Deep-Red and Ultrafast Photocatalytic Proximity Labeling Empowered in situ Dissection of Tumor-Immune Interactions in Primary Tissues

Immunotherapy efficacy in solid tumors varies greatly, influenced by the tumor microenvironment (TME) and the dynamic tumor-immune interactions within it. Decoding these interactions in situ with minimal interference to native tissue architecture and delicate immune responses is critical for understanding tumor progression and optimizing therapeutic strategies. Here, we introduce CAT-Tissue, a novel deep-red photocatalytic proximity labeling method that enables ultrafast, high-resolution profiling of tumor-immune interactions in primary tissues. By leveraging nanobody-Chlorin e6 as the photocatalyst and biotin-aniline as the probe, CAT-Tissue enabled the rapid and comprehensive detection of various tumor-immune interactions in both coculture systems and primary tumor sections. Coupled with bulk RNA-sequencing, CAT-Tissue revealed distinct gene expression patterns between tumor-neighboring and tumor-distal lymphocytes, highlighting the recognition and immune responses of tumor-neighboring CD8+ T cells, which exhibited activated, effector, and exhausted phenotypes. By leveraging a deep-red photocatalytic proximity cell labeling strategy with excellent tissue penetration and biocompatibility, CAT-Tissue offers a non-genetically encoded platform with high sensitivity and spatiotemporal controllability for rapid profiling tumor-immune interactions within complex tissue environments in situ, which may advance our understanding of tumor immunology and guide the development of more effective immunotherapies. Overall design: RNA-seq of tumor-neighboring (Biotin+) CD8+ T and tumor-distal (Biotin-) CD8+ T cells of TILs isolated from MC38-hPD-L1 tumor (12 days) on C57BL/6N mice, in triplicate.