Colorectal cancer liver metastasis: immunosuppressive microenvironment, signaling pathways, and emerging therapeutic strategies.

Colorectal cancer liver metastasis (CRLM) remains a leading cause of mortality in colorectal cancer. The metastatic liver site is characterized by an immunosuppressive microenvironment enriched with inhibitory immune cells and cytokines, contributing to a poorly inflamed, "cold" tumor phenotype. The progression of CRLM is driven by aberrant activation of oncogenic signaling pathways and a dysfunctional immune landscape, marked by T cell exhaustion and the expansion of immunosuppressive cell populations. This review summarizes the epidemiological characteristics of CRLM and discusses the mechanisms underlying its immunosuppressive microenvironment. We further highlight recent advances in therapeutic strategies, including radiotherapy, interventional approaches, and immune checkpoint inhibitors, providing insights for future mechanistic research and therapeutic development.