Recombinant snake venom metalloproteinase inhibitor BJ46A inhibits invasion and metastasis of B16F10 and MHCC97H cells through reductions of matrix metalloproteinases 2 and 9 activities.

Studies have shown that the recombinant BJ46a (rBJ46a) protein can reduce matrix metalloproteinase (MMP) activities and inhibit invasion and metastasis of melanoma cells. Here, we optimized the Pichia pastoris system to evaluate rBJ46a protein as an anticancer agent. The Enzchek gelatinase/collagenase assay showed that rBJ46a inhibited MMP activities (IC50=0.119 mg/ml). Kinetic analyses using a series of double reciprocal Lineweaver-Burk plots (1/V vs. 1/S) showed a competitive mode of inhibition with rBJ46a with inhibitory efficiency against MMPs (Ki=13.6 nmol/l). Matrigel invasion assays showed significant activity of rBJ46a on tumor cells. For lung colonization assays, C57BL/6 mice were inoculated in the lateral tail vein with B16F10 cells and were treated with three i.v. injections of rBJ46a (1, 2, and 4 mg/kg) 24 h before cell inoculation, and 2 and 24 h after cell inoculation. Administration of rBJ46a suppressed lung tumor colony formation significantly. For spontaneous metastasis assays, MHCC97H cells were inoculated subcutaneously into nude mice. After 24 h, rBJ46a was administered by i.p. injections: 1, 2, and 4 mg/kg once daily for 6 days. rBJ46a decreased lung tumor colony formation significantly. Gelatin zymography showed that MMP2/MMP9 enzymatic activities in tumor cells were suppressed by rBJ46a in a dose-dependent manner, and the Km values of rBJ46a against MMP2 and MMP9 activities that were expressed in both B16F10 and MHCC97H cells were 3.6 and 1.4 μmol/l, respectively. Thus, rBJ46a can inhibit the invasion and metastasis of tumor cells by reducing MMP2/MMP9 activities, indicating that rBJ46a may be a novel therapeutic agent for antimetastasis of tumor cells.