High-dimensional analyses reveal a distinct role of T-cell subsets in the immune microenvironment of gastric cancer

Objectives: To facilitate disease prognosis and improve precise immunotherapy of gastric cancer (GC) patients, a comprehensive study integrating immune cellular and molecular analyses on tumor tissues and peripheral blood was performed. Methods: The association of GC patients’ outcomes and the immune context of their tumors was explored using multiplex immunohistochemistry (mIHC) and transcriptome profiling. Potential immune dysfunction mechanism/s in the tumors on the systemic level was further examined using mass cytometry (CyTOF) in complementary peripheral blood from selected patients. GC cohorts with mIHC and gene expression profiling data were also used as validation cohorts. Results: Increased CD4⁺FOXP3⁺ T-cell density in the GC tumor correlated with prolonged survival. Interestingly, CD4⁺FOXP3⁺ T cells had a close interaction with CD8⁺ T cells rather than tumor cells. High densities of CD4⁺FOXP3⁺ T cells and CD8⁺ T cells (High-High) independently predicted prolonged patient survival. Furthermore, the interferon-gamma (IFN-γ) gene signature and PDL1 expression were up-regulated in this group. Importantly, a subgroup of genomically stable (GS) tumors and tumors with chromosomal instability (CIN) within this High-High group also had excellent survival. The High-High GS/CIN tumors were coupled with increased frequencies of Tbet⁺CD4⁺ T cells and central memory CD4⁺ T cells in the peripheral blood. Conclusion: These novel findings identify the combination of CD8⁺ T cells and FOXP3⁺CD4⁺ T cells as a significant prognostic marker for GC patients, which also could potentially be targeted and applied in the combination therapy with immune checkpoint blockades in precision medicine.