Molecular analysis of WWOX expression correlation with proliferation and apoptosis in glioblastoma multiforme

Molecular landscapes of glioblastoma cell lines revealed a group of patients that do not benefit from WWOX tumor suppressor expression

Introduction

Glioblastoma (GBM) is notorious for its clinical and molecular heterogeneity, contributing to therapeutic failure and a grim prognosis. WWOX is one of the tumor suppressor genes important in nervous tissue or related pathologies, which was scarcely investigated in GBM for reliable associations with prognosis or disease progression despite known alterations. Recently, we observed a phenotypic heterogeneity between GBM cell lines (U87MG, T98G, U251MG, DBTRG-05MG), among which the anti-GBM activity of WWOX was generally corresponding, but colony growth and formation were inconsistent in DBTRG-05MG. This prompted us to investigate the molecular landscapes of these cell lines, intending to translate them into the clinical context.

Methods

U87MG/T98G/U251MG/DBTRG-05MG were subjected to high-throughput sequencing, and obtained data were explored via weighted gene co-expression network analysis, differential expression analysis, functional annotation, and network building. Following the identification of the most relevant DBTRG-distinguishing driver genes, data from GBM patients were employed for, e.g., differential expression analysis, survival analysis, and principal component analysis.

Results

Although most driver genes were unique for each cell line, some were inversely regulated in DBTRG-05MG. Alongside driver genes, the differentially-expressed genes were used to build a WWOX-related network depicting protein-protein interactions in U87MG/T98G/U251MG/DBTRG-05MG. This network revealed processes distinctly regulated in DBTRG-05MG, e.g., microglia proliferation or neurofibrillary tangle assembly. POLE4 and HSF2BP were selected as DBTRG-discriminating driver genes based on the gene significance, module membership, and fold-change. Alongside WWOX, POLE4 and HSF2BP expression was used to stratify patients into cell lines-resembling groups that differed in, e.g., prognosis and treatment response. Some differences from a WWOX-related network were certified in patients, revealing genes that clarify clinical outcomes. Presumably, WWOX overexpression in DBTRG-05MG resulted in expression profile change resembling that of patients with inferior prognosis and drug response. Among these patients, WWOX may be inaccessible for its partners and does not manifest its anti-cancer activity, which was proposed in the literature but not regarding glioblastoma or concerning POLE4 and HSF2BP.

Conclusion

Cell lines data enabled the identification of patients among which, despite high expression of WWOX tumor suppressor, no advantageous outcomes were noted due to the cancer-promoting profile ensured by other genes.

Inflammation-targeted nanomedicine against brain cancer: From design strategies to future developments

Brain cancer is an aggressive type of cancer with poor prognosis. While the immune system protects against cancer in the early stages, the tumor exploits the healing arm of inflammatory reactions to accelerate its growth and spread. Various immune cells penetrate the developing tumor region, establishing a pro-inflammatory tumor milieu. Additionally, tumor cells may release chemokines and cytokines to attract immune cells and promote cancer growth. Inflammation and its associated mechanisms in the progression of cancer have been extensively studied in the majority of solid tumors, especially brain tumors. However, treatment of the malignant brain cancer is hindered by several obstacles, such as the blood-brain barrier, transportation inside the brain interstitium, inflammatory mediators that promote tumor growth and invasiveness, complications in administering therapies to tumor cells specifically, the highly invasive nature of gliomas, and the resistance to drugs. To resolve these obstacles, nanomedicine could be a potential strategy that has facilitated advancements in diagnosing and treating brain cancer. Due to the numerous benefits provided by their small size and other features, nanoparticles have been a prominent focus of research in the drug-delivery field. The purpose of this article is to discuss the role of inflammatory mediators and signaling pathways in brain cancer as well as the recent advances in understanding the nano-carrier approaches for enhancing drug delivery to the brain in the treatment of brain cancer.

ErbB4 in the brain: Focus on high grade glioma

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases (RTKs) consists of EGFR, ErbB2, ErbB3, and ErbB4. These receptors play key roles in cell proliferation, angiogenesis, cell migration, and in some cases, tumor promotion. ErbB4 is a unique member of the EGFR family, implicated not only in pro-tumorigenic mechanisms, such as cell proliferation and migration, but also in anti-tumorigenic activities, including cell differentiation and apoptosis. ErbB4 is differentially expressed in a wide variety of tissues, and interestingly, as different isoforms that result in vastly different signalling outcomes. Most studies have either ignored the presence of these isoforms or used overexpression models that may mask the true function of ErbB4. ErbB4 is widely expressed throughout the body with significant expression in skeletal tissue, mammary glands, heart, and brain. Knockout models have demonstrated embryonic lethality due to disrupted heart and brain development. Despite high expression in the brain and a critical role in brain development, remarkably little is known about the potential signalling activity of ErbB4 in brain cancer.This review focuses on the unique biology of ErbB4 in the brain, and in particular, highlights brain cancer research findings. We end the review with a focus on high grade gliomas, primarily glioblastoma, a disease that has been shown to involve EGFR and its mutant forms. The role of the different ErbB4 isotypes in high grade gliomas is still unclear and future research will hopefully shed some light on this question.

WWOX and metabolic regulation in normal and pathological conditions

WW domain-containing oxidoreductase (WWOX) spans the common fragile site FRA16D. There is evidence that translocations and deletions affecting WWOX accompanied by loss of expression are frequent in many cancers and often correlate with a worse prognosis. Additionally, WWOX germline mutations were also found to be the cause of pathologies of brain development. Because WWOX binds to some transcription factors, it is a modulator of many cellular processes, including metabolic processes. Recently, studies have linked WWOX to familial dyslipidemias, osteopenia, metabolic syndrome, and gestational diabetes, confirming its role as a regulator of steroid, cholesterol, glucose, and normal bone metabolism. The WW domain of WWOX is directly engaged in the control of the activity of transcription factors such as HIF1α and RUNX2; therefore, WWOX gene alterations are associated with some metabolic abnormalities. Presently, most interest is devoted to the associations between WWOX and glucose and basic energy metabolism disturbances. In particular, its involvement in the initiation of the Warburg effect in cancer or gestational diabetes and type II diabetes is of interest. This review is aimed at systematically and comprehensively presenting the current state of knowledge about the participation of WWOX in the metabolism of healthy and diseased organisms.

The WWOX gene in brain development and pathology

Shortly after its discovery in 2000, WWOX was hailed as a tumor suppressor gene. In subsequent years of research, this function was confirmed indisputably. Majority of tumors show high rate of loss of heterozygosity and decreased expression of WWOX. Nevertheless, over the years, the range of its known functions, at the cellular, organ and system levels, has expanded to include metabolism and endocrine system control and CNS differentiation and functioning. Despite of its function as a tumor suppressor gene, WWOX genetic alternations were found in a number of metabolic and neural diseases. A lack of WWOX protein as a consequence of germline mutations results in brain development disturbances and malfunctions.

Primary glioblastoma transcriptome data analysis for screening survival-related genes

PURPOSE

The aim of this study was to screen survival-related genes for glioblastoma (GBM).

METHODS

GSE53733 was downloaded from Gene Expression Omnibus (GEO) database, including 16 short-term (ST), 31 intermediate (IM), and 23 long-term (LT) survivors. Analysis of variance was used to analyze the expression in three groups. The genes with P < .01 were screened as differentially expressed genes (DEGs). Soft clustering was performed using Mfuzz to mine the expression patterns of differential genes in three groups of overall survival (OS) classification. The cytoscape plugin clueGO was used for functional enrichment analysis. The protein interaction between differential genes was extracted from the STRING V10 database, and the protein-protein interaction (PPI) network was constructed and displayed with cytoscape. The hub genes were verified by quantitative reverse-transcription polymerase chain reaction.

RESULTS

Total 662 DEGs were obtained among three groups and enriched in 12 clusters. The overlap analysis between clusters could classify these 12 clusters Cluster A and B. Total 264 OS.DEGs were contained in Cluter A and Cluster B, and enriched in 28 Gene Ontology terms, such as trophoblast giant cell differentiation (P value = 6.18E-04), muscle fiber development (P value = 9.09E-04), and negative regulation of stem cell differentiation (P value = 1.76E-03). The top five nodes with highest degree in OS.PPI were HDAC1, DECR1, RASL11A, PDIA3, and POLR2F. The expression of DECR1 and POLR2F was significantly lower, while the levels of HDAC1 and PDIA3 were highly expressed in GBM tissues.

CONCLUSION

DECR1, POLR2F, HDAC1, and PDIA3 might be potential key genes affected the overall survival time of patients with GBM.

The WWOX Gene Influences Cellular Pathways in the Neuronal Differentiation of Human Neural Progenitor Cells

The brain is the most functionally organized structure of all organs. It manages behavior, perception and higher cognitive functions. The WWOX gene is non-classical tumor suppressor gene, which has been shown to have an impact on proliferation, apoptosis and migration processes. Moreover, genetic aberrations in WWOX induce severe neuropathological phenotypes in humans and rodents. The aim of the present study was to investigate in detail the impact of WWOX on human neural progenitor cell (hNPC) maintenance and how depletion of WWOX disturbs signaling pathways playing a pivotal role in neuronal differentiation and central nervous system (CNS) organogenesis. hNPC with a silenced WWOX gene exhibited lowered mitochondrial redox potential, enhanced adhesion to fibronectin and extracellular matrix protein mixture, downregulation of MMP2/9 expression and impaired 3D growth. Global transcriptome analysis using cap analysis of gene expression (CAGE) found that WWOX downregulation significantly changes the expression of multiple genes engaged in cytoskeleton organization, adhesion, cell signaling and chromatin remodeling. The massive changes in gene expression caused by WWOX silencing may strongly affect the differentiation and migration of neurons in organogenesis, brain injury, cancerogenesis or neurodifferentiation. WWOX gene appears to be an important regulator of neural tissue architecture and function.

WWOX Tumor Suppressor Gene in Breast Cancer, a Historical Perspective and Future Directions

The WWOX tumor suppressor gene is located at 16q23. 1–23.2, which covers the region of FRA16D—a common fragile sites. Deletions within the WWOX coding sequence are observed in up to 80% of breast cancer cases, which makes it one of the most common genetic alterations in this tumor type. The WWOX gene is known to play a role in breast cancer: increased expression of WWOX inhibits cell proliferation in suspension, reduces tumor growth rates in xenographic transplants, but also enhances cell migration through the basal membrane and contributes to morphological changes in 3D matrix-based cell cultures. The WWOX protein may act in several ways, as it has three functional domains—two WW domains, responsible for protein-protein interactions and an SDR domain (short dehydrogenase/reductase domain) which catalyzes conversions of low molecular weight ligands, most likely steroids. In epithelial cells, WWOX modulates gene transcription through interaction with p73, AP-2γ, and ERBB4 proteins. In steroid hormone-regulated tissues like mammary gland epithelium, the WWOX SDR domain acts as a steroid dehydrogenase. The relationship between WWOX and hormone receptors was shown in an animal model, where WWOX(C3H)+/–mice exhibited loss of both ER and PR receptors. Moreover, in breast cancer specimens, a positive correlation was observed between WWOX expression and ER status. On the other hand, decreased WWOX expression was associated with worse prognosis, namely higher relapse and mortality rates in BC patients. Recently, it was shown that genomic instability might be driven by the loss of WWOX expression. It was reported that WWOX plays role in DNA damage response (DDR) and DNA repair by regulating ATM activation through physical interaction. A genome caretaker function has also been proposed for WWOX, as it was found that WWOX sufficiency decreases homology directed repair (HDR) and supports non-homologous end-joining (NHEJ) repair as the dominant DSB repair pathway by Brca1-Wwox interaction. In breast cancer cells, WWOX was also found to modulate the expression of glycolysis pathway genes, through hypoxia-inducible transcription factor 1α (HIF1α) regulation. The paper presents the current state of knowledge regarding the WWOX tumor suppressor gene in breast cancer, as well as future research perspectives.

An update on the epigenetics of glioblastomas

Glioblastomas, also known as glioblastoma multiforme (GBM), are the most aggressive and malignant type of primary brain tumor in adults, exhibiting notable variability at the histopathological, genetic and epigenetic levels. Recently, epigenetic alterations have emerged as a common hallmark of many tumors, including GBM. Considering that a deeper understanding of the epigenetic modifications that occur in GBM may increase the knowledge regarding the tumorigenesis, progression and recurrence of this disease, in this review we discuss the recent major advances in GBM epigenetics research involving histone modification, glioblastoma stem cells, DNA methylation, noncoding RNAs expression, including their main alterations and the use of epigenetic therapy as a valid option for GBM treatment.

Tumor Suppressor WWOX Contributes to the Elimination of Tumorigenic Cells in Drosophila melanogaster

WWOX is a >1Mb gene spanning FRA16D Common Chromosomal Fragile Site, a region of DNA instability in cancer. Consequently, altered WWOX levels have been observed in a wide variety of cancers. In vitro studies have identified a large number and variety of potential roles for WWOX. Although its normal role in vivo and functional contribution to cancer have not been fully defined, WWOX does have an integral role in metabolism and can suppress tumor growth. Using Drosophila melanogaster as an in vivo model system, we find that WWOX is a modulator of TNFα/Egr-mediated cell death. We found that altered levels of WWOX can modify phenotypes generated by low level ectopic expression of TNFα/Egr and this corresponds to altered levels of Caspase 3 activity. These results demonstrate an in vivo role for WWOX in promoting cell death. This form of cell death is accompanied by an increase in levels of reactive oxygen species, the regulation of which we have previously shown can also be modified by altered WWOX activity. We now hypothesise that, through regulation of reactive oxygen species, WWOX constitutes a link between alterations in cellular metabolism observed in cancer cells and their ability to evade normal cell death pathways. We have further shown that WWOX activity is required for the efficient removal of tumorigenic cells from a developing epithelial tissue. Together these results provide a molecular basis for the tumor suppressor functions of WWOX and the better prognosis observed in cancer patients with higher levels of WWOX activity. Understanding the conserved cellular pathways to which WWOX contributes provides novel possibilities for the development of therapeutic approaches to restore WWOX function in cancer.

The role of WWOX tumor suppressor gene in the regulation of EMT process via regulation of CDH1-ZEB1-VIM expression in endometrial cancer

This study defines the role of WWOX in the regulation of epithelial to mesenchymal transition. A group of 164 endometrial adenocarcinoma patients was studied as well as an ECC1 well-differentiated steroid-responsive endometrial cell line, which was transducted with WWOX cDNA by a retroviral system. The relationship between WWOX gene and EMT marker (CDH1, VIM, ZEB1, SNAI1) expression on mRNA (RT-qPCR) and protein levels (western blotting) was evaluated. The EMT processes were also analysed in vitro by adhesion of cells to extracellular matrix proteins, migration through a basement membrane, anchorage-independent growth and MMP activity assay. DNA microarrays (HumanOneArray™) were used to determine WWOX-dependent pathways in an ECC1 cell line. A positive correlation was observed between WWOX and ZEB1, and a negative correlation between CDH1 and VIM. WWOX expression was found to inversely correlate with the risk of recurrence of tumors in patients. However, in the WWOX-expressing ECC1 cell line, WWOX expression was found to be inversely related with VIM and positively with CDH1. The ECC1/WWOX cell line variant demonstrated increased migratory capacity, with increased expression of metalloproteinases MMP2/MMP9. However, these cells were not able to form colonies in suspension and revealed decreased adhesion to fibronectin and fibrinogen. Microarray analysis demonstrated that WWOX has an impact on the variety of cellular pathways including the cadherin and integrin signalling pathways. Our results suggest that the WWOX gene plays a role in the regulation of EMT processes in endometrial cancer by controlling the expression of proteins associated with cell motility, thus influencing tissue remodeling, with the suppression of mesenchymal markers.

WWOX: a fragile tumor suppressor

WWOX, the WW domain-containing oxidoreductase gene at chromosome region 16q23.3-q24.1, spanning chromosomal fragile site FRA16D, encodes the 46 kDa Wwox protein, a tumor suppressor that is lost or reduced in expression in a wide variety of cancers, including breast, prostate, ovarian, and lung. The function of Wwox as a tumor suppressor implies that it serves a function in the prevention of carcinogenesis. Indeed, in vitro studies show that Wwox protein interacts with many binding partners to regulate cellular apoptosis, proliferation, and/or maturation. It has been reported that newborn Wwox knockout mice exhibit nascent osteosarcomas while Wwox(+/-) mice exhibit increased incidence of spontaneous and induced tumors. Furthermore, absence or reduction of Wwox expression in mouse xenograft models results in increased tumorigenesis, which can be rescued by Wwox re-expression, though there is not universal agreement among investigators regarding the role of Wwox loss in these experimental models. Despite this proposed tumor suppressor function, the overlap of the human WWOX locus with FRA16D sensitizes the gene to protein-inactivating deletions caused by replication stress. The high frequency of deletions within the WWOX locus in cancers of various types, without the hallmark protein inactivation-associated mutations of "classical" tumor suppressors, has led to the proposal that WWOX deletions in cancers are passenger events that occur in early cancer progenitor cells due to fragility of the genetic locus, rather than driver events which provide the cancer cell a selective advantage. Recently, a proposed epigenetic cause of chromosomal fragility has suggested a novel mechanism for early fragile site instability and has implications regarding the involvement of tumor suppressor genes at chromosomal fragile sites in cancer. In this review, we provide an overview of the evidence for WWOX as a tumor suppressor gene and put this into the context of fragility associated with the FRA16D locus.

Alteration of WWOX in human cancer: a clinical view

WWOX gene is located in FRA16D, the highly affected chromosomal fragile site. Its tumor suppressor activity has been proposed on a basis of numerous genomic alterations reported in chromosome 16q23.3-24.1 locus. WWOX is affected in many cancers, showing as high as 80% loss of heterozygosity in breast tumors. Unlike most tumor suppressors impairing of both alleles of WWOX is very rare. Despite cellular and animal models information on a WWOX role in cancer tissue is limited and sometimes confusing. This review summarizes information on WWOX in human tumors.

Alternating expression levels of WWOX tumor suppressor and cancer-related genes in patients with bladder cancer

The aim of the present study was to determine the roles of the WWOX tumor suppressor and cancer-related genes in bladder tumor carcinogenesis. Reverse transcription-quantitative polymerase chain reaction was used to analyze the status of WWOX promoter methylation (using MethylScreen™ technology) and loss of heterozygosity (LOH) in papillary urothelial cancer tissues. The associations between the expression levels of the following tumorigenesis-related genes were also assessed: The WWOX tumor suppressor gene, the MKI67 proliferation gene, the BAX, BCL2 and BIRC5 apoptotic genes, the EGFR signal transduction gene, the VEGF vascular endothelial growth factor gene, and the CCND1 and CCNE1 cell cycle genes. The results reveal a high frequency of LOH in intron 1 in the WWOX gene, as well as an association between reduced WWOX expression levels and increased promoter methylation. In addition, the present study demonstrates that in bladder tumors, apoptosis is inhibited by increased expression levels of the BCL2 gene. A correlation between the proliferation indices of the MKI67 and the BIRC5 genes was also revealed. Furthermore, the expression levels of VEGF were identified to be positively associated with those of the EGFR gene.

WWOX modulates the gene expression profile in the T98G glioblastoma cell line rendering its phenotype less malignant

The aim of the present study was to assess the influence of WWOX gene upregulation on the transcriptome and phenotype of the T98G glioblastoma cell line. The cells with high WWOX expression demonstrated a significantly different transcription profile for approximately 3,000 genes. The main cellular pathways affected were Wnt, TGFβ, Notch and Hedgehog. Moreover, the WWOX-transfected cells proliferated at less than half the rate, exhibited greatly lowered adhesion to ECM, increased apoptosis and impaired 3D culture formation. They also demonstrated an increased ability for crossing the basement membrane. Our results indicate that WWOX, apart from its tumor-suppressor function, appears to be a key regulator of the main cellular functions of the cell cycle and apoptosis. Furthermore, our results showed that WWOX may be involved in controlling metabolism, cytoskeletal structure and differentiation.

Diverse effect of WWOX overexpression in HT29 and SW480 colon cancer cell lines

WW-domain-containing oxidoreductase (WWOX) is the tumour suppressor gene from the common fragile site FRA16D, whose altered expression has been observed in tumours of various origins. Its suppressive role and influence on basic cellular processes such as proliferation and apoptosis have been confirmed in many in vitro and in vivo studies. Moreover, its protein is thought to take part in the regulation of tissue morphogenesis and cell differentiation. However, its role in colon cancer formation remains unclear. The aim of this study was to characterize the influence of WWOX on the process of colon cancerogenesis, the basic features of the cancer cell and its expression profiles. Multiple biological tests, microarray experiments and quantitative reverse transcriptase (RT)-PCR were performed on two colon cancer cell lines, HT29 and SW480, which differ in morphology, expression of differentiation markers, migratory characteristics and metastasis potential and which represent negative (HT29) and low (SW480) WWOX expression levels. The cell lines were subjected to retroviral transfection, inducting WWOX overexpression. WWOX was found to have diverse effects on proliferation, apoptosis and the adhesion potential of modified cell lines. Our observations suggest that in the HT29 colon cancer cell line, increased expression of WWOX may result in the transition of cancer cells into a more normal colon epithelium phenotype, while in SW480, WWOX demonstrated well-known tumour suppressor properties. Our results also suggest that WWOX does not behave as classical tumour suppressor gene, and its influence on cell functioning is more global and complicated.

WW domain-containing oxidoreductase's role in myriad cancers: clinical significance and future implications

The WW domain-containing oxidoreductase (WWOX) gene, encodes a tumor suppressor located on 16q23.1, spanning FRA16D, one of the most active common fragile sites in the human genome, that is altered in numerous types of cancer. WWOX's alteration in these myriad cancers is due to disparate mechanisms including loss of heterozygosity, homozygous deletion and epigenetic changes. In vitro, WWOX has been found to be reduced or absent in numerous cancer cell lines and WWOX restoration has been found to inhibit tumor cell growth and invasion. Wwox knockout mice developed femoral focal lesions resembling osteosarcomas within one month of their life and aging Wwox heterozygous mice have an increased incidence of spontaneous lung and mammary tumors as well as B-cell lymphomas. We herein review WWOX's role that has been unearthed thus far in different types of malignancies, its clinical significance and future implications.

Common Chromosomal Fragile Site Gene WWOX in Metabolic Disorders and Tumors

WWOX, a gene that spans the second most common chromosomal fragile site (FRA16D), often exhibits homozygous deletions and translocation breakpoints under multiple cellular stresses induced by extrinsic or intrinsic factors, such as hypoxia, UV, and DNA damage regents. Loss of WWOX is closely related to genomic instability, tumorigenesis, cancer progression and therapy resistance. WWOX heterozygous knockout mice show an increased incidence of spontaneous or induced tumors. WWOX can interact via the WW domain with proteins that possess proline PPxY motifs and is involved in a variety of cellular processes. Accumulating evidence has shown that WWOX that contains a short-chain dehydrogenase/reductase (SDR) domain is involved in steroid metabolism and bone development. Reduced or lost expression of WWOX will lead to development of metabolic disease. In this review, we focus on the roles of WWOX in metabolic disorders and tumors.

The WWOX tumor suppressor gene in endometrial adenocarcinoma

Endometrial cancer is a lethal malignancy, the causes of which remain to be determined. The aim of the present study, carried out on tumor samples from 79 patients, was to evaluate the role of the WWOX tumor suppressor gene in endometrial adenocarcinoma. The expression levels of WWOX and its protein content were assessed in normal endometrium and cancer samples. Quantitative PCR was used to assess the correlation between the expression levels of WWOX and the genes involved in the proliferation (MKI67), apoptosis (BAX, BCL2), signal transduction (EGFR), cell cycle (CCNE1, CCND1), cell adhesion (CDH1) and transcription regulation (TP73, NCOR1). The relationship between loss of hetero-zygosity (LOH) and WWOX mRNA levels was also investigated using high resolution melting. Results of the present study demonstrated a positive correlation of WWOX expression with BCL2 and CCND1 and a negative correlation with BAX, CDH1, NCOR1 and BCL2/BAX ratio. The results also showed that loss of heterozygosity at two analyzed loci of the WWOX gene is frequent in patients with endometrial cancer and that WWOX expression levels are lower in tumor samples than in normal tissue. In conclusion, WWOX may be involved in endometrial cancer.

Personalized treatment strategies in glioblastoma: MGMT promoter methylation status

The identification of molecular genetic biomarkers considerably increased our current understanding of glioma genesis, prognostic evaluation, and treatment planning. In glioblastoma, the most malignant intrinsic brain tumor entity in adults, the promoter methylation status of the gene encoding for the repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) indicates increased efficacy of current standard of care, which is concomitant and adjuvant chemoradiotherapy with the alkylating agent temozolomide. In the elderly, MGMT promoter methylation status has recently been introduced to be a predictive biomarker that can be used for stratification of treatment regimes. This review gives a short summery of epidemiological, clinical, diagnostic, and treatment aspects of patients who are currently diagnosed with glioblastoma. The most important molecular genetic markers and epigenetic alterations in glioblastoma are summarized. Special focus is given to the physiological function of DNA methylation-in particular, of the MGMT gene promoter, its clinical relevance, technical aspects of status assessment, its correlation with MGMT mRNA and protein expressions, and its place within the management cascade of glioblastoma patients.

Gene expression of WWOX, FHIT and p73 in acute lymphoblastic leukemia

The aim of the present study was to analyze the expression of WW-domain oxidoreductase (WWOX), fragile histidine triad (FHIT) and p73 in acute lymphoblastic leukemia (ALL). Samples from 122 ALL patients and 35 non-ALL control patients were collected in this study. RT-PCR was performed to detect the mRNA expression of WWOX, FHIT and p73. The methylation status of the WWOX promoter region, FHIT promoter region and the first exon region of p73 were also analyzed using the methylation-specific PCR method. The mRNA expression of WWOX, FHIT and p73 was significantly lower in the ALL samples compared with the controls (48.2, 42.9 and 55.4%, respectively). By contrast, the methylation frequency of WWOX, FHIT and p73 was significantly higher in the ALL samples compared with the controls (44.6, 46.4 and 37.5%, respectively). The mRNA expression of these three genes was inversely correlated with the methylation frequency in the ALL samples (correlation coefficients, −0.661, −0.685 and −0.536 for WWOX, FHIT and p73, respectively). Moreover, the mRNA expression of WWOX was positively correlated with that of FHIT and p73 (correlation coefficients, 0.569 and 0.556, respectively). However, the methylation status of WWOX had no correlation with that of FHIT or p73. It was concluded that the high methylation status of WWOX, FHIT and p73 may lead to the inactivation of expression and the silencing of these genes, promoting the occurrence and development of ALL. The determination of the mRNA expression and methylation status of WWOX, FHIT and p73 may aid in the development of treatment approaches for ALL.

Reduced WWOX protein expression in human astrocytoma

The WW domain-containing oxidoreductase (WWOX) functions as a tumor suppressor by interacting with various proteins in numerous important signaling pathways. WWOX silencing via homozygous deletion of its locus and/or promoter hypermethylation has been observed in various human cancers. However, the relationship between WWOX and tumors in the central nervous system has not been fully explored. In this study, the expression levels of WWOX protein in astrocytomas from 38 patients with different tumor grades were retrospectively analyzed by immunohistochemical staining. The results showed that 19 (50.0%) samples had highly reduced WWOX protein expression when compared with normal controls, while 14 (36.8%) and five (13.2%) cases exhibited moderate and mild decreases in WWOX expression, respectively. Reduction of the expression of WWOX protein correlated with patient age, supra-tentorial localization of the tumor and severity of the symptoms. Furthermore, loss of WWOX expression inversely correlated with survival time. No significant correlation was observed between the loss of WWOX expression and the gender of patients or the difference in pre-operative and post-operative karnofsky performance status scores. Surprisingly, there was no significant correlation between the loss of WWOX protein expression and overall tumor grades. Nevertheless, it was found that 63.6% (7/11) of the grade II astrocytomas had highly reduced WWOX expression and 36.4% (4/11) showed moderately reduced WWOX expression, while none of the samples exhibited mild reductions. Similar results were also found in grade III astrocytomas. The results from this small-size sample pilot study suggest that the loss of WWOX expression may be an early event in the pathogenesis of human astrocytoma.

Tumor Suppressor WWOX and p53 Alterations and Drug Resistance in Glioblastomas

Tumor suppressor p53 are frequently mutated in glioblastomas (GBMs) and appears to contribute, in part, to resistance to temozolomide (TMZ) and therapeutic drugs. WW domain-containing oxidoreductase WWOX (FOR or WOX1) is a proapoptotic protein and is considered as a tumor suppressor. Loss of WWOX gene expression is frequently seen in malignant cancer cells due to promoter hypermethylation, genetic alterations, and translational blockade. Intriguingly, ectopic expression of wild type WWOX preferentially induces apoptosis in human glioblastoma cells harboring mutant p53. WWOX is known to physically bind and stabilize wild type p53. Here, we provide an overview for the updated knowledge in p53 and WWOX, and postulate potential scenarios that wild type and mutant p53, or isoforms, modulate the apoptotic function of WWOX. We propose that triggering WWOX activation by therapeutic drugs under p53 functional deficiency is needed to overcome TMZ resistance and induce GBM cell death.

Epigenetics in human gliomas

Aberrant epigenetic landscapes and their involvement in genesis and progression of tumors, as well as in treatment responses and prognosis, indicate one of the most emerging fields in cancer research. In gliomas, the most common human primary brain tumors, and in particular in glioblastoma, the most malignant and devastating brain tumor entity in adults, the elucidation of distinct patterns of aberrant DNA methylation, histone modification, and miRNA expression and their interrelationship has fundamentally changed our point of view on these highly heterogeneous tumors. In the current review article, we address the basic principles of epigenetic control in gliomas, their current and putative future role in prognostic and predictive models and possible interactions within the epigenetic network. We discuss diagnostic and therapeutic opportunities appearing at horizon of epigenetic research. Moreover, we present current and propose future clinical workflow models for molecular characterization of malignant gliomas.

Decreased expression of WWOX in the development of esophageal squamous cell carcinoma

The WW domain-containing oxidoreductase (WWOX) gene, located on chromosome 16q23.3-24.1 in the region recognized as the common fragile site FRA16D is considered to be a tumor suppressor gene involved in various carcinomas. The present study was to investigate the alterations of WWOX expression and its correlation with polymorphism, the level of WWOX loss of heterozygosity (LOH), and methylation status in esophageal squamous cell carcinoma (ESCC). Immunohistochemistry and RT-PCR methods were used, respectively, to examine the protein and mRNA expression of WWOX in ESCC tissues. PCR-RFLP, PCR-SSLP, and MSP approach were used, respectively, to detect polymorphisms of rs3764340, rs2548861, and rs1079635 site, the level of LOH, and WWOX methylation status. Family history of upper gastrointestinal cancer (UGIC) significantly increased the risk of developing ESCC. Protein and mRNA expression of WWOX was reduced in ESCC tumor tissues and was associated with LOH and hypermethylation of the gene. The G allele of rs3764340 significantly elevated the risk of developing ESCC and was associated with TNM stage. LOH at the WWOX loci was observed in 41.4% tumors. The hypermethylation of promoter and exon1 of WWOX was found to be occurred in dysplastic tissues and the methylation frequency of WWOX in ESCC tumor tissues was significantly higher than that in corresponding normal tissues and was associated with UGIC family history. In all, these results indicate that the WWOX gene may play an important role in the development of ESCC especially in individuals with UGIC family history.

Splicing factor hnRNP A2/B1 regulates tumor suppressor gene splicing and is an oncogenic driver in glioblastoma

The process of alternative splicing is widely misregulated in cancer, but the contribution of splicing regulators to cancer development is largely unknown. In this study, we found that the splicing factor hnRNP A2/B1 is overexpressed in glioblastomas and is correlated with poor prognosis. Conversely, patients who harbor deletions of the HNRNPA2B1 gene show better prognosis than average. Knockdown of hnRNP A2/B1 in glioblastoma cells inhibited tumor formation in mice. In contrast, overexpression of hnRNP A2/B1 in immortal cells led to malignant transformation, suggesting that HNRNPA2B1 is a putative proto-oncogene. We then identified several tumor suppressors and oncogenes that are regulated by HNRNPA2B1, among them are c-FLIP, BIN1, and WWOX, and the proto-oncogene RON. Knockdown of RON inhibited hnRNP A2/B1 mediated transformation, which implied that RON is one of the mediators of HNRNPA2B1 oncogenic activity. Together, our results indicate that HNRNPA2B1 is a novel oncogene in glioblastoma and a potential new target for glioblastoma therapy.

WWOX expression in colorectal cancer--a real-time quantitative RT-PCR study

The WWOX gene is a tumour suppressor gene affected in various types of malignancies. Numerous studies showed either loss or reduction of the WWOX expression in variety of tumours, including breast, ovary, liver, stomach and pancreas. Recent study demonstrated that breast cancer patients exhibiting higher WWOX expression showed significantly longer disease-free survival in contrast to the group with lower relative WWOX level. This work was undertaken to show whether similar phenomena take place in colon tumours and cell lines. To assess the correlation of WWOX gene expression with prognosis and cancer recurrence in 99 colorectal cancer patients, we performed qRT-PCR analysis. We also performed analysis of WWOX promoter methylation status using MethylScreen method and analysis of loss of heterozygosity (LOH) status at two WWOX-related loci, previously shown to be frequently deleted in various types of tumours. A significantly better disease-free survival was observed among patients with tumours exhibiting high level of WWOX (hazard ratio = 0.39; p = 0.0452; Mantel-Cox log-rank test), but in multivariate analysis it was not an independent prognostic factor. We also found that although in colorectal cancer WWOX expression varies among patients and correlates with DFS, the exact mode of decrease in this type of tumour was not found. We failed to find the evidence of LOH in WWOX region, or hypermethylation in promoter regions of this gene. Although we provide the evidence for tumour-suppressive role of WWOX gene expression in colon, we were unable to identify the molecular mechanism responsible for this.