Tumor-infiltrated activated B cells suppress liver metastasis of colorectal cancers

More than 40% of patients with late-stage colorectal cancer (CRC) develop liver metastasis (LM). Which immune cells play important roles in CRC-LM and contribute to the difference between left-sided CRC (LCC) and right-sided CRC (RCC) remain unclear. By single-cell RNA sequencing (scRNA-seq), we not only find that activated B cells are significantly depleted in CRC with LM, but also find a subtype of B cells developed from activated B cells, namely immature plasma cell population alpha (iMPA), highly correlated with metastasis. Mechanistically, inhibition of the Wnt and transforming growth factor β (TGF-β) pathways in cancer cell promotes activated B cell migration via the SDF-1-CXCR4 axis. This study reveals that B cell subpopulations in the tumor immune microenvironment (TIME) play a key role in CRC-LM as well as in LCC and RCC. The preventive effects of modulating B cell subpopulations in CRC may provide a rationale for subsequent drug development and CRC-LM management.