Inhibiting Glutamine-Dependent mTORC1 Activation Ameliorates Liver Cancers Driven by β-Catenin Mutations

Long non-coding RNA PXN-AS1 promotes glutamine synthetase-mediated chronic myeloid leukemia BCR::ABL1-independent resistance to Imatinib via cell cycle signaling pathway

BACKGROUND

Chronic myeloid leukemia (CML) is a common hematological malignancy, and tyrosine kinase inhibitors (TKIs) represent the primary therapeutic approach for CML. Activation of metabolism signaling pathway has been connected with BCR::ABL1-independent TKIs resistance in CML cells. However, the specific mechanism by which metabolism signaling mediates this drug resistance remains unclear. Here, we identified one relationship between glutamine synthetase (GS) and BCR::ABL1-independent Imatinib resistance in CML cells.

METHODS

GS and PXN-AS1 in bone marrow samples of CML patients with Imatinib resistance (IR) were screened and detected by whole transcriptome sequencing. GS expression was upregulated using LVs and blocked using shRNAs respectively, then GS expression, Gln content, and cell cycle progression were respectively tested. The CML IR mice model were established by tail vein injection, prognosis of CML IR mice model were evaluated by Kaplan-Meier analysis, the ratio of spleen/body weight, HE staining, and IHC. PXN-AS1 level was blocked using shRNAs, and the effects of PXN-AS1 on CML IR cells in vitro and in vivo were tested the same as GS. Several RNA-RNA tools were used to predict the potential target microRNAs binding to both GS and PXN-AS1. RNA mimics and RNA inhibitors were used to explore the mechanism through which PXN-AS1 regulates miR-635 or miR-635 regulates GS.

RESULTS

GS was highly expressed in the bone marrow samples of CML patients with Imatinib resistance. In addition, the lncRNA PXN-AS1 was found to mediate GS expression and disorder cell cycle in CML IR cells via mTOR signaling pathway. PXN-AS1 regulated GS expression by binding to miR-635. Additionally, knockdown of PXN-AS1 attenuated BCR::ABL1-independent Imatinib resistance in CML cells via PXN-AS1/miR-635/GS/Gln/mTOR signaling pathway.

CONCLUSIONS

Thus, PXN-AS1 promotes GS-mediated BCR::ABL1-independent Imatinib resistance in CML cells via cell cycle signaling pathway.

Quantitative radiomics and qualitative LI-RADS imaging descriptors for non-invasive assessment of β-catenin mutation status in hepatocellular carcinoma

PURPOSE

Gain-of-function mutations in CTNNB1, gene encoding for β-catenin, are observed in 25-30% of hepatocellular carcinomas (HCCs). Recent studies have shown β-catenin activation to have distinct roles in HCC susceptibility to mTOR inhibitors and resistance to immunotherapy. Our goal was to develop and test a computational imaging-based model to non-invasively assess β-catenin activation in HCC, since liver biopsies are often not done due to risk of complications.

METHODS

This IRB-approved retrospective study included 134 subjects with pathologically proven HCC and available β-catenin activation status, who also had either CT or MR imaging of the liver performed within 1 year of histological assessment. For qualitative descriptors, experienced radiologists assessed the presence of imaging features listed in LI-RADS v2018. For quantitative analysis, a single biopsy proven tumor underwent a 3D segmentation and radiomics features were extracted. We developed prediction models to assess the β-catenin activation in HCC using both qualitative and quantitative descriptors.

RESULTS

There were 41 cases (31%) with β-catenin mutation and 93 cases (69%) without. The model's AUC was 0.70 (95% CI 0.60, 0.79) using radiomics features and 0.64 (0.52, 0.74; p = 0.468) using qualitative descriptors. However, when combined, the AUC increased to 0.88 (0.80, 0.92; p = 0.009). Among the LI-RADS descriptors, the presence of a nodule-in-nodule showed a significant association with β-catenin mutations (p = 0.015). Additionally, 88 radiomics features exhibited a significant association (p < 0.05) with β-catenin mutations.

CONCLUSION

Combination of LI-RADS descriptors and CT/MRI-derived radiomics determine β-catenin activation status in HCC with high confidence, making precision medicine a possibility.

β-Catenin Activation Reprograms Ammonia Metabolism to Promote Senescence Resistance in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a typical tumor that undergoes metabolic reprogramming, differing from normal liver tissue in glucose, lipid, nucleic acid, and amino acid metabolism. Although ammonia is a toxic metabolic by-product, it has also been recently recognized as a signaling molecule to activate lipid metabolism, and it can be a nitrogen source for biosynthesis to support tumorigenesis. In this study, we revealed that β-catenin activation increases ammonia production in HCC mainly by stimulating glutaminolysis. β-Catenin/LEF1 activated the transcription of the glutamate dehydrogenase GLUD1, which then promoted ammonia utilization to enhance the production of glutamate, aspartate, and proline as evidenced by 15NH4Cl metabolic flux. β-Catenin/TCF4 induced the transcription of SLC4A11, an ammonia transporter, to excrete excess ammonia. SLC4A11 was upregulated in HCC tumor tissues, and high SLC4A11 expression was associated with poor prognosis and advanced disease stages. Loss of SLC4A11 induced HCC cell senescence in vitro by blocking ammonia excretion and reduced β-catenin-driven tumor growth in vivo. Furthermore, elevated levels of plasma ammonia promoted the progression of β-catenin mutant HCC, which was impeded by SLC4A11 deficiency. Downregulation of SLC4A11 led to ammonia accumulation in tumor interstitial fluid and decreased plasma ammonia levels in HCC with activated β-catenin. Altogether, this study indicates that β-catenin activation reprograms ammonia metabolism and that blocking ammonia excretion by targeting SLC4A11 could be a promising approach to induce senescence in β-catenin mutant HCC.

SIGNIFICANCE

Ammonia metabolism reprogramming mediated by aberrant activation of β-catenin induces resistance to senescence in HCC and can be targeted by inhibiting SLC4A11 as a potential therapy for β-catenin mutant liver cancer.

Analysis of Tumor-Associated AXIN1 Missense Mutations Identifies Variants That Activate β-Catenin Signaling

AXIN1 is a major component of the β-catenin destruction complex and is frequently mutated in various cancer types, particularly liver cancers. Truncating AXIN1 mutations are recognized to encode a defective protein that leads to β-catenin stabilization, but the functional consequences of missense mutations are not well characterized. Here, we first identified the GSK3β, β-catenin, and RGS/APC interaction domains of AXIN1 that are the most critical for proper β-catenin regulation. Analysis of 80 tumor-associated variants in these domains identified 18 that significantly affected β-catenin signaling. Coimmunoprecipitation experiments revealed that most of them lost binding to the binding partner corresponding to the mutated domain. A comprehensive protein structure analysis predicted the consequences of these mutations, which largely overlapped with the observed effects on β-catenin signaling in functional experiments. The structure analysis also predicted that loss-of-function mutations within the RGS/APC interaction domain either directly affected the interface for APC binding or were located within the hydrophobic core and destabilized the entire structure. In addition, truncated AXIN1 length inversely correlated with the β-catenin regulatory function, with longer proteins retaining more functionality. These analyses suggest that all AXIN1-truncating mutations at least partially affect β-catenin regulation, whereas this is only the case for a subset of missense mutations. Consistently, most colorectal and liver cancers carrying missense variants acquire mutations in other β-catenin regulatory genes such as APC and CTNNB1. These results will aid the functional annotation of AXIN1 mutations identified in large-scale sequencing efforts or in individual patients.

SIGNIFICANCE

Characterization of 80 tumor-associated missense variants of AXIN1 reveals a subset of 18 mutations that disrupt its β-catenin regulatory function, whereas the majority are passenger mutations.

Glutamine metabolism, a double agent combating or fuelling hepatocellular carcinoma

The reprogramming of glutamine metabolism is a key event in cancer more generally and in hepatocellular carcinoma (HCC) in particular. Glutamine consumption supplies tumours with ATP and metabolites through anaplerosis of the tricarboxylic acid cycle, while glutamine production can be enhanced by the overexpression of glutamine synthetase. In HCC, increased glutamine production is driven by activating mutations in the CTNNB1 gene encoding β-catenin. Increased glutamine synthesis or utilisation impacts tumour epigenetics, oxidative stress, autophagy, immunity and associated pathways, such as the mTOR (mammalian target of rapamycin) pathway. In this review, we will discuss studies which emphasise the pro-tumoral or tumour-suppressive effect of glutamine overproduction. It is clear that more comprehensive studies are needed as a foundation from which to develop suitable therapies targeting glutamine metabolic pathways, depending on the predicted pro- or anti-tumour role of dysregulated glutamine metabolism in distinct genetic contexts.

Wnt/β-catenin signaling pathway in liver biology and tumorigenesis

The Wnt/β-catenin pathway is an evolutionarily conserved signaling pathway that controls fundamental physiological and pathological processes by regulating cell proliferation and differentiation. The Wnt/β-catenin pathway enables liver homeostasis by inducing differentiation and contributes to liver-specific features such as metabolic zonation and regeneration. In contrast, abnormalities in the Wnt/β-catenin pathway promote the development and progression of hepatocellular carcinoma (HCC). Similarly, hepatoblastoma, the most common childhood liver cancer, is frequently associated with β-catenin mutations, which activate Wnt/β-catenin signaling. HCCs with activation of the Wnt/β-catenin pathway have unique gene expression patterns and pathological and clinical features. Accordingly, they are highly differentiated with retaining hepatocyte-like characteristics and tumorigenic. Activation of the Wnt/β-catenin pathway in HCC also alters the state of immune cells, causing "immune evasion" with inducing resistance to immune checkpoint inhibitors, which have recently become widely used to treat HCC. Activated Wnt/β-catenin signaling exhibits these phenomena in liver tumorigenesis through the expression of downstream target genes, and the molecular basis is still poorly understood. In this review, we describe the physiological roles of Wnt/b-catenin signaling and then discuss their characteristic changes by the abnormal activation of Wnt/b-catenin signaling. Clarification of the mechanism would contribute to the development of therapeutic agents in the future.

Apigenin Suppresses MED28-Mediated Cell Growth in Human Liver Cancer Cells

Flavonoids exhibit health-promoting benefits against multiple chronic diseases, including cancer. Apigenin (4',5,7-trihydroxyflavone), one flavonoid present in fruits and vegetables, is potentially applicable to chemoprevention. Despite considerable progress in the therapeutic regimen of liver cancer, its prognosis remains poor. MED28, a Mediator subunit for transcriptional activation, is implicated in the development of several types of malignancy; however, its role in liver cancer is unknown at present. In liver cancer, the AKT/mammalian target of rapamycin (mTOR) is one major pathway involved in the oncogenic process. The aim of this study is to investigate the role of apigenin and MED28 in AKT/mTOR signaling in liver cancer. We first identified a connectivity score of 92.77 between apigenin treatment and MED28 knockdown in several cancer cell lines using CLUE, a cloud-based software platform to assess connectivity among compounds and genetic perturbagens. Higher expression of MED28 predicted a poorer survival prognosis; MED28 expression in liver cancer tissue was significantly higher than that of normal tissue, and it was positively correlated with tumor stage and grade in The Cancer Genome Atlas Liver Cancer (TCGA-LIHC) data set. Knockdown of MED28 induced cell cycle arrest and suppressed the AKT/mTOR signaling in two human liver cancer cell lines, HepG2 and Huh 7, accompanied by less lipid accumulation and lower expression and nuclear localization of sterol regulatory element binding protein 1 (SREBP1). Apigenin inhibited the expression of MED28, and the effect of apigenin mimicked that of the MED28 knockdown. On the other hand, the AKT/mTOR signaling was upregulated when MED28 was overexpressed. These data indicated that MED28 was associated with the survival prognosis and the progression of liver cancer by regulating AKT/mTOR signaling and apigenin appeared to inhibit cell growth through MED28-mediated mTOR signaling, which may be applicable as an adjuvant of chemotherapy or chemoprevention in liver cancer.

WNT/β-catenin signaling in hepatocellular carcinoma: The aberrant activation, pathogenic roles, and therapeutic opportunities

Hepatocellular carcinoma (HCC) is a liver cancer, highly heterogeneous both at the histopathological and molecular levels. It arises from hepatocytes as the result of the accumulation of numerous genomic alterations in various signaling pathways, including canonical WNT/β-catenin, AKT/mTOR, MAPK pathways as well as signaling associated with telomere maintenance, p53/cell cycle regulation, epigenetic modifiers, and oxidative stress. The role of WNT/β-catenin signaling in liver homeostasis and regeneration is well established, whereas in development and progression of HCC is extensively studied. Herein, we review recent advances in our understanding of how WNT/β-catenin signaling facilitates the HCC development, acquisition of stemness features, metastasis, and resistance to treatment. We outline genetic and epigenetic alterations that lead to activated WNT/β-catenin signaling in HCC. We discuss the pivotal roles of CTNNB1 mutations, aberrantly expressed non-coding RNAs and complexity of crosstalk between WNT/β-catenin signaling and other signaling pathways as challenging or advantageous aspects of therapy development and molecular stratification of HCC patients for treatment.

shinyDeepDR: A user-friendly R Shiny app for predicting anti-cancer drug response using deep learning

Advancing precision oncology requires accurate prediction of treatment response and accessible prediction models. To this end, we present shinyDeepDR, a user-friendly implementation of our innovative deep learning model, DeepDR, for predicting anti-cancer drug sensitivity. The web tool makes DeepDR more accessible to researchers without extensive programming experience. Using shinyDeepDR, users can upload mutation and/or gene expression data from a cancer sample (cell line or tumor) and perform two main functions: "Find Drug," which predicts the sample's response to 265 approved and investigational anti-cancer compounds, and "Find Sample," which searches for cell lines in the Cancer Cell Line Encyclopedia (CCLE) and tumors in The Cancer Genome Atlas (TCGA) with genomics profiles similar to those of the query sample to study potential effective treatments. shinyDeepDR provides an interactive interface to interpret prediction results and to investigate individual compounds. In conclusion, shinyDeepDR is an intuitive and free-to-use web tool for in silico anti-cancer drug screening.

GLUL stabilizes N-Cadherin by antagonizing β-Catenin to inhibit the progresses of gastric cancer

Glutamate-ammonia ligase (GLUL, also known as glutamine synthetase) is a crucial enzyme that catalyzes ammonium and glutamate into glutamine in the ATP-dependent condensation. Although GLUL plays a critical role in multiple cancers, the expression and function of GLUL in gastric cancer remain unclear. In the present study, we have found that the expression level of GLUL was significantly lower in gastric cancer tissues compared with adjacent normal tissues, and correlated with N stage and TNM stage, and low GLUL expression predicted poor survival for gastric cancer patients. Knockdown of GLUL promoted the growth, migration, invasion and metastasis of gastric cancer cells in vitro and in vivo, and vice versa, which was independent of its enzyme activity. Mechanistically, GLUL competed with β-Catenin to bind to N-Cadherin, increased the stability of N-Cadherin and decreased the stability of β-Catenin by alerting their ubiquitination. Furthermore, there were lower N-Cadherin and higher β-Catenin expression levels in gastric cancer tissues compared with adjacent normal tissues. GLUL protein expression was correlated with that of N-Cadherin, and could be the independent prognostic factor in gastric cancer. Our findings reveal that GLUL stabilizes N-Cadherin by antagonizing β-Catenin to inhibit the progress of gastric cancer.

Metabolic reprogramming in the tumor microenvironment of liver cancer

The liver is essential for metabolic homeostasis. The onset of liver cancer is often accompanied by dysregulated liver function, leading to metabolic rearrangements. Overwhelming evidence has illustrated that dysregulated cellular metabolism can, in turn, promote anabolic growth and tumor propagation in a hostile microenvironment. In addition to supporting continuous tumor growth and survival, disrupted metabolic process also creates obstacles for the anticancer immune response and restrains durable clinical remission following immunotherapy. In this review, we elucidate the metabolic communication between liver cancer cells and their surrounding immune cells and discuss how metabolic reprogramming of liver cancer impacts the immune microenvironment and the efficacy of anticancer immunotherapy. We also describe the crucial role of the gut-liver axis in remodeling the metabolic crosstalk of immune surveillance and escape, highlighting novel therapeutic opportunities.

Endoplasmic Reticulum Stress and Metabolism in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, accounting for 85% to 90% of all liver cancer cases. It is a hepatocyte-derived primary tumor, causing 550,000 deaths per year, ranking it as one of the most common cancers worldwide. The liver is a highly metabolic organ with multiple functions, including digestion, detoxification, breakdown of fats, and production of bile and cholesterol, in addition to storage of vitamins, glycogen, and minerals, and synthesizing plasma proteins and clotting factors. Due to these fundamental and diverse functions, the malignant transformation of hepatic cells can have a severe impact on the liver's metabolism. Furthermore, tumorigenesis is often accompanied by activation of the endoplasmic reticulum (ER) stress pathways, which are known to be highly intertwined with several metabolic pathways. Because HCC is characterized by changes in the metabolome and by an aberrant activation of the ER stress pathways, the aim of this review was to summarize the current knowledge that links ER stress and metabolism in HCC, thereby focusing on potential therapeutic targets.

β-catenin/CBP activation of mTORC1 signaling promotes partial epithelial-mesenchymal states in head and neck cancer

Head and neck cancers, which include oral squamous cell carcinoma (OSCC) as a major subsite, exhibit cellular plasticity that includes features of an epithelial-mesenchymal transition (EMT), referred to as partial-EMT (p-EMT). To identify molecular mechanisms contributing to OSCC plasticity, we performed a multiphase analysis of single cell RNA sequencing (scRNAseq) data from human OSCC. This included a multiresolution characterization of cancer cell subgroups to identify pathways and cell states that are heterogeneously represented, followed by casual inference analysis to elucidate activating and inhibitory relationships between these pathways and cell states. This approach revealed signaling networks associated with hierarchical cell state transitions, which notably included an association between β-catenin-driven CREB-binding protein (CBP) activity and mTORC1 signaling. This network was associated with subpopulations of cancer cells that were enriched for markers of the p-EMT state and poor patient survival. Functional analyses revealed that β-catenin/CBP induced mTORC1 activity in part through the transcriptional regulation of a raptor-interacting protein, chaperonin containing TCP1 subunit 5 (CCT5). Inhibition of β-catenin-CBP activity through the use of the orally active small molecule, E7386, reduced the expression of CCT5 and mTORC1 activity in vitro, and inhibited p-EMT-associated markers and tumor development in a murine model of OSCC. Our study highlights the use of multiresolution network analyses of scRNAseq data to identify targetable signals for therapeutic benefit, thus defining an underappreciated association between β-catenin/CBP and mTORC1 signaling in head and neck cancer plasticity.

Hepatocellular carcinomas, exhibiting intratumor fibrosis, express cancer-specific extracellular matrix remodeling and WNT/TGFB signatures, associated with poor outcome

BACKGROUND AND AIMS

HCC, the third leading cause of cancer-related death, arises in the context of liver fibrosis. Although HCC is generally poorly fibrogenic, some tumors harbor focal intratumor extracellular matrix (ECM) deposits called "fibrous nests." To date, the molecular composition and clinical relevance of these ECM deposits have not been fully defined.

APPROACH AND RESULTS

We performed quantitative matrisome analysis by tandem mass tags mass spectrometry in 20 human cancer specific matrisome (HCCs) with high or low-grade intratumor fibrosis and matched nontumor tissues, as well as in 12 livers from mice treated with vehicle, carbon tetrachloride, or diethylnitrosamine. We found 94 ECM proteins differentially abundant between high and low-grade fibrous nests, including interstitial and basement membrane components, such as several collagens, glycoproteins, proteoglycans, enzymes involved in ECM stabilization and degradation, and growth factors. Pathway analysis revealed a metabolic switch in high-grade fibrosis, with enhanced glycolysis and decreased oxidative phosphorylation. Integrating the quantitative proteomics with transcriptomics from HCCs and nontumor livers (n = 2,285 samples), we identified a subgroup of fibrous nest HCCs, characterized by cancer-specific ECM remodeling, expression of the WNT/TGFB (S1) subclass signature, and poor patient outcome. Fibrous nest HCCs abundantly expressed an 11-fibrous-nest - protein signature, associated with poor patient outcome, by multivariate Cox analysis, and validated by multiplex immunohistochemistry.

CONCLUSIONS

Matrisome analysis highlighted cancer-specific ECM deposits, typical of the WNT/TGFB HCC subclass, associated with poor patient outcomes. Hence, histologic reporting of intratumor fibrosis in HCC is of clinical relevance.

Glutamine metabolic reprogramming in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a lethal disease with limited management strategies and poor prognosis. Metabolism alternations have been frequently unveiled in HCC, including glutamine metabolic reprogramming. The components of glutamine metabolism, such as glutamine synthetase, glutamate dehydrogenase, glutaminase, metabolites, and metabolite transporters, are validated to be potential biomarkers of HCC. Increased glutamine consumption is confirmed in HCC, which fuels proliferation by elevated glutamate dehydrogenase or upstream signals. Glutamine metabolism also serves as a nitrogen source for amino acid or nucleotide anabolism. In addition, more glutamine converts to glutathione as an antioxidant in HCC to protect HCC cells from oxidative stress. Moreover, glutamine metabolic reprogramming activates the mTORC signaling pathway to support tumor cell proliferation. Glutamine metabolism targeting therapy includes glutamine deprivation, related enzyme inhibitors, and transporters inhibitors. Together, glutamine metabolic reprogramming plays a pivotal role in HCC identification, proliferation, and progression.

Wnt Signaling Stimulates Cooperation between GREB1 and HNF4α to Promote Proliferation in Hepatocellular Carcinoma

Wnt signaling is known to maintain two cell states, hepatocyte differentiation and proliferation, in hepatocellular carcinoma (HCC). On the other hand, activation of Wnt signaling in colon cancer promotes uncontrollable stereotypic proliferation, whereas cells remain undifferentiated. To elucidate the unique mode of Wnt signaling in HCC, we comprehensively investigated HCC-specific Wnt pathway target genes and identified GREB1. Wnt signaling induced expression of GREB1 coupled with HNF4α and FOXA2, master transcription factors that maintain hepatic differentiation. Moreover, GREB1 was enriched at the regulatory region of atypical HNF4α target genes, including progrowth genes, thereby stimulating HCC proliferation. Therefore, GREB1 acts as a unique mediator of versatile Wnt signaling in HCC progression, bridging the roles of the Wnt pathway in differentiation and proliferation.

SIGNIFICANCE

GREB1 is a liver cancer-specific Wnt signaling target gene that induces an oncogenic shift of HNF4α, a putative tumor suppressor, and may represent a therapeutic target in Wnt-activated hepatocellular carcinoma.

Acyl-CoA thioesterase 12 suppresses YAP-mediated hepatocarcinogenesis by limiting glycerolipid biosynthesis

Cancer cells use acetate to support the higher demand for energy and lipid biosynthesis during uncontrolled cell proliferation, as well as for acetylation of regulatory proteins. Acyl-CoA thioesterase 12 (Acot12) is the enzyme that hydrolyzes acetyl-CoA to acetate in liver cytosol and is downregulated in hepatocellular carcinoma (HCC). A mechanistic role for Acot12 in hepatocarcinogenesis was assessed in mice in response to treatment with diethylnitrosamine(DEN)/carbon tetrachloride (CCl4) administration or prolonged feeding of a diet that promotes non-alcoholic steatohepatitis (NASH). Relative to controls, Acot12-/- mice exhibited accelerated liver tumor formation that was characterized by the hepatic accumulation of glycerolipids, including lysophosphatidic acid (LPA), and that was associated with reduced Hippo signaling and increased yes-associated protein (YAP)-mediated transcriptional activity. In Acot12-/- mice, restoration of hepatic Acot12 expression inhibited hepatocarcinogenesis and YAP activation, as did knockdown of hepatic YAP expression. Excess LPA produced due to deletion of Acot12 signaled through LPA receptors (LPARs) coupled to Gα12/13 subunits to suppress YAP phosphorylation, thereby promoting its nuclear localization and transcriptional activity. These findings identify a protective role for Acot12 in suppressing hepatocarcinogenesis by limiting biosynthesis of glycerolipids including LPA, which preserves Hippo signaling.

A Novel Bioactive Peptide, T14, Selectively Activates mTORC1 Signalling: Therapeutic Implications for Neurodegeneration and Other Rapamycin-Sensitive Applications

T14 modulates calcium influx via the α-7 nicotinic acetylcholine receptor to regulate cell growth. Inappropriate triggering of this process has been implicated in Alzheimer's disease (AD) and cancer, whereas T14 blockade has proven therapeutic potential in in vitro, ex vivo and in vivo models of these pathologies. Mammalian target of rapamycin complex 1 (mTORC1) is critical for growth, however its hyperactivation is implicated in AD and cancer. T14 is a product of the longer 30mer-T30. Recent work shows that T30 drives neurite growth in the human SH-SY5Y cell line via the mTOR pathway. Here, we demonstrate that T30 induces an increase in mTORC1 in PC12 cells, and ex vivo rat brain slices containing substantia nigra, but not mTORC2. The increase in mTORC1 by T30 in PC12 cells is attenuated by its blocker, NBP14. Moreover, in post-mortem human midbrain, T14 levels correlate significantly with mTORC1. Silencing mTORC1 reverses the effects of T30 on PC12 cells measured via AChE release in undifferentiated PC12 cells, whilst silencing mTORC2 does not. This suggests that T14 acts selectively via mTORC1. T14 blockade offers a preferable alternative to currently available blockers of mTOR as it would enable selective blockade of mTORC1, thereby reducing side effects associated with generalised mTOR blockade.

Hepatocyte β-catenin loss is compensated by Insulin-mTORC1 activation to promote liver regeneration

BACKGROUND AND AIMS

Liver regeneration (LR) following partial hepatectomy (PH) occurs via activation of various signaling pathways. Disruption of a single pathway can be compensated by activation of another pathway to continue LR. The Wnt-β-catenin pathway is activated early during LR and conditional hepatocyte loss of β-catenin delays LR. Here, we study mechanism of LR in the absence of hepatocyte-β-catenin.

APPROACH AND RESULTS

Eight-week-old hepatocyte-specific Ctnnb1 knockout mice (β-catenin ΔHC ) were subjected to PH. These animals exhibited decreased hepatocyte proliferation at 40-120 h and decreased cumulative 14-day BrdU labeling of <40%, but all mice survived, suggesting compensation. Insulin-mediated mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) activation was uniquely identified in the β-catenin ΔHC mice at 72-96 h after PH. Deletion of hepatocyte regulatory-associated protein of mTOR (Raptor), a critical mTORC1 partner, in the β-catenin ΔHC mice led to progressive hepatic injury and mortality by 30 dys. PH on early stage nonmorbid Raptor ΔHC -β-catenin ΔHC mice led to lethality by 12 h. Raptor ΔHC mice showed progressive hepatic injury and spontaneous LR with β-catenin activation but died by 40 days. PH on early stage nonmorbid Raptor ΔHC mice was lethal by 48 h. Temporal inhibition of insulin receptor and mTORC1 in β-catenin ΔHC or controls after PH was achieved by administration of linsitinib at 48 h or rapamycin at 60 h post-PH and completely prevented LR leading to lethality by 12-14 days.

CONCLUSIONS

Insulin-mTORC1 activation compensates for β-catenin loss to enable LR after PH. mTORC1 signaling in hepatocytes itself is critical to both homeostasis and LR and is only partially compensated by β-catenin activation. Dual inhibition of β-catenin and mTOR may have notable untoward hepatotoxic side effects.

Elevated Nuclear PHGDH Synergistically Functions with cMyc to Reshape the Immune Microenvironment of Liver Cancer

Herein, we observed that nuclear localization of phosphoglycerate dehydrogenase (PHGDH) is associated with poor prognosis in liver cancer, and Phgdh is required for liver cancer progression in a mouse model. Unexpectedly, impairment of Phgdh enzyme activity exerts a slight effect in a liver cancer model. In liver cancer cells, the aspartate kinase-chorismate mutase-tyrA prephenate dehydrogenase (ACT) domain of PHGDH binds nuclear cMyc to form a transactivation axis, PHGDH/p300/cMyc/AF9, which drives chemokine CXCL1 and IL8 gene expression. Then, CXCL1 and IL8 promote neutrophil recruitment and enhance tumor-associated macrophage (TAM) filtration in the liver, thereby advancing liver cancer. Forced cytosolic localization of PHGDH or destruction of the PHGDH/cMyc interaction abolishes the oncogenic function of nuclear PHGDH. Depletion of neutrophils by neutralizing antibodies greatly hampers TAM filtration. These findings reveal a nonmetabolic role of PHGDH with altered cellular localization and suggest a promising drug target for liver cancer therapy by targeting the nonmetabolic region of PHGDH.

Phosphomevalonate Kinase Controls β-Catenin Signaling via the Metabolite 5-Diphosphomevalonate

β-catenin signaling is abnormally activated in cancer. Here, this work screens the mevalonate metabolic pathway enzyme PMVK to stabilize β-catenin signaling using a human genome-wide library. On the one hand, PMVK-produced MVA-5PP competitively binds to CKIα to prevent β-catenin Ser45 phosphorylation and degradation. On the other hand, PMVK functions as a protein kinase to directly phosphorylate β-catenin Ser184 to increase its protein nuclear localization. This synergistic effect of PMVK and MVA-5PP together promotes β-catenin signaling. In addition, PMVK deletion impairs mouse embryonic development and causes embryonic lethal. PMVK deficiency in liver tissue alleviates DEN/CCl₄ -induced hepatocarcinogenesis. Finally, the small molecule inhibitor of PMVK, PMVKi5, is developed and PMVKi5 inhibits carcinogenesis of liver and colorectal tissues. These findings reveal a non-canonical function of a key metabolic enzyme PMVK and a novel link between the mevalonate pathway and β-catenin signaling in carcinogenesis providing a new target for clinical cancer therapy.

A mixed blessing for liver transplantation patients - Rapamycin

BACKGROUND

Liver transplantation (LT) is an effective treatment option for end-stage liver disease. Mammalian target of rapamycin (mTOR) inhibitors, such as rapamycin, are widely used post LT.

DATA SOURCES

In this review, we focused on the anti-cancer activities and metabolic side effects of rapamycin after LT. The literature available on PubMed for the period of January 1999-September 2022 was reviewed. The key words were rapamycin, sirolimus, liver transplantation, hepatocellular carcinoma, diabetes, and lipid metabolism disorder.

RESULTS

Rapamycin has shown excellent effects and is safer than other immunosuppressive regimens. It has exhibited excellent anti-cancer activity and has the potential in preventing hepatocellular carcinoma (HCC) recurrence post LT. Rapamycin is closely related to two long-term complications after LT, diabetes and lipid metabolism disorders.

CONCLUSIONS

Rapamycin prevents HCC recurrence post LT in some patients, but it also induces metabolic disorders. Reasonable use of rapamycin benefits the liver recipients.

Is liver regeneration key in hepatocellular carcinoma development?

The liver is the largest organ of the mammalian body and has the remarkable ability to fully regenerate in order to maintain tissue homeostasis. The adult liver consists of hexagonal lobules, each with a central vein surrounded by six portal triads localized in the lobule border containing distinct parenchymal and nonparenchymal cells. Because the liver is continuously exposed to diverse stress signals, several sophisticated regenerative processes exist to restore its functional status following impairment. However, these stress signals can affect the liver's capacity to regenerate and may lead to the development of hepatocellular carcinoma (HCC), one of the most aggressive liver cancers. Here, we review the mechanisms of hepatic regeneration and their potential to influence HCC development.

Spatiotemporal Metabolic Liver Zonation and Consequences on Pathophysiology

Hepatocytes are the main workers in the hepatic factory, managing metabolism of nutrients and xenobiotics, production and recycling of proteins, and glucose and lipid homeostasis. Division of labor between hepatocytes is critical to coordinate complex complementary or opposing multistep processes, similar to distributed tasks at an assembly line. This so-called metabolic zonation has both spatial and temporal components. Spatial distribution of metabolic function in hepatocytes of different lobular zones is necessary to perform complex sequential multistep metabolic processes and to assign metabolic tasks to the right environment. Moreover, temporal control of metabolic processes is critical to align required metabolic processes to the feeding and fasting cycles. Disruption of this complex spatiotemporal hepatic organization impairs key metabolic processes with both local and systemic consequences. Many metabolic diseases, such as nonalcoholic steatohepatitis and diabetes, are associated with impaired metabolic liver zonation. Recent technological advances shed new light on the spatiotemporal gene expression networks controlling liver function and how their deregulation may be involved in a large variety of diseases. We summarize the current knowledge about spatiotemporal metabolic liver zonation and consequences on liver pathobiology.

Cancer stem cell-immune cell collusion in immunotherapy

Immunotherapy has pioneered a new era of tumor treatment, in which the immune checkpoint blockade (ICB) exerts significant superiority in overcoming tumor immune escape. However, the formation of an immune-suppressive tumor microenvironment (TME) and the lack of effective activation of the immune response have become major obstacles limiting its development. Emerging reports indicate that cancer stem cells (CSCs) potentially play important roles in treatment resistance and progressive relapse, while current research is usually focused on CSCs themselves. In this review, we mainly emphasize the collusions between CSCs and tumor-infiltrating immune cells. We focus on the summary of CSC-immune cell crosstalk signaling pathways in ICB resistance and highlight the application of targeted drugs to improve the ICB response.

Hepatocellular Carcinomas with Concomitant Mutations of TERT, TP53, and CTNNB1: Is There a Role for Artificial Intelligence?

TP53, CTNNB1, and TERT-promoter mutations are the most common driver mutations in hepatocellular carcinoma (HCC). The morphological and genetical HCC heterogeneities are difficult to discriminate by the eye of the pathologist. Here, we describe two rare cases of HCC with simultaneous co-mutation of all three of genes, which represent a poorly described occurrence in the literature. In these two cases, areas with different tumor grade and different β-catenin and Glutamine Synthetase expression (performed by automated immunohistochemistry) were observed. NGS analysis was performed in these different areas, to check for potential diversity of mutation burden on the different regions, but no differences were found: all micro-areas analyzed showed the co-presence of mutations in TP53, CTNNB1, and TERT. The evidence that all mutations were found in all the different areas analyzed by NGS leads to hypothesize that the tumor is not composed of different clones harboring different mutations. All the variants are harbored by the same neoplastic clone, albeit leading to different phenotypes. Mutation prediction Artificial Intelligence models could help the morpho-genetic classification of HCC in the future, since they can find variabilities not obvious to the human eye, with increased sensitivity, specificity and reproducibility.

Unraveling the Sweet Secrets of HCC: Glucometabolic Rewiring in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the primary form of liver cancer. It causes ∼ 800 000 deaths per year, which is expected to increase due to increasing rates of obesity and metabolic dysfunction associated steatotic liver disease (MASLD). Current therapies include immune checkpoint inhibitors, tyrosine kinase inhibitors, and monoclonal antibodies, but these therapies are not satisfactorily effective and often come with multiple side effects and recurrences. Metabolic reprogramming plays a significant role in HCC progression and is often conserved between tumor types. Thus, targeting rewired metabolic pathways could provide an attractive option for targeting tumor cells alone or in conjunction with existing treatments. Therefore, there is an urgent need to identify novel targets involved in cancer-mediated metabolic reprogramming in HCC. In this review, we provide an overview of molecular rewiring and metabolic reprogramming of glucose metabolism in HCC to understand better the concepts that might widen the therapeutic window against this deadly cancer.

Lactylome analysis suggests lactylation-dependent mechanisms of metabolic adaptation in hepatocellular carcinoma

Enhanced glycolysis and accumulation of lactate is a common feature in various types of cancer. Intracellular lactate drives a recently described type of posttranslational modification, lysine lactylation (Kla), on core histones. However, the impact of lactylation on biological processes of tumour cells remains largely unknown. Here we show a global lactylome profiling on a prospectively collected hepatitis B virus-related hepatocellular carcinoma (HCC) cohort. Integrative lactylome and proteome analysis of the tumours and adjacent livers identifies 9,275 Kla sites, with 9,256 sites on non-histone proteins, indicating that Kla is a prevalent modification beyond histone proteins and transcriptional regulation. Notably, Kla preferentially affects enzymes involved in metabolic pathways, including the tricarboxylic acid cycle, and carbohydrate, amino acid, fatty acid and nucleotide metabolism. We further verify that lactylation at K28 inhibits the function of adenylate kinase 2, facilitating the proliferation and metastasis of HCC cells. Our study therefore reveals that Kla plays an important role in regulating cellular metabolism and may contribute to HCC progression.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Glutamine synthetase limits β-catenin-mutated liver cancer growth by maintaining nitrogen homeostasis and suppressing mTORC1

Glutamine synthetase (GS) catalyzes de novo synthesis of glutamine that facilitates cancer cell growth. In the liver, GS functions next to the urea cycle to remove ammonia waste. As a dysregulated urea cycle is implicated in cancer development, the impact of GS's ammonia clearance function has not been explored in cancer. Here, we show that oncogenic activation of β-catenin (encoded by CTNNB1) led to a decreased urea cycle and elevated ammonia waste burden. While β-catenin induced the expression of GS, which is thought to be cancer promoting, surprisingly, genetic ablation of hepatic GS accelerated the onset of liver tumors in several mouse models that involved β-catenin activation. Mechanistically, GS ablation exacerbated hyperammonemia and facilitated the production of glutamate-derived nonessential amino acids, which subsequently stimulated mechanistic target of rapamycin complex 1 (mTORC1). Pharmacological and genetic inhibition of mTORC1 and glutamic transaminases suppressed tumorigenesis facilitated by GS ablation. While patients with hepatocellular carcinoma, especially those with CTNNB1 mutations, have an overall defective urea cycle and increased expression of GS, there exists a subset of patients with low GS expression that is associated with mTORC1 hyperactivation. Therefore, GS-mediated ammonia clearance serves as a tumor-suppressing mechanism in livers that harbor β-catenin activation mutations and a compromised urea cycle.

Excessive gluconeogenesis causes the hepatic insulin resistance paradox and its sequelae

Background

Hepatic insulin signaling suppresses gluconeogenesis but promotes de novo lipid synthesis. Paradoxically, hepatic insulin resistance (HIR) enhances both gluconeogenesis and de novo lipid synthesis. Elucidation of the etiology of this paradox, which participates in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, the metabolic syndrome and hepatocellular carcinoma, has not been fully achieved.

Scope of review

This article briefly outlines the previously proposed hypotheses on the etiology of the HIR paradox. It then discusses literature consistent with an alternative hypothesis that excessive gluconeogenesis, the direct effect of HIR, is responsible for the aberrant lipogenesis. The mechanisms involved therein are explained, involving de novo synthesis of fructose and uric acid, promotion of glutamine anaplerosis, and induction of glucagon resistance. Thus, gluconeogenesis via lipogenesis promotes hepatic steatosis, a component of NAFLD, and dyslipidemia. Gluconeogenesis-centred mechanisms for the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH) and fibrosis are suggested. That NAFLD often precedes and predicts type 2 diabetes is explained by the ability of lipogenesis to cushion against blood glucose dysregulation in the earlier stages of NAFLD.

Major conclusions

HIR-induced excessive gluconeogenesis is a major cause of the HIR paradox and its sequelae. Such involvement of gluconeogenesis in lipid synthesis rationalizes the fact that several types of antidiabetic drugs ameliorate NAFLD. Thus, dietary, lifestyle and pharmacological targeting of HIR and hepatic gluconeogenesis may be a most viable approach for the prevention and management of the HIR-associated network of diseases.

Wnt/β-Catenin Signaling as a Driver of Stemness and Metabolic Reprogramming in Hepatocellular Carcinoma

Simple Summary

Aberrant Wnt/β-catenin signaling has been reported to play crucial role in pathogenesis of hepatocellular carcinoma (HCC). In this review, we focus on the regulatory role of Wnt/β-catenin signaling in cancer stemness and metabolic reprogramming, which are two emerging hallmarks of cancer. Understanding the role of Wnt/β-catenin signaling in regulation of the above processes reveals novel therapeutic strategy against this deadly disease.

Abstract

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide due to its high rates of tumor recurrence and metastasis. Aberrant Wnt/β-catenin signaling has been shown to play a significant role in HCC development, progression and clinical impact on tumor behavior. Accumulating evidence has revealed the critical involvement of Wnt/β-catenin signaling in driving cancer stemness and metabolic reprogramming, which are regarded as emerging cancer hallmarks. In this review, we summarize the regulatory mechanism of Wnt/β-catenin signaling and its role in HCC. Furthermore, we provide an update on the regulatory roles of Wnt/β-catenin signaling in metabolic reprogramming, cancer stemness and drug resistance in HCC. We also provide an update on preclinical and clinical studies targeting Wnt/β-catenin signaling alone or in combination with current therapies for effective cancer therapy. This review provides insights into the current opportunities and challenges of targeting this signaling pathway in HCC.

Single-cell spatial transcriptomics reveals a dynamic control of metabolic zonation and liver regeneration by endothelial cell Wnt2 and Wnt9b

The conclusive identity of Wnts regulating liver zonation (LZ) and regeneration (LR) remains unclear despite an undisputed role of β-catenin. Using single-cell analysis, we identified a conserved Wnt2 and Wnt9b expression in endothelial cells (ECs) in zone 3. EC-elimination of Wnt2 and Wnt9b led to both loss of β-catenin targets in zone 3, and re-appearance of zone 1 genes in zone 3, unraveling dynamicity in the LZ process. Impaired LR observed in the knockouts phenocopied models of defective hepatic Wnt signaling. Administration of a tetravalent antibody to activate Wnt signaling rescued LZ and LR in the knockouts and induced zone 3 gene expression and LR in controls. Administration of the agonist also promoted LR in acetaminophen overdose acute liver failure (ALF) fulfilling an unmet clinical need. Overall, we report an unequivocal role of EC-Wnt2 and Wnt9b in LZ and LR and show the role of Wnt activators as regenerative therapy for ALF.

SAC3D1 activates Wnt/β‑catenin signalling in hepatocellular carcinoma

β‑catenin accumulates in hepatocellular carcinoma (HCC); therefore, understanding the mechanism of Wnt/β‑catenin pathway activation is important for HCC therapy. SAC3 domain containing 1 (SAC3D1) is involved in numerous types of cancer, such as gastric cancer. To the best of our knowledge, however, the role of SAC3D1 in HCC has not yet been elucidated. Here, the expression of SAC3D in HCC was examined by quantitative PCR, western blotting and immunohistochemistry. The function of SAC3D1 in HCC were examined using Cell Counting Kit‑8 and anchorage‑independent growth assay. It was found that the levels of SAC3D1 mRNA and protein were upregulated in HCC. When SAC3D1 was overexpressed, the proliferation of HCC cells was promoted; when the expression of SAC3D1 was disrupted, HCC cell growth was inhibited. When the molecular mechanism was investigated using immunoprecipitation, it was found that SAC3D1 interacted with axin, inhibiting ubiquitination of β‑catenin and elevating protein levels of β‑catenin. In summary, the present study revealed the promoting function of SAC3D1 in the progression of HCC. SAC3D1 may be a promising target for HCC therapy.

Hepatocellular carcinoma downstaging for liver transplantation in the era of systemic combined therapy with anti-VEGF/TKI and immunotherapy

Hepatocellular carcinoma remains a global health challenge affecting close to 1 million cases yearly. Liver transplantation provides the best long-term outcomes for those meeting strict criteria. Efforts have been made to expand these criteria, whereas others have attempted downstaging approaches. Although locoregional approaches to downstaging are appealing and have demonstrated efficacy, limitations and challenges exists including poor imaging modality to assess response and appropriate endpoints along the process. Recent advances in systemic treatments including immune checkpoint inhibitors alone or in combination with tyrosine kinase inhibitors have prompted the discussion regarding their role for downstaging disease prior to transplantation. Here, we provide a review of prior locoregional approaches for downstaging, new systemic agents and their role for downstaging, and finally, key and critical considerations of the assessment, endpoints, and optimal designs in clinical trials to address this key question.

Oncogenic β-catenin stimulation of AKT2-CAD-mediated pyrimidine synthesis is targetable vulnerability in liver cancer

β-Catenin encoding gene CTNNB1 is known as the most frequently mutated proto-oncogene in liver cancer. We report that active β-catenin is essential in initiation and advancement of hepatocarcinogenesis. As a transcriptional activator of AKT2, β-catenin potentiates AKT2 phosphorylation of CAD, which in return stimulates de novo pyrimidine synthesis and liver cancer development. β-Catenin, AKT2, and pyrimidine synthesis inhibitors are promising therapeutics for the treatment of oncogenic β-catenin–associated cancer.

CTNNB1, encoding β-catenin protein, is the most frequently altered proto-oncogene in hepatic neoplasms. In this study, we studied the significance and pathological mechanism of CTNNB1 gain-of-function mutations in hepatocarcinogenesis. Activated β-catenin not only triggered hepatic tumorigenesis but also exacerbated Tp53 deletion or hepatitis B virus infection–mediated liver cancer development in mouse models. Using untargeted metabolomic profiling, we identified boosted de novo pyrimidine synthesis as the major metabolic aberration in β-catenin mutant cell lines and livers. Oncogenic β-catenin transcriptionally stimulated AKT2, which then phosphorylated the rate-limiting de novo pyrimidine synthesis enzyme CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, dihydroorotase) on S1406 and S1859 to potentiate nucleotide synthesis. Moreover, inhibition of β-catenin/AKT2-stimulated pyrimidine synthesis axis preferentially repressed β-catenin mutant cell proliferation and tumor formation. Therefore, β-catenin active mutations are oncogenic in various preclinical liver cancer models. Stimulation of β-catenin/AKT2/CAD signaling cascade on pyrimidine synthesis is an essential and druggable vulnerability for β-catenin mutant liver cancer.

Preoperative radiomics model using gadobenate dimeglumine-enhanced magnetic resonance imaging for predicting β-catenin mutation in patients with hepatocellular carcinoma: A retrospective study

Objective

To compare and evaluate radiomics models to preoperatively predict β-catenin mutation in patients with hepatocellular carcinoma (HCC).

Methods

Ninety-eight patients who underwent preoperative gadobenate dimeglumine (Gd-BOPTA)-enhanced MRI were retrospectively included. Volumes of interest were manually delineated on arterial phase, portal venous phase, delay phase, and hepatobiliary phase (HBP) images. Radiomics features extracted from different combinations of imaging phases were analyzed and validated. A linear support vector classifier was applied to develop different models.

Results

Among all 15 types of radiomics models, the model with the best performance was seen in the R^HBP radiomics model. The area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, specificity of the R^HBP radiomics model in the training and validation cohorts were 0.86 (95% confidence interval [CI], 0.75–0.93), 0.75, 1.0, and 0.65 and 0.82 (95% CI, 0.63–0.93), 0.73, 0.67, and 0.76, respectively. The combined model integrated radiomics features in the R^HBP radiomics model, and signatures in the clinical model did not improve further compared to the single HBP radiomics model with AUCs of 0.86 and 0.76. Good calibration for the best R^HBP radiomics model was displayed in both cohorts; the decision curve showed that the net benefit could achieve 0.15. The most important radiomics features were low and high gray-level zone emphases based on gray-level size zone matrix with the same Shapley additive explanation values of 0.424.

Conclusion

The R^HBP radiomics model may be used as an effective model indicative of HCCs with β-catenin mutation preoperatively and thus could guide personalized medicine.

Pregnane X receptor promotes liver enlargement in mice through the spatial induction of hepatocyte hypertrophy and proliferation

Nuclear receptor pregnane X receptor (PXR) can induce significant liver enlargement through hepatocyte hypertrophy and proliferation. A previous report showed that during the process of PXR-induced liver enlargement, hepatocyte hypertrophy occurs around the central vein (CV) area while hepatocyte proliferation occurs around the portal vein (PV) area. However, the features of this spatial change remain unclear. Therefore, this study aims to explore the features of the spatial changes in hepatocytes in PXR-induced liver enlargement. PXR-induced spatial changes in hepatocyte hypertrophy and proliferation were confirmed in C57BL/6 mice. The liver was perfused with digitonin to destroy the hepatocytes around the CV or PV areas, and then the regional expression of proteins related to hepatocyte hypertrophy and proliferation was further measured. The results showed that the expression of PXR downstream proteins, such as cytochrome P450 (CYP) 3A11, CYP2B10, P-glycoprotein (P-gp) and organ anion transporting polypeptide 2 (OATP2) was upregulated around the CV area, while the expression of proliferation-related proteins such as cyclin B1 (CCNB1), cyclin D1 (CCND1) and serine/threonine NIMA-related kinase 2 (NEK2) was upregulated around the PV area. At the same time, the expression of cyclin-dependent kinase inhibitors such as retinoblastoma-like protein 2 (RBL2), cyclin-dependent kinase inhibitor 1B (CDKN1B) and CDKN1A was downregulated around the PV area. This study demonstrated that the spatial change in PXR-induced hepatocyte hypertrophy and proliferation is associated with the regional expression of PXR downstream targets and proliferation-related proteins and the regional distribution of triglycerides (TGs). These findings provide new insight into the understanding of PXR-induced hepatomegaly.

Recent insights into the pathogeneses and therapeutic targets of liver diseases: Summary of the 4th Chinese American Liver Society/Society of Chinese Bioscientists in America Hepatology Division Symposium in 2021

The 4th Chinese American Liver Society (CALS)/Society of Chinese Bioscientists in America (SCBA) Hepatology Division Annual Symposium was held virtually on October 29-30, 2021. The goal of the CALS Symposium was to present and discuss the recent research data on the pathogeneses and therapeutic targets of liver diseases among the CALS members, trainees and invited speakers. Here we briefly introduce the history of the CALS/SCBA Hepatology Division and highlight the presentations that focus on the current progresses on basic and translational research in liver metabolism, bile acid biology, alcohol-related liver disease, drug-induced liver injury, cholestatic liver injury, non-alcoholic fatty liver disease/non-alcoholic steatohepatitis and liver cancer.

β-Catenin signaling in hepatocellular carcinoma

Deregulated Wnt/β-catenin signaling is one of the main genetic alterations in human hepatocellular carcinoma (HCC). Comprehensive genomic analyses have revealed that gain-of-function mutation of CTNNB1, which encodes β-catenin, and loss-of-function mutation of AXIN1 occur in approximately 35% of human HCC samples. Human HCCs with activation of the Wnt/β-catenin pathway demonstrate unique gene expression patterns and pathological features. Activated Wnt/β-catenin synergizes with multiple signaling cascades to drive HCC formation, and it functions through its downstream effectors. Therefore, strategies targeting Wnt/β-catenin have been pursued as possible therapeutics against HCC. Here, we review the genetic alterations and oncogenic roles of aberrant Wnt/β-catenin signaling during hepatocarcinogenesis. In addition, we discuss the implication of this pathway in HCC diagnosis, classification, and personalized treatment.

Glutamine synthetase licenses APC/C-mediated mitotic progression to drive cell growth

Tumors can reprogram the functions of metabolic enzymes to fuel malignant growth; however, beyond their conventional functions, key metabolic enzymes have not been found to directly govern cell mitosis. Here, we report that glutamine synthetase (GS) promotes cell proliferation by licensing mitotic progression independently of its metabolic function. GS depletion, but not impairment of its enzymatic activity, results in mitotic arrest and multinucleation across multiple lung and liver cancer cell lines, patient-derived organoids and xenografted tumors. Mechanistically, GS directly interacts with the nuclear pore protein NUP88 to prevent its binding to CDC20. Such interaction licenses activation of the CDC20-mediated anaphase-promoting complex or cyclosome to ensure proper metaphase-to-anaphase transition. In addition, GS is overexpressed in human non-small cell lung cancer and its depletion reduces tumor growth in mice and increases the efficacy of microtubule-targeted chemotherapy. Our findings highlight a moonlighting function of GS in governing mitosis and illustrate how an essential metabolic enzyme promotes cell proliferation and tumor development, beyond its main metabolic function.

Role and Regulation of Wnt/β-Catenin in Hepatic Perivenous Zonation and Physiological Homeostasis

Metabolic heterogeneity or functional zonation is a key characteristic of the liver that allows different metabolic pathways to be spatially regulated within the hepatic system and together contribute to whole body homeostasis. These metabolic pathways are segregated along the portocentral axis of the liver lobule into three hepatic zones: periportal, intermediate or midzonal, and perivenous. The liver performs complementary or opposing metabolic functions within different hepatic zones while synergistic functions are regulated by overlapping zones, thereby maintaining the overall physiological stability. The Wnt/β-catenin signaling pathway is well known for its role in liver growth, development, and regeneration. In addition, the Wnt/β-catenin pathway plays a fundamental and dominant role in hepatic zonation and signals to orchestrate various functions of liver metabolism and pathophysiology. The β-catenin protein is the central player in the Wnt/β-catenin signaling cascade, and its activation is crucial for metabolic patterning of the liver. However, dysregulation of Wnt/β-catenin signaling is also implicated in different liver pathologies, including those associated with metabolic syndrome. β-Catenin is preferentially localized in the central region of the hepatic lobule surrounding the central vein and regulates multiple functions of this region. This review outlines the role of Wnt/β-catenin signaling pathway in controlling the different metabolic processes surrounding the central vein and its relation to liver homeostasis and dysfunction.

An RNA-RNA crosstalk network involving HMGB1 and RICTOR facilitates hepatocellular carcinoma tumorigenesis by promoting glutamine metabolism and impedes immunotherapy by PD-L1+ exosomes activity

Hepatocellular carcinoma (HCC) is the global leading cause of cancer-related deaths due to the deficiency of targets for precision therapy. A new modality of epigenetic regulation has emerged involving RNA–RNA crosstalk networks where two or more competing endogenous RNAs (ceRNAs) bind to the same microRNAs. However, the contribution of such mechanisms in HCC has not been well studied. Herein, potential HMGB1-driven RNA–RNA crosstalk networks were evaluated at different HCC stages, identifying the mTORC2 component RICTOR as a potential HMGB1 ceRNA in HBV⁺ early stage HCC. Indeed, elevated HMGB1 mRNA was found to promote the expression of RICTOR mRNA through competitively binding with the miR-200 family, especially miR-429. Functional assays employing overexpression or interference strategies demonstrated that the HMGB1 and RICTOR 3′untranslated regions (UTR) epigenetically promoted the malignant proliferation, self-renewal, and tumorigenesis in HCC cells. Intriguingly, interference against HMGB1 and RICTOR in HCC cells promoted a stronger anti-PD-L1 immunotherapy response, which appeared to associate with the production of PD-L1⁺ exosomes. Mechanistically, the HMGB1-driven RNA-RNA crosstalk network facilitated HCC cell glutamine metabolism via dual mechanisms, activating a positive feedback loop involving mTORC2-AKT-C-MYC to upregulate glutamine synthetase (GS) expression, and inducing mTORC1 signaling to derepress SIRT4 on glutamate dehydrogenase (GDH). Meanwhile, this crosstalk network could impede the efficacy of immunotherapy through mTORC1-P70S6K dependent PD-L1 production and PD-L1⁺ exosomes activity. In conclusion, our study highlights the non-coding regulatory role of HMGB1 with implications for RNA-based therapeutic targeting together with a prediction of anti-PD-L1 immunotherapy in HCC.

Enhanced Antitumor Effect in Liver Cancer by Amino Acid Depletion-Induced Oxidative Stress

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer. HCC cells consume large amounts of glutamine to survive, but can adapt to glutamine depletion in the presence of an exogenous asparagine. L-asparaginase (ASNase) converts glutamine and asparagine to glutamate and aspartate, respectively, and has been used to treat leukemia. Here we examined the effects of ASNase treatment on HCC cells and explored the potential impact of combining ASNase with the tyrosine kinase inhibitor lenvatinib (Len) for HCC treatment. Cell viability and death of HCC cell lines treated with either Len or ASNase alone or with Len and ASNase combined were determined. We assessed mRNA and protein expression levels of glutamine synthetase (GS) and asparagine synthetase (ASNS) by real-time quantitative PCR and immunoblotting. The antitumor effect of the combination therapy relative to Len or ASNase monotherapy was also evaluated in a xenograft tumor mouse model. ASNase treatment inhibited growth of SNU387 and SNU398 HCC cells, which have low GS and high ASNS expression levels, respectively, but did not clearly inhibit growth of the other cell lines. Len plus ASNase combination therapy synergistically inhibited proliferation and induced oxidative stress leading to cell death of some HCC cells lines. However, cell death of Huh7 cells, which express ASCT2, an important glutamine transporter for cancer cells, was not affected by the combination treatment. In a xenograft model, Len combined with ASNase significantly attenuated tumor development relative to mice treated with Len or ASNase alone. ASNase-mediated targeting of two amino acids, glutamine and asparagine, which are indispensable for HCC survival, induces oxidative stress and can be a novel cancer treatment option that exerts a synergistic effect when used in combination with Len.

The protein kinase activity of NME7 activates Wnt/β-Catenin signaling to promote one-carbon metabolism in hepatocellular carcinoma

Metabolic reprogramming by oncogenic signaling is a hallmark of cancer. Hyperactivation of Wnt/β-catenin signaling has been reported in hepatocellular carcinoma (HCC). However, the mechanisms inducing hyperactivation of Wnt/β-catenin signaling and strategies for targeting this pathway are incompletely understood. In this study, we find nucleoside diphosphate kinase 7 (NME7) to be a positive regulator of Wnt/β-catenin signaling. Upregulation of NME7 positively correlated with the clinical features of HCC. Knockdown of NME7 inhibited HCC growth in vitro and in vivo, while overexpression of NME7 cooperated with c-Myc to drive tumorigenesis in a mouse model and promote the growth of tumor-derived organoids. Mechanistically, NME7 bound and phosphorylated serine 9 of GSK3β to promote β-catenin activation. Furthermore, MTHFD2, the key enzyme in one-carbon metabolism, was a target gene of β-catenin and mediated the effects of NME7. Tumor-derived organoids with NME7 overexpression exhibited increased sensitivity to MTHFD2 inhibition. Additionally, expression levels of NME7, β-catenin and MTHFD2 correlated with each other and with poor prognosis in HCC patients. Collectively, this study emphasizes the crucial roles of NME7 protein kinase activity in promoting Wnt/β-catenin signaling and one-carbon metabolism, suggesting NME7 and MTHFD2 as potential therapeutic targets for HCC.

Oxygen and metabolic reprogramming in the tumor microenvironment influences metastasis homing

Tumor metastasis is the leading cause of cancer mortality, often characterized by abnormal cell growth and invasion to distant organs. The cancer invasion due to epithelial to mesenchymal transition is affected by metabolic and oxygen availability in the tumor-associated micro-environment. A precise alteration in oxygen and metabolic signaling between healthy and metastatic cells is a substantial probe for understanding tumor progression and metastasis. Molecular heterogeneity in the tumor microenvironment help to sustain the metastatic cell growth during their survival shift from low to high metabolic-oxygen-rich sites and reinforces the metastatic events. This review highlighted the crucial role of oxygen and metabolites in metastatic progression and exemplified the role of metabolic rewiring and oxygen availability in cancer cell adaptation. Furthermore, we have also addressed potential applications of altered oxygen and metabolic networking with tumor type that could be a signature pattern to assess tumor growth and chemotherapeutics efficacy in managing cancer metastasis.

Glucose and Amino Acid Metabolic Dependencies Linked to Stemness and Metastasis in Different Aggressive Cancer Types

Malignant cells are commonly characterised by being capable of invading tissue, growing self-sufficiently and uncontrollably, being insensitive to apoptosis induction and controlling their environment, for example inducing angiogenesis. Amongst them, a subpopulation of cancer cells, called cancer stem cells (CSCs) shows sustained replicative potential, tumor-initiating properties and chemoresistance. These characteristics make CSCs responsible for therapy resistance, tumor relapse and growth in distant organs, causing metastatic dissemination. For these reasons, eliminating CSCs is necessary in order to achieve long-term survival of cancer patients. New insights in cancer metabolism have revealed that cellular metabolism in tumors is highly heterogeneous and that CSCs show specific metabolic traits supporting their unique functionality. Indeed, CSCs adapt differently to the deprivation of specific nutrients that represent potentially targetable vulnerabilities. This review focuses on three of the most aggressive tumor types: pancreatic ductal adenocarcinoma (PDAC), hepatocellular carcinoma (HCC) and glioblastoma (GBM). The aim is to prove whether CSCs from different tumour types share common metabolic requirements and responses to nutrient starvation, by outlining the diverse roles of glucose and amino acids within tumour cells and in the tumour microenvironment, as well as the consequences of their deprivation. Beyond their role in biosynthesis, they serve as energy sources and help maintain redox balance. In addition, glucose and amino acid derivatives contribute to immune responses linked to tumourigenesis and metastasis. Furthermore, potential metabolic liabilities are identified and discussed as targets for therapeutic intervention.

Characterization of metabolic landscape in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide, accounting for approximately 75%-85% of primary liver cancers. Metabolic alterations have been labeled as an emerging hallmark of tumors. Specially, the last decades have registered a significant improvement in our understanding of the role of metabolism in driving the carcinogenesis and progression of HCC. In this paper, we provide a review of recent studies that investigated the metabolic traits of HCC with a specific focus on three common metabolic alterations involving glycolysis, lipid metabolism, and glutamine addiction which have been gaining much attention in the field of HCC. Next, we describe some representative diagnostic markers or tools, and promising treatment agents that are proposed on the basis of the aforementioned metabolic alterations for HCC. Finally, we present some challenges and directions that may promisingly speed up the process of developing objective diagnostic markers and therapeutic options underlying HCC. Specifically, we recommend future investigations to carefully take into account the influence of heterogeneity, control for study-specific confounds, and invite the validation of existing biomarkers.

Nuclear factor erythroid 2-related factor 2 and β-Catenin Coactivation in Hepatocellular Cancer: Biological and Therapeutic Implications

BACKGROUND AND AIMS

HCC remains a major unmet clinical need. Although activating catenin beta-1 (CTNNB1) mutations are observed in prominent subsets of HCC cases, these by themselves are insufficient for hepatocarcinogenesis. Coexpression of mutant CTNNB1 with clinically relevant co-occurrence has yielded HCCs. Here, we identify cooperation between β-catenin and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling in HCC.

APPROACH AND RESULTS

Public HCC data sets were assessed for concomitant presence of CTNNB1 mutations and either mutations in nuclear factor erythroid-2-related factor-2 (NFE2L2) or Kelch like-ECH-associated protein 1 (KEAP1), or Nrf2 activation by gene signature. HCC development in mice and similarity to human HCC subsets was assessed following coexpression of T41A-CTNNB1 with either wild-type (WT)-, G31A-, or T80K-NFE2L2. Based on mammalian target of rapamycin complex 1 activation in CTNNB1-mutated HCCs, response of preclinical HCC to mammalian target of rapamycin (mTOR) inhibitor was investigated. Overall, 9% of HCC cases showed concomitant CTNNB1 mutations and Nrf2 activation, subsets of which were attributable to mutations in NFE2L2/KEAP1. Coexpression of mutated CTNNB1 with mutant NFE2L2, but not WT-NFE2L2, led to HCC development and mortality by 12-14 weeks. These HCCs were positive for β-catenin targets, like glutamine synthetase and cyclin-D1, and Nrf2 targets, like NAD(P)H quinone dehydrogenase 1 and peroxiredoxin 1. RNA-sequencing and pathway analysis showed high concordance of preclinical HCC to human HCC subset showing activation of unique (iron homeostasis and glioblastoma multiforme signaling) and expected (glutamine metabolism) pathways. NFE2L2-CTNNB1 HCC mice were treated with mTOR inhibitor everolimus (5-mg/kg diet ad libitum), which led to >50% decrease in tumor burden.

CONCLUSIONS

Coactivation of β-catenin and Nrf2 is evident in 9% of all human HCCs. Coexpression of mutant NFE2L2 and mutant CTNNB1 led to clinically relevant HCC development in mice, which responded to mTOR inhibitors. Thus, this model has both biological and therapeutic implications.