Fang‐Zhu Ouyang

UNLABELLED: 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-1(hi) B cells exhibited a unique CD5(hi)CD24(-/+)CD27(hi/+)CD38(dim) phenotype different from the phenotype of conventional CD24(hi)CD38(hi) peripheral regulatory B cells. TLR4-mediated BCL6 upregulation was crucial for PD-1(hi) 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-1(hi) 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-1(hi) 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-1(hi) 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); 546-59. ©2016 AACR.See related commentary by Ren et al., p. 477This article is highlighted in the In This Issue feature, p. 461.

Abstract B cells are prominent components of human solid tumours, but activation status and functions of these cells in human cancers remain elusive. Here we establish that over 50% B cells in hepatocellular carcinoma (HCC) exhibit an FcγRII low/− activated phenotype, and high infiltration of these cells positively correlates with cancer progression. Environmental semimature dendritic cells, but not macrophages, can operate in a CD95L-dependent pathway to generate FcγRII low/− activated B cells. Early activation of monocytes in cancer environments is critical for the generation of semimature dendritic cells and subsequent FcγRII low/− activated B cells. More importantly, the activated FcγRII low/− B cells from HCC tumours, but not the resting FcγRII high B cells, without external stimulation suppress autologous tumour-specific cytotoxic T-cell immunity via IL-10 signals. Collectively, generation of FcγRII low/− activated B cells may represent a mechanism by which the immune activation is linked to immune tolerance in the tumour milieu.

UNLABELLED: B cells consistently represent abundant cellular components in tumors; however, direct evidence supporting a role for B cells in the immunopathogenesis of human cancers is lacking, as is specific knowledge of their trafficking mechanisms. Here, we demonstrate that chemokine (C-X-C motif) receptor 3-positive (CXCR3(+)) B cells constitute approximately 45% of B-cell infiltrate in human hepatocellular carcinoma (HCC) and that their levels are positively correlated with early recurrence of HCC. These cells selectively accumulate at the invading edge of HCC and undergo further somatic hypermutation and immunoglobulin G-secreting plasma cell differentiation. Proinflammatory interleukin-17(+) cells are important for the induction of epithelial cell-derived CXCR3 ligands CXCL9, CXCL10, and CXCL11, which subsequently promote the sequential recruitment and further maturation of CXCR3(+) B cells. More importantly, we provide evidence that CXCR3(+) B cells, but not their CXCR3(-) counterparts, may operate in immunoglobulin G-dependent pathways to induce M2b macrophage polarization in human HCC. Depletion of B cells significantly suppresses M2b polarization and the protumorigenic activity of tumor-associated macrophages and restores the production of antitumorigenic interleukin-12 by those cells in vivo. CONCLUSION: Selective recruitment of CXCR3(+) B cells bridges proinflammatory interleukin-17 response and protumorigenic macrophage polarization in the tumor milieu, and blocking CXCR3(+) B-cell migration or function may help defeat HCC.

Classical IL-22-producing T helper cells (Th22 cells) mediate inflammatory responses independently of IFN-γ and IL-17; however, nonclassical Th22 cells have been recently identified and coexpress IFN-γ and/or IL-17 along with IL-22. Little is known about how classical and nonclassical Th22 subsets in human diseases are regulated. Here, we used samples of human blood, normal and peritumoral liver, and hepatocellular carcinoma (HCC) to delineate the phenotype, distribution, generation, and functional relevance of various Th22 subsets. Three nonclassical Th22 subsets constituted the majority of all Th22 cells in human liver and HCC tissues, although the classical Th22 subset was predominant in blood. Monocytes activated by TLR2 and TLR4 agonists served as the antigen-presenting cells (APCs) that most efficiently triggered the expansion of nonclassical Th22 subsets from memory T cells and classical Th22 subsets from naive T cells. Moreover, B7-H1-expressing monocytes skewed Th22 polarization away from IFN-γ and toward IL-17 through interaction with programmed death 1 (PD-1), an effect that can create favorable conditions for in vivo aggressive cancer growth and angiogenesis. Our results provide insight into the selective modulation of Th22 subsets and suggest that strategies to influence functional activities of inflammatory cells may benefit anticancer therapy.