Hepatocyte-Specific Deletion of HIF2α Prevents NASH-Related Liver Carcinogenesis by Decreasing Cancer Cell Proliferation

YAP/TAZ as master regulators in liver regeneration and disease: insights into mechanisms and therapeutic targets

Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are key downstream effectors of the Hippo pathway that regulate organ size, tissue homeostasis, and cancer development. YAP/TAZ play crucial regulatory roles in organ growth, cell proliferation, cell renewal, and regeneration. Mechanistically, YAP/TAZ influence the occurrence and progression of liver regeneration (LR) through various signaling pathways, including Notch, Wnt/β-catenin, TGF-β/Smad. While the activation of YAP/TAZ can promote the regeneration of damaged liver tissue, their mechanisms of action may differ under various LR conditions. Furthermore, excessive activation of YAP/TAZ may also lead to severe liver damage, manifesting as alcoholic hepatitis, liver fibrosis, and even liver cancer. Here, we review the role and mechanisms of YAP/TAZ in LR and liver disease, highlighting the potential for advancements in clinical diagnosis and treatment targeting YAP/TAZ in these contexts.

Hypoxia-Inducible Factor-2α Promotes Liver Fibrosis by Inducing Hepatocellular Death

The activation of hypoxia-inducible factors (HIF)-1α and 2α in the liver is closely linked to the progression of fatty liver diseases. Prior studies indicated that disrupting hepatocyte HIF-2α attenuates diet-induced hepatic steatosis, subsequently decreasing fibrosis. However, the direct role of hepatocyte HIF-2α in liver fibrosis has not been addressed. Hepatic HIF-2α expression was examined in mouse model of carbon tetrachloride (CCl4)-induced liver fibrosis. Conditional hepatocyte Hif-2α knockout mice were employed to investigate the role of hepatocyte HIF-2α in fibrosis. Markers of apoptosis, proliferation, inflammation, and fibrosis were assessed through biochemical, molecular, and histological analyses. We found an induction of HIF-2α in CCL4-injected liver injury and fibrosis mouse models. Hepatocyte-specific deletion of HIF-2α attenuated stellate cell activation and fibrosis, with no significant difference in inflammation. Disrupting hepatocyte HIF-2α led to reduced injury-mediated hepatocellular apoptosis. Surviving hepatocytes exhibited hypertrophy, which was strongly associated with the activation of c-JUN signaling. Our study demonstrates a direct role of hepatocyte HIF-2α in liver fibrosis by promoting hepatocyte apoptosis. The reduction in apoptosis and induction of hepatocyte hypertrophy following HIF-2α disruption is closely linked to enhanced c-JUN signaling, a survival mechanism in response to liver injury. These findings highlight HIF-2α as a potential therapeutic target for liver fibrosis.

Protease activated receptor 2 as a novel druggable target for the treatment of metabolic dysfunction-associated fatty liver disease and cancer

Metabolic dysfunction-associated fatty liver disease (MAFLD) is spreading worldwide, largely due to unhealthy lifestyles that contribute to the rise in diabetes, metabolic syndrome, and obesity. In this situation, the progression of injury to metabolic steatohepatitis can evolve to cirrhosis and, eventually, to hepatocellular carcinoma (HCC). It is well known that serine protease enzymes with different functions in cellular homeostasis act as signaling molecules that regulate liver inflammation by activating the protease-activated receptors (PARs) family members, expressed on the cellular plasma membrane. Among them, PAR2 plays a central role in the activation of signaling pathways in response to changes in the extracellular microenvironment. Experimental data have provided evidence that PAR2 is involved not only in inflammatory response but also in insulin resistance, lipid metabolism, and cancer. The major aims of this narrative review are addressed to assess PAR2 involvement in inflammation, metabolism, and liver disease progression and to explore possible therapeutic strategies, based on PAR2 inhibition, in order to prevent its biological effects in the context of MAFLD and cancer.

SerpinB3: A Multifaceted Player in Health and Disease-Review and Future Perspectives

SerpinB3, a member of the serine-protease inhibitor family, has emerged as a crucial player in various physiological and pathological processes. Initially identified as an oncogenic factor in squamous cell carcinomas, SerpinB3's intricate involvement extends from fibrosis progression and cancer to cell protection in acute oxidative stress conditions. This review explores the multifaceted roles of SerpinB3, focusing on its implications in fibrosis, metabolic syndrome, carcinogenesis and immune system impairment. Furthermore, its involvement in tissue protection from oxidative stress and wound healing underscores its potential as diagnostic and therapeutic tool. Recent studies have described the therapeutic potential of targeting SerpinB3 through its upstream regulators, offering novel strategies for cancer treatment development. Overall, this review underscores the importance of further research to fully elucidate the mechanisms of action of SerpinB3 and to exploit its therapeutic potential across various medical conditions.

The protease activated receptor 2 - CCAAT/enhancer-binding protein beta - SerpinB3 axis inhibition as a novel strategy for the treatment of non-alcoholic steatohepatitis

OBJECTIVE

The serine protease inhibitor SerpinB3 has been described as critical mediator of liver fibrosis and it has been recently proposed as an additional hepatokine involved in NASH development and insulin resistance. Protease Activated Receptor 2 has been identified as a novel regulator of hepatic metabolism. A targeted therapeutic strategy for NASH has been investigated, using 1-Piperidine Propionic Acid (1-PPA), since this compound has been recently proposed as both Protease Activated Receptor 2 and SerpinB3 inhibitor.

METHODS

The effect of SerpinB3 on inflammation and fibrosis genes was assessed in human macrophage and stellate cell lines. Transgenic mice, either overexpressing SerpinB3 or carrying Serpinb3 deletion and their relative wild type strains, were used in experimental NASH models. Subgroups of SerpinB3 transgenic mice and their controls were also injected with 1-PPA to assess the efficacy of this compound in NASH inhibition.

RESULTS

1-PPA did not present significant cell and organ toxicity and was able to inhibit SerpinB3 and PAR2 in a dose-dependent manner. This effect was associated to a parallel reduction of the synthesis of the molecules induced by endogenous SerpinB3 or by its paracrine effects both in vitro and in vivo, leading to inhibition of lipid accumulation, inflammation and fibrosis in experimental NASH. At mechanistic level, the antiprotease activity of SerpinB3 was found essential for PAR2 activation, determining upregulation of the CCAAT Enhancer Binding Protein beta (C/EBP-β), another pivotal regulator of metabolism, inflammation and fibrosis, which in turn determined SerpinB3 synthesis.

CONCLUSIONS

1-PPA treatment was able to inhibit the PAR2 - C/EBP-β - SerpinB3 axis and to protect from NASH development and progression, supporting the potential use of a similar approach for a targeted therapy of NASH.

Hypoxia-inducible factor-2α promotes fibrosis in non-alcoholic fatty liver disease by enhancing glutamine catabolism and inhibiting yes-associated protein phosphorylation in hepatic stellate cells

Non-alcoholic fatty liver disease (NAFLD) has a high global prevalence and affects approximately one-third of adults, owing to high-fat dietary habits and a sedentary lifestyle. The role of hypoxia-inducible factor 2α (HIF-2α) in NAFLD progression remains unknown. This study aimed to investigate the effects of chronic hypoxia on NAFLD progression by examining the role of hypoxia-inducible factor 2α (HIF-2α) activation and that of hepatic stellate cell (HSC)-derived myofibroblasts through glutaminolysis. We hypothesised that hypoxia exacerbates NAFLD by promoting HIF-2α upregulation and inhibiting phosphorylated yes-associated protein (YAP), and that increasing YAP expression enhances HSC-derived myofibroblasts. We studied patients with NAFLD living at high altitudes, as well as animal models and cultured cells. The results revealed significant increases in HSC-derived myofibroblasts and collagen accumulation caused by HIF-2α and YAP upregulation, both in patients and in a mouse model for hypoxia and NAFLD. HIF-2α and HIF-2α-dependent YAP downregulation reduced HSC activation and myofibroblast levels in persistent chronic hypoxia. Furthermore, hypoxia-induced HIF-2α upregulation promoted YAP and inhibited YAP phosphorylation, leading to glutaminase 1 (GLS1), SLC38A1, α-SMA, and Collagen-1 overexpression. Additionally, hypoxia restored mitochondrial adenosine triphosphate production and reactive oxygen species (ROS) overproduction. Thus, chronic hypoxia-induced HIF-2α activation enhances fibrosis and NAFLD progression by restoring mitochondrial ROS production and glutaminase-1-induced glutaminolysis, which is mediated through the inhibition of YAP phosphorylation and increased YAP nuclear translocation. In summary, HIF-2α plays a pivotal role in NAFLD progression during chronic hypoxia.

Histidine-rich glycoprotein in metabolic dysfunction-associated steatohepatitis-related disease progression and liver carcinogenesis

Background

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously non-alcoholic fatty liver disease (NAFLD), is a leading cause of chronic liver disease worldwide. In 20%-30% of MASLD patients, the disease progresses to metabolic dysfunction-associated steatohepatitis (MASH, previously NASH) which can lead to fibrosis/cirrhosis, liver failure as well as hepatocellular carcinoma (HCC). Here we investigated the role of histidine-rich glycoprotein (HRG), a plasma protein produced by hepatocytes, in MASLD/MASH progression and HCC development.

Methods

The role of HRG was investigated by morphological, cellular, and molecular biology approaches in (a) HRG knock-out mice (HRG-/- mice) fed on a CDAA dietary protocol or a MASH related diethyl-nitrosamine/CDAA protocol of hepatocarcinogenesis, (b) THP1 monocytic cells treated with purified HRG, and (c) well-characterized cohorts of MASLD patients with or without HCC.

Results

In non-neoplastic settings, murine and clinical data indicate that HRG increases significantly in parallel with disease progression. In particular, in MASLD/MASH patients, higher levels of HRG plasma levels were detected in subjects with extensive fibrosis/cirrhosis. When submitted to the pro-carcinogenic protocol, HRG-/- mice showed a significant decrease in the volume and number of HCC nodules in relation to decreased infiltration of macrophages producing pro-inflammatory mediators, including IL-1β, IL-6, IL-12, IL-10, and VEGF as well as impaired angiogenesis. The histopathological analysis (H-score) of MASH-related HCC indicate that the higher HRG positivity in peritumoral tissue significantly correlates with a lower overall patient survival and an increased recurrence. Moreover, a significant increase in HRG plasma levels was detected in cirrhotic (F4) patients and in patients carrying HCC vs. F0/F1 patients.

Conclusion

Murine and clinical data indicate that HRG plays a significant role in MASLD/MASH progression to HCC by supporting a specific population of tumor-associated macrophages with pro-inflammatory response and pro-angiogenetic capabilities which critically support cancer cell survival. Furthermore, our data suggest HRG as a possible prognostic predictor in HCC patients with MASLD/MASH-related HCCs.

Hypoxia-Induced Signaling in Gut and Liver Pathobiology

Oxygen (O2) is essential for cellular metabolism and biochemical reactions. When the demand for O2 exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are essential to activate adaptive and survival responses following hypoxic stress. In the gut (intestines) and liver, the presence of oxygen gradients or physiologic hypoxia is necessary to maintain normal homeostasis. While physiologic hypoxia is beneficial and aids in normal functions, pathological hypoxia is harmful as it exacerbates inflammatory responses and tissue dysfunction and is a hallmark of many cancers. In this review, we discuss the role of gut and liver hypoxia-induced signaling, primarily focusing on HIFs, in the physiology and pathobiology of gut and liver diseases. Additionally, we examine the function of HIFs in various cell types during gut and liver diseases, beyond intestinal epithelial and hepatocyte HIFs. This review highlights the importance of understanding hypoxia-induced signaling in the pathogenesis of gut and liver diseases and emphasizes the potential of HIFs as therapeutic targets.

HIF2α, Hepcidin and their crosstalk as tumour-promoting signalling

Not all aspects of the disruption of iron homeostasis in cancer have been fully elucidated. Iron accumulation in cancer cells is frequent for many solid tumours, and this is often accompanied by the contemporary rise of two key iron regulators, HIF2α and Hepcidin. This scenario is different from what happens under physiological conditions, where Hepcidin parallels systemic iron concentrations while HIF2α levels are inversely associated to Hepcidin. The present review highlights the increasing body of evidence for the pro-tumoral effect of HIF2α and Hepcidin, discusses the possible imbalance in HIF2α, Hepcidin and iron homeostasis during cancer, and explores therapeutic options relying on these pathways as anticancer strategies.

Novel Molecular Targets for Immune Surveillance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common and aggressive cancer with a high mortality rate. The incidence of HCC is increasing worldwide, and the lack of effective screening programs often results in delayed diagnosis, making it a challenging disease to manage. Immunotherapy has emerged as a promising treatment option for different kinds of cancers, with the potential to stimulate the immune system to target cancer cells. However, the current immunotherapeutic approaches for HCC have shown limited efficacy. Since HCC arises within a complex tumour microenvironment (TME) characterized by the presence of various immune and stromal cell types, the understanding of this interaction is crucial for the identification of effective therapy. In this review, we highlight recent advances in our understanding of the TME of HCC and the immune cells involved in anti-tumour responses, including the identification of new possible targets for immunotherapy. We illustrate a possible classification of HCC based on the tumour immune infiltration and give evidence about the role of SerpinB3, a serine protease inhibitor involved in the regulation of the immune response in different cancers.

SerpinB3 Upregulates Low-Density Lipoprotein Receptor-Related Protein (LRP) Family Members, Leading to Wnt Signaling Activation and Increased Cell Survival and Invasiveness

Abnormal activation of the Wnt-β-catenin signaling cascade is involved in tumor growth and dissemination. SerpinB3 has been shown to induce β-catenin, and both molecules are overexpressed in tumors, particularly in those with poor prognoses. The aim of this study was to evaluate the ability of SerpinB3 to modulate the Wnt pathway in liver cancer and in monocytic cells, the main type of inflammatory cells in the tumor microenvironment. The Wnt cascade, Wnt co-receptors, and low-density lipoprotein receptor-related protein (LRP) members were analyzed in different cell lines and human monocytes in the presence or absence of SerpinB3. The Wnt-β-catenin axis was also evaluated in liver tumors induced in mice with different extents of SeprinB3 expression. In monocytic cells, SerpinB3 induced a significant upregulation of Wnt-1/7, nuclear β-catenin, and c-Myc, which are associated with increased cell lifespan and proliferation. In liver tumors in mice, the expression of β-catenin was significantly correlated with the presence of SerpinB3. In hepatoma cells, Wnt co-receptors LRP-5/6 and LRP-1, implicated in cell survival and invasiveness, were upregulated by SerpinB3. The LRP pan-inhibitor RAP not only induced a decrease in LRP expression, but also a dose-dependent reduction in SerpinB3-induced invasiveness. In conclusion, SerpinB3 determines the activation of the Wnt canonical pathway and cell invasiveness through the upregulation of LRP family members.

Inflammatory processes involved in NASH-related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. In the recent years nonalcoholic fatty liver disease (NAFLD) is becoming a growing cause of HCCs and the incidence of NAFLD-related HCCs is expected to further dramatically increase by the next decade. Chronic inflammation is regarded as the driving force of NAFLD progression and a key factor in hepatic carcinogenesis. Hepatic inflammation in NAFLD results from the persistent stimulation of innate immunity in response to hepatocellular injury and gut dysbiosis as well as by the activation of adaptive immunity. However, the relative roles of innate and adaptive immunity in the processes leading to HCC are still incompletely characterized. This is due to the complex interplay between different liver cell populations, which is also strongly influenced by gut-derived bacterial products, metabolic/nutritional signals. Furthermore, carcinogenic mechanisms in NAFLD/NASH appear to involve the activation of signals mediated by hypoxia inducible factors. This review discusses recent data regarding the contribution of different inflammatory cells to NAFLD-related HCC and their possible impact on patient response to current treatments.

Advances in prognostic and therapeutic targets for hepatocellular carcinoma and intrahepatic cholangiocarcinoma: The hippo signaling pathway

Primary liver cancer is the sixth most frequently diagnosed cancer worldwide and the third leading cause of cancer-related death. The majority of the primary liver cancer cases are hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Worldwide, there is an increasing incidence of primary liver cancer cases due to multiple risk factors ranging from parasites and viruses to metabolic diseases and lifestyles. Often, patients are diagnosed at advanced stages, depriving them of surgical curability benefits. Moreover, the efficacy of the available chemotherapeutics is limited in advanced stages. Furthermore, tumor metastases and recurrence make primary liver cancer management exceptionally challenging. Thus, exploring the molecular mechanisms for the development and progression of primary liver cancer is critical in improving diagnostic, treatment, prognostication, and surveillance modalities. These mechanisms facilitate the discovery of specific targets that are critical for novel and more efficient treatments. Consequently, the Hippo signaling pathway executing a pivotal role in organogenesis, hemostasis, and regeneration of tissues, regulates liver cells proliferation, and apoptosis. Cell polarity or adhesion molecules and cellular metabolic status are some of the biological activators of the pathway. Thus, understanding the mechanisms exhibited by the Hippo pathway is critical to the development of novel targeted therapies. This study reviews the advances in identifying therapeutic targets and prognostic markers of the Hippo pathway for primary liver cancer in the past six years.

SerpinB3 as a Pro-Inflammatory Mediator in the Progression of Experimental Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is becoming the most common chronic liver disease worldwide. In 20-30% of patients, NAFLD can progress into non-alcoholic steatohepatitis (NASH), eventually leading to fibrosis, cirrhosis and hepatocellular carcinoma development. SerpinB3 (SB3), a hypoxia-inducible factor-2α dependent cysteine protease inhibitor, is up-regulated in hepatocytes during progressive NAFLD and proposed to contribute to disease progression. In this study we investigated the pro-inflammatory role of SB3 by employing phorbol-myristate acetate-differentiated human THP-1 macrophages exposed in vitro to human recombinant SB3 (hrSB3) along with mice overexpressing SB3 in hepatocytes (TG/SB3) or knockout for SB3 (KO/SB3) in which NASH was induced by feeding methionine/choline deficient (MCD) or a choline-deficient, L-amino acid defined (CDAA) diets. In vivo experiments showed that the induction of NASH in TG/SB3 mice was characterized by an impressive increase of liver infiltrating macrophages that formed crown-like aggregates and by an up-regulation of hepatic transcript levels of pro-inflammatory cytokines. All these parameters and the extent of liver damage were significantly blunted in KO/SB3 mice. In vitro experiments confirmed that hrSB3 stimulated macrophage production of M1-cytokines such as TNFα and IL-1β and reactive oxygen species along with that of TGFβ and VEGF through the activation of the NF-kB transcription factor. The opposite changes in liver macrophage activation observed in TG/SB3 or KO/SB3 mice with NASH were associated with a parallel modulation in the expression of triggering receptor expressed on myeloid cells-2 (TREM2), CD9 and galectin-3 markers, recently detected in NASH-associated macrophages. From these results we propose that SB3, produced by activated/injured hepatocytes, may operate as a pro-inflammatory mediator in NASH contributing to the disease progression.

Hypoxia-driven metabolic heterogeneity and immune evasive behaviour of gastrointestinal cancers: Elements of a recipe for disaster

Gastrointestinal (GI) cancers refer to a group of malignancies associated with the GI tract (GIT). Like other solid tumors, hypoxic regions consistently feature inside the GI tumor microenvironment (TME) and contribute towards metabolic reprogramming of tumor-resident cells by modulating hypoxia-induced factors. We highlight here how the metabolic crosstalk between cancer cells and immune cells generate immunosuppressive environment inside hypoxic tumors. Given the fluctuating nature of tumor hypoxia, the metabolic fluxes between immune cells and cancer cells change dynamically. These changes alter cellular phenotypes and functions, resulting in the acceleration of cancer progression. These evolved properties of hypoxic tumors make metabolism-targeting monotherapy approaches or immunotherapy-measures unsuccessful. The current review highlights the advantages of combined immunometabolic treatment strategies to target hypoxic GI cancers and also identifies research areas to develop better combinational therapeutics for future.