No abstract

Proteolysis in close vicinity of tumor cells is a hallmark of cancer invasion and metastasis. We show here that mouse mammary tumor virus-polyoma middle T antigen (PyMT) transgenic mice deficient for the cysteine protease cathepsin B (CTSB) exhibited a significantly delayed onset and reduced growth rate of mammary cancers compared with wild-type PyMT mice. with PyMT;ctsb +/+ cells, was used to address the role of stroma-derived CTSB in lung metastasis formation. Notably, ctsb À/À mice showed reduced number and volume of lung colonies, and infiltrating macrophages showed a strongly up-regulated expression of CTSB within metastatic cell populations. These results indicate that both cancer cellderived and stroma cell-derived (i.e., macrophages) CTSB plays an important role in tumor progression and metastasis.

Due to its ability to inhibit pro-metastatic matrix metalloproteinases, tissue inhibitor of metalloproteinases (TIMP)-1 has been thought to suppress tumor metastasis. However, elevated systemic levels of TIMP-1 correlate with poor prognosis in cancer patients suggesting a metastasis-stimulating role of TIMP-1. In colorectal cancer patients, tumor as well as plasma TIMP-1 levels were correlated with synchronous liver metastasis or distant metastasis-associated disease relapse. In mice, high systemic TIMP-1 levels increased the liver susceptibility towards metastasis by triggering the formation of a pre-metastatic niche. This promoted hepatic metastasis independent of origin or intrinsic metastatic potential of tumor cells. High systemic TIMP-1 led to increased hepatic SDF-1 levels, which in turn promoted recruitment of neutrophils to the liver. Both inhibition of SDF-1-mediated neutrophil recruitment and systemic depletion of neutrophils reduced TIMP-1-induced increased liver susceptibility towards metastasis. This indicates a crucial functional role of neutrophils in the TIMP-1-induced pre-metastatic niche. Conclusion Our results identify TIMP-1 as an essential promoter of hepatic pre-metastatic niche formation.

The serine protease urokinase-type plasminogen activator (uPA) interacts with a specific receptor (uPAR) on the surface of various cell types, including tumor cells, and plays a crucial role in pericellular proteolysis. High levels of uPA and uPAR often correlate with poor prognosis of cancer patients. Therefore, the specific inhibition of uPA with small molecule active-site inhibitors is one strategy to decrease the invasive and metastatic activity of tumor cells. We have developed a series of highly potent and selective uPA inhibitors with a C-terminal 4-amidinobenzylamide residue. Optimization was directed toward reducing the fast elimination from circulation that was observed with initial analogues. The x-ray structures of three inhibitor/uPA complexes have been solved and were used to improve the inhibition efficacy. One of the most potent and selective derivatives, benzylsulfonyl-D-SerSer-4-amidinobenzylamide (inhibitor 26), inhibits uPA with a K i of 20 nM. This inhibitor was used in a fibrosarcoma model in nude mice using lacZ-tagged human HT1080 cells, to prevent experimental lung metastasis formation. Compared with control (100%), an inhibitor dose of 2 ؋ 1.5 mg/kg/day reduced the number of experimental metastases to 4.6 ؎ 1%. Under these conditions inhibitor 26 also significantly prolonged survival. All mice from the control group died within 43 days after tumor cell inoculation, whereas 50% of mice from the inhibitor-treated group survived more than 117 days. This study demonstrates that the specific inhibition of uPA by these inhibitors may be a useful strategy for the treatment of cancer to prevent metastasis.The detachment of malignant cells from the primary tumor and their subsequent migration within the surrounding tissue, including intravasation and extravasation into blood and lymph vessels, leads to tumor dissemination and the formation of metastases at distant loci. Whereas a solid tumor can be removed by surgery or treated by radio-, chemo-, or hormone therapy, invasive tumor cells that have spread over the whole body can form secondary tumors leading to poor prognosis or death of cancer patients. Several proteases, such as matrix metalloproteases, the cysteine proteases cathepsin B and L, the aspartyl protease cathepsin D, and serine proteases, e.g. plasmin and uPA, 1 are involved at multiple stages during growth, invasion and progression of tumors, including metastases formation (1). High levels of expression of these proteases often correlate with poor prognosis for cancer patients (2). However, in several clinical cancer trials with different types of nonspecific matrix metalloprotease inhibitors, disappointing results with poor benefit and severe side effects were observed (3). This stimulated the search for alternative proteases with matrix degrading activity as new targets for anti-cancer drugs. An important role in metastasis has been recently ascribed to the plasmin-plasminogen activation system and especially to uPA.Both, uPA and the second endogenous plasminogen activator tPA are...

The L1 cell adhesion molecule is implicated in the control of proliferation, migration, and invasion of several tumor cell types in vitro. Recently, L1 overexpression was found to correlate with tumor progression of ovarian carcinoma, one of the most common causes of cancer-related deaths in gynecologic malignant diseases. To evaluate L1 as a potential target for ovarian cancer therapy, we investigated the effects of anti-L1 monoclonal antibodies (chCE7 and L1-11A) on proliferation and migration of L1-positive human SKOV3ip ovarian carcinoma cells in vitro and the therapeutic efficacy of L1-11A against i.p. SKOV3ip tumor growth in nude mice. In vitro, both anti-L1 antibodies efficiently inhibited the proliferation of SKOV3ip cells as well as other L1-expressing tumor cell lines (renal carcinoma, neuroblastoma, and colon carcinoma). On two cell lines, hyper-cross-linking of L1-11A with a secondary antibody was necessary for significant inhibition of proliferation, indicating that cross-linking of L1 is required for the antiproliferative effect. L1-negative prostate carcinoma cells were not influenced by antibody treatment. Biweekly treatment of ovarian carcinoma-bearing mice with L1-11A led to a dose-dependent and significant reduction of tumor burden (up to À63.5%) and ascites formation (up to À75%). This effect was associated with reduced proliferation within the tumors. L1-directed antibody-based inhibition of peritoneal growth and dissemination of human ovarian carcinoma cells represents important proof-of-principle for the development of a new therapy against one of the leading gynecologic malignant diseases. (Cancer Res 2006; 66(2): 936-43)