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. 26 patients with LARC, treated with three different neoadjuvant therapies including nCT, nRT and nRCT, were enrolled in this study. We employed droplet-based single-cell RNA sequencing (scRNA-seq) and paired T-cell receptor sequencing (scTCR-seq) to profile a set of 92 samples, including 44 blood tissues and 48 tumor tissues. These samples were collected from patients before (pre-treatment, Pre) and after neoadjuvant therapies. ---------------------- Authors state: The corresponding raw data has been deposited in the Genome Sequence Archive in National Genomics Data Center, China National Center for Bioinformation / Beijing Institute of Genomics, Chinese Academy of Sciences (GSA-Human: HRA006512) that are publicly accessible at https://ngdc.cncb.ac.cn/gsa-human. When published, raw FASTQ data are publicly available and a data access agreement will be required to evaluate the reasonableness of the data request and to avoid any confidentiality obligations