B cells often constitute abundant cellular components in human tumors. Regulatory B cells that are functionally defined by their ability to produce IL10 downregulate inflammation and control T-cell immunity. Here, we identified a protumorigenic subset of B cells that constitutively expressed higher levels of programmed cell death-1 (PD-1) and constituted ∼10% of all B cells in advanced-stage hepatocellular carcinoma (HCC). These PD-1hi B cells exhibited a unique CD5hiCD24−/+CD27hi/+CD38dim phenotype different from the phenotype of conventional CD24hiCD38hi peripheral regulatory B cells. TLR4-mediated BCL6 upregulation was crucial for PD-1hi B-cell induction by HCC environmental factors, and that effect was abolished by IL4-elicited STAT6 phosphorylation. Importantly, upon encountering PD-L1+ cells or undergoing PD-1 triggering, PD-1hi B cells acquired regulatory functions that suppressed tumor-specific T-cell immunity and promoted cancer growth via IL10 signals. Our findings provide significant new insights for human cancer immunosuppression and anticancer therapies regarding PD-1/PD-L1.
SIGNIFICANCE: We identify a novel protumorigenic PD-1hi B-cell subset in human HCC that exhibits a phenotype distinct from that of peripheral regulatory B cells. TLR4-mediated BCL6 upregulation is critical for induction of PD-1hi B cells, which operate via IL10-dependent pathways upon interacting with PD-L1 to cause T-cell dysfunction and foster disease progression. Cancer Discov; 6(5); 1–14. ©2016 AACR.
See related commentary by Ren et al., p. 477.
Note: Supplementary data for this article are available at Cancer Discovery Online (http://cancerdiscovery.aacrjournals.org/).
- Received November 30, 2015.
- Revision received February 23, 2016.
- Accepted February 23, 2016.
- ©2016 American Association for Cancer Research.