Abstract:

Objective To discuss the effects of monocyte chemoattractant protein-1 （MCP-1） on the migration and invasion of lung cancer A549 cells， and to clarify the mechanisms. Methods Immunohistochemistry method was used to detect the expression of MCP-1 protein in 80 cases of non-small cell lung cancer （NSCLC） and adjacent normal lung tissues. The human lung cancer A549 cells were cultured in vitro. The MCP-1-small interfering RNA （siRNA） experiment was divided into blank group， negative control group （si-NC group）， MCP-1-siRNA-1 group， and MCP-1-siRNA-2 group. The MCP-1 over-expression experiment was divided into control group， empty vector control group （OE-NC， transfected with MCP-1 over-expression empty vector）， over-expression MCP-1 group （OE-MCP-1 group， transfected with MCP-1 over-expression plasmid）， over-expression MCP-1+extracellular regulated protein kinase （ERK） pathway inhibitor PD98059 group （OE-MCP-1+PD98059 group， co-transfected with MCP-1 over-expression plasmid and PD98059）， and PD98059 group （transfected with PD98059）.The MCP-1 siRNA and plasmids were transfected into the lung cancer A549 cells； Western blotting method was used to verify the transfection efficiencies of the cells in various groups； the migration rate and the number of invasion cells in various groups were observed by wound healing assay and Transwell chamber assay， respectively； Western blotting method was also used to detect the expression levels of phosphorylated ERK （p-ERK）， total ERK （t-ERK）， and epithelial-mesenchymal transition （EMT）-related proteins in the A549 cells in various groups. Results Compared with adjacent tissue， the positive expression rate of MCP-1 protein in NSCLC tissue was significantly increased （P<0.05）， and the expression level of MCP-1 protein was related to TNM stage and lymph node metastasis （P<0.05）. Compared with si-NC group， the expression level of MCP-1 protein in the cells in MCP-1-siRNA-1 and MCP-1-siRNA-2 groups was significantly decreased （P<0.01）. Compared with control group and OE-NC group， the expression level of MCP-1 protein in the cells in OE-MCP-1 group was significantly increased （P<0.01）. The wound healing assay results showed that compared with si-NC group， the migration rate of the cells in MCP-1-siRNA-1 and MCP-1-siRNA-2 groups were significantly decreased （P<0.01）. Compared with OE-NC group， the migration rate of the cells in OE-MCP-1 group was significantly increased （P<0.01）； compared with OE-MCP-1 group， the migration rate of the cells in OE-MCP-1+PD98059 group was significantly decreased （P<0.01）. Compared with OE-MCP-1+PD98059 group， the migration rate of the cells in PD98059 group was significantly decreased （P<0.01）. The Transwell chamber assay results showed that compared with si-NC group， the number of invasion cells in MCP-1-siRNA-1 and MCP-1-siRNA-2 groups was significantly decreased （P<0.01）. Compared with OE-NC group， the number of invasion cells in OE-MCP-1 group was significantly increased （P<0.01）； compared with OE-MCP-1 group， the number of invasion cells in OE-MCP-1+PD98059 group was significantly decreased （P<0.01）； compared with OE-MCP-1+PD98059 group， the number of invasion cells in PD98059 group was significantly decreased （P<0.01）.The Western blotting results showed that compared with si-NC group， the expression levels of p-ERK， Vimentin， and N-cadherin protein in the cells in MCP-1-siRNA-1 and MCP-1-siRNA-2 groups were significantly decreased （P<0.05 or P<0.01）， and the expression level of E-cadherin proteins was significantly increased （P<0.01）. Compared with OE-NC group， the expression levels of p-ERK， Vimentin， and N-cadherin proteins in the cells in OE-MCP-1 group were significantly increased （P<0.01）， and the expression level of E-cadherin protein was significantly decreased （P<0.01）. Compared with OE-MCP-1 group， the expression levels of p-ERK， Vimentin， and N-cadherins proteins in the OE-MCP-1+PD98059 group were significantly decreased （P<0.01）， and the expression level of E-cadherin protein was significantly increased （P<0.05）. Compared with OE-MCP-1+PD98059 group， the expression levels of p-ERK， Vimentin， and N-cadherin proteins in the cells in PD98059 group were significantly decreased （P<0.05 or P<0.01）， and the expression level of E-cadherin protein was increased （P<0.01）. Conclusion MCP-1 protein can upregulate the expression of EMT-related proteins in the lung cancer A549 cells， and promote the migration and invasion of the lung cancer A549 cells； its mechanism may be related to the activation of the ERK signaling pathway.

Key words: Monocyte chemoattractant protein-1, Extracellular-signal regulated protein kinase, Cancer，non-small cell lung, Cell invasion, Cell migration