Abstract 6151: Tumor microenvironment heterogeneity identifies potential biomarkers of response in ER-positive breast cancers treated with palbociclib

Abstract

Abstract Despite the breast cancer microenvironment being recognized as a critical participant in tumor progression and therapeutic response, current technologies for tumor cell-to-cell interaction analyses are limited to qualitative and descriptive histological methods. Here, we utilized multiplex immunofluorescence (MxIF), RNA sequencing (RNA-seq), and microarray gene expression to quantitatively assess, using the BostonGene automated pipeline, the immune microenvironment composition of clinical stage 2 or 3 primary estrogen receptor-positive (ER+) HER2-negative (HER-) breast tumors (n = 29) from patients treated with neoadjuvant palbociclib in combination with anastrozole. Microenvironment characteristics of pretreatment tumor biopsies were associated with molecular subtype, cytokine signatures, and Ki67 response. MxIF analysis (21 markers, 2-13 ROIs per slide) of the tumor immune composition revealed that while the cellular composition was similar for each tumor region of the same patient, significant cellular heterogeneity was observed in tumor biopsies from different patients. The spatial heterogeneity was found in the distribution of both immune infiltrate cells and stromal components. T cells, CD68+ and CD163+ macrophages, and B cells were the predominant cell populations in the stromal component. Further MxIF analysis showed an increase in Ki67+ tumor cells in nonresponders (NR) versus responders (R). The number of immune cells was similar between Luminal A and B breast cancer molecular subtypes. A lower number of Ki67+ tumor cells was found in Luminal A compared to Luminal B tumors, as expected. MxIF analysis of cell-to-cell interactions revealed that distinct groups of cellular neighborhoods were significantly increased in NR compared with R: the immune inflammation cluster with a high density of CD4 T cells, Tregs, and CD8 T cells in the stromal component (p = 0.03); CD163+ macrophage-enriched cluster (p < 0.001); and tertiary lymphoid structures cluster (p < 0.001). Transcriptomic analysis showed that while CXCL1, CCL17, CCL13, CXCL9, and CCL5 expression correlated with the high density of CD4 and CD8 T cells in the stromal component cluster, VEGFA, IL1B, CXCL16, CCL3, and CCL7 were increased in the CD163+ and CD68+ macrophage-enriched clusters, indicating that differential cytokine expression is associated with the tumor architecture.Comprehensively characterizing, via MxIF, the immune microenvironment of ER+ HER2- breast cancer provided resolution of cellular architecture and elucidated spatial relationships among the immune and stromal cells of the tumor. Quantitatively assessing breast tumor cell-to-cell interactions has the potential to identify imaging markers of response, ultimately leading to the development of effective therapy options. Citation Format: Maria Bruttan, Souzan Sanati, Anna Belozerova, Ilia Galkin, Akshaya Ramachandran, Pavel Ovcharov, Grigory Perelman, Viktor Svekolkin, Ekaterina Postovalova, Alexander Bagaev, Krystle Nomie, Shana Thomas, Jeremy Hoog, Ravshan Ataullakhanov, James Hsieh, Cynthia Ma. Tumor microenvironment heterogeneity identifies potential biomarkers of response in ER-positive breast cancers treated with palbociclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6151.