Working towards our stated goal of preclinical development of TIMP-2 as a novel cancer therapeutic we have performed in vivo xenograft growth experiments. These experiments have shown that the TIMP-2 homolog lacking MMP inhibitory activity known as Ala+TIMP-2 effectively inhibits growth of the human A549 lung cancer xenograft, when overexperssed in the tumor cells using a retroviral vector system. Ongoing experiments are utilizing the TET-On system to examine the effect of forced expression of TIMP-2 and Ala+TIMP-2 in established tumor systems. To further the development of Ala+TIMP-2 as a therapeutic we have developed CHO cell expression systems for the production of recombinant Ala+TIMP-2 and TIMP-2, and are continuing these efforts to optimize production of large quantities under good manufacturing procedures (GMP). It is our plan to test these materials as therapeutic agents in both xenogfraft and syngeneic murine tumor models to demonstrate the effectiveness of treatment with exogenous recombinant proteins. We also plan to utilize newly developed genetically engineered mouse models (GEMMs) of lung cancer for testing the anti-tumor effects of recombinant exogenous TIMP-2 and Ala+TIMP-2. The results will be compared with the effects of other members of the TIMP family for potency and efficacy. These models will focus on the treatment of lung cancer (A549 and Lewis Lung) as well as melanoma (A2058 and B16F10). Various dosing regimens will be utilized to compare the relative in vivo effectiveness of Ala+TIMP-2 compared to TIMP-2. Preliminary studies indicate that Ala+TIMP-2 is more effective than TIMP-2, which is attributed to the fact that Ala+TIMP-2 does not bind to the active site of MMP like TIMP-2, therefore effectively increasing its concentration for cell binding sites. Another important aspect of this project is to determine if we can develop peptide analogs that could be utilized for in vivo therapy. Furthermore we propose to develop a high throughput screening assay to screen synthetic small molecule analogs that can compete for TIMP-2, Ala+TIMP-2, or TIMP peptide binding to the cell surface receptor integrin alpha3 beta1, that we have shown modulates the anti-angiogenic and anti-tumorigenic activity of Ala+TIMP-2. Tissue inhibitor of metalloproteinase 2 (TIMP-2) belongs to a small family of endogenous proteins that function to inhibit a group of enzymes, the matrix metalloproteinases (MMPs). TIMP-2 inhibits endothelial cell proliferation and migration in vitro and angiogenesis in vivo, through MMP dependent and independent mechanisms. However, little is known regarding the contribution of these mechanisms to the antitumor effects of TIMP-2. Using a retroviral delivery system, we stably overexpressed TIMP-2 and its mutant Ala+TIMP-2 (devoid of MMP inhibitory activity) in human adenocarcinoma A549 cells. Using real time PCR, western blot and ELISA we confirmed enhanced TIMP-2 expression and its MMP inhibitory activity by reverse zymography. In vitro, growth assays suggested that TIMP-2 and Ala+TIMP-2 did not alter basal cell proliferation rates, however, tumor cell migration and invasion were inhibited. In vivo, both TIMP-2 and Ala+TIMP-2 A549 xenografts exhibited reduced growth rate, CD31 immunostaining indicated decreased intra-tumoral microvascular density and TUNEL demonstrated enhanced tumor cell apoptosis. Immunoblotting and Immunohistochemistry analyses in vitro and of A549 xenograft tissues with either phospho-FAK (Tyr397) or phospho-AKT (Ser473) showed decreased activation in both TIMP-2 and Ala+TIMP-2 tumor cells. We conclude that TIMP-2-mediated inhibition of tumor growth occurs, at least in part, independently of MMP inhibition, and is a consequence of both direct effects of TIMP-2 on tumor cells and modulation of the tumor microenvironment.
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