The Cell Cycle Regulatory Proteins p16, CDK4, and PTEN Are Unsuitable as Biomarkers in Oral Melanocytic Lesions.

Abstract

Background: Melanocytic neoplasms are rare in the oral cavity and represent a diagnostic challenge due to the overlap between benign and malignant lesions. However, their pathogenesis is not fully elucidated. The aim of this study was to evaluate the expression of the cell cycle-related proteins p16, CDK4, and PTEN in oral melanocytic nevi and melanomas.

Methods: A total of 42 cases of melanocytic nevi and five cases of melanoma underwent immunohistochemical analysis. Cases were scored as 0, 1 (< 5% of positive cells), 2 (6%-50% of positive cells), and 3 (> 50% of positive cells). Statistical significance was set at p ≤ 0.05.

Results: Two cases of melanocytic nevi were totally negative for p16 and 95.2% of cases scored 1. For CDK4, 47.6% of the cases scored 2 and 52.4% scored 3. For PTEN, 97.6% of the cases scored 3 and only one case showed a score of 2. All melanoma cases were classified with a score of 2 for p16, and for CDK4 and PTEN, all cases exhibited a score of 3. PTEN and CDK4 were higher expressed when compared to p16 both in melanocytic nevi and melanomas (p < 0.001), and melanocytic nevi showed low expression of p16 when compared to melanomas (p < 0.0001).

Conclusion: The findings suggest that these cell cycle-related proteins are not useful biomarkers in melanocytic lesions of the oral mucosa and support the apparent biological distinction between oral and cutaneous lesions.