A major research goal in this project is to understand the role of the extracellular matrix in metastasis and invasion, focusing currently on identifying integrin-mediated signaling pathways that regulate tumor invadopodia assembly and function in proteolytic degradation. A fundamental question in cancer biology is the relationship of the local matrix environment to cancer progression. For example, a common feature of carcinomas is the induction of a dense collagenous matrix surrounding tumors during the process of desmoplasia. However, whether this increase in collagen is protective against tumor expansion or actually contributes to cancer pathogenesis is not known. We have been characterizing in depth the effects of extracellular matrix on invadopodia formation, testing a current hypothesis that increased matrix density contributes to cancer pathogenesis. We have been developing two different systems to test this concept: (a) evaluating effects of endogenous desmoplastic 3D matrix from human tumors on invadopodia formation, and (b) using an in vitro system to model this dense collagenous matrix in order to identify novel molecular mechanisms regulating invadopodia formation. We have developed methods to test the capacity of intact, cell-free 3D human tumor matrix on the ability of tumor cells to form invadopodia. This new protocol uses extracted extracellular matrix from cryostat sections of human breast and pancreatic cancers versus normal adjacent tissue. Its development required solving various technical problems to successfully produce intact, cell-free 3D human tissue matrix suitable for testing cell-matrix interactions and performing immunofluorescence analyses. We have also developed a new high-density 2D fibrillar collagen matrix system to try to mimic this dense fibrillar collagen in tumors and are testing its effects on cell signaling and invadopodia formation. Interactions at the cell surface are likely to play important roles in many diseases. We have been involved in a long-term collaboration with Dr. Subhash Dhawan in CBER, FDA to characterize cell-surface and extracellular interactions involved in the pathogenesis of infectious diseases. We have completed a study showing a link between macrophage stimulation via LPS and protection against HIV infection at both entry and viral replication steps, which involves heme oxygenase-1 (HO-1) and elevation of cytokines. This study identifies a novel role for HO-1 in host immune response against HIV infection. This approach was then extended to evaluate HO-1 induction by hemin in a prostate tumor cell line;it inhibited cell proliferation rate and susceptibility of the cells to retroviral infection. We are evaluating efficacy of hemin treatment of human macrophages and its associated HO-1 induction for suppression of infectivity by two other viruses, dengue and West Nile virus, as well as the protozoan parasite Leishmania. We suggest that HO-1 induction might provide a potential host-defense therapeutic strategy against a variety of pathogens. Since protease degradation of extracellular matrix proteins is a common theme in multiple diseases, a possible therapeutic approach would be to use matrix molecules stabilized against proteases, for example to promote resolution of chronic wounds or periodontal disease characterized by excessive proteolysis and destruction of extracellular matrix. We have initiated collaboration with Dr. Nancy Karuri at the Illinois Institute of Technology, who is developing functional fibronectin molecules that are protected from proteases by conjugation with polyethylene glycol polymers.
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