Spatial single-cell proteotyping reveals immunotherapy-resistant features within the complex tumor microenvironment...

BACKGROUNDImmune checkpoint inhibitors (ICIs) targeting the programmed cell death 1 axis have revolutionized metastatic non-small cell lung cancer (mNSCLC) treatment. However, disease progression remains a concern, and the role of the complex tumor microenvironment (TME) in treatment failure is not fully understood.METHODSIn this biomarker study involving 103 patients with mNSCLC, including 81 patients who received ICI treatment, we evaluated the association between heterogeneous immune cell subsets and ICI efficacy through single-cell spatial profiling of pretreatment tumor tissue, using a 29-marker multiplex IHC platform built for in-depth dissection of the TME.RESULTSAmong various types of intratumoral lymphocytes, including Th1, Treg, and NK cells, only CD8+ T cells (tumor-infiltrating lymphocytes [TILs]) were associated with ICI efficacy. Computational tissue segmentation underscored the importance of direct physical interactions between CD8+ TILs and cancer cells for ICI efficacy. TIL phenotyping identified CD39/CD103/Ki-67 positivity as a hallmark of exhausted yet functional tumor-reactive CD8+ TILs. Immunosuppressive tumor-associated macrophages (TAMs) and cancer-associated fibroblasts were independent unfavorable adversaries. High CD73 expression on cancer cells was suggested to confer tolerance to ICI in EGFR/ALK-oncogene+ NSCLC, potentially through M2-TAM accumulation and aberrant angiogenesis.CONCLUSIONOur study delineates the clinical relevance of heterogeneous immune cell subsets in ICI-treated mNSCLC, aiding the development of targeted therapeutic strategies.FUNDINGOsaka Cancer Society, KANAE Foundation for the Promotion of Medical Science, SGH Foundation, and YOKOYAMA Foundation for Clinical Pharmacology.