Remodeling of T and endothelial cells during total neoadjuvant therapy in rectal cancer

Total neoadjuvant therapy (TNT) is a standard care for locally advanced rectal cancer (LARC), yet the immune remodeling mechanisms underlying its efficacy remain unclear. Using single-cell RNA, T cell receptor, and spatial transcriptome sequencing of matched pre- and post-treatment samples, we depicted the tumor microenvironment (TME) dynamics induced by different neoadjuvant therapies. TNT is associated with reduced regulatory T cells and increased IFNG⁺CD8⁺ effector memory T cells with high IFNG expression, potentially contributing to improved complete response rates. The abundance of tumor-infiltrating CD8⁺ T cells is correlated with the enrichment of the ACKR1⁺ endothelial subset after TNT. We further validated that endothelial cells (ECs), when stimulated by IFNγ, potentially released by CD8⁺ T cells, acquire an enhanced ability for presenting antigens and activating CD8⁺ T cells. Together, our study systematically characterizes the TME dynamics and uncovers the unique interaction between activated CD8⁺ T cells and ECs after TNT.