Abstract Colorectal cancer (CRC) is one of the most common malignant tumors with the highest incidence and mortality rates worldwide. Immune checkpoint blockade (ICB) therapy has revolutionized the landscape of cancer treatment; however, most patients with CRC gain limited benefits from it. The immunosuppressive microenvironment of CRC is an important cause of tumor progression, metastasis, and immunotherapy resistance. This study aimed to reveal the key role of chemokine receptor 4 (CXCR4) in the immunosuppressive microenvironment and glutamine metabolism reprogramming using integrated single-cell transcriptomics and metabolomics analyses. The in vivo and in vitro experiments verified that CXCR4 mediated metabolic reprogramming in CRC cells by regulating the PI3K-Akt-SMAD4 pathway. Further co-culture experiments revealed that CXCR4 promoted the polarization of tumor-associated macrophages (TAMs) to M2 type through glutamine metabolic reprogramming and induced the exhaustion of CD8 + T cells, thereby intensifying immune escape. The knockdown of CXCR4 significantly increased the infiltration of CD8 + T cells and M1 TAMs, reduced the infiltration of M2 TAMs, effectively reshaped the immunosuppressive microenvironment of CRC-bearing mice, and significantly enhanced the immunotherapeutic effect against programmed cell death protein 1 (PD-1). This study discovered a novel mechanism by which CXCR4 drove CRC immune escape through the dual-axis regulation of the “glutamine metabolism-immune microenvironment.” Targeting CXCR4 not only inhibits tumor metabolic adaptability but also reverses TAMs polarization and T cell exhaustion, thereby effectively sensitizing PD-1 inhibitors. This study provides an important theoretical basis and a highly promising new combined treatment strategy for overcoming ICB resistance in patients with CRC.
Zhu et al. (Mon,) studied this question.