Effect Of MYOCD On TGF-?-induced Growth Inhibition In Non-small Cell Lung Cancer Cells

Background and Objective: Growing evidence has shown that lung cancer is the world's most common cancer,which is characterized by highest mortality,and non-small cell lung cancer(NSCLC)accounts for about 85%.It is well known that TGF-? pathway strongly inhibits proliferation in the early stages of cancer.Myocardin(MYOCD),as a transcriptional co-activator,has been reported extensively in relation to the proliferation of cancer cells,but the roles by which Myocardin regulates TGF-?-mediated cell proliferation in NSCLC has not been elucidated.Methods:(1)Expression of MYOCD mRNA were detected in 105 paired NSCLC tissue samples and paired non-cancerours tissues using quantitative real-time PCR(qRT-PCR),and analyzed by Prism software.(2)Five NSCLC cell line were exposed to 5 ng/ml TGF-?1 for 24 h,and the expression of MYOCD mRNA and protein were deterined by quantitative RT-PCR and Western Blotting.(3)With or without the treatment of TGF-?1,cell proliferation was detected using CCK-8 assay and colony foration in A549 and SPC-A1 cells,respectively,in which the MYOCD was silenced by transfection of small interference RNAs.(4)With or without stimulation of TGF-?1,cell cycle was detected using propidium iodide(PI)staining flow cytometry in A549 and SPC-A1 cells in which the MYOCD was silenced,respectively.Results:(1)Real-time PCR results showed that the MYOCD mRNA expression levels were lower in 105 non-small cell lung cancer tissues than in paired non-cancerours tissues(p <0.01).(2)MYOCD expression were up-regulated in A549,SPC-A1 and H1650 cell lines in the presence of TGF-?1,but not in H1299 or H226 cell lines.(3)The cell proliferation inhibition induced by TGF-?1 was significantly reversed when MYOCD was silenced in A549 and SPC-A1 cells.(4)Knockdown MYOCD expression in NSCLC cells showed that the proportion of S phase was up-regulated and the G1 phase was decreased whether with the treatment of TGF-?1 or not.Conclusion: Our study showed that MYOCD expression was significantly down-regulated in NSCLC tissues,and plays a marked role in TGF-?-mediated NSCLCcell growth inhibition.More works are needed to clarify the mechanism by which MYOCD regulates TGF-? signaling.