Abstract 3073: EphrinA1 inhibits non small cell lung cancer (NSCLC) tumor growth via induction of miRNA-122

Introduction: Ephrin-A1 ligand exerts anti-oncogeneic effect in NSCLC tumor cells through activation and down regulation of the EphA2 receptor. Alteration in their expression levels is associated with aggressive tumor growth. The underlying mechanisms for altered expression of Ephrin-A1 and EphA2 receptor are yet to be defined. MicroRNAs (miR) are small non-coding RNAs play a key role in tumorogenesis. MiR-122 directly targets Bcl-w which harbours a putative miR-122 binding site in its 3′-UTR. However, if EphrinA1 induces miR-122 expression in NSCLC is not known. Here we demonstrate a novel mechanism of EphrinA1 mediated miR-122 signalling in the inhibition of NSCLC growth. Methods: NSCLC cell lines (A-549 and H-23) were activated with Ephrin-A1 over time (3 hr, 6hr, 12hr and 24 hr) and miR-122 expression was measured by Real-time PCR and In situ hybridization. Furthermore, in order to understand the underlying mechanisms EphrinA-1 mediated signalling, Bach-1 and Bcl-w protein expression were studied through Western blotting analysis. In addition, Tumor growth and Cell migration studies were performed in Ephrin-A1 activated and premiR-122 transfected NSCLC cells. Results: The data from this study demonstrates that Ephrin-A1 activation of NSCLC enhanced Bach-1 and miR-122 expression over time. When NSCLC transfected with pre-miR-122, we noticed a significant down-regulation of Bcl-w gene and protein expression, suggesting miR-122 specifically targets to anti-apoptotic gene Bcl-w and induced apoptosis in NSCLC. In situ hybridization demonstrated strong signals for miR-122 in EphrinA1 activated NSCLC cells as compared to control cells. Furthermore, knock down of Bach-1 gene expression using siRNA, showed significant down-regulation of miR-122, suggesting Ephrin-A1 mediated signalling is regulated by the transcription factor Bach-1 via miR-122 in NSCLC. In addition, this was confirmed by transfection of NSCLC by premiR-122 that inhibited tumor growth and migration of NSCLC cells. Conclusions: Our study suggests that Ephrin-A1 mediated signalling is regulated by the transcription factor Bach-1 via miR-122 expression. MiR-122 targets the anti-apoptotic gene Bcl-w and triggers apoptosis in NSCLC cells. The present study provides a new insight into the complex regulating pathways of Ephrin-A1/Eph receptor, and also understanding the direct role of miRNA-122 in Ephrin-A1 mediated signalling pathway that may lead to new therapeutic strategies for lung adenocarcinoma