Prognostic value of the Hippo signaling pathway in oral squamous cell carcinoma: a systematic review and meta-analysis

Background: This systematic review and meta-analysis evaluated the prognostic value of Hippo signaling pathway biomarkers in oral squamous cell carcinoma. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, electronic database searches identified 17 eligible studies involving 1,194 patients. Associations between the immunohistochemical expression of Hippo pathway effectors, primarily YAP and TAZ, and clinicopathological characteristics were assessed. Meta-analyses using random-effects models estimated pooled hazard ratios for overall survival. Results: Predominantly nuclear expression of YAP and TAZ was consistently associated with adverse clinicopathological features, including advanced clinical stage, lymph node metastasis, and poorer histological differentiation. Meta-analysis demonstrated that YAP overexpression was associated with worse overall survival (hazard ratio, 1.918; 95% confidence interval, 1.036 to 3.549; p = 0.038). TAZ overexpression was similarly associated with poorer overall survival (hazard ratio, 2.845; 95% confidence interval, 1.682 to 4.811; p < 0.001). Although substantial between-study heterogeneity was observed, the direction of the prognostic association remained consistent across studies. Conclusions: Increased nuclear expression of YAP and TAZ is consistently associated with more aggressive disease and poorer overall survival in oral squamous cell carcinoma. These findings support the prognostic value of Hippo pathway biomarkers, although methodological heterogeneity warrants cautious interpretation.