RGBs have both tumor promoting and vascular effects;however, little is known about their influence on the development of metastatic disease. We indicated that selected non-coplanar PCB congeners accumulate in the brain, stimulate dysfunction of brain microvascular endothelial cells (BMEC), and facilitate the interaction of tumor cells with the vascular endothelium. Our new data provide evidence that PCBs localize to caveolae in endothelial cells. This is an important finding because a variety of cell surface receptors and signaling pathways are also localized in these membrane domains. Thus, caveolae may provide the crucial signaling platform for cerebral vascular toxicity of PCBs. We hypothesize that PCB-induced stimulation of caveolar-associated pathways, such as the Ras and Rho cascades, underlie the mechanisms of PCB-induced injury to BMEC, disruption of the bloodbrain barrier (BBB) integrity, and the development of brain metastases. Mechanistically, we will focus on the involvement of the Ras and Rho pathways in PCB-induced alterations of expression of tight junction proteins, which are associated with caveolae and are detrimental for the normal functions of the brain endothelium and regulate the barrier properties of the BBB. Diet is one of the most powerful modifiable behavioral factors which can influence cancer development and progression. Moreover, our data indicate that exposure to PCBs can upregulate expression of CD36, a receptor which is localized in caveolae and is involved in cellular uptake of fatty acids. Therefore, we will also study the influence of dietary polyunsaturated fatty acids (namely fatty acids of the omega-6 and omega-3 family) on the vascular toxicity of PCBs and PCB-induced brain metastases. Specifically, we hypothesize that omega- 6 fatty acids (e.g., linoleic acid) potentiate the pro-metastatic properties of selected PCBs and that omega-3 fatty acids (e.g., alpha-linolenic acid) protect against these effects. The proposed research combines elements of clinical and translational approaches (brain metastases) with environmental toxicology and molecular biology. In addition, it is based on a variety of model systems, such as unique cultures of brain endothelial cells, Transwell systems, and in vivo studies based on genetically altered mice (caveolin-1 deficient mice). The long term goals of this application are to determine molecular mechanisms of metastatic events induced by PCBs. However, an even more important goal of this proposal is to evaluate how dietary factors can influence the development of tumor metastases induced by Superfund chemicals. Therefore, our application has strong clinical implications and can significantly contribute to the improvement of public health.
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