Organoid cultures are being explored as intermediate preclinical models in numerous cancer types including colon, liver and brain. Recently it has been demonstrated that organoids can be robustly isolated and cultured from breast cancer subtypes, that they maintain the histological, genomic and transcriptomic signatures of the primary tumor tissue, and that ER expression can be preserved (Sachs et al, 2018). The Institute for Precision Medicine (IPM), a collaboration between UPMC and the University of Pittsburgh initiated a program to develop breast cancer organoids in 2018. The IPM works closely with surgeons to consent patients with primary or metastatic breast cancer for tissue collection, and with an institutional biospecimen core for tissue procurement and deidentification. The IPM receives fresh, deidentified tissue typically within 60 minutes of the patient’s operation. Based on the protocol by Sachs et al, to date we have established 49 organoids from a total of 60 tumor samples received from patients undergoing resection of their primary or metastatic breast tumor, resulting in a success rate of 82%. Our current collection includes organoids from 17 treatment-naïve invasive ductal carcinomas, 12 treatment-naïve invasive lobular carcinomas, 10 primary tumors excised after neoadjuvant therapy and 5 from breast cancer metastasized to bone or ovary. Our organoids demonstrate a range of growth morphologies, consistent with those previously described. ER expression can be detected in a subset of our cultures as well as robust response to estradiol as indicated by the induction of GREB1 gene expression. We have further demonstrated that organoids are amenable to transient transfection of siRNA and lentiviral infection of reporter constructs which allows for RFP and luciferase-based detection of cells both in vitro and in vivo as well as expression of genes of interest. We additionally recognized that some of our organoid cultures can give rise to suspension cultures when maintained in organoid culture medium but without 3D matrix. This observation allows the opportunity for further phenotypic evaluation by increasing the number of assays amenable to these unique patient derived cultures. Single cell RNA sequencing (10X Genomics) of organoid cultures and paired tumor tissue confirms that organoid cultures faithfully maintain the heterogeneity of epithelial subpopulations found in the surgically resected tumors. Further, organoids show greater epithelial diversity and heterogeneity compared to single cell sequencing of breast cancer cell lines. We have further used sequencing data to identify targetable pathways in individual organoid cultures and demonstrate that drug sensitivity can be correlated with gene expression in these models. Collectively, these data indicate that breast cancer organoids represent a valuable model for preclinical breast cancer research.

Citation Format: Daniel D Brown, Kai Ding, Fangyuan Chen, Jian Chen, Brian Orr, Sarah Taylor, Kurt Weiss, Steffi Oesterreich, Peter C Lucas, Priscilla F McAuliffe, Jennifer M Atkinson, Adrian V Lee. Development of a breast cancer organoid resource faithfully representing epithelial heterogeneity and drug response [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-23.