HE Jing-dong, LUO Hong-lei, LI Jin, FENG Wan-ting , CHEN Long-bang

Background  Interferon-induced transmembrane protein 1 (IFITM1) has been identified as a molecular marker of the colorectal tumors; however its influences on the biological behaviors of the colorectal cancer cells are currently unknown. We aimed to study the influences of IFITM1 on the proliferation, invasion, and metastasis of the colorectal cancer SW480 cell lines.
Methods  We constructed IFITM1/pEGFP-C3 recombinant plasmids and transfected them into the colorectal cancer SW480 cell lines. IFITM1/pEGFP-C3 recombinant plasmids were identified by means of immunofluorescence, laser confocal scanning microscopy, and reverse transcription polymerase chain reaction. IFITM1/SW480 cells with stable over-expression of IFITM1 were confirmed by G418 screening. The influences of IFITM1 on the proliferation of the SW480 cell lines were investigated by MTT assay and tumor transplantation experiments in nude mice. Cell invasion experiments were performed to determine the invasion capacity of the IFITM1/SW480 cells. Matrix metalloproteinase 2 (MMP-2) and MMP-9 activities were detected by the gelatin zymographic analysis, and MMP-9 expression by the Western blotting analysis.
Results  IFITM1/pEGFP-C3 recombinant plasmids were successfully constructed in this study, and the IFITM1/SW480 cells with stable IFITM1 gene over-expression were confirmed by G418 screening. MTT results showed that the proliferation of the IFITM1/SW480 cells was significantly enhanced (P <0.01). Tumors were harvested from four weeks old mice. Tumor volumes were (1347.00±60.94) mm3, (1032.40±111.38) mm3 and (1018.78±28.83) mm3; and tumor weights were (1522.34±62.76) mg, (1137.78±97.22) mg and (1155.76±133.31) mg for mice inoculated with the IFITM1/SW480 cells, pEGFP-C3/SW480 cells and SW480 cells, respectively. Tumor volumes and weights from mice inoculated with the IFITM1/SW480 cells were significantly increased (P <0.01). In addition, the numbers of the SW480 cells and IFITM1/SW480 cells that migrated through Matrigel were 448.64±38.09 and 540.45±44.61, respectively; so the invasive ability of the SW480 cells transfected with IFITM1 gene was significantly greater than that of the SW480 cells (P <0.01). Gelatin zymographic analysis showed that MMP-9 and MMP-2 protein activities in the IFITM1/SW480 cells were significantly enhanced, and Western blotting analysis showed that MMP-9 expression in the IFITM1/SW480 cells was also increased.
Conclusion  IFITM1 can enhance the proliferation, invasion, and metastasis of the colorectal cancer SW480 cell lines.