Assessment of p16 Tumour Suppressor Protein Expression In Oral Mucosa of Smokers And Paan Chewers using Immunohistochemistry

Introduction:Environmental factors such as diet, alcohol use, stress, and environmental chemicals are known to elicit epigenetic changes, leading to increased rates of cancers and other diseases. Squamous cell carcinoma of the upper aero digestive tract typically occurs in older patients in their fifth to seventh decade of life and older. Commonly, there is a prolonged history of tobacco exposure and alcohol abuse. The risk of cancer development in this population is both dose‐ and time‐ dependent. Less frequently, patients with little or no exposure to known risk factors develop squamous cell carcinoma of the oral cavity, pharynx, and larynx. The alteration of p16 occurs frequently in human oral cancers. 83% of oral cancer and 60% of the premalignant lesion shows the loss of p16 expression, suggesting that p16 alteration is an early event in oral cancer . [1] Hence an attempt was made to determine a possible correlation between the p 16 expression and habits of smoking and chewing tobacco in patients attending a tertiary health care centre in south India. Methods: This study was conducted in the Department of Oral Medicine and Radiology, Dental College, Trivandrum, for a period of one year with the collaboration of the Division of Cancer Research, Regional Cancer Centre, Trivandrum, India. Patientswith history of various deleterious habits were screened and details regarding the type, duration and frequency were noted.Patients with clinical features suggestive of oral submucuous fibrosis, and associated oral cancer were selected for the study. Normal subjects were selected from patients reporting for removal of third molars. Informed consent was obtained from all the patients. Instituitional ethics committee clearance was also obtained for the study. An incision biopsy of sufficient width and depth to ensure inclusion of connective tissue was taken from the buccal mucosa in OSF patients and from the respective sites in patients with concomitant malignancy. Of the sections cut from formalin fixed, paraffin embedded specimens, one was used for routine hematoxylin and eosin staining and the other was used for immunohistochemistry staining by Avidin and Biotin methods. The immunoreactivity was evaluated and the percentage of cells showing positive nucleus was determined. The habit patterns practiced by the patients and the expression of p 16 in all the three groups were analysed. Results:A total of 61 patients were selected for the study.There were 29 patients diagnosed clinically and histopathologically as having oral submucous fibrosis. Seven patients had oral squamous cell carcinoma.25 normalwere selected for the study of which 20 subjects did not have any habits and 5 were smokers. None of them were alcoholics or paan chewers. In the OSF group all patients had the habit of paanchewing ,either alone or in combination with smoking and alcoholism.When the habits of patients were analyzed, a higher p16 expression was found in patients who practiced betel quid chewing either alone or in combination with smoking and alcoholism, when compared to those without habits.