AXIN1 mutations in hepatocellular carcinomas, and growth suppression in cancer cells by virus-mediated transfer of AXIN1

β-Catenin Signaling and Roles in Liver Homeostasis, Injury, and Tumorigenesis

β-catenin (encoded by CTNNB1) is a subunit of the cell surface cadherin protein complex that acts as an intracellular signal transducer in the WNT signaling pathway; alterations in its activity have been associated with the development of hepatocellular carcinoma and other liver diseases. Other than WNT, additional signaling pathways also can converge at β-catenin. β-catenin also interacts with transcription factors such as T-cell factor, forkhead box protein O, and hypoxia inducible factor 1α to regulate the expression of target genes. We discuss the role of β-catenin in metabolic zonation of the adult liver. β-catenin also regulates the expression of genes that control metabolism of glucose, nutrients, and xenobiotics; alterations in its activity may contribute to the pathogenesis of nonalcoholic steatohepatitis. Alterations in β-catenin signaling may lead to activation of hepatic stellate cells, which is required for fibrosis. Many hepatic tumors such as hepatocellular adenomas, hepatocellular cancers, and hepatoblastomas have mutations in CTNNB1 that result in constitutive activation of β-catenin, so this molecule could be a therapeutic target. We discuss how alterations in β-catenin activity contribute to liver disease and how these might be used in diagnosis and prognosis, as well as in the development of therapeutics.

Molecular signalling in hepatocellular carcinoma: Role of and crosstalk among WNT/ß-catenin, Sonic Hedgehog, Notch and Dickkopf-1

Hepatocellular carcinoma is the sixth most common cancer worldwide. In the majority of cases, there is evidence of existing chronic liver disease from a variety of causes including viral hepatitis B and C, alcoholic liver disease and nonalcoholic steatohepatitis. Identification of the signalling pathways used by hepatocellular carcinoma cells to proliferate, invade or metastasize is of paramount importance in the discovery and implementation of successfully targeted therapies. Activation of Wnt/β-catenin, Notch and Hedgehog pathways play a critical role in regulating liver cell proliferation during development and in controlling crucial functions of the adult liver in the initiation and progression of human cancers. β-catenin was identified as a protein interacting with the cell adhesion molecule E-cadherin at the cell-cell junction, and has been shown to be one of the most important mediators of the Wnt signalling pathway in tumourigenesis. Investigations into the role of Dikkopf-1 in hepatocellular carcinoma have demonstrated controversial results, with a decreased expression of Dickkopf-1 and soluble frizzled-related protein in various cancers on one hand, and as a possible negative prognostic indicator of hepatocellular carcinoma on the other. In the present review, the authors focus on the Wnt⁄β-catenin, Notch and Sonic Hedgehog pathways, and their interaction with Dikkopf-1 in hepatocellular carcinoma.

Coordinated action of Axin1 and Axin2 suppresses β-catenin to regulate muscle stem cell function

The resident stem cells of skeletal muscle are satellite cells, which are regulated by both canonical and non-canonical Wnt pathways. Canonical Wnt signalling promotes differentiation, and is controlled at many levels, including via Axin1 and Axin2-mediated β-catenin degradation. Axin1 and Axin2 are thought equivalent suppressors of canonical Wnt signalling, although Axin2 is also a Wnt target gene. We show that Axin1 expression was higher in proliferating satellite cells, while Axin2 was up-regulated during differentiation. siRNA-mediated Axin1 knockdown changed cell morphology, suppressed proliferation and promoted myogenic differentiation. Simultaneous knockdown of both Axin1 and β-catenin rescued proliferation and partially, premature differentiation. Surprisingly, retroviral-mediated overexpression of Axin2 was unable to compensate for knockdown of Axin1 in satellite cells, indicating that Axin1 and Axin2 are not fully redundant. Isolated satellite cells from Axin2-null mice also had no major phenotype. However, siRNA-mediated knockdown of Axin1 in Axin2-null cells strongly inhibited proliferation, while inducing differentiation, clear nuclear localisation of β-catenin, up-regulation of canonical Wnt target genes (Axin2, Lef1, Tcf4, Pitx2c and Lgr5) and activation of a TCF reporter construct. Again, concomitant knockdown of Axin1 and β-catenin in Axin2-null satellite cells rescued morphology and proliferation, but only partially prevented precocious differentiation. Thus, Axin1 and Axin2 do not have equivalent functions in satellite cells, but are both involved in repression of Wnt/β-catenin signalling to maintain proliferation and contribute to controlling timely myogenic differentiation.

Cytotoxic activity of rearranged drimane meroterpenoids against colon cancer cells via down-regulation of β-catenin expression

Colorectal cancer has emerged as a major cause of death in Western countries. Down-regulation of β-catenin expression has been considered a promising approach for cytotoxic drug formulation. Eight 4,9-friedodrimane-type sesquiterpenoids (1-8) were acquired using the oxidative potential of Verongula rigida on bioactive metabolites from two Smenospongia sponges. Compounds 3 and 4 contain a 2,2-dimethylbenzo[d]oxazol-6(2H)-one moiety as their substituted heterocyclic residues, which is unprecedented in such types of meroterpenoids. Gauge-invariant atomic orbital NMR chemical shift calculations were employed to investigate stereochemical details with support of the application of advanced statistics such as CP3 and DP4. Compounds 2 and 8 and the mixture of 3 and 4 suppressed β-catenin response transcription (CRT) via degrading β-catenin and exhibited cytotoxic activity on colon cancer cells, implying that their anti-CRT potential is, at least in part, one of their underlying antineoplastic mechanisms.

Differentiation-inducing factor-3 inhibits intestinal tumor growth in vitro and in vivo

Differentiation-inducing factor-1 (DIF-1) produced by Dictyostelium discoideum strongly inhibits the proliferation of various types of cancer cells by suppression of the Wnt/β-catenin signal transduction pathway. In the present study, we examined the effect of differentiation-inducing factor-3 (DIF-3), a monochlorinated metabolite of DIF-1 that is also produced by D. discoideum, on human colon cancer cell lines HCT-116 and DLD-1. DIF-3 strongly inhibited cell proliferation by arresting the cell cycle at the G0/G1 phase. DIF-3 reduced the expression levels of cyclin D1 and c-Myc by facilitating their degradation via activation of GSK-3β in a time and dose-dependent manner. In addition, DIF-3 suppressed the expression of T-cell factor 7-like 2, a key transcription factor in the Wnt/β-catenin signaling pathway, thereby reducing the mRNA levels of cyclin D1 and c-Myc. Subsequently, we examined the in vivo effects of DIF-3 in Mutyh(-/-) mice with oxidative stress-induced intestinal cancers. Repeated oral administration of DIF-3 markedly reduced the number and size of cancers at a level comparable to that of DIF-1. These data suggest that DIF-3 inhibits intestinal cancer cell proliferation in vitro and in vivo, probably by mechanisms similar to those identified in DIF-1 actions, and that DIF-3 may be a potential novel anti-cancer agent.

Global increase of p16INK4a in APC-deficient mouse liver drives clonal growth of p16INK4a-negative tumors

Reduction of β-catenin (CTNNB1) destroying complex components, for example, adenomatous polyposis coli (APC), induces β-catenin signaling and subsequently triggers activation of genes involved in proliferation and tumorigenesis. Though diminished expression of APC has organ-specific and threshold-dependent influence on the development of liver tumors in mice, the molecular basis is poorly understood. Therefore, a detailed investigation was conducted to determine the underlying mechanism in the development of liver tumors under reduced APC levels. Mouse liver at different developmental stages was analyzed in terms of β-catenin target genes including Cyp2e1, Glul, and Ihh using real-time RT-PCR, reporter gene assays, and immunohistologic methods with consideration of liver zonation. Data from human livers with mutations in APC derived from patients with familial adenomatous polyposis (FAP) were also included. Hepatocyte senescence was investigated by determining p16(INK4a) expression level, presence of senescence-associated β-galactosidase activity, and assessing ploidy. A β-catenin activation of hepatocytes does not always result in β-catenin positive but unexpectedly also in mixed and β-catenin-negative tumors. In summary, a senescence-inducing program was found in hepatocytes with increased β-catenin levels and a positive selection of hepatocytes lacking p16(INK4a), by epigenetic silencing, drives the development of liver tumors in mice with reduced APC expression (Apc(580S) mice). The lack of p16(INK4a) was also detected in liver tumors of mice with triggers other than APC reduction.

IMPLICATIONS

Epigenetic silencing of p16(Ink4a) in selected liver cells bypassing senescence is a general principle for development of liver tumors with β-catenin involvement in mice independent of the initial stimulus.

Kaposi's sarcoma-associated herpesvirus G-protein coupled receptor activates the canonical Wnt/β-catenin signaling pathway

Background

KSHV is a tumorigenic γ-herpesvirus that has been identified as the etiologic agent of Kaposi’s sarcoma (KS), a multifocal highly vascularized neoplasm that is the most common malignancy associated with acquired immunodeficiency syndrome (AIDS). The virus encodes a constitutively active chemokine receptor homologue, vGPCR that possesses potent angiogenic and tumorigenic properties, and is critical for KSHV pathobiology. To date, a number of signaling pathways have been identified as key in mediating vGPCR oncogenic potential.

Findings

In this study, we identify a novel pathway, the Wnt/β-catenin pathway, which is dysregulated by vGPCR expression in endothelial cells. Expression of vGPCR in endothelial cells enhances the nuclear accumulation of β-catenin, that correlates with an increase in β-catenin transcriptional activity. Activation of β-catenin signaling by vGPCR is dependent on the PI3K/Akt pathway, as treatment of vGPCR-expressing cells with a pharmacological inhibitor of PI3K, leads to a decreased activation of a β-catenin-driven reporter, a significant decrease in expression of β-catenin target genes, and reduced endothelial tube formation.

Conclusions

Given the critical role of Wnt/β-catenin signaling in angiogenesis and tumorigenesis, the findings from this study suggest a novel mechanism in KSHV-induced malignancies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-014-0218-8) contains supplementary material, which is available to authorized users.

Stem cells in gastrointestinal cancers: The road less travelled

Cancer stem cells (CSC) are thought to be malignant cells that have the capacity to initiate and maintain tumor growth and survival. Studies have described CSC in various gastrointestinal neoplasms such as colon, pancreas and liver and gastroesophageal tumors. The mechanism by which CSC develop remains unclear. Several studies have explored the role of dysregulation of the Wnt/β-catenin, transformation growth factor-beta and hedhog pathways in generation of CSC. In this review, we discuss the various molecular abnormalities that may be related to formation of CSC in gastrointestinal malignancies, strategies to identify CSC and therapeutic strategies that are based on these concepts. Identification and targeting CSC is an intriguing area and may provide a new therapeutic option for patients with cancer including gastrointestinal malignancies. Although great progress has been made, many issues need to be addressed. Precise targeting of CSC will require precise isolation and characterization of those cells. This field is also evolving but further research is needed to identify markers that are specific for CSC. Although the application of this field has not entered the clinic yet, there continues to be significant optimism about its potential utility in overcoming cancer resistance and curing patients with cancer.

MicroRNA-93 suppress colorectal cancer development via Wnt/β-catenin pathway downregulating

MicroRNA-93 (miR-93) is involved in several carcinoma progressions. It has been reported that miR-93 acts as a promoter or suppressor in different tumors. However, till now, the role of miR-93 in colon cancer is unclear. Herein, we have found that expression of miR-93 was lower in human colon cancer tissue and colorectal carcinoma cell lines compared with normal colon mucosa. Forced expression of miR-93 in colon cancer cells inhibits colon cancer invasion, migration, and proliferation. Furthermore, miR-93 may downregulate the Wnt/β-catenin pathway, which was confirmed by measuring the expression level of the β-catenin, axin, c-Myc, and cyclin-D1 in this pathway. Mothers against decapentaplegic homolog 7 (Smad7), as an essential molecular protein for nuclear accumulation of β-catenin in the canonical Wnt signaling pathway, is predicted as a putative target gene of miR-93 by the silico method and demonstrated that it may be suppressed by targeting its 3'UTR. These findings showed that miR-93 suppresses colorectal cancer development via downregulating Wnt/β-catenin, at least in part, by targeting Smad7. This study revealed that miR-93 is an important negative regulator in colon cancer and suggested that miR-93 may serve as a novel therapeutic agent that offers benefits for colon cancer treatment.

Association between polymorphisms in AXIN1 gene and atrial septal defect

CONTEXT

AXIN1 is a central component of Wnt signalling pathway which is essential for embryonic development.

OBJECTIVE

To investigate whether polymorphisms of AXIN1 contribute to ASD susceptibility.

MATERIALS AND METHODS

Three tag SNPs (rs12921862, rs370681 and rs1805105) in AXIN1 were genotyped in 208 ASD patients and 302 healthy controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in a Chinese population.

RESULTS

Significantly increased ASD risk was observed to be associated with the A allele of rs12921862 (p < 0.0001, OR = 3.096, 95% CI = 2.037-4.717). Increased ASD risk was observed to be associated with rs370681 in a codominant (p = 0.043, OR = 1.52, 95% CI = 1.04-2.22) and overdominant model (p = 0.016, OR = 1.57, 95% CI = 1.08-2.27).

CONCLUSION

rs12921862 and rs370681 may contribute to ASD susceptibility.

WNT signaling: an emerging mediator of cancer cell metabolism?

WNT signaling was discovered in tumor models and has been recognized as a regulator of cancer development and progression for over 3 decades. Recent work has highlighted a critical role for WNT signaling in the metabolic homeostasis of mammals, where its misregulation has been heavily implicated in diabetes. While the majority of WNT metabolism research has focused on nontransformed tissues, the role of WNT in cancer metabolism remains underinvestigated. Cancer is also a metabolic disease where oncogenic signaling pathways regulate energy production and macromolecular synthesis to fuel rapidly proliferating tumors. This review highlights the emerging evidence for WNT signaling in the reprogramming of cancer cell metabolism and examines the role of these signaling pathways as mediators of tumor bioenergetics.

New insights in hepatocellular carcinoma: from bench to bedside

Hepatocarcinogenesis is a multistep process involving different genetic alterations that ultimately lead to malignant transformation of the hepatocyte. The liver is one of the main targets for different metastatic foci, but it represents an important and frequent locus of degeneration in the course of chronic disease. In fact, Hepatocellular carcinoma (HCC) represents the outcome of the natural history of chronic liver diseases, from the condition of fibrosis, to cirrhosis and finally to cancer. HCC is the sixth most common cancer in the world, some 630,000 new cases being diagnosed each year. Furthermore, about the 80% of people with HCC, have seen their clinical history developing from fibrosis, to cirrhosis and finally to cancer. The three main causes of HCC development are represented by HBV, HCV infection and alcoholism. Moreover, metabolic disease [starting from Non Alcoholic Fatty Liver Disease (NAFLD), Non Alcoholic Steatohepatitis (NASH)] and, with reduced frequency, some autoimmune disease may lead to HCC development. An additional rare cause of carcinogenetic degeneration of the liver, especially developed in African and Asian Countries, is represented by aflatoxin B1. The mechanisms by which these etiologic factors may induce HCC development involve a wide range of pathway and molecules, currently under investigation. In summary, the hepatocarcionogenesis results from a multifactorial process leading to the common condition of genetic changes in mature hepatocytes mainly characterized by uncontrolled proliferation and cell death. Advances in understanding the mechanism of action are fundamental for the development of new potential therapies and results primarily from the association of the research activities coming from basic and clinical science. This review article analyzes the current models used in basic research to investigate HCC activity, and the advances obtained from a basic and clinical point of view.

Potential prognostic, diagnostic and therapeutic markers for human gastric cancer

The high incidence of gastric cancer (GC) and its consequent mortality rate severely threaten human health. GC is frequently not diagnosed until a relatively advanced stage. Surgery is the only potentially curative treatment. Thus, early screening and diagnosis are critical for improving prognoses in patients with GC. Gastroscopy with biopsy is an appropriate method capable of aiding the diagnosis of specific early GC tumor types; however, the stress caused by this method together with it being excessively expensive makes it difficult to use it as a routine method for screening for GC on a population basis. The currently used tumor marker assays for detecting GC are simple and rapid, but their use is limited by their low sensitivity and specificity. In recent years, several markers have been identified and tested for their clinical relevance in the management of GC. Here, we review the serum-based tumor markers for GC and their clinical significance, focusing on discoveries from microarray/proteomics research. We also review tissue-based GC tumor markers and their clinical application, focusing on discoveries from immunohistochemical research. This review provides a brief description of various tumor markers for the purposes of diagnosis, prognosis and therapeutics, and we include markers already in clinical practice and various forthcoming biomarkers.

Silencing of the glypican-3 gene affects the biological behavior of human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in the world. The gene glypican-3 (GPC3) is reported to be a potential therapeutic target for HCC. In this study, we use RNA interference with lentiviral vectors to explore the effect of GPC3 silencing on the biological behavior of HCC cells and the potential role of the GPC3 protein in the activation of epithelial-mesenchymal transition (EMT), which relates to HCC cell invasion and migration. Our data suggest that GPC3 silencing leads to a decrease in HCC cell proliferation and to an increase in apoptosis. We demonstrated that GPC3 silencing regulates cell invasion and migration, most probably through the activation of the EMT cellular program. In conclusion, GPC3 is associated with the HCC cell biological behavior, while the relationship between GPC3 and EMT in tumorigenesis of HCC deserves future investigation.

AXIN1 and AXIN2 variants in gastrointestinal cancers

Mutations in the APC (adenomatous polyposis coli) gene, which encodes a multi-functional protein with a well-defined role in the canonical Wnt pathway, underlie familial adenomatous polypsosis, a rare, inherited form of colorectal cancer (CRC) and contribute to the majority of sporadic CRCs. However, not all sporadic and familial CRCs can be explained by mutations in APC or other genes with well-established roles in CRC. The AXIN1 and AXIN2 proteins function in the canonical Wnt pathway, and AXIN1/2 alterations have been proposed as key defects in some cancers. Here, we review AXIN1 and AXIN2 sequence alterations reported in gastrointestinal cancers, with the goal of vetting the evidence that some of the variants may have key functional roles in cancer development.

Characterization of two unique α-globin gene cluster deletions causing α-thalassemia in Israeli Arabs

The molecular basis of α-thalassemia (α-thal) is complex. The use of multiplex ligation-dependent probe amplification (MLPA) has offered the possibility of identifying more gene deletions causing α-thal. Our objective was to determine the molecular basis of two patients with Hb H (β4) disease. By using MLPA in combination with comparative genomic hybridization (CGH) we identified two novel α-globin gene cluster deletions: a 30 kb deletion (patient 1) we refer to as - -(JAL) and a large 216 kb deletion (patient 2) we refer to as - -(LOD). Patient 1 was a compound heterozygote for - -(JAL) and -α(3.7) (rightward deletion). Twelve family members of patient 1 carrying the - -(JAL) deletion were available for evaluation: five with - -(JAL)/-α(3.7), four with - -(JAL)/α(Hph I)α and three with - -(JAL)/αα. Their clinical picture of compound heterozygosity was compatible with moderate Hb H disease. In patient 2 (- -(LOD)/-α(3.7)), no additional symptoms were present despite the heterozygous deletion of seven known genes, three non coding RNAs (ncRNAs), four unknown genes and two pseudo genes. Further analysis of more patients with α-thal deletions will have implications for genetic counseling and appropriate therapy.

MicroRNAs in liver cancer: a model for investigating pathogenesis and novel therapeutic approaches

MicroRNAs (miRNAs) constitute a large class of short RNAs (e.g., 20-24 nucleotides in length), whose main function is to posttranscriptionally regulate the expression of protein-coding genes. Their importance in tumorigenesis has been demonstrated over the past decade, and correspondingly, they have emerged as potential therapeutic molecules and targets. Liver cancer is one of the most common neoplastic diseases worldwide, and it currently has a poor prognosis owing to largely ineffective therapeutic options. Liver cancer is also an excellent model for testing miRNA-based therapy approaches as it can be easily targeted with the systemic delivery of oligonucleotides. In recent years, the role of miRNAs in hepatocellular carcinoma (HCC) has been established with molecular studies and the development of animal models. These studies have also provided the basis for evaluating the therapeutic potential of miRNAs, or anti-miRNAs. In general, the safety of miRNAs has been proven and antitumor activity has been observed. Moreover, because of the absence or presence of mild side effects, the prophylactic use of miRNA-based approaches may be foreseen.

Methylation profiles reveal distinct subgroup of hepatocellular carcinoma patients with poor prognosis

Hepatocellular Carcinoma (HCC) is one of the leading causes of cancer-associated mortality worldwide. However, the role of epigenetic changes such as aberrant DNA methylation in hepatocarcinogenesis remains largely unclear. In this study, we examined the methylation profiles of 59 HCC patients. Using consensus hierarchical clustering with feature selection, we identified three tumor subgroups based on their methylation profiles and correlated these subgroups with clinicopathological parameters. Interestingly, one tumor subgroup is different from the other 2 subgroups and the methylation profile of this subgroup is the most distinctly different from the non-tumorous liver tissues. Significantly, this subgroup of patients was found to be associated with poor overall as well as disease-free survival. To further understand the pathways modulated by the deregulation of methylation in HCC patients, we integrated data from both the methylation as well as the gene expression profiles of these 59 HCC patients. In these patients, while 4416 CpG sites were differentially methylated between the tumors compared to the adjacent non-tumorous tissues, only 536 of these CpG sites were associated with differences in the expression of their associated genes. Pathway analysis revealed that forty-four percent of the most significant upstream regulators of these 536 genes were involved in inflammation-related NFκB pathway. These data suggest that inflammation via the NFκB pathway play an important role in modulating gene expression of HCC patients through methylation. Overall, our analysis provides an understanding on aberrant methylation profile in HCC patients.

β-catenin in oral cancer: an update on current knowledge

β-Catenin is a multiple function protein. These functions derive from its interactions with other cell proteins, both on the cell membrane, in the cytoplasm and in the nucleus. β-Catenin forms a complex with the adhesion molecule E-cadherin, promoting cell-cell adhesion and thereby preventing the cell dissociation that is required for cancer invasion and progression mechanisms. There is also a dynamic pool of cytoplasmic β-catenin that serves as connection between the extracellular microenvironment and the nucleus. Cytoplasmic β-catenin acts as a transcription factor for the nucleus in the canonical Wnt pathway, activating the transcription of various genes. Structural or functional alterations of β-catenin can promote cancer progression. This review addresses the current knowledge on the implications of β-catenin in the development of oral cancer.

Identification of drivers from cancer genome diversity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers with a dismal outcome. The complicated molecular pathogenesis of HCC caused by tumor heterogeneity makes it difficult to identify druggable targets useful for treating HCC patients. One approach that has a potential for the improvement of patient prognosis is the identification of cancer driver genes that play a critical role in the development of HCC. Recent technological advances of high-throughput methods, such as gene expression profiles, DNA copy number alterations and somatic mutations, have expanded our understanding of the comprehensive genetic profiles of HCC. Integrative analysis of these omics profiles enables us to classify the molecular subgroups of HCC patients. As each subgroup classified according to genetic profiles has different clinical features, such as recurrence rate and prognosis, the tumor subclassification tools are useful in clinical practice. Furthermore, a global genetic analysis, including genome-wide RNAi functional screening, makes it possible to identify cancer vulnerable genes. Identification of common cancer driver genes in HCC leads to the development of an effective molecular target therapy.

Exploration of liver cancer genomes

Liver cancer is the third leading cause of cancer-related death worldwide. Advances in sequencing technologies have enabled the examination of liver cancer genomes at high resolution; somatic mutations, structural alterations, HBV integration, RNA editing and retrotransposon changes have been comprehensively identified. Furthermore, integrated analyses of trans-omics data (genome, transcriptome and methylome data) have identified multiple critical genes and pathways implicated in hepatocarcinogenesis. These analyses have uncovered potential therapeutic targets, including growth factor signalling, WNT signalling, the NFE2L2-mediated oxidative pathway and chromatin modifying factors, and paved the way for new molecular classifications for clinical application. The aetiological factors associated with liver cancer are well understood; however, their effects on the accumulation of somatic changes and the influence of ethnic variation in risk factors still remain unknown. The international collaborations of cancer genome sequencing projects are expected to contribute to an improved understanding of risk evaluation, diagnosis and therapy for this cancer.

Human Sarcoma growth is sensitive to small-molecule mediated AXIN stabilization

Sarcomas are mesenchymal tumors showing high molecular heterogeneity, reflected at the histological level by the existence of more than fifty different subtypes. Genetic and epigenetic evidences link aberrant activation of the Wnt signaling to growth and progression of human sarcomas. This phenomenon, mainly accomplished by autocrine loop activity, is sustained by gene amplification, over-expression of Wnt ligands and co-receptors or epigenetic silencing of endogenous Wnt antagonists. We previously showed that pharmacological inhibition of Wnt signaling mediated by Axin stabilization produced in vitro and in vivo antitumor activity in glioblastoma tumors. Here, we report that targeting different sarcoma cell lines with the Wnt inhibitor/Axin stabilizer SEN461 produces a less transformed phenotype, as supported by modulation of anchorage-independent growth in vitro. At the molecular level, SEN461 treatment enhanced the stability of the scaffold protein Axin1, a key negative regulator of the Wnt signaling with tumor suppressor function, resulting in downstream effects coherent with inhibition of canonical Wnt signaling. Genetic phenocopy of small molecule Axin stabilization, through Axin1 over-expression, coherently resulted in strong impairment of soft-agar growth. Importantly, sarcoma growth inhibition through pharmacological Axin stabilization was also observed in a xenograft model in vivo in female CD-1 nude mice. Our findings suggest the usefulness of Wnt inhibitors with Axin stabilization activity as a potentialyl clinical relevant strategy for certain types of sarcomas.

Dysregulated expression of dickkopfs for potential detection of hepatocellular carcinoma

The prognosis for hepatocellular carcinoma (HCC) remains dismal due to the lack of diagnostic markers for early detection. This review will discuss the clinical potential of the dickkopf (DKK) family members as diagnostic and/or prognostic markers for HCC. In comparison to serum α-fetoprotein (AFP) level, which remains the gold standard for HCC diagnosis, high serum DKK1 levels have higher diagnostic value for HCC, especially for AFP-negative HCC, and can distinguish HCC from non-malignant chronic liver diseases. Additionally, the combination of serum DKK1 and AFP levels enhances diagnostic accuracy for HCC compared to serum DKK1 or AFP levels alone. Although DKK1 offers potential for its use in HCC diagnosis this review will discuss the challenges facing DKK1 and also shed some light on recent developments on the remaining DKK family members: DKK2, DKK3 and DKK4.

β-Catenin knockdown in liver tumor cells by a cell permeable gamma guanidine-based peptide nucleic acid

Hepatocellular cancer (HCC) is the third cause of death by cancer worldwide. In the current study we target β- catenin, an oncogene mutated and constitutively active in 20-30% of HCCs, via a novel, cell permeable gamma guanidine-based peptide nucleic acid (γGPNA) antisense oligonucleotide designed against either the transcription or the translation start site of the human β-catenin gene. Using TOPflash, a luciferase reporter assay, we show that γGPNA targeting the transcription start site showed more robust activity against β-catenin activity in liver tumor cells that harbor β-catenin gene mutations (HepG2 & Snu-449). We identified concomitant suppression of β-catenin expression and of various Wnt targets including glutamine synthetase (GS) and cyclin-D1. Concurrently, γGPNA treatment reduced proliferation, survival and viability of HCC cells. Intriguingly, an angiogenesis quantitative Real-Time-PCR array identified decreased expression of several pro-angiogenic secreted factors such as EphrinA1, FGF-2, and VEGF-A upon β-catenin inhibition in liver tumor cells. Conversely, transfection of stabilized-β-catenin mutants enhanced the expression of angiogenic factors like VEGF-A. Conditioned media from HepG2 cells treated with β-catenin but not the mismatch γGPNA significantly diminished spheroid and tubule formation by SK-Hep1 cells, an HCC-associated endothelial cell line. Thus, we report a novel class of cell permeable and efficacious γGPNAs that effectively targets β-catenin, a known oncogene in the liver. Our study also identifies a novel role of β-catenin in liver tumor angiogenesis through paracrine mechanisms in addition to its roles in proliferation, survival, metabolism and cancer stem cell biology, thus further strengthening its effectiveness as a therapeutic target in HCC.

DIF-1 inhibits tumor growth in vivo reducing phosphorylation of GSK-3β and expressions of cyclin D1 and TCF7L2 in cancer model mice

We reported that differentiation-inducing factor-1 (DIF-1), synthesized by Dictyostelium discoideum, inhibited proliferation of various tumor cell lines in vitro by suppressing the Wnt/β-catenin signaling pathway. However, it remained unexplored whether DIF-1 also inhibits tumor growth in vivo. In the present study, therefore, we examined in-vivo effects of DIF-1 using three cancer models: Mutyh-deficient mice with oxidative stress-induced intestinal tumors and nude mice xenografted with the human colon cancer cell line HCT-116 and cervical cancer cell line HeLa. In exploration for an appropriate route of administration, we found that orally administered DIF-1 was absorbed through the digestive tract to elevate its blood concentration to levels enough to suppress tumor cell proliferation. Repeated oral administration of DIF-1 markedly reduced the number and size of intestinal tumors that developed in Mutyh-deficient mice, reducing the phosphorylation level of GSK-3β Ser(9) and the expression levels of early growth response-1 (Egr-1), transcription factor 7-like 2 (TCF7L2) and cyclin D1. DIF-1 also inhibited the growth of HCT-116- and HeLa-xenograft tumors together with decreasing phosphorylation level of GSK-3β Ser(9), although it was not statistically significant in HeLa-xenograft tumors. DIF-1 also suppressed the expressions of Egr-1, TCF7L2 and cyclin D1 in HCT-116-xenograft tumors and those of β-catenin, TCF7L2 and cyclin D1 in HeLa-xenograft tumors. This is the first report to show that DIF-1 inhibits tumor growth in vivo, consistent with its in-vitro action, suggesting that this compound may have potential as a novel anti-tumor agent.

DNA methylation: potential biomarker in Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is one of the most common cancers in the world and it is often associated with poor prognosis. Liver transplantation and resection are two currently available curative therapies. However, most patients cannot be treated with such therapies due to late diagnosis. This underscores the urgent need to identify potential markers that ensure early diagnosis of HCC. As more evidences are suggesting that epigenetic changes contribute hepatocarcinogenesis, DNA methylation was poised as one promising biomarker. Indeed, genome wide profiling reveals that aberrant methylation is frequent event in HCC. Many studies showed that differentially methylated genes and CpG island methylator phenotype (CIMP) status in HCC were associated with clinicopathological data. Some commonly studied hypermethylated genes include p16, SOCS1, GSTP1 and CDH1. In addition, studies have also revealed that methylation markers could be detected in patient blood samples and associated with poor prognosis of the disease. Undeniably, increasing number of methylation markers are being discovered through high throughput genome wide data in recent years. Proper and systematic validation of these candidate markers in prospective cohort is required so that their actual prognostication and surveillance value could be accurately determined. It is hope that in near future, methylation marker could be translate into clinical use, where patients at risk could be diagnosed early and that the progression of disease could be more correctly assessed.

Impact of chromosomal instability on colorectal cancer progression and outcome

Background

It remains presently unclear whether disease progression in colorectal carcinoma (CRC), from early, to invasive and metastatic forms, is associated to a gradual increase in genetic instability and to a scheme of sequentially occurring Copy Number Alterations (CNAs).

Methods

In this work we set to determine the existence of such links between CRC progression and genetic instability and searched for associations with patient outcome. To this aim we analyzed a set of 162 Chromosomal Instable (CIN) CRCs comprising 131 primary carcinomas evenly distributed through stage 1 to 4, 31 metastases and 14 adenomas by array-CGH. CNA profiles were established according to disease stage and compared. We, also, asked whether the level of genomic instability was correlated to disease outcome in stage 2 and 3 CRCs. Two metrics of chromosomal instability were used; (i) Global Genomic Index (GGI), corresponding to the fraction of the genome involved in CNA, (ii) number of breakpoints (nbBP).

Results

Stage 1, 2, 3 and 4 tumors did not differ significantly at the level of their CNA profiles precluding the conventional definition of a progression scheme based on increasing levels of genetic instability. Combining GGI and nbBP,we classified genomic profiles into 5 groups presenting distinct patterns of chromosomal instability and defined two risk classes of tumors, showing strong differences in outcome and hazard risk (RFS: p = 0.012, HR = 3; OS: p < 0.001, HR = 9.7). While tumors of the high risk group were characterized by frequent fractional CNAs, low risk tumors presented predominantly whole chromosomal arm CNAs. Searching for CNAs correlating with negative outcome we found that losses at 16p13.3 and 19q13.3 observed in 10% (7/72) of stage 2–3 tumors showed strong association with early relapse (p < 0.001) and death (p < 0.007, p < 0.016). Both events showed frequent co-occurrence (p < 1x10-8) and could, therefore, mark for stage 2–3 CRC susceptible to negative outcome.

Conclusions

Our data show that CRC disease progression from stage 1 to stage 4 is not paralleled by increased levels of genetic instability. However, they suggest that stage 2–3 CRC with elevated genetic instability and particularly profiles with fractional CNA represent a subset of aggressive tumors.

Promoter methylation of SFRP3 is frequent in hepatocellular carcinoma

Oncogenic activation of the Wnt/β-catenin signaling pathway is common in human cancers. The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and have important implications in carcinogenesis. Because there have been no reports about the role of SFRP3 in hepatocellular carcinoma (HCC), we investigated the level of methylation and transcription of SFRP3. Four HCC cell lines, 60 HCCs, 23 cirrhosis livers, 37 chronic hepatitis livers, and 30 control livers were prescreened for SFRP3 promoter methylation by methylation-specific polymerase chain reaction (MS-PCR) and bisulfite sequencing. SFRP3 promoter methylation was observed in 100%, 60%, 39.1%, 16.2%, and 0% in HCC cell lines, primary HCCs, cirrhosis livers, chronic hepatitis livers, and control livers, respectively. Demethylation treatment with 5-aza-2′-deoxycytidine in HCC cells restored or increased the SFRP3 mRNA expression. We next used quantitative MS-PCR (QMSP) to analyze the methylation level of SFRP3 in 60 HCCs and their corresponding nontumor tissues. Methylation of SFRP3 promoter region in HCCs increased significantly compared with control tissues. There is a positive correlation between promoter hypermethylation and SFRP3 mRNA downregulation. Our data suggest that promoter hypermethylation of SFRP3 is a common event in HCCs and plays an important role in regulation of SFRP3 mRNA expression.

Glypican-3 binds to frizzled and plays a direct role in the stimulation of canonical Wnt signaling

Glypican-3 (GPC3) is a proteoglycan that is bound to the cell surface. It is expressed by most hepatocellular carcinomas (HCCs), but not by normal hepatocytes. GPC3 stimulates HCC growth by promoting canonical Wnt signaling. Because glypicans interact with Wnts, it has been proposed that these proteoglycans stimulate signaling by increasing the amount of Wnt at the cell membrane, facilitating in this way the interaction of this growth factor with its signaling receptor Frizzled. However, in this study we demonstrate that GPC3 plays a more direct role in the stimulation of Wnt signaling. Specifically, we show that, in addition to interacting with Wnt, GPC3 directly binds to Frizzled through its glycosaminoglycan chains, indicating that this glypican stimulates the formation of signaling complexes between these two proteins. Consistent with this, we show that Wnt binding at the cell membrane triggers the endocytosis of a complex that includes Wnt, Frizzled and GPC3. Additional support to our model is provided by the finding that Glypican-6 (GPC6) inhibits canonical Wnt signaling despite the fact that it binds to Wnt at the cell membrane.

Target genes discovery through copy number alteration analysis in human hepatocellular carcinoma

High-throughput short-read sequencing of exomes and whole cancer genomes in multiple human hepatocellular carcinoma (HCC) cohorts confirmed previously identified frequently mutated somatic genes, such as TP53, CTNNB1 and AXIN1, and identified several novel genes with moderate mutation frequencies, including ARID1A, ARID2, MLL, MLL2, MLL3, MLL4, IRF2, ATM, CDKN2A, FGF19, PIK3CA, RPS6KA3, JAK1, KEAP1, NFE2L2, C16orf62, LEPR, RAC2, and IL6ST. Functional classification of these mutated genes suggested that alterations in pathways participating in chromatin remodeling, Wnt/β-catenin signaling, JAK/STAT signaling, and oxidative stress play critical roles in HCC tumorigenesis. Nevertheless, because there are few druggable genes used in HCC therapy, the identification of new therapeutic targets through integrated genomic approaches remains an important task. Because a large amount of HCC genomic data genotyped by high density single nucleotide polymorphism arrays is deposited in the public domain, copy number alteration (CNA) analyses of these arrays is a cost-effective way to reveal target genes through profiling of recurrent and overlapping amplicons, homozygous deletions and potentially unbalanced chromosomal translocations accumulated during HCC progression. Moreover, integration of CNAs with other high-throughput genomic data, such as aberrantly coding transcriptomes and non-coding gene expression in human HCC tissues and rodent HCC models, provides lines of evidence that can be used to facilitate the identification of novel HCC target genes with the potential of improving the survival of HCC patients.

Pancreatic cancer-associated retinoblastoma 1 dysfunction enables TGF-β to promote proliferation

Pancreatic ductal adenocarcinoma (PDAC) is often associated with overexpression of TGF-β. Given its tumor suppressor functions, it is unclear whether TGF-β is a valid therapeutic target for PDAC. Here, we found that proliferating pancreatic cancer cells (PCCs) from human PDAC patients and multiple murine models of PDAC (mPDAC) often exhibit abundant levels of phosphorylated retinoblastoma 1 (RB) and Smad2. TGF-β1 treatment enhanced proliferation of PCCs isolated from KrasG12D-driven mPDAC that lacked RB (KRC cells). This mitogenic effect was abrogated by pharmacological inhibition of type I TGF-β receptor kinase, combined inhibition of MEK/Src or MEK/PI3K, and restoration of RB expression. TGF-β1 promoted epithelial-to-mesenchymal transition (EMT), invasion, Smad2/3 phosphorylation, Src activation, Wnt reporter activity, and Smad-dependent upregulation of Wnt7b in KRC cells. Importantly, TGF-β1-induced mitogenesis was markedly attenuated by inhibition of Wnt secretion. In an in vivo syngeneic orthotopic model, inhibition of TGF-β signaling suppressed KRC cell proliferation, tumor growth, stroma formation, EMT, metastasis, ascites formation, and Wnt7b expression, and markedly prolonged survival. Together, these data indicate that RB dysfunction converts TGF-β to a mitogen that activates known oncogenic signaling pathways and upregulates Wnt7b, which synergize to promote PCC invasion, survival, and mitogenesis. Furthermore, this study suggests that concomitantly targeting TGF-β and Wnt7b signaling in PDAC may disrupt these aberrant pathways, which warrants further evaluation in preclinical models.

AXIN genetic analysis in adrenocortical carcinomas updated

BACKGROUND

Wnt/β-catenin signaling pathway activation plays an important role in adrenocortical tumorigenesis, but is only in part related to β-catenin activating somatic mutations. Recently, genetic alteration in AXIN2, a key component of the Wnt/β-catenin signaling pathway, has been described in adrenocortical tumors and specifically in adrenocortical carcinoma (ACC).

AIM

To assess frequency and consequences of AXIN genes alteration on a large cohort of ACC.

PATIENTS AND METHODS

Forty-nine adult sporadic ACC, with expression data available, in addition to both ACC cell lines H295 and H295R were studied. AXIN2 exon 8 hot-spot sequencing was performed on the entire cohort. AXIN1 entire coding region was studied on the 8 ACC with nuclear β-catenin staining.

RESULTS

The previously described AXIN2 in-frame heterozygous 12bp deletion c2013_2024del12 was found in 1 of the 49 ACC studied (2%), in a tumor with pSer45del activating CTNNB1 mutation and nuclear β-catenin staining. This heterozygous deletion was also found in the patient's germline DNA, extracted from peripheral blood leukocytes. This genetic alteration was also present in H295 and H295R cell lines. The single-nucleotide polymorphism rs35415678 was found with an allele frequency similar to those found in reference populations. No correlation between AXIN2 expression, AXIN2 genetic variant or nuclear β- catenin staining was observed. No AXIN1 alterations were found in the 8 ACC studied.

CONCLUSIONS

AXIN genes do not play a major role in ACC tumorigenesis and Wnt/β-catenin signaling pathway activation. AXIN2 germline variant c2013_2024del12 is likely to be a non-pathogenic polymorphism.

Gene expression profiling analysis of hepatocellular carcinoma

Background

Primary hepatocellular carcinoma (HCC) is one of the most common malignancies in the world. However, the molecular pathogenesis of HCC is not well-understood, and the prognosis for patients with HCC remains very poor.

Methods

To disclose detailed genetic mechanisms in hepatocellular carcinoma (HCC) with a view toward development of novel therapeutic targets, we analyzed expression profiles HCCs and their corresponding noncancerous tissues by using bioinformatics method.

Results

In this paper, we report the identification of genes whose expression has been altered and the changed bio-pathways during hepatocarcinogenesis. Hepatoma cells infect intracellular and intercellular signal transduction through Focal adhesion and cause abnormal expression of important intracellular signaling pathway. In addition, it is worth mentioning that some small molecules still restored to the state similar to normal cells, such as bambuterol and lovastatin. This member gene set would serve as a pool of lead gene targets for the identification and development of novel diagnostic and therapeutic biomarkers to greatly improve the clinical management of HCC patients with different risks of recurrence after curative partial hepatectomy.

Conclusions

The study has great significance for gene therapy and pharmacotherapy and provides a new treatment entry point and a potential new clinical drug for HCC patients.

Destabilization of heterologous proteins mediated by the GSK3β phosphorylation domain of the β-catenin protein

BACKGROUND AND AIMS

Wnt/β-catenin signaling plays important roles in development and cellular processes. The hallmark of canonical Wnt signaling activation is the stabilization of β-catenin protein in cytoplasm and/or nucleus. The stability of β-catenin is the key to its biological functions and is controlled by the phosphorylation of its amino-terminal degradation domain. Aberrant activation of β-catenin signaling has been implicated in the development of human cancers. It has been recently suggested that GSK3βmay play an essential role in regulating global protein turnover. Here, we investigate if the GSK3β phosphorylation site-containing degradation domain of β-catenin is sufficient to destabilize heterologous proteins.

METHODS AND RESULTS

We engineer chimeric proteins by fusing β-catenin degradation domain at the N- and/or C-termini of the enhanced green fluorescent protein (eGFP). In both transient and stable expression experiments, the chimeric GFP proteins exhibit a significantly decreased stability, which can be effectively antagonized by lithium and Wnt1. An activating mutation in the destruction domain significantly stabilizes the fusion protein. Furthermore, GSK3 inhibitor SB-216763 effectively increases the GFP signal of the fusion protein. Conversely, the inhibition of Wnt signaling with tankyrase inhibitor XAV939 results in a decrease in GFP signal of the fusion proteins, while these small molecules have no significant effects on the mutant destruction domain-GFP fusion protein.

CONCLUSION

Our findings strongly suggest that the β-catenin degradation domain may be sufficient to destabilize heterologous proteins in Wnt signaling-dependent manner. It is conceivable that the chimeric GFP proteins may be used as a functional reporter to measure the dynamic status of β-catenin signaling, and to identify potential anticancer drugs that target β-catenin signaling.

Wnt signaling and hepatocarcinogenesis: molecular targets for the development of innovative anticancer drugs

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer death worldwide. HCC can be cured by radical therapies if early diagnosis is done while the tumor has remained of small size. Unfortunately, diagnosis is commonly late when the tumor has grown and spread. Thus, palliative approaches are usually applied such as transarterial intrahepatic chemoembolization and sorafenib, an anti-angiogenic agent and MAP kinase inhibitor. This latter is the only targeted therapy that has shown significant, although moderate, efficiency in some individuals with advanced HCC. This highlights the need to develop other targeted therapies, and to this goal, to identify more and more pathways as potential targets. The Wnt pathway is a key component of a physiological process involved in embryonic development and tissue homeostasis. Activation of this pathway occurs when a Wnt ligand binds to a Frizzled (FZD) receptor at the cell membrane. Two different Wnt signaling cascades have been identified, called non-canonical and canonical pathways, the latter involving the β-catenin protein. Deregulation of the Wnt pathway is an early event in hepatocarcinogenesis and has been associated with an aggressive HCC phenotype, since it is implicated both in cell survival, proliferation, migration and invasion. Thus, component proteins identified in this pathway are potential candidates of pharmacological intervention. This review focuses on the characteristics and functions of the molecular targets of the Wnt signaling cascade and how they may be manipulated to achieve anti-tumor effects.

Distinctive microRNA signature associated of neoplasms with the Wnt/β-catenin signaling pathway

As the crucial biological regulators, microRNAs that act by suppressing their target genes are involved in a variety of pathophysiological processes. It is generally accepted that microRNAs are often dysregulated in many types of neoplasm and other human diseases. In neoplasm, microRNAs may function as oncogenes or tumor suppressors. As constitutive activation of the Wnt signaling pathway is a common feature of neoplasm and contributes to its development, progression and metastasis in various cancers, numerous studies have revealed that microRNA-mediated gene regulation are interconnected with the Wnt/β-catenin signaling pathway, forming a Wnt/β-catenin-microRNA regulatory network, which is critical to successful targeting of the Wnt/β-catenin pathway for oncotherapy. In this review, we aim to accumulate recent advances on microRNAs that work in tandem with Wnt/β-catenin signaling in tumorigenesis, with particular focus on how microRNAs affect Wnt/β-catenin activity as well as how microRNAs are regulated through the Wnt/β-catenin pathway.

Inhibitory effect of a standardized pomegranate fruit extract on Wnt signalling in 1, 2-dimethylhydrazine induced rat colon carcinogenesis

BACKGROUND

De-regulation of Wnt signalling is increasingly being implicated in both experimental and human carcinogenesis including colon cancer.

AIMS

Our goal was to identify possible dietary agents that block Wnt signalling as a step toward investigating new strategies for suppression of colon cancer. Pomegranate extract has emerged as an intriguing candidate due to its polyphenolic content.

METHODS

We used a 1,2-dimethylhydrazine dihydrochloride (DMH)-induced rat colon carcinogenesis model to investigate the expression pattern of the main key players in Wnt signalling by reverse transcription polymerase chain reaction (RT-PCR) analysis.

RESULTS

Our results showed that many Wnt-target genes, e.g., Wnt5a, frizzled receptor (FRZ)-8, β-catenin, T cell factor/lymphoid enhancer binding protein (Tcf4/Lef1), c-myc and cyclin D1, were up-regulated whereas adenomatous polyposis coli (APC) and axin1 exhibited down-regulation in colonic tissues of our DMH-colon cancer group compared with the normal group. Standardized pomegranate extract minimised all the aberrant alterations observed in the studied Wnt genes in colonic tissues of the DMH+pomegranate group as compared with the DMH-induced colon cancer group. This effect was also confirmed by the normalization of survival rate, inhibition of tumour incidence and a reduction of serum tumour marker carcinoembryonic antigen (CEA) level. Histopathological observations provided supportive evidence for the biochemical and molecular analyses.

CONCLUSIONS

Standardized pomegranate extract holds great promise in the field of colon cancer prevention by dietary agents.

The SxxSS motif of T-cell factor-4 isoforms modulates Wnt/β-catenin signal activation in hepatocellular carcinoma cells

T-cell factor (TCF) proteins represent key transcription factors in Wnt signaling. We show that the SxxSS motif in TCF-4 regulates transcriptional activity in HCC cells. TCF-4K mutants increased transcriptional activity compared to TCF-4K (bearing the SxxSS); the binding pattern of co-factors in TCF-4K mutants was similar to that in TCF-4J (lacking the SxxSS). TCF activity in TCF-4K cells was suppressed by homeodomain-interacting protein kinase 2 (HIPK2), but not in TCF-4J cells. Together, our data indicates that the SxxSS motif in TCF-4K regulates transcriptional activity by modifying co-factors in the β-catenin/TCF-4 transcriptional complex and these events may be mediated through HIPK2.

Upregulation of T-cell factor-4 isoform-responsive target genes in hepatocellular carcinoma

BACKGROUND

The Wnt/β-catenin signalling pathway regulates genes involved in cell proliferation, survival, migration and invasion through regulation by T-cell factor (TCF)-4 transcription factor proteins. However, the role of TCF-4 isoforms generated by alternative splicing events in hepatocellular carcinoma (HCC) is unknown.

AIM

Here, we investigated TCF-4 isoforms (TCF-4J and K)-responsive target genes that are important in hepatic oncogenesis and tumour development.

METHODS

Gene expression microarray was performed on HCC cells overexpressing TCF-4J and K isoforms. Expression level of selected target genes was evaluated and correlations were made between their expression level and that of TCF-4 isoform in 47 pairs of human HCC tumours.

RESULTS

Comparison by gene expression microarray revealed that 447 genes were upregulated and 343 downregulated more than 2.0-fold in TCF-4J compared with TCF-4K expressing cells. We validated expression of 18 selected target genes involved in Wnt/β-catenin, insulin/IGF-1/IRS1 and Notch signalling pathways in 47 pairs of human HCCs and adjacent uninvolved liver tissues. It was observed that 13 genes (CLDN2, STK17B, SPP1, AXIN2, WISP2, MMP7, IRS1, ANXA1, CAMK2N1, ASPH, GPR56, CD24 and JAG1) activated by TCF-4J isoform in HCC cells, were also upregulated in HCC tumours compared with adjacent peritumour tissue; more importantly, 10 genes exhibited a significant correlation with the TCF-4J expression level in tumour.

CONCLUSION

TCF-4 isoforms (TCF-4J and K) activated different downstream target genes in HCC. The biological consequence of TCF-4J isoform expression was upregulation of genes associated with tripartite Wnt/β-catenin, insulin/IGF-1/IRS1 and Notch signal transduction pathway activation, which contribute to the pathogenesis of HCC.

Whole-genome sequencing identifies recurrent mutations in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide and has no effective treatment, yet the molecular basis of hepatocarcinogenesis remains largely unknown. Here we report findings from a whole-genome sequencing (WGS) study of 88 matched HCC tumor/normal pairs, 81 of which are Hepatitis B virus (HBV) positive, seeking to identify genetically altered genes and pathways implicated in HBV-associated HCC. We find beta-catenin to be the most frequently mutated oncogene (15.9%) and TP53 the most frequently mutated tumor suppressor (35.2%). The Wnt/beta-catenin and JAK/STAT pathways, altered in 62.5% and 45.5% of cases, respectively, are likely to act as two major oncogenic drivers in HCC. This study also identifies several prevalent and potentially actionable mutations, including activating mutations of Janus kinase 1 (JAK1), in 9.1% of patients and provides a path toward therapeutic intervention of the disease.

TRIB2 acts downstream of Wnt/TCF in liver cancer cells to regulate YAP and C/EBPα function

Dysregulation of Wnt signaling is closely associated with human liver tumorigenesis. However, liver cancer-specific Wnt transcriptional programs and downstream effectors remain poorly understood. Here, we identify tribbles homolog 2 (TRIB2) as a direct target of Wnt/TCF in liver cancer and demonstrate that transcription of Wnt target genes, including TRIB2, is coordinated by the TCF and FoxA transcription factors in liver cancer cells. We show that Wnt-TRIB2 activation is critical for cancer cell survival and transformation. Mechanistically, TRIB2 promotes protein stabilization of the YAP transcription coactivator through interaction with the βTrCP ubiquitin ligase. Furthermore, we find that TRIB2 relieves the liver tumor suppressor protein C/EBPα-mediated inhibition of YAP/TEAD transcriptional activation in liver cancer cells. Altogether, our study uncovers a regulatory mechanism underlying liver cancer-specific Wnt transcriptional output, and suggests that TRIB2 functions as a signaling nexus to integrate the Wnt/β-catenin, Hippo/YAP, and C/EBPα pathways in cancer cells.

Effect of pantoprazole on human gastric adenocarcinoma SGC7901 cells through regulation of phospho‑LRP6 expression in Wnt/β-catenin signaling

Recent studies have found that an acidic tumor microenvironment is the key to managing cancer progression and metastasis. Our previous study found that proton pump inhibitors (PPIs) inhibit the expression of vacuolar-ATPases (V-ATPases) and reverse the transmembrane pH gradient. The present study was conducted to explore the effect of pantoprazole on gastric adenocarcinoma through the regulation of Wnt/β-catenin signaling. We used SGC7901 human gastric cancer cells as an in vitro model to study the effect of pantoprazole. The antiproliferative, pro-apoptotic and anti‑invasive effects of pantoprazole were examined. The effects of pantoprazole on the expression of the Wnt/β-catenin signaling pathway were also studied by western blotting. Our study found that pantoprazole inhibited the proliferation and induced the apoptosis of SGC7901 human gastric cancer cells. The expression of V-ATPases was decreased following treatment with pantoprazole. Further study found that pantoprazole treatment caused a decrease in phospho-LRP6, but not in LRP6. β-catenin in Wnt/β-catenin signaling and its target genes c-Myc and cyclin D1 were also decreased upon the inhibition of V-ATPases. Therefore, pantoprazole could be characterized as a V-ATPase inhibitor for treating gastric cancer by inhibiting the phosphorylation of LRP6 in Wnt/β-catenin signaling.

Impact of an altered Wnt1/β-catenin expression on clinicopathology and prognosis in clear cell renal cell carcinoma

In renal cell carcinoma (RCC), single members of the Wnt/β-catenin signaling cascade were recently identified to contribute to cancer progression. However, the role of Wnt1, one of the key ligands in β-catenin regulation, is currently unknown in RCC. Therefore, alterations of the Wnt1/β-catenin axis in clear cell RCC (ccRCC) were examined with regard to clinicopathology, overall survival (OS) and cancer specific survival (CSS). Corresponding ccRCCs and benign renal tissue were analyzed in 278 patients for Wnt1 and β-catenin expression by immunohistochemistry in tissue microarrays. Expression scores, including intensity and percentage of stained cells, were compared between normal kidney and ccRCCs. Data was categorized according to mean expression scores and correlated to tumor and patients' characteristics. Survival was analyzed according to the Kaplan-Meier and log-rank test. Univariable and multivariable Cox proportional hazard regression models were used to explore the independent prognostic value of Wnt1 and β-catenin. In ccRCCs, high Wnt1 was associated with increased tumor diameter, stage and vascular invasion (p ≤ 0.02). High membranous β-catenin was associated with advanced stage, vascular invasion and tumor necrosis (p ≤ 0.01). Higher diameter, stage, node involvement, grade, vascular invasion and sarcomatoid differentiation (p ≤ 0.01) were found in patients with high cytoplasmic β-catenin. Patients with a high cytoplasmic β-catenin had a significantly reduced OS (hazard ratio (HR) 1.75) and CSS (HR 2.26), which was not independently associated with OS and CSS after adjustment in the multivariable model. Increased ccRCC aggressiveness was reflected by an altered Wnt1/β-catenin signaling. Cytoplasmic β-catenin was identified as the most promising candidate associated with unfavorable clinicopathology and impaired survival. Nevertheless, the shift of membranous β-catenin to the cytoplasm with a subsequently increased nuclear expression, as shown for other malignancies, could not be demonstrated to be present in ccRCC.

Identification and characterization of a small-molecule inhibitor of Wnt signaling in glioblastoma cells

Glioblastoma multiforme (GBM) is the most common and prognostically unfavorable form of brain tumor. The aggressive and highly invasive phenotype of these tumors makes them among the most anatomically damaging human cancers with a median survival of less than 1 year. Although canonical Wnt pathway activation in cancers has been historically linked to the presence of mutations involving key components of the pathway (APC, β-catenin, or Axin proteins), an increasing number of studies suggest that elevated Wnt signaling in GBM is initiated by several alternative mechanisms that are involved in different steps of the disease. Therefore, inhibition of Wnt signaling may represent a therapeutically relevant approach for GBM treatment. After the selection of a GBM cell model responsive to Wnt inhibition, we set out to develop a screening approach for the identification of compounds capable of modulating canonical Wnt signaling and associated proliferative responses in GBM cells. Here, we show that the small molecule SEN461 inhibits the canonical Wnt signaling pathway in GBM cells, with relevant effects at both molecular and phenotypic levels in vitro and in vivo. These include SEN461-induced Axin stabilization, increased β-catenin phosphorylation/degradation, and inhibition of anchorage-independent growth of human GBM cell lines and patient-derived primary tumor cells in vitro. Moreover, in vivo administration of SEN461 antagonized Wnt signaling in Xenopus embryos and reduced tumor growth in a GBM xenograft model. These data represent the first demonstration that small-molecule-mediated inhibition of Wnt signaling may be a potential approach for GBM therapeutics.

All-trans retinoic acid upregulates the expression of p53 via Axin and inhibits the proliferation of glioma cells

All-trans retinoic acid (ATRA) is a potent chemopreventive and therapeutic agent and exerts its effects by inducing growth arrest. In the present study, we demonstrated that ATRA activated the expression of p53 via Axin and induced cell cycle arrest at the G1/S phase and apoptosis of glioma cells. Briefly, C6 cells were treated with ATRA, and the levels of p53 mRNA and protein were determined by RT-PCR, western blotting and immunohistochemistry. The results showed that ATRA activated the expression of p53. In addition, ectopic expression of Axin by transient transfection of C6 cells with rAxin revealed that overexpression of Axin induced cell cycle arrest and apoptosis with an upregulation of p53. Furthermore, loss-of-function of Axin in glioma cells by RNAi blocked ATRA-induced cell cycle phase arrest and apoptosis via downregulation of p53. The present study revealed a novel function of Axin and identified it as an important regulator of ATRA-activated p53 expression.

Frequent concomitant epigenetic silencing of SOX1 and secreted frizzled-related proteins (SFRPs) in human hepatocellular carcinoma

BACKGROUND AND AIM

Except for genetic mutations, epigenetic changes are also involved in the development of human cancers. Recently, we have identified SOX1, SRY (sex determining region Y)-box 1, is hypermethylated in cervical cancer and ovarian cancer. Therefore, we investigated whether promoter hypermethylation of SOX1 is common in hepatocellular carcinoma (HCC).

METHODS

We used methylation-specific polymerase chain reaction (MS-PCR) and bisulfite sequencing to analyze the methyaltion level of the SOX1 promoter in seven HCC cell lines, 54 clinical HCCs, 42 cirrhotic livers, 21 livers with chronic hepatitis, and 15 control livers. Then, we employed quantitative MS-PCR (QMSP) to validate in an independent set of samples (60 paired HCCs and 30 control livers). Finally, we used luciferase reporter and colony formation assay to check the effect of SOX1 in HCC.

RESULTS

Promoter methylation of SOX1 was significantly frequent in HCC cell lines and clinical HCCs, cirrhotic livers, but not in control livers (P < 0.0001). There is a significant correlation between downregulation of SOX1 expression and promoter methylation. QMSP results confirmed that promoter hypermethylation of SOX1 is significantly more frequent in HCCs than control livers (P < 0.0001). The frequency of SOX1 methylation in patients with secreted frizzled-related proteins (SFRPs) methylation is significantly higher than in patients without SFRPs methylation (P < 0.0001). Furthermore, ectopic expression of SOX1 could suppress T-cell factor-dependent transcriptional activity and colony formation number in HCCs.

CONCLUSIONS

Concomitant epigenetic silencing of SOX1 and SFRPs through promoter hypermethylation is frequent in HCCs, and this might contribute to abnormal activation of canonical Wnt signal pathway.

Dickkopf-1 inhibits thyroid cancer cell survival and migration through regulation of β-catenin/E-cadherin signaling

Wnt/β-catenin signaling plays a role in tumorigenesis of human papillary thyroid cancer (PTC). Dickkopf-1 (Dkk-1) is an inhibitor of Wnt/β-catenin signaling. We investigated the therapeutic potential of Dkk-1 in human PTC cell lines, SNU-790, B-CPAP, and BHP10-3. Dkk-1 reversed the aberrant expression of β-catenin from nucleus to membrane and inhibited basal levels of TCF/LEF-dependent transcriptional activities. Furthermore, Dkk-1 inhibited cell viability in a dose-dependent manner and adenoviral transduction of constitutively active β-catenin blocked these effects, thus suggesting that the Dkk-1 anti-tumoral effect is mediated by Wnt/β-catenin signaling. Bromodeoxyuridine assay showed minimal effects of Dkk-1 on cell proliferation. Flow cytometric analysis with Annexin V staining showed marked induction of cell apoptosis by Dkk-1 treatment. Dkk-1 also restored the loss of membranous E-cadherin expression with consequent inhibition of cell migration and invasion. In conclusion, Dkk-1 inhibited the survival and migration of human PTC cells by regulating Wnt/β-catenin signaling and E-cadherin expression.