Abstract 7106: Comprehensive spatial profiling of the tumor immune microenvironment in triple negative breast cancer from Black women

Abstract Normal tissues from Black individuals, regardless of their country of birth or residence, remain critically understudied. This gap in research is particularly concerning, as Black individuals disproportionately experience aggressive pathological diseases, often exhibit resistance or refractoriness to treatment, and face higher rates of premature death. In women, breast cancer is not only more common among U.S. Black women, but it also tends to develop at a younger age compared to other ancestral groups. Furthermore, U.S. Black women are approximately twice as likely as White women to be diagnosed with triple-negative breast cancer (TNBC), a subtype characterized by higher recurrence rates and poorer survival outcomes. To investigate the biological factors contributing to these disparities, we spatially profiled TNBC tumors from U.S. Black and White patients. Our analysis revealed significant differences in the tumor immune microenvironment (TiME). Tumors from Black women exhibited higher immune infiltration, particularly among macrophage and T cell populations. To explore how differences in key immune cell populations could impact immunotherapeutic outcomes, we employed a multiomic spatial proteomics approach, aimed at (1) identifying immune cell populations, (2) mapping their activation states, and (3) revealing PD-1/PD-L1 checkpoint activity. All of this was accomplished with a novel serial CellScapeTM workflow, which allows the integration multiplex immunofluorescence (mIF) with and in situ Proximity Ligation Assay (isPLA). Our mIF assay consisted of more than 30 VistaplexTM antibodies and efficiently labeled immune cell lineages, activation states and checkpoints. Cell-to-cell interactions and protein-protein interactions at immune checkpoints were then surveyed throughout the TiME using isPLA, which enables the imaging-based identification of checkpoint activation via detection of protein-protein interactions. The assay is based on a 40 nm proximity of the interacting partners and uses rolling circle amplification (RCA) to amplify the signal, ensuring high sensitivity and specificity of the detected interaction, in this case, that of PD1 and PDL1. Collectively these results affirmed heightened immune infiltration in tumors from Black woman and, crucially, allowed us to map checkpoint activation on a cell-by-cell phenotypic basis. By leveraging multiomic spatial phenotyping, we detected distinctions in the TNBC TiME from Black women compared to White women. Linking together the occurrence of certain cell phenotypes, their spatial signatures, and their checkpoint activation states. These findings underscore the importance of studying diverse patient populations to better understand tumor biology and inform more equitable therapeutic strategies. Citation Format: Felipe Segato Dezem, Matt Ingalls, Omotoso Ayodele, Destiny Burnett, Priscila Coelho, Carmen Gomez, Sara Bodbin, Judith Hurley, Agata Zieba Wicher, Arne Christians, Jannik Boog, Daniel Jimenez Sanchez, Oliver Braubach, Sophia George, Jasmine Plummer. Comprehensive spatial profiling of the tumor immune microenvironment in triple negative breast cancer from Black women [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 7106.