Methods: DNA was extracted from formalin fixed paraffin embedded tissues using QIAamp DNA Tissue Kits (Qiagen). The mucosal alpha HPV L1 gene was detected by means of consensus primer pairs utilising nested, seminested and independent Polymerase Chain Reaction (PCR) techniques. The amplified PCR products were further confirmed via automated DNA sequencing approaches. HPV genotyping was carried out utilising SPF-DEIA and SPF10-LiPA methods for alpha HPV L1 gene and the PM-PCR RHA method of identifying beta HPV E1 gene.
Results: The ‘low risk'-alpha HPV type (HPV6) was the most frequently present in 21 out of 60 (35%) samples tested. In other samples, HPV6 co-existed with ‘high risk'-alpha HPV types: 5 samples with HPV16 (8.3%) and one with HPV18 (1.6%). In addition, six samples had simultaneous expression with beta HPVs: two with HPV93, one sample each with HPV23, HPV36, HPV38 and HPV80. Two samples were recognised to contain only HR-alpha HPV types (one each for HPV16 and HPV35) and another two for beta HPV types (HPV15 and HPV76). A Kaplan-Meier survival analysis suggested that HPV positivity, regardless low risk or high risk HPV types, was associated with a poor prognosis for oral carcinoma (p<0.05).
Conclusion: Our results may suggest that HPV positive patients, either high or low risk types, might benefit from more aggressive management. It also may explain why individuals without obvious aetiological factors might be prone to developing aggressive disease. This might prove not only to be of diagnostic use but may support vaccine development for at risk groups. Our work thus far suggests that a subset of oral cancer is associated with HPV.