Abstract 2010: A spatial profiling approach to evaluating the prognostic impact of heterogeneity in the triple-negative breast cancer immune microenvironment

Abstract Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype with the poorest patient outcomes. The composition and active immune pathways of the immune microenvironment play a critical role in tumor progression. TNBC is frequently characterized by a high and heterogeneous immune infiltration in the tumor stroma. The degree of immune infiltration impacts current management: neoadjuvant chemotherapy and anti-PD1 agent pembrolizumab.1, 2, 3 Previously, our lab studied a treatment-naive cohort of 192 patients diagnosed with TNBC and found that patients with higher B cell infiltration in the stromal regions had better outcomes (Kanwar and Balde et. al, Cancer Res 2021)4. While previous studies employed low-plex methods of analysis to study archival formalin-fixed paraffin-embedded tissue samples, the emergence of high-plex in situ protein detection methods like the GeoMx Digital Spatial profiler (DSP) has drastically enhanced the resolution of the tumor microenvironment that can be assessed.5 Using the GeoMx DSP, we are quantifying a panel of 40 immune proteins, to expand our understanding of the immune microenvironment of the pre-treatment cohort previously studied. The protein panel enables the detection of multiple immune cell types and subtypes, certain immune pathways like T cell activation and exhaustion, and the expression of immunotherapeutic targets. Preliminary results show that patients with high CD163 expression, associated with immunosuppressive macrophages had poorer outcomes (p= 0.035). The immune microenvironment for larger tumors expressed higher T cell activation markers (p=0.016). While the overall heterogeneity in immune cells did not have an impact on patient outcomes, a high heterogeneity in T cell activation markers was significantly associated with patient outcomes (p=0.029) as well as tumor size (p=0.024). We have characterized the stromal immune cell infiltrates and their spatial heterogeneity, finding immune markers that may significantly impact patient outcomes. Our findings aid in the identification of therapeutic targets prevalent in the TNBC stroma as well as potentially informing therapy decisions based on the tumor immune microenvironment composition. 1. Won KA, Spruck C. (2020). Int J Oncol, 57(6), 1245-1261. DOI:10.3892/ijo.2020.5135 2. Marra A et al. (2020). NPJ Breast Cancer, 6, 54. DOI:10.1038/s41523-020-00197-2 3. Obidiro O et al. (2023). Pharmaceutics, 15(7), 1796. DOI:10.3390/pharmaceutics15071796 4. Kanwar N et al. (2021). Cancer Res, 81(24), 6196-6206. DOI:10.1158/0008-5472.CAN-21-1079 5. Bergholtz H et al. (2021). Cancers, 13(17), 4456. DOI:10.3390/cancers13174456 Citation Format: Prerana Sensharma, Huidan Zuo, Melanie Dawe, Megan Hopkins, Zeynep Baskurt, Osvaldo Espin-Garcia, Philippe L. Bedard, Melanie Spears, Susan J. Done. A spatial profiling approach to evaluating the prognostic impact of heterogeneity in the triple-negative breast cancer immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2010.