Testicular orphan nuclear receptor 4-associated protein 16 promotes non-small cell lung carcinoma by activating estrogen receptor β and blocking testicular orphan nuclear receptor 2

The possible involvement of estrogen receptors (ERs) and testicular orphannuclear receptors (TRs) in human non-small cell lung carcinoma (NSCLC) has beensuggested, but their precise roles and their relationship remain largely unknown.This study aimed to investigate whether TR4-associated protein 16 (TRA16) regulatesthe ERβ and TR2 pathways and could be a potential target in NSCLC. We used tissuemicroarrays including NSCLC tissues (n=154) and negative controls (n=14) to examinethe expression of TRA16 and ERβ, and in vitro reporter gene assays, the mammaliantwo-hybrid method and immunoprecipitation in Cos-1 cells to investigate the relationshipsamong TRA16, ERβ and TR2. We found that TRA16 was highly expressed in approximately90% of the NSCLC tissues examined. TRA16 overexpression was significantly associatedwith TNM stage, tumor size, lymph node metastasis, tumor thrombus in vein, tumordifferentiation and prognosis of NSCLC patients, in which TRA16 was shown to bean independent prognostic factor. Introduction of TRA16 into Cos-1 cells enhancedcell proliferation. Co-expression of TRA16 and ERβ in Cos-1 cells using differentreporter gene systems and mammalian two-hybrid approaches revealed that TRA16enhanced ERβ-mediated transcriptional activity. By adopting similar approaches,and immunoprecipitation and immunocytofluorescence assays, we found that TRA16also interacted with TR2, and blocked the TR2 inhibitory effect on ERβ. Our findingsdemonstrate that TRA16 could be a promising diagnostic and prognostic biomarkerin NSCLC, and promotes cancer cell growth through activation of the ERβ pathwayby interacting with ERβ and TR2.