Hedgehog signaling antagonist promotes regression of both liver fibrosis and hepatocellular carcinoma in a murine model of primary liver cancer

Role of liver sinusoidal endothelial cell in metabolic dysfunction-associated fatty liver disease

Liver sinusoidal endothelial cells (LSECs) are highly specialized endothelial cells that represent the interface between blood cells on one side and hepatocytes on the other side. LSECs not only form a barrier within the hepatic sinus, but also play important physiological functions such as regulating hepatic vascular pressure, anti-inflammatory and anti-fibrotic. Pathologically, pathogenic factors can induce LSECs capillarization, that is, loss of fenestra and dysfunction, which are conducive to early steatosis, lay the foundation for the progression of metabolic dysfunction-associated fatty liver disease (MAFLD), and accelerate metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. The unique localization, phenotype, and function of LSECs make them potential candidates for reducing liver injury, inflammation, and preventing or reversing fibrosis in the future.

Localized application of SAG21k-loaded fibrin hydrogels for targeted modulation of the hedgehog pathway in facial nerve injury

Given the broad biological effects of the Hedgehog (Hh) pathway, there is potential clinical value in local application of Hh pathway modulators to restrict pathway activation of target tissues and avoid systemic pathway activation. One option to limit Hh pathway activation is using fibrin hydrogels to deliver pathway modulators directly to tissues of interest, bypassing systemic distribution of the drug. In this study, we loaded the potent Hh pathway agonist, SAG21k, into fibrin hydrogels. We describe the binding between fibrin and SAG21k and achieve sustained release of the drug in vitro. SAG21k-loaded fibrin hydrogels exhibit strong biological activity in vitro, using a pathway-specific reporter cell line. To test in vivo activity, we used a mouse model of facial nerve injury. Application of fibrin hydrogels is a common adjunct to surgical nerve repair, and the Hh pathway is known to play an important role in facial nerve injury and regeneration. Local application of the Hh pathway agonist SAG21k using a fibrin hydrogel applied to the site of facial nerve injury successfully activates the Hh pathway in treated nerve tissue. Importantly, this method appears to avoid systemic pathway activation when Hh-responsive organs are analyzed for transcriptional pathway activation. This method of local tissue Hh pathway agonist administration allows for effective pathway targeting surgically accessible tissues and may have translational value in situations where supranormal pathway activation is therapeutic.

Reappraisal of the Roles of the Sonic Hedgehog Signaling Pathway in Hepatocellular Carcinoma

HCC remains one of the leading causes of cancer-related death globally. The main challenges in treatments of hepatocellular carcinoma (HCC) primarily arise from high rates of postoperative recurrence and the limited efficacy in treating advanced-stage patients. Various signaling pathways involved in HCC have been reported. Among them, the Sonic hedgehog (SHH) signaling pathway is crucial. The presence of SHH ligands is identified in approximately 60% of HCC tumor tissues, including tumor nests. PTCH-1 and GLI-1 are detected in more than half of HCC tissues, while GLI-2 is found in over 84% of HCC tissues. The SHH signaling pathway (including canonical and non-canonical) is involved in different aspects of HCC, including hepatocarcinogenesis, tumor growth, tumor invasiveness, progression, and migration. The SHH signaling pathway also contributes to recurrence, metastasis, modulation of the cancer microenvironment, and sustaining cancer stem cells. It also affects the resistance of HCC cells to chemotherapy, target therapy, and radiotherapy. Reappraisal of the roles of the SHH signaling pathway in HCC may trigger some novel therapies for HCC.

TGF-β1/SMAD3-driven GLI2 isoform expression contributes to aggressive phenotypes of hepatocellular carcinoma

Hedgehog signaling is activated in response to liver injury, and modulates organogenesis. However, the role of non-canonical hedgehog activation via TGF-β1/SMAD3 in hepatic carcinogenesis is poorly understood. TGF-β1/SMAD3-mediated non-canonical activation was found in approximately half of GLI2-positive hepatocellular carcinoma (HCC), and two new GLI2 isoforms with transactivating activity were identified. Phospho-SMAD3 interacted with active GLI2 isoforms to transactivate downstream genes in modulation of stemness, epithelial-mesenchymal transition, chemo-resistance and metastasis in poorly-differentiated hepatoma cells. Non-canonical activation of hedgehog signaling was confirmed in a transgenic HBV-associated HCC mouse model. Inhibition of TGF-β/SMAD3 signaling reduced lung metastasis in a mouse in situ hepatic xenograft model. In another cohort of 55 HCC patients, subjects with high GLI2 expression had a shorter disease-free survival than those with low expression. Moreover, co-positivity of GLI2 with SMAD3 was observed in 87.5% of relapsed HCC patients with high GLI2 expression, indicating an increased risk of post-resection recurrence of HCC. The findings underscore that suppressing the non-canonical hedgehog signaling pathway may confer a potential strategy in the treatment of HCC.

Hepatocellular carcinoma: signaling pathways, targeted therapy, and immunotherapy

Hepatocellular carcinoma (HCC) is the most common primary liver cancer with a high mortality rate. It is regarded as a significant public health issue because of its complicated pathophysiology, high metastasis, and recurrence rates. There are no obvious symptoms in the early stage of HCC, which often leads to delays in diagnosis. Traditional treatment methods such as surgical resection, radiotherapy, chemotherapy, and interventional therapies have limited therapeutic effects for HCC patients with recurrence or metastasis. With the development of molecular biology and immunology, molecular signaling pathways and immune checkpoint were identified as the main mechanism of HCC progression. Targeting these molecules has become a new direction for the treatment of HCC. At present, the combination of targeted drugs and immune checkpoint inhibitors is the first choice for advanced HCC patients. In this review, we mainly focus on the cutting-edge research of signaling pathways and corresponding targeted therapy and immunotherapy in HCC. It is of great significance to comprehensively understand the pathogenesis of HCC, search for potential therapeutic targets, and optimize the treatment strategies of HCC.

Emerging trends in gastrointestinal cancers: Targeting developmental pathways in carcinogenesis and tumor progression

Gastrointestinal carcinomas are a group of cancers associated with the digestive system and its accessory organs. The most prevalent cancers related to the gastrointestinal tract are colorectal, gall bladder, gastric, hepatocellular, and esophageal cancers, respectively. Molecular aberrations in different signaling pathways, such as signal transduction systems or developmental pathways are the chief triggering mechanisms in different cancers Though a massive advancement in diagnostic and therapeutic interventions results in improved survival of patients with gastrointestinal cancer; the lower malignancy stages of these carcinomas are comparatively asymptomatic. Various gastrointestinal-related cancers are detected at advanced stages, leading to deplorable prognoses and increased rates of recurrence. Recent molecular studies have elucidated the imperative roles of several signaling pathways, namely Wnt, Hedgehog, and Notch signaling pathways, play in the progression, therapeutic responsiveness, and metastasis of gastrointestinal-related cancers. This book chapter gives an interesting update on recent findings on the involvement of developmental signaling pathways their mechanistic insight in gastrointestinalcancer. Subsequently, evidences supporting the exploration of gastrointestinal cancer related molecular mechanisms have also been discussed for developing novel therapeutic strategies against these debilitating carcinomas.

Phytochemicals as Potential Lead Molecules against Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most prevalent form of liver cancer, accounting for 85-90% of liver cancer cases and is a leading cause of cancer-related mortality worldwide. The major risk factors for HCC include hepatitis C and B viral infections, along with chronic liver diseases, such as cirrhosis, fibrosis, and non-alcoholic steatohepatitis associated with metabolic syndrome. Despite the advancements in modern medicine, there is a continuous rise in the annual global incidence rate of HCC, and it is estimated to reach >1 million cases by 2025. Emerging research in phytomedicine and chemotherapy has established the anti-cancer potential of phytochemicals, owing to their diverse biological activities. In this review, we report the major phytochemicals that have been explored in combating hepatocellular carcinoma and possess great potential to be used as an alternative or in conjunction with the existing HCC treatment modalities. An overview of the pre-clinical observations, mechanism of action and molecular targets of some of these phytochemicals is also incorporated.

Indian Hedgehog release from TNF-activated renal epithelia drives local and remote organ fibrosis

Progressive fibrosis is a feature of aging and chronic tissue injury in multiple organs, including the kidney and heart. Glioma-associated oncogene 1 expressing (Gli1+) cells are a major source of activated fibroblasts in multiple organs, but the links between injury, inflammation, and Gli1+ cell expansion and tissue fibrosis remain incompletely understood. We demonstrated that leukocyte-derived tumor necrosis factor (TNF) promoted Gli1+ cell proliferation and cardiorenal fibrosis through induction and release of Indian Hedgehog (IHH) from renal epithelial cells. Using single-cell-resolution transcriptomic analysis, we identified an "inflammatory" proximal tubular epithelial (iPT) population contributing to TNF- and nuclear factor κB (NF-κB)-induced IHH production in vivo. TNF-induced Ubiquitin D (Ubd) expression was observed in human proximal tubular cells in vitro and during murine and human renal disease and aging. Studies using pharmacological and conditional genetic ablation of TNF-induced IHH signaling revealed that IHH activated canonical Hedgehog signaling in Gli1+ cells, which led to their activation, proliferation, and fibrosis within the injured and aging kidney and heart. These changes were inhibited in mice by Ihh deletion in Pax8-expressing cells or by pharmacological blockade of TNF, NF-κB, or Gli1 signaling. Increased amounts of circulating IHH were associated with loss of renal function and higher rates of cardiovascular disease in patients with chronic kidney disease. Thus, IHH connects leukocyte activation to Gli1+ cell expansion and represents a potential target for therapies to inhibit inflammation-induced fibrosis.

Resolution of hepatic fibrosis after ZFN-mediated gene editing in the PiZ mouse model of human α1-antitrypsin deficiency

BACKGROUND

α1-antitrypsin deficiency is most commonly caused by a mutation in exon-7 of SERPINA1 (SA1-ATZ), resulting in hepatocellular accumulation of a misfolded variant (ATZ). Human SA1-ATZ-transgenic (PiZ) mice exhibit hepatocellular ATZ accumulation and liver fibrosis. We hypothesized that disrupting the SA1-ATZ transgene in PiZ mice by in vivo genome editing would confer a proliferative advantage to the genome-edited hepatocytes, enabling them to repopulate the liver.

METHODS

To create a targeted DNA break in exon-7 of the SA1-ATZ transgene, we generated 2 recombinant adeno-associated viruses (rAAV) expressing a zinc-finger nuclease pair (rAAV-ZFN), and another rAAV for gene correction by targeted insertion (rAAV-TI). PiZ mice were injected i.v. with rAAV-TI alone or the rAAV-ZFNs at a low (7.5×1010vg/mouse, LD) or a high dose (1.5×1011vg/mouse, HD), with or without rAAV-TI. Two weeks and 6 months after treatment, livers were harvested for molecular, histological, and biochemical analyses.

RESULTS

Two weeks after treatment, deep sequencing of the hepatic SA1-ATZ transgene pool showed 6%±3% or 15%±4% nonhomologous end joining in mice receiving LD or HD rAAV-ZFN, respectively, which increased to 36%±12% and 36%±12%, respectively, 6 months after treatment. Two weeks postinjection of rAAV-TI with LD or HD of rAAV-ZFN, repair by targeted insertion occurred in 0.10%±0.09% and 0.25%±0.14% of SA1-ATZ transgenes, respectively, which increased to 5.2%±5.0% and 33%±13%, respectively, 6 months after treatment. Six months after rAAV-ZFN administration, there was a marked clearance of ATZ globules from hepatocytes, and resolution of liver fibrosis, along with reduction of hepatic TAZ/WWTR1, hedgehog ligands, Gli2, a TIMP, and collagen content.

CONCLUSIONS

ZFN-mediated SA1-ATZ transgene disruption provides a proliferative advantage to ATZ-depleted hepatocytes, enabling them to repopulate the liver and reverse hepatic fibrosis.

A novel mechanistic approach for the anti-fibrotic potential of rupatadine in rat liver via amendment of PAF/NF-ĸB p65/TGF-β1 and hedgehog/HIF-1α/VEGF trajectories

Hepatic fibrosis is one of the major worldwide health concerns which requires tremendous research due to the limited outcomes of the current therapies. The present study was designed to assess, for the first time, the potential therapeutic effect of rupatadine (RUP) in diethylnitrosamine (DEN)-induced liver fibrosis and to explore its possible mechanistic actions. For the induction of hepatic fibrosis, rats were treated with DEN (100 mg/kg, i.p.) once weekly for 6 consecutive weeks, and on the 6th week, RUP (4 mg/kg/day, p.o.) was administered for 4 weeks. Treatment with RUP ameliorated changes in body weights, liver indices, liver function enzymes, and histopathological alterations induced by DEN. Besides, RUP amended oxidative stress, which led to the inhibition of PAF/NF-κB p65-induced inflammation, and, subsequently, prevention of TGF-β1 elevation and HSCs activation as indicated by reduced α-SMA expression and collagen deposition. Moreover, RUP exerted significant anti-fibrotic and anti-angiogenic effects by suppressing Hh and HIF-1α/VEGF signaling pathways. Our results highlight, for the first time, a promising anti-fibrotic potential of RUP in rat liver. The molecular mechanisms underlying this effect involve the attenuation of PAF/NF-κB p65/TGF-β1 and Hh pathways and, subsequently, the pathological angiogenesis (HIF-1α/VEGF).

C-X-C motif chemokine ligand 1 induced by Hedgehog signaling promotes mouse extrahepatic bile duct repair after acute injury

BACKGROUND AND AIMS

In extrahepatic bile duct (EHBD) cholangiopathies, including primary sclerosing cholangitis, a reactive cholangiocyte phenotype is associated with inflammation and epithelial hyperproliferation. The signaling pathways involved in EHBD injury response are poorly understood. In this study, we investigated the role of Hedgehog (HH) signaling and its downstream effectors in controlling biliary proliferation and inflammation after EHBD injury.

APPROACH AND RESULTS

Using mouse bile duct ligation as an acute EHBD injury model, we used inhibitory paradigms to uncover mechanisms promoting the proliferative response. HH signaling was inhibited genetically in Gli1^-/- mice or by treating wild-type mice with LDE225. The role of neutrophils was tested using chemical (SB225002) and biological (lymphocyte antigen 6 complex locus G6D [Ly6G] antibodies) inhibitors of neutrophil recruitment. The cellular response was defined through morphometric quantification of proliferating cells and CD45+ and Ly6G+ immune cell populations. Key signaling component expression was measured and localized to specific EHBD cellular compartments by in situ hybridization, reporter strain analysis, and immunohistochemistry. Epithelial cell proliferation peaked 24 h after EHBD injury, preceded stromal cell proliferation, and was associated with neutrophil influx. Indian HH ligand expression in the biliary epithelium rapidly increased after injury. HH-responding cells and neutrophil chemoattractant C-X-C motif chemokine ligand 1 (CXCL1) expression mapped to EHBD stromal cells. Inhibition of HH signaling blocked CXCL1 induction, diminishing neutrophil recruitment and the biliary proliferative response to injury. Directly targeting neutrophils by inhibition of the CXCL1/C-X-C motif chemokine receptor 2/Ly6G signaling axis also decreased biliary proliferation.

CONCLUSIONS

HH-regulated CXCL1 orchestrates the early inflammatory response and biliary proliferation after EHBD injury through complex cellular crosstalk.

Target Therapy for Hepatocellular Carcinoma: Beyond Receptor Tyrosine Kinase Inhibitors and Immune Checkpoint Inhibitors

Simple Summary

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and its incidence is steadily increasing. The development of HCC is a complex, multi-step process that is accompanied by alterations in multiple signaling cascades. Recent years have seen advancement in understanding molecular signaling pathways that play central roles in hepatocarcinogenesis. Aberrant activation of YAP/TAZ, Hedgehog, or Wnt/β-catenin signaling is frequently found in a subset of HCC patients. Targeting the signaling pathway via small molecule inhibitors could be a promising therapeutic option for the subset of patients. In this review, we will introduce the signaling pathways, discuss their roles in the development of HCC, and propose a therapeutic approach targeting the signaling pathways in the context of HCC.

Abstract

Hepatocellular carcinoma (HCC) is a major health concern worldwide, and its incidence is increasing steadily. To date, receptor tyrosine kinases (RTKs) are the most favored molecular targets for the treatment of HCC, followed by immune checkpoint regulators such as PD-1, PD-L1, and CTLA-4. With less than desirable clinical outcomes from RTK inhibitors as well as immune checkpoint inhibitors (ICI) so far, novel molecular target therapies have been proposed for HCC. In this review, we will introduce diverse molecular signaling pathways that are aberrantly activated in HCC, focusing on YAP/TAZ, Hedgehog, and Wnt/β-catenin signaling pathways, and discuss potential therapeutic strategies targeting the signaling pathways in HCC.

Inhibition of Hedgehog Delays Liver Regeneration through Disrupting the Cell Cycle

Liver regeneration is a complicated biological process orchestrated by various liver resident cells. Hepatic cell proliferation and reconstruction of the hepatic architecture involve multiple signaling pathways. It has been reported that the Hh signal is involved in liver regeneration. However, the signal transduction pathways and cell types involved are ill studied. This study aimed to investigate hedgehog signal response cell types and the specific molecular mechanism involved in the process of liver regeneration. Partial hepatectomy (PH) of 70% was performed on ICR (Institute of Cancer Research) mice to study the process of liver regeneration. We found that the hedgehog signal was activated significantly after PH, including hedgehog ligands, receptors and intracellular signaling molecules. Ligand signals were mainly expressed in bile duct cells and non-parenchymal hepatic cells, while receptors were expressed in hepatocytes and some non-parenchymal cells. Inhibition of the hedgehog signal treated with vismodegib reduced the liver regeneration rate after partial hepatectomy, including inhibition of hepatic cell proliferation by decreasing Cyclin D expression and disturbing the cell cycle through the accumulation of Cyclin B. The current study reveals the important role of the hedgehog signal and its participation in the regulation of hepatic cell proliferation and the cell cycle during liver regeneration. It provides new insight into the recovery of the liver after liver resection.

Nanotechnology in Drug Delivery for Liver Fibrosis

Liver fibrosis is a reversible disease course caused by various liver injury etiologies, and it can lead to severe complications, such as liver cirrhosis, liver failure, and even liver cancer. Traditional pharmacotherapy has several limitations, such as inadequate therapeutic effect and side effects. Nanotechnology in drug delivery for liver fibrosis has exhibited great potential. Nanomedicine improves the internalization and penetration, which facilitates targeted drug delivery, combination therapy, and theranostics. Here, we focus on new targets and new mechanisms in liver fibrosis, as well as recent designs and development work of nanotechnology in delivery systems for liver fibrosis treatment.

Dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes hepatobiliary carcinogenesis in non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD), the hepatic correlate of the metabolic syndrome, is a major risk factor for hepatobiliary cancer (HBC). Although chronic inflammation is thought to be the root cause of all these diseases, the mechanism whereby it promotes HBC in NAFLD remains poorly understood. Herein, we aim to evaluate the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis.

METHODS

We use murine NAFLD models, liver biopsies from patients with NAFLD, human liver cancer registry data, and studies in liver cancer cell lines.

RESULTS

Our results confirm the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis, supporting a model whereby chronic inflammation suppresses hepatocyte expression of ESRP2, an RNA splicing factor that directly targets and activates NF2, a tumor suppressor that is necessary to constrain YAP/TAZ activation. The resultant loss of NF2 function permits sustained YAP/TAZ activity that drives hepatocyte proliferation and de-differentiation.

CONCLUSION

Herein, we report on a novel mechanism by which chronic inflammation leads to sustained activation of YAP/TAZ activity; this imposes a selection pressure that favors liver cells with mutations enabling survival during chronic oncogenic stress.

LAY SUMMARY

Non-alcoholic fatty liver disease (NAFLD) increases the risk of hepatobiliary carcinogenesis. However, the underlying mechanism remains unknown. Our study demonstrates that chronic inflammation suppresses hepatocyte expression of ESRP2, an adult RNA splicing factor that activates NF2. Thus, inactive (fetal) NF2 loses the ability to activate Hippo kinases, leading to the increased activity of downstream YAP/TAZ and promoting hepatobiliary carcinogenesis in chronically injured livers.

Concomitant inhibition of hedgehog signalling and activation of retinoid receptors abolishes bleomycin-induced lung fibrosis

Pulmonary fibrosis is a devastating disease with unknown treatment. All-trans retinoic acid (ATRA) attenuates bleomycin-induced lung fibrosis by different mechanistic pathways. However, the role of retinoid receptors in lung fibrosis is still unclear. Forskolin (FSK), a potent inhibitor for the revolutionary hedgehog (Hh) signalling pathway, has a promising antifibrotic effect on other organs such as the liver. This study investigates the interplay between the retinoid receptors modulation and the Hh signalling pathway in bleomycin (BLM)-induced pulmonary fibrosis. Rats were randomised and administrated a single dose of 7.5 mg/kg of BLM alone and with ATRA, FSK and both of them. The effects of FSK and ATRA on lung functions, oxidative stress markers (malondialdehyde [MDA], glutathione [GSH], superoxide dismutase [SOD] and catalase [CAT]), retinoid markers (retinoic acid receptors [RAR] and rexinoid X receptors [RXR]) and Hh signalling markers (patched homolog 1 [Ptch-1], Smoothened [Smo] and glioblastoma-2 [Gli-2]) were assessed. In single therapies, ATRA and FSK ameliorated BLM-induced lung fibrosis. On the contrary, a combination of both drugs synergistically reversed the effect of BLM-induced lung fibrosis, as indicated by the enhancement of lung functions and the decrease of the α-smooth muscle actin (α-SMA) expression and collagen deposition. Additionally, FSK and ATRA ameliorated oxidative stress and inflammation, reduced transforming growth factor β1 (TGF-β1) levels and reversed the effect of BLM on the mRNA expression of Ptch-1, Smo and Gli-2. FSK inhibited the Hh pathway and also activated protein kinase A (PKA) that is, in part, involved in phosphorylation of RAR/RXR heterodimer (a key step in retinoid receptor activation). The present results suggest that a combination of FSK and ATRA has a promising therapeutic value for lung fibrosis management.

Silencing of CD147 inhibits hepatic stellate cells activation related to suppressing aerobic glycolysis via hedgehog signaling

Hepatic stellate cells (HSCs) activation is a key step that promotes hepatic fibrosis. Emerging evidence suggests that aerobic glycolysis is one of its important metabolic characteristics. Our previous study has reported that CD147, a glycosylated transmembrane protein, contributes significantly to the activation of HSCs. However, whether and how it is involved in the aerobic glycolysis of HSCs activation is unknown. The objective of the present study was to validate the effect of CD147 in HSCs activation and the underlying molecular mechanism. Our results showed that the silencing of CD147 decreased the expression of α-smooth muscle-actin (α-SMA) and collagen I at both mRNA and protein levels. Furthermore, CD147 silencing decreased the glucose uptake, lactate production in HSCs, and repressed the lactate dehydrogenase (LDH) activity, the expression of hexokinase 2 (HK2), glucose transporter 1 (Glut1). The effect of galloflavin, a well-defined glycolysis inhibitor, was similar to CD147 siRNA. Mechanistically, CD147 silencing suppressed glycolysis-associated HSCs activation through inhibiting the hedgehog signaling. Moreover, the hedgehog signaling agonist SAG could rescue the above effect of CD147 silencing. In conclusion, CD147 silencing blockade of aerobic glycolysis via suppression of hedgehog signaling inhibited HSCs activation, suggesting CD147 as a novel therapeutic target for hepatic fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-021-00460-9.

The Space of Disse: The Liver Hub in Health and Disease

Since it was first described by the German anatomist and histologist, Joseph Hugo Vincenz Disse, the structure and functions of the space of Disse, a thin perisinusoidal area between the endothelial cells and hepatocytes filled with blood plasma, have acquired great importance in liver disease. The space of Disse is home for the hepatic stellate cells (HSCs), the major fibrogenic players in the liver. Quiescent HSCs (qHSCs) store vitamin A, and upon activation they lose their retinol reservoir and become activated. Activated HSCs (aHSCs) are responsible for secretion of extracellular matrix (ECM) into the space of Disse. This early event in hepatic injury is accompanied by loss of the pores—known as fenestrations—of the endothelial cells, triggering loss of balance between the blood flow and the hepatocyte, and underlies the link between fibrosis and organ dysfunction. If the imbalance persists, the expansion of the fibrotic scar followed by the vascularized septae leads to cirrhosis and/or end-stage hepatocellular carcinoma (HCC). Thus, researchers have been focused on finding therapeutic targets that reduce fibrosis. The space of Disse provides the perfect microenvironment for the stem cells niche in the liver and the interchange of nutrients between cells. In the present review article, we focused on the space of Disse, its components and its leading role in liver disease development.

Hedgehog Signaling, a Critical Pathway Governing the Development and Progression of Hepatocellular Carcinoma

Hedgehog (Hh) signaling is a classic morphogen in controlling embryonic development and tissue repairing. Aberrant activation of Hh signaling has been well documented in liver cancer, including hepatoblastoma, hepatocellular carcinoma (HCC) and cholangiocarcinoma. The present review aims to update the current understanding on how abnormal Hh signaling molecules modulate initiation, progression, drug resistance and metastasis of HCC. The latest relevant literature was reviewed with our recent findings to provide an overview regarding the molecular interplay and clinical relevance of the Hh signaling in HCC management. Hh signaling molecules are involved in the transformation of pre-carcinogenic lesions to malignant features in chronic liver injury, such as nonalcoholic steatohepatitis. Activation of GLI target genes, such as ABCC1 and TAP1, is responsible for drug resistance in hepatoma cells, with a CD133⁻/EpCAM⁻ surface molecular profile, and GLI1 and truncated GLI1 account for the metastatic feature of the hepatoma cells, with upregulation of matrix metalloproteinases. A novel bioassay for the Sonic Hh ligand in tissue specimens may assist HCC diagnosis with negative α-fetoprotein and predict early microvascular invasion. In-depth exploration of the Hh signaling deepens our understanding of its molecular modulation in HCC initiation, drug sensitivity and metastasis, and guides precise management of HCC on an individual basis.

Comparison of MR-PWI quantitative and semi-quantitative parameters for the evaluation of liver fibrosis

Background

To evaluate different stages of liver fibrosis in cynomolgus monkeys by comparing magnetic resonance-perfusion weighted imaging (MR-PWI) quantitative and semi-quantitative parameters, and confirm the best detection indicators for diagnosis of liver fibrosis.

Methods

A liver fibrosis model of different stages (S0–S4) was established in cynomolgus monkeys. The changes in MR-PWI quantitative and semi-quantitative parameters with the progression of liver fibrosis were investigated.

Results

MR-PWI quantitative parameters gradually decreased with the progression of liver fibrosis. Hepatic arterial perfusion index (HPI) was found to increase with the progression of liver fibrosis and significant differences of HPI between each group were observed. There was a highly positive correlation between HPI and the stages of liver fibrosis. Receiver operating characteristic (ROC) curve analysis showed that HPI had the highest efficacy of the MR-PWI quantitative parameters for the diagnosis of liver fibrosis. The MR-PW semi-quantitative parameters gradually reduced with the progression of liver fibrosis, and the differences were statistically significant between stages S3–S4 and S0–S2. Time to peak (TPP) gradually extended and showed a positive correlation with the stages of liver fibrosis. TTP had the highest efficacy of the semi-quantitative parameters for diagnosis of liver fibrosis.

Conclusions

Both the MR-PWI quantitative and semi-quantitative parameters of the liver fibrosis model in cynomolgus monkeys varied at different stages of liver fibrosis, and HPI and TTP were the best detection indices for quantitative and semi-quantitative evaluation of liver fibrosis, respectively.

Targeting Liver Cancer Stem Cells: An Alternative Therapeutic Approach for Liver Cancer

The first report of cancer stem cell (CSC) from Bruce et al. has demonstrated the relatively rare population of stem-like cells in acute myeloid leukemia (AML). The discovery of leukemic CSCs prompted further identification of CSCs in multiple types of solid tumor. Recently, extensive research has attempted to identity CSCs in multiple types of solid tumors in the brain, colon, head and neck, liver, and lung. Based on these studies, we hypothesize that the initiation and progression of most malignant tumors rely largely on the CSC population. Recent studies indicated that stem cell-related markers or signaling pathways, such as aldehyde dehydrogenase (ALDH), CD133, epithelial cell adhesion molecule (EpCAM), Wnt/β-catenin signaling, and Notch signaling, contribute to the initiation and progression of various liver cancer types. Importantly, CSCs are markedly resistant to conventional therapeutic approaches and current targeted therapeutics. Therefore, it is believed that selectively targeting specific markers and/or signaling pathways of hepatic CSCs is an effective therapeutic strategy for treating chemotherapy-resistant liver cancer. Here, we provide an overview of the current knowledge on the hepatic CSC hypothesis and discuss the specific surface markers and critical signaling pathways involved in the development and maintenance of hepatic CSC subpopulations.

Novel molecular targets in hepatocellular carcinoma

Globally, hepatocellular carcinoma (HCC) is a leading cause of cancer and cancer-related deaths. The therapeutic efficacy of locoregional and systemic treatment in patients with advanced HCC remains low, which results in a poor prognosis. The development of sorafenib for the treatment of HCC has resulted in a new era of molecular targeted therapy for this disease. However, the median overall survival was reported to be barely higher in the sorafenib treatment group than in the control group. Hence, in this review we describe the importance of developing more effective targeted therapies for the management of advanced HCC. Recent investigations of molecular signaling pathways in several cancers have provided some insights into developing molecular therapies that target critical members of these signaling pathways. Proteins involved in the Hedgehog and Notch signaling pathways, Polo-like kinase 1, arginine, histone deacetylases and Glypican-3 can be potential targets in the treatment of HCC. Monotherapy has limited therapeutic efficacy due to the development of inhibitory feedback mechanisms and induction of chemoresistance. Thus, emphasis is now on the development of personalized and combination molecular targeted therapies that can serve as ideal therapeutic strategies for improved management of HCC.

Cancer Stem Cell Functions in Hepatocellular Carcinoma and Comprehensive Therapeutic Strategies

Hepatocellular carcinoma (HCC) is a significant cause of cancer-related mortality owing to resistance to traditional treatments and tumor recurrence after therapy, which leads to poor therapeutic outcomes. Cancer stem cells (CSC) are a small subset of tumor cells with the capability to influence self-renewal, differentiation, and tumorigenesis. A number of surface markers for liver cancer stem cell (LCSC) subpopulations (EpCAM, CD133, CD44, CD13, CD90, OV-6, CD47, and side populations) in HCC have been identified. LCSCs play critical roles in regulating HCC stemness, self-renewal, tumorigenicity, metastasis, recurrence, and therapeutic resistance via genetic mutations, epigenetic disruption, signaling pathway dysregulation, or alterations microenvironment. Accumulating studies have shown that biomarkers for LCSCs contribute to diagnosis and prognosis prediction of HCC, supporting their utility in clinical management and development of therapeutic strategies. Preclinical and clinical analyses of therapeutic approaches for HCC using small molecule inhibitors, oncolytic measles viruses, and anti-surface marker antibodies have demonstrated selective, efficient, and safe targeting of LCSC populations. The current review focuses on recent reports on the influence of LCSCs on HCC stemness, tumorigenesis, and multiple drug resistance (MDR), along with LCSC-targeted therapeutic strategies for HCC.

Liver Bioreactor Design Issues of Fluid Flow and Zonation, Fibrosis, and Mechanics: A Computational Perspective

Tissue engineering, with the goal of repairing or replacing damaged tissue and organs, has continued to make dramatic science-based advances since its origins in the late 1980’s and early 1990’s. Such advances are always multi-disciplinary in nature, from basic biology and chemistry through physics and mathematics to various engineering and computer fields. This review will focus its attention on two topics critical for tissue engineering liver development: (a) fluid flow, zonation, and drug screening, and (b) biomechanics, tissue stiffness, and fibrosis, all within the context of 3D structures. First, a general overview of various bioreactor designs developed to investigate fluid transport and tissue biomechanics is given. This includes a mention of computational fluid dynamic methods used to optimize and validate these designs. Thereafter, the perspective provided by computer simulations of flow, reactive transport, and biomechanics responses at the scale of the liver lobule and liver tissue is outlined, in addition to how bioreactor-measured properties can be utilized in these models. Here, the fundamental issues of tortuosity and upscaling are highlighted, as well as the role of disease and fibrosis in these issues. Some idealized simulations of the effects of fibrosis on lobule drug transport and mechanics responses are provided to further illustrate these concepts. This review concludes with an outline of some practical applications of tissue engineering advances and how efficient computational upscaling techniques, such as dual continuum modeling, might be used to quantify the transition of bioreactor results to the full liver scale.

Inflammation and fibrosis in chronic liver diseases including non-alcoholic fatty liver disease and hepatitis C

At present chronic liver disease (CLD), the third commonest cause of premature death in the United Kingdom is detected late, when interventions are ineffective, resulting in considerable morbidity and mortality. Injury to the liver, the largest solid organ in the body, leads to a cascade of inflammatory events. Chronic inflammation leads to the activation of hepatic stellate cells that undergo trans-differentiation to become myofibroblasts, the main extra-cellular matrix producing cells in the liver; over time increased extra-cellular matrix production results in the formation of liver fibrosis. Although fibrogenesis may be viewed as having evolved as a “wound healing” process that preserves tissue integrity, sustained chronic fibrosis can become pathogenic culminating in CLD, cirrhosis and its associated complications. As the reference standard for detecting liver fibrosis, liver biopsy, is invasive and has an associated morbidity, the diagnostic assessment of CLD by non-invasive testing is attractive. Accordingly, in this review the mechanisms by which liver inflammation and fibrosis develop in chronic liver diseases are explored to identify appropriate and meaningful diagnostic targets for clinical practice. Due to differing disease prevalence and treatment efficacy, disease specific diagnostic targets are required to optimally manage individual CLDs such as non-alcoholic fatty liver disease and chronic hepatitis C infection. To facilitate this, a review of the pathogenesis of both conditions is also conducted. Finally, the evidence for hepatic fibrosis regression and the mechanisms by which this occurs are discussed, including the current use of antifibrotic therapy.

The Therapeutic Potential of the Labdane Diterpenoid Forskolin

Forskolin is mainly found in the root of a plant called Coleus forskohlii (Willd.) Briq., which has been used in the traditional medicine of Indian Ayurvedic and Southeast Asia since ancient times. Forskolin is responsible for the pharmacological activity of this species. Forskolin is a labdane diterpenoid with a wide biological effect. Several studies suggested a positive role of forskolin on heart complications, respiratory disorders, high blood pressure, obesity, and asthma. There are numerous clinical and pre-clinical studies representing the effect of forskolin on the above-mentioned disorders but more clinical studies need to be performed to support its efficacy.

Targeting metabolic dysregulation for fibrosis therapy

Fibrosis is the abnormal deposition of extracellular matrix, which can lead to organ dysfunction, morbidity, and death. The disease burden caused by fibrosis is substantial, and there are currently no therapies that can prevent or reverse fibrosis. Metabolic alterations are increasingly recognized as an important pathogenic process that underlies fibrosis across many organ types. As a result, metabolically targeted therapies could become important strategies for fibrosis reduction. Indeed, some of the pathways targeted by antifibrotic drugs in development - such as the activation of transforming growth factor-β and the deposition of extracellular matrix - have metabolic implications. This Review summarizes the evidence to date and describes novel opportunities for the discovery and development of drugs for metabolic reprogramming, their associated challenges, and their utility in reducing fibrosis. Fibrotic therapies are potentially relevant to numerous common diseases such as cirrhosis, non-alcoholic steatohepatitis, chronic renal disease, heart failure, diabetes, idiopathic pulmonary fibrosis, and scleroderma.

Targeting the RAS axis alleviates silicotic fibrosis and Ang II-induced myofibroblast differentiation via inhibition of the hedgehog signaling pathway

The hedgehog (HH) signaling pathway plays an important role in lung development, but its significance in silicosis is unclear. We showed that in human coal pneumoconiosis autopsy specimens, Sonic Hedgehog (SHH) and the Glioma-associated oncogene homolog transcription factors family (GLI) 1 proteins were up-regulated, whereas Patch-1 (PTC) was down-regulated. The protein levels of SHH, smoothened (SMO), GLI1, GLI2, α-smooth muscle actin (α-SMA) and collagen type Ⅰ (Col Ⅰ) were also elevated gradually in the bronchoalveolar lavage fluid (BALF) of different stages of coal pneumoconiosis patients, dynamic silica-inhalation rat lung tissue and MRC-5 cells induced by Ang II at different time points, whereas the PTC and GLI3 levels were diminished gradually. Ac-SDKP, an active peptide of renin-angiotensin system (RAS), is an anti-fibrotic tetrapeptide. Targeting RAS axis also has anti-silicotic fibrosis effects. However, their roles on the HH pathway are still unknown. Here, we reported that Ac-SDKP + Captopril, Ac-SDKP, Captopril, or Ang (1-7) could alleviate silicotic fibrosis and collagen deposition, as well as improve the lung functions of silicotic rat. These treatments decreased the expression of SHH, SMO, GLI1, GLI2, α-SMA, and Col Ⅰ and increased the expression of PTC and GLI3 on both the silicotic rat lung tissue and MRC-5 cells induced by Ang II. We also reported that Ang II may promote myofibroblast differentiation via the GLI1 transcription factor and independently of the SMO receptor.

An integrin-based nanoparticle that targets activated hepatic stellate cells and alleviates liver fibrosis

Activation of hepatic stellate cells (HSCs) contributes to the development of liver fibrosis. Because of a relatively small population of HSCs in the liver and the lack of specific membrane targeting proteins, HSC-targeted therapy remains a major clinical challenge. Here we first showed that a hallmark of activated HSC (aHSC) is their increased expression of integrin αvβ3. Thus we established sterically stable liposomes that contain the cyclic peptides (cRGDyK) with a high affinity to αvβ3 to achieve aHSC-specific delivery. Our results showed that the cRGDyK-guided liposomes were preferentially internalized by activated HSCs in vitro and in vivo, and the internalization was abolished by excess free cRGDyK or knockdown of αvβ3. In contrast, quiescent HSCs, hepatocytes, Kupffer cells, sinusoidal endothelial cells, or biliary cells showed minimal uptake of the cRGDyK-guided liposomes. When loaded with the hedgehog inhibitor vismodegib, the cRGDyK-guided liposomes inhibited hedgehog pathway signaling specifically in activated HSCs. Moreover, treatment of mice with vismodegib-loaded cRGDyK-liposomes markedly inhibited the fibrogenic phenotype in bile duct ligation- or thioacetamide-treated mice. We conclude that the cRGDyK-guided liposomes can specifically target the activated HSCs, but not quiescent HSCs. This nanoparticle system showed great promise to deliver therapeutic agents to aHSC to treat liver fibrosis.

Recent Insight into the Role of Fibrosis in Nonalcoholic Steatohepatitis-Related Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most widespread tumors in the world and its prognosis is poor because of lack of effective treatments. Epidemiological studies show that non-alcoholic steatohepatitis (NASH) and advanced fibrosis represent a relevant risk factors to the HCC development. However little is known of pathophysiological mechanisms linking liver fibrogenesis to HCC in NASH. Recent advances in scientific research allowed to discover some mechanisms that may represent potential therapeutic targets. These include the integrin signaling, hepatic stellate cells (HSCs) activation, Hedgehog signaling and alteration of immune system. In the near future, knowledge of fibrosis-dependent carcinogenic mechanisms, will help optimize antifibrotic therapies as an approach to prevent and treat HCC in patients with NASH and advanced fibrosis.

Ligustrazin increases lung cell autophagy and ameliorates paraquat-induced pulmonary fibrosis by inhibiting PI3K/Akt/mTOR and hedgehog signalling via increasing miR-193a expression

Background

Reactive oxygen species (ROS) levels largely determine pulmonary fibrosis. Antioxidants have been found to ameliorate lung fibrosis after long-term paraquat (PQ) exposure. The effects of antioxidants, however, on the signalling pathways involved in PQ-induced lung fibrosis have not yet been investigated sufficiently. Here, we examined the impacts of ligustrazin on lung fibrosis, in particular ROS-related autophagy and pro-fibrotic signalling pathways, using a murine model of PQ-induced lung fibrosis.

Methods

We explored the effects of microRNA-193 (miR-193a) on Hedgehog (Hh) and PI3K/Akt/mTOR signalling and oxidative stress in lung tissues. Levels of miR-193a, protein kinase B (Akt), phosphoinositide 3-Kinase (PI3K), ceclin1, mammalian target of rapamycin (mTOR), sonic hedgehog (SHH), myosin-like Bcl2 interacting protein (LC3), smoothened (Smo), and glioma-associated oncogene-1 (Gli-1) mRNAs were determined with quantitative real-time PCR. Protein levels of PI3K, p-mTOR, p-Akt, SHH, beclin1, gGli-1, LC3, smo, transforming growth factor-β1 (TGF-β1), mothers against DPP homologue-2 (Smad2), connective tissue growth factor (CTGF), collagen I, collagen III, α-smooth muscle actin (α-SMA) nuclear factor erythroid 2p45-related factor-2 (Nrf2), and p-Smad2 were detected by western blotting. In addition, α-SMA, malondialdehyde, ROS, superoxide dismutase (SOD), oxidised and reduced glutathione, hydroxyproline, and overall collagen levels were identified in lung tissues using immunohistochemistry.

Results

Long-term PQ exposure blocked miR-193a expression, reduced PI3K/Akt/mTOR signalling, increased oxidative stress, inhibited autophagy, increased Hh signalling, and facilitated the formation of pulmonary fibrosis. Ligustrazin blocked PI3K/Akt/mTOR and Hh signalling as well as reduced oxidative stress via increasing miR-193a expression and autophagy, all of which reduced pulmonary fibrosis. These effects of ligustrazin were accompanied by reduced TGF-β1, CTGF, and Collagen I and III expression.

Conclusions

Ligustrazin blocked PQ-induced PI3K/Akt/mTOR and Hh signalling by increasing miR-193a expression, thereby attenuating PQ-induced lung fibrosis.

Iron and liver fibrosis: Mechanistic and clinical aspects

Liver fibrosis is characterised by excessive deposition of extracellular matrix that interrupts normal liver functionality. It is a pathological stage in several untreated chronic liver diseases such as the iron overload syndrome hereditary haemochromatosis, viral hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis and diabetes. Interestingly, regardless of the aetiology, iron-loading is frequently observed in chronic liver diseases. Excess iron can feed the Fenton reaction to generate unquenchable amounts of free radicals that cause grave cellular and tissue damage and thereby contribute to fibrosis. Moreover, excess iron can induce fibrosis-promoting signals in the parenchymal and non-parenchymal cells, which accelerate disease progression and exacerbate liver pathology. Fibrosis regression is achievable following treatment, but if untreated or unsuccessful, it can progress to the irreversible cirrhotic stage leading to organ failure and hepatocellular carcinoma, where resection or transplantation remain the only curative options. Therefore, understanding the role of iron in liver fibrosis is extremely essential as it can help in formulating iron-related diagnostic, prognostic and treatment strategies. These can be implemented in isolation or in combination with the current approaches to prepone detection, and halt or decelerate fibrosis progression before it reaches the irreparable stage. Thus, this review narrates the role of iron in liver fibrosis. It examines the underlying mechanisms by which excess iron can facilitate fibrotic responses. It describes the role of iron in various clinical pathologies and lastly, highlights the significance and potential of iron-related proteins in the diagnosis and therapeutics of liver fibrosis.

High Risk of Hepatocellular Carcinoma Development in Fibrotic Liver: Role of the Hippo-YAP/TAZ Signaling Pathway

Liver cancer is the fourth leading cause of cancer-related death globally, accounting for approximately 800,000 deaths annually. Hepatocellular carcinoma (HCC) is the most common type of liver cancer, making up about 80% of cases. Liver fibrosis and its end-stage disease, cirrhosis, are major risk factors for HCC. A fibrotic liver typically shows persistent hepatocyte death and compensatory regeneration, chronic inflammation, and an increase in reactive oxygen species, which collaboratively create a tumor-promoting microenvironment via inducing genetic alterations and chromosomal instability, and activating various oncogenic molecular signaling pathways. In this article, we review recent advances in fields of liver fibrosis and carcinogenesis, and consider several molecular signaling pathways that promote hepato-carcinogenesis under the microenvironment of liver fibrosis. In particular, we pay attention to emerging roles of the Hippo-YAP/TAZ signaling pathway in stromal activation, hepatic fibrosis, and liver cancer.

Cancer stem cells in hepatocellular carcinoma: an overview and promising therapeutic strategies

The poor clinical outcome of hepatocellular carcinoma (HCC) patients is ascribed to the resistance of HCC cells to traditional treatments and tumor recurrence after curative therapies. Cancer stem cells (CSCs) have been identified as a small subset of cancer cells which have high capacity for self-renewal, differentiation and tumorigenesis. Recent advances in the field of liver CSCs (LCSCs) have enabled the identification of CSC surface markers and the isolation of CSC subpopulations from HCC cells. Given their central role in cancer initiation, metastasis, recurrence and therapeutic resistance, LCSCs constitute a therapeutic opportunity to achieve cure and prevent relapse of HCC. Thus, it is necessary to develop therapeutic strategies to selectively and efficiently target LCSCs. Small molecular inhibitors targeting the core stemness signaling pathways have been actively pursued and evaluated in preclinical and clinical studies. Other alternative therapeutic strategies include targeting LCSC surface markers, interrupting the CSC microenvironment, and altering the epigenetic state. In this review, we summarize the properties of CSCs in HCC and discuss novel therapeutic strategies that can be used to target LCSCs.

Adult Hepatocytes Are Hedgehog-Responsive Cells in the Setting of Liver Injury: Evidence for Smoothened-Mediated Activation of NF-κB/Epidermal Growth Factor Receptor/Akt in Hepatocytes that Counteract Fas-Induced Apoptosis

Although hedgehog (Hh) signaling pathway is inactive in adult healthy liver, it becomes activated during acute and chronic liver injury and, thus, modulates the reparative process and disease progression. We developed a novel mouse model with liver-specific knockout of Smoothened (Smo LKO), and animals were subjected to Fas-induced liver injury in vivo. Results showed that Smo deletion in hepatocytes enhances Fas-induced liver injury. Activation of Hh signaling in hepatocytes in the setting of Fas-induced injury was indicated by the fact that Jo2 treatment enhanced hepatic expression of Ptch1, Smo, and its downstream target Gli1 in control but not Smo LKO mice. Primary hepatocytes from control mice showed increased Hh signaling activation in response to Jo2 treatment in vitro. On the other hand, the Smo KO hepatocytes were devoid of Hh activation and were more susceptible to Jo2-induced apoptosis. The levels of NF-κB and related signaling molecules, including epidermal growth factor receptor and Akt, were lower in Smo KO livers/hepatocytes than in control livers/hepatocytes. Accordingly, hydrodynamic gene delivery of active NK-κB prevented Jo2-induced liver injury in the Smo LKO mice. Our findings provide important evidence that adult hepatocytes become responsive to Hh signaling through up-regulation of Smo in the setting of Fas-induced liver injury and that such alteration leads to activation of NF-κB/epidermal growth factor receptor/Akt, which counteracts Fas-induced hepatocyte apoptosis.

HMGB1 promotes ductular reaction and tumorigenesis in autophagy-deficient livers

Autophagy is important for liver homeostasis, and the deficiency leads to injury, inflammation, ductular reaction (DR), fibrosis, and tumorigenesis. It is not clear how these events are mechanistically linked to autophagy deficiency. Here, we reveal the role of high-mobility group box 1 (HMGB1) in two of these processes. First, HMGB1 was required for DR, which represents the expansion of hepatic progenitor cells (HPCs) implicated in liver repair and regeneration. DR caused by hepatotoxic diets (3,5-diethoxycarbonyl-1,4-dihydrocollidine [DDC] or choline-deficient, ethionine-supplemented [CDE]) also depended on HMGB1, indicating that HMGB1 may be generally required for DR in various injury scenarios. Second, HMGB1 promoted tumor progression in autophagy-deficient livers. Receptor for advanced glycation end product (RAGE), a receptor for HMGB1, was required in the same two processes and could mediate the proliferative effects of HMBG1 in isolated HPCs. HMGB1 was released from autophagy-deficient hepatocytes independently of cellular injury but depended on NRF2 and the inflammasome, which was activated by NRF2. Pharmacological or genetic activation of NRF2 alone, without disabling autophagy or causing injury, was sufficient to cause inflammasome-dependent HMGB1 release. In conclusion, HMGB1 release is a critical mechanism in hepatic pathogenesis under autophagy-deficient conditions and leads to HPC expansion as well as tumor progression.

Emerging Roles of G Protein-Coupled Receptors in Hepatocellular Carcinoma

Among a great variety of cell surface receptors, the largest superfamily is G protein-coupled receptors (GPCRs), also known as seven-transmembrane domain receptors. GPCRs can modulate diverse signal-transduction pathways through G protein-dependent or independent pathways which involve β-arrestins, G protein receptor kinases (GRKs), ion channels, or Src kinases under physiological and pathological conditions. Recent studies have revealed the crucial role of GPCRs in the tumorigenesis and the development of cancer metastasis. We will sum up the functions of GPCRs—particularly those coupled to chemokines, prostaglandin, lysophosphatidic acid, endothelin, catecholamine, and angiotensin—in the proliferation, invasion, metastasis, and angiogenesis of hepatoma cells and the development of hepatocellular carcinoma (HCC) in this review. We also highlight the potential avenues of GPCR-based therapeutics for HCC.

The hedgehog pathway in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of obesity-associated liver diseases and it has become the major cause of cirrhosis in the Western world. The high prevalence of NAFLD-associated advanced liver disease reflects both the high prevalence of obesity-related fatty liver (hepatic steatosis) and the lack of specific treatments to prevent hepatic steatosis from progressing to more serious forms of liver damage, including nonalcoholic steatohepatitis (NASH), cirrhosis, and primary liver cancer. The pathogenesis of NAFLD is complex, and not fully understood. However, compelling evidence demonstrates that dysregulation of the hedgehog (Hh) pathway is involved in both the pathogenesis of hepatic steatosis and the progression from hepatic steatosis to more serious forms of liver damage. Inhibiting hedgehog signaling enhances hepatic steatosis, a condition which seldom results in liver-related morbidity or mortality. In contrast, excessive Hh pathway activation promotes development of NASH, cirrhosis, and primary liver cancer, the major causes of liver-related deaths. Thus, suppressing excessive Hh pathway activity is a potential approach to prevent progressive liver damage in NAFLD. Various pharmacologic agents that inhibit Hh signaling are available and approved for cancer therapeutics; more are being developed to optimize the benefits and minimize the risks of inhibiting this pathway. In this review we will describe the Hh pathway, summarize the evidence for its role in NAFLD evolution, and discuss the potential role for Hh pathway inhibitors as therapies to prevent NASH, cirrhosis and liver cancer.

Hedgehog signalling in liver pathophysiology

Liver disease remains a leading cause of mortality worldwide despite recent successes in the field of viral hepatitis, because increases in alcohol consumption and obesity are fuelling an epidemic of chronic fatty liver disease for which there are currently no effective medical therapies. About 20% of individuals with chronic liver injury ultimately develop end-stage liver disease due to cirrhosis. Hence, treatments to prevent and reverse cirrhosis in individuals with ongoing liver injury are desperately needed. The development of successful treatments requires an improved understanding of the mechanisms controlling liver disease progression. The liver responds to diverse insults with a conserved wound healing response, suggesting that it might be generally beneficial to optimise pathways that are crucial for effective liver repair. The Hedgehog pathway has emerged as a potential target based on compelling preclinical and clinical data, which demonstrate that it critically regulates the liver's response to injury. Herein, we will summarise evidence of the Hedgehog pathway's role in liver disease and discuss how modulating pathway activity might be applied to improve liver disease outcomes.

Stem-like plasticity and heterogeneity of circulating tumor cells: current status and prospect challenges in liver cancer

Poor prognosis and high recurrence remain leading causes of primary liver cancerassociated mortality. The spread of circulating tumor cells (CTCs) in the blood plays a major role in the initiation of metastasis and tumor recurrence after surgery. Nevertheless, only a subset of CTCs can survive, migrate to distant sites and establish secondary tumors. Consistent with cancer stem cell (CSC) hypothesis, stem-like CTCs might represent a potential source for cancer relapse and distant metastasis. Thus, identification of stem-like metastasis-initiating CTC-subset may provide useful clinically prognostic information. This review will emphasize the most relevant findings of CTCs in the context of stem-like biology associated to liver carcinogenesis. In this view, the emerging field of stem-like CTCs may deliver substantial contribution in liver cancer field in order to move to personalized approaches for diagnosis, prognosis and therapy.

Developmental Morphogens & Recovery from Alcoholic Liver Disease

Alcohol-induced steatohepatitis (ASH) increases the risk for both clinically-severe acute alcoholic hepatitis and eventual cirrhosis. The mechanisms that control ASH pathogenesis and progression are unclear but processes that regulate liver cell plasticity seem to be critically involved. In injured adult livers, morphogenic signaling pathways that modulate cell fate decisions during fetal development and in adult liver progenitors become reactivated. Overly-exuberant activation of such morphogenic signaling causes dysregulated liver repair and increases short- and long-term mortality by promoting acute liver failure, as well as progressive fibrosis. Hence, these pathways may be novel therapeutic targets to optimize liver cell reprogramming and prevent defective regenerative responses that cause acute liver failure and cirrhosis.

Vismodegib

Vismodegib (GDC-0449, Erivedge^®) is a small molecule antagonist of the hedgehog (Hh) pathway that binds to smoothened (SMO) and leads to inhibition of an aberrant activation of the Hh pathway. Dysregulated Hh signaling results in uncontrolled proliferation in basal cell carcinoma (BCC) and has also been found present in medulloblastoma, and many other cancers such as those of gastrointestinal tract, brain, lung, breast, and prostate. In January 2012, vismodegib became the first agent to target the Hh pathway to receive approval by the United States Food and Drug Administration (FDA) and in July 2013 approval by the European Medicines Agency (EMA) followed for the treatment of adult patients with symptomatic metastatic BCC, or locally advanced BCC inappropriate for surgery or radiotherapy. The role of vismodegib in other malignancies than BCC has still to be investigated.

The Hedgehog Signaling Pathway Emerges as a Pathogenic Target

The Hedgehog (Hh) signaling pathway plays an essential role in the growth, development, and homeostatis of many tissues in vertebrates and invertebrates. Much of what is known about Hh signaling is in the context of embryonic development and tumor formation. However, a growing body of evidence is emerging indicating that Hh signaling is also involved in postnatal processes such as tissue repair and adult immune responses. To that extent, Hh signaling has also been shown to be a target for some pathogens that presumably utilize the pathway to control the local infected environment. In this review, we discuss what is currently known regarding pathogenic interactions with Hh signaling and speculate on the reasons for this pathway being a target. We also hope to shed light on the possibility of using small molecule modulators of Hh signaling as effective therapies for a wider range of human diseases beyond their current use in a limited number of cancers.

The Injury-Related Activation of Hedgehog Signaling Pathway Modulates the Repair-Associated Inflammation in Liver Fibrosis

Liver fibrosis is a wound healing response initiated by inflammation responding for different iterative parenchymal damages caused by diverse etiologies. Immune cells, which exert their ability of either inducing injury or promoting repair, have been regarded as crucial participants in the fibrogenic response. A characteristic feature of the fibrotic microenvironment associated with chronic liver injury is aberrant activation of hedgehog (Hh) signaling pathway. Growing evidence from a number of different studies in vivo and in vitro has indicated that immune-mediated events involved in liver fibrogenesis are regulated by Hh signaling pathway. In this review, we emphasize the impacts of injury-activated Hh signaling on liver fibrogenesis through modulating repair-related inflammation and focus on the regulatory action of aberrant Hh signaling on repair-related inflammatory responses mediated by hepatic classical and non-classical immune cell populations in the progression of liver fibrosis. Moreover, we also assess the potentiality of Hh pathway inhibitors as good candidates for anti-fibrotic therapeutic agents because of their immune regulation actions for fibrogenic liver repair. The identification of immune-modulatory mechanisms of Hh signaling pathway underlying the fibrotic process of chronic liver diseases might provide a basis for Hh-centered therapeutic strategies for liver fibrosis.