Inhibition of matrix metalloproteinases by overexpression of tissue inhibitor of metalloproteinase-2 inhibits the growth of experimental hemangiomas

Inhibitors of proteases prevent tumor-associated matrix degradation, affect ing tumor growth, angiogenesis and metastasis, Our study was designed to in vestigate the effect of inhibition of matrix metalloproteinases (MMPs) on t he growth of experimental hemangiomas, using the model of murine endothelio ma eEnd.1 cells. In nude mice, these cells generate hemangiomas, consisting mostly of host-recruited endothelial cells, whose growth requires the acti vity of MMPs. In vitro, eEnd.1 cells produce factors that recruit endotheli al cells and stimulate them to release MMPs. Overexpression of TIMP-2, foll owing retrovirus-mediated gene transfer, decreased tumor growth in vivo. Th e infected clone CR1, which produces high levels of TIMP-2 (as assessed by Northern blot, ELISA and reverse zymography), formed slow-growing tumors th at 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. H istologically, control tumors presented the features of cavernous hemangiom as, while CR1 tumors had a more solid pattern, showing foci of apoptotic ce lls. In vitro, TIMP-2 over-expression had no autocrine anti-proliferative e ffect on endothelioma cells but reduced their ability to recruit endothelia l cells. CRI cells lacked the capacity of mock-infected or parental eEnd.1 cells to stimulate endothelial cell motility and invasiveness. Antibodies a gainst TIMP-2 restored the ability of CRI to induce endothelial cell invasi on. We conclude that, in this model, genetic increase of TIMP-2 inhibits tu mor growth, apparently by affecting the recruitment and organization of hos t endothelial cells by the transformed cells. (C) 2001 Wiley-Liss, Inc.