Exome Sequencing with Validations and Expression of p16/CDKN2A Shows no Association with HPV in Oral Cancers.

PURPOSE: Despite many studies attributing HPV infection to oropharyngeal tumorigenesis, its involvement in non-oropharyngeal cancers is ambiguous. We have evaluated the mutation profile of p16 along with protein expression and correlated it with the HPV status in oral cancers. METHODS: Somatic mutations in p16 were studied by exome sequencing (n=25) and validated by Sequenom Mass spectrometry (n=50).  Expression of p16 was studied by immunohistochemistry (IHC) and correlated with HPV16/18 status evaluated by PCR, and IHC (n=221) in oral cancers. RESULTS: Out of 25 oral cancer patients' samples sequenced by Exome sequencing, p16 mutations were found in 4 samples (16%). All the p16 mutations were identified in patients with cancers in the site of gingivobuccal complex and not tongue subsite. All the 4 patients with p16 mutations had failed treatment, and showed a significantly poor disease-free survival. Insilico analysis of the types of p16 mutations showed mutated, truncated p16 protein having an increased intrinsic disorder, and all the mutations involved truncation post arginine. Validation of the p16 mutations by mass spectrometry showed 8/50 (16%) of patients harbouring pArg80Ter mutation, of which 7/8 (87.5%) had failed treatment.  Overexpression of p16 in >70% of the tumour cells was found in 21.4% (26/121) OSCC patients, 6.75% (5/74) OPML patients and p16 expression was significantly correlated (p=0.001; χ2 = 25.601) to the grade. All the samples were studied for HPV presence by PCR and IHC. We found that none of the p16 positive tumours showing expression in >70% of the tumour cells harbored HPV both by PCR as well as IHC. CONCLUSION: Our study emphasises the importance of p16 in oral cancers, and shows that oral cancer is not HPV associated and p16 expression is not a surrogate marker for HPV.

Dental caries vaccine - a possible option?

Dental caries is an irreversible microbial disease of the calcified tissues of the teeth and it has a multifactorial origin. In India, the dental caries prevalence in 35-44 year olds was reported to be 80-95% in a DCI survey. Among the elderly in the 65-74 years age group, the DCI survey reported the caries prevalence to be about 70%, while the present survey reported it to be 51- 95% in various states. Surveys which were done on school children in India showed a carie prevalence of approximately 58%.Among the U.S. population, a survey showed an incidence of 93.8% in adults with either past or present coronal caries and an incidence of 45.3% in children 23. In countries like Brazil and China, it is reaching epidemic proportions. Thus, more effective public-health measures are needed to combat dental caries. Mutans streptococci is one of the main microorganisms which are associated with the aetiology of dental caries. Preclinical studies of immunological interventions have shown that the disease can be interrupted. Clinical trials have indicated that a mucosal immune response to Streptococcus mutans crucial antigens can influence the pathogenesis of dental caries. The dental caries vaccine, when it is used in appropriate individuals at the appropriate time, can reduce the reemergence of the disease.