UC San Diego

In the United States, cancer is the second leading cause of death only to be surpassed by heart diseases (1). Within 2016, an estimated 1.6 million new cases of cancer will be diagnosed and approximately 0.6 million individuals will die from this disease (1). The survival rate of individuals afflicted with cancer have increased over the years due to early detection and increased fundamental understanding of this disease. However, the complex nature of cancer exceeds the current capacity to recapitulate its features in vitro. Additionally, the animal models that have been relied upon within the field of oncology may not be translatable to the human counterpart (2-5). In this dissertation, I have created novel in vitro technological platforms focusing on specific aspects of cancer progression to identify the underlying biological phenomena and recapitulate the physiological cancer microenvironment to provide better alternatives for cancer drug screening.

Chapter 1 is a literature review focusing on cancer cell migration during metastasis and in vitro platforms used to model the cancer microenvironment. Specifically, I have focused on the role of the extracellular matrix (ECM) network on modulating the protease dependent or independent mode of migration during cancer metastasis. In vitro systems used to study cancer cell metastasis within 3D matrices are also briefly reviewed. Next, I have described the use of organ-on-a-chip technology as the next generation platforms towards creating low cost, efficient, and realistic tumor models for screening of oncologic drugs. Lastly, I have summarized the emergence of a potent cancer treatment, immunotherapy, and its mechanism through the immune cells within the tumor environment are activated to eliminate cancer. Furthermore, I have discussed the crucial role of cytotoxic T-cells in immunotherapies and the means by which they are recruited to the tumor stroma.

Studies have implicated the physical cues of the cancer microenvironment in modulating the particular mode of migration. In Chapter 2, I have investigated how these various cues activate an intracellular “trigger” to dictate a cell’s mode of invasion. I have developed a novel single cell invasion assay to quantitatively investigate the interplay between cell generated traction forces and protease activity during cancer cell invasion into basement membrane-like extracellular matrix (ECM) network. Within these studies, I observed the translocation of a crucial membrane bound protease, MT1-MMP, from the cytoplasm to the cell surface to degrade the surrounding ECM network. Chapter 3 further investigates the transport pathway through which this translocation occurs. The results from this study implicate a regulated secretory pathway known as CARTS that is necessary for MT1-MMP transport and the protease dependent invasion of cancer cells into an ECM network. In addition to understanding cancer cell metastasis, I next shifted my research focus towards recreating the cancer microenvironment to test the efficacy of cancer drugs. Chapter 4 describes the development a state-of-the-art 3D tumor-on-a-chip platform containing cancer and endothelial cells to assess the penetration and efficacy of cancer drugs. Here, I have used a morphogen gradient to induce the self-assembly of an endothelial and cancer cell mixture resulting in a tumor mass enveloped by a vascular barrier. The drug screening capacity of this system was assessed using doxorubicin as a model drug. Current immunotherapies rely on the presence of cytotoxic T-cells within the tumor microenvironment to eliminate cancer cells. In Chapter 5, I have adapted the tumor-on-a-chip device to incorporate immune cells to recapitulate cancer-immune interactions and investigate its effect of recruitment of T-cells into the engineered microenvironment. In the last chapter, I have discussed the future directions in which these platforms can be directed towards to better understand cancer-immune interactions and improve future immunotherapies.