Macrophages (Mφ) are prominent components of solid tumors and exhibit distinct phenotypes in different microenvironments. We have recently found that tumors can alter the normal developmental process of Mφ to trigger transient activation of monocytes in peritumoral stroma. We showed that a fraction of monocytes/Mφ in peritumoral stroma, but not in cancer nests, expresses surface PD-L1 (also termed B7-H1) molecules in tumors from patients with hepatocellular carcinoma (HCC). Monocytes activated by tumors strongly express PD-L1 proteins with kinetics similar to their activation status, and significant correlations were found between the levels of PD-L1+ and HLA-DRhigh on tumor-infiltrating monocytes. Autocrine tumor necrosis factor α and interleukin 10 released from activated monocytes stimulated monocyte expression of PD-L1. The PD-L1+ monocytes effectively suppressed tumor-specific T cell immunity and contributed to the growth of human tumors in vivo; the effect could be reversed by blocking PD-L1 on those monocytes. Moreover, we found that PD-L1 expression on tumor-infiltrating monocytes increased with disease progression, and the intensity of the protein was associated with high mortality and reduced survival in the HCC patients. Thus, expression of PD-L1 on activated monocytes/Mφ may represent a novel mechanism that links the proinflammatory response to immune tolerance in the tumor milieu.

No abstract

B cells often constitute abundant cellular components in human tumors. Regulatory B cells that are functionally defi ned by their ability to produce IL10 downregulate infl ammation and control T-cell immunity. Here, we identifi ed 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).

H epatocellular carcinoma (HCC) is characterized by progressive development, high postsurgical recurrence, and extremely poor prognosis. The dismal outcome has been attributed to the highly vascular nature of HCC, which increases the propensity to spread and invade into neighboring or distant sites. 1 Tumor progression is now recognized as the product of evolving crosstalk between different cell types within tumors. 2,3 HCC is usually present in inflamed fibrotic and/or cirrhotic liver with extensive leukocyte infiltration. Thus, the immune status at a tumor site can largely influence the biologic behavior of HCC. 1,4 Recent studies have shown that high infiltration of intratumoral regulatory T cells is associated with reduced survival and increased invasiveness in HCC. 5 These findings are in accordance with the general view that the tumor microenvironment

Macrophages play a pivotal role in tissue fibrogenesis, which underlies the pathogenesis of many end-stage chronic inflammatory diseases. MicroRNAs are key regulators of immune cell functions, but their roles in macrophage's fibrogenesis have not been characterized. Here we show that IL-4 and IL-13 induce miR-142-5p and downregulate miR-130a-3p in macrophages; these changes sustain the profibrogenic effect of macrophages. In vitro, miR-142-5p mimic prolongs STAT6 phosphorylation by targeting its negative regulator, SOCS1. Blocking miR-130a relieves its inhibition of PPARγ, which coordinates STAT6 signalling. In vivo, inhibiting miR-142-5p and increasing miR-130a-3p expression with locked nucleic acid-modified oligonucleotides inhibits CCL4-induced liver fibrosis and bleomycin-induced lung fibrosis in mice. Furthermore, macrophages from the tissue samples of patients with liver cirrhosis and idiopathic pulmonary fibrosis display increased miR-142-5p and decreased miR-130a-3p expression. Therefore, miR-142-5p and miR-130a-3p regulate macrophage profibrogenic gene expression in chronic inflammation.