High expression of P21-activated kinase 5 protein is associated with poor survival in gastric cancer.

P21-activated kinase 5 (PAK5), also termed PAK7, is one of the six members of the PAK family of serine/threonine kinases, which are downstream effectors in several cancer signaling pathways. PAK5 promotes neural outgrowth, contributes to microtubule stability and induces resistance to apoptosis. However, the clinical importance of PAK5 in gastric cancer has not been comprehensively investigated. In the present study, PAK5 expression was evaluated in gastric cancer tissue samples. Furthermore, the associations between high expression of PAK5, and clinicopathological features and prognosis were examined. PAK5 expression in primary gastric cancer specimens resected from 279 patients who underwent gastrectomy at the Tokyo Medical and Dental University Hospital was evaluated using immunohistochemistry. Of the 279 patients, 44 (15.8%) exhibited high PAK5 expression, which was significantly associated with the differentiated pathological type (differentiated vs. undifferentiated; P<0.001), depth of tumor invasion (T1 vs. T2-T4; P<0.001), lymph node metastasis (N0 vs. N1-N3; P<0.001), presence of distant metastasis or recurrence (present vs. absent; P=0.038), advanced tumor stage (I vs. II-IV; P=0.001) and worse disease-specific survival (P=0.013). In stage I-III disease, 38/254 (15.0%) patients exhibited high PAK5 expression, and high expression of PAK5 was significantly associated with relapse-free interval (P=0.044). PAK5 may serve an important role in tumor progression and influence the outcome of patients with gastric cancer.