Immunohistochemical expression of p16 protein in oral squamous cell carcinoma and lichen planus

Epithelial carcinogenesis is a multistep process. Specific genetic events lead to malignant transformation of oral epithelium. Oral squamous cell carcinoma (OSCC) may be preceded by potentially malignant lesions such as oral lichen planus (OLP). The p16 protein functions as a negative regulator of the cell cycle progression. Altered pattern of p16 serves as a biomarker for oral mucosal dysplasia and malignant growth. The purpose of this study was to evaluate p16 expression in OSCC and OLP to determine whether it can be a useful marker for early detection of carcinogenesis. We examined p16 expression in 45 OSCCs (15 grade I, 15 grade II, and 15 grade III), 15 OLPs without dysplasia, and 8 normal mucosal specimens with immunohistochemistry. p16 was interpreted as positive if more than 70% of tumor cells showed brown nuclear and cytoplasmic staining. All of the OSCC and control group samples showed negative immunoreactivity, whereas 26.7% of OLP samples were positive for p16. Our findings suggest that p16 expression could not be used as a helpful marker for detection of development toward malignancy in OLP samples.