Mammary carcinoma cells over‐expressing tissue inhibitor of metalloproteinases‐1show vascular endothelial growth factor expression

Abstract

The tissue inhibitor of metalloproteinases-1 (TIMP-1) has at least 2 independent functions, i.e., regulation of matrix metalloproteinases and erythroid-potentiating activity. We investigated the effects of TIMP-1 over-expression on tumor growth, using cloned lines derived from a TIMP-1-transfected rat breast carcinoma cell line. The in vitro growth rate of the TIMP-1-transfected clones was indistinguishable from that of the control. In contrast, the highest TIMP-1-producing clone (159.0 ng/ml), designated as T-H, formed 4.6-fold larger s.c. tumors than did the control after 14 days. Tumors derived from an intermediate TIMP-1-producing clone (45.4 ng/ml), designated as T-M, were 1.9-fold larger than the control. TIMP-1 over-expression was associated with increased vascular endothelial growth factor (VEGF) expression, vascularization and proliferative activity of the s.c. tumors. Similar to the rat breast carcinoma cells, transfection of TIMP-1 cDNA into the human breast carcinoma cell line MCF-7 resulted in up-regulation of VEGF, with a linear relationship between TIMP-1 and VEGF production in 9 cell clones examined. There was, however, no change in VEGF expression when the rat and human breast carcinoma cell lines were exposed to exogenous recombinant TIMP-1. Our findings suggest that over-expression of TIMP-1 confers growth advantage on breast carcinoma cells in vivo and that up-regulation of VEGF expression may play an important role in this TIMP-1-mediated, growth-stimulating effect. Int. J. Cancer 75:81-87, 1998.1998 Wiley-Liss, Inc. † Matrix metalloproteinases (MMPs) are involved in various pathological processes, including tumor invasion, in which degradation of the extracellular matrix is a key event (MacDougall and Matrisian, 1995). MMP activities are regulated by tissue inhibitors of metalloproteinases (TIMPs), which bind to the active site of MMPs (Murphy and Docherty, 1992). To date, 4 members of the TIMP family have been characterized: TIMP-1, TIMP-2, TIMP-3 (Denhardt et al., 1993) and TIMP-4 (Greene et al., 1996). A number of reports have demonstrated TIMP-1-mediated inhibition of tumor invasion and metastasis in rodent models, both when administered exogenously and when over-expressed through TIMP transfection of different types of tumor cell lines (Schultz et al., 1988;Alvarez et al., 1990;Tsuchiya et al., 1993;Thorgeirsson et al., 1982). Furthermore, down-regulation of TIMP-1 expression was associated with increased invasiveness of embryonic stem cells (Alexander and Werb, 1992). In human malignancies, TIMP-1 over-expression has been associated with tumor recurrence and poor prognosis in non-Hodgkin's lymphoma (Kossakowska et al., 1991) and carcinoma of the colon (Urbanski et al., 1993) and lung (Fong et al., 1996). It has been reported that high TIMP-1 expression in tumorigenic cells could result in either increased or decreased tumor invasion in a tumor-specific manner (Soloway et al., 1996). TIMP-1 is also known as erythroid-potentiating activity (EPA) due to its growth-stimulating effect on...

Bcl‐2 overexpression in melanoma cells increases tumor progression‐associated properties and in vivo tumor growth

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