Abstract A037: The impact of cell-matrix interactions on the chemoresponse of breast cancer cells
Authors: Moore Elizabeth S. , Shimpi Adrian A. , Tan Mathew L. , Fischbach Claudia 
Published: November 2024

Abstract
Increased deposition of collagen-rich, fibrotic extracellular matrix (ECM) is a risk factor for mammary cancer and contributes to aggressive drug-resistant phenotypes. However, it remains unclear how tumor cell interactions with collagen modulate responses to chemotherapy, due in part to a lack of relevant model systems. Using engineered cell culture platforms in which ECM composition and mechanical properties are tunable, we have shown that ECM physicochemical properties modulate breast cancer cell growth and response to genotoxic chemotherapy. Triple negative MDA-MB-231 cells grown in 3D collagen have reduced sensitivity to the DNA crosslinker mitomycin C (MMC) and the topoisomerase inhibitor doxorubicin, but similar sensitivity to ionizing radiation as cells plated on 2D collagen as assessed by live/dead staining and flow cytometry. Given the link between the ECM and drug resistance, we evaluated the impact of collagen on the DNA damage response (DDR) of breast cancer cells. MDA-MB-231 cells grown in 3D fibrillar collagen have transcriptional signatures of altered DDR as assessed by bulk RNAseq. Growth in 3D collagen is associated with an increased percentage of tail DNA in the COMET assay, indicative of increased DNA damage and strand breaks, and increased 53BP1 foci in G0/G1 phase cells assessed by immunofluorescence and confocal microscopy, suggestive of persistent damage from the prior replication cycle, relative to cells plated on 2D collagen. Replicative cells plated in 3D collagen have a higher fold increase in MMC-induced phosphorylation of the DDR kinase ATM and expression of the DNA damage marker ƴH2AX relative to cells plated on 2D collagen as assessed by immunofluorescence. These data indicate that growth in 3D collagen alters the DDR of MDA-MB-231 breast cancer cells. We are investigating which cell-matrix interactions and matrix characteristics mediate these phenotypes and the 3D collagen-mediated drug resistance mechanisms. Neither the inhibition of focal adhesion kinase signaling, or cell contractility impacts the chemoresistance of 3D plated breast cancer cells; however, inhibiting ECM-degrading matrix metalloprotease (MMP) activity partially restores the chemosensitivity of 3D plated breast cancer cells. Using a fluorescently labeled 3D fibrillar collagen (DQ collagen), we have observed that 3D plated MDA-MB-231 cells display increased matrix degradation and uptake upon genotoxin exposure using flow cytometry. The physical structure of 3D collagen appears required for the chemoresistance phenotype, as provision of soluble collagen does not induce chemoresistance of 2D plated breast cancer cells. We are currently exploring the potential mechanistic connection between enhanced MMP activity in 3D plated breast cancer cells upon genotoxin exposure and their chemoresistance.
Citation Format: Elizabeth S. Moore, Adrian A. Shimpi, Mathew L. Tan, Claudia Fischbach. The impact of cell-matrix interactions on the chemoresponse of breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A037.