Yes-associated protein, a downstream effector of the Hippo signaling pathway, has been linked to progression of non-small-cell lung carcinoma. The aim of this study was to investigate expression of Yes-associated protein in lung adenocarcinoma and squamous cell carcinoma. Associations of Yes-associated protein expression with clinicopathologic parameters, expression of cell cycle-specific markers, and epidermal growth factor receptor gene amplification were also analyzed. In a univariate analysis of the 66 adenocarcinomas, high nuclear expression of Yes-associated protein was significantly correlated with expression of cyclin A and mitogen-activated protein kinase. Multivariate analysis, including age and sex, showed that cyclin A expression was independently correlated with nuclear expression of Yes-associated protein in adenocarcinomas. Furthermore, high nuclear expression of Yes-associated protein was also a significant predictor of epidermal growth factor receptor gene amplification for adenocarcinoma. For the 102 squamous cell carcinomas, univariate analysis revealed that high cytoplasmic expression of Yes-associated protein was correlated with the low pathologic TNM staging (stage I) and histologic grading. Multivariate analysis, including age and sex, showed that cytoplasmic expression of Yes-associated protein was an independent predictor of low pathologic TNM staging. These results indicate that nuclear overexpression of Yes-associated protein contributes to pulmonary adenocarcinoma growth and that high cytoplasmic expression of Yes-associated protein is an independent predictor of low pathologic TNM staging and histologic grading. The differential effects of Yes-associated protein expression patterns in adenocarcinomas and squamous cell carcinomas suggest that Yes-associated protein may play important roles in different pathways in distinct tumor subtypes. These observations may, therefore, lead to new perspectives on therapeutic targeting of these tumor types.
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