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Humanized mouse tumor models for evaluation of ILT2 and ILT4 antagonist antibodies

ABSTRACT: Solid tumors are dense three-dimensional (3D) multi-cellular structures that enable efficient receptor–ligand trans interactions via close cell–cell contact. Immunoglobulin-like transcript (ILT)2 and ILT4 are related immune suppressive receptors that play a role in the inhibition of myeloid cells within the tumor microenvironment. The relative contributions of ILT2 and ILT4 to immune inhibition in the context of solid tumor tissue has not been fully explored. We present evidence that both ILT2 and ILT4 contribute to myeloid inhibition. We found that while ILT2 inhibits myeloid cell activation in the context of trans-engagement by MHC-I, ILT4 efficiently inhibits myeloid cells in the presence of either cis- or trans-engagement. In a 3D spheroid tumor model, dual ILT2/ILT4 blockade was required for optimal activation of myeloid cells, including the secretion of CXCL9 and CCL5, upregulation of CD86 on dendritic cells, and downregulation of CD163 on macrophages. Humanized mouse tumor models showed increased immune activation and cytolytic T cell activity with combined ILT2 and ILT4 blockade, including evidence of the generation of immune niches, which have been shown to correlate with clinical response to immune checkpoint blockade. In a human tumor explant histoculture system, dual ILT2/ILT4 blockade increased CXCL9 secretion, downregulated CD163 expression, and increased the expression of M1 macrophage, IFN-γ, and cytolytic T cell gene signatures. Thus, we have revealed distinct contributions of ILT2 and ILT4 to myeloid cell biology and provide proof-of-concept data supporting the combined blockade of ILT2 and ILT4 to therapeutically induce optimal myeloid cell reprogramming in the tumor microenvironment.

ORGANISM(S): Homo sapiens

PROVIDER: GSE255649 | GEO | 2025/02/12

REPOSITORIES: GEO

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Project description:The differentiation and effector function of tumor infiltrating lymphocytes and macrophages in the tumor microenvironment is critical for productive anti-tumor immune responses, although direct evidence for this remains poorly characterized in brain cancer patients. Using mass cytometry, single-cell RNA sequencing, and quantitative multiplex immunofluorescence, we comprehensively characterized the phenotype and single-cell transcriptome of myeloid cells and T lymphocytes that infiltrated malignant gliomas, and identified how such populations changed following neoadjuvant PD-1 checkpoint blockade in recurrent glioblastoma patients. Cells of the myelo-monocytic lineage represented approximately three quarters of the immune cell infiltrate, with T lymphocytes representing the next major immune cell subset by density and percentage, but following neoadjuvant PD-1 antibody blockade, the ratio of myeloid cells to T cells significantly decreased. We then used single-cell RNA sequencing to comprehensively define the transcriptional profiles of lymphoid and myeloid populations in these tumors. Recurrent GBM patients treated with neoadjuvant PD-1 checkpoint inhibition possessed a greater fraction of CD8+ T cells with an effector T cell transcriptional program. The increased effector T cell populations were associated with the distinct upregulation of the chemokines, CXCL9 and CXCL10 by an interferon-responsive macrophage cluster. Importantly, we also identified that neoadjuvant PD-1 blockade was associated with significantly increased cellular interactions specifically between CD8+ T cells and tumor associated macrophages within the tumor microenvironment. Together, these findings suggest that effector T cell infiltration and differentiation are increased with neoadjuvant PD-1 blockade but impeded by adaptive resistance and immunosuppression from tumor associated macrophages. Future therapeutic strategies to target this dominant immunosuppressive myeloid cell population may be needed to achieve true, therapeutic interventions in this patient population.

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Humanized mouse tumor models for evaluation of ILT2 and ILT4 antagonist antibodies

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