In vitro characterization of cancer cell morphology, chemokinesis, and matrix invasion using a novel microfabricated system
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A diagnosis of metastatic cancer reduces a patient's 5-year survival rate by nearly 80% compared to a primary tumor diagnosed at an early stage. While gene expression arrays have revealed unique gene signatures for metastatic cancer cells, we are lacking an understanding of the tangible physical changes that distinguish metastatic tumor cells from each other and from their related primary tumors. At the fundamental level, this translates into first characterizing the phenotype of metastatic cancer cells in vitro both in 2D – looking at morphology and migration – and in 3D – focusing on matrix invasion. While 2D in vitro studies have provided insight into the effects of specific environmental conditions on specific cancer cell lines, the unique details included in each experimental design make it challenging to compare cell phenotype across different in vitro platforms as well as between laboratories and disciplines thatshare the goal of understanding cancer. While 3D phenotype studies have employed more standardized and ubiquitous assays, most available tools lack the imaging capability and geometry to effectively characterize all factors driving 3D matrix invasion. In this work, we present protocols and platforms aimed at addressing the problems identified in the tools currently available for studying metastatic cancer in vitro. First, we present a 2D study of morphology and migration using widely accepted protocols. The study is applied to characterizing phenotypes of three breast cancer cell lines with different metastatic organ tropisms. The results show that general populations of cells from each of the 3 lines are unique in shape and motility despite being derived from the same tumor line and that the observed phenotype differences may be related to differences in focal adhesion assembly. More broadly, these studies suggest that standardizing phenotype studies using commonly available techniques may provide a platform by which to compare phenotypic studies across cancer cell types and between research groups to investigate tropism-specific cancer phenotypes. We conclude our investigation of phenotype with a study of 3D matrix invasion using a novel microfluidic platform. The results show that invasion of metastatic breast cancer cells into a 3D type I collagen gel is significantly enhanced in the presence of live endothelial cells. In applying the model to study cell-cell and cell-matrix interactions driving invasion, our platform revealed that, while the fibronectin-rich matrix deposited by endothelial cells was not sufficient to drive invasion alone, metastatic breast cancer cells were able to exploit a structural or secreted component of energetically inactivated endothelial cell to gain entry into the underlying matrix. These findings have important implications for designing drugs targeted at preventing cancer metastasis. The findings in this dissertation reveal significant phenotypic differences in metastatic breast cancer cells with different preferences in metastatic target organ. In addition, the microfluidic platform reveals novel cell-cell interactions driving a key step in the seeding and colonization of a metastatic tumor. Collectively, these results reveal important characteristics of metastatic cancer cells and their interactions with other cell types during metastasis. These studies also provide platforms on which to target or prevent malignant phenotypes and cellular interactions in the future.