Hepatic stellate cells promote tumor progression by enhancement of immunosuppressive cells in an orthotopic liver tumor mouse model

The Role of Fibrosis and Liver-Associated Fibroblasts in the Pathogenesis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most aggressive types of cancer and lacks effective therapeutic approaches. Most HCC develops in the setting of chronic liver injury, hepatic inflammation, and fibrosis. Hepatic stellate cells (HSCs) and cancer-associated fibroblasts (CAFs) are key players in liver fibrogenesis and hepatocarcinogenesis, respectively. CAFs, which probably derive from HSCs, activate into extracellular matrix (ECM)-producing myofibroblasts and crosstalk with cancer cells to affect tumor growth and invasion. In this review, we describe the different components which form the HCC premalignant microenvironment (PME) and the tumor microenvironment (TME), focusing on the liver fibrosis process and the biology of CAFs. We will describe the CAF-dependent mechanisms which have been suggested to promote hepatocarcinogenesis, such as the alteration of ECM, CAF-dependent production of cytokines and angiogenic factors, CAF-dependent reduction of immuno-surveillance, and CAF-dependent promotion of epithelial-mesenchymal transition (EMT). New knowledge of the fibrosis process and the role of CAFs in HCC may pave the way for new therapeutic strategies for liver cancer.

The Role of Fibrosis and Liver-Associated Fibroblasts in the Pathogenesis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most aggressive types of cancer and lacks effective therapeutic approaches. Most HCC develops in the setting of chronic liver injury, hepatic inflammation, and fibrosis. Hepatic stellate cells (HSCs) and cancer-associated fibroblasts (CAFs) are key players in liver fibrogenesis and hepatocarcinogenesis, respectively. CAFs, which probably derive from HSCs, activate into extracellular matrix (ECM)-producing myofibroblasts and crosstalk with cancer cells to affect tumor growth and invasion. In this review, we describe the different components which form the HCC premalignant microenvironment (PME) and the tumor microenvironment (TME), focusing on the liver fibrosis process and the biology of CAFs. We will describe the CAF-dependent mechanisms which have been suggested to promote hepatocarcinogenesis, such as the alteration of ECM, CAF-dependent production of cytokines and angiogenic factors, CAF-dependent reduction of immuno-surveillance, and CAF-dependent promotion of epithelial-mesenchymal transition (EMT). New knowledge of the fibrosis process and the role of CAFs in HCC may pave the way for new therapeutic strategies for liver cancer.

Inflammation and Liver Cancer: Molecular Mechanisms and Therapeutic Targets

Hepatocellular carcinoma (HCC) is associated with chronic inflammation and fibrosis arising from different etiologies, including hepatitis B and C and alcoholic and nonalcoholic fatty liver diseases. The inflammatory cytokines tumor necrosis factor-α and interleukin-6 and their downstream targets nuclear factor kappa B (NF-κB), c-Jun N-terminal kinase (JNK), and signal transducer and activator of transcription 3 drive inflammation-associated HCC. Further, while adaptive immunity promotes immune surveillance to eradicate early HCC, adaptive immune cells, such as CD8+ T cells, Th17 cells, and B cells, can also stimulate HCC development. Thus, the role of the hepatic immune system in HCC development is a highly complex topic. This review highlights the role of cytokine signals, NF-κB, JNK, innate and adaptive immunity, and hepatic stellate cells in HCC and discusses whether these pathways could be therapeutic targets. The authors will also discuss cholangiocarcinoma and liver metastasis because biliary inflammation and tumor-associated stroma are essential for cholangiocarcinoma development and because primary tumor-derived inflammatory mediators promote the formation of a "premetastasis niche" in the liver.

Nanoparticle mediated silencing of tenascin C in hepatic stellate cells: effect on inflammatory gene expression and cell migration

Mesoporous silica nanoparticles efficiently knock-down tenascin-C in hepatic stellate cells resulting in decrease of inflammatory cytokine levels and hepatocyte migration.

Multipotent mesenchymal stromal cells play critical roles in hepatocellular carcinoma initiation, progression and therapy

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, with high morbidity, relapse and mortality rates. Multipotent mesenchymal stromal cells (MSCs) can be recruited to and become integral components of the HCC microenvironment and can influence tumor progression. This review discusses MSC migration to liver fibrosis and the HCC microenvironment, MSC involvement in HCC initiation and progression and the widespread application of MSCs in HCC-targeted therapy, thus clarifying the critical roles of MSCs in HCC.

Tumor matrix remodeling and novel immunotherapies: the promise of matrix-derived immune biomarkers

Recent advances in our understanding of the dynamics of cellular cross-talk have highlighted the significance of host-versus-tumor effect that can be harnessed with immune therapies. Tumors exploit immune checkpoints to evade adaptive immune responses. Cancer immunotherapy has witnessed a revolution in the past decade with the development of immune checkpoint inhibitors (ICIs), monoclonal antibodies against cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed cell death protein 1 (PD-1) or their ligands, such as PD1 ligand 1 (PD-L1). ICIs have been reported to have activity against a broad range of tumor types, in both solid organ and hematologic malignancy contexts. However, less than one-third of the patients achieve a durable and meaningful treatment response. Expression of immune checkpoint ligands (e.g., PD-L1), mutational burden and tumor-infiltrating lymphocytes are currently used as biomarkers for predicting response to ICIs. However, they do not reliably predict which patients will benefit from these therapies. There is dire need to discover novel biomarkers to predict treatment efficacy and to identify areas for development of combination strategies to improve response rates. Emerging evidence suggests key roles of tumor extracellular matrix (ECM) components and their proteolytic remodeling products in regulating each step of the cancer-immunity cycle. Here we review tumor matrix dynamics and matrix remodeling in context of anti-tumor immune responses and immunotherapy and propose the exploration of matrix-based biomarkers to identify candidates for immune therapy.

MiRNA-22 inhibits oncogene galectin-1 in hepatocellular carcinoma

Hepatic stellate cells (HSCs) induce immune privilege and promote hepatocellular carcinoma (HCC) by suppressing the immune system. On the other hand, galectin-1 and miRNA-22 (miR-22) are dysregulated in HCC and serve as prognostic indicators for patients. In this study, therefore, we measured galectin-1 and miR-22 expression in HSCs isolated from HCC tissues (Ca-HSCs), and in normal liver tissues (N-HSCs) as a control. We also investigated the apoptosis rate among T cells and the production of cytokines (IFN-η and IL-10) in HSCs co-cultured with T cells. And we used immunohistochemical staining to tested for correlation between galectin-1 expression, CD3 expression and clinicopathological features in 162 HCC patients. Our results showed that galectin-1 expression was much higher in Ca-HSCs than in N-HSCs. Overexpression of galectin-1 promoted HSC-induced T cell apoptosis and cytokine production (IFN-η and IL-10), while miR-22 expression inhibited it. Galectin-1 expression correlated negatively with miR-22 expression in HSCs. High galectin-1 and low CD3 expression levels were associated with poor prognosis in HCC patients. These results suggest that the immunosuppressive microenvironment promoted by HSC-derived galectin-1 in HCC can be inhibited by miR-22. Galectin-1 and miR-22 could potentially serve as prognostic markers and therapeutic targets in HCC.

Mesenchymal-myeloid interaction in the regulation of immunity

Several studies have demonstrated how different cell types of mesenchymal and myeloid origin can independently exhibit immunoregulatory activities. In response to inflammatory cues, they transcribe a molecular repertoire that restores the tissue microenvironment to what it was before the injury. There is accumulating evidence that stromal and myeloid-derived cells do not act independently but that the establishment of a cross-talk between them is a fundamental requirement. Stromal cells, prompted by inflammatory molecules, orchestrate and initiate myeloid cell recruitment and their functional reprogramming. Once instructed, myeloid cells effect the anti-inflammatory activity or, if alternatively required, enhance immune responses. The cross-talk plays a fundamental role in tissue homeostasis, not only to regulate inflammation, but also to promote tissue regeneration and cancer progression.

Lipopolysaccharide promotes angiogenesis in mice model of HCC by stimulating hepatic stellate cell activation via TLR4 pathway

Angiogenesis plays a key role in the progression of hepatocellular carcinoma (HCC). This study aimed to investigate whether lipopolysaccharide (LPS) could promote HCC angiogenesis and the role of hepatic stellate cell (HSC) in this process. In vivo orthotopic HCC model and the effect of LPS on HSC in vitro were studied. Our results demonstrated that LPS-induced HSC activation during the promotion of HCC growth and angiogenesis in mice. The LPS-TLR4 (Toll-like receptor 4) pathway in HSC is responsible for HCC angiogenesis. LPS-induced secretion of pro-angiogenic factors from HSC could promote endothelial cell migration and tubulogenesis. This study suggests that LPS acts with HSC in tumor stroma and promotes the secretion of pro-angiogenic factors that increase angiogenesis in HCC.

Molecular Pathways: Targeting the Microenvironment of Liver Metastases

Curative treatment for metastatic solid cancers remains elusive. The liver, which is nourished by a rich blood supply from both the arterial and portal venous systems, is the most common site of visceral metastases, particularly from cancers arising in the gastrointestinal tract, with colorectal cancer being the predominant primary site in Western countries. A mounting body of evidence suggests that the liver microenvironment (LME) provides autocrine and paracrine signals originating from both parenchymal and nonparenchymal cells that collectively create both pre- and prometastatic niches for the development of hepatic metastases. These resident cells and their molecular mediators represent potential therapeutic targets for the prevention and/or treatment of liver metastases (LM). This review summarizes: (i) the current therapeutic options for treating LM, with a particular focus on colorectal cancer LM; (ii) the role of the LME in LM at each of its phases; (iii) potential targets in the LME identified through preclinical and clinical investigations; and (iv) potential therapeutic approaches for targeting elements of the LME before and/or after the onset of LM as the basis for future clinical trials. Clin Cancer Res; 23(21); 6390-9. ©2017 AACR.

The expression of ETAR in liver cirrhosis and liver cancer

BACKGROUND

To investigate the expression of endothelin receptors in liver diseases and discuss its role in the process of liver cirrhosis and liver cancer.

RESEARCH DESIGN AND METHODS

We examined the expressions of ETAR, ETBR and α-SMA in tissue samples using western blotting analysis. Furthermore, immunofluorescence was used to locate ETAR expression in hepatic stellate cells (HSCs) and hepatic sinusoidal endothelial cells (HSECs), we calculated the percentage of positive cells and then analyzed its relation with clinical indexes.

RESULTS

According to the western blotting analysis, the expression of ETAR was high in hepatic hemangioma and liver cancer tissues and ETBR was highly expressed in cirrhosis tissues. The immunofluorescence results demonstrated that the expression of ETAR was elevated in hepatic hemangioma and liver cancer tissues. Moreover, ETAR expression was found in both HSCs and HSECs. Finally, the statistical analysis revealed that the number of positive ETAR cells was correlated with the clinical index platelets (PLT), alanine transaminase (ALT) and diameter of portal vein.

CONCLUSION

Endothelin receptors express differently in liver cirrhosis and liver cancer tissues and play a role in hepatic diseases by affecting HSCs and HSECs.

Role of liver ICAM-1 in metastasis

Intercellular adhesion molecule (ICAM)-1, is a transmembrane glycoprotein of the immunoglobulin (Ig)-like superfamily, consisting of five extracellular Ig-like domains, a transmembrane domain and a short cytoplasmic tail. ICAM-1 is expressed in various cell types, including endothelial cells and leukocytes, and is involved in several physiological processes. Furthermore, it has additionally been reported to be expressed in various cancer cells, including melanoma, colorectal cancer and lymphoma. The majority of studies to date have focused on the expression of the ICAM-1 on the surface of tumor cells, without research into ICAM-1 expression at sites of metastasis. Cancer cells frequently metastasize to the liver, due to its unique physiology and specialized liver sinusoid capillary network. Liver sinusoidal endothelial cells constitutively express ICAM-1, which is upregulated under inflammatory conditions. Furthermore, liver ICAM-1 may be important during the development of liver metastasis. Therefore, it is necessary to improve the understanding of the mechanisms mediated by this adhesion molecule in order to develop host-directed anticancer therapies.

Tumor Microenvironment, a Paradigm in Hepatocellular Carcinoma Progression and Therapy

Hepatocellular carcinoma (HCC) is among the most lethal and prevalent cancers in the human population. Different etiological factors such as hepatitis B and C virus, alcohol and diabetes cause liver injury followed by inflammation, necrosis and hepatocytes proliferation. Continuous cycles of this destructive-regenerative process culminates in liver cirrhosis which is characterized by regenerating nodules that progress to dysplastic nodules and ultimately HCC. Despite its significance, there is only an elemental understanding of the pathogenetic mechanisms, and there are only limited therapeutic options. Therefore, the study of the involved molecular mechanisms can open a new insight to define more effective treatment strategies. A variety of alterations have been reported in HCC patients, particularly the cancer-associated microenvironment components including immune cells, fibroblast cells, endothelial cells and extracellular matrix can support the neoplastic cells to proliferate, growth and invade. This review summarizes the current state of knowledge and highlights the principal challenges that are relevant to controlling this milieu.

Tumor Microenvironment, a Paradigm in Hepatocellular Carcinoma Progression and Therapy

Hepatocellular carcinoma (HCC) is among the most lethal and prevalent cancers in the human population. Different etiological factors such as hepatitis B and C virus, alcohol and diabetes cause liver injury followed by inflammation, necrosis and hepatocytes proliferation. Continuous cycles of this destructive–regenerative process culminates in liver cirrhosis which is characterized by regenerating nodules that progress to dysplastic nodules and ultimately HCC. Despite its significance, there is only an elemental understanding of the pathogenetic mechanisms, and there are only limited therapeutic options. Therefore, the study of the involved molecular mechanisms can open a new insight to define more effective treatment strategies. A variety of alterations have been reported in HCC patients, particularly the cancer-associated microenvironment components including immune cells, fibroblast cells, endothelial cells and extracellular matrix can support the neoplastic cells to proliferate, growth and invade. This review summarizes the current state of knowledge and highlights the principal challenges that are relevant to controlling this milieu.

Tumour-activated liver stromal cells regulate myeloid-derived suppressor cells accumulation in the liver

Regulating mechanisms underlying hepatic myeloid-derived suppressor cell (MDSC) accumulation remain to be described. Here, we provide evidence for the involvement of tumour-activated liver stromal cells in the process of hepatic MDSCs migration and accumulation. Our data showed an elevated frequency of MDSCs in the liver of tumour-bearing mice. Moreover, tumour-activated liver stromal cells promote MDSC migration into the liver site. Further investigation indicated higher levels of cytokine and chemokine expression in liver stromal cells after exposure to the tumour-conditioned supernatant. Notably, the expression levels of proinflammatory factors, mainly including macrophage colony stimulating factor (M-CSF), transforming growth factor-β (TGF-β), monocyte chemotactic protein-1 (MCP-1) and stromal-derived factor-1 (SDF-1), increased after treatment with tumour-conditioned supernatant, and blockade of MCP-1 or SDF-1 decreased the proportion of tumour infiltrated MDSCs in mice co-transplanted with liver stromal cells and tumour cells, but not in mice with only tumour cells injection. These findings demonstrate that tumour-activated liver stromal cells produce higher levels of chemokines and cytokines, which may contribute to MDSC accumulation into the liver site in patients with liver cancer.

Tumor regulation of the tissue environment in the liver

The tumor microenvironment (TME) in the liver plays an important role in primary and metastatic liver tumor formation and tumor growth promotion. Cellular and non-cellular components of the TME significantly influence tumor development, growth, metastatic spread, anti-tumor immunity and response to tumor therapy. The cellular components of the TME in the liver not only consist of infiltrating immune cells, but also of liver-resident cells such as liver sinusoidal endothelial cells (LSEC) and hepatic stellate cells (HSC), which promote tumor growth by negatively regulating tumor-associated immune responses. In this review, we characterize cells of the TME with pro- and anti-tumor function in primary and metastatic liver tumors. Furthermore, we summarize mechanisms that permit growth of hepatic tumors despite the occurrence of spontaneous anti-tumor immune responses and how novel therapeutic approaches targeting the TME could unleash tumor-specific immune responses to improve survival of liver cancer patients.

Activated hepatic stellate cells promote liver cancer by induction of myeloid-derived suppressor cells through cyclooxygenase-2

Hepatic stellate cells (HSCs) are critical mediators of immunosuppression and the pathogenesis of hepatocellular carcinoma (HCC). Our previous work indicates that HSCs promote HCC progression by enhancing immunosuppressive cell populations including myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). MDSCs are induced by inflammatory cytokines (e.g., prostaglandins) and are important in immune suppression. However, how HSCs mediate expansion of MDSCs is uncertain. Thus, we studied activated HSCs that could induce MDSCs from bone marrow cells and noted that HSC-induced MDSCs up-regulated immunosuppressive activity via iNOS, Arg-1, and IL-4Rα. After treating cells with a COX-2 inhibitor or an EP4 antagonist, we established that HSC-induced MDSC accumulation was mediated by the COX2-PGE₂-EP4 signaling. Furthermore, in vivo animal studies confirmed that inhibition of HSC-derived PGE₂ could inhibit HSC-induced MDSC accumulation and HCC growth. Thus, our data show that HSCs are required for MDSC accumulation mediated by the COX2-PGE₂-EP4 pathway, and these data are the first to link HSC and MDSC subsets in HCC immune microenvironment and provide a rationale for targeting PGE₂ signaling for HCC therapy.

The Role of Cancer-Associated Fibroblasts and Fibrosis in Liver Cancer

Liver cancer is the second leading cause of cancer mortality worldwide, causing more than 700,000 deaths annually. Because of the wide landscape of genomic alterations and limited therapeutic success of targeting tumor cells, a recent focus has been on better understanding and possibly targeting the microenvironment in which liver tumors develop. A unique feature of liver cancer is its close association with liver fibrosis. More than 80% of hepatocellular carcinomas (HCCs) develop in fibrotic or cirrhotic livers, suggesting an important role of liver fibrosis in the premalignant environment (PME) of the liver. Cholangiocarcinoma (CCA), in contrast, is characterized by a strong desmoplasia that typically occurs in response to the tumor, suggesting a key role of cancer-associated fibroblasts (CAFs) and fibrosis in its tumor microenvironment (TME). Here, we discuss the functional contributions of myofibroblasts, CAFs, and fibrosis to the development of HCC and CCA in the hepatic PME and TME, focusing on myofibroblast- and extracellular matrix-associated growth factors, fibrosis-associated immunosuppressive pathways, as well as mechanosensitive signaling cascades that are activated by increased tissue stiffness. Better understanding of the role of myofibroblasts in HCC and CCA development and progression may provide the basis to target these cells for tumor prevention or therapy.

Role of the Microenvironment in Liver Metastasis: From Pre- to Prometastatic Niches

Liver metastases remain a major barrier to successful management of malignant disease, particularly for cancers of the gastrointestinal tract but also for other malignancies, such as breast carcinoma and melanoma. The ability of metastatic cells to survive and proliferate in the liver is determined by the outcome of complex, reciprocal interactions between tumor cells and different local resident subpopulations, including the sinusoidal endothelium, stellate, Kupffer, and inflammatory cells that are mediated through cell-cell and cell-extracellular matrix adhesion and the release of soluble factors. Cross-communication between different hepatic resident cells in response to local tissue damage and inflammation and the recruitment of bone marrow cells further enhance this intercellular communication network. Both resident and recruited cells can play opposing roles in the progression of metastasis, and the balance of these divergent effects determines whether the tumor cells will die, proliferate, and colonize the new site or enter a state of dormancy. Moreover, this delicate balance can be tilted in favor of metastasis, if factors produced by the primary tumor precondition the microenvironment to form niches of activated resident cells that promote tumor expansion. This review aims to summarize current knowledge on these diverse interactions and the impact they can have on the clinical management of hepatic metastases. Clin Cancer Res; 22(24); 5971-82. ©2016 AACR.

Mouse models of liver cancer: Progress and recommendations

To clarify the pathogenesis of hepatocellular carcinoma (HCC) and investigate the effects of potential therapies, a number of mouse models have been developed. Subcutaneous xenograft models are widely used in the past decades. Yet, with the advent of in vivo imaging technology, investigators are more and more concerned with the orthotopic models nowadays. Genetically engineered mouse models (GEM) have greatly facilitated studies of gene function in HCC development. Recently, GEM of miR-122 and miR-221 provided new approaches for better understanding of the in vivo functions of microRNA in hepatocarcinogenesis. Chemically induced liver tumors in animals share many of the morphological, histogenic, and biochemical features of human HCC. Yet, the complicated and obscure genomic alternation restricts their applications. In this review, we highlight both the frequently used mouse models and some emerging ones with emphasis on their merits or defects, and give advises for investigators to chose a “best-fit” animal model in HCC research.

Proteinase-activated receptor 2 (PAR2) in hepatic stellate cells - evidence for a role in hepatocellular carcinoma growth in vivo

BACKGROUND

Previous studies have established that proteinase-activated receptor 2 (PAR2) promotes migration and invasion of hepatocellular carcinoma (HCC) cells, suggesting a role in HCC progression. Here, we assessed the impact of PAR2 in HCC stromal cells on HCC growth using LX-2 hepatic stellate cells (HSCs) and Hep3B cells as model.

METHODS

PAR2 expression and function in LX-2 cells was analysed by RT-PCR, confocal immunofluorescence, electron microscopy, and [Ca(2+)]i measurements, respectively. The impact of LX-2-expressed PAR2 on tumour growth in vivo was monitored using HCC xenotransplantation experiments in SCID mice, in which HCC-like tumours were induced by coinjection of LX-2 cells and Hep3B cells. To characterise the effects of PAR2 activation in LX-2 cells, various signalling pathways were analysed by immunoblotting and proteome profiler arrays.

RESULTS

Following verification of functional PAR2 expression in LX-2 cells, in vivo studies showed that these cells promoted tumour growth and angiogenesis of HCC xenografts in mice. These effects were significantly reduced when F2RL1 (encoding PAR2) was downregulated by RNA interference (RNAi). In vitro studies confirmed these results demonstrating RNAi mediated inhibition of PAR2 attenuated Smad2/3 activation in response to TGF-β1 stimulation in LX-2 cells and blocked the pro-mitotic effect of LX-2 derived conditioned medium on Hep3B cells. Furthermore, PAR2 stimulation with trypsin or a PAR2-selective activating peptide (PAR2-AP) led to activation of different intracellular signalling pathways, an increased secretion of pro-angiogenic and pro-mitotic factors and proteinases, and an enhanced migration rate across a collagen-coated membrane barrier. Silencing F2RL1 by RNAi or pharmacological inhibition of Src, hepatocyte growth factor receptor (Met), platelet-derived growth factor receptor (PDGFR), p42/p44 mitogen activated protein kinase (MAPK) or matrix-metalloproteinases (MMPs) blocked PAR2-AP-induced migration.

CONCLUSION

PAR2 in HSCs plays a crucial role in promoting HCC growth presumably by mediating migration and secretion of pro-angiogenic and pro-mitotic factors. Therefore, PAR2 in stromal HSCs may have relevance as a therapeutic target of HCC.

Roles of hepatic stellate cells in liver inflammation: a new perspective

Connected with the intestinal tract through the portal circulation, liver sinusoids function as the first line of defense against extrahepatic stimuli such as bacterial products and other toxic substances. Hepatic stellate cells (HSCs) are pericytes residing in the perisinusoidal space, between sinusoidal endothelial cells and hepatocytes, store vitamin A, and regulate sinusoidal circulation. Following chronic hepatitis, HSCs actively produce extracellular matrices and cause liver fibrosis. In spite of their close position to the liver sinusoids, however, whether HSCs contribute to liver inflammation has remained elusive. Evidence now accumulates to suggest that HSCs actively take part in the regulation of various forms of liver inflammation. Upon inflammatory stimuli from the sinusoids, HSCs produce various inflammatory molecules and interact with other liver cells, thereby recruiting and then activating infiltrating leukocytes and ultimately causing hepatocyte death. On the other hand, HSCs also exert hepatoprotective effects through inhibition of cytokine and chemokine production or induction of immunosuppressive cell population. HSCs therefore integrate cytokine-mediated inflammatory responses in the sinusoids and relay them to the liver parenchyma, either amplifying liver inflammation or suppressing parenchymal damage through immunoregulatory signaling depending on the context.

Abscopal Effects and Yttrium-90 Radioembolization

We present the case of an 80-year-old male with squamous cell carcinoma with bilobar hepatic metastases who underwent targeted Yttrium-90 radioembolization of the right hepatic lobe lesion. Subsequently, there was complete regression of the nontargeted, left hepatic lobe lesion. This may represent the first ever reported abscopal effect in radioembolization. The abscopal effect refers to the phenomenon of tumor response in nontargeted sites after targeted radiotherapy. In this article, we briefly review the immune-mediated mechanisms responsible for the abscopal effect.

Hepatoma cell-derived leptin downregulates the immunosuppressive function of regulatory T-cells to enhance the anti-tumor activity of CD8+ T-cells

The adaptive immune response against hepatocellular carcinoma (HCC) could be a therapeutic target to restrain HCC initiation and growth. The interactions between hepatoma cells and immune cells modify the anti-tumor immunity to influence hepatoma cell survival. To explore the potential interplay between hepatoma cells and anti-HCC T-cells, we conducted a HCC induction mouse model to analyze the phenotypic and functional alterations of T-cell subsets. We found that both hepatoma tissues and hepatoma cell lines substantially produced higher leptin, which is an adipokine usually expressed in fat tissue, than normal liver tissue or hepatocytes. We also found that regulatory T-cells (Tregs), effector CD4(+) T-cells and CD8(+) T-cells upregulated expression of leptin receptor (LEPR) in spleens and livers after HCC induction. In vitro study showed that macrophages and dendritic cells isolated from HCC livers upregulated LEPR expression on T-cells. Leptin inhibited Treg activation and function in vitro, demonstrated by lower expression of TGF-β, IL-10, CTLA4 and GITR in Tregs, as wells weaker suppression of CD8(+) T-cell proliferation and production of cytotoxic mediators. In addition, silencing LEPR in Tregs favored tumor growth in a hepatoma cell line allograft model. Taken together, our study suggests that hepatoma cells could enhance anti-HCC immunity through secreting leptin to down-regulate Treg activity and subsequently promote CD8(+) T-cell response.

Diet-Induced Obesity Enhances Progression of Hepatocellular Carcinoma through Tenascin-C/Toll-Like Receptor 4 Signaling

Obesity is an independent risk factor for the development of liver fibrosis/cirrhosis and hepatocellular carcinoma (HCC). Tenascin-C (TnC), an extracellular matrix protein, is transiently expressed during tissue injury and plays a role in fibrogenesis and tumorigenesis. However, the mechanistic role of TnC signaling in the development of HCC remains unknown. We developed a diet-induced obesity HCC mouse model and examined TnC expression and liver injury. To determine the cellular mechanism of TnC signaling in promoting inflammation and hepatocyte epithelial-mesenchymal transition and migration, we used primary hepatocytes and hepatoma and macrophage cell lines. Further, to determine whether elevated TnC expression correlated with obesity-associated HCC, we measured plasma TnC in obese patients with various levels of liver injury. Increased tissue inflammation accompanied with elevated hepatic stellate cell-derived TnC and Toll-like receptor 4 expression was observed in the diet-induced obesity HCC animal model. In vitro studies found enhanced Toll-like receptor 4 signaling activated by TnC, promoting an increased inflammatory response, hepatocyte transformation, and migration. Further, obese patients with cirrhosis alone and in combination with HCC showed significant increases in plasma TnC compared with healthy volunteers and patients with less severe liver injury. Overall, these studies suggest TnC/Toll-like receptor 4 signaling as an important regulator in HCC; inhibiting this signaling axis may be a viable therapeutic target for impeding HCC.

Immunological hallmarks of stromal cells in the tumour microenvironment

A dynamic and mutualistic interaction between tumour cells and the surrounding stroma promotes the initiation, progression, metastasis and chemoresistance of solid tumours. Far less understood is the relationship between the stroma and tumour-infiltrating leukocytes; however, emerging evidence suggests that the stromal compartment can shape antitumour immunity and responsiveness to immunotherapy. Thus, there is growing interest in elucidating the immunomodulatory roles of the stroma that evolve within the tumour microenvironment. In this Review, we discuss the evidence that stromal determinants interact with leukocytes and influence antitumour immunity, with emphasis on the immunological attributes of stromal cells that may foster their protumorigenic function.

Metformin inhibits angiogenesis induced by interaction of hepatocellular carcinoma with hepatic stellate cells

Accumulated evidences indicate metformin is associated with reduced risk of hepatocellular carcinoma (HCC) in diabetic patients, which inspired researchers to explore its therapeutic potentials in HCC. Since Hepatic stellate cells (HSCs) are believed to be the key contributors to tumor microenvironment in HCC and promotes tumor development, here, we explored the effect of metformin on tumor angiogenesis induced by interplay of HCC and HSCs. Our results showed that conditional medium from co-culture of HCC/HSCs induced VEGF secretions and stimulated human umbilical vein endothelial cells (HUVEC) tube formation. However, 25 µM metformin could inhibit this angiogenesis effect. Furthermore, knockdown AMPK of HSCs, not HCC, could abolish inhibition caused by metformin. Our finding suggested that metformin could inhibit HCC angiogenesis through targeting on HSCs through AMPK pathway.

Hepatocellular carcinoma treatment over sorafenib: epigenetics, microRNAs and microenvironment. Is there a light at the end of the tunnel?

INTRODUCTION

Sorafenib is currently the only approved therapy in hepatocellular carcinoma (HCC). Alternative first- and second-line treatments are a significant unmet medical need, and several biologic agents have been tested in recent years, with poor results. Therefore, angiogenic pathways and the cytokine cascade remain possible targets in HCC. Recent studies suggest a role of epigenetic processes, associated with the initiation and development of HCC. In this field, DNA methylation, micro-RNAs (miRNAs) and tumor microenvironment cells became a possible new target for HCC treatment.

AREAS COVERED

This review explains the possible role of DNA methylation and histone deacetylase inhibitors as predictive biomarkers and target therapy, the extensive world of the promising miRNA blockade strategy, and the recent strong evidence of correlation between HCC tumors and peritumoral stroma cells. The literature and preclinic/clinic data were obtained through an electronic search.

EXPERT OPINION

Future research should aim to understand how best to identify patient groups that would benefit most from the prescribed therapy. To overcome the 'therapeutic stranding' of HCC, a possible way out from the current therapeutic tunnel might be to evaluate the major epigenetic and genetic processes involved in HCC carcinogenesis, not underestimating the tumor microenvironment and its 'actors' (angiogenesis, immune system, platelets). We are only at the start of a long journey towards the elucidation of HCC molecular pathways as therapeutic targets. Yet, currently this path appears to be the only one to cast some light at the end of the tunnel.

Metabolic regulation of hepatitis B immunopathology by myeloid-derived suppressor cells

Infection with hepatitis B virus (HBV) results in disparate degrees of tissue injury: the virus can either replicate without pathological consequences or trigger immune-mediated necroinflammatory liver damage. We investigated the potential for myeloid-derived suppressor cells (MDSCs) to suppress T cell-mediated immunopathology in this setting. Granulocytic MDSCs (gMDSCs) expanded transiently in acute resolving HBV, decreasing in frequency prior to peak hepatic injury. In persistent infection, arginase-expressing gMDSCs (and circulating arginase) increased most in disease phases characterized by HBV replication without immunopathology, whilst L-arginine decreased. gMDSCs expressed liver-homing chemokine receptors and accumulated in the liver, their expansion supported by hepatic stellate cells. We provide in vitro and ex vivo evidence that gMDSCs potently inhibited T cells in a partially arginase-dependent manner. L-arginine-deprived T cells upregulated system L amino acid transporters to increase uptake of essential nutrients and attempt metabolic reprogramming. These data demonstrate the capacity of expanded arginase-expressing gMDSCs to regulate liver immunopathology in HBV infection.

Hepatic stellate cells: central modulators of hepatic carcinogenesis

Hepatocellular carcinoma (HCC) represents the second most common cause of cancer-related death worldwide, and is increasing in incidence. Currently, our therapeutic repertoire for the treatment of HCC is severely limited, and therefore effective new therapies are urgently required. Recently, there has been increasing interest focusing on the cellular and molecular interactions between cancer cells and their microenvironment. HCC represents a unique opportunity to study the relationship between a diseased stroma and promotion of carcinogenesis, as 90 % of HCCs arise in a cirrhotic liver. Hepatic stellate cells (HSC) are the major source of extracellular proteins during fibrogenesis, and may directly, or via secreted products, contribute to tumour initiation and progression. In this review we explore the complex cellular and molecular interplay between HSC biology and hepatocarcinogenesis. We focus on the molecular mechanisms by which HSC modulate HCC growth, immune cell evasion and angiogenesis. This is followed by a discussion of recent progress in the field in understanding the mechanistic crosstalk between HSC and HCC, and the pathways that are potentially amenable to therapeutic intervention. Furthermore, we summarise the exciting recent developments in strategies to target HSC specifically, and novel techniques to deliver pharmaceutical agents directly to HSC, potentially allowing tailored, cell-specific therapy for HCC.

Cluster of differentiation 147 is a key molecule during hepatocellular carcinoma cell-hepatic stellate cell cross-talk in the rat liver

The cross-talk between hepatocellular carcinoma (HCC) cells and activated hepatic stellate cells (HSCs) is considered to be important for modulating the biological behavior of tumor cells. However, the molecular links between inflammation and cancer in the activation of HSCs remain to be elucidated. The present study demonstrated that cluster of differentiation (CD)147 is a key molecule involved in the interaction between HCC cells and HSCs. The effects of conditioned medium from human HCC cells on the activation of the human HSC line, LX-2, were assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blotting, RT-qPCR and gelatin zymography were also used to investigate the effects of CD147 on the activation of LX-2. The expression levels of α-smooth muscle actin (α-SMA) and CD147 were assessed in a co-culture system of LX-2 and FHCC-98 cells by immunofluorescence staining and immunoblotting. In hepatic tissues from a rat model of fibrosis, immunohistochemistry and immunoblotting were performed to detect the expression levels of α-SMA and CD147. Tumor-conditioned medium and CD147 promoted cell proliferation, activated LX-2 cells, increased the expression levels of α-SMA, collagen I and tissue inhibitor of metalloproteinase-1 (TIMP-1), and increased the secretion of matrix metalloproteinase (MMP)-2. The HSCs, which were induced in the co-culture system of HCC cells and HSCs exhibited marked expression levels of CD147. In the hepatic tissue of rat models of fibrosis induced by CCl4, marked expression levels of CD147 were observed in the activated HSCs. Therefore, CD147 promoted the activation of HSCs and was a key molecule during HCC cell-HSC cross-talk in the rat liver.

Targeting the tumor stroma in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and deadly cancers worldwide. In ninety percent of the cases it develops as a result of chronic liver damage and it is thus a typical inflammation-related cancer characterized by the close relation between the tumor microenvironment and tumor cells. The stromal environment consists out of several cell types, including hepatic stellate cells, macrophages and endothelial cells. They are not just active bystanders in the pathogenesis of HCC, but play an important and active role in tumor initiation, progression and metastasis. Furthermore, the tumor itself influences these cells to create a background that is beneficial for sustaining tumor growth. One of the key players is the hepatic stellate cell, which is activated during liver damage and differentiates towards a myofibroblast-like cell. Activated stellate cells are responsible for the deposition of extracellular matrix, increase the production of angiogenic factors and stimulate the recruitment of macrophages. The increase of angiogenic factors (which are secreted by macrophages, tumor cells and activated stellate cells) will induce the formation of new blood vessels, thereby supplying the tumor with more oxygen and nutrients, thus supporting tumor growth and offering a passageway in the circulatory system. In addition, the secretion of chemokines by the tumor cells leads to the recruitment of tumor associated macrophages. These tumor associated macrophages are key actors of cancer-related inflammation, being the main type of inflammatory cells infiltrating the tumor environment and exerting a tumor promoting effect by secreting growth factors, stimulating angiogenesis and influencing the activation of stellate cells. This complex interplay between the several cell types involved in liver cancer emphasizes the need for targeting the tumor stroma in HCC patients.

Cellular and molecular functions of hepatic stellate cells in inflammatory responses and liver immunology

The liver is a central immunological organ. Liver resident macrophages, Kupffer cells (KC), but also sinusoidal endothelial cells, dendritic cells (DC) and other immune cells are involved in balancing immunity and tolerance against pathogens, commensals or food antigens. Hepatic stellate cells (HSCs) have been primarily characterized as the main effector cells in liver fibrosis, due to their capacity to transdifferentiate into collagen-producing myofibroblasts (MFB). More recent studies elucidated the fundamental role of HSC in liver immunology. HSC are not only the major storage site for dietary vitamin A (Vit A) (retinol, retinoic acid), which is essential for proper function of the immune system. This pericyte further represents a versatile source of many soluble immunological active factors including cytokines [e.g., interleukin 17 (IL-17)] and chemokines [C-C motif chemokine (ligand) 2 (CCL2)], may act as an antigen presenting cell (APC), and has autophagy activity. Additionally, it responds to many immunological triggers via toll-like receptors (TLR) (e.g., TLR4, TLR9) and transduces signals through pathways and mediators traditionally found in immune cells, including the Hedgehog (Hh) pathway or inflammasome activation. Overall, HSC promote rather immune-suppressive responses in homeostasis, like induction of regulatory T cells (Treg), T cell apoptosis (via B7-H1, PDL-1) or inhibition of cytotoxic CD8 T cells. In conditions of liver injury, HSC are important sensors of altered tissue integrity and initiators of innate immune cell activation. Vice versa, several immune cell subtypes interact directly or via soluble mediators with HSC. Such interactions include the mutual activation of HSC (towards MFB) and macrophages or pro-apoptotic signals from natural killer (NK), natural killer T (NKT) and gamma-delta T cells (γδ T-cells) on activated HSC. Current directions of research investigate the immune-modulating functions of HSC in the environment of liver tumors, cellular heterogeneity or interactions promoting HSC deactivation during resolution of liver fibrosis. Understanding the role of HSC as central regulators of liver immunology may lead to novel therapeutic strategies for chronic liver diseases.

Immunotherapy of hepatocellular carcinoma

Newer immunotherapy agents may break the barrier that tumors create to evade the attack from the immune system. Dendritic cell vaccination has shown encouraging clinical activity and a favorable safety profile in advanced tumor stages. However, optimal cell maturation status, choice of tumor antigens and route of administration have not been established. Single or multiple peptides derived from tumor-associated antigens may also be used for cancer vaccination. Intratumoral delivery of oncolytic viruses expressing immunostimulating cytokines like GM-CSF have produced stimulating clinical results that need further verification. But it is probably T-cell checkpoint modulation with monoclonal antibodies that has attracted the highest expectations. Promising activity has been reported for tremelimumab, a CTLA-4 inhibitor, and a clinical trial testing the PD-1 antibody nivolumab is underway. Future progress will probably come from a better understanding of the mechanisms of cancer-related immunosuppression, improvement in agents and strategies and combination of the available therapeutic tools.

Albumin-drug conjugates in the treatment of hepatic disorders

INTRODUCTION

This review deals with the use of serum albumin (SA) as a carrier for the selective delivery of drugs to liver cells.

AREAS COVERED

The synthesis and properties of the SA conjugates prepared to enhance the performance of the drugs used in the treatment of viral hepatitis, hepatocellular carcinoma (HCC), liver micrometastases and hepatic fibrosis are reported.

EXPERT OPINION

Studies in humans and laboratory animals demonstrated the capacity of SA conjugates to accomplish a liver targeting of the drugs, but at the same time underscored their limits and drawbacks, which can explain why to date these complexes did not reach a practical application. The major drawback is the need of administration by intravenous route, which prevents long-term daily treatments as required by some liver pathologies, such as chronic virus hepatitis and fibrosis. At present, only a conjugate carrying doxorubicin and addressed to the treatment of HCC showed in laboratory animals a solid potentiality to improve the value of the coupled drug. In the future, conjugation to SA could remain a successful strategy to permit the administration of drugs with rapid resolutive effects inside liver cells without causing severe extrahepatic adverse reactions.

Role of tumor microenvironment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the third leading cause of cancer death worldwide, with an incidence increasing every year. HCC pathogenesis is very complex. Its occurrence, development and metastasis are closely related to multiple mutations, cell signaling pathways and abnormal angiogenesis. The main reason for the high mortality rate of liver cancer is the difficulties in early diagnosis, and most patients have had local or distant metastasis when diagnosed. Moreover, there is a lack of effective treatment, because the pathogenesis of HCC is not yet fully clear. In recent years, a large number of studies have found that stromal tumor microenvironment plays an important role in the occurrence, development and metastasis of HCC. Tumor microenvironment and tumor cells create a complex system with interacting signaling pathways. In this review, we will discuss the role of tumor microenvironment in HCC in terms of HCC stromal cell microenvironment, inflammatory microenvironment and angiogenesis microenvironment.