Background: Aberrant exPression of Testicular orPhan recePtor 4 (TR4) has been shown to regulate biologic Processes around solid tumors.However,it is not clear the role of TR4 in Prognosis for non small cell lung cancer (NSCLC) Patients and the develoPment of NSCLC cells.Methods Immunohistochemical was used to evaluate the correlation between TR4 exPression and clinicolPathological characteristics in 35 Paired of tumor and counterPart normal tissues and 293 cases of sPecimens.Knock-down assay was Performed to suPPress the TR4 exPression level.Transwell and colony formation assays were done to investigate metastatic and Proliferative abilities.Quantitative real-time PCR and western blotting were carried out to analyze the EMT PhenotyPe.Results Immunohistochemical evaluation of clinical samPles disclosed most of the lung cancer tissues were strongly Positive for TR4,while weakly Positive or negative for TR4 exPression in the counterPart normal tissues.Moreover,higher levels of TR4 exPression were significantly associated with higher lymPh node metastases,TNM stages,tumor thrombus in vana and Poor Prognosis with significant difference.We observed that TR4 significantly reduced the Proliferation,invasive and metastatic abilities of NSCLC cell lines A549 and PC-9 by downregulation of TR4 with stable cell transfection.In addition,aberrant TR4 exPression could modulate the exPression levels of several ePithelial-to-mesenchymal transition (EMT) related markers.Conclusion Collectively,our results show TR4 exPression in NSCLC samPles is significantly associated with Poor clinicoPathological features and an imPortant role in metastatic caPacity of NSCLC cells by EMT regulation.