Investigating Fibroblast Activation State and Phenotype in Tumor Co-culture Models

Abstract

Fibroblast cells in the tumor microenvironment play a role in cancer cell growth, progression of invasion, and secretion of extracellular matrix components, cytokines, and growth factors. Characterizing fibroblast subsets in the tumor microenvironment and their different activation states through the use of in vitro models may provide novel opportunities to identify fibroblast-specific anti-tumor therapies. This thesis work addresses the complexities involved in creating a physiologically relevant in vitro model by comparing expression patterns of five fibroblast activation markers (CD29, FAP, PDGFRb, Thy1.1 and Cav-1) in co-cultures with tumor cells in a typical two-dimensional cell culture method to a three-dimensional spheroid model. Markers of fibroblast activation had varying levels of expression in co-cultures with two different breast cancer lines, SKBR3 or MDA-MB-231, which may be reflected in the different morphology of the 3D spheroids. Fibroblasts grown in traditional 2D cultures appeared to be in a more uniformly activated state than 3D spheroid models, suggesting that 3D culture may be a better tool for identifying changes in the tumor microenvironment. The development and use of physiological in vitro models provide opportunities to study the complex roles played by fibroblasts in the tumor microenvironment as well as a system for validating potential targets for anti-tumor therapies.