AimsHoxB9, as a Hox family member, is known to play important roles in embryonic development. Recent studies showed that HoxB9 is engaged in cancer progression. However, the role of Hoxb9 in lung adenocarcinoma is unknown. The purpose of this study is to investigate the expression and prognostic value of HoxB9 in patients with lung adenocarcinoma. Methods and resultsThe localization and expression of HoxB9 in lung adenocarcinoma were examined byimmunohistochemistry. The correlation between HoxB9 expression levels with patient survival was assessed by Kaplan-Meier analysis. The epithelial-mesenchymal transition (EMT) markers and migratory ability were evaluated in HoxB9 up- and down-regulated H1299 lung adenocarcinoma cells. HoxB9 was found to be localized predominantly in the cell nuclei and expressed in 21.3% of lung adenocarcinomas. Asignificant increase in HoxB9 intensity in the highstage of lung adenocarcinoma was observed (P<0.01). Increased expression of HoxB9 was related to T classification, more lymph node metastasis and a shorter patient overall survival (P<0.05). However, the expression level of HoxB9 was not correlated with age and gender. Functionally, HoxB9 up-regulated EMT-related molecules and promoted cell migration in H1299 cells. ConclusionHigh expression of HoxB9 is a prognostic marker for lung adenocarcinoma patients.