Integrated Multiomics and Functional Validation Identify CLSPN as a Central Integrator of Genomic Instability and Immune Remodeling in Colorectal Cancer

Colorectal cancer (CRC) is characterized by pervasive genomic instability, yet the molecular mechanisms linking replication stress responses to genome alteration and phenotypic evolution remain incompletely understood. Here, we performed an integrative multiomics analysis combined with functional validation to investigate the role of CLSPN, a key adaptor of the ATR‐CHK1 pathway, in CRC. Machine learning–based feature selection identified CLSPN as a robust prognostic factor. Single‐cell and spatial transcriptomic analyses revealed that CLSPN is preferentially enriched in highly proliferative tumor cell populations and spatially localized within tumor core regions. Elevated CLSPN expression was strongly associated with increased copy number variation burden (FGA, FGG, and FGL) and chromosomal instability, indicating enhanced tolerance to replication stress and accumulation of genomic alterations. This genomic instability was further linked to remodeling of the tumor immune microenvironment. Functional assays demonstrated that CLSPN promotes proliferation, invasion, and migration while suppressing apoptosis in CRC cells. Collectively, these findings identify CLSPN as a key regulator of replication stress–driven genomic instability and highlight its role in shaping mutation‐associated tumor evolution, providing a potential target for therapeutic intervention.