Th121 - Mapping T Cell Antitumor Responses in Whole Blood to Solid Tumor Tissue Biopsies of Cancer Patients Using Mass Cytometry

Abstract Text: Immunotherapy has revolutionized cancer treatment, yet it exhibits limited efficacy in solid tumors due to their complex immune landscape involving an immunosuppressive tumor microenvironment (TME). To develop safe and effective immunotherapies, it is crucial to achieve a comprehensive understanding of localized and systemic immune responses.

Here, we took an integrative approach of mapping localized and systemic T cell responses with CyTOF™ and Imaging Mass Cytometry™ (IMC™) technologies in matched PBMC, tumor-derived cells and FFPE tumor tissues from cancer patients. Samples were barcoded, stained with a 40-plus-marker CyTOF panel (including lineage markers, immune checkpoint markers, cytokines and transcription factors), frozen and acquired later using a CyTOF XT system. FFPE tumor tissues were stained with a 40-plus-marker immuno-oncology IMC panel to phenotype immune, stromal and tumor cells, and assess the activation status of immune cells. Samples were acquired using the Hyperion™ XTi Imaging System to capture both whole-tissue sections and subcellular-resolution regions of interest.

CyTOF analysis revealed phenotypic and functional heterogeneity, including distinct T cell exhaustion and activation profiles. IMC analysis illuminated the spatial relationships of immune subsets relative to tumor cells, vasculature and stromal components, uncovering distinct patterns of immune infiltration and congregation. Merging CyTOF and IMC data revealed shared and divergent phenotypes between peripheral and tissue-resident immune compartments, highlighting the power of an integrated mass cytometry approach to identify potential biomarkers linking systemic immune profiles and the spatial heterogeneity of the TME.