SUPPRESSION OF THE TUMORIGENIC AND METASTATIC ABILITIES OF MURINE B16-F10 MELANOMA-CELLS IN-VIVO BY THE OVEREXPRESSION OF THE TISSUE INHIBITOR OF THE METALLOPROTEINASES-1

Background: Metalloproteinases participate in the first steps of tumor invasion and subsequent metastasis. Three distinct proteins have been identified as tissue inhibitors of metalloproteinases (TIMPs), and an imbalance between TIMPs and metalloproteinases may be an important factor in tumor progression. Purpose: The purpose of this study was to determine if increased levels of TIMP-1 suppressed the malignant phenotype of B16-F10 melanoma cells in mice. Methods: We examined and compared the tumorgenic and metastatic behavior of B16-F10 cells, several independent clonal cell lines that were transfected to overexpress TIMP-1, and a vector-transfected control, in both nude (BALB/c) and syngeneic (C56BL/6) mice. Tumor growth was assessed by subcutaneously injecting female nude mice with 10(5) cells of parental or transfected B16-F10 cell lines, and monitoring for the appearance of tumors at the injection site. Tumor size was measured every 2-3 days for 5 weeks. To evaluate the effect of elevated TIMP-1 on metastases, 3 X 10(4) cells were administered by intravenous injection into the tail vein of C57BL/6 mice, and the number of metastases counted on days 14 and 22. Results: Following subcutaneous injections into nude mice, TIMP-1-overexpressing cells showed a substantial decline in their primary tumor growth, characterized by a reduced tumor incidence (50%-89% versus 100% in controls) and longer periods before the appearance of tumors (15 +/- 1.0 to 19 +/- 3.3 days versus 12 +/- 0.4 days in controls). All TIMP-1 clones showed a reduction in their lung colonization ability (8.2 +/- 1.4 to 48.1 +/- 9.9 versus 59.9 +/- 6.0 metatastic nodules in controls) following intravenous injection into syngenic mice. The number of lung metastases arising from four of the five TIMP-1-overexpressing lines was significantly lower than those formed by parental or control cells. Conclusions: The data demonstrate that an overexpression of TIMP-1 directly inhibits the tumorigenic as well as metastatic potential of B16-F10 cells in mice, lending further support to the importance of TIMP-1 in controlling malignancy.