Investigation of How the Tumor Microenvironment Mediates Therapeutic Resistance in Breast Cancer with New 3D Cell Culture Methods

Elucidating how the tumor microenvironment (TME) mediates chemotherapy resistance in breast cancer is essential for developing new therapeutics. The stromal cells are abundant in the TME and a potential target of new therapeutics. The stroma is less likely to develop a drug-resistant phenotype because, unlike cancer cells, they do not readily divide. To probe cancer-stromal relationships in a systematic and experimentally controlled manner, tissue-like in vitro models are needed. This work measured the effect of stromal cells impart on estrogen receptor-expressing (ER+) breast cancer cells dosed with doxorubicin. Specifically, the MCF-7 ER+ breast cancer cell line was co-cultured with three stromal cells: two fibroblasts and one endothelial cell line. The 3D culture method employed supported gel slab (SGS) scaffolds recently developed in our lab. These scaffolds support cell-laden gels in defined volumes. Using the SGS scaffolds, we evaluated co-cultures with MCF-7 cells suspended in an extracellular matrix. A re-imagined 96-well plate was devised and realized to probe the effects of the TME on breast cancer cell responses to doxorubicin, enabling higher throughput studies with the SGS scaffolds. This work's biological outcome demonstrates that density and stromal cell origin have context-specific effects. However, further studies are required to fully characterize these responses at a phenotypic and biochemical level. The technological outcome of this work is a prototype of an SGS scaffold-compatible 96-well plate.