Abstract 4708: Investigating triple negative breast cancer phenotypic heterogeneity of human and patient-derived xenograft samples using imaging mass cytometry

Abstract

Abstract Tumors are highly heterogeneous populations of cells, and measures of intratumoral heterogeneity (ITH) and diversity correlate with worse prognosis in many cancers, including breast cancer. Emerging studies are highlighting functional interactions between subclones, as well as among subclones and components of the tumor microenvironment. However, these studies have largely focused on soluble factors without interrogating the spatial distribution of subclones defined by activated signaling pathways. Previous work in this area has been severely limited by technical restrictions - existing techniques allowing measurement of many biomarkers simultaneously lose all information about the tissue architecture, while those that do retain spatial information can only assay a handful of markers at once. We will circumvent these limitations by undertaking imaging mass cytometry (IMC), which allows for simultaneous measurement of 30-40 antigens while retaining the spatial organization of the sample. Our objective is to dissect the signaling heterogeneity in tumors from patients and patient-derived xenograft (PDX) models of triple negative breast cancer (TNBC), through two main approaches: (1) characterization of signaling heterogeneity in tissue microarrays of human tumors and PDX models of TNBC with IMC and (2) modeling cell signaling heterogeneity in cell line-based models to determine mechanisms of cell-cell interaction and communication. We have constructed an IMC panel of antibodies that combines markers for tissue architecture, tumor and immune cell phenotyping, and signaling pathway activation. Profiling of a diverse panel of TNBC PDX models captures the heterogeneity of human TNBC. Analysis of distinct regions within individual PDX tumors demonstrate unique compositions of cell phenotypes between the edge and core of the tumor. Our PDX collection also includes sequential pairs derived from biopsies taken before and after chemotherapy treatment. Comparison of the pre-/post-chemotherapy pairs indicates emerging patterns of pathway activation. Interestingly, while the tumor cells from these models exhibit distinct phenotypes, the stromal cells are largely indistinguishable from one another, suggesting that these models are capturing tumor cell-intrinsic changes associated with chemotherapy response. Ultimately, we plan to use these results to identify novel vulnerabilities in subclonal interactions that can be targeted therapeutically in TNBC. Citation Format: Amanda L. Rinkenbaugh, Vidya C. Sinha, Xiaomei Zhang, Jiansu Shao, Helen Piwnica-Worms. Investigating triple negative breast cancer phenotypic heterogeneity of human and patient-derived xenograft samples using imaging mass cytometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4708.