CT-1746

Development of metastases requires cancer cells to breach underlying basement membrane, migrate through interstitial stroma and gain access to blood or lymphatic vessels. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been linked with these processes. Expression of MT1-MMP in human prostate cancer correlates with the stage of this disseminated disease. The mechanism underlying this observation, however, still remains to be understood. To study the role of MT1-MMP in prostate cancer dissemination, endogenous and recombinant MT1-MMP expressed in human prostate cancer cell lines (DU-145 and LNCaP) were examined. Using FITC-labeled Ma-trigel, a soluble basement membrane extract coated coverslips, LNCaP cells stably expressing a chimera of MT1-MMP and Green Fluorescent Protein (MT1-GFP) degraded Matrigel and readily migrated over degraded substrates. The degradation of Matrigel by LNCaP cells expressing MT1-GFP was sensitive to MMP inhibitors, CT-1746 and TIMP-2, but not TIMP-1. Cell migration was dramatically enhanced by expression of MT1-MMP. By employing surgical orthotopic implantation of LNCaP cells stably expressing MT1-GFP into the prostate gland of immunodeficient mice, we demonstrated that MT1-MMP promotes lymph node and lung metastasis of prostate cancer cells. Together, these results emphasize the pivotal role of MT1-MMP in prostate cancer dissemination and confirm that MT1-MMP is a suitable target to prevent cancer metastasis.

It has been suggested that functional heterogeneity exists between osteoclasts from different bone sites. This could be exploited to design therapeutics that would selectively inhibit bone resorption only at compromised sites. To further investigate the existence of functional differences between osteoclasts from different bone sites we assessed whether osteoclasts isolated from intramembranous bone differ from osteoclasts isolated from endochondral bone in the extent that they utilize cysteine proteinases and matrix metalloproteinases to degrade the organic matrix of bone. The differential involvement of the two classes of proteases was assessed by analyzing dose-dependent effects of the matrix metalloproteinase inhibitor, CT-1746, and of the cathepsin inhibitor, E64, on bone resorption. Osteoclasts isolated from the scapula (intramembranous) and long bones (endochondral) of newborn New Zealand white rabbits were seeded on cortical bovine bone slices in the presence or absence of inhibitors. Resorptive activity was evaluated by measuring the number and area of resorption pits and by measuring the release of collagen degradation products in the culture medium. In the absence of inhibitors, scapular osteoclasts and long bone osteoclasts had similar activity based on these criteria. The resorptive activity of scapular osteoclasts was inhibited to a greater extent by the MMP inhibitor CT-1746 than by the cysteine proteinase inhibitor E64. Conversely, resorption by osteoclasts derived from long bones was inhibited to a greater degree by the cysteine proteinase inhibitor. These results strongly suggest that there are functional differences between dispersed osteoclasts derived from the scapula and long bones, with scapular osteoclasts utilizing matrix metalloproteinases to a greater extent than cysteine proteinases and long bone osteoclasts using cysteine proteinases to a greater extent than matrix metalloproteinases.