[Function of IL-18 in promoting metastasis of lung cancer].
OBJECTIVE: To study the function of IL-18 in promoting metastasis of lung cancer. METHODS: 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. RESULTS: 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. CONCLUSION: IL-18 might play a role in enhancing tumor metastasis of lung cancer by down-regulating E-cadherin protein expression.