Common Chromosomal Fragile Site Gene WWOX in Metabolic Disorders and Tumors

DHRS2 inhibits cell growth and metastasis in ovarian cancer by downregulation of CHKα to disrupt choline metabolism

The short-chain dehydrogenase/reductase (SDR) superfamily has essential roles in lipid metabolism and redox sensing. In recent years, accumulating evidence highlights the emerging association between SDR family enzymes and cancer. Dehydrogenase/reductase member 2(DHRS2) belongs to the NADH/NADPH-dependent SDR family, and extensively participates in the regulation of the proliferation, migration, and chemoresistance of cancer cells. However, the underlying mechanism has not been well defined. In the present study, we have demonstrated that DHRS2 inhibits the growth and metastasis of ovarian cancer (OC) cells in vitro and in vivo. Mechanistically, the combination of transcriptome and metabolome reveals an interruption of choline metabolism by DHRS2. DHRS2 post-transcriptionally downregulates choline kinase α (CHKα) to inhibit AKT signaling activation and reduce phosphorylcholine (PC)/glycerophosphorylcholine (GPC) ratio, impeding choline metabolism reprogramming in OC. These actions mainly account for the tumor-suppressive role of DHRS2 in OC. Overall, our findings establish the mechanistic connection among metabolic enzymes, metabolites, and the malignant phenotype of cancer cells. This could result in further development of novel pharmacological tools against OC by the induction of DHRS2 to disrupt the choline metabolic pathway.

WWOX Phosphorylation, Signaling, and Role in Neurodegeneration

Homozygous null mutation of tumor suppressor WWOX/Wwox gene leads to severe neural diseases, metabolic disorders and early death in the newborns of humans, mice and rats. WWOX is frequently downregulated in the hippocampi of patients with Alzheimer’s disease (AD). In vitro analysis revealed that knockdown of WWOX protein in neuroblastoma cells results in aggregation of TRAPPC6AΔ, TIAF1, amyloid β, and Tau in a sequential manner. Indeed, TRAPPC6AΔ and TIAF1, but not tau and amyloid β, aggregates are present in the brains of healthy mid-aged individuals. It is reasonable to assume that very slow activation of a protein aggregation cascade starts sequentially with TRAPPC6AΔ and TIAF1 aggregation at mid-ages, then caspase activation and APP de-phosphorylation and degradation, and final accumulation of amyloid β and Tau aggregates in the brains at greater than 70 years old. WWOX binds Tau-hyperphosphorylating enzymes (e.g., GSK-3β) and blocks their functions, thereby supporting neuronal survival and differentiation. As a neuronal protective hormone, 17β-estradiol (E2) binds WWOX at an NSYK motif in the C-terminal SDR (short-chain alcohol dehydrogenase/reductase) domain. In this review, we discuss how WWOX and E2 block protein aggregation during neurodegeneration, and how a 31-amino-acid zinc finger-like Zfra peptide restores memory loss in mice.

Genetic association study identifies a functional CNV in the WWOX gene contributes to the risk of intracranial aneurysms

Intracranial aneurysms (IAs) accounts for 85% of hemorrhagic stroke. Genetic factors have been known to play an important role in the development of IAs. A functional CNV (CNV-67048) of human WW domain-containing oxidoreductase (WWOX), which has been identified as a tumor suppressor gene in multiple cancers, was identified to be associated with gliomas risk previously. Here, we hypothesized that the CNV-67048 could also affect susceptibility of IAs. Based on a two-stage, case⁻ control study with a total of 976 patients of IAs and 1,200 matched healthy controls, we found the effect size for per copy deletion was 1.35 (95% CI = 1.16–1.57; P_trend = 1.18 × 10⁻⁴). Compared with the individuals having no deletion, significantly higher risk of IAs was detected for both subjects carrying 1 copy deletion (OR = 1.24, 95% CI = 1.02–1.52) and subjects carrying 2 copy deletion (OR = 1.77, 95% CI = 1.24–2.53). Real-time PCR was used to confirm the abnormal expression of WWOX in tissues of IA patients and influence of genotypes of CNV-67048. The expression level of WWOX in IA tissues was significantly lower than that in corresponding normal tissues (P = 0.004), and the deletion genotypes of CNV-67048 have lower WWOX mRNA levels in both tumor tissues and border tissues (P < 0.01). Our data suggests that the deletion genotypes of CNV-67048 in WWOX predispose their carriers to IAs, which might be a genetic biomarker to predict risk of IAs in Chinese.

DHRS2 inhibits cell growth and motility in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is highly prevailing in Asia and it is ranked in the most aggressive squamous cell carcinomas. High-frequency loss of heterozygosity occurred in chromosome 14q11.2 in many tumors including ESCC, suggesting that one or more tumor-suppressor genes might exist within this region. In this study, we identified the tumor-suppressing role of DHRS2 (short-chain dehydrogenase/reductase family, member 2) at 14q11.2 in ESCCs. Downregulation of DHRS2 occurred in 30.8% of primary ESCC tumor tissues vs paired non-tumorous tissues. DHRS2 downregulation was associated significantly with ESCC invasion, lymph nodes metastasis and clinical staging (P<0.001). Survival analysis revealed that DHRS2 downregulation was significantly associated with worse outcome of patients with ESCC. In vitro and in vivo studies indicated that both DHRS2 variants could suppress cell proliferation and cell motility. Moreover, we demonstrated that DHRS2 could reduce reactive oxygen species and decrease nicotinamide adenine dinucleotide phosphate (oxidized/reduced), increase p53 stability and decrease Rb phosphorylation; it also decreased p38 mitogen-activated protein kinase phosphorylation and matrix metalloproteinase 2. In summary, these findings demonstrated that DHRS2 had an important part in ESCC development and progression.

Exogenous WWOX enhances apoptosis and weakens metastasis in CNE2 nasopharyngeal carcinoma cells through the intrinsic apoptotic pathway

The WW domain containing oxidoreductase (WWOX) has been postulated to behave as a putative tumor suppressor and that silencing of WWOX expression is linked to the carcinogenesis and progression of various carcinomas. The role of WWOX in nasopharyngeal carcinoma (NPC) remains unclear. Herein, we sought to evaluate the biological feature of WWOX restoration in human CNE2 NPC cells. In vitro experiments manifested that transiently overexpressed WWOX significantly suppressed proliferation as well as invasion and migration of the CNE2 cells. Of note, WWOX-induced apoptosis could be partly reversed by the selective caspase inhibitor, Z-VAD-FMK. Furthermore, immunoblotting analysis indicated that ectopic expression of WWOX could trigger the intrinsic apoptotic signaling pathway characterized by a down-regulation of Bcl-2 and Bcl-xL, and up-regulation of Bax and Cytochrome c along with a remarkable activation of the caspase cascades. Taken together, our data reveal that WWOX behaves as a potent tumor suppressor in CNE2 cells, possibly by enhancing apoptosis and weakening metastasis via the intrinsic apoptotic pathway.

Expression of ORAOV1, CD133 and WWOX correlate with metastasis and prognosis in gastric adenocarcinoma

BACKGROUND

Oral cancer overexpressed 1 (ORAOV1) which is a novel candidate oncogene is a useful biomarker of metastasis and prognosis in various cancers. CD133 which is a biomarker of cancer stem cells is overexpressed in many cancers and promotes cancer cells growth and metastasis. WW domain-containing oxidoreductase (WWOX) which is a suppressor gene of tumor can inhibit proliferation and promote apoptosis in various cancers. However, associations among ORAOV1, CD133, and WWOX and their clinicopathological significance in gastric adenocarcionma (GAC) are unclear. In this study, we analyzed associations among ORAOV1, CD133, and WWOX in GAC, and their respective associations with clinicopathological characteristics and survival in GAC.

METHOD

Positive expression of ORAOV1, CD133, and WWOX in 236 whole GAC tissue samples were detected by immunohistochemistry staining. Patients' clinical data were also collected.

RESULTS

Levels of ORAOV1 and CD133 were significantly higher, and levels of WWOX significantly lower, in GAC tissues than in normal gastric tissues. Levels of ORAOV1 and CD133 were positively associated with tumor grade, invasion of depth, lymph node metastasis (LNM), and tumor-node metastasis (TNM) stages, and inversely with patients overall survival time; levels of WWOX was negatively correlated with tumor grade, invasion of depth, LNM, and TNM stages, and the WWOX-positive subgroup had significantly longer overall survival time than did the WWOX-negative subgroup. In multivariate analysis, high expression of ORAOV1 and CD133, invasion of depth, and TNM stages, and low expression of WWOX were potential to be independent prognostic factors for overall survival time in patients with GAC.

CONCLUSIONS

The expression of ORAOV1, CD133, and WWOX represent promising biomarkers for metastasis and prognosis, and potential therapeutic targets for GAC.

A new tumor suppressor lncRNA RP11-190D6.2 inhibits the proliferation, migration, and invasion of epithelial ovarian cancer cells

At present, a large number of long noncoding RNAs (lncRNAs) from the human genome have been discovered. Meanwhile, emerging evidence has indicated that lncRNAs could play a critical role in the regulation of cellular processes such as cancer progression and metastasis. However, the functions of some new lncRNAs in the complex transcriptional process are mostly unknown at present. Existing studies suggest that loss of WW domain-containing oxidoreductase (WWOX) expression is linked with poor prognosis in numerous cancers, including epithelial ovarian cancer (EOC). However, the functional role of its antisense transcript RP11-190D6.2 is not clear to date. In this study, WWOX antisense transcript RP11-190D6.2 was analyzed specifically in EOC cells using real-time polymerase chain reaction and gain-/loss-of-function studies. We found that RP11-190D6.2 expression was positively correlated with WWOX expression. The RP11-190D6.2 expression was markedly downregulated in tumor tissues compared with normal tissues, but the RP11-190D6.2 expression was significantly downregu-lated in four EOC cell lines compared with human ovarian surface epithelial cell line. RP11-190D6.2 overexpression resulted in the increase of WWOX expression, whereas its knockdown led to the decrease of WWOX expression. We also found that RP11-190D6.2 was restored by 5-aza-2′-deoxycytidine treatment in EOC. In addition, the RP11-190D6.2 overexpression and knockdown experiments revealed that RP11-190D6.2 overexpression inhibited proliferation, migration, and invasion abilities in HO8910-PM cells, whereas RP11-190D6.2 knockdown in HEY-A8 cells had the opposite effect. The analyses in EOC implicate that RP11-190D6.2 may play a pivotal role in the regulation of tumor metastasis, suggesting that RP11-190D6.2 may serve as a potential biomarker and therapeutic target for EOC.

Fragility Extraordinaire: Unsolved Mysteries of Chromosome Fragile Sites

Chromosome fragile sites are a fascinating cytogenetic phenomenon now widely implicated in a slew of human diseases ranging from neurological disorders to cancer. Yet, the paths leading to these revelations were far from direct, and the number of fragile sites that have been molecularly cloned with known disease-associated genes remains modest. Moreover, as more fragile sites were being discovered, research interests in some of the earliest discovered fragile sites ebbed away, leaving a number of unsolved mysteries in chromosome biology. In this review we attempt to recount some of the early discoveries of fragile sites and highlight those phenomena that have eluded intense scrutiny but remain extremely relevant in our understanding of the mechanisms of chromosome fragility. We then survey the literature for disease association for a comprehensive list of fragile sites. We also review recent studies addressing the underlying cause of chromosome fragility while highlighting some ongoing debates. We report an observed enrichment for R-loop forming sequences in fragile site-associated genes than genomic average. Finally, we will leave the reader with some lingering questions to provoke discussion and inspire further scientific inquiries.

Chromothripsis-like chromosomal rearrangements induced by ionizing radiation using proton microbeam irradiation system

Chromothripsis is the massive but highly localized chromosomal rearrangement in response to a one-step catastrophic event, rather than an accumulation of a series of subsequent and random alterations. Chromothripsis occurs commonly in various human cancers and is thought to be associated with increased malignancy and carcinogenesis. However, the causes and consequences of chromothripsis remain unclear. Therefore, to identify the mechanism underlying the generation of chromothripsis, we investigated whether chromothripsis could be artificially induced by ionizing radiation. We first elicited DNA double-strand breaks in an oral squamous cell carcinoma cell line HOC313-P and its highly metastatic subline HOC313-LM, using Single Particle Irradiation system to Cell (SPICE), a focused vertical microbeam system designed to irradiate a spot within the nuclei of adhesive cells, and then established irradiated monoclonal sublines from them, respectively. SNP array analysis detected a number of chromosomal copy number alterations (CNAs) in these sublines, and one HOC313-LM-derived monoclonal subline irradiated with 200 protons by the microbeam displayed multiple CNAs involved locally in chromosome 7. Multi-color FISH showed a complex translocation of chromosome 7 involving chromosomes 11 and 12. Furthermore, whole genome sequencing analysis revealed multiple de novo complex chromosomal rearrangements localized in chromosomes 2, 5, 7, and 20, resembling chromothripsis. These findings suggested that localized ionizing irradiation within the nucleus may induce chromothripsis-like complex chromosomal alterations via local DNA damage in the nucleus.

MicroRNA-153 promotes Wnt/β-catenin activation in hepatocellular carcinoma through suppression of WWOX

Persistent activation of Wnt/β-catenin signaling plays crucial roles in the development of human cancers, including hepatocellular carcinoma (HCC). Here, we performed a MicroRNA-based genetic screen, which revealed a novel diversion in β-catenin signaling triggered by MicroRNA-153 (miR-153). Overexpression of miR-153 was able to promote β-catenin transcriptional activity, leading to cell-cycle progression, proliferation and colony formation of HCC cells. Additionally, systemic administration of miR-153 antigomir suppressed hepatocellular carcinogenesis in a murine liver cancer model. At the molecular level, we found that miR-153 inhibited protein level of WWOX, a tumor suppressor and inhibitor of β-catenin signaling, through targeting its 3′-untranslated region. Therefore, our study highlights the importance of MicroRNA-153/WWOX/β-catenin regulatory axis in the HCC tumorigenesis.

WW domain-containing oxidoreductase in neuronal injury and neurological diseases

The human and mouse WWOX/Wwox gene encodes a candidate tumor suppressor WW domain-containing oxidoreductase protein. This gene is located on a common fragile site FRA16D. WWOX participates in a variety of cellular events and acts as a transducer in the many signal pathways, including TNF, chemotherapeutic drugs, UV irradiation, Wnt, TGF-β, C1q, Hyal-2, sex steroid hormones, and others. While transiently overexpressed WWOX restricts relocation of transcription factors to the nucleus for suppressing cancer survival, physiological relevance of this regard in vivo has not been confirmed. Unlike many tumor suppressor genes, mutation of WWOX is rare, raising a question whether WWOX is a driver for cancer initiation. WWOX/Wwox was initially shown to play a crucial role in neural development and in the pathogenesis of Alzheimer's disease and neuronal injury. Later on, WWOX/Wwox was shown to participate in the development of epilepsy, mental retardation, and brain developmental defects in mice, rats and humans. Up to date, most of the research and review articles have focused on the involvement of WWOX in cancer. Here, we review the role of WWOX in neural injury and neurological diseases, and provide perspectives for the WWOX-regulated neurodegeneration.

Ectopic expression of the WWOX gene suppresses stemness of human ovarian cancer stem cells

The present study aimed to investigate the effects of the WW domain-containing oxidoreductase (WWOX) gene on the stem cell properties of human ovarian cancer stem cells. A eukaryotic expression vector containing the WWOX gene was transfected into human ovarian cancer stem cells and Western blotting was used to assess the expression of WWOX protein in the transfected cells compared with the control cells (untransfected cells and cells transfected with the empty vector). The self-renewal abilities of these three types of stem cells was also assessed in vitro. To monitor changes in their differentiation potential, cells were cultured in medium supplemented with serum, and the expression of specific stem cell markers was determined. Drug-sensitivity tests were used to measure the sensitivity of the stem cells to cisplatin, doxorubicin, and mitoxantrone. The cells were also transplanted into non-obese diabetic (NOD)/severe combined immunodeficiency (SCID) mice to determine the changes in their tumorigenicity in vivo. Cells transfected with the WWOX-expressing plasmid stably expressed WWOX protein, while no WWOX protein was detected in control cells. Compared with the two types of control cells, WWOX-expressing stem cells manifested significantly reduced self-renewal ability. Compared with control cells, the expression levels of stem cell markers, including CD133, CD117, ATP-binding cassette sub-family G member 2, Nanog, octamer-binding transcription factor 4 and breast cancer resistance protein, were significantly lower in WWOX-expressing cells, while the level of the differentiation marker E-cadherin was significantly higher in WWOX-expressing cells. Furthermore, WWOX-expressing cells were more sensitive to treatment with cisplatin, doxorubicin and mitoxantrone. In NOD/SCID mice, the tumorigenicity of WWOX-expressing cells was significantly lower compared with that of control cells. The results indicate that the tumor suppressor WWOX suppresses stem cell properties in cancer stem cells, including self-renewal ability, differentiation potential, in vivo tumorigenic capability, high-level expression of stem cell genes and multidrug resistance.

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.

Loss of wwox expression in zebrafish embryos causes edema and alters Ca(2+) dynamics

We investigated the role of the WW domain-containing oxidoreductase (wwox) gene in the embryonic development of zebrafish, with particular emphasis on intracellular Ca²⁺ dynamics because Ca²⁺ is an important intracellular messenger. Comparisons between zebrafish wwox and human WWOX sequences identified highly conserved domain structures. wwox was expressed in developing heart tissues in the zebrafish embryo. Moreover, wwox knockdown induced pericardial edema with similarities to conditions observed in human breast cancer. The wwox knockdown embryos with the edema died within a week. High Ca²⁺ levels were observed at the boundary between the edema and yolk in wwox knockdown embryos.

Strategies of oncogenic microbes to deal with WW domain-containing oxidoreductase

WW domain-containing oxidoreductase (WWOX) is a well-documented tumor suppressor protein that controls growth, survival, and metastasis of malignant cells. To counteract WWOX's suppressive effects, cancer cells have developed many strategies either to downregulate WWOX expression or to functionally inactivate WWOX. Relatively unknown is, in the context of those cancers associated with certain viruses or bacteria, how the oncogenic pathogens deal with WWOX. Here we review recent studies showing different strategies utilized by three cancer-associated pathogens. Helicobactor pylori reduces WWOX expression through promoter hypermethylation, an epigenetic mechanism also occurring in many other cancer cells. WWOX has a potential to block canonical NF-κB activation and tumorigenesis induced by Tax, an oncoprotein of human T-cell leukemia virus. Tax successfully overcomes the blockage by inhibiting WWOX expression through activation of the non-canonical NF-κB pathway. On the other hand, latent membrane protein 2A of Epstein-Barr virus physically interacts with WWOX and redirects its function to trigger a signaling pathway that upregulates matrix metalloproteinase 9 and cancer cell invasion. These reports may be just "the tip of the iceberg" regarding multiple interactions between WWOX and oncogenic microbes. Further studies in this direction should expand our understanding of infection-driven oncogenesis.

The fragile site WWOX gene and the developing brain

WWOX was cloned as a tumor suppressor gene mapping to chromosomal fragile site FRA16D. Loss of WWOX is closely related to tumorigenesis, cancer progression, and therapy resistance. Recent studies demonstrate the growing role of WWOX gene in other human pathologies such as metabolic and nervous system-related conditions. The neurologic phenotype of WWOX mutation includes seizures, ataxia, developmental delay, and spasticity of variable severity. WWOX is a ubiquitous protein with high expression in many tissues including brain, cerebellum, brain stem, and spinal cord. WWOX is highly expressed in different brain regions during murine fetal development and remained unchanged in the cortex and the corpus callosum in adult mice. The mechanism or the putative role of WWOX in the nervous system is still unclear but may include abnormal signaling protein, disruption of neuronal pathways, neuronal differentiation, mitochondrial dysfunction, or apoptosis. Homozygous mutations affecting WWOX in humans are likely to be more described in the future using exome sequencing. The described findings highlight that WWOX plays a critical role in normal central nervous system development and disease. The aim of this review is to summarize the roles of WWOX in the developing brain.

A novel whole exon deletion in WWOX gene causes early epilepsy, intellectual disability and optic atrophy

Recent studies have implicated the WW domain-containing oxidoreductase encoding gene (WWOX) in a severe form of autosomal recessive neurological disorder. This condition showed an overlapping spectrum of clinical features including spinocerebellar ataxia associated with generalized seizures and delayed psychomotor development to growth retardation, spasticity, and microcephaly. We evaluated a child from a consanguineous Emirati family that presented at birth with growth retardation, microcephaly, epileptic seizures, and later developed spasticity and delayed psychomotor development. Screening for deletions and duplications using whole-chromosomal microarray analysis identified a novel homozygous microdeletion encompassing exon 5 of the WWOX gene. Analysis of parental DNA indicated that this deletion was inherited from both parents and lies within a large region of homozygosity. Sanger sequencing of the cDNA showed that the deletion resulted in exon 5 skipping leading to a frame-shift and creating a premature stop codon at amino acid position 212. Quantification of mRNA revealed striking low level of WWOX expression in the child and moderate level of expression in the mother compared to a healthy control. To the best of our knowledge, this is the first homozygous germline structural variation in WWOX gene resulting in truncated transcripts that were presumably subject to NMD pathway. Our findings extend the clinical and genetic spectrum of WWOX mutations and support a crucial role of this gene in neurological development.