ABSTRACT
<p><b>OBJECTIVE</b>To study the function of IL-18 in promoting metastasis of lung cancer.</p><p><b>METHODS</b>The differential expression of IL-18 protein or mRNA level between highly and poorly metastatic sublines of human lung giant cell carcinoma metastatic model was detected by Western blot, semi-quantitative RT-PCR and northern blot analysis. The poorly metastatic PLA801C subline or highly metastatic PLA801D subline was transfected with constructed IL-18 sense or IL-18 antisense expressed plasmid by lipofectamine stable transfection technique. The metastasis-related effect mediated by IL-18, the metastatic phenotype differences, cell motility and cell invasion potential in vitro determined by MICS system and the expression level of metastasis-associated biomarkers detected by Western blot analysis, were compared between IL-18 stably transfectants and mock control, i.e. between PLA801C/IL-18(S) and PLA801C/pcDNA3.1, or between PLA801D/IL-18(As) and PLA801D/pcDNA3.</p><p><b>RESULTS</b>IL-18 was only present in highly metastatic PLA801D subline at either protein or mRNA level, which implied that IL-18 might play a role in promoting metastasis of lung cancer. After IL-18 sense expressed plasmid was transfected into poorly metastatic PLA801C subline, IL-18 fused protein with myc tag detected by Western blot analysis using either IL-18 or myc tag monoclonal antibody. In addition, cell motility ability in vitro was significantly increased about 3 times and E-cadherin protein was significantly down-regulated at about 50% in PLA801C/IL-18(S) transfectants compared with mock control. While IL-18 expressed plasmid was transfected into highly metastatic PLA801D subline, IL-18 protein and mRNA were simultaneously decreased by 30%. In addition, cell invasion ability in vitro was significantly decreased at about 75% and E-cadherin protein was significantly up-regulated in PLA801D/IL-18(As) transfectants compared with mock control.</p><p><b>CONCLUSION</b>IL-18 might play a role in enhancing tumor metastasis of lung cancer by down-regulating E-cadherin protein expression.</p>
Subject(s)
Humans , Cadherins , Metabolism , Carcinoma, Giant Cell , Metabolism , Cell Line, Tumor , Cell Movement , DNA, Antisense , Genetics , Gene Expression Regulation, Neoplastic , Interleukin-18 , Genetics , Lung Neoplasms , Metabolism , Pathology , Neoplasm Invasiveness , Neoplasm Metastasis , Genetics , Plasmids , RNA, Messenger , Genetics , TransfectionABSTRACT
<p><b>OBJECTIVE</b>To study the metastasis-associated molecules differentially expressed in highly and poorly metastatic sublines and the mechanism of metastasis in lung giant cell carcinoma.</p><p><b>METHODS</b>Highly and poorly metastatic sublines (PLA801D and PLA801C)were used as metastasis model. Cell motility and invasion assay in vitro were first compared between the two sublines. Then, gelatin zymography analysis was used to determine the MMP-2 and MMP-9 activity. The protein expression level of secreted MMP-2, MMP-9, TIMP-1, TIMP-2 and intracellular expression level of p53, p16, PCNA, CD44(V6) isomeride, E-cadherin, CK18, nm23-H1 as well as the mRNA expression level of MMP-2, MMP-9, TIMP-1, TIMP-2, VEGF were compared through Western blot. Semi-quantitative RT-PCR analysis was used to determine the intracellular mRNA expression of MMP-2, MMP-9, TIMP-1, TIMP-2 and VEGF.</p><p><b>RESULTS</b>The in vitro cell invasion potential of highly metastatic subline PLA801D was significantly higher than that of poorly metastatic subline PLA801C by about 4 folds, while the cell motility potential was similar. The secreted MMP-2 activity was notably higher in PLA801D, which was initiated by the higher expression of MMP-2 at protein and mRNA level. In addition, the expression level of p53, PCNA, CK18 protein and VEGF mRNA were significantly higher, while the expression level of p16, E-cadherin and nm23-H1 protein were significantly lower in PLA801D. Some molecules such as MMP-9, TIMP-1, TIMP-2, CD44(V6) isomeride, which had been reported to be associated with tumor metastasis, were not observed to change significantly between the two sublines.</p><p><b>CONCLUSION</b>There are significant differences in metastatic potential and phenotypes between highly and poorly metastatic sublines of lung giant cell carcinoma. Some differentially expressed molecules might be playing roles in promoting or inhibiting metastasis of lung giant cell carcinoma, which may be useful to elucidate the mechanism of metastasis.</p>