Abstract 768: Modeling the triple-negative breast cancer extracellular matrix in a 3d tumor scaffold.

Abstract Breast Cancer is the second leading cause of cancer death in women and incidence rates are increasing 0.5% per year. Triple negative breast cancer (TNBC), which is classified by negative hormone receptors (HR-), progesterone and estrogen, and human epidermal growth factor receptor 2 (HER2) negative, is the most aggressive subtype and occurs more often in younger Black and Hispanic women. TNBC, compared to other subtypes, is difficult to treat due to the treatment response rate of 30%. Neoadjuvant chemotherapy is the standard treatment for TNBC. This is attributed to the lack of preclinical models that allow multi-cellular interactions in the highly heterogenous nature of TNBC. Due to this, there is a critical need for 3D TNBC tumor models that recapitulate the complex extracellular matrix (ECM). Most ECM-cancer studies focus on collagen I (COL1); however, COL1 is not a prognostic marker for TNBC and is often not observed to be elevated in TNBC. Evaluation of ECMs overexpressed in a primary TNBC tumor compared to adjacent adipose demonstrated elevated ECM protein expression. To determine the impact of distinct ECMs in TNBC breast cancer progression, we explored changes in ECM protein expression (MFAP5, FN1, and POSTN) in TNBC cell lines and fabricated matrix for in vitro systems. qRT-PCR and RNA sequencing, genes associated with epithelial-to-mesenchymal transition and inflammation were significantly upregulated in ECM-OE expressing cells in 2D culture. Next, we created 3D models of TNBC ECM through the fabrication of ECM matrix coated cell culture plates (COL1, FN1, and POSTN) and 3D scaffolds using bioinert fish gelatin methacrylol (fgelMA). Taken together, this work identifies ECM proteins - MFAP5, FN1, and POSTN - attribute to TNBC proliferation and survival through epithelial to mesenchymal transition. Overall, our results establish an extracellular signature for the triple-negative tumor type while also demonstrating fabricated 3D ECM models can be used to advancing the development of potential treatments for TNBC. Citation Format: Katherine Hebert, Thomas Cheng, Sophie Dietrich, Mackenzie Hawes, W. Todd Monroe, Jorge Belgodere, Elizabeth Martin. Modeling the triple-negative breast cancer extracellular matrix in a 3d tumor scaffold abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 768.