Inhibition of matrix metalloproteinases by over‐expression of tissue inhibitor of metalloproteinase‐2 inhibits the growth of experimental hemangiomas

Abstract

Inhibitors of proteases prevent tumor-associated matrix degradation, affecting tumor growth, angiogenesis and metastasis. Our study was designed to investigate the effect of inhibition of matrix metalloproteinases (MMPs) on the growth of experimental hemangiomas, using the model of murine endothelioma eEnd.1 cells. In nude mice, these cells generate hemangiomas, consisting mostly of host-recruited endothelial cells, whose growth requires the activity of MMPs. In vitro, eEnd.1 cells produce factors that recruit endothelial cells and stimulate them to release MMPs. Over-expression of TIMP-2, following retrovirus-mediated gene transfer, decreased tumor growth in vivo. The infected clone CR1, which produces high levels of TIMP-2 (as assessed by Northern blot, ELISA and reverse zymography), formed slow-growing tumors that did not grow beyond 0.4 g, while clone 1H, which produces little TIMP-2, grew not dissimilarly to mock-infected cells and parental e.End.1 cells. Histologically, control tumors presented the features of cavernous hemangiomas, while CR1 tumors had a more solid pattern, showing foci of apoptotic cells. In vitro, TIMP-2 over-expression had no autocrine anti-proliferative effect on endothelioma cells but reduced their ability to recruit endothelial cells. CR1 cells lacked the capacity of mock-infected or parental eEnd.1 cells to stimulate endothelial cell motility and invasiveness. Antibodies against TIMP-2 restored the ability of CR1 to induce endothelial cell invasion. We conclude that, in this model, genetic increase of TIMP-2 inhibits tumor growth, apparently by affecting the recruitment and organization of host endothelial cells by the transformed cells.