The Effects Of MicroRNA-153 On Lung Cancer And The Underlying Mechanisms

Background and PurposeLung cancer remains one of the leading causes of cancer death worldwide despite that tremendous advances have been made to understand the nature of this cancer.This is largely ascribed to our incomplete understanding of the complex processes and multifatorial properties of lung cancers.Recently,the critical role of micro RNAs(mi RNAs)in the tumorigenesis and development of lung cancers has been well recognized,which adds a new layer of regulatory network of lung cancers.In our pilot study to search for the key mi RNAs in lung cancers,we identified mi R-153 as a promising candidate in regulating lung cancer pathology.This study was therefore designed to experimentally assess the role of mi R-153 with both in vitro cellular model and in vivo xenograft tumor model,and to delineate the associated signling mediators and molecular mechanisms.MethodsIn vitro,quantitative real-time PCR(q RT-PCR)was used to detect the expression of mi R-153 and AKT m RNA in lung cancer tissues and cell lines.Western blot was used to detect the protein expression of total AKT and phosphorylated AKT(p-AKT)in lung cancer tissues and cell lines.Cell proliferation was monitored by cell counting after transfection of mi R-153 and determined by using Cy QUANTV? NF cell proliferation assay kit.The scratch assay was performed to monitor the effects of mi R-153 on migration of lung cancer cells.Apoptosis was analyzed by terminal deoxynucleotidyl transferase d UTPnick end labeling(TUNEL).Luciferase reporter assay was performed to verify the direct targeting of AKT by mi R-153.The efficacy of mi R-153 in suppressing in vivo tumor growth was assessed using the xenograft methods in nude mice.ResultsMi R-153 level was significantly lower in lung cancer tissues than in adjacent tissues.The protein and m RNA levels of protein kinase B(AKT),a well established oncoprotein,were both increased in lung cancer tissues relative to adjacent tissues.Overexpression of mi R-153 significantly repressed AKT protein level,an effect substantially abrogated by co-transfection of AMO-153,the specific inhibitor of mi R-153.Luciferase assay showed that transfection of mi R-153 markedly suppressed the fluorescent intensity of chimeric vectors carrying the 3’-UTR of AKT,but not on the mutant construct,indicating that AKT is regulated by mi R-153.Overexpression of mi R-153 significantly inhibited the proliferation and migration,and promoted apoptosis of A549 and H460 small lung cancer cells and BE-1 non-small lung cancer cells as well,and suppressed the growth of xenograft tumors in vivo.Interestingly,lung cancer cells with lower endogenous mi R-153 expression were more sensitive to inhibition caused by ectopic overexpression of mi R-153.The IC50 of mi R-153 on lung cancer cells was correlated with the endogenous mi R-153 level,but negatively correlated with AKT level.Knockdown of AKT expression suppressed lung cancer cell proliferation.Conclusions(1)Mi R-153 is a novel tumor-suppressive mi RNA with its remarkable anti-lung cancer efficacy by targeting AKT.(2)Abnormal downregulation of mi R-153 is one of the molecular mechanisms for the pathogenesis of human lung cancers.(3)Mi R-153 replacement may be a rational mi RNA-based therapeutic approach for lung cancers.