Abstract 2965: Generation of a human breast tissue mimetic organoid model

Purpose: Much effort has been focused on understanding breast cancer tumorigenesis. However, the regulation of human breast cancer development by gene mutations, hormone perturbation, external chemicals, and environmental cues is poorly understood at the molecular and cellular level. Although mouse models have been invaluable in advancing the knowledge of breast cancer tumorigenesis and progression, human breast ex vivo models comprising the breast tissue microenvironment are needed to help elucidate the underlying mechanisms of breast cancer risk factors. Here, we report a new human breast tissue mimetic organoid model. Methods: Fresh human breast tissue specimens from reduction mammaplasty reduction and prophylactic surgeries were cut and digested overnight. The breast microtissue containing stroma components were collected via centrifugation. They were then cultured in 3D using a matrix mixture containing Matrigel, collagen I, and specially formulated organoid medium. Using culture inserts, a “sandwich” method was utilized, in which we added 1 layer of matrix mixture, followed by 2 layers of organoids and matrix mixture, and a final layer of matrix mixture. Imaging analyses, including immunohistochemistry, immunofluorescence, and highly-multiplexed CODEX imaging, were used to study cellular marker expression in the organoids. Results: Our 3D culture system is distinct from previous models that reconstitute 3D mammary microstructures using isolated individual cell populations and is capable of growing patient-derived breast organoids for 3 weeks and longer. Via CODEX imaging we spatially localized more than 25 antigens for different cell types, allowing us to produce detailed characterizations of the organoid microarchitecture. Breast tissue microstructures with ducts and lobules along with stromal cell types normally found in the human breast are present. For the first time, we found that different stromal cell types grow alongside the mammary epithelium in the organoid system. The cultured breast organoids are hormone responsive and can be subcultured. We also found that BRCA1 mutant organoids are more sensitive to estrogen and progesterone treatment compared with BRCA1 wildtype, as indicated by organoid size changes. Furthermore, BRCA1 mutant organoids display unique gene expression profiles related to oxidative stress and DNA damage response. Conclusion: We have developed a 3D human breast tissue mimetic culture model that phenocopies the breast tissue microenvironment. This model will serve as the foundation for refining a breast organoid system that can faithfully recapitulate the physiology of human breast tissue. It will pave the way for a novel screening system that will test the pathogenic effects of breast cancer risk factors, providing a useful tool for elucidating the biological mechanisms of breast cancer tumorigenesis. Citation Format: Tian-Yu Lee, Nadya Nikulina, Srivarshini C. Mohan, Edward Ray, Armando Giuliano, Oliver Braubach, Xiaojiang Cui. Generation of a human breast tissue mimetic organoid model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2965.