Modulation of Tumor-host Interactions, Angiogenesis, and Tumor Growth by Tissue Inhibitor of Metalloproteinase 2 via a Novel Mechanism

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Abstract
Solid tumors depend on angiogenesis for sustained growth. Tissue inhibitor of metalloproteinase 2 (TIMP-2) is an angiogenesis inhibitor initially characterized for its ability to block matrix metalloproteinases; however, recent data suggest that the antiangiogenic action of TIMP-2 may rely on matrix metalloproteinase-independent mechanisms. The aim of this study was to identify molecular pathways involved in the effects of TIMP-2 on processes dependent on tumor-host interactions such as angiogenesis. Using in vitro cell culture and a syngeneic murine tumor model, we compared the effects of TIMP-2 overexpression on gene expression profiles in vitro to those observed in vivo. Validating these findings by real-time quantitative PCR and layered protein scanning, we identified up-regulation of mitogen-activated protein kinase phosphatase 1 as an effector of the antiangiogenic function of TIMP-2. Up-regulation of mitogen-activated protein kinase phosphatase 1 in tumors overexpressing TIMP-2 leads to dephosphorylation of p38 mitogen-activated protein kinase and inhibition of tumor growth and angiogenesis. Phosphatase activity appears important in regulating tumor angiogenesis, offering a promising direction for the identification of novel molecular targets and antiangiogenic compounds for the treatment of cancer.