Year: 2026
Type: conference-abstract
Abstract: Background Spatially organized immune niches of T cells and antigen-presenting cells (APCs) have been associated with immune checkpoint therapy (ICT) efficacy. However, our understanding of how these structures form and evolve over time remains limited. In fact, most of our current insights derive from spatial analyses conducted at single time points or during suboptimal therapeutic responses without complete tumor clearance. Consequently, the spatiotemporal mechanisms governing the role of these T cell-APC niches during successful immunotherapy remain largely undefined.Methods We used a spatial-proteomic approach to investigate longitudinal changes in immune organization in a fully responsive ICT mouse tumor model (T3). Mice bearing syngeneic orthotopic T3 tumors were treated with control monoclonal antibodies or the ICT combination of α-CTLA-4 and α-PD-1. A total of 42 tumors were harvested at multiple time points and subjected to CODEX multiplex imaging, allowing us to profile 13,051,156 cells and 13 distinct cell types with single-cell resolution in fresh-frozen sections. In parallel, we generated scRNA-seq data and integrated transcriptomic and spatial proteomic datasets using ARCADIA, a framework for spatially informed analysis of transcriptional programs, and validated key findings using Xenium.Results T3 tumors were organized into seven cellular neighborhoods (CNs), but successful ICT led to the assembly, expansion, and maturation of an immunity-promoting cellular neighborhood (IP-CN) enriched in CD4 + and CD8+ T cells forming three-cell clusters (triads) with two distinct types of APCs: cDC1s or IFNγ-activated macrophages. Triads first increased in frequency at the onset of tumor rejection, and their emergence was accompanied by extensive remodeling of chemokine and cytokine communication networks, including enrichment of IFNγ- and TNFα-associated signaling pathways. This functional remodeling enabled the IP-CN to serve as a major intratumoral site for induction of T-cell proliferation and effector differentiation. Over time, the IP-CN expanded throughout tumor rejection, ultimately becoming the largest CN within the tumor tissue. During this expansion, we found that the IP-CN underwent functional maturation and formed two subneighbothoods that spatially compartmentalized proliferating Ki67+ T cells (localized alongside triad-forming APCs at the tumor periphery), from cytotoxic granzyme-B+ T cells that accumulated near tumor targets and progressively advanced from the tumor boundary toward the tumor core.Conclusions Our findings provide critical and novel temporal insight into the role of T cell–APC niches during successful ICT and reveal a mechanism in which immune triad interactions nucleate the formation of the IP-CN that organizes and sustains tumor immunity during successful ICT.Ethics Approval All studies were performed in accordance with procedures by AAALAC accredited Animal Studies Committee of Washington University in St. Louis.
Authors: Ruan Felipe Vieira Medrano, Vladimir Sukhov, Kevin Hoffer-Hawlik, Bar Rozenman, Cora D Arthur, Fei Han, Bassem Ben Cheikh, Hussein Sultan, Yoshiko Takeuchi, Samuel Ameh, Derek J Theisen, Yuang Song, Heather N Kohlmiller, J Michael White, Alexey Sergushichev, Bernd H Zinselmeyer, Pat Leinert, Wm Pat Leinert, Kathleen C F Sheehan, Garry P Nolan, Elham Azizi, Maxim Artyomov, Robert D Schreiber
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,490
OpenAlex ID: W7225303998