p16 and p53 in HPV-positive versus HPV-negative oral squamous cell carcinoma: do pathways differ?

p16 overexpression and wild-type p53 expression are associated with human papilloma virus (HPV) in cervical and oropharyngeal cancer. Role of HPV-related carcinogenesis in the etiology of oral squamous cell carcinoma (OSCC) is still vague in Indian population. We aimed to explore the expression pattern of p16 and p53 in HPV-positive and HPV-negative OSCC to elicit differences, if any. Further their effect on survival of patients was studied.

Thirty-one consecutive HPV-positive as well as 31 age and sex-matched HPV-negative OSCC cases from a case series of 369 histologically diagnosed cases of OSCC were included in this study. HPV was detected by two methods, viz. real-time PCR and conventional PCR in biopsy samples. p16 and p53 protein expression was assessed by immunohistochemistry, and p16 mRNA expression was quantified with real-time PCR using SYBR Green assay.

p16 was expressed in six (19.4%) HPV-positive and in four (12.9%) HPV-negative cases. Overall mutant-type p53 expression in 62 OSCC cases was 54.8%. Out of ten p16-positive cases, eight expressed mutant-type p53 and only two cases expressed wild-type p53. Risk factors including oral tobacco consumption and alcohol were present in all these ten p16-positive cases. Survival of patients was not affected by HPV, p16 and p53 status.

Presence of mutant-type p53 and exposure to tobacco-related risk factors in both HPV-positive and negative cases suggest existence of p53-related carcinogenesis in HPV-positive cases in Indian population.