Microenvironmental Regulation of Tumor-Derived Exosomes using a Tissue-Engineered Model

Cancer cells are typically studied in monolayers that do not provide the 3-dimensional microenvironment and signaling present in native tumors. The lack of specific cell-matrix interactions and stiffness of the substrate lead to changes in many cancer cell processes, including endo- and exocytosis. In recent years, there has been an increased interest in understanding how exosomes modulate the cancer cell microenvironment, after the discovery of their role in the pre-metastatic niche formation in the lung. However, despite the well-established importance of the microenvironment for cancer cell behavior, supernatants from monolayer cultures still represent the major source for isolation of tumor-derived exosomes, such that their microenvironmental regulation remains largely unknown.

Bioengineering methods that have transformed the stem cell research and regenerative medicine are just starting to enter the field of cancer research. Our lab is making progress in replicating the physiological landscape of human tumors using 3-dimensional in vitro tissue models that contain the essential components necessary for recapitulating in vivo conditions. Here, we report the effects of the tumor microenvironment on exosomes, using a bioengineered tumor model of Ewing’s sarcoma as a clinically relevant example. To this end, we cultured cancer cells on 3-dimensional scaffolds that were designed to mimic the biological and mechanical properties of the native tumor. Our data confirm the role of the extracellular matrix in regulating tumor-derived exosomes and provide compelling evidences for a link between the stiffness, 3-dimensionality and composition of the environment and the size of exosomes. Notably, the size of exosomes released from the bioengineered tumor models were indistinguishable from those secreted into the plasma of patients, and significantly smaller than those secreted from cancer cell monolayers.