR reaction preparation in separate biosafety cabinet, sterile gloves changing after each batch of reactions, inclusion of negative controls in all PCR reactions, etc. were maintained to minimize contamination.
Our results suggest that the association of tobacco–betel quid chewing, null GST genotypes, HPV infection and mutations can be used as a possible biomarker for early detection and prevention of oral cancer. Furthermore, biochemical and molecular studies are necessary to determine the pathological significance of these associated somatic mutations. The most reliable way to prevent infection with either high-risk or low-risk HPV is by avoiding any skin-to-skin oral, anal or genital contact with another person. Those who are sexually active, long term, mutually monogamous relationship with an uninfected partner are the strategy most likely to prevent HPV infection. PCR must be employed in combination with histological detection for rapid, sensitive and specific detection of HPV, thereby facilitating early therapeutic decisions in suspected and histopathological negative cases, thus providing the clinicians the guidance for choosing an accurate treatment of HPV-infected advanced OSCC cases.