Abstract 2045: Spatial organization of the immune microenvironment after neoadjuvant treatment of breast cancer
Authors: Thomas Noémie , Garaud Soizic , Langouo Mireille , Zerdes Ioannis , Sofronii Doïna , Boisson Anaïs , Foukakis Theodoros , De Wind Alexandre , Salgado Roberto , Awada Ahmad , Willard-Gallo Karen 
Published: June 2022

Abstract
Using the immune system to fight cancer has garnered tangible success, but some treatments, like neoadjuvant chemotherapy (NAC), modulate the immune microenvironment. Recent studies show that the spatial organization of tumor infiltrating lymphocytes (TIL) have greater predictive value than TIL density. The effect of NAC on immune composition and spatial distribution is not fully understood but new insight could help to guide its use in combination with immune therapy and identify patients with potential to derive benefit. We spatially profiled 84 RNA targets (GeoMx®) in a cohort of 12 NAC-treated breast cancer patients (4 Luminal, 4 HER2+ and 4 triple negative), none of whom achieved a pathological complete response. Matched pre- and post-treatment tissue samples were analyzed together with regions of interest (tumor center, invasive margin and TIL aggregates) identified using CD3, CD20, Syto83 and pan-cytokeratin for stromal/tumor segmentation. NAC decreases overall gene expression in breast tumors with the biggest declines seen in tumor promoting (CCND1, AKT1, CTNNB1, EPCAM, VEGFA, KRT and MKI67) and some inflammatory (CXCL10, STAT1 and STAT2) genes (p-value &lt;0.05; other immune related transcripts showed little variation). Expression was compared between patients with a good response (&lt;20% tumor cellularity) and those with a poor response (&gt;50% cellularity). Poor responders expressed higher levels of tumor promoting genes pre-NAC, which remained high after treatment (KRT p=0.023, CTNNB1 p=0.031). No differences were detected in immune genes in the stroma based on patient responsiveness; however, higher antigen presentation and inflammatory gene transcripts were found at the tumor margins of good responders. Post-NAC differences between the margin and center decrease in good responders paralleled by a shift towards higher or equal expression of some inflammatory markers at the tumor center. Poor responders maintain high expression of all immune markers at the margin. A higher number of aggregates (mean n=5 vs n=1.3) were detected in good compared to poor responders together with more tertiary lymphoid structures (mean n=2.4 vs n=0.3) and distinguished by higher immune gene expression (CD8 p=0.046, CCL5 p=0.054, NKG7 p=0.022). NAC induces changes in other cells in the tumor microenvironment while targeting tumor cells. Our data show that spatial analysis of gene expression comparing good and poor responders (without a pathological complete response) reveal that tumor cells in the latter retain expression of tumor promoting genes while the immune compartment remains excluded. Good responders are characterized by a decrease in tumor promoting genes in parallel with lymphoid aggregates, including TLS, of active immune cells in the stroma and at the tumor center. These findings suggest that tailoring adjuvant treatment between good and poor responding patients might be warranted.
Citation Format: Noémie Thomas, Soizic Garaud, Mireille Langouo, Ioannis Zerdes, Doïna Sofronii, Anaïs Boisson, Theodoros Foukakis, Alexandre De Wind, Roberto Salgado, Ahmad Awada, Karen Willard-Gallo. Spatial organization of the immune microenvironment after neoadjuvant treatment of breast cancer [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 2045.