Abstract: Objective: To investigate the effects of Dickkopf1(DKK1) protein on the biological behaviors of SBC-3 cells of human small cell lung cancer(SCLC),and to elucidate their mechanisms. Methods: The human SCLC cell strain SBC-3 were infected with lentiviruses over-expressing DKK1 and control viruses,respectively,and the cells stably expressing DKK1 protein (SBC-3-DKK1 group) and control cells (SBC-3-NC group) were obtained.RT-PCR and Western blotting methods were used to detect the expression levels of DKK1 mRNA and the expression amount of DKK1 protein in the SBC-3 cells in two groups;plate cloning assay was used to detect the colony formation rate of the cells in two groups;Transwell assay was used to observe the abilities of migration and invasion of the SBC-3 cells in two groups;Western blotting method was used to detect the expression amounts of MMP-9 protein in the SBC-3 cells in two groups. Results: The green fluorescence rate in the SBC-3 cells after lentivirus infection for 72 h was more than 80%.Compared with SBC-3-NC group,the expression level of DKK1 mRNA (P=0.004)and the expression amount of DKK1 protein in the SBC-3 cells in SBC-3-DKK1 group were significantly increased,the colony formation rate was significantly increased (P=0.002 6),the number of migration cells was significantly increased (P=0.006 2),the number of invadsion cells was significantly increased (P=0.021 4),and the expression amount of MMP-9 protein was significantly increased. Conclusion: Over-expression of DKK1 protein can promote the proliferation,migration and invasion of SBC-3 cells,and their mechanisms may be related to the up-regulation of MMP-9 protein expression.

Key words: cancer,small cell lung, dickkopf1, matrix metalloproteinase 9, colon formation rate