Cathepsin B induces expression of hypoxia inducible factor-1 alpha and enhances invasiveness of colon cancer cells

Objective To study the expression of hypoxia inducible factor-1 alpha(HIF-1α) induced by cathepsin B (CatB) and its effect on invasiveness of colon cancer cells.Methods Using molecular cloning technique,eukaryotic CatB cDNA were transfected into Lovo cells,a human colon cancer cell line.Invasiveness of the cells was examined with transwell.A hypoxia model of Lovo was reproduced.Expression of HIF-1αwas detected by Western blotting.Results The number of Lovo cells trans-fected with CatB penetrating transwell filter membrane was(14.8±4.2),and was larger than that of cells transfected with empty vector(8.6±3.7) and the control Lovo cells(8.4±3.2).HIF-1αexpression was detected weakly at 0 h and 6 h,and enhanced expression of HIF-1αwas found at 12 h and 24 h after the cells were exposed to low oxygen tension(P0.05).The expression of HIF-1αin cells of the three groups was not significantly different at 0 h and 6 h after hypoxia(P0.05).But enhanced expression of HIF-1αwas found in CatB positive Lovo cells rather than in CatB negative cells at 12 h and 24 h after hypoxia(P0.01).Conclusions CatB induces HIF-1αexpression in colon cancer cells that makes tumor cells adapted to hypoxia environment and enhances invasiveness of the cancer cells.