Investigate the heterogeneity of colorectal cancer patients at the single-cell level prior to and subsequent to immunotherapy

BackgroundImmune checkpoint blockade (ICB) has improved outcomes for a subset of colorectal cancer (CRC) patients, yet the cellular determinants that drive heterogeneous treatment responses remain insufficiently understood. The extent to which ICB reshapes immune populations across tumor, blood, and adjacent normal tissues at single-cell resolution is largely unexplored.MethodsWe reanalyzed spatiotemporal single-cell RNA-sequencing data from CRC patients treated with Pembrolizumab or Sintilimab, profiling immune and stromal compartments across pre- and post-treatment tumor, blood, and normal mucosa.

Major cell types and transcriptional programs were characterized using Seurat and Harmony. Treatment-associated cellular remodeling, differential gene expression, and response-related signatures were assessed in T cells and B cells.

Cell-cell communication networks were inferred using CellChat.ResultsICB produced pronounced remodeling of tumor-infiltrating lymphocytes, particularly within T cell and B cell lineages. Responders (CR/PR) exhibited robust cytotoxic T-cell activation characterized by up-regulation of GNLY, GZMB, and CXCL13, whereas non-responders (SD) uniquely showed persistent overexpression of HSPA1B, a stress-response gene associated with tumor progression and immune suppression.

Responders (CR/PR) exhibited robust cytotoxic T-cell activation, with increased expression of GNLY, GZMB, and CXCL13.