Role of tumor suppressor protein p16 in patients with oral lichen planus

Oral lichen planus (OLP), is considered premalignant condition. This study tried to investigate the possibility of malignant transformation in OLP patients, by measuring the level of tumor suppressor protein p16INK4A, which is a product of the cyclin-dependent kinase inhibitor 2 (CDK2). CDK inhibitors may be responsible for maintenance of cell cycle. An imbalance in the cell cycle regulatory pathway involving p16/pRb may lead to unrestricted proliferation and tumorigenesis.40 patients with OLP underwent biopsy. Two control groups were included in this research, 13 healthy persons and 12 patients with oral squamous cell carcinoma (OSCC). All tissue samples were treated immunohistochemically using avidin-biotin peroxidase complex method.The number of patients with p16 positive cells was significantly higher in OLP (72.5%) in comparison to OSCC (33.33%). Although the prevalence of patients with p16 positive cells in OSCC was low, they expressed the highest percentage of p16 positive keratinocytes. Staining intensity of cytoplasm was also higher in p16 positive keratinocytes of OSCC in comparison to OLP.These results suggest that inactivation of p16 is an early detectable event in oral tumorigenesis. P16 expression could also be connected with tumor grading and may be useful marker in oral tumor progression.