Points of therapeutic intervention along the Wnt signaling pathway in hepatocellular carcinoma

Glutamine synthetase and hepatocellular carcinoma

Glutamine synthetase (GS) is an enzyme that converts ammonia and glutamate to glutamine using adenosine triphosphate. GS is expressed in the brain, kidney, and liver tissues under normal physiological conditions. GS is involved in abnormal lipid metabolism of the liver by catalyzing de novo synthesis of glutamine, thereby inducing liver inflammation. Metabolic dysfunction-associated steatotic liver diseases (MASLD), such as Metabolic Associated Fatty Liver Disease and Metabolic Associated Steato Hepatitis, are considered risk factors for HCC. GS may also be involved in the development and progression of hepatocellular carcinoma (HCC) through other signaling pathways, including the rapamycin (mTOR) and Wnt/β-catenin signaling pathways. Furthermore, the correct combination of HSP70, GPC3, and GS can improve the accuracy and precision of HCC diagnosis. However, the prognostic value of GS in different HCC populations remains controversial. The expression of GS affects the sensitivity of HCC cells to radiotherapy and chemotherapy. In addition, immunotherapy has been approved for the treatment of advanced HCC. This article delves into the development and application of GS in HCC, laying a theoretical foundation for the subsequent exploration of GS as a potential target for treating HCC.

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.

Targeting Wnt/β-Catenin Pathways in Primary Liver Tumours: From Microenvironment Signaling to Therapeutic Agents

Primary liver cancers (PLCs) are steadily increasing in incidence and mortality in the world. They have a poor prognosis due to their silent nature, late discovery and resistance to common chemotherapy. At present, there are limited treatment alternatives, and the understanding of PLC molecular aspects is essential to develop more efficient drugs and therapeutic surgical and loco-regional strategies. A clear causal link with liver damage, inflammation, and regeneration has been found in the occurrence of PLC over the last few decades. Physiologically, Wingless/It (Wnt)-β-catenin signaling plays a key role in liver development, metabolic zonation and regeneration. Loss of functional homeostasis of this pathway appears to be a major driver of carcinogenesis in the liver parenchyma. In the hepatic microenvironment, molecular deregulations that exceed the Wnt signaling biological capacity can induce tumor initiation and progression. Indeed, somatic mutations are identified in key components of canonical and non-canonical Wnt signaling and in PLCs and precancerous lesions. In this review, the altered functions of Wnt/β-catenin signaling are considered in human PLCs, with emphasis on hepatocellular carcinomas (HCC), cholangiocarcinomas (CCA) and hepatoblastomas (HB). Based on recent literature, we also focused on liver cancerogenesis through Wnt deregulation. An overview of preclinical and clinical studies on approved and experimental drugs, targeting the Wnt/β-catenin cascade in PLCs, is proposed. In addition, the clinical implication of molecule inhibitors that have been shown to possess activity against the Wnt pathway in association with conventional surgical and loco-regional therapies are reviewed.

Diwu Yanggan Modulates the Wnt/β-catenin Pathway and Inhibits Liver Carcinogenesis Signaling in 2-AAF/PH Model Rats

The activation of the Wnt/β-catenin signaling pathway in oval cells after liver injury is implicated in hepatocarcinogenesis. Diwu Yanggan capsule is a Chinese herbal medicine that has been used for treating liver disorder. The present study aimed to examine the mechanism by which Diwu Yanggan inhibits liver carcinogenesis, and the involvement of the Wnt/β-catenin signaling pathway. Diwu Yanggan capsule was administered to 2-acetaminofluorene/partial hepatectomy (2-AAF/PH) rats, a murine model of liver injury. The biomarkers of oval cells and key proteins in the Wnt/β-catenin signaling pathway were assessed on postoperative day 8, 10, 14, 17, 19 and 22. The results showed that treatment with Diwu Yanggan was associated with reduced expression of oval cell and stem cell biomarkers in the 2-AAF/PH animals. The expression pattern of key proteins in the Wnt/β-catenin pathway was altered in Diwu Yanggan-treated animals, indicating that the Diwu Yanggan treatment accelerated the activation of the Wnt/β-catenin pathway in the initial stage and contributed to its deactivation in the later stage. Histological findings indicated that hepatocyte proliferation was suppressed in Diwu Yanggan-treated animals, compared with untreated 2-AAF/PH animals. Taken together, Diwu Yanggan capsule may reduce the risk of hepatocarcinogenesis by modulating the Wnt/β-catenin signaling pathway.

CWP232228 targets liver cancer stem cells through Wnt/β-catenin signaling: a novel therapeutic approach for liver cancer treatment

Liver cancer stem cells (CSCs) are resistant to conventional chemotherapy and radiation, which may destroy tumor masses, but not all liver CSCs contribute to tumor initiation, metastasis, and relapse. In the present study, we showed that liver CSCs with elevated Wnt/β-catenin signaling possess much greater self-renewal and clonogenic potential. We further documented that the increased clonogenic potential of liver CSCs is highly associated with changes in Wnt/β-catenin signaling and that Wnt/β-catenin signaling activity is positively correlated with CD133 expression and aldehyde dehydrogenase (ALDH) enzymatic activity. Notably, the small molecule inhibitor CWP232228, which antagonizes the binding of β-catenin to TCF in the nucleus, inhibits Wnt/β-catenin signaling and depletes CD133⁺/ALDH⁺ liver CSCs, thus ultimately diminishing the self-renewal capacity of CSCs and decreasing tumorigenicity in vitro and in vivo. Taken together, our findings suggest that CWP232228 acts as a candidate therapeutic agent for liver cancer by preferentially targeting liver CSCs.

Down-regulation of the Wnt/β-catenin signaling pathway by Cacnb4

The β4 isoform of the β-subunits of voltage-gated calcium channel regulates cell proliferation and cell cycle progression. Herein we show that coexpression of the β4-subunit with actors of the canonical Wnt/β-catenin signaling pathway in a hepatoma cell line inhibits Wnt-responsive gene transcription and decreases cell division, in agreement with the role of the Wnt pathway in cell proliferation. β4-subunit-mediated inhibition of Wnt signaling is observed in the presence of LiCl, an inhibitor of glycogen synthase kinase (GSK3) that promotes β-catenin translocation to the nucleus. Expression of β4-subunit mutants that lost the ability to translocate to the nucleus has no effect on Wnt signaling, suggesting that β4-subunit inhibition of Wnt signaling occurs downstream from GSK3 and requires targeting of β4-subunit to the nucleus. β4-subunit coimmunoprecipitates with the TCF4 transcription factor and overexpression of TCF4 reverses the effect of β4-subunit on the Wnt pathway. We thus propose that the interaction of nuclear β4-subunit with TCF4 prevents β-catenin binding to TCF4 and leads to the inhibition of the Wnt-responsive gene transcription. Thereby, our results show that β4-subunit is a TCF4 repressor and therefore appears as an interesting candidate for the regulation of this pathway in neurons where β4-subunit is specifically expressed.

Promising new strategies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer death worldwide. It usually arises based on a background of chronic liver diseases, defined as the hypercarcinogenic state. The current treatment options for HCC ranging from locoregional treatments to chemotherapies, including sorafenib, effectively regulate the limited sizes and numbers of the nodules. However, these treatments remain unsatisfactory because they have insufficient antitumor effects on the large and numerous nodules associated with HCC and because of a high recurrence rate in the surrounding inflamed liver. To develop novel and promising therapies with higher antitumor effects, recent progress in identifying molecular targets and developing immunological procedures for HCC are reviewed. The molecular targets discussed include the intracellular signaling pathways of protein kinase B/mammalian target of rapamycin and RAS/RAF/mitogen-activated protein kinase, Wnt/β-catenin and glutamine synthetase, insulin-like growth factor, signal transducer and activator of transcription 3, nuclear factor-κB and telomerase reverse transcriptase, and c-MET. Immunological studies have focused mainly on target identification, T cells, natural killer cells, dendritic cells, natural killer T cells, and vaccine development.

Wnt-/-β-catenin pathway signaling in human hepatocellular carcinoma

The molecular basis of the carcinogenesis of hepatocellular carcinoma (HCC) has not been adequately clarified, which negatively impacts the development of targeted therapy protocols for this overwhelming neoplasia. The aberrant activation of signaling in the HCC is primarily due to the deregulated expression of the components of the Wnt-/-β-catenin. This leads to the activation of β-catenin/T-cell factor-dependent target genes that control cell proliferation, cell cycle, apoptosis, and cell motility. The deregulation of the Wnt pathway is an early event in hepatocarcinogenesis. An aggressive phenotype was associated with HCC, since this pathway is implicated in the proliferation, migration, and invasiveness of cancer cells, regarding the cell’s own survival. The disruption of the signaling cascade Wnt-/-β-catenin has shown anticancer properties in HCC’s clinical evaluations of therapeutic molecules targeted for blocking the Wnt signaling pathway for the treatment of HCC, and it represents a promising perspective. The key to bringing this strategy in to clinical practice is to identify new molecules that would be effective only in tumor cells with aberrant signaling β-catenin.

Biomarkers for hepatocellular carcinoma: diagnostic and therapeutic utility

Because of the high prevalence and associated-mortality of hepatocellular carcinoma (HCC), early diagnosis of the disease is vital for patient survival. In this regard, tumor size is one of the two main prognostic factors for surgical resection, which constitutes the only curative treatment for HCC along with liver transplantation. However, techniques for HCC surveillance and diagnosis that are currently used in clinical practice have certain limitations that may be inherent to the tumor development. Thus, it is important to continue efforts in the search for biomarkers that increase diagnostic accuracy for HCC. In this review, we focus on different biological sources of candidate biomarkers for HCC diagnosis. Although those biomarkers identified from biological samples obtained by noninvasive methods have greater diagnostic value, we have also considered those obtained from liver tissue because of their potential therapeutic value. To date, sorafenib is the only US Food and Drug Administration-approved antineoplastic for HCC. However, this therapeutic agent shows very low tumor response rates and frequently causes acquired resistance in HCC patients. We discuss the use of HCC biomarkers as therapeutic targets themselves, or as targets to increase sensitivity to sorafenib treatment.

Inactivation of Wnt signaling by a human antibody that recognizes the heparan sulfate chains of glypican-3 for liver cancer therapy

Wnt signaling is important for cancer pathogenesis and is often up-regulated in hepatocellular carcinoma (HCC). Heparan sulfate proteoglycans (HSPGs) function as coreceptors or modulators of Wnt activation. Glypican-3 (GPC3) is an HSPG that is highly expressed in HCC, where it can attract Wnt proteins to the cell surface and promote cell proliferation. Thus, GPC3 has emerged as a candidate therapeutic target in liver cancer. While monoclonal antibodies to GPC3 are currently being evaluated in preclinical and clinical studies, none have shown an effect on Wnt signaling. Here, we first document the expression of Wnt3a, multiple Wnt receptors, and GPC3 in several HCC cell lines, and demonstrate that GPC3 enhanced the activity of Wnt3a/β-catenin signaling in these cells. Then we report the identification of HS20, a human monoclonal antibody against GPC3, which preferentially recognized the heparan sulfate chains of GPC3, both the sulfated and nonsulfated portions. HS20 disrupted the interaction of Wnt3a and GPC3 and blocked Wnt3a/β-catenin signaling. Moreover, HS20 inhibited Wnt3a-dependent cell proliferation in vitro and HCC xenograft growth in nude mice. In addition, HS20 had no detectable undesired toxicity in mice. Taken together, our results show that a monoclonal antibody primarily targeting the heparin sulfate chains of GPC3 inhibited Wnt/β-catenin signaling in HCC cells and had potent antitumor activity in vivo.

CONCLUSION

An antibody directed against the heparan sulfate of a proteoglycan shows efficacy in blocking Wnt signaling and HCC growth, suggesting a novel strategy for liver cancer therapy.

Targeting the Wnt/β-catenin signaling pathway in liver cancer stem cells and hepatocellular carcinoma cell lines with FH535

Activation of the Wnt/β-catenin pathway has been observed in at least 1/3 of hepatocellular carcinomas (HCC), and a significant number of these have mutations in the β-catenin gene. Therefore, effective inhibition of this pathway could provide a novel method to treat HCC. The purposed of this study was to determine whether FH535, which was previously shown to block the β-catenin pathway, could inhibit β-catenin activation of target genes and inhibit proliferation of Liver Cancer Stem Cells (LCSC) and HCC cell lines. Using β-catenin responsive reporter genes, our data indicates that FH535 can inhibit target gene activation by endogenous and exogenously expressed β-catenin, including the constitutively active form of β-catenin that contains a Serine37Alanine mutation. Our data also indicate that proliferation of LCSC and HCC lines is inhibited by FH535 in a dose-dependent manner, and that this correlates with a decrease in the percentage of cells in S phase. Finally, we also show that expression of two well-characterized targets of β-catenin, Cyclin D1 and Survivin, is reduced by FH535. Taken together, this data indicates that FH535 has potential therapeutic value in treatment of liver cancer. Importantly, these results suggest that this therapy may be effective at several levels by targeting both HCC and LCSC.

The role of Wnt signaling pathway in carcinogenesis and implications for anticancer therapeutics

The Wnt proteins are a family of 19 secreted glycoproteins that occupy crucial roles in the regulation of processes such as cell survival, proliferation, migration and polarity, cell fate specification, body axis patterning and self-renewal in stem cells. The canonical pathway has been implicated in a variety of cancers. As such, it is only fair to conclude that therapies targeting the Wnt pathway may play an essential role in the future of anticancer therapeutics, both alone or in conjunction with traditional therapies.

Loss of exon 4 in a human T-cell factor-4 isoform promotes hepatic tumourigenicity

BACKGROUND

T-cell factor (TCF) proteins represent key transcription factors that activate Wnt/β-catenin signalling. We have reported that a pair of TCF-4 isoforms (TCF-4C and TCF-4D) exhibit differential TCF transcriptional activity in hepatocellular carcinoma (HCC) cells, although their structure differs by only the presence (TCF-4D) or absence (TCF-4C) of exon 4.

AIM

To demonstrate a regulatory role of exon 4 in HCC development.

METHODS

TCF-4C and TCF-4D expression profiles were examined in 27 pairs of human HCC and adjacent liver tissues. The functional role of the TCF-4 isoforms was evaluated in OUMS-29 (an immortalized hepatocyte-derived) and HAK-1A (a well-differentiated HCC) cell lines using stable clones overexpressing the TCF-4 isoforms.

RESULTS

TCF-4C was significantly upregulated in HCC tissues compared with corresponding peritumour and normal liver tissues; in contrast, there was no difference in TCF-4D expression. TCF-4C clones derived from both cell lines exhibited increased TCF activity, Wnt-responsive target genes, cell proliferation, cell cycle progression and resistance to chemotherapeutic drugs compared with TCF-4D clones. Capability of cell migration and colony formation was significantly higher in TCF-4C than TCF-4D clones. In a nude mice xenograft model, the HAK-1A-derived TCF-4C clone rapidly developed tumours compared with the TCF-4D clone. TCF-4C clone-derived tumours exhibited upregulation of Wnt-responsive target genes compared with the slow developing and small TCF-4D-derived tumours.

CONCLUSION

These results demonstrate that the TCF-4C isoform lacking exon 4 is associated with a malignant phenotype compared with the exon 4-harbouring TCF-4D isoform, indicating that exon 4 of TCF-4 plays a prominent role in HCC development.

Pomegranate Bioactive Constituents Suppress Cell Proliferation and Induce Apoptosis in an Experimental Model of Hepatocellular Carcinoma: Role of Wnt/ β -Catenin Signaling Pathway

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide, and chemoprevention represents a viable approach in lowering the mortality of this disease. Pomegranate fruit, an abundant source of anti-inflammatory phytochemicals, is gaining tremendous attention for its wide-spectrum health benefits. We previously reported that a characterized pomegranate emulsion (PE) prevents diethylnitrosamine (DENA)-induced rat hepatocarcinogenesis though inhibition of nuclear factor-kappaB (NF- κ B). Since NF- κ B concurrently induces Wnt/ β -catenin signaling implicated in cell proliferation, cell survival, and apoptosis evasion, we examined antiproliferative, apoptosis-inducing and Wnt/ β -catenin signaling-modulatory mechanisms of PE during DENA rat hepatocarcinogenesis. PE (1 or 10 g/kg) was administered 4 weeks before and 18 weeks following DENA exposure. There was a significant increase in hepatic proliferation (proliferating cell nuclear antigen) and alteration in cell cycle progression (cyclin D1) due to DENA treatment, and PE dose dependently reversed these effects. PE substantially induced apoptosis by upregulating proapoptotic protein Bax and downregulating antiapoptotic protein Bcl-2. PE dose dependently reduced hepatic β -catenin and augmented glycogen synthase kinase-3 β expression. Our study provides evidence that pomegranate phytochemicals exert chemoprevention of hepatic cancer through antiproliferative and proapoptotic mechanisms by modulating Wnt/ β -catenin signaling. PE, thus, targets two interconnected molecular circuits (canonical NF- κ B and Wnt/ β -catenin pathways) to exert chemoprevention of HCC.

Functional consequences of WNT3/Frizzled7-mediated signaling in non-transformed hepatic cells

We have previously demonstrated that WNT3 and Frizzled7 (FZD7) expression levelswere upregulated in hepatocellular carcinoma (HCC) and that they directly interact to activate the canonical Wnt/β–catenin pathway in HCC cell lines. In this study, we investigated the functional consequences of WNT3 and FZD7 expression levels in non-transformed hepatic cells to address the question of whether WNT3/FZD7-mediated signal transduction could be involved in cellular transformation. After stable transfection of WNT3 and FZD7, the activation of the Wnt/β–catenin pathway was confirmed by western blot, immunostaining and quantitative real-time reverse transcriptase–PCR (qRT–PCR) analysis in two non-transformed hepatocyte-derived cell lines. In vitro characteristics of the malignant phenotype were measured, including cell proliferation, migration, invasion and anchorage-independent growth in soft agar. Stable expression of WNT3 and FZD7 in the two cell lines led to cellular accumulation of β-catenin and expression of downstream target genes activated by this pathway. In the stable WNT3/FZD7-expressing clones, hepatic cell proliferation, migration, invasion as well as soft agar colony formation were enhanced compared with the non-transformed control cells. The epithelial–mesenchymal transition (EMT) factors, Twist, Snail and Vimentin, were increased in cells expressing WNT3 and FZD7. However, the WNT3/FZD7-expressing cells did not form tumors in vivo. We conclude that activation of the WNT3/FZD7 canonical pathway has a role in the early stages of hepatocarcinogenesis by promoting the acquisition of a malignant phenotype with features of EMT.

Unraveling 50-Year-Old Clues Linking Neurodegeneration and Cancer to Cycad Toxins: Are microRNAs Common Mediators?

Recognition of overlapping molecular signaling activated by a chemical trigger of cancer and neurodegeneration is new, but the path to this discovery has been long and potholed. Six conferences (1962–1972) examined the puzzling neurotoxic and carcinogenic properties of a then-novel toxin [cycasin: methylazoxymethanol (MAM)-β-d-glucoside] in cycad plants used traditionally for food and medicine on Guam where a complex neurodegenerative disease plagued the indigenous population. Affected families showed combinations of amyotrophic lateral sclerosis (ALS), parkinsonism (P), and/or a dementia (D) akin to Alzheimer’s disease (AD). Modernization saw declining disease rates on Guam and remarkable changes in clinical phenotype (ALS was replaced by P-D and then by D) and in two genetically distinct ALS-PDC-affected populations (Kii-Japan, West Papua-Indonesia) that used cycad seed medicinally. MAM forms DNA lesions – repaired by O⁶-methylguanine methyltransferase (MGMT) – that perturb mouse brain development and induce malignant tumors in peripheral organs. The brains of young adult MGMT-deficient mice given a single dose of MAM show DNA lesion-linked changes in cell-signaling pathways associated with miRNA-1, which is implicated in colon, liver, and prostate cancers, and in neurological disease, notably AD. MAM is metabolized to formaldehyde, a human carcinogen. Formaldehyde-responsive miRNAs predicted to modulate MAM-associated genes in the brains of MGMT-deficient mice include miR-17-5p and miR-18d, which regulate genes involved in tumor suppression, DNA repair, amyloid deposition, and neurotransmission. These findings marry cycad-associated ALS-PDC with colon, liver, and prostate cancer; they also add to evidence linking changes in microRNA status both to ALS, AD, and parkinsonism, and to cancer initiation and progression.