(174j) In Vitro Modeling of 3D Breast Cancer and Primary Keloid Fibroblasts Cell Interactions to Elucidate Changes in Collagen-I Expression and Endocrine Resistance.

Understanding the influence of stromal and immune cells in the tumor microenvironment (TME) is key for comprehending tumor behavior and advancing anticancer drug development. Therefore, there is a growing interest in co-culturing different cell types with cancer cells in vitro to elucidate how cell-to-cell communication between each cell type modulates the TME. Fibroblasts are known for their pivotal role in cancer progression through collagen-I production and extracellular matrix (ECM) remodeling as they have been suspected to contribute to drug resistance by enhancing collagen-I deposition and the stiffening of the ECM. In this study, the distribution of collagen-I within the TME in the presence of primary keloid fibroblasts when co-cultured with an ER⁺ breast cancer cell line in 3D culture were investigated. This analysis was conducted utilizing a microfluidic droplet generator approach coupled with a thiol acrylate (TA) hydrogel scaffold capable of growing and interrogating an array of individual 3D spheroids. Initial observations found the presence of two distinct spatial distributions of collagen-I referred to as ‘hotspots’. One cohort exhibited a single hotspot with diminished collagen I expression, while the second cohort displayed multiple hotspots with enhanced collagen I expression. Cluster analysis was performed to elucidate any correlations between frequency of hotspots, size of the spheroids, and Collagen-I expression. Interestingly, the stratification of the population into these two cohorts did not dependent upon spheroid size which is a unique finding since collagen-I plays role in cancer fibrosis, which often leads to drug resistance, and subsequent hindrances in drug transport into the TME. Because of this, drug studies were performed to determine if resistance to the endocrine therapy, Fulvestrant, is enhanced or diminished in the two different cohorts. This study provides novel insight on the heterogeneous nature of breast cancer and supports the idea that each patient exhibits a personalized response to therapeutics due, in part, the variations in cell-to-cell communication between cancer and stromal cells.