Enhanced expression of the cancer stem cell (CSC) marker, CD133, is closely associated with a higher rate of tumor formation and poor prognosis in hepatocellular carcinoma (HCC) patients. Despite its clinical significance, the molecular mechanism underlying the deregulation of CD133 during tumor progression remains to be clarified. Here, we report on a novel mechanism by which interleukin‐6/signal transducer and activator of transcription 3 (IL‐6/STAT3) signaling up‐regulates expression of CD133 and promotes HCC progression. STAT3 activated by IL‐6 rapidly bound to CD133 promoter and increased protein levels of CD133 in HCC cells. Reversely, in hypoxic conditions, RNA interference silencing of STAT3 resulted in decrease of CD133 levels, even in the presence of IL‐6, with a concomitant decrease of hypoxia‐inducible factor 1 alpha (HIF‐1α) expression. Active STAT3 interacted with nuclear factor kappa B (NF‐κB) p65 subunit to positively regulate the transcription of HIF‐1α providing a mechanistic explanation on how those three oncogenes work together to increase the activity of CD133 in a hypoxic liver microenvironment. Activation of STAT3 and its consequent induction of HIF‐1α and CD133 expression were not observed in Toll‐like receptor 4/IL‐6 double‐knockout mice. Long‐term silencing of CD133 by a lentiviral‐based approach inhibited cancer cell‐cycle progression and suppressed in vivo tumorigenicity by down‐regulating expression of cytokinesis‐related genes, such as TACC1, ACF7, and CKAP5. We also found that sorafenib and STAT3 inhibitor nifuroxazide inhibit HCC xenograft formation by blocking activation of STAT3 and expression of CD133 and HIF‐1α proteins. Conclusion: IL‐6/STAT3 signaling induces expression of CD133 through functional cooperation with NF‐κB and HIF‐1α during liver carcinogenesis. Targeting STAT3‐mediated CD133 up‐regulation may represent a novel, effective treatment by eradicating the liver tumor microenvironment. (Hepatology 2015;62:1160‐1173)

Reactive oxygen species (ROS) contribute to the development of non-alcoholic fatty liver disease. ROS generation by infiltrating macrophages involves multiple mechanisms, including Toll-like receptor 4 (TLR4)-mediated NADPH oxidase (NOX) activation. Here, we show that palmitate-stimulated CD11b+F4/80low hepatic infiltrating macrophages, but not CD11b+F4/80high Kupffer cells, generate ROS via dynamin-mediated endocytosis of TLR4 and NOX2, independently from MyD88 and TRIF. We demonstrate that differently from LPS-mediated dimerization of the TLR4–MD2 complex, palmitate binds a monomeric TLR4–MD2 complex that triggers endocytosis, ROS generation and increases pro-interleukin-1β expression in macrophages. Palmitate-induced ROS generation in human CD68lowCD14high macrophages is strongly suppressed by inhibition of dynamin. Furthermore, Nox2-deficient mice are protected against high-fat diet-induced hepatic steatosis and insulin resistance. Therefore, endocytosis of TLR4 and NOX2 into macrophages might be a novel therapeutic target for non-alcoholic fatty liver disease.

The important roles of retinols and their metabolites have recently been emphasized in the interactions between hepatic stellate cells (HSCs) and natural killer (NK) cells. Nevertheless, the expression and role of retinol metabolizing enzyme in both cell types have yet to be clarified. Thus, we investigated the expression of retinol metabolizing enzyme and its role in liver fibrosis. Among several retinol metabolizing enzymes, only alcohol dehydrogenase (ADH) 3 expression was detected in isolated HSCs and NK cells, whereas hepatocytes express all of them. In vitro treatment with 4-methylpyrazole (4-MP), abroad ADH inhibitor, or depletion of the ADH3 gene downregulated collagen and transforming growth factor-β1 (TGF-β1) gene expression, but did not affect α-smooth muscle actin gene expression in cultured HSCs. Additionally, in vitro, treatments with retinol suppressed NK cell activities, whereas inhibition of ADH3 enhanced interferon-γ (IFN-γ) production and cytotoxicity of NK cells against HSCs. In vivo, genetic depletion of the ADH3 gene ameliorated bile duct ligation- and carbon tetrachloride-induced liver fibrosis, in which a higher number of apoptotic HSCs and an enhanced activation of NK cells were detected. Freshly isolated HSCs from ADH3-deficient mice showed reduced expression of collagen and TGF-β1, but enhanced expression of IFN-γ was detected in NK cells from these mice compared with those of control mice. Using reciprocal bone marrow transplantation of wild-type and ADH3-deficient mice, we demonstrated that ADH3 deficiency in both HSCs and NK cells contributed to the suppressed liver fibrosis. Conclusion ADH3 plays important roles in promoting liver fibrosis by enhancing HSC activation and inhibiting NK cell activity, and could be used as a potential therapeutic target for the treatment of liver fibrosis.

Eosinophils are a myeloid cell subpopulation that mediates type 2 T helper cell immune responses. Unexpectedly, we identified a rapid accumulation of eosinophils in 22 human liver grafts after hepatic transplantation. In contrast, no eosinophils were detectable in healthy liver tissues before transplantation. Studies with two genetic mouse models of eosinophil deficiency and a mouse model of antibody-mediated eosinophil depletion revealed exacerbated liver injury after hepatic ischemia and reperfusion. Adoptive transfer of bone marrow–derived eosinophils normalized liver injury of eosinophil-deficient mice and reduced hepatic ischemia and reperfusion injury in wild-type mice. Mechanistic studies combining genetic and adoptive transfer approaches identified a critical role of suppression of tumorigenicity (ST2)–dependent production of interleukin-13 by eosinophils in the hepatoprotection against ischemia-reperfusion–induced injury. Together, these data provide insight into a mechanism of eosinophil-mediated liver protection that could serve as a therapeutic target to improve outcomes of patients undergoing liver transplantation.

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