The Anti-tumor Role And Molecular Mechanism Of MiR-148a-3p In Non-small Cell Lung Cancer

Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer death among both males and females around the world.There are two main types of lung cancer:non-small cell lung cancer(NSCLC)and small cell lung cancer(SCLC)and the NSCLC contribute to the majority(80%to 85%)of lung cancer Though many traditional therapeutic modalities,such as surgical resection,primary chemotherapy,radiotherapy or their combinations,are considered as the common treatment choices for NSCLC,more than 70%patients have a dismal 5-year survival rate of less than 16%for locally advancing or metastatic disease at the time of clear diagnosis.Therefore,a better understanding of the mechanisms and developing useful therapeutic targets of lung cancer is urgently needed.MicroRNAs(miRNAs)are comprised of a large family of about 21-nucleotide-long non-coding RNAs that have emerged as key regulators in post-transcription of gene expression.Previous studies demonstrated that the expression level of miR-148a-3p was significantly down-regulated in the gastric cancer(GC),laryngeal squamous cell carcinoma(LSCC)and bladder cancer(BC)etc.,besides,forced expression of miR-148a-3p significantly inhibited the proliferation and development of LSCC and BCa.However,the expression pattern,functions and specific mechanisms of miR-148a-3p in the carcinogenesis of NSCLC are still elusive.Son of sevenless(SOS),the Ras-specific guanine nucleotide-exchange factor,couples the receptor tyrosine kinases(RTKs)stimulation to Ras activation by promoting the conversion of Ras-GDP to Ras-GTP.The SOS family consist of two human homologues,SOS1 and SOS2.SOS2 facilitates the activation process of Ras,and the activated Ras subsequently interacts with several effector such as Raf and PI-3 kinases to motivate the mitogen-activated protein kinase/extracellular signal regulated kinase(MAPK/ERK)signal pathway.Several studies have confirmed that this signaling cascades are of great significance in the control of activities during cell proliferation and differentiation as well as cell cycle,cell migration and cell shape.Nevertheless,the functions of SOS2 and its relationship with the downstream signaling in NSCLC have not been well described.Our research focused on the biological effect of miR-148a-3p and its epigenetic regulation mechanism in NSCLC.The main investigations and results are as follows:1.MiR-148a-3p is down-regulated in NSCLC cells.2.To evaluate the inhibited effects of miR-148a-3p on cell proliferation,NSCLC cell lines HCC827 and A549 were transfected with miR-148a-3p mimics and negative control.Then found that over-expression of miR-148a-3p inhibits the proliferation of NSCLC cells by triggering G1-phase arrest.EMT progression was obviously inhibited by over-expressed miR-148a-3p in NSCLC cells.3.The online bioinformatic databases TargetScan and miRDB online databases were utilized to predict the potential target of miR-148a-3p.SOS2 was of particular interest and chosen as the candidate target.Our study indicated that miR-148a-3p down-regulates the expression level of SOS2 via targeting part of its 3’UTR.Then we elucidated that SOS2 was the direct target of miR-148a-3p which was further confirmed by dual-luciferase reporter and rescue experiment.4.To investigate whether down-regulation of SOS2 has the same effect as miR-148a-3p-mediated suppression of NSCLC,we analyzed the functions of SOS2 in NSCLC cells.The results illustrated that the silence of SOS2 caused dramatic suppression of the migration and invasive capability,consistently with over-expression of miR-148a-3p.5.Further studies showed that miR-148a-3p inhibited the proliferation and EMT progression of Non-small Cell Lung Cancer via modulating Ras/MAPK/ERK signaling.To conclude,our study confirmed that miR-148a-3p,as a tumor suppressor in NSCLC cells,could exert its inhibitory effects on the proliferation and EMT progressions of NSCLC by modulating SOS2/MAPK/ERK signaling.