Engineered approaches to querying the microenvironment of cancer metastasis

Abstract

Cancer metastasis is the underlying mechanism of 90% of cancer-related deaths, yet few therapeutics exist that directly target it. Part of this scarcity is attributable to a general lack of knowledge with regards to the underlying mechanisms that mediate traversal of the sequential steps required for malignant dissemination. Recently, biologists and clinicians have gained appreciation for the role that the microenvironment plays in promoting or inhibiting metastasis. This thesis sought to expand our understanding of the involvement of extracellular matrix (ECM) interactions during metastasis through the development and use of a novel ECM microarray screening platform. This platform consists of 768 unique single and pairwise combinations spotted in quintuplicate as 150pm features onto polyacrylamide coated glass slides. Cells are seeded onto these arrays and queried for their adhesion, proliferation, and marker expression using automated fluorescence microscopy in conjunction with automated cell counting and image analysis. In the first part of this thesis, this platform is used in conjunction with a mouse model of lung adenocarcinoma metastasis (KraLSL-G12D/+; p53flox/flOx) where distinct stages of metastasis are defined by characteristic cell lines derived from these mice. Hierarchical clustering of the adhesion profiles revealed conserved alterations in ECM adhesion signatures that correlate with metastasis. Additionally, they identify a role for combinations of ECM composed of fibronectin with any of galectin-3, galectin-8, or laminin. In the next part of this thesis, these molecules are investigated for their involvement in mice bearing the autochthonous tumors or in humans with lung cancer. The integrin Q3p1 is found to mediate adhesion to the fibronectin-galectin combinations in vitro and promote metastasis in vivo. Subsequently, this thesis investigates the role of carbohydrate-mediated interactions in promoting galectin adhesion. The oncofetal T-Antigen glycan motif is found to be increasingly expressed on cells with elevated metastatic potential, and is found to be the result of aberrant glycosyltransferase activity. Finally the role of galectin-3 in the metastatic niche and its presentation on bone marrow derived cells recruited to tumors is investigated. The results of this thesis suggest a role for novel phenotypic screening platforms in investigating regulation of the cancer microenvironment. Additionally, we extend these studies to the role of ECM in the epithelial-mesenchymal transition (EMT) and lay the groundwork for the development of nanoparticle-based therapeutics targeting the conserved glycan-ECM interactions. Such technologies will likely prove useful to study other disease mechanisms as well as identify novel biomarkers.