Immunohistochemical Evaluation of Yes-associated protein1 (YAP1) Expression in Oral Leukoplakia and Squamous Cell Carcinoma: Implications for Prognosis

Abstract

Background: Oral Squamous Cell Carcinoma (OSCC), often preceded by epithelial dysplasia, is a prevalent head and neck malignancy. Yes-associated protein1 (YAP1), a key effector of the Hippo pathway, functions as an oncogene promoting cell proliferation and tumorigenesis. Elevated YAP1 expression has been linked to poor prognosis in OSCC. This study investigates the immunohistochemical expression of YAP1 in normal oral mucosa, epithelial dysplasia, and OSCC to clarify its role in oral carcinogenesis.

Aims and objectives: The present study aims to evaluate the immuno-expression of YAP1 in normal oral mucosa, epithelial dysplasia, and OSCC, with the objective of elucidating its role in tumor progression by correlating expression patterns across these groups.

Methodology: Tissue samples from normal oral mucosa (n=9), epithelial dysplasia (n=9), and OSCC (n=9) were analyzed for YAP1 expression using chromogenic immunohistochemistry. Staining intensity and localization were compared across groups, and statistical significance was assessed via Chi-square test.

Results: YAP1 expression significantly increased from normal mucosa to dysplasia and OSCC (p=0.001). Normal tissues predominantly showed absent or weak cytoplasmic staining, whereas dysplastic lesions exhibited mixed weak cytoplasmic and focal nuclear staining. OSCC samples demonstrated strong cytoplasmic staining in over 50% of cells, with notable nuclear localization. This progressive increase in YAP1 expression and altered subcellular distribution correlates with lesion severity, suggesting dysregulated YAP1 activity during malignant transformation.

Conclusion: The findings support YAP1 as a potential biomarker for the malignant progression of Oral Epithelial Dysplasia to OSCC. Enhanced YAP1 expression and nuclear localization may reflect its oncogenic role in oral carcinogenesis. Further studies with larger cohorts and mechanistic analyses are warranted to validate YAP1's prognostic utility and explore its potential as a therapeutic target in OSCC.

Keywords: Leukoplakia; Oral; Squamous Cell Carcinoma of Head and Neck; YAP1-Signaling Proteins.