The role of AdipoR1 and AdipoR2 in liver fibrosis

Activation of the adiponectin (APN) signaling axis retards liver fibrosis. However, understanding of the role of AdipoR1 and AdipoR2 in mediating this response is still rudimentary. Here, we sought to elucidate the APN receptor responsible for limiting liver fibrosis by employing AdipoR1 and AdipoR2 knock-out mice in the carbon tetrachloride (CCl4) model of liver fibrosis. In addition, we knocked down receptor function in primary hepatic stellate cells (HSCs) in vitro. Following the development of fibrosis, AdipoR1 and AdipoR2 KO mice had no quantitative difference in fibrosis by Sirius red staining. However, AdipoR2 KO mice had an enhanced fibrotic signature with increased Col1-α1, TGFß-1, TIMP-1, IL-10, MMP-2 and MMP-9. Knockdown of AdipoR1 or AdipoR2 in HSCs followed by APN treatment demonstrated that AdipoR1 and AdipoR2 did not affect proliferation or TIMP-1 gene expression, while AdipoR2 modulated Col1-α1 and α-SMA gene expression, HSC migration, and AMPK activity. These finding suggest that AdipoR2 is the major APN receptor on HSCs responsible for mediating its anti-fibrotic effects

Hepatitis C Virus Induces the Cannabinoid Receptor 1

BACKGROUND: Activation of hepatic CB(1) receptors (CB(1)) is associated with steatosis and fibrosis in experimental forms of liver disease. However, CB(1) expression has not been assessed in patients with chronic hepatitis C (CHC), a disease associated with insulin resistance, steatosis and metabolic disturbance. We aimed to determine the importance and explore the associations of CB(1) expression in CHC. METHODS: CB(1) receptor mRNA was measured by real time quantitative PCR on extracted liver tissue from 88 patients with CHC (genotypes 1 and 3), 12 controls and 10 patients with chronic hepatitis B (CHB). The Huh7/JFH1 Hepatitis C virus (HCV) cell culture model was used to validate results. PRINCIPAL FINDINGS: CB(1) was expressed in all patients with CHC and levels were 6-fold higher than in controls (P<0.001). CB(1) expression increased with fibrosis stage, with cirrhotics having up to a 2 fold up-regulation compared to those with low fibrosis stage (p<0.05). Even in mild CHC with no steatosis (F0-1), CB(1) levels remained substantially greater than in controls (p<0.001) and in those with mild CHB (F0-1; p<0.001). Huh7 cells infected with JFH-1 HCV showed an 8-fold upregulation of CB(1), and CB(1) expression directly correlated with the percentage of cells infected over time, suggesting that CB(1) is an HCV inducible gene. While HCV structural proteins appear essential for CB(1) induction, there was no core genotype specific difference in CB(1) expression. CB(1) significantly increased with steatosis grade, primarily driven by patients with genotype 3 CHC. In genotype 3 patients, CB(1) correlated with SREBP-1c and its downstream target FASN (SREBP-1c; R=0.37, FASN; R=0.39, p<0.05 for both). CONCLUSIONS/SIGNIFICANCE: CB(1) is up-regulated in CHC and is associated with increased steatosis in genotype 3. It is induced by the hepatitis C virus

Role of angiogenesis in HCC development and therapy

A pre-requisite for tumour growth and metastasis is angiogenesis, the sprouting and growth of new capillaries from pre-existing blood vessels. Tumours without the ability to induce the growth of new capillaries remain small, in the order of 1-2 mm3. Drugs are now available, such as Bevacizumab, to inhibit angiogenesis and human tumour growth. Hepatocellular carcinoma (HCC) is a very aggressive human cancer, has clear angiogenic characteristics and patients with HCC have a very poor clinical outlook. In this context, we review the mechanisms of the predominant angiogenic pathways and how their targeting can impact on liver tumour growth. We also discuss the role of hepatitis in influencing liver tumour blood vessel growth. Equally, the role of the hepatic manifestation of the metabolic syndrome, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) is considered, since it is now one of most common causes of liver disease in Western Societies. There are links between angiogenesis and metabolism and although poorly researched in respect of HCC, these we examine as they may impact on liver tumour formation and progression. Finally, we report on the current status of trials of anti-angiogenic HCC therapy and consider the potential limitations of such a therapeutic strategy

Molecular cross-talk between the liver and white adipose tissue links excessive noURIshment to hepatocellular carcinoma

In their recent study published in Cancer Cell, Gomes and colleagues uncovered a novel mechanism driving obesity-triggered hepatocellular carcinoma (HCC). The authors revealed a feed-forward loop between hepatic unconventional prefoldin RPB5 interactor (URI) and cytokine interleukin-17A (IL-17A), and showed that chronically high expression of both proteins induces DNA damage, followed by systemic inflammation, which initiates non-alcoholic steatohepatitis (NASH) and HCC. URI and IL-17A are involved in cross-talk between the liver and white adipose tissue (WAT), with lipolysis, neutrophil infiltration and insulin resistance occurring in WAT, resulting in hepatosteatosis, injury and HCC in the liver. These results suggest that targeting URI and IL-17 levels may be a useful therapeutic strategy in the treatment of obesity-driven HCC

Non-viral causes of liver cancer: does obesity led inflammation play a role

Liver cancer is the fifth most common cancer worldwide and the third most common cause of cancer mortality. Hepatocellular carcinoma (HCC) accounts for around 90% of primary liver cancers. Chronic infection with hepatitis B and hepatitis C viruses are two of most common causes of liver cancer. However, there are non-viral factors that are associated with liver cancer development. Numerous population studies have revealed strong links between obesity and the development of liver cancer. Obesity can alter hepatic pathology, metabolism and promote inflammation, leading to nonalcoholic fatty liver disease (NAFLD) and the progression to the more severe form, non-alcoholic steatohepatitis (NASH). NASH is characterised by prominent steatosis and inflammation, and can lead to HCC. Here, we discuss the role of obesity in inflammation and the principal signalling mechanisms involved in HCC formation

Animal models of hepatocellular carcinoma

Hepatocellular carcinoma is the fifth most common cancer worldwide. Studies of the molecular mechanisms leading to hepatocarcinogenesis hold the key to improvements in diagnosis and treatment of this disease. Animal models give us the opportunity to study these mechanisms by manipulating the risk factors and associated genetic alterations that lead to hepatocarcinogenesis. Worldwide, hepatitis B virus (HBV) and hepatitis C virus (HCV) infections account for more than two thirds of HCC cases. Therefore, HBV- and HCV-induced hepatocarcinogenesis in animals would most closely mimic the aetiology and possibly the associated pathogenesis of human HCC. Other risk factors include exposure to chemical carcinogens and other causes of cirrhosis. Rodents remain the most valuable animal models and can be classified as infection-associated, carcinogen-induced, and transgenic or inflammatory. From studies of these models, many potential molecular mechanisms have been identified as contributing to hepatocarcinogenesis, such as HBx, c-Myc, TGFa, IGF-II, H-ras, p53, NF-KB, and Wnt signaling pathways. Transgenic mouse models with the potential for wider use include the P-catenin/H-ras double transgenic mouse, the TGFa/c-Myc double transgenic mouse and the c-Met conditional knockout mouse (MetLivKO). These mice develop liver tumours with high penetrance and a short latency and pathological features similar to human HCC. Other species including rabbits, woodchucks, tree shrews, dogs, pigs and primates have been used to study diagnostic and therapeutic options in HCC. However, more work is required to unravel the sequence of events that leads to HCC in order to guide future prevention, diagnosis and treatment

Adiponectin deficiency limits tumor vascularization in the MMTV-PyV-mT mouse model of mammary cancer

PURPOSE\ud \ud High levels of the fat-secreted cytokine adiponectin (APN) are present in the circulation of healthy people, whereas low levels correlate with an increased incidence of breast cancer in women. The current study experimentally probes the physiologic functions of APN in mammary cancer in a newly generated genetic mouse model.\ud \ud EXPERIMENTAL DESIGN\ud \ud We established an APN null mouse model of mammary cancer by introducing the polyoma virus middle T (PyV-mT) oncogene expressed from mouse mammary tumor virus (MMTV) regulatory elements into APN null mice. MMTV-PyV-mT-induced tumors resemble ErbB2-amplified human breast cancers. We monitored tumor onset, kinetics, and animal survival, and analyzed vascular coverage, apoptosis, and hypoxia in sections from the primary tumors. Metastatic spreading was evaluated by analyses of the lungs.\ud \ud RESULTS\ud \ud APN prominently localized to the vasculature in human and mouse mammary tumors. In APN null mice, MMTV-PyV-mT-induced tumors appeared with delayed onset and exhibited reduced growth rates. Affected animals survived control tumor-bearing mice by an average of 21 days. Pathologic analyses revealed reduced vascularization of APN null tumors along with increased hypoxia and apoptosis. At the experimental end point, APN null transgenic mice showed increased frequency of pulmonary metastases.\ud \ud CONCLUSION\ud \ud The current work identifies a proangiogenic contribution of APN in mammary cancer that, in turn, affects tumor progression. APN interactions with vascular receptors may be useful targets for developing therapies aimed at controlling tumor vascularization in cancer patients

T-cadherin supports angiogenesis and adiponectin association with the vasculature in a mouse mammary tumor model

T-cadherin delineates endothelial, myoepithelial, and ductal epithelial cells in the normal mouse mammary gland, and becomes progressively restricted to the vasculature during mammary tumorigenesis. To test the function of T-cadherin in breast cancer, we inactivated the T-cadherin (Cdh13) gene in mice and evaluated tumor development and pathology after crossing the mutation into the mouse mammary tumor virus (MMTV)-polyoma virus middle T (PyV-mT) transgenic model. We report that T-cadherin deficiency limits mammary tumor vascularization and reduces tumor growth. Tumor transplantation experiments confirm the stromal role of T-cadherin in tumorigenesis. In comparison with wild-type MMTV-PyV-mT controls, T-cadherin-deficient tumors are pathologically advanced and metastasize to the lungs. T-cadherin is a suggested binding partner for high molecular weight forms of the circulating, fat-secreted hormone adiponectin. We discern adiponectin in association with the T-cadherin-positive vasculature in the normal and malignant mammary glands and report that this interaction is lost in the T-cadherin null condition. This work establishes a role for T-cadherin in promoting tumor angiogenesis and raises the possibility that vascular T-cadherin-adiponectin association may contribute to the molecular cross-talk between tumor cells and the stromal compartment in breast cancer

Maternal embryonic leucine zipper kinase is upregulated and required in mammary tumor-initiating cells in vivo

Maternal embryonic leucine zipper kinase (MELK) is expressed in several developing tissues, in the adult germ line, and in adult neural progenitors. MELK expression is elevated in aggressive undifferentiated tumors, correlating with poor patient outcome in human breast cancer. To investigate the role of MELK in mammary tumorigenesis in vivo, we used a MELK-green fluorescent protein (GFP) reporter mouse, which allows prospective isolation of MELK-expressing cells based on GFP fluorescence. We found that in the normal mammary gland, cells expressing high levels of MELK were enriched in proliferating cells that express markers of mammary progenitors. The isolation of cells with high levels of MELK in mammary tumors from MMTV-Wnt1/MELK-GFP bitransgenic mice resulted in a significant enrichment of tumorsphere formation in culture and tumor initiation after transplantation into mammary fat pads of syngeneic mice. Furthermore, using lentiviral delivery of MELK-specific shRNA and limiting dilution cell transplantations, we showed that MELK function is required for mammary tumorigenesis in vivo. Our findings identify MELK as a potential target in breast tumor-initiating cells