Background and Objective:Recent studies proved that P21-activated kinase 1(PAK1) is highly expressed in many kinds of tumor and plays an important role in genesis,development,and metastasis of tumor.We aimed to detect the expression of PAK1 in gastric carcinoma and to analyze its relationship with clinicopathological features and prognosis of gastric carcinoma.Met hods:Tissue microarray and immunohistochemical staining were performed to detect PAK1 in paraffin specimens of 189 gastric carcinomas,54 paracancer tissues,40 lymph nodes and 30 healthy tissues.Clinicopathologic features and follow-up data of the patients were analyzed by the χ2 test and the Kaplan-Meier method.Result s:Positive rate of PAK1 was 73.0% in gastric carcinoma,57.4% in paracancer tissues and 23.3% in healthy controls(χ2 = 29.364,P < 0.05).Expression of PAK1 was significantly correlated with tumor size,tumor differentiation,lymph node metastasis,Lauren classification and invasive depth(all P < 0.05).The positive rate of PAK1 was significantly higher in primary gastric carcinomas than in metastatic lymph nodes(75.0% vs.52.5%,χ2 = 4.381,P < 0.05).Survival analysis using the Kaplan-Meier method showed that the expression of PAK1 was a predictor for poor prognosis of the patients with gastric carcinoma(χ2 = 6.857,P < 0.01).Conclusions:Expression of PAK1 is an early molecular event in the tumorigenesis of gastric carcinoma.It is also closely correlated the development of gastric carcinoma and the patients’ prognosis. Background and Objective: Recent studies demonstrate that P21-activated kinase 1 (PAK1) is highly expressed in many kinds of tumor and plays an important role in genesis, development, and metastasis of tumor. We aim to detect the expression of PAK1 in gastric carcinoma And to analyze its relationship with clinicopathological features and prognosis of gastric carcinoma.Met hods: Tissue microarray and immunohistochemical staining were performed to detect PAK1 in paraffin specimens of 189 gastric carcinomas,54 paracancer tissues,40 lymph nodes and 30 healthy tissues.Clinicopathologic features and Follow-up data of the patients were analyzed by the χ2 test and the Kaplan-Meier method.Result s:Positive rate of PAK1 was 73.0% in gastric carcinoma,57.4% in paracancer tissues and 23.3% in healthy controls(χ2 = 29.364, P < 0.05). Expression of PAK1 was significantly correlated with tumor size, tumor differentiation, lymph node metastasis, Lauren classification and invasive depth (all P < 0.05). The positive The rate of PAK1 was significantly higher in primary gastric carcinomas than in metastatic lymph nodes (75.0% vs. 52.5%, χ2 = 4.381, P < 0.05). Survival analysis using the Kaplan-Meier method showed that the expression of PAK1 was a predictor for The poor prognosis of the patients with gastric carcinoma (χ2 = 6.857, P < 0.01).Conclusions: Expression of PAK1 is an early molecular event in the tumorigenesis of gastric carcinoma.It is also closely correlated the development of gastric carcinoma and the patients’ prognosis. .