Yes associated protein is a poor prognostic factor in well-differentiated lung adenocarcinoma

The Hippo pathway is a highly conserved potent regulator of cell growth and apoptosis including large tumor suppressor (LATS) and Yes-associated protein (YAP). LATS has been regarded as a tumor suppressor gene and YAP as either of a tumor suppressor gene or an oncogene. We investigated their expression in lung adenocarcinoma. YAP and LATS protein expression was assessed in 167 surgically resected lung adenocarcinomas and compared with clinicopathologic factors. Disease free survival and overall survival were also evaluated. YAP expression was noted in cytoplasm (48 cases; 28.7%), nuclear (34; 20.4%) and both locations (4; 2.4%). The nuclear expression was typically observed in well differentiated adenocarcinoma. LATS was expressed in cytoplasm when its signal is weak. Perinuclear expression of LATS was observed when it is strongly expressed. While cytoplasmic and nuclear YAP expressions were inversely related. In well differentiated adenocarcinoma patients, YAP nuclear expression was related with more frequent relapse. Both of nuclear YAP and LATS expression were more frequently observed in well differentiated adenocarcinoma. Furthermore, YAP expression exhibited more frequent relapse in well differentiated adenocarcinoma group. We suggest that YAP may act as an oncogene and predict poorer prognosis in well differentiated lung adenocarcinoma.