Role of MMP-9 and its tissue inhibitor TIMP-1 in human osteosarcoma: findings in 42 patients followed for 1-16 years.

Background: The activity of matrix metalloproteinases (MMPs) in degrading extracellular matrix is controlled by activation of proenzymes and inhibition of MMP tissue inhibitors (TIMPs).

Patients and methods: To assess the proteolytic cascade imbalance in malignancy progression, tissue expression and serum levels of MMP-2, MMP-9 and of their inhibitors TIMP-2 and TIMP-1 respectively were evaluated in 42 selected patients with high-grade osteosarcoma (OS). MMP-2, MMP-9, TIMP-2 and TIMP-1 were studied in biopsies by immunohistochemistry and in serum by ELISA test. Patients were subdivided into 3 groups according to their follow up: continuously disease-free, diagnosis of metastasis during follow-up, and metastasis at diagnosis.

Results: Immunohistochemistry demonstrated an imbalance between MMPs and TIMPs, with a more evident role for MMP-9 than for MMP-2 in tumor progression. TIMP-1 inhibitor in plasma was higher in patients with osteosarcoma than in a control group. This high value of TIMP-1 was particularly evident in the group of patients who later developed metastases and/or local recurrences, and in those with metastases at diagnosis.

Interpretation: Our findings confirm the protective action of TIMP-1, as MMP inhibitor, but also show its activity as a growth factor underlining its multifunctional role in OS.