Dynamics of tertiary lymphoid structures and immune cross talk in early versus advanced colorectal cancer: potential implications for immunotherapy.

BACKGROUND: Irrespective of microsatellite status, immune checkpoint inhibitor therapy shows superior efficacy in early-stage colorectal cancer (CRC) compared to advanced cases. The distinctions of the tumor microenvironment (TME) and tertiary lymphoid structure (TLS) between early- and advanced-stage CRC may represent a critical factor, yet remain incompletely elucidated. METHODS: We comprehensively analyzed single-cell RNA sequencing data, bulk RNA transcription data and pathological tissue data to investigate the dynamic changes in the TME. The features of TLS in early- and advanced-stage tumors and their potential impact on immunotherapy were explored using three in-house cohorts. RESULTS: We provided single-cell fine maps of the immune landscape in early and advanced CRC. Significant functional differences were identified in CD4 + Tfh and BGC cells between early and advanced CRC. We revealed CXCL13 expression on CD8 + Tex cells, along with CD40-CD40L interactions between CD4 + Tfh and BGC cells, could be key regulators of TLS functionality and subsequently affect the response to immunotherapy. CONCLUSIONS: Our research shed light on the multilayered immune dysfunction in advanced CRC and elucidates the alterations in the TLS during the progression of CRC, providing insights for functional studies and the exploration of potential target in advanced CRC.