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Most methods available to study the behavior of metastatic tumor cells are indirect or capture only brief periods. Problematic with these assays are an inability to follow the complete metastatic program including extravasation, invasion, establishment and growth of the metastatic mass. As such, have developed an ex vivo model in which tumor cells can be analyzed while in the environment of a major metastatic target, the liver. In order to accomplish this we utilized a three dimensional liver perfusion culture (bioreactor), which allows for in situ observation and ensures a relatively homogeneous distribution of flow and mass transfer throughout the system to meet the metabolic demands of the livers cells augmented by an appropriate scaffold which facilitates morphogenesis of primary cells into tissue-like structures. This system, formally named a Micro-fabricated Array Bioreactor, affords for the recreation of an in vivo environment for in vitro observation in real-time and provides for an optimal device for the study of physiological events. GFP hepatocytes and nonparenchymal liver cells were obtained and introduced into the bioreactor utilizing established protocols. After allowing 5 days of observed hepatic tissue morphogenesis, DU-145 human prostate carcinoma cells expressing RFP were introduced into the bioreactor. In situ observation of the co-culture system was observed by 2-photon microscopy over a 14 day period. Fluorescent intensity of co-cultures revealed ongoing cell proliferation of the DU-145 cells, which correlated with a visually observed overgrowth of DU-145 cells by 14 days. These tumors often become visible with naked eye by day 25 with intact cellular structures and no evident necrosis throughout when examine with TEM. The DU-145 cells failed to grow in the absence of the hepatocytes, suggesting a paracrine or stromal support function for the liver bioreactor in tumor progression. The overt tumor mass resulted in a decline in hepatocyte tissue structure and function. TEM also revealed DU-145 RFP cells invading the hepatocyte parenchyma by 14 days with very distinct cell-cell interaction. This interaction was further characterized in 2D cultures of GFP hepatocytes and RFP prostate cancer cells with increase in E-cadherin staining of clusters compared to respective cell types alone. Finally, in vivo invasion of prostate cancer into the liver revealed increased E-cadherin staining as well. These experiments provide the basis for the development of an ex vivo model system to dissect cellular behavior during the dynamic process of tumor invasion and metastasis.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]