Objective         To determine the effect of matrix metalloproteinase-26 (MMP-26) on cell invasiveness in lung cancer 95-C cells and its possible underlying mechanism.         Methods        A full-length cDNA encoding human MMP-26 was cloned into the eukaryotic expression vector PUC57

and this vector was designated as PUC57-MMP-26. After the vector was transfected into 95-C cells

the stable cells expressing MMP-26 were screened out

then RT-PCR was used to detect the mRNA expression of MMP-26 and MMP-9. The secretion of MMP-9 in the transfected cells was detected by gelatin zymography. In vitro invasion was detected by transwell assay and localization of MMP-26 and MMP-9 proteins were determined by double immunofluorescent staining.         Results         Transfection of MMP-26 expressing plasmid PUC57-MMP-26 in 95-C cells led to over-expression of MMP-26 mRNA and MMP-9 mRNA（P0.05）

and cell invasiveness in these cells were significantly promoted （P0.05）. The results of gelatin zymogram revealed that MMP-26 over-expression enhanced the secretion of MMP-9（P0.05）. Double immunofluorescence staining revealed that MMP-26 and MMP-9 were co-localized in MMP-26-transfected 95-C cells.         Conclusion        MMP-26 is involved in invasion-promoting regulating of lung cancer cells

and it functions

at least in partial

through interaction with MMP-9.