Abstract P1-06-05: Breast cancer organoid cultures preserve intra-tumor heterogeneity and reveal intrinsically resistant phenotypes to standard chemotherapies

Abstract

Abstract Breast cancer intra-tumor heterogeneity contributes to chemotherapy resistance and decreased patient survival, yet no reliable in vitro models exist to study this phenomenon. To address this need we developed an in vitro 3D organoid culture system using primary human breast cancer tissue. A major difficulty in the development of such models is to identify robust in vitro conditions that preserve the breast cancer phenotypes observed in situ. To address this challenge we used quantitative immunofluorescence imaging to compare the cellular phenotypes in the starting tumor tissue with those observed in the tumor organoids cultured in 3D. We utilized a clustering algorithm and utility function to quantitatively assess whether tumor organoids generated in vitro faithfully recapitulated intra- and inter-tumor heterogeneity of the tumor tissue in situ. This approach generated a normalized score that reflects tissue-organoid similarity. To test the sensitivity of our method to overall changes in tissue phenotype we focused on three distinct breast cancer subtypes distinguished by expression of estrogen receptor (ER), progesterone receptor (PR) and amplification of ERBB2/HER2 (HER2). Using our approach, we successfully recapitulated the tumor phenotypes present in ER+, ER+/HER2+ and triple negative breast cancer. We discovered that EGF preserves the TNBC phenotype, whereas AREG is required for recapitulating the phenotype of ER+ and ER+/HER2+ breast cancers. Additionally, our data demonstrate that HER1 ligands drive inter- and intra-tumor heterogeneity. To investigate how intra-tumor heterogeneity contributes to therapy responses we treated organoids with standard agents used clinically to treat each of the distinct subtypes. For all tumor subtypes we observed differential vulnerabilities between patients to drug treatments. Importantly, our analysis identified divergent cellular phenotypes that have various sensitivities to chemotherapies. Taken together, our methodology provides an unprecedented view of intra-tumor heterogeneity and allows for the investigation of chemo-resistance mechanisms. Further, this approach will provide a powerful tool, which will enhance the identification of novel therapies and facilitate personalized medicine. Citation Format: Sowder ME, Ludwik KA, Pasic L, Brenin DR, Stricker TP, Macara IG, Lannigan DA. Breast cancer organoid cultures preserve intra-tumor heterogeneity and reveal intrinsically resistant phenotypes to standard chemotherapies [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-06-05.