This study aimed to explore Semaphrin4D(Sema4D) expression and clinical significance in non-small cell lung cancer(NSCLC), and to define the roles and mechanisms of Sema4 D in regulating the malignant behaviors of A549 cells by small interfering RNA(siRNA). Firstly, immunohistochemistry revealed that Sema4 D was more frequently expressed in NSCLC than in lung benign lesion(P<0.05) and its overexprssion was associated with low differentiation(P<0.05), poor pTNM staging(P<0.05) and occurrence of lymph node(LN) metastasis(P<0.05). Endogenous Sema4 D expression was suppressed by Sema4 D siRNA in A549 cells overexpressing Sema4 D. Protein levels of Sema4 D, total Akt and p-Akt were examined by Western blotting. Cell proliferation, migration and invasion abilities were measured by MTT assay and Transwell assay respectively. Results showed that Sema4 D siRNA significantly suppressed phosphorylation of AKT in A549 cells, but it did not alter total AKT expression. In addition, efficient down-regulation of SemaD significantly inhibit cell proliferation(P<0.05), migration(P<0.05) and invasion(P<0.05) in A549 cells. These findings suggest that Sema4 D might serve as a reliable tool for early prediction of NSCLC poor prognosis. Sema4 D could play an important role in promoting tumor proliferation, migration and metastasis in the NSCLC, by influencing the Akt protein phosphorylation. Inhibition of Sema4 D may be a useful approach for the treatment of NSCLC.
Vascular endothelial growth factor 165 (VEGF165)-mediated autocrine stimulation of tumor cells enhances the progression to a malignant phenotype. VEGF165b competes with VEGF165 and binds to vascular endothelial growth factor receptor (VEGFR), resulting in inhibition of downstream signal transduction pathways. This study was designed to investigate the role of VEGF165b in the migration and invasion of human lung adenocarcinoma A549 cells. The full-length of VEGF165b was constructed and cloned into an expression plasmid (pVEGF165b), and then transfected into A549 cells. Dimethylthiazolyl-2, 5-diphenyltetrazolium bromide (MTT) assay was used to detect the effect of VEGF165b on proliferation of transfected cells. Reverse transcription polymerase chain reaction (RT-PCR) was employed to examine the effect of VEGF165b on the expression of VEGF165 in transfected cells. Wound-healing assays were used to investigate the effect of VEGF165b on migration of transfected cells. Matrix metalloproteinase (MMPs) activity assay and in vitro invasion assay were used to determine the role of VEGF165b in invasion of transfected cells. There was no significant change in proliferation of A549 cells after transfection of pVEGF165b, but the expression of VEGF165, migration and invasion in A549 cells were inhibited. Furthermore, exogenous VEGF165b inhibited the activity of MMP9 in the supernatant of A549 cells and the subsequent invasion capacity of those cells. We therefore conclude that exogenous VEGF165b can inhibit the expression of VEGF165, as well as the migration and invasion of A549 cells, but has no effect on the proliferation of A549 cells.
