Functional significance of Wnt inhibitory factor-1 gene in kidney cancer

Wnt/β-catenin signaling pathway in the tumor progression of adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an uncommon, aggressive endocrine malignancy with a high rate of recurrence, a poor prognosis, and a propensity for metastasis. Currently, only mitotane has received certification from both the US Food and Drug Administration (FDA) and the European Medicines Agency for the therapy of advanced ACC. However, treatment in the advanced periods of the disorders is ineffective and has serious adverse consequences. Completely surgical excision is the only cure but has failed to effectively improve the survival of advanced patients. The aberrantly activated Wnt/β-catenin pathway is one of the catalysts for adrenocortical carcinogenesis. Research has concentrated on identifying methods that can prevent the stimulation of the Wnt/β-catenin pathway and are safe and advantageous for patients in view of the absence of effective treatments and the frequent alteration of the Wnt/β-catenin pathway in ACC. Comprehending the complex connection between the development of ACC and Wnt/β-catenin signaling is essential for accurate pharmacological targets. In this review, we summarize the potential targets between adrenocortical carcinoma and the Wnt/β-catenin signaling pathway. We analyze the relevant targets of drugs or inhibitors that act on the Wnt pathway. Finally, we provide new insights into how drugs or inhibitors may improve the treatment of ACC.

The logistics of Wnt production and delivery

Wnts are secreted proteins that control stem cell maintenance, cell fate decisions, and growth during development and adult homeostasis. Wnts carry a post-translational modification not seen in any other secreted protein: during biosynthesis, they are appended with a palmitoleoyl moiety that is required for signaling but also impairs solubility and hence diffusion in the extracellular space. In some contexts, Wnts act only in a juxtacrine manner but there are also instances of long range action. Several proteins and processes ensure that active Wnts reach the appropriate target cells. Some, like Porcupine, Wntless, and Notum are dedicated to Wnt function; we describe their activities in molecular detail. We also outline how the cell infrastructure (secretory, endocytic, and retromer pathways) contribute to the progression of Wnts from production to delivery. We then address how Wnts spread in the extracellular space and form a signaling gradient despite carrying a hydrophobic moiety. We highlight particularly the role of lipid-binding Wnt interactors and heparan sulfate proteoglycans. Finally, we briefly discuss how evolution might have led to the emergence of this unusual signaling pathway.

New insights into fibrotic signaling in renal cell carcinoma

Fibrotic signaling plays a pivotal role in the development and progression of solid cancers including renal cell carcinoma (RCC). Intratumoral fibrosis (ITF) and pseudo-capsule (PC) fibrosis are significantly correlated to the disease progression of renal cell carcinoma. Targeting classic fibrotic signaling processes such as TGF-β signaling and epithelial-to-mesenchymal transition (EMT) shows promising antitumor effects both preclinically and clinically. Therefore, a better understanding of the pathogenic mechanisms of fibrotic signaling in renal cell carcinoma at molecular resolution can facilitate the development of precision therapies against solid cancers. In this review, we systematically summarized the latest updates on fibrotic signaling, from clinical correlation and molecular mechanisms to its therapeutic strategies for renal cell carcinoma. Importantly, we examined the reported fibrotic signaling on the human renal cell carcinoma dataset at the transcriptome level with single-cell resolution to assess its translational potential in the clinic.

Mucosal melanomas of different anatomic sites share a common global DNA methylation profile with cutaneous melanoma but show location-dependent patterns of genetic and epigenetic alterations

Cutaneous, ocular, and mucosal melanomas are histologically indistinguishable tumors that are driven by a different spectrum of genetic alterations. With current methods, identification of the site of origin of a melanoma metastasis is challenging. DNA methylation profiling has shown promise for the identification of the site of tumor origin in various settings. Here we explore the DNA methylation landscape of melanomas from different sites and analyze if different melanoma origins can be distinguished by their epigenetic profile. We performed DNA methylation analysis, next generation DNA panel sequencing, and copy number analysis of 82 non-cutaneous and 25 cutaneous melanoma samples. We further analyzed eight normal melanocyte cell culture preparations. DNA methylation analysis separated uveal melanomas from melanomas of other primary sites. Mucosal, conjunctival, and cutaneous melanomas shared a common global DNA methylation profile. Still, we observed location-dependent DNA methylation differences in cancer-related genes, such as low frequencies of RARB (7/63) and CDKN2A promoter methylation (6/63) in mucosal melanomas, or a high frequency of APC promoter methylation in conjunctival melanomas (6/9). Furthermore, all investigated melanomas of the paranasal sinus showed loss of PTEN expression (9/9), mainly caused by promoter methylation. This was less frequently seen in melanomas of other sites (24/98). Copy number analysis revealed recurrent amplifications in mucosal melanomas, including chromosomes 4q, 5p, 11q and 12q. Most melanomas of the oral cavity showed gains of chromosome 5p with TERT amplification (8/10), while 11q amplifications were enriched in melanomas of the nasal cavity (7/16). In summary, mucosal, conjunctival, and cutaneous melanomas show a surprisingly similar global DNA methylation profile and identification of the site of origin by DNA methylation testing is likely not feasible. Still, our study demonstrates tumor location-dependent differences of promoter methylation frequencies in specific cancer-related genes together with tumor site-specific enrichment for specific chromosomal changes and genetic mutations. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Wnt signaling in kidney: the initiator or terminator?

The kidney is a key organ in the human body that excretes toxins and sustains the water-electrolyte balance. During embryonic development and disease progression, the kidney undergoes enormous changes in macrostructure, accompanied by a variety of microstructural histological changes, such as glomerular formation and sclerosis, tubule elongation and atrophy, interstitial establishment, and fibrosis progression. All of these rely on the frequent occurrence of cell death and growth. Notably, to overcome disease, some cells regenerate through self-repair or progenitor cell differentiation. However, the signaling mechanisms underlying kidney development and regeneration have not been elucidated. Recently, Wnt signaling has been noted to play an important role. Although it is a well-known developmental signal, the role of Wnt signaling in kidney development and regeneration is not well recognized. In this review, we review the role of Wnt signaling in kidney embryonic development, tissue repair, cell division, and progenitor cell differentiation after injury. Moreover, we briefly highlight advances in our understanding of the pathogenic mechanisms of Wnt signaling in mediating cellular senescence in kidney parenchymal and stem cells, an irreversible arrest of cell proliferation blocking tissue repair and regeneration. We also highlight the therapeutic targets of Wnt signaling in kidney diseases and provide important clues for clinical strategies.

Anti proliferative and apoptotic effects on pancreatic cancer cell lines indicate new roles for ANGPTL8 (Betatrophin)

Despite considerable advances, the treatment of pancreatic cancer (PC) still requires much effort. Unusual regulation of the Wnt and apoptotic signaling pathways is widespread in cancer incidence. For instance, the WIF1 (Wnt inhibitory factor 1) gene is down-regulated in many cancers. The purpose of this study was to determine the effects of recombinant Betatrophin, a recently discovered hormone, on MiaPaca-II and Panc-1 pancreatic cell lines. Various concentrations of Betatrophin were added to MiaPaca-II and Panc-1 pancreatic cell lines during periods of 24 , 48, and 72 h. The MTT assay was applied to investigate cell proliferation after treatment. The rate of apoptotic cells was assessed using double-staining flow cytometry, and the expression levels of the WIF1 gene and Bcl2 protein was observed by real-time PCR and western blotting, respectively. The findings of this study suggest that Betatrophin has an anti-proliferative effect on both MiaPaca-II and Panc-1 cell lines, in line with the up-regulation of WIF1 as a tumor suppressor gene. Moreover, the induction of apoptosis by ANGPTL8 occurred by the down-regulation of Bcl2. Thus, Betatrophin can be proposed as a potential therapeutic drug for treating pancreatic cancer.

Secretome profiling identifies neuron-derived neurotrophic factor as a tumor-suppressive factor in lung cancer

Clinical and preclinical studies show tissue-specific differences in tumorigenesis. Tissue specificity is controlled by differential gene expression. We prioritized genes that encode secreted proteins according to their preferential expression in normal lungs to identify candidates associated with lung cancer. Indeed, most of the lung-enriched genes identified in our analysis have known or suspected roles in lung cancer. We focused on the gene encoding neuron-derived neurotrophic factor (NDNF), which had not yet been associated with lung cancer. We determined that NDNF was preferentially expressed in the normal adult lung and that its expression was decreased in human lung adenocarcinoma and a mouse model of this cancer. Higher expression of NDNF was associated with better clinical outcome of patients with lung adenocarcinoma. Purified NDNF inhibited proliferation of lung cancer cells, whereas silencing NDNF promoted tumor cell growth in culture and in xenograft models. We determined that NDNF is downregulated through DNA hypermethylation near CpG island shores in human lung adenocarcinoma. Furthermore, the lung cancer-related DNA hypermethylation sites corresponded to the methylation sites that occurred in tissues with low NDNF expression. Thus, by analyzing the tissue-specific secretome, we identified a tumor-suppressive factor, NDNF, which is associated with patient outcomes in lung adenocarcinoma.

Methylation of tumour suppressor genes associated with thyroid cancer

BACKGROUND

Thyroid carcinoma is the most common endocrine malignancy worldwide. Changes in DNA methylation can cause silencing of normally active genes, especially tumour suppressor genes (TSG) or activation of normally silent genes.

OBJECTIVE

The aim of this study is to evaluate the degree of promoter methylation for a panel of markers for thyroid neoplasms and to establish their relationship with thyroid oncogenesis.

METHODS

To generate a comprehensive DNA methylation signature of TSGs involved in thyroid neoplasia, we use Human TSG EpiTect Methyl II Signature PCR Array-Qiagen for 24 samples (follicular adenomas and papillary thyroid carcinomas) compared with normal thyroid tissue. We extended the evaluation for three TSGs (TP73, WIF1, PDLIM4) using qMS-PCR. Statistical analysis was performed with GraphPad Prism.

RESULTS

We noted four important genes NEUROG1, ESR1, RUNX3, MLH1, which presented methylated promoter in tumour samples compared to normal. We found new characteristic of thyroid tumours: methylation of TP73, WIF1 and PDLIM4 TSGs, which can contribute to thyroid neoplasia. A significant correlation between BRAF V600E mutation and RET/PTC rearrangements with TIMP3 and CDH13, RARB methylation, respectively was observed.

CONCLUSIONS

TSGs promoter hypermethylation is a hallmark of cancer and a test that uses methylation quantification method is suitable for diagnosis and prognosis of thyroid cancer.

Wnt inhibitory factor-1-mediated autophagy inhibits Wnt/β-catenin signaling by downregulating dishevelled-2 expression in non-small cell lung cancer cells

Wnt inhibitory factor‑1 (WIF‑1) is an important antagonist of Wnt/β‑catenin signaling by binding to Wnt ligands. The downregulation of WIF‑1 leads to the development of non‑small cell lung cancer (NSCLC). The upregulation of WIF‑1 significantly inhibits proliferation and induces apoptosis by inhibiting Wnt/β‑catenin signaling in NSCLC. However, the mechanisms underlying the inhibition of Wnt/β‑catenin signaling by WIF‑1‑mediated autophagy are poorly understood. Thus, in this study, we aimed to shed some light into these mechanisms. The upregulation of WIF‑1‑induced autophagy in NSCLC cells was detected by transmission electron microscopy, acridine orange staining, punctate GFP‑LC3 and immunoblotting‑based LC3 flux assay. Subsequently, WIF‑1‑mediated autophagy was blocked in NSCLC cells and the effects of WIF‑1‑mediated autophagy blocking were examined on the proliferation and apoptosis of NSCLC cells in vitro. Western blot analysis was used to investigate the molecular mechanisms effected by WIF‑1‑mediated autophagy in NSCLC cells. Finally, combination treatment with WIF‑1 and an autophagy agonist was used to examine the tumor growth inhibitory effects of WIF‑1 in vivo. The results revealed that the upregulation of WIF‑1 induced autophagy in NSCLC cells. WIF‑1‑mediated autophagy was demonstrated to inhibit Wnt/β‑catenin signaling by downregulating dishevelled‑2 (Dvl2), which contributed to the inhibition of the proliferation and the promotion of the apoptosis of NSCLC cells. Moreover, the induction of autophagy mediated by WIF‑1 was associated with to suppression of the activation of the phosphoinositide 3‑kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. Finally, we found that transfection with a WIF‑1 gene overexpression vector in combination with treatment with the autophagy agonist, everolimus (RAD001) exerted synergistic antitumor effects on A549 subcutaneous tumor xenografts and pulmonary metastasis in mice. On the whole, the findings of this study demonstrated that WIF‑1‑mediated autophagy inhibits Wnt/β‑catenin signaling by downregulating Dvl2 expression in NSCLC cells. This may a novel molecular mechanism through which WIF‑1 inhibits Wnt/β‑catenin signaling. This study may provide a theoretical basis for joint therapy of NSCLC with WIF‑1 and autophagic agonists in clinical practice.

The biochemistry, signalling and disease relevance of RYK and other WNT-binding receptor tyrosine kinases

The receptor tyrosine kinases (RTKs) are a well-characterized family of growth factor receptors that have central roles in human disease and are frequently therapeutically targeted. The RYK, ROR, PTK7 and MuSK subfamilies make up an understudied subset of WNT-binding RTKs. Numerous developmental, stem cell and pathological roles of WNTs, in particular WNT5A, involve signalling via these WNT receptors. The WNT-binding RTKs have highly context-dependent signalling outputs and stimulate the β-catenin-dependent, planar cell polarity and/or WNT/Ca²⁺ pathways. RYK, ROR and PTK7 members have a pseudokinase domain in their intracellular regions. Alternative signalling mechanisms, including proteolytic cleavage and protein scaffolding functions, have been identified for these receptors. This review explores the structure, signalling, physiological and pathological roles of RYK, with particular attention paid to cancer and the possibility of therapeutically targeting RYK. The other WNT-binding RTKs are compared with RYK throughout to highlight the similarities and differences within this subset of WNT receptors.

Secreted Wnt antagonists in leukemia: A road yet to be paved

Wnt signaling has been a topic of research for many years for its diverse and fundamental functions in physiological (such as embryogenesis, organogenesis, proliferation, tissue repair and cellular differentiation) and pathological (carcinogenesis, congenital/genetic diseases, and tissue degeneration) processes. Wnt signaling pathway aberrations are associated with both solid tumors and hematological malignancies. Unregulated Wnt signaling observed in malignancies may be due to a wide spectrum of abnormalities, from mutations in the genes of key players to epigenetic modifications of Wnt antagonists. Of these, Wnt antagonists are gaining significant attention for their potential of being targets for treatment and inhibition of Wnt signaling. In this review, we discuss and summarize the significance of Wnt signaling antagonists in the pathogenesis and treatment of hematological malignancies.

Wnt signaling in cervical cancer?

Cervical cancer (CC) is the second most common malignant cancer in women. CC is difficult to diagnose, has a high recurrence rate, and is resistant to systemic therapies; as a result, CC patients have a relatively poor prognosis. One potential link to CC is the Wnt signaling pathway and its downstream effectors, which regulate cell differentiation, proliferation, migration, and fate. The aberrant activation of Wnt signaling is associated with various cancers, including CC. Recent studies have shown that activating or inhibiting the intracellular signal transduction in this pathway can regulate cancer cell growth and viability. This review will summarize the experimental evidence supporting the significance of the Wnt signaling pathway in CC, and will also discuss the current clinical role of Wnt signaling in CC diagnosis, therapy, and prognosis.

WNT signalling events near the cell membrane and their pharmacological targeting for the treatment of cancer

WNT signalling is an essential signalling pathway for all multicellular animals. Although first described more than 30 years ago, new components and regulators of the pathway are still being discovered. Considering its importance in both embryonic development and adult homeostasis, it is not surprising that this pathway is often deregulated in human diseases such as cancer. Recently, it became clear that in addition to cytoplasmic components such as β-catenin, other, membrane-bound or extracellular, components of the WNT pathway are also altered in cancer. This review gives an overview of the recent discoveries on WNT signalling events near the cell membrane. Furthermore, membrane-associated components of the WNT pathway, which are more accessible for therapeutic intervention, as well therapeutic approaches that already target those components will be discussed. In this way, we hope to stimulate the development of effective anti-cancer therapies that target this fascinating pathway.

LINKED ARTICLES

This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

Hypermethylation of WIF1 and its inhibitory role in the tumor growth of endometrial adenocarcinoma

Endometrial carcinoma is the most common malignancy of the female genital tract and is the fourth most common malignancy among women worldwide. Endometrial adenocarcinoma (EAC) accounts for ~80% of endometrial carcinoma cases. Numerous critical genetic events have been determined to serve an essential role in EAC progression; however, the precise molecular mechanisms underlying EAC progression remain unclear. Pyrosequencing and methylation-specific PCR were used to detect the methylation status of Wnt inhibitory factor 1 (WIF1). Immunohistochemistry and western blot were used to detect the expression of WIF1, Wnt family member 1 and other related pathways. The anticancer role of WIF1 in EAC was investigated in vitro and in vivo. Two of the three EAC cases exhibited significantly high methylation in five CpG sites, and the WIF1 methylation rate in EAC and endometrial tissues was 43.4 and 8%, respectively (P<0.05). The kappa consistency coefficient was −0.369 between methylation and mRNA expression (P<0.05) and WIF1 expression levels were significantly downregulated in EAC tissues compared with non-tumorous tissues (P<0.01). The 5-year overall survival rates were significantly lower for patients with tumors that negatively expressed WIF1 when compared with the 77.9% exhibited by those with positive WIF1 expression. Furthermore, the proliferation rate of KLE cells was significantly reduced following 5-aza-20-deoxycytidine treatment or WIF1 overexpression in vitro and in vivo, which may be associated with downregulated c-Myc and phosphorylated-extracellular signal-regulated kinase expression. These results demonstrated the important role of WIF1 in EAC tumorigenesis, and suggested that WIF1 may be a potential drug target in EAC treatment.

Native Oligodendrocytes in Astrocytomas Might Inhibit Tumor Proliferation by WIF1 Expression

Malignant astrocytoma remains incurable and rapidly fatal despite multimodal therapy. In particular, accelerated tumor cell heterogeneity often overcomes therapeutic effects of molecular protein targeting. This study aimed at identifying a gene with therapeutic potential that was consistently downregulated with astrocytoma progression. Analysis of the "Rembrandt" gene expression data revealed Wnt inhibitory factor 1 (WIF1) gene as the most promising candidate with tumor suppressor function. Consequently, 288 randomly selected tissue regions of astrocytoma specimens were investigated immunohistochemically with the aid of image analysis. This in situ approach identified tumor areas with numerous single cells strongly expressing Wif-1. In diffuse and anaplastic astrocytoma, the proliferation index was independent of the generally weak Wif-1 expression in tumor cells but was significantly correlated with the density of Wif-1-expressing single cells, subsequently characterized as native and non-neoplastic oligodendrocytes. Because these cells may contribute to inhibition of tumor cell proliferation by paracrine signaling, the endogenous protein Wif-1 may represent a promising therapeutic agent with expected minimal side effects. Moreover, we suggest that immunohistochemistry for Wif might be useful for discriminating between astrocytic tumors and reactive changes.

WNT inhibitory factor 1 promoter hypermethylation is an early event during gallbladder cancer tumorigenesis that predicts poor survival

Gallbladder cancer (GBC) is the most common malignant tumor in the human biliary tract, but the lack of a marker for timely diagnosis leads to an extremely poor prognosis. In this study, we assessed CpG sites in the WIF-1 promoter using bisulfite sequencing PCR and methylation-specific PCR to detect methylation in gallbladder cancer and cholecystitis tissues. WIF-1 promoter methylation was present in 36 of 50 (72.0%) gallbladder cancers but only 5 of 20 (25.0%) cholecystitis tissues (P=0.000<0.05), suggesting that WIF-1 promoter methylation might participate in the malignant transformation of cholecystitis into gallbladder cancer. WIF-1 methylation was negatively correlated with WIF-1 protein expression by immunohistochemistry, demonstrating that WIF-1 expression is downregulated by promoter hypermethylation. We analyzed the prognosis of 50 GBC patients with 5years of follow-up. Univariate analysis revealed that patients with hypermethylated WIF-1 exhibited worse overall survival than those with hypomethylated WIF-1 (χ²=8.137, P=0.004<0.05). Furthermore, multivariate analysis revealed that WIF-1 methylation was an independent prognostic factor for 5-year overall survival (P=0.011). Therefore, WIF-1 methylation is a candidate as a marker for early gallbladder cancer diagnosis and prognosis.

The epigenetic landscape of renal cancer

The majority of kidney cancers are associated with mutations in the von Hippel-Lindau gene and a small proportion are associated with infrequent mutations in other well characterized tumour-suppressor genes. In the past 15 years, efforts to uncover other key genes involved in renal cancer have identified many genes that are dysregulated or silenced via epigenetic mechanisms, mainly through methylation of promoter CpG islands or dysregulation of specific microRNAs. In addition, the advent of next-generation sequencing has led to the identification of several novel genes that are mutated in renal cancer, such as PBRM1, BAP1 and SETD2, which are all involved in histone modification and nucleosome and chromatin remodelling. In this Review, we discuss how altered DNA methylation, microRNA dysregulation and mutations in histone-modifying enzymes disrupt cellular pathways in renal cancers.

β-Catenin Expression Negatively Correlates with WIF1 and Predicts Poor Clinical Outcomes in Patients with Cervical Cancer

Aberrant activation of the canonical Wnt pathway plays a significant role in cervical cancer (CC). However, limited data show the correlation between the cancer clinicopathological characteristics and the key molecules such as β-catenin and Wnt inhibitory factor 1 (WIF1). In this study, β-catenin and WIF1 expression were analyzed by immunohistochemistry for 196 patients with CC, 39 with cervical intraepithelial neoplasia (CIN), and 41 with normal cervical epithelium (NCE). Significant overexpression of β-catenin was detected in CC (67.9%) when compared to CIN (43.6%) or NCE (34.1%), p < 0.01, while low WIF1 expression was detected in CC (24.0%) when compared to CIN (59.0%) or NCE (58.5%), p < 0.001. Negative correlation was shown between β-catenin and WIF1 expression (r = −0.637, p < 0.001). In addition, multivariate analysis revealed that both lymph node metastasis and β-catenin expression were the independent prognostic factors not only for disease-free survival (HR = 5.029, p < 0.001; HR = 2.588, p = 0.035, resp.), but also for overall survival (HR = 5.058, p < 0.001; HR = 2.873, p = 0.031, resp.). Our findings indicate that, besides lymph node metastasis, β-catenin expression may also be a poor prognostic factor for CC while WIF1 could be a potential drug target for treatment of advanced CC.

Renal Carcinogenesis, Tumor Heterogeneity, and Reactive Oxygen Species: Tactics Evolved

SIGNIFICANCE

The number of kidney cancers is growing 3-5% each year due to unknown etiologies. Intra- and inter-tumor mediators increase oxidative stress and drive tumor heterogeneity. Recent Advances: Technology advancement in state-of-the-art instrumentation and methodologies allows researchers to detect and characterize global landscaping modifications in genes, proteins, and pathophysiology patterns at the single-cell level.

CRITICAL ISSUES

We postulate that the sources of reactive oxygen species (ROS) and their activation within subcellular compartments will change over a timeline of tumor evolvement and contribute to tumor heterogeneity. Therefore, the complexity of intracellular changes within a tumor and ROS-induced tumor heterogeneity coupled to the advancement of detecting these events globally are limited at the level of data collection, organization, and interpretation using software algorithms and bioinformatics.

FUTURE DIRECTIONS

Integrative and collaborative research, combining the power of numbers with careful experimental design, protocol development, and data interpretation, will translate cancer biology and therapeutics to a heightened level or leave the abundant raw data as stagnant and underutilized. Antioxid. Redox Signal. 25, 685-701.

Rescued expression of WIF-1 in gallbladder cancer inhibits tumor growth and induces tumor cell apoptosis with altered expression of proteins

As a highly conserved metabolic pathway, the Wnt signaling pathway is involved in cell differentiation, proliferation and several other processes. In normal cells, this pathway is suppressed, and abnormal activation is often associated with tumor occurrence and development. In certain types of tumor, Wnt inhibitory factor 1 (WIF-1), an inhibitor of the Wnt pathway, inhibits tumor growth. However, the effect of the expression of WIF-1 on gallbladder cancer remains to be fully elucidated. In the current study, reverse transcription-quantitative polymerase chain reaction and western blotting were conducted. The present study demonstrated that, in gallbladder cancer, WIF-1 generally exhibited low levels of expression as a result of gene promoter methylation. Treatment with the drug, 5-aza-2-deoxycytidine, increased the expression of WIF-1 in the GBC-SD gallbladder cell line. In addition, a WIF-1-expression plasmid was transfected into GBC-SD cells, and it was found that cell proliferation, invasion and metastasis declined significantly, whereas the apoptotic rate increased. A nude mouse tumor transplantation experiment showed that the oncogenicity of the GBC-SD cells expressing WIF-1 was substantially lower, compared with that of the untransfected GBC-SD cells and of GBD-SD cells expressing the control plasmid. A fluorescent protein chip experiment showed that the restored expression of WIF-1 affected the expression of several cellular proteins. These alterations may explain the different biological behavior of the tumor cells expressing WIF-1. As an effective inhibitory factor of the Wnt signaling pathway, WIF-1 modulated the expression of proteins controlling the proliferation, apoptosis and metastasis of gallbladder tumor cells, thus suppressing the tumor. Therefore, WIF-1 may be an effective treatment target for gallbladder cancer.

Sequential pathogenesis of metastatic VHL mutant clear cell renal cell carcinoma: putting it together with a translational perspective

Clear cell renal cell carcinoma (ccRCC) accounts for ∼80% of all RCC, and biallelic Von Hippel-Lindau (VHL) gene defects occur in ∼75% of sporadic ccRCC. The etiopathogenesis of VHL mutant metastatic RCC, based on our understanding to date of molecular mechanisms involved, is a sequence of events which can be grouped under the following: (i) loss of VHL activity (germline/somatic mutation + inactivation of the wild-type copy); (ii) constitutive activation of the hypoxia-inducible factor (HIF) pathway due to loss of VHL activity and transcription of genes involved in angiogenesis, epithelial-mesenchymal transition, invasion, metastasis, survival, anaerobic glycolysis and pentose phosphate pathway; (iii) interactions of the HIF pathway with other oncogenic pathways; (iv) genome-wide epigenetic changes (potentially driven by an overactive HIF pathway) and the influence of epigenetics on various oncogenic, apoptotic, cell cycle regulatory and mismatch repair pathways (inhibition of multiple tumor suppressor genes); (v) immune evasion, at least partially caused by changes in the epigenome. These mechanisms interact throughout the pathogenesis and progression of disease, and also confer chemoresistance and radioresistance, making it one of the most difficult metastatic cancers to treat. This article puts together the sequential pathogenesis of VHL mutant ccRCC by elaborating these mechanisms and the interplay of oncogenic pathways, epigenetics, metabolism and immune evasion, with a perspective on potential therapeutic strategies. We reflect on the huge gap between our understanding of the molecular biology and currently accepted standard of care in metastatic ccRCC, and present ideas for better translational research involving therapeutic strategies with combinatorial drug approach, targeting different aspects of the pathogenesis.

Wnt Signaling in Renal Cell Carcinoma

Renal cell carcinoma (RCC) accounts for 90% of all kidney cancers. Due to poor diagnosis, high resistance to the systemic therapies and the fact that most RCC cases occur sporadically, current research switched its focus on studying the molecular mechanisms underlying RCC. The aim is the discovery of new effective and less toxic anti-cancer drugs and novel diagnostic markers. Besides the PI3K/Akt/mTOR, HGF/Met and VHL/hypoxia cellular signaling pathways, the involvement of the Wnt/β-catenin pathway in RCC is commonly studied. Wnt signaling and its targeted genes are known to actively participate in different biological processes during embryonic development and renal cancer. Recently, studies have shown that targeting this pathway by alternating/inhibiting its intracellular signal transduction can reduce cancer cells viability and inhibit their growth. The targets and drugs identified show promising potential to serve as novel RCC therapeutics and prognostic markers. This review aims to summarize the current status quo regarding recent research on RCC focusing on the involvement of the Wnt/β-catenin pathway and how its understanding could facilitate the identification of potential therapeutic targets, new drugs and diagnostic biomarkers.

TIKI2 is upregulated and plays an oncogenic role in renal cell carcinoma

TIKI2 is a negative regulator of the Wnt family. Although many Wnt antagonists play important roles in renal cell carcinoma (RCC), the molecular function of TIKI2 in human RCC has not been fully elucidated. Here, we analyzed TIKI2 mRNA level in RCC specimens, the corresponding non-tumor tissues, RCC cell lines, and human proximal tubule epithelial cell line HK-2 using qPCR. We demonstrated that TIKI2 was highly expressed in RCC tissue (P < 0.05) and most RCC cell lines. In vitro, TIKI2 knockdown significantly inhibited proliferation, invasion, and clone formation ability of 769-P cells compared with controls, while ectopic TIKI2 expression enhanced A498 cell proliferation, invasion, and clone formation ability. In vivo, the average tumor volume was significantly increased in mice injected with A498-Tiki2 cells (P < 0.05). In the 769-P cell TIKI2 knockdown group, the average tumor volume was not significantly different compared to that of the control group (P = 0.08). Moreover, Wnt/β-catenin signaling was not affected by TIKI2 knockdown or overexpression. Results of the present study indicate that TIKI2 is upregulated in RCC tissues and plays an oncogenic role in RCC.

Role of DNA methylation in renal cell carcinoma

Alterations in DNA methylation are seen in cancers and have also been examined in clear cell renal cell carcinoma (ccRCC). Numerous tumor suppressor genes have been reported to be partially or completely silenced due to hypermethylation of their promoters in single-locus studies, and the use of hypomethylating agents has been shown to restore the expression of many of these genes in vitro. In particular, members of the Wnt and TGF-beta pathways, pro-apoptotic genes such as APAF-1 and negative cell-cycle regulators such as KILLIN have been shown to be epigenetically silenced in numerous studies in ccRCC. Recently, TCGA analysis of a large cohort of ccRCC samples demonstrated that aberrant hypermethylation correlated with the stage and grade in kidney cancer. Our genome-wide studies also revealed aberrant widespread hypermethylation that affected regulatory regions of the kidney genome in ccRCC. We also observed that aberrant enhancer hypermethylation was predictive of adverse prognosis in ccRCC. Recent discovery of mutations affecting epigenetic regulators reinforces the importance of these changes in the pathophysiology of ccRCC and points to the potential of epigenetic modulators in the treatment of this malignancy.

[Construction of pVAX-WIF-1 Eukaryotic Expression Vector and Its Anti-tumor Effect on Lung Cancer]

BACKGROUND AND OBJECTIVE

WIF-1 is an important tumor-suppressing gene in lung cancer, and its encoding protein WIF-1 can reduce proliferation and promote apoptosis by inhibiting Wnt/β-catenin signaling in lung cancer. This study constructs a eukaryotic expression plasmid carrying WIF-1 using FDA-approved clinical plasmid pVAX and explores the anti-tumor effect of pVAX-WIF-1 on A549 lung cancer cells in vitro and vivo.

METHODS

The DNA fragment of human WIF-1 coding sequence was amplified by PCR and was cloned into the multiple cloning sites of eukaryotic expression vector pVAX to construct pVAX-WIF-1. A recombinant plasmid was transfected into lung cancer A549 cells, and the expression of WIF-1 genes was verified by Western blot after transfection. Subsequently, the effect of pVAX-WIF-1 on cell apoptosis and proliferation was identified by MTT assay, staining A549 cells with Hoechst 3235, and flow cytometry. Finally, the A549 subcutaneous xenograft was established to detect the effect of pVAX-WIF-1 on lung tumor growth in vivo.

RESULTS

The results of restriction enzyme digestion, PCR, and sequencing indicated that eukaryotic expression plasmid pVAX-WIF-1 was successfully constructed. The protein expression level of WIF-1 was increased in the transfected A549 cells. Further results showed that transfection with pVAX-WIF-1 significantly inhibited proliferation and promoted apoptosis in A549 cells. Moreover, pVAX-WIF-1 significantly inhibited the tumor growth of the A549 subcutaneous xenograft in vivo.

CONCLUSIONS

The recombinant eukaryotic expression vector pVAX-WIF-1 was successfully constructed. Transfection with pVAX-WIF-1 could significantly inhibit proliferation and promote apoptosis of lung cancer A549 cells and also effectively inhibit the tumor growth of the A549 subcutaneous xenograft in vivo. Our research can contribute to clinical applications of WIF-1 in lung cancer gene therapy.

Genetic polymorphism in extracellular regulators of Wnt signaling pathway

The Wnt signaling pathway is mediated by a family of secreted glycoproteins through canonical and noncanonical mechanism. The signaling pathways are regulated by various modulators, which are classified into two classes on the basis of their interaction with either Wnt or its receptors. Secreted frizzled-related proteins (sFRPs) are the member of class that binds to Wnt protein and antagonizes Wnt signaling pathway. The other class consists of Dickkopf (DKK) proteins family that binds to Wnt receptor complex. The present review discusses the disease related association of various polymorphisms in Wnt signaling modulators. Furthermore, this review also highlights that some of the sFRPs and DKKs are unable to act as an antagonist for Wnt signaling pathway and thus their function needs to be explored more extensively.

Chronic exposure to nanoparticulate TiO2 causes renal fibrosis involving activation of the Wnt pathway in mouse kidney

Chronic exposure to nano-TiO2 may induce renal fibrosis, and the mechanism of this process is not well understood. Therefore, in this study, mice were administered nano-TiO2 by intragastric feeding for 9 months, and the urinary levels of nephrotoxicity biomarkers, activation of the Wnt pathway, and markers of the epithelial-to-mesenchymal transition (EMT) in the kidneys were investigated. The findings suggested that exposure to nano-TiO2 increased the level of renal titanium accumulation, urinary levels of kidney injury molecule-1 (1.18 ± 0.13- to 3.60 ± 0.41-fold), clusterin (1.40 ± 0.16- to 5.14 ± 0.58-fold), and osteopontin (0.71 ± 0.08- to 2.41 ± 0.29-fold), and increased levels of renal inflammation and fibrosis. Furthermore, nano-TiO2 increased the level of expression of Wnt ligands (Wnt1, Wnt2, Wnt3, Wnt4, Wnt5a, Wnt6, Wnt7a, Wnt9a, Wnt10a, and Wnt11, 0.09 ± 0.02- to 4.84 ± 0.52-fold), Wnt receptors Frizzled (Fz1, Fz5, and Fz7, 0.37 ± 0.04- to 8.57 ± 0.91-fold), and coreceptors low-density lipoprotein receptor-related proteins 5 and 6 (0.73 ± 0.09- to 5.27 ± 0.56-fold) in the kidney. Wnt signaling components induced by nano-TiO2 were corroborated by decreased levels of expression of Wnt antagonist-related markers (Dkk1, Dkk2, Dkk3, Dkk4, and sFRP/FrzB, -0.06 ± 0.01- to -0.87 ± 0.09-fold) and increased levels of expression of Wnt target genes (Abcb1b, cyclin D1, and Myc, 0.03 ± 0.01- to 2.73 ± 0.28-fold) and EMT markers Colla1, Fn, Twist, and α-SMA (0.06 ± 0.02- to 5.80 ± 0.61-fold). These findings indicate that nano-TiO2 induced renal fibrosis that may be mediated via Wnt signaling.

Extracellular activation of Wnt signaling through epigenetic dysregulation of Wnt inhibitory factor-1 (Wif-1) is associated with pathogenesis of adrenocortical tumor

Wnt/β-catenin signaling is considered to be an essential regulator of adrenocortical oncogenesis. Wnt inhibitory factor-1 (Wif-1), an extracellular regulator of Wnt signaling, is frequently down-regulated by hypermethylation of the promoter CpG. We investigated epigenetic regulation of Wif-1 and its association with adrenocortical (AC) tumor pathogenesis in light of Wnt activation. The AC tumors showed a high prevalence of Wif-1 promoter methylation and low prevalence of Wif-1 mRNA transcription as compared to the normal adrenal (NA) samples. Furthermore, a significant correlation was found between Wif-1 promoter methylation and mRNA transcription in the tumors. Either intracellular β-catenin accumulation or β-catenin mRNA transcription was significantly elevated in the AC tumors, which also showed an inverse correlation with Wif-1 mRNA transcription. Cyclin D1, a target gene of Wnt signaling, was also up-regulated in the AC tumors as compared with the NA samples. In addition, down-regulation of Wif-1 was correlated with increased cyclin D1 at both mRNA and protein levels. However, despite the proposed activation of Wnt signaling in AC tumors, only 2 of 20 with intracellular β-catenin accumulation showed β-catenin mutations. Thus, genetic alterations of β-catenin and epigenetics-related Wif-1 promoter hypermethylation may be important mechanisms underlying AC tumor formation though aberrant canonical Wnt/β-catenin signaling activation.

Epigenetic markers for noninvasive early detection of nasopharyngeal carcinoma by methylation-sensitive high resolution melting

Nasopharyngeal carcinoma (NPC) is a human malignancy that is closely associated with Epstein-Barr Virus (EBV). Early diagnosis of NPC will greatly improve the overall survival. However, current EBV DNA marker detection still lacks the predictive value to perform well in high-risk populations for early detection of NPC. Since aberrant promoter hypermethylation of tumor suppressor genes (TSGs) is widely considered to be an important epigenetic change in early carcinogenesis, this study identified a panel of methylation markers for early detection of NPC and also assessed the clinical usefulness of these markers with noninvasive plasma specimens instead of biopsies. MS-HRM assays were carried out to assess the methylation status of a selected panel of four TSGs (RASSF1A, WIF1, DAPK1 and RARβ2) in biopsies, NP brushings and cell-free plasma from NPC patients. High-risk and cancer-free groups were used as controls. DNA methylation panel showed higher sensitivity and specificity than EBV DNA marker in cell-free plasma from NPC patients at early Stages (I and II) and in addition to the EBV DNA marker, MS-HRM test for plasma and NP brushing DNA methylation significantly increased the detection rate at all NPC stages as well as local recurrence, using this selected four-gene panel (p<0.05). MS-HRM assay on a selected gene panel has great potential to become a noninvasive and complementary test for NPC early and recurrent detection in combination with the EBV DNA test to increase the sensitivity for NPC detection at an early stage.

Wnt signaling pathway and liver fibrosis: Recent research status

Hepatic fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM), and the activiation of hepatic stellate cells (HSCs) is recognized as the core and initial stage. It is reported that the activiation of HSCs is related to the regulation of a series of cell factors and cell signal pathways. The Wnt signaling pathway plays a key role in the physiology and pathology of the liver, and the abnormal activiation of Wnt results in the activiation of HSCs. Therefore, a further understanding of the role of the Wnt signaling pathway in the pathogeneisis of hepatic fibrosis will be valuable in the development of diagnosic and threputic strategies for this disease.

Wnt inhibitory factor 1 suppresses cancer stemness and induces cellular senescence

Hyperactivation of the Wingless-type (Wnt)/β-catenin pathway promotes tumor initiation, tumor growth and metastasis in various tissues. Although there is evidence for the involvement of Wnt/β-catenin pathway activation in salivary gland tumors, the precise mechanisms are unknown. Here we report for the first time that downregulation of the Wnt inhibitory factor 1 (WIF1) is a widespread event in salivary gland carcinoma ex-pleomorphic adenoma (CaExPA). We also show that WIF1 downregulation occurs in the CaExPA precursor lesion pleomorphic adenoma (PA) and indicates a higher risk of progression from benign to malignant tumor. Our results demonstrate that diverse mechanisms including WIF1 promoter hypermethylation and loss of heterozygosity contribute to WIF1 downregulation in human salivary gland tumors. In accordance with a crucial role in suppressing salivary gland tumor progression, WIF1 re-expression in salivary gland tumor cells inhibited cell proliferation, induced more differentiated phenotype and promoted cellular senescence, possibly through upregulation of tumor-suppressor genes, such as p53 and p21. Most importantly, WIF1 significantly diminished the number of salivary gland cancer stem cells and the anchorage-independent cell growth. Consistent with this observation, WIF1 caused a reduction in the expression of pluripotency and stemness markers (OCT4 and c-MYC), as well as adult stem cell self-renewal and multi-lineage differentiation markers, such as WNT3A, TCF4, c-KIT and MYB. Furthermore, WIF1 significantly increased the expression of microRNAs pri-let-7a and pri-miR-200c, negative regulators of stemness and cancer progression. In addition, we show that WIF1 functions as a positive regulator of miR-200c, leading to downregulation of BMI1, ZEB1 and ZEB2, with a consequent increase in downstream targets such as E-cadherin. Our study emphasizes the prognostic and therapeutic potential of WIF1 in human salivary gland CaExPA. Moreover, our findings demonstrate a novel mechanism by which WIF1 regulates cancer stemness and senescence, which might have major implications in the field of cancer biology.

Coexpression of SFRP1 and WIF1 as a prognostic predictor of favorable outcomes in patients with colorectal carcinoma

Colorectal tumorigenesis is ascribed to the activity of Wnt signaling pathway in a ligand-independent manner mainly through APC and CTNNB1 gene mutations and in a ligand-dependent manner through low expression of Wnt inhibitors such as WNT inhibitory factor 1 (WIF1) and secreted frizzled related protein 1 (SFRP1). In this study we found that WIF1 protein expression was increased and SFRP1 was decreased significantly in CRC tissue versus normal tissue, and high expression of WIF1 was associated with big tumor diameters and deep invasion, and loss of SFRP1 expression was associated with the left lesion site, deep invasion, and high TNM stage. Among the four expression patterns (WIF+/SFRP1+, WIF+/SFRP1−, WIF−/SFRP1+, and WIF−/SFRP1−) only coexpression of WIF1 and SFRP1 (WIF+/SFRP1+) was associated with favorable overall survival, together with low TNM stage, as an independent prognostic factor as shown in a multivariate survival model. The results indicated that WIF1 seemed to play an oncogenic role, while SFRP1 seemed to play an oncosuppressive role although both of them are secreted Wnt antagonists. Coexpression of SFRP1 and WIF1, rather than SFRP1 or WIF1 alone, could be used, together with low TNM stage, as a prognostic predictor of favorable outcomes in CRC.

MicroRNA-181a promotes tumor growth and liver metastasis in colorectal cancer by targeting the tumor suppressor WIF-1

Background

Given the emerging role of microRNA in tumor disease progression, we investigated the association between microRNA expression, liver metastasis and prognosis of colorectal cancer.

Methods

Colorectal cancer tissues from patients with or without liver metastases were profiled to identify differentially expressed microRNA. Expression profile was further assessed using quantitative reverse transcription PCR and in situ hybridization. Correlation between miR-181a expression, the most differentially expressed microRNA, between patients with and without liver metastasis, and its downstream target genes were investigated using qRT-PCR. Luciferase reporter assay was conducted to establish functional association between miR-181a and its target genes. Manipulation of miR-181a expression and its consequences in tumor growth and metastasis were demonstrated in various in vitro and in vivo models.

Results

miR-181a was revealed being the most elevated in CRC with liver metastases. miR-181a expression correlated with advanced stage, distant metastasis, and served as an independent prognostic factor of poor overall survival. Stable transfection of CRC cell lines with miR-181a promoted cell motility and invasion, as well as tumor growth and liver metastasis,while silencing its expression resulted in reduced migration and invasion. Additionally, we identified WIF-1 as direct and functional targets of miR-181a. Ectopic expression of miR-181a suppressed the epithelial markers E-cadherin and β-catenin, while enhanced the mesenchymal markers vimentin.

Conclusion

Our data demonstrate that miR-181a expression is associated with CRC liver metastasis and survival. miR-181a has strong tumor-promoting effects through inhibiting the expression of WIF-1, and its potential role in promoting epithelial-mesenchymal transition.

The epigenetically regulated effects of Wnt antagonists on the expression of genes in the apoptosis pathway in human bladder cancer cell line (T24)

The epigenetic suppression of Wnt antagonists (sFRPs, DKKs, and WIF-1) causes the activation of both β-catenin and target genes, which play an important role in cell proliferation, metastasis, and angiogenesis. This study is aimed to investigate, on transcriptional and protein levels, the synergic effects of unaccompanied and/or combined use of 5-aza-2'-deoxycytidine (DAC, 5-aza-dC), trichostatin A (TSA), and gemcitabine+cisplatin chemotherapeutic agents on the apoptotic pathway of human bladder cancer cell line T24. The anti-tumor effects of gemcitabine (0-500 nM), cisplatin (0-10 μM), DAC (10 μM), and TSA (300 nM) alone and/or together on T24 cells were determined by WST-1. ELISA method was used to analyze the effects of unaccompanied and combined use of gemcitabine+cisplatin, DAC, and TSA on cell proliferation and determine the cytotoxic and apoptotic dosages at the level of H3 histone acetylation. Methylation-specific PCR was used to evaluate methylation profiles of Wnt antagonist gene (WIF-1). In the case of unaccompanied and/or combined use of specified drugs, the variations in the expression levels of CTNNB1, GSK3β, c-MYC, CCND1, CASP-3, CASP-8, CASP-9, BCL2L1, and WIF-1 genes were determined by quantitative real-time PCR. Our results indicate that through inhibition of DNA methylation, expression of β-catenin and Wnt antagonist re-activation and expressions of canonical Wnt/β-catenin pathway target genes, c-myc and cyclin D1 (CCND1), have decreased. In addition, DAC, TSA, and gemcitabine+cisplatin combination caused an increase in GSK3β mRNA levels, which in turn significantly decreased CCND1 mRNA levels. Moreover, BCL2L1, an anti-apoptotic gene, was downregulated significantly. Meanwhile, both CASP-3 mRNA and active caspase-3 protein levels increased with respect to control (p<0.01). The results revealed that use of quadruplicate gemcitabine+cisplatin+DAC+TSA combination led to a reduced inhibition of canonical Wnt/β-catenin pathway and reduced cell proliferation. Our findings may offer a new approach to consider in the treatment of bladder cancer.

Wnt inhibitory factor-1 functions as a tumor suppressor through modulating Wnt/β-catenin signaling in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor in childhood and is associated with serious morbidity and mortality. The effective treatment of neuroblastoma remains one of the major challenges in pediatric oncology. The Wnt signaling pathway has been shown to play a significant role in the pathogenesis of adult and pediatric tumors. WIF-1 has been identified as an important Wnt antagonist which inhibits Wnt/β-catenin signaling by directly binding to Wnt proteins. However, the expression and function of WIF-1 in neuroblastoma remains unknown. The present study showed that WIF-1 was downregulated with high level promoter methylation in neuroblastoma cells, and was significantly upregulated after exposure to demethylating agent. This finding suggests that downregulation of WIF-1 was associated with its promoter methylation in neuroblastoma. To further study the potential function of WIF-1 in neuroblastoma, we constructed a plasmid that over-expressed WIF-1 and transfected the plasmid into one neuroblastoma cell line SK-N-SH. We found that restoration of WIF-1 inhibited the growth and proliferation of neuroblastoma cells in vitro. Moreover, Wnt/β-catenin signaling activity and target genes expression were reduced by WIF-1 restoration. These results provide support that WIF-1 is downregulated and functions as a tumor suppressor by antagonizing Wnt/β-catenin signaling in neuroblastoma, suggesting a potential role as a therapeutic target in neuroblastoma.

DNA methyltransferase inhibitor-mediated apoptosis in the Wnt/β-catenin signal pathway in a renal cell carcinoma cell line

The Wnt signaling pathway is activated in most cancer types when Wnt antagonist genes are inactivated. Glycogen synthase kinase 3 ( GSK3β) is an important regulator of the Wnt/β-catenin signaling pathway. The mechanisms underlying GSK3β regulation of neoplastic transformation and tumor development are unclear. Studies have raised the possibility that the Wnt signaling pathway may be implicated in renal cell carcinoma (RCC). Therefore, in the present study, we hypothesize that the expression and methylation status of the secreted frizzled-related protein 2 ( sFRP2) gene, one of the secreted antagonists that bind Wnt protein, and re-expression of this gene with the demethylation agent (5-aza-2′-deoxycytidine; DAC) may induce apoptosis in RCC cells. To test this hypothesis, we investigated the relationship among epigenetic inactivation of sFRP2 and p-GSK3β (Ser9) and other Wnt antagonists ( sFRP1, DKK3, WIF-1) and apoptotic factors ( Bax and Caspase3) as well as the anti-apoptotic factor BCL2. Our results indicate that DAC-mediated inhibition of DNA methylation led to a re-activation of sFRP2 expression and increased expression levels of the Wnt antagonists and apoptotic factors. In contrast, the level of β-catenin (CTNNB1) expression decreased. The p-GSK3β (Ser9) protein level in Caki-2 cells was significantly down-regulated, while the DNA fragmentation rate increased after treatment with 5 μM DAC at 96 h. Our data show that sFRP2 functions as a tumor suppressor gene in RCC and that its restoration may offer a new therapeutic approach for the treatment of RCC. Moreover, our study draws attention to the regulatory features of epigenetic molecules and analyses their underlying molecular mechanisms of action and their potential use in clinical practice.

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.

Promoter methylation of WNT inhibitory factor-1 and expression pattern of WNT/β-catenin pathway in human astrocytoma: pathologic and prognostic correlations

WNT inhibitory factor-1 (WIF1) is an antagonist of the WNT signaling pathway. We investigated the relationship between WIF1 promoter methylation and regulation of the WNT/β-catenin signaling pathway, tumor grade, and survival in patients with astrocytoma. This study included 86 cases of astrocytoma, comprising 20 diffuse astrocytomas and 66 glioblastomas. In addition, 17 temporal lobectomy specimens from patients with epilepsy were included as controls. The ratio of methylated DNA to total methylated and unmethylated DNA (% methylation) was measured by methylation- and unmethylation-specific PCR. Representative tumor tissue was immunostained for WIF1, β-catenin, cyclin D1, c-myc, and isocitrate dehydrogenase 1. Levels of WIF1 promoter methylation, mRNA expression, and protein expression in a glioblastoma cell line were compared before and after demethylation treatment. The mean percent methylation of the WIF1 promoter in astrocytomas was higher than that in control brain tissue. WIF1 protein expression was lower in the tumor group with >5% methylation than in the group with <5% methylation. Cytoplasmic β-catenin staining was more frequently observed in tumors with a low WIF1 protein expression level. Demethylation treatment of a glioblastoma cell line increased WIF1 mRNA and protein expression. Increased WIF1 promoter methylation and decreased WIF1 protein expression were not related to patient survival. In conclusion, WIF1 expression is downregulated by promoter methylation and is an important mechanism of aberrant WNT/β-catenin pathway activation in astrocytoma pathogenesis.

The way Wnt works: components and mechanism

The canonical Wnt/β-catenin pathway is an ancient and evolutionarily conserved signaling pathway that is required for the proper development of all metazoans, from the basal demosponge Amphimedon queenslandica to humans. Misregulation of Wnt signaling is implicated in many human diseases, making this pathway an intense area of research in industry as well as academia. In this review, we explore our current understanding of the molecular steps involved in the transduction of a Wnt signal. We will focus on how the critical Wnt pathway component, β-catenin, is in a "futile cycle" of constant synthesis and degradation and how this cycle is disrupted upon pathway activation. We describe the role of the Wnt pathway in major human cancers and in the control of stem cell self-renewal in the developing organism and in adults. Finally, we describe well-accepted criteria that have been proposed as evidence for the involvement of a molecule in regulating the canonical Wnt pathway.

WNT10A plays an oncogenic role in renal cell carcinoma by activating WNT/β-catenin pathway

Renal cell carcinoma (RCC) is a malignancy with poor prognosis. WNT/β-catenin signaling dysregulation, especially β-catenin overactivation and WNT antagonist silencing, is associated with RCC carcinogenesis and progression. However, the role of WNT ligands in RCC has not yet been determined. We screened 19 WNT ligands from normal kidney and RCC cell lines and tissues and found that WNT10A was significantly increased in RCC cell lines and tissues as compared to that in normal controls. The clinical significance of increase in WNT10A was evaluated by performing an immunohistochemical association study in a 19-year follow-up cohort comprising 284 RCC and 267 benign renal disease (BRD) patients. The results of this study showed that WNT10A was dramatically upregulated in RCC tissues as compared to that in BRD tissues. This result suggests that WNT10A, nuclear β-catenin, and nuclear cyclin D1 act as independent risk factors for RCC carcinogenesis and progression, with accumulative risk effects. Molecular validation of cell line models with gain- or loss-of-function designs showed that forced WNT10A expression induced RCC cell proliferation and aggressiveness, including higher chemoresistance, cell migration, invasiveness, and cell transformation, due to the activation of β-catenin-dependent signaling. Conversely, WNT10A siRNA knockdown decreased cell proliferation and aggressiveness of RCC cells. In conclusion, we showed that WNT10A acts as an autocrine oncogene both in RCC carcinogenesis and progression by activating WNT/β-catenin signaling.

Comparison of different normalization assumptions for analyses of DNA methylation data from the cancer genome

Nowadays, some researchers normalized DNA methylation arrays data in order to remove the technical artifacts introduced by experimental differences in sample preparation, array processing and other factors. However, other researchers analyzed DNA methylation arrays without performing data normalization considering that current normalizations for methylation data may distort real differences between normal and cancer samples because cancer genomes may be extensively subject to hypomethylation and the total amount of CpG methylation might differ substantially among samples. In this study, using eight datasets by Infinium HumanMethylation27 assay, we systemically analyzed the global distribution of DNA methylation changes in cancer compared to normal control and its effect on data normalization for selecting differentially methylated (DM) genes. We showed more differentially methylated (DM) genes could be found in the Quantile/Lowess-normalized data than in the non-normalized data. We found the DM genes additionally selected in the Quantile/Lowess-normalized data showed significantly consistent methylation states in another independent dataset for the same cancer, indicating these extra DM genes were effective biological signals related to the disease. These results suggested normalization can increase the power of detecting DM genes in the context of diagnostic markers which were usually characterized by relatively large effect sizes. Besides, we evaluated the reproducibility of DM discoveries for a particular cancer type, and we found most of the DM genes additionally detected in one dataset showed the same methylation directions in the other dataset for the same cancer type, indicating that these DM genes were effective biological signals in the other dataset. Furthermore, we showed that some DM genes detected from different studies for a particular cancer type were significantly reproducible at the functional level.

Role of canonical Wnt signaling in endometrial carcinogenesis

While the role of Wnt signaling is well established in colorectal carcinogenesis, its function in gynecologic cancers has not been elucidated. Here, we describe the current state of knowledge of canonical Wnt signaling in endometrial cancer (EC), and its implications for future therapeutic targets. Deregulation of the Wnt/β-catenin signaling pathway in EC occurs by inactivating β-catenin mutations in approximately 10-45% of ECs, and via downregulation of Wnt antagonists by epigenetic silencing. The Wnt pathway is intimately involved with estrogen and progesterone, and emerging data implicate it in other important signaling pathways, such as mTOR and Hedgehog. While no therapeutic agents targeting the Wnt signaling pathway are currently in clinical trials, the preclinical data presented suggest a role for Wnt signaling in uterine carcinogenesis, with further research warranted to elucidate the mechanism of action and to proceed towards targeted cancer drug development.

Expression of the Wnt antagonist Dickkopf-3 is associated with prognostic clinicopathologic characteristics and impairs proliferation and invasion in endometrial cancer

OBJECTIVE

Emerging evidence implicates the Wnt antagonist Dickkopf-3 (Dkk3) as a tumor suppressor and potential biomarker in solid tumors. We investigated whether Dkk3 plays an important role in the carcinogenesis of endometrial cancer (EC).

METHODS

We analyzed Dkk3 mRNA expression via real-time RT-PCR in twenty-seven human primary EC tissues, and six matched normal endometrial controls. Dkk3 levels were correlated with various clinicopathologic characteristics. Additionally, enforced Dkk3 expression was examined in proliferation and tumorigenesis in vitro and in vivo, using MTT, soft agar assay, invasion assay, a xenograft mouse model, and a β-catenin-responsive SuperTopFlash luciferase assay.

RESULTS

Compared with matched normal endometrial cases, Dkk3 was down-regulated in EC (p<0.0001). Among cancer cases, Dkk3 expression was significantly reduced in patients with higher stage (p=0.002), positive pelvic lymph nodes (p=0.0004), non-endometrioid histology (p=0.02), and cytology-positive ECs (p=0.02). Enforced expression of Dkk3 in EC cell lines showed reduced proliferation (p<0.0001), anchorage-independent growth (p=0.005), invasion (p=0.02), and reduced TCF activity (p=0.04), confirming Dkk3 as a negative regulator of the β-catenin/Wnt signaling pathway. Tumor growth in Dkk3-injected mice was not statistically different, though did plateau towards the end, and was associated with increased lymphoid infiltration and tumor necrosis.

CONCLUSION

Dkk3 gene expression is frequently downregulated in endometrial cancer, and is associated with poor prognostic clinicopathologic markers. The results also identify a role for Dkk3 as a tumor suppressor in EC, affecting both proliferation and invasiveness. These findings may prove to be important in the design of novel biomarkers and treatment modalities for advanced EC.

Wnt signaling pathways in urological cancers: past decades and still growing

The Wnt signaling pathway is involved in a wide range of embryonic patterning events and maintenance of homeostasis in adult tissues. The pathological role of the Wnt pathway has emerged from studies showing a high frequency of specific human cancers associated with mutations that constitutively activate the transcriptional response of these pathways. Constitutive activation of the Wnt signaling pathway is a common feature of solid tumors and contributes to tumor development, progression and metastasis in various cancers. In this review, the Wnt pathway will be covered from the perspective of urological cancers with emphasis placed on the recent published literature. Regulation of the Wnt signaling pathway by microRNAs (miRNA), small RNA sequences that modify gene expression profiles will also be discussed. An improved understanding of the basic genetics and biology of Wnt signaling pathway will provide insights into the development of novel chemopreventive and therapeutic strategies for urological cancers.

The complex roles of Wnt antagonists in RCC

Renal cell carcinoma (RCC) is the most lethal of all the genitourinary cancers, as it is generally refractory to current treatment regimens, including chemotherapy and radiation therapy. Targeted therapies against critical signaling pathways associated with RCC pathogenesis, such as vascular endothelial growth factor, von Hippel-Lindau tumor suppressor and mammalian target of rapamycin, have shown limited efficacy so far. Thus, Wnt signaling, which is known to be intricately involved in the pathogenesis of RCC, has attracted much interest. Several Wnt signaling components have been examined in RCC, and, while studies suggest that Wnt signaling is constitutively active in RCC, the molecular mechanisms differ considerably from other human carcinomas. Increasing evidence indicates that secreted Wnt antagonists have important roles in RCC pathogenesis. Considering these vital roles, it has been postulated--and supported by experimental evidence--that the functional loss of Wnt antagonists, for example by promoter hypermethylation, can contribute to constitutive activation of the Wnt pathway, resulting in carcinogenesis through dysregulation of cell proliferation and differentiation. However, subsequent functional studies of these Wnt antagonists have demonstrated the inherent complexities underlying their role in RCC pathogenesis.

Wnt inhibitory factor 1 induces apoptosis and inhibits cervical cancer growth, invasion and angiogenesis in vivo

Aberrant activation of Wingless-type (Wnt)/β-catenin signaling is widespread in human cervical cancer. However, the underlying mechanisms of Wnt activation and the therapeutic potential of Wnt inhibition remain largely unknown. Here, we demonstrate that the Wnt inhibitory factor 1 (WIF1), a secreted Wnt antagonist, is downregulated in all human primary cervical tumors and cell lines analyzed. Our data reveal that WIF1 downregulation occurs due to promoter hypermethylation and is an early event in cervical oncogenesis. WIF1 re-expression upon 5-aza-2'-deoxycytidine treatment or WIF1 gene transfer induces significant apoptosis and G(2)/M arrest, and inhibits cervical cancer cell proliferation in vitro. Consistent with this, treatment of established mice tumor xenografts with peritumoral WIF1 gene transfer results in a significant inhibition of cancer growth and invasion. WIF1 treatment causes a significant decrease in intracellular WNT1 and TCF-4 proteins revealing novel Wnt-regulatory mechanisms. Thus, WIF1 causes a major cellular re-distribution of β-catenin and a significant inhibition of the Wnt/β-catenin pathway in tumor cells, as documented by a remarkable reversion in the expression of Wnt/β-catenin transcriptional target genes (E-cadherin, c-Myc, cyclin D1, CD44 and VEGF). Consequently, multiple critical events in tumor progression and metastasis such as cell proliferation, angiogenesis and invasion were inhibited by WIF1. In addition, WIF1 modulated the expression of specific anti-apoptotic and apoptotic proteins, thereby inducing significant apoptosis in vivo. Our findings demonstrate for the first time that WIF1 downregulation by epigenetic gene silencing is an important mechanism of Wnt activation in cervical oncogenesis. Of major clinical relevance, we show that peritumoral WIF1 gene transfer reduces not only cancer growth but also invasion in well-established tumors. Therefore, our data provide novel mechanistic insights into the role of WIF1 in cervical cancer progression, and the important preclinical validation of WIF1 as a potent drug target in cervical cancer treatment.

Aberrant activation of Wnt/β-catenin signaling pathway contributes to the sequential progression of DMBA-induced HBP carcinomas

Wnt signaling pathway mediated via interactions between β-catenin and members of the TCF/LEF-1 family of transcription factors plays a central role in the regulation of epithelial cell proliferation, apoptosis, differentiation, adhesion, epithelial-mesenchymal transition, and invasion. Aberrant activation of the Wnt/β-catenin signaling pathway with overexpression of Wnt and Fz, mutations of APC, β-catenin, and axin 1, and cytoplasmic accumulation of β-catenin have been frequently reported in a broad spectrum of human malignancies including oral squamous cell carcinomas (OSCCs). However, changes in the components of the Wnt signaling pathway have not been documented during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis, a paradigm for oral oncogenesis and chemointervention. In this study, we evaluated the role of β-catenin accumulation and Wnt ligands, Wnt signaling members (Fz, Dvl, APC, GSK-3β, axin, and WIF) and the downstream targets of Wnt (cyclin D1, MMP-2, and MMP-9) during the sequential progression of DMBA-induced HBP carcinomas by semi-quantitative RT-PCR and western blot analyses. Our data reveal a correlation between β-catenin accumulation and activation of Wnt signaling, and its downstream effector molecules during the sequential development of HBP carcinomas from hyperplasia to invasive carcinoma through dysplasia. Our data also support a pivotal role for β-catenin in the malignant transition of the HBP. Aberrant Wnt signaling may be a hallmark of progression to malignancy during DMBA-induced HBP carcinogenesis and could be a potential preventive and therapeutic target for suppression of OSCC.