Abstract C142: Differential single-cell spatial immune cell profiles and immune cell interactions identified within lymph nodes metastases of black and white women diagnosed with triple negative breast cancers
Authors: Buckley Paul R. , Akay Melek , Carpenter Esme , Graham Rosalind , Kakkassery Helen , Alaguthurai Thanussuyah , Hossain Priya , Gazińska Patrycja , Irshad Sheeba 
Published: September 2024

Abstract
Ethnic disparities in breast cancer (BC) outcomes have been reported, with lower survival rates among black women compared to white. Additionally, the unfavorable triple negative (TNBC) sub-type is more prevalent in black women and within this population, risk of mortality is again higher compared to white women. Biological contributors to this disparity are less clearly understood than socio-economic factors. Recent studies recognize different breast tumour immune microenvironments between black and white BC patients, necessitating further research into ethnicity-related differences in anti-tumor immune responses. Such responses begin in regional lymph nodes (LNs) with tumor neoantigen presentation. Here, we generate single-cell spatial maps of involved TNBC LN cores in treatment naïve black and white women. To guide design of a phenotyping panel for LNs, we profiled blood samples (n=95) using high-dimensional flow cytometry from newly diagnosed black and white BC patients. We found differential skewing of NK cell subsets, lower memory B cell (identified as IgM+CD27+IgD- & IgM+CD27+IgD+ cells) abundance and higher CD4+ T effector memory presence in black patients compared to white. Additionally, higher antigen presentation capacity was observed with increased intermediate monocytes and conventional DCs, confirmed by MS-based proteomics. Using highly multiplexed imaging with a panel of 26 markers, we performed single-cell spatial immune profiling to characterize cellular phenotypes, neighborhoods and interactions within a cohort of LN core biopsies from black patients and white patients. A total of 536,113 cells were segmented for analysis. Cell abundance analysis revealed higher CD8+ T effector memory and CD4+ T cell subsets in white patients, except for CD4+ T effector memory cells which were higher in black patients, consistent with blood profiling. Cellular neighborhood analysis revealed black patient tumor-rich regions were enriched for M2 macrophages while white patients had no such enrichment. In these white patients, a neighborhood resembling canonical follicular structures almost exclusively containing B cells was identified. Interestingly in these black patients, analogous B cell rich regions also comprised a heterogeneous array of other immune cells. Further analysis to explore B cell zones is ongoing. Preliminary interaction analysis identified immunosuppressive crosstalk in black patients with enriched Treg & CD8+ T cell and Treg & NK interactions, not observed in white patients. These initial findings suggest ethnicity-based variation in LN architectures from treatment naive patients with TNBC, supporting the hypothesis that variation in immune programming could translate into differences in pro and anti-tumor immunity, contributing to disparities in outcome amongst black and white patients.
Citation Format: Paul R. Buckley, Melek Akay, Esme Carpenter, Rosalind Graham, Helen Kakkassery, Thanussuyah Alaguthurai, Priya Hossain, Patrycja Gazińska, Sheeba Irshad. Differential single-cell spatial immune cell profiles and immune cell interactions identified within lymph nodes metastases of black and white women diagnosed with triple negative breast cancers [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C142.