Immune landscape of liver metastases in advanced lung cancer.

Abstract

8540 Background: The liver is a frequent site of metastasis and carries a poor prognosis in patients with non-small cell (NSCLC) and small cell lung cancer (SCLC). Patients with liver metastases (LM) derive limited benefit from immune checkpoint inhibitors (ICI), due to hepatic myeloid derived suppressor cell (MDSC) mediated T cell elimination. Here, we used imaging mass cytometry (IMC) to perform single cell, highly multiplexed, analysis of LM and primary lung tumors to investigate how vascular endothelial growth factor (VEGF) influences T cell depletion within the tumor immune microenvironment (TIME) of LM. Methods: We comprehensively characterizedthe TIME in LM and primary lung tumors in 21 patients with NSCLC or SCLC using IMC. A panel of 40 antibodies was assembled to interrogate immune subsets and VEGF pathway markers. Each antibody was conjugated to a unique metal isotope. After validation, the antibody cocktail was used to stain the biopsies. Tissue images were segmented using Mesmer, and hierarchical clustering was applied to single-cell expression data to identify phenotypes. Similar clustering of cell neighbor profiles was applied to obtain spatial motifs. Phenotypic and motif frequencies, together with functional expression across phenotypes, were compiled from all samples and compared across conditions. Results: Initial visualization of the raw, unsegmented data revealed higher infiltration of CD8 + and CD4 + T cells in LM compared to the lung TIME. After segmentation, marker expression heatmaps uncovered complex cell-cell interaction ecosystems. The liver samples were enriched with M2 macrophages (CD163 + ), MDSC (CD11b + ), and proliferative endothelial cells (CD105 + ) whereas the lung samples were enriched in tumor cells (TTF1 + for NSCLC and INSM1 + /synaptophysin + for SCLC) and T cells (CD4 + , CD8 + ). Spatial neighborhood profiling of NSCLC liver tissues identified 12 neighborhood types, showing a general trend of mutual exclusivity between MDSCs and CD4 + /CD8 + T cells across neighborhoods. Notably, CD8 + T cells in MDSC-enriched neighborhoods exhibited consistently higher FAS expression, a key apoptotic marker. Heterogenous FAS and VEGF signaling across neighborhoods suggested a mixed immune-suppressive and vascularized response in the liver TIME, supporting VEGF’s role in mediating MDSC-driven hepatic CD8 + T cell depletion in patients with LM. Conclusions: Our findings highlight significant differences in the TIME between LM and primary lung tumors, with LM demonstrating a more immunosuppressive and VEGF-enriched milieu. The spatial association of MDSCs with CD8 + T cells, along with elevated FAS expression and VEGF signaling suggests a mechanistic role for VEGF in driving immune evasion within liver tumors. These results underscore the potential of VEGF blockade as a therapeutic strategy to overcome T cell suppression and improve ICI efficacy in patients with lung cancer metastatic to liver (NCT05588388, PI Sankar).