Abstract 6772: A 3D model of breast cancer-bone metastasis to mimic dysregulation of bone remodeling and drug response
Authors: Tai Michelle , González Díaz Eva C. , Monette Callan E. , Wu Joy , Yang Fan 
Published: March 2024

Abstract
Introduction: Bone metastases are common among advanced stage breast cancer patients and induce dysregulation of bone remodeling. Crosstalk between cancer cells and the bone niche drives the vicious cycle of bone loss and breast cancer growth. To accelerate discovery of targeted therapies, there is a critical need for experimental models that can mimic breast cancer-induced dysregulation of bone remodeling in patients. Mouse models are the current gold standard, but are low throughput, costly, and cannot fully recapitulate human-human cell interactions. To address these limitations, our goal is to engineer a fully human 3D in vitro model of breast cancer-bone metastasis that can mimic dysregulation of bone remodeling and drug responses in patients, and enable screening of potential new drug candidates.
Methods: Two human breast cancer cell lines (MDA-MB-231, MCF-7) were chosen given their well characterized clinical features and tendency to invade bone. Our 3D model comprises an outer ring of tissue engineered (TE) bone and a center of breast cancer cells to mimic invasion through the bone marrow/long bone interface. Human mesenchymal stem cells were encapsulated in 3D gelatin microribbon scaffolds and cultured in osteogenic media for 28 days to form TE bone. Human monocyte-derived osteoclasts were seeded onto the bone, and the center was replaced with GFP-labeled breast cancer cells. Denosumab and zoledronic acid were selected as they are standard treatments for reducing bone loss in patients, and were used to treat the model at 30 µg/mL and 2 µg/mL, respectively. Intermittent parathyroid hormone (iPTH) treatment was selected as it showed efficacy in animal models, and was used to treat the model at 10 µg/mL for 6 hours daily. All groups were treated with drugs for 14 days. Bone volume was assessed using microCT. Cancer cell proliferation and invasion into bone was monitored with fluorescence confocal microscopy.
Results: MicroCT imaging showed both breast cancer cell lines induced bone loss in the triculture model, compared to the control with no breast cancer cells in the center. Consistent with known clinical features, the more aggressive cell line (MDA-MB-231) induced a greater amount of bone loss than the less aggressive breast cancer cell line (MCF-7). Consistent with clinical findings, both denosumab and zoledronic acid reduced bone loss in our 3D model, and zoledronic acid further reduced breast cancer cell invasion and proliferation. Finally, the 3D model recapitulated the in vivo drug response of iPTH treatment, reducing bone resorption and breast cancer invasion.
Conclusions: Here we report a fully human triculture model of breast cancer-bone metastasis that can mimic key clinical features of breast cancer-induced bone resorption and drug response in patients. Such a 3D model could enable screening of drug candidates with reduced time and cost and enable identification of novel druggable targets.
Citation Format: Michelle Tai, Eva C. González Díaz, Callan E. Monette, Joy Wu, Fan Yang. A 3D model of breast cancer-bone metastasis to mimic dysregulation of bone remodeling and drug response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6772.