Oncogenic Role of MiR-20b is Mediated by a Positive Feedback Loop of Wnt//β-Catenin Pathway in Non-Small Cell Lung Cancer

Background: MicroRNAs (miRNAs) are a kind of endogenous non-encoding single stranded RNA which is able to regulate genes expression by targeting the 3’-untranslated region (UTR) and play an important role in many biological and pathological processes, such as inflammation and cancer. Methods: The expression levels of miRNAs and its regulated genes were evaluated by qPCR and Western-blot analysis respectively. The proliferation of cells was calculated by growth curve and colony formation. The migration and invasion assay was determined by trans-well study. Mouse xenograft model was applied for in vivo study. Findings: In this study, we found that miR-20b significantly increased in human non-small cell lung cancer (NSCLC) cell lines and patients’ tissues, suggesting that it possesses a carcinogenic role in lung cancer. It promoted the proliferation, migration and invasion of NSCLC cells by targeting and down-regulating the expression of APC which is a negative regulator of the canonical Wnt signaling pathway. Specifically, as the downstream of miR-20b, the activation of Wnt signaling could increases the transcription of miR-20b. Therefore, miR-20b and canonical Wnt signaling were coupled through a feed-forward positive feedback loop, forming a biological regulatory circuit. Finally, in vivo study further demonstrated that the increase of miR-20b could promote the growth of cancer cells. Interpretation: Overall, our findings offered compelling evidence that miR-20b contributes to the development of NSCLC by inhibiting APC via the canonical Wnt signaling pathway. Funding: This work was supported by FDCT grants from the Science and Technology Development Fund of Macao (Project code: 082/2013/A3,082/2015/A3,0003/2018/A1,130/2017/A3 and 046/2016/A2). Declaration of Interests: "There is no conflict of interests." Ethics Approval Statement: Animal studies were approved by the Ethical Committee of Macau University of Science and Technology.