Lagal, Daniel J.

Abstract Specialized immune niches located in the stroma-tumor junction promote interactions between tumor-resident antigen-presenting cells and effector lymphocytes that are required for immunotherapy efficacy. We have hypothesized that this stromal-based immune crosstalk may be regulated by provisional extracellular matrix signals, analogous to the early-stages of wound healing where provisional matrix hosts robust immune activity. A cardinal provisional matrix remodeling event, the regulated proteolysis of the large proteoglycan versican (VCAN) generates an immunomodulatory fragment (matrikine), versikine, that engages adaptive immunity. We have previously shown that VCAN proteolysis correlates with T-cell infiltration across multiple solid and liquid cancers with the most immune-evasive cancers showing low to negligible rates of VCAN proteolysis (e.g., 0% in pancreatic adenocarcinoma). A recent clinical trial generated informative prospective data linking VCAN proteolysis with immunotherapy outcomes: patients whose metastatic colorectal tumors categorized as VCAN proteolysis-weak (VPW, 60% of cases) demonstrated inferior responses to checkpoint inhibition (CPI, pembrolizumab) and worse outcomes compared to VCAN proteolysis-predominant (VPP, 40%) cases. Leveraging these prospective trial data, we hypothesized that versikine therapy may rationally reverse the immunosuppression associated with the prevalent VPW phenotype. To tailor versikine therapy to specific human biomarker-stratified tumor phenotypes, we studied experimental models replicating partially T-permissive VPW-VCANlo human cancers and poor-prognosis, immune-exclusionary VPW-VCANhi cancers. Across VPW-like tumors, versikine promoted the stromal accumulation of CD40lghiIcoshiFoxp3neg Tfh-like CD4+ T cells that engaged dendritic cells (DC) and CD8+ T cells in “immune triads” even at baseline (prior to CPI), concurrently with the intratumoral expansion of activated CD8+ T cells expressing cytolytic molecules (granzymes, perforin). In VPW-VCANlo tumors, versikine delivered as LNP-mRNA or recombinant protein demonstrated monotherapy activity, dependent on Batf3-lineage DC and CD8+ T cells. When combined with single-agent CPI, versikine cured most VPW-VCANlo tumors with memory to tumor re-challenge. In VPW-VCANhi tumors, versikine synergized with combination immunotherapy modulating “mature DCs enriched in immunoregulatory molecules” (mregDC). Our data provide mechanistic rationale for the biomarker-stratified, therapeutic restoration of a provisional matrix-regulated immune signaling network to reverse resistance to CPI. Moreover, the data highlight the need to reevaluate prior approaches to globally disrupt tumor stroma in favor of biomarker-driven, pathway-focused harnessing of stromal signals that modulate anti-tumor immunity. Citation Format: Daniel J. Lagal, Duncan Hong, Athanasios Papadas, Emma Geatches, George Yacu, Surabhi Naik, Alicia Gibbons, Alexander Cicala, Kersi Pestonjamasp, Peter Toth, Kristina Matkowskyj, Dustin A. Deming, Fotis Asimakopoulos. Biomarker-driven restoration of tumor provisional matrix signaling network reverses resistance to checkpoint inhibition immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6746.

Abstract Recent evidence has highlighted the critical requirement for “immune triads” of CD8+ T cells, CD4+ T cells and dendritic cells (DC) for tumor elimination in response to checkpoint inhibition (CPI) immunotherapy. However, the mechanistic underpinnings of this cross-talk are poorly understood. Immune triads are often located in peripherally-distributed DC-rich niches within the tumor stroma. We have hypothesized that stromal remodeling in response to tumor expansion generates homeostatic signals that trigger an adaptive immune response that may ultimately fail through effector exhaustion or apoptosis. In particular, stromal proteolysis of the large matrix proteoglycan versican (VCAN) has been associated with T-cell infiltration across multiple tumor types. The objective of this study was to interrogate a mechanistic link between stromal remodeling, immune triad formation and response to CPI. We used HALO image analysis to determine the spatial relationship of CD4+ and CD8+ T cells in a panel of 95 human non-small cell lung cancers. Each tumor was VCAN proteolysis-scored based on a binning system measuring staining intensity for a neoepitope exposed through site-specific VCAN proteolysis. Tumors displaying VCAN proteolysis intensity of zero (0) had an average of 0.122 CD8+ T cells located with 10um of a CD4+ T cell vs. 0.216 in tumors with any VCAN proteolysis (intensity 1, 2, 3 combined); p=0.04. Similar results were obtained when measuring proximity of CD4+ to CD8+ T cells (0.124 vs 0.223, p=0.02). These data demonstrate that remodeling stroma promotes CD4+:CD8+ crosstalk. Site-specific VCAN proteolysis releases a 441 N-terminal bioactive fragment, versikine. Versikine constitutes a classical “matrikine”, i.e., a bioactive matrix fragment possessing novel functions compared to its parent macromolecule. To determine the mechanisms by which versikine may promote immune triad niches, we generated several transplantable syngeneic tumor cell lines engineered to stably secrete versikine into the TME. One CPI-refractory tumor cell line (Lewis Lung Carcinoma, LLC) and two partially CPI-responsive transplantable tumor lines (CT26 and MC38 colorectal carcinoma) were extensively characterized through flow cytometry, spatial immunofluorescence and scRNAseq. Our results demonstrate that in all contexts, versikine results in expansion of Tfh-like CD4+ T cells expressing Cd40lg and Icos. This expansion is associated with specific patterns of CD8+ T cell exhaustion that will be discussed. Therapeutically, versikine reversed anti-PD-1 pathway refractoriness in the poorly-immunogenic LLC model and demonstrated superior synergy with CPI in the more immunogenic CT26 and MC38 models, leading to tumor eradication with resistance to tumor rechallenge. Our data bolster the mechanistic rationale for exploitation of stromal remodeling signals to promote CD4+T:CD8+T:DC cross-talk for enhanced CPI efficacy. Citation Format: Daniel Lagal, Duncan Hong, Athanasios Papadas, Alicia Gibbons, Yun Huang, Yaling Dou, Alexander Cicala, Elsa Molina, Kristina Matkowskyj, Dustin Deming, Fotis Asimakopoulos. Stromal remodeling promotes immune triad formation in the tumor microenvironment (TME) [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 2588.