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 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.