Our major research goals in this project are to characterize the roles of cell interactions with the extracellular matrix and exogenously added extracellular molecules in pathogenesis. One major focus is on tumor cell invasion and metastasis, with a goal of identifying novel molecular regulators and mediators. A fundamental question in cancer biology is the relationship of the local matrix environment to cancer progression. For example, a common feature of advanced carcinomas is the induction of a dense collagenous matrix surrounding tumors during the process of desmoplasia. After completing studies establishing the role of dense fibrillar collagen in induction of proteolytically active invadopodia, we have turned to the question of how alterations in the physical rigidity of the matrix substrate can alter the nature of cell migration by a variety of human tumor cell lines. For quantifying a variety of parameters of cell migration, a non-biased, automated computer-based system has been developed that uses algorithms for video fluorescence microscopy tracking of Hoechst-labeled nuclei of a variety of tumor cell lines to provide rapid quantification of speed, persistence, and durotactic migration. This program termed FastTracks was developed using MATLAB software; after final publication, however, it can be downloaded for use on regular computers without proprietary software. Tumor cell invasiveness may be promoted by epithelial-mesenchymal transition (EMT). In studies of normal tissue morphogenesis, we identified the novel regulator Btbd7 as an inducer of the EMT transcription factor Snail2 and a disruptor of E-cadherin mediated cell-cell adhesion. We are currently evaluating whether Btbd7 or fibronectin, its upstream extracellular matrix regulator, can play a role in the invasiveness of certain tumor cells. Molecular interactions at the cell surface with soluble or matrix factors are likely to play important roles in many diseases. We have continued a long-term collaboration with Dr. Subhash Dhawan in CBER, FDA to characterize cell-surface and extracellular interactions involved in the pathogenesis or suppression of infectious diseases. Some molecules are found to enhance infectivity, while others can suppress this process. For example, the host cellular response to extracellularly provided hemin, an inducer of heme oxygenase-1 (HO-1), elicits host protective responses against viral infections including HIV and poxvirus. This collaborative project has recently been extended to explore and to document the effectiveness of inducing HO-1 mediated host responses to suppress Ebola and Zika virus infections. Since hemin is an FDA-approved drug, its induction of HO-1 might provide a potential general host-defense therapeutic strategy against a variety of pathogens. Specifically, we established that Zika virus can infect primary human monocyte-derived macrophages. Hemin dramatically reduced Zika virus replication in vitro. Hemin induced HO-1 expression and produced major reductions of >90% in Zika virus replication in human macrophages and LLC-MK2 monkey kidney cells with minimal toxicity. RNAi silencing of the expression of HO-1, or of its upstream regulatory gene Nrf2, attenuated hemin-induced suppression of Zika virus infection. Hemin, an FDA-approved drug for an unrelated disease (porphyria) may provide a useful therapeutic approach based on its ability to stimulate an innate cellular response against Zika virus infection. In a multi-site collaboration that extended beyond the FDA to include the Molecular and Translational Sciences Division of the United States Army Medical Research Institute of Infectious Diseases at Frederick and the Department of Medicine at Howard University, we tested whether hemin could inhibit Ebola virus replication through induction of HO-1. Treatment of not only primary monocyte-derived macrophages (MDM), but also Vero cells, HeLa cells, and human foreskin fibroblasts, reduced Ebola virus infection by >90% with minimal toxicity to infected cells. Inhibition of HO-1 enzymatic activity and RNAi silencing of HO-1 expression prevented this hemin-mediated suppression of Ebola virus infection. Consequently, re-purposing hemin to stimulate the innate HO-1 cellular response may provide an alternative approach to help alleviate Ebola virus infection. Because we have extensive expertise in real-time imaging of cell behavior in vitro and in organ explants, we have initiated a collaboration with Dr. Ashok Kulkarni's laboratory to use the GCaMP6 mouse system for direct visualization of calcium signaling for characterizing pain signaling in the mouse trigeminal ganglion.
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