Engineering Tumor Constructs to Elucidate the Impact of Microenvironment on Tumor Angiogenesis and Metastasis

Abstract

Breast cancer is the leading cause of cancer deaths among females globally. Although localized or early stage cancer is largely curable, the five-year survival rate significantly decreases after metastasis. The crosstalk between tumor microenvironment and neoplastic cells is the key for promoting tumor growth and stimulating tumor angiogenesis and metastasis to distant organs. In the first section of this study, the effect of stromal stiffening on the angiogenic activity of cancer cells was explored. Highly aggressive breast cancer cells, MDA-MB-231, displayed an increased expression of pro-angiogenesis-related signals when encapsulated in stiffer collagen matrices. In comparison, less-invasive cells, MCF-7, showed a minimal change in the release of angiogenic signals when cultured on stiffer matrices. Inhibition of mechanotransduction pathways on the angiogenic activity of aggressive tumor cells in stiff matrices was investigated using Y- 27632, Blebbistatin, and Cytochalasin D. Rho associated kinase (ROCK) inhibitor, Y-27632, diminished the pro-angiogenic signal release, thereby suggesting the potential dependence of breast cancer cells on the Rho/ROCK pathway in regulating tumor angiogenesis. Breast cancer cells most commonly metastasize to lungs, liver, and brain, with preferential metastasis to bone tissue. Initial stages of bone metastasis are not well understood, but studies suggest that the host microenvironment is manipulated into allowing the tumor cells to invade and proliferate at bone sites. In the second section of this study, the effect of microenvironment on bone metastasis was studied. Mesenchymal stem cells (MSCs) were differentiated into osteoblasts, and the deposited matrices were decellularized. The key components of the deposited extracellular matrix (ECM) were characterized. Furthermore, the effect of the decellularized ECM (dECM) on the activity of breast cancer cells was investigated. In the presence of dECM, MDA-MB-231 cell proliferation increased, and the efficacy of anti-cancer drug, 5-fluorouracil, on the cancer cells was reduced.