The fragile genesFHIT andWWOX are inactivated coordinately in invasive breast carcinoma

Unveiling the relationship between WWOX and BRCA1 in mammary tumorigenicity and in DNA repair pathway selection

Breast cancer is the leading cause of cancer-related deaths in women worldwide, with the basal-like or triple-negative breast cancer (TNBC) subtype being particularly aggressive and challenging to treat. Understanding the molecular mechanisms driving the development and progression of TNBC is essential. We previously showed that WW domain-containing oxidoreductase (WWOX) is commonly inactivated in TNBC and is implicated in the DNA damage response (DDR) through ATM and ATR activation. In this study, we investigated the interplay between WWOX and BRCA1, both frequently inactivated in TNBC, on mammary tumor development and on DNA double-strand break (DSB) repair choice. We generated and characterized a transgenic mouse model (K14-Cre;Brca1fl/fl;Wwoxfl/fl) and observed that mice lacking both WWOX and BRCA1 developed basal-like mammary tumors and exhibited a decrease in 53BP1 foci and an increase in RAD51 foci, suggesting impaired DSB repair. We examined human TNBC cell lines harboring wild-type and mutant BRCA1 and found that WWOX expression promoted NHEJ repair in cells with wild-type BRCA1. Our findings suggest that WWOX and BRCA1 play an important role in DSB repair pathway choice in mammary epithelial cells, underscoring their functional interaction and significance in breast carcinogenesis.

Antineoplastic Nature of WWOX in Glioblastoma Is Mainly a Consequence of Reduced Cell Viability and Invasion

Following the discovery of WWOX, research has moved in many directions, including the role of this putative tumor suppressor in the central nervous system and related diseases. The task of determining the nature of WWOX in glioblastoma (GBM) is still considered to be at the initial stage; however, the influence of this gene on the GBM malignant phenotype has already been reported. Because most of the available in vitro research does not consider several cellular GBM models or a wide range of investigated biological assays, the present study aimed to determine the main processes by which WWOX exhibits anticancer properties in GBM, while taking into account the phenotypic heterogeneity between cell lines. Ectopic WWOX overexpression was studied in T98G, DBTRG-05MG, U251MG, and U87MG cell lines that were compared with the use of assays investigating cell viability, proliferation, apoptosis, adhesion, clonogenicity, three-dimensional and anchorage-independent growth, and invasiveness. Observations presenting the antineoplastic properties of WWOX were consistent for T98G, U251MG, and U87MG. Increased proliferation and tumor growth were noted in WWOX-overexpressing DBTRG-05MG cells. A possible explanation for this, arrived at via bioinformatics tools, was linked to the TARDBP transcription factor and expression differences of USP25 and CPNE2 that regulate EGFR surface abundance. Collectively, and despite various cell line-specific circumstances, WWOX exhibits its anticancer nature mainly via a reduction of cell viability and invasiveness of glioblastoma.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

Interaction of Wwox with Brca1 and associated complex proteins prevents premature resection at double-strand breaks and aberrant homologous recombination

Down regulation of Wwox protein expression occurs in many cancers, contributing to insensitivity to ionizing radiation (IR) and platinum drug treatments. Patients with reduced Wwox expression in their cancer tissue show decreased overall survival following these treatments, in accord with our earlier finding that reduced Wwox protein expression in cancers is associated with changes in choice of DNA double-strand break (DSB) repair pathway. Our current investigation of mechanisms underlying the initial choice of repair by homologous recombination/single-strand annealing (HR/SSA) in Wwox-deficient cells, showed immediate DNA end-resection at DSBs following IR, abrogating initial repair by the expected non-homologous end-joining (NHEJ) pathway. Mechanisms supporting the expected choice of DSB repair by NHEJ in Wwox-sufficient cells are: 1) direct recruitment of Wwox protein binding to Brca1 through the Brca1 ⁹⁸¹PPLF⁹⁸⁴ Wwox-binding motif; 2) possible Wwox blocking of Brca1-Rad50 interaction and of Brca1 activation by Chk2 phosphorylation of Brca1 S988; 3) Wwox suppression of Brca1 interaction with the B and C complex proteins, Brip1 and CtIP, thereby delaying the process of DSB end-resection post-IR. Wwox deficiency, instead, leads to early formation of the Brca1-CtIP/MRN complex at induced DSBs, stimulating immediate post-IR end-resection. This premature resection at DNA DSBs leads to inappropriate HR/SSA repair not restricted to late S/G2 cell cycle phases, and increases mutations in genomes of radiation or platinum-resistant colonies. Prevention of premature initiation of end-resection, by combining Chk2 inhibition with IR or carboplatin treatment, successfully sensitized IR and platinum-resistant Wwox-deficient cells by synthetic lethality, but did not alter response of Wwox-sufficient cells. Our results establish Wwox as a biomarker for treatment response and provide potential targets, such as Chk2, for reversal of treatment resistance.

Molecular Functions of WWOX Potentially Involved in Cancer Development

The WW domain-containing oxidoreductase gene (WWOX) was cloned 21 years ago as a putative tumor suppressor gene mapping to chromosomal fragile site FRA16D. The localization of WWOX in a chromosomal region frequently altered in human cancers has initiated multiple current studies to establish its role in this disease. All of this work suggests that WWOX, due to its ability to interact with a large number of partners, exerts its tumor suppressive activity through a wide variety of molecular actions that are mostly cell specific.

Cigarette Smoke and Nicotine-Containing Electronic-Cigarette Vapor Downregulate Lung WWOX Expression, Which Is Associated with Increased Severity of Murine Acute Respiratory Distress Syndrome

A history of chronic cigarette smoking is known to increase risk for acute respiratory distress syndrome (ARDS), but the corresponding risks associated with chronic e-cigarette use are largely unknown. The chromosomal fragile site gene, WWOX, is highly susceptible to genotoxic stress from environmental exposures and thus an interesting candidate gene for the study of exposure-related lung disease. Lungs harvested from current versus former/never-smokers exhibited a 47% decrease in WWOX mRNA levels. Exposure to nicotine-containing e-cigarette vapor resulted in an average 57% decrease in WWOX mRNA levels relative to vehicle-treated controls. In separate studies, endothelial (EC)-specific WWOX knockout (KO) versus WWOX flox control mice were examined under ARDS-producing conditions. EC WWOX KO mice exhibited significantly greater levels of vascular leak and histologic lung injury. ECs were isolated from digested lungs of untreated EC WWOX KO mice using sorting by flow cytometry for CD31+ CD45-cells. These were grown in culture, confirmed to be WWOX deficient by RT-PCR and Western blotting, and analyzed by electric cell impedance sensing as well as an FITC dextran transwell assay for their barrier properties during methicillin-resistant Staphylococcus aureus or LPS exposure. WWOX KO ECs demonstrated significantly greater declines in barrier function relative to cells from WWOX flox controls during either methicillin-resistant S. aureus or LPS treatment as measured by both electric cell impedance sensing and the transwell assay. The increased risk for ARDS observed in chronic smokers may be mechanistically linked, at least in part, to lung WWOX downregulation, and this phenomenon may also manifest in the near future in chronic users of e-cigarettes.

Characterization of WWOX expression and function in canine mast cell tumors and malignant mast cell lines

BACKGROUND

The WW domain-containing oxidoreductase (WWOX) tumor suppressor gene is frequently lost in a variety of solid and hematopoietic malignancies in humans. Dysregulation of WWOX has been implicated as playing a key role in tumor cell survival, DNA damage repair, and genomic stability. The purpose of this study was to characterize WWOX expression in spontaneous canine mast cell tumors (MCTs) and malignant cell lines and investigate the potential contribution of WWOX loss on malignant mast cell behavior.

METHODS/RESULTS

WWOX expression is decreased in primary canine MCTs and malignant mast cell lines compared to normal canine bone marrow-cultured mast cells. In transformed canine mastocytoma cell lines, overexpression of WWOX or WWOX knockdown had no effect on mast cell viability. Inhibition of WWOX enhanced clonogenic survival following treatment with ionizing radiation in the C2 mast cell line. Lastly, immunohistochemistry for WWOX was performed using a canine MCT tissue microarray, demonstrating that WWOX staining intensity and percent of cells staining for WWOX is decreased in high-grade MCTs compared to low-grade MCTs.

CONCLUSIONS

These data suggest that WWOX expression is attenuated or lost in primary canine MCTs and malignant mast cell lines. Given the observed increase in clonogenic survival in WWOX-deficient C2 mast cells treated with ionizing radiation, further investigation of WWOX and its role in mediating the DNA damage response in malignant mast cells is warranted.

Pleiotropic tumor suppressor functions of WWOX antagonize metastasis

Tumor progression and metastasis are the major causes of death among cancer associated mortality. Metastatic cells acquire features of migration and invasion and usually undergo epithelia-mesenchymal transition (EMT). Acquirement of these various hallmarks rely on different cellular pathways, including TGF-β and Wnt signaling. Recently, we reported that WW domain-containing oxidoreductase (WWOX) acts as a tumor suppressor and has anti-metastatic activities involving regulation of several key microRNAs (miRNAs) in triple-negative breast cancer (TNBC). Here, we report that WWOX restoration in highly metastatic MDA-MB435S cancer cells alters mRNA expression profiles; further, WWOX interacts with various proteins to exert its tumor suppressor function. Careful alignment and analysis of gene and miRNA expression in these cells revealed profound changes in cellular pathways mediating adhesion, invasion and motility. We further demonstrate that WWOX, through regulation of miR-146a levels, regulates SMAD3, which is a member of the TGF-β signaling pathway. Moreover, proteomic analysis of WWOX partners revealed regulation of the Wnt-signaling activation through physical interaction with Disheveled. Altogether, these findings underscore a significant role for WWOX in antagonizing metastasis, further highlighting its role and therapeutic potential in suppressing tumor progression.

Loss of Wwox Causes Defective Development of Cerebral Cortex with Hypomyelination in a Rat Model of Lethal Dwarfism with Epilepsy

WW domain-containing oxidoreductase (Wwox) is a putative tumor suppressor. Several germline mutations of Wwox have been associated with infant neurological disorders characterized by epilepsy, growth retardation, and early death. Less is known, however, about the pathological link between Wwox mutations and these disorders or the physiological role of Wwox in brain development. In this study, we examined age-related expression and histological localization of Wwox in forebrains as well as the effects of loss of function mutations in the Wwox gene in the immature cortex of a rat model of lethal dwarfism with epilepsy (lde/lde). Immunostaining revealed that Wwox is expressed in neurons, astrocytes, and oligodendrocytes. lde/lde cortices were characterized by a reduction in neurite growth without a reduced number of neurons, severe reduction in myelination with a reduced number of mature oligodendrocytes, and a reduction in cell populations of astrocytes and microglia. These results indicate that Wwox is essential for normal development of neurons and glial cells in the cerebral cortex.

Downregulation of WW domain-containing oxidoreductase leads to tamoxifen-resistance by the inactivation of Hippo signaling

Acquired tamoxifen-resistance is an important cause of death in patients with hormone-dependent breast tumors. Therefore, understanding the molecular mechanisms underlying the development of tamoxifen-resistance is critical for successful endocrine therapy. This study aimed to define the role of WW domain-containing oxidoreductase (WWOX) in acquired tamoxifen-resistance. Our results show that low WWOX expression was significantly related to tamoxifen-resistance. Moreover, WWOX-knockdown increased resistance to tamoxifen, while WWOX overexpression decreased the resistance. Furthermore, WWOX silencing decreased Yes-associated protein (YAP) phosphorylation and increased YAP nuclear translocation. Finally, YAP silencing decreased tamoxifen-resistance in WWOX-knockdown cells. Our findings demonstrate that WWOX downregulation can lead to the development of tamoxifen-resistance by inactivating Hippo signaling. Thus, WWOX might be a valuable target and prognostic marker for tamoxifen-resistance.

Impact statement

Understanding the molecular pathways leading to the development of tamoxifen-resistance is an important research focus as acquired tamoxifen-resistance is the main cause of death in patients with benign primary prognosis. Although WW domain-containing oxidoreductase (WWOX) has been related to breast tumorigenesis, its role in acquired tamoxifen-resistance has not yet been demonstrated. Our findings show that WWOX might be a valuable therapeutic target and prognostic marker for tamoxifen-resistance.

Fhit-Fdxr interaction in the mitochondria: modulation of reactive oxygen species generation and apoptosis in cancer cells

Fhit protein is lost in cancers of most, perhaps all, cancer types; when restored, it can induce apoptosis and suppress tumorigenicity, as shown in vitro and in mouse tumor models in vivo. Following protein cross-linking and proteomics analyses, we characterized a Fhit protein complex involved in triggering Fhit-mediated apoptosis. The complex includes the heat-shock chaperonin pair, HSP60/10, which is likely involved in importing Fhit into the mitochondria, where it interacts with ferredoxin reductase, responsible for transferring electrons from NADPH to cytochrome P450 via ferredoxin, in electron transport chain complex III. Overexpression of Fhit protein in Fhit-deficient cancer cells modulates the production of intracellular reactive oxygen species, causing increased ROS, following peroxide treatment, with subsequent increased apoptosis of lung cancer cells under oxidative stress conditions; conversely, Fhit-negative cells escape ROS overproduction and ROS-induced apoptosis, likely carrying oxidative damage. Thus, characterization of Fhit-interacting proteins has identified direct effectors of a Fhit-mediated apoptotic signal pathway that is lost in many cancers. This is of translational interest considering the very recent emphasis in a number of high-profile publications, concerning the role of oxidative phosphorylation in the treatment of human cancers, and especially cancer stem cells that rely upon oxidative phosphorylation for survival. Additionally, we have shown that cells from a Fhit-deficient lung cancer cell line, are sensitive to killing by exposure to atovaquone, thought to act as a selective oxidative phosphorylation inhibitor by targeting the CoQ10 dependence of the mitochondrial complex III, while the Fhit-expressing sister clone is resistant to this treatment.

WWOX Inhibits Metastasis of Triple-Negative Breast Cancer Cells via Modulation of miRNAs

Triple-negative breast cancer (TNBC) is a heterogeneous, highly aggressive, and difficult to treat tumor type. The tumor suppressor WWOX spans FRA16D, a common fragile site that is commonly altered in breast cancer. Despite recent progress, the role of WWOX in TNBC metastasis is unknown. Here we report that WWOX inactivation correlates with advanced stages of TNBC and that its levels are frequently altered in TNBC cells. Ectopic restoration of WWOX in WWOX-negative TNBC cells inhibited metastasis while its depletion in WWOX-positive TNBC cells promoted metastasis. WWOX was a negative regulator of c-MYC, which regulated miR-146a expression and consequently fibronectin levels, contributing to an epithelial status of the cell. Treatment of TNBC cells with anti-miR-146a rescued the WWOX antimetastatic phenotype. Moreover, overexpression of MYC in WWOX-expressing TNBC cells overrode WWOX effects on miR-146a and fibronectin levels. Altogether, our data uncover an essential role for WWOX in antagonizing TNBC progression and highlight its potential use as a biomarker for metastasis. SIGNIFICANCE: These findings highlight the mechanism by which the tumor suppressor WWOX regulates metastasis of triple-negative breast cancer.See related commentary by Sharma, p. 1746.

Modeling WWOX Loss of Function in vivo: What Have We Learned?

The WW domain–containing oxidoreductase (WWOX) gene encompasses a common fragile sites (CFS) known as FRA16D, and is implicated in cancer. WWOX encodes a 46kDa adaptor protein, which contains two N-terminal WW–domains and a catalytic domain at its C–terminus homologous to short–chain dehydrogenase/reductase (SDR) family proteins. A high sequence conservation of WWOX orthologues from insects to rodents and ultimately humans suggest its significant role in physiology and homeostasis. Indeed, data obtained from several animal models including flies, fish, and rodents demonstrate WWOX in vivo requirement and that its deregulation results in severe pathological consequences including growth retardation, post–natal lethality, neuropathy, metabolic disorders, and tumorigenesis. Altogether, these findings set WWOX as an essential protein that is necessary to maintain normal cellular/physiological homeostasis. Here, we review and discuss lessons and outcomes learned from modeling loss of WWOX expression in vivo.

Loss of Wwox drives metastasis in triple-negative breast cancer by JAK2/STAT3 axis

Loss of WW domain-containing oxidoreductase (Wwox) expression has been observed in breast cancer (BC). However, its regulatory effects are largely unknown, especially in triple-negative breast cancer (TNBC). Herein, gene expression profiling revealed that JAK/STAT3 pathway was one of the most differentially modulated pathways in basal-like BC cells. The lower expression of Wwox was significantly correlated with high activation of STAT3 in basal-like cells and TNBC tissues. Overexpression of Wwox markedly inhibited proliferation and metastasis of BC cells by suppressing STAT3 activation, which is to interact with JAK2 to inhibit JAK2 and STAT3 phosphorylation. Furthermore, Wwox limited STAT3 binding to the interleukin-6 promoter, repressing expression of the IL-6 cytokine. Altogether, our data established that Wwox suppresses BC cell metastasis and proliferation by JAK2/STAT3 pathway. Targeting of Wwox with STAT3 could offer a promising therapeutic strategy for TNBC.

In breast cancer, the loss of expression of WW domain-containing oxireductase (Wwox) has been observed. Here, the authors illustrate that in triple negative breast cancer models Wwox suppresses metastasis and proliferation via the JAK2/STAT3 pathway.

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.

Somatic loss of WWOX is associated with TP53 perturbation in basal-like breast cancer

Inactivation of WW domain-containing oxidoreductase (WWOX), the gene product of the common fragile site FRA16D, is a common event in breast cancer and is associated with worse prognosis of triple-negative breast cancer (TNBC) and basal-like breast cancer (BLBC). Despite recent progress, the role of WWOX in driving breast carcinogenesis remains unknown. Here we report that ablation of Wwox in mammary tumor-susceptible mice results in increased tumorigenesis, and that the resultant tumors resemble human BLBC. Interestingly, copy number loss of Trp53 and downregulation of its transcript levels were observed in the Wwox knockout tumors. Moreover, tumors isolated from Wwox and Trp53 mutant mice were indistinguishable histologically and transcriptionally. Finally, we find that deletion of TP53 and WWOX co-occurred and is associated with poor survival of breast cancer patients. Altogether, our data uncover an essential role for WWOX as a bona fide breast cancer tumor suppressor through the maintenance of p53 stability.

Association between WWOX and the risk of malignant tumor, especially among Asians: evidence from a meta-analysis

Purpose

Many studies have been carried out to examine whether there are associations between WWOX polymorphisms (rs3764340 C>G, rs12918952 G>A, and rs383362 G>T) and malignant tumor risk, but the results from these studies remained inconsistent and even controversial. In the present study, we performed a meta-analysis to evaluate the relationships comprehensively.

Methods

Published reports were searched in PubMed, Google Scholar, and Chinese National Knowledge Infrastructure databases. Eight eligible case–control studies were included in the final analysis. In the analysis, pooled odds ratios (ORs) with corresponding 95% CIs were calculated in five genetic models to assess the genetic risk. Egger’s regression and Begg’s funnel plots test were conducted to appraise the publication bias.

Results

We found that rs12918952 G>A and rs383362 G>T polymorphisms were not associated with the susceptibility of malignant tumor. However, a significant correlation was found between WWOX rs3764340 C>G and malignant tumor risk in three genetic models (CG vs CC: OR=1.31, 95% CI: 1.12–1.53, P=0.031; GG/CG vs CC: OR=1.31, 95% CI: 1.11–1.54, P=0.014; G vs C: OR=1.28, 95% CI: 1.09–1.50, P=0.009). Furthermore, when stratified by source of control, the results were significant especially in population-based control for rs3764340.

Conclusion

In general, our results first indicated that the rs3764340 C>G polymorphism in WWOX gene can increase the susceptibility of tumor, while the others cannot. However, large, well-designed epidemiological studies are required to verify our findings.

Investigation of Mutations and Expression of the FHIT Gene in Turkish Patients with Brain Metastases Derived from Non-Small Cell Lung Cancer

Aims and background

Brain metastases occur in 20–40% of patients with cancer, and their frequency has increased over time. Lung, breast and skin (melanoma) are the most common sources of brain metastases. Recent studies show that several genes such as CD44 and PTEN have roles in the suppression of metastatic growth. Although it has been determined that there is a relationship between the FHIT gene and several primary tumors, its role in the initiation and progression of brain tumors has not yet been entirely explained. Furthermore, it is not known whether the FHIT gene has a role in the formation of brain metastases.

Patients and methods

The present study investigated mutations of the FHIT gene in Turkish patients with brain metastases derived from non-small cell lung cancer (NSCLC). Single-strand conformational polymorphism and sequencing analysis of the coding exons (5–9) of the FHIT gene were performed on 26 tissues. Furthermore, the level of Fhit protein expression of 36 tumor tissues was identified by immunohistochemistry.

Results

Using single-strand conformational polymorphism and sequencing analyses, no point mutations of the FHIT gene were detected in brain metastases derived from NSCLC. However, it was observed that Fhit protein expression was reduced in 88.9% of subjects.

Conclusions

We suggest that the FHIT gene may be turned off in brain metastases via other genetic/epigenetic mechanisms rather than mutations.

Relationship of genetic variant distributions of WW domain-containing oxidoreductase gene with uterine cervical cancer

To our knowledge, no study investigates the association of genetic variant distributions of WW domain-containing oxidoreductase (WWOX) gene with development of invasive cancer, clinicopathologic variables and patient survival in uterine cervical cancer for Taiwanese women. We therefore conducted this study to explore the clinical involvements of WWOX single nucleotide polymorphisms (SNPs) in cervical cancer. One hundred and thirty-one patients with cervical invasive cancer and 93 patients with precancerous lesions as well as 316 control women were consecutively enrolled. The genotypic frequencies of WWOX genetic variants rs73569323, rs383362, rs11545028, rs3764340 and rs12918952 were determined by real-time polymerase chain reaction. The results revealed that only WWOX SNP rs3764340 was associated between patients with cervical invasive cancer and normal controls among 5 WWOX genetic variants. Cervical cancer patients with genotypes GA/AA in WWOX SNP rs12918952 were associated with parametrium invasion and pelvic lymph node metastasis. Univariate analysis found that WWOX SNPs rs73569323 and rs11545028 were associated with patient survival, whereas multivariate analysis revealed CT/TT in rs11545028 was the only genetic variant, which could predict better overall survival, among 5 WWOX SNPs in Taiwan. In conclusion, Taiwanese women with CG/GG in WWOX SNP rs3764340 are susceptible to cervical invasive cancer. Cervical cancer patients with GA/AA in rs12918952 tend to have more risk to develop parametrium invasion and pelvic lymph node metastasis. Among 5 WWOX SNPs, rs11545028 is the only genetic variant associated with patient survival, in which CT/TT could predict better overall survival in Taiwanese women.

Fhit down-regulation is an early event in pancreatic carcinogenesis

Aberrant Fhit expression characterizes a large proportion of primary pancreatic ductal adenocarcinomas (PDACs), but fragmentary information is available on Fhit expression during the phenotypic changes of pancreatic ductal epithelium during multistep transformation. We assessed Fhit expression by immunohistochemistry in two different multistep pancreatic carcinogenic processes: pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasia (IPMN). We considered 105 surgically treated PDACs/IPMNs and selected 30 samples of non-neoplastic pancreatic parenchyma, 50 PanIN lesions, 30 IPMNs, 15 IPMNs with associated invasive carcinoma, and 60 adenocarcinomas. Normal pancreatic ducts and surrounding acinar cells consistently showed moderate to strong Fhit immunoreactivity. Significant down-regulation of Fhit expression was observed in association with increasing severity of dysplastia/neoplastia in both carcinogenic processes. This was further confirmed by studying multiple lesions obtained from the same surgical specimen. Of 60 PDACs, only 14 showed Fhit expression comparable to normal pancreatic ductal epithelium, while the remainder (77%) showed clearly negative or reduced Fhit expression. This study demonstrates that Fhit down-regulation is an early event in both multistep carcinogenic processes leading to PDAC.

Functional genetic variant of WW domain-containing oxidoreductase (WWOX) gene is associated with hepatocellular carcinoma risk

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. Human WW domain-containing oxidoreductase (WWOX) gene has been identified as a tumor suppressor gene in multiple cancers. We hypothesize that genetic variations in WWOX are associated with HCC risk.

METHODOLOGY/PRINCIPAL FINDINGS

Five single-nucleotide polymorphisms (SNPs) of the WWOX gene were evaluated from 708 normal controls and 354 patients with HCC. We identified a significant association between a WWOX single nucleotide polymorphism (SNP), rs73569323, and decreased risk of HCC. After adjustment for potential confounders, patients with at least one T allele at rs11545028 of WWOX may have a significantly smaller tumor size, reduced levels of α-fetoprotein and alanine aminotransferase (ALT). Moreover, the A allele at SNP rs12918952 in WWOX conferred higher risk of vascular invasion. Additional in silico analysis also suggests that WWOX rs12918952 polymorphism tends to affect WWOX expression, which in turn contributes to tumor vascular invasion.

CONCLUSIONS

In conclusion, genetic variations in WWOX may be a significant predictor of early HCC occurrence and a reliable biomarker for disease progression.

Wwox-Brca1 interaction: role in DNA repair pathway choice

In this study, loss of expression of the fragile site-encoded Wwox protein was found to contribute to radiation and cisplatin resistance of cells, responses that could be associated with cancer recurrence and poor outcome. WWOX gene deletions occur in a variety of human cancer types, and reduced Wwox protein expression can be detected early during cancer development. We found that Wwox loss is followed by mild chromosome instability in genomes of mouse embryo fibroblast cells from Wwox-knockout mice. Human and mouse cells deficient for Wwox also exhibit significantly enhanced survival of ionizing radiation and bleomycin treatment, agents that induce double-strand breaks (DSBs). Cancer cells that survive radiation recur more rapidly in a xenograft model of irradiated breast cancer cells; Wwox-deficient cells exhibited significantly shorter tumor latencies vs Wwox-expressing cells. This Wwox effect has important consequences in human disease: in a cohort of cancer patients treated with radiation, Wwox deficiency significantly correlated with shorter overall survival times. In examining mechanisms underlying Wwox-dependent survival differences, we found that Wwox-deficient cells exhibit enhanced homology directed repair (HDR) and decreased non-homologous end-joining (NHEJ) repair, suggesting that Wwox contributes to DNA DSB repair pathway choice. Upon silencing of Rad51, a protein critical for HDR, Wwox-deficient cells were resensitized to radiation. We also demonstrated interaction of Wwox with Brca1, a driver of HDR, and show via immunofluorescent detection of repair proteins at ionizing radiation-induced DNA damage foci that Wwox expression suppresses DSB repair at the end-resection step of HDR. We propose a genome caretaker function for WWOX, in which Brca1-Wwox interaction supports NHEJ as the dominant DSB repair pathway in Wwox-sufficient cells. Taken together, the experimental results suggest that reduced Wwox expression, a common occurrence in cancers, dysregulates DSB repair, enhancing efficiency of likely mutagenic repair, and enabling radiation and cisplatin treatment resistance.

Ectopic WWOX Expression Inhibits Growth of 5637 Bladder Cancer Cell In Vitro and In Vivo

WW domain-containing oxidoreductase (WWOX) gene located in the common fragile site FRA16D region exhibits loss or reduction of expression in multiple types of carcinomas including bladder cancer. However, the role of WWOX in the tumorigenesis and development of bladder cancer remains elusive. In this study, WWOX overexpression construct was transfected into 5637 bladder cancer cell line in which WWOX expression was compromised. Constitutive expression of ectopic WWOX in 5637 cells suppressed cell proliferation and cell cycle progression, which was associated with downregulation of Cyclin B, D1, and E. Moreover, WWOX overexpression promoted apoptosis in 5637 cells and resulted in upregulation of Bax, downregulation of Bcl-2, and elevated levels of cleaved caspase-3 and cleaved PARP, indicating activation of the intrinsic apoptosis pathway. Furthermore, WWOX overexpression suppressed tumorigenicity of 5637 cells and promoted apoptosis in the xenograft tumors as demonstrated in a xenograft mouse model. In summary, our data indicate that WWOX plays a critical role in the regulation of proliferation, cell cycle, apoptosis, and tumorigenesis of bladder cancer cells, suggesting that WWOX may have potential clinical implications in bladder cancer therapy.

Fhit loss-associated initiation and progression of neoplasia in vitro

The FHIT gene, encompassing an active common fragile site, FRA3B, is frequently silenced in preneoplasia and cancer, through gene rearrangement or methylation of regulatory sequences. Silencing of Fhit protein expression causes thymidine kinase 1 downregulation, resulting in dNTP imbalance, and spontaneous replication stress that leads to chromosomal aberrations, allele copy number variations, insertions/deletions, and single-base substitutions. Thus, Fhit, which is reduced in expression in the majority of human cancers, is a genome "caretaker" whose loss initiates genome instability in preneoplastic lesions. To follow the early genetic alterations and functional changes induced by Fhit loss that may recapitulate the neoplastic process in vitro, we established epithelial cell lines from kidney tissues of Fhit-/- and +/+ mouse pups early after weaning, and subjected cell cultures to nutritional and carcinogen stress, which +/+ cells did not survive. Through transcriptome profiling and protein expression analysis, we observed changes in the Trp53/p21 and survivin apoptotic pathways in -/- cells, and in expression of proteins involved in epithelial-mesenchymal transition. Some Fhit-deficient cell lines showed anchorage-independent colony formation and increased invasive capacity in vitro. Furthermore, cells of stressed Fhit-/- cell lines formed s.c. and metastatic tumors in nude mice. Collectively, we show that Fhit loss and subsequent thymidine kinase 1 inactivation, combined with selective pressures, leads to neoplasia-associated alterations in genes and gene expression patterns in vitro and in vivo.

Fhit and Wwox loss-associated genome instability: A genome caretaker one-two punch

Expression of Fhit and Wwox protein is frequently lost or reduced in many human cancers. In this report, we provide data that further characterizes the molecular consequences of Fhit loss in the initiation of DNA double-strand breaks (DSBs), and of Wwox loss in altered repair of DSBs. We show that loss of Fhit initiates mild genome instability in early passage mouse kidney cells, confirming that DNA damage associated with Fhit-deficiency is not limited to cancer cells. We also demonstrate that the cause of Fhit-deficient DSBs: thymidine deficiency-induced replication stress, can be resolved with thymidine supplementation in early passage mouse kidney cells before extensive genome instability occurs. As for consequences of Wwox loss in cancer, we show in a small panel of breast cancer cells and mouse embryonic fibroblasts that Wwox expression predicts response to radiation and mitomycin C, all agents that cause DSBs. In addition, loss of Wwox significantly reduced progression free survival in a cohort of ovarian cancer patients treated with platin-based chemotherapies. Finally, stratification of a cohort of squamous lung cancers by Fhit expression reveals that Wwox expression is significantly reduced in the low Fhit-expressing group, suggesting that loss of Fhit is quickly succeeded by loss of Wwox. We propose that Fhit and Wwox loss work synergistically in cancer progression and that DNA damage caused by Fhit could be targeted early in cancer initiation for prevention, while DNA damage caused by Wwox loss could be targeted later in cancer progression, particularly in cancers that develop resistance to genotoxic therapies.

Pc2-mediated SUMOylation of WWOX is essential for its suppression of DU145 prostate tumorigenesis

Tumor suppressor WW domain-containing oxidoreductase (WWOX) is depleted in various cancer types. Here we report that WWOX is modified by small ubiquitin-like modifier (SUMO) proteins and represses DU145 prostate cancer tumorigenesis in a SUMOylation-dependent manner. Ectopic WWOX was shown to associate with SUMO2/3 or E2 Ubc9. Furthermore, we revealed that WWOX SUMOylation was promoted by E3 ligase polycomb2 (Pc2), and that WWOX associated with Pc2. Meanwhile, anisomycin-induced activator protein-1 (AP-1) activity was markedly diminished by co-expression of SUMO and WWOX. Also, WWOX wild type (WT), but not WWOX SUMO mutant (K176A) markedly reduced both DU145 prostate cancer cell proliferation and xenograft tumorigenesis. Collectively, our findings demonstrate that SUMO modification of WWOX is essential for its suppressive activity for DU145 prostate cancer tumorigenesis.

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.

Roles of the WWOX in pathogenesis and endocrine therapy of breast cancer

Breast cancer is one of the most common malignancies, often with complicated etiology and poor clinical outcome. In recent years, a critical role has emerged for the WW domain-containing oxidoreductase (WWOX) in breast cancer. WWOX is a tumor suppressor; it is deleted or attenuated in 29-63.2% of breast cancer tissues and is associated with a poor prognosis of breast cancer patients. WWOX heterozygous knockout mice show a higher incidence of mammary tumors and impaired branching morphogenesis. At the molecular level, WWOX interacts with AP2γ, ErbB4, SMAD3, and WBP2 suppressing their transcription activities in breast cancer cell lines. This review provides comprehensive insights into the current knowledge of WWOX activities in the pathogenesis and endocrine therapy of breast cancer.

The tumor suppressor WW domain-containing oxidoreductase modulates cell metabolism

The WW domain-containing oxidoreductase (WWOX) encodes a tumor suppressor that is frequently altered in cancer. WWOX binds several proteins and thus is postulated to be involved in a variety of cellular processes. Interestingly, Wwox-knockout mice develop normally in utero but succumb to hypoglycemia and other metabolic defects early in life resulting in their death by 3-4 weeks of age. Cumulative evidence has linked WWOX with cellular metabolism including steroid metabolism, high-density lipoprotein cholesterol (HDL-C) metabolism, bone metabolism and, more recently, glucose metabolism. In this review, we discuss these evolving functions for WWOX and how its deletion affects cellular metabolism and neoplastic progression.

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.

Very large common fragile site genes and their potential role in cancer development

Common fragile sites (CFSs) are large chromosomal regions that are hot-spots for alterations especially within cancer cells. The three most frequently expressed CFS regions (FRA3B, FRA16D and FRA6E) contain genes that span extremely large genomic regions (FHIT, WWOX and PARK2, respectively), and these genes were found to function as important tumor suppressors. Many other CFS regions contain extremely large genes that are also targets of alterations in multiple cancers, but none have yet been demonstrated to function as tumor suppressors. The loss of expression of just FHIT or WWOX has been found to be associated with a worse overall clinical outcome. Studies in different cancers have revealed that some cancers have decreased expression of multiple large CFS genes. This loss of expression could have a profound phenotypic effect on these cells. In this review, we will summarize the known large common fragile site genes and discuss their potential relationship to cancer development.

The common fragile site FRA16D gene product WWOX: roles in tumor suppression and genomic stability

The fragile WWOX gene, encompassing the chromosomal fragile site FRA16D, is frequently altered in human cancers. While vulnerable to DNA damage itself, recent evidence has shown that the WWOX protein is essential for proper DNA damage response (DDR). Furthermore, the gene product, WWOX, has been associated with multiple protein networks, highlighting its critical functions in normal cell homeostasis. Targeted deletion of Wwox in murine models suggests its in vivo requirement for proper growth, metabolism, and survival. Recent molecular and biochemical analyses of WWOX functions highlighted its role in modulating aerobic glycolysis and genomic stability. Cumulatively, we propose that the gene product of FRA16D, WWOX, is a functionally essential protein that is required for cell homeostasis and that its deletion has important consequences that contribute to the neoplastic process. This review discusses the essential role of WWOX in tumor suppression and genomic stability and how its alteration contributes to cancer transformation.

WWOX at the crossroads of cancer, metabolic syndrome related traits and CNS pathologies

WWOX was cloned as a putative tumor suppressor gene mapping to chromosomal fragile site FRA16D. Deletions affecting WWOX accompanied by loss of expression are frequent in various epithelial cancers. Translocations and deletions affecting WWOX are also common in multiple myeloma and are associated with worse prognosis. Metanalysis of gene expression datasets demonstrates that low WWOX expression is significantly associated with shorter relapse-free survival in ovarian and breast cancer patients. Although somatic mutations affecting WWOX are not frequent, analysis of TCGA tumor datasets led to identifying 44 novel mutations in various tumor types. The highest frequencies of mutations were found in head and neck cancers and uterine and gastric adenocarcinomas. Mouse models of gene ablation led us to conclude that Wwox does not behave as a highly penetrant, classical tumor suppressor gene since its deletion is not tumorigenic in most models and its role is more likely to be of relevance in tumor progression rather than in initiation. Analysis of signaling pathways associated with WWOX expression confirmed previous in vivo and in vitro observations linking WWOX function with the TGFβ/SMAD and WNT signaling pathways and with specific metabolic processes. Supporting these conclusions recently we demonstrated that indeed WWOX behaves as a modulator of TGFβ/SMAD signaling by binding and sequestering SMAD3 in the cytoplasmic compartment. As a consequence progressive loss of WWOX expression in advanced breast cancer would contribute to the pro-metastatic effects resulting from TGFβ/SMAD3 hyperactive signaling in breast cancer. Recently, GWAS and resequencing studies have linked the WWOX locus with familial dyslipidemias and metabolic syndrome related traits. Indeed, gene expression studies in liver conditional KO mice confirmed an association between WWOX expression and lipid metabolism. Finally, very recently the first human pedigrees with probands carrying homozygous germline loss of function WWOX mutations have been identified. These patients are characterized by severe CNS related pathology that includes epilepsy, ataxia and mental retardation. In summary, WWOX is a highly conserved and tightly regulated gene throughout evolution and when defective or deregulated the consequences are important and deleterious as demonstrated by its association not only with poor prognosis in cancer but also with other important human pathologies such as metabolic syndrome and CNS related pathologic conditions.

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 cancer gene WWOX behaves as an inhibitor of SMAD3 transcriptional activity via direct binding

BACKGROUND

The WW domain containing protein WWOX has been postulated to behave as a tumor suppressor in breast and other cancers. Expression of this protein is lost in over 70% of ER negative tumors. This prompted us to investigate the phenotypic and gene expression effects of loss of WWOX expression in breast cells.

METHODS

Gene expression microarrays and standard in vitro assays were performed on stably silenced WWOX (shRNA) normal breast cells. Bioinformatic analyses were used to identify gene networks and transcriptional regulators affected by WWOX silencing. Co-immunoprecipitations and GST-pulldowns were used to demonstrate a direct interaction between WWOX and SMAD3. Reporter assays, ChIP, confocal microscopy and in silico analyses were employed to determine the effect of WWOX silencing on TGFβ-signaling.

RESULTS

WWOX silencing affected cell proliferation, motility, attachment and deregulated expression of genes involved in cell cycle, motility and DNA damage. Interestingly, we detected an enrichment of targets activated by the SMAD3 transcription factor, including significant upregulation of ANGPTL4, FST, PTHLH and SERPINE1 transcripts. Importantly, we demonstrate that the WWOX protein physically interacts with SMAD3 via WW domain 1. Furthermore, WWOX expression dramatically decreases SMAD3 occupancy at the ANGPTL4 and SERPINE1 promoters and significantly quenches activation of a TGFβ responsive reporter. Additionally, WWOX expression leads to redistribution of SMAD3 from the nuclear to the cytoplasmic compartment. Since the TGFβ target ANGPTL4 plays a key role in lung metastasis development, we performed a meta-analysis of ANGPTL4 expression relative to WWOX in microarray datasets from breast carcinomas. We observed a significant inverse correlation between WWOX and ANGPTL4. Furthermore, the WWOX(lo)/ANGPTL4(hi) cluster of breast tumors is enriched in triple-negative and basal-like sub-types. Tumors with this gene expression signature could represent candidates for anti-TGFβ targeted therapies.

CONCLUSIONS

We show for the first time that WWOX modulates SMAD3 signaling in breast cells via direct WW-domain mediated binding and potential cytoplasmic sequestration of SMAD3 protein. Since loss of WWOX expression increases with breast cancer progression and it behaves as an inhibitor of SMAD3 transcriptional activity these observations may help explain, at least in part, the paradoxical pro-tumorigenic effects of TGFβ signaling in advanced breast cancer.

Common chromosome fragile sites in human and murine epithelial cells and FHIT/FRA3B loss-induced global genome instability

Chromosomal positions of common fragile sites differ in lymphoblasts and fibroblasts, with positions dependent on the epigenetically determined density of replication origins at these loci. Because rearrangement of fragile loci and associated loss of fragile gene products are hallmarks of cancers, we aimed to map common fragile sites in epithelial cells, from which most cancers derive. Among the five most frequently activated sites in human epithelial cells were chromosome bands 2q33 and Xq22.1, which are not among top fragile sites identified in lymphoblasts or fibroblasts. FRA16D at 16q23 was among the top three fragile sites in the human epithelial cells examined, as it is in lymphoblasts and fibroblasts, while FRA3B at 3p14.2, the top fragile locus in lymphoblasts, was not fragile in most epithelial cell lines tested. Epithelial cells exhibited varying hierarchies of fragile sites; some frequent epithelial cell fragile sites are apparently not frequently altered in epithelial cancers and sites that are frequently deleted in epithelial cancers are not necessarily among the most fragile. Since we have reported that loss of expression of the FRA3B-encoded FHIT protein causes increased replication stress-induced DNA damage, we also examined the effect of FHIT-deficiency on markers of genome instability in epithelial cells. FHIT-deficient cells exhibited increases in fragile breaks and in γH2AX and 53BP1 foci in G1 phase cells, confirming in epithelial cells that the FHIT gene and encompassing FRA3B, is a "caretaker gene" necessary for maintenance of genome stability.

Upregulation of tumor suppressor WWOX promotes immune response in glioma

Previous studies demonstrate that human glioma cells could evade the host's immune surveillance system, result in aggressive proliferation. WWOX, a tumor suppressor gene affected in multiple cancers, induces tumor apoptosis and suppresses growth in vitro and in vivo. However, the effect of WWOX expression in glioma cells to immune cells is still unknown. In the present study, we transduced WWOX into human glioma cell line U251, and cocultured with Jurkat T cells together. We demonstrated that upregulation of WWOX could increase proliferation of Jurkat T cells and decrease the FasL and TGF-β expression of U251 cells, result in inhibiting apoptosis of Jurkat T cells. Therefore, our results suggested that loss of WWOX expression not only resulted in glioma carcinogenesis, but also suppressed immune cell attack by inducing Fas/FasL mediated apoptotic signaling.

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.

WWOX induces apoptosis and inhibits proliferation in cervical cancer and cell lines

Cervical cancer is the second most common gynecological malignancy, but the molecular events involved in its development remain unclear. The tumor‑suppressor gene, WW domain-containing oxidoreductase (WWOX), has been found to be lost in various types of cancers. Few studies have been reported detailing the function of WWOX in human cervical cancer; therefore we aimed to investigate the role played by WWOX in human cervical cancer. Immunohistochemistry was used to study preinvasive and invasive primary cervical cancer. Full length cDNA was transfected into HeLa cells to overexpress WWOX, and short hairpin RNA (shRNA) was transfected into SiHa cells to deplete its expression, respectively. The cellular levels of WWOX RNA and protein were detected by real-time PCR and western immunoblotting. Proliferation rates were assessed by methyl thiazolyl tetrazolium (MTT), plate colony formation and soft agar colony assays. Cellular apoptosis was measured by flow cytometry and TdT-mediated dUTP nick-end labeling (TUNEL) assay. The activity of caspase-3 and its protein levels were determined by caspase-3 activity assay and western blot analysis. Xenografts were established by injecting cells into nude mice. The results showed that WWOX expression was decreased in human cervical cancer and cervical cancer cell lines. Reconstitution of WWOX in HeLa cells inhibited their proliferation and induced apoptosis, while knockdown of WWOX in SiHa cells promoted proliferation and inhibited apoptosis. Xenografts in groups of mice verified the effect in vivo. These data suggest that underexpression of WWOX is associated with cervical cancer development. Modulation of WWOX expression may be an effective and novel method for the treatment of cervical cancer.

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.

Wwox expression may predict benefit from adjuvant tamoxifen in randomized breast cancer patients

Reduced or absent Wwox expression has recently been associated with tamoxifen resistance in breast cancer and has also been proposed as a candidate predictive marker for treatment. We aimed to investigate the correlation of Wwox expression with the outcome of tamoxifen treatment by examining tissues from 912 randomized breast cancer patients. Paraffin-embedded tissues from patient tumors were arranged on tissue microarray, and Wwox protein was stained using immunohistochemistry. After microscopic examination, the results were analyzed with Cox regression, Kaplan-Meier survival curves and the log-rank test. In the group of cases having a tumor absent for Wwox expression, there was no difference in recurrence-free survival between treated and untreated patients (P=0.81). For treated cases with a tumor expressing moderate or strong Wwox protein, recurrence-free survival was improved (P=0.001 and P=0.003, respectively). The test for interaction between Wwox and treatment response demonstrated a decreased risk of recurrence for treated patients with a moderate or strong Wwox expression (HR=0.31, 95% CI 0.10-0.98 and HR=0.28, 95% CI 0.08-0.97, respectively). Our results indicate that patients with high expression of Wwox may gain more benefit from treatment with tamoxifen.

Aberrant crypt focus and fragile histidine triad protein in sporadic colorectal carcinoma

AIM: To characterize aberrant crypt focus (ACF) in adjoining mucosa in sporadic colorectal carcinoma and to evaluate fragile histidine triad (Fhit) protein and Ki67.

METHODS: ACF was identified grossly and classified histologically in 75 resected specimens. ACF was typed into hyperplastic ACF (HACF) and dysplastic ACF (DACF). Sections of ACF, carcinoma and normal colonic mucosa as control were studied for Fhit and Ki67 expressions by immunohistochemistry and were grouped according to staining intensity and the number of positive stained cells observed in different histological groups. Comparison was done between the different groups by Pearson’s χ² test and γ test for the ordinal data. P value < 0.05 was considered as significant.

RESULTS: Age range was 40 to 86 years in males (mean = 43.36) and 45 to 70 years in females (mean = 56). HACF was identified in all cases studied in the non-tumorous colonic mucosa; ACF was observed as non-contiguous scattered foci, which supports the hypothesis of acquisition of single focus monoclonality by colonic epithelial cells in tumor generation. Twenty-four (32%) had DACF and were observed as closure to carcinoma foci. Intensity of Fhit expression: (1) HACF - 40% exhibited strong intensity, similar to normal, moderate in 36% and weak in 24%; (2) DACF - strong in 25%, moderate in 37.5% and weak in 37.5%; and (3) carcinoma - negative in 16%, strong in 43% and moderate and weak in 28.5% each. Significant difference was observed in intensity of the Fhit protein expressions by HACF and DACF (P < 0.05). Tumor in older patients showed a stronger Fhit intensity compared to younger patients (P = 0.036). Vegetarian diet intake and non-smokers showed stronger Fhit intensities. Advanced stage tumor, non-vegetarian diet and younger age was associated with loss of Fhit protein. Ki67 positivity was an extended crypt pattern in HACF and DACF showed extension up to the neck region of the crypts and surface epithelium. Carcinomas showed a marked increase in Ki67 expression (P < 0.05). Fhit protein had an inverse association with Ki67 expression.

CONCLUSION: Weaker Fhit intensity was associated with smoking, non-vegetarian diet intake and increasing Ki67 expression. Loss of Fhit protein expression is possibly influenced by environmental factors like smoking and non-vegetarian diet intake.

WWOX induces apoptosis and inhibits proliferation of human hepatoma cell line SMMC-7721

AIM: To investigate the effects of the WWOX gene on the human hepatic carcinoma cell line SMMC-7721.

METHODS: Full-length WWOX cDNA was amplified from normal human liver tissues. Full-length cDNA was subcloned into pEGFP-N1, a eukaryotic expression vector. After introduction of the WWOX gene into cancer cells using liposomes, the WWOX protein level in the cells was detected through Western blotting. Cell growth rates were assessed by methyl thiazolyl tetrazolium (MTT) and colony formation assays. Cell cycle progression and cell apoptosis were measured by flow cytometry. The phosphorylated protein kinase B (AKT) and activated fragments of caspase-9 and caspase-3 were examined by Western blotting analysis.

RESULTS: WWOX significantly inhibited cell proliferation, as evaluated by the MTT and colony formation assays. Cells transfected with WWOX showed significantly higher apoptosis ratios when compared with cells transfected with a mock plasmid, and overexpression of WWOX delayed cell cycle progression from G1 to S phase, as measured by flow cytometry. An increase in apoptosis was also indicated by a remarkable activation of caspase-9 and caspase-3 and a dephosphorylation of AKT (Thr308 and Ser473) measured with Western blotting analysis.

CONCLUSION: Overexpression of WWOX induces apoptosis and inhibits proliferation of the human hepatic carcinoma cell line SMMC-7721.

Aberrant expression of WWOX protein in epithelial ovarian cancer: a clinicopathologic and immunohistochemical study

Epithelial ovarian cancer is the most frequent cause of death from gynecologic cancer. The WW domain-containing oxidoreductase (WWOX) gene is located at 16q23.3-24.1, a region that spans the second most common human fragile site, FRA16D. Abnormalities affecting WWOX at the genomic and/or expression level(s) have been reported in numerous neoplasias and cancer-derived cell lines. The goal of the study was to evaluate WWOX protein expression in epithelial ovarian carcinoma tissues to determine whether they correlated with clincopathologic parameters. We performed WWOX expression analyses by means of immunohistochemistry on 112 epithelial ovarian carcinoma tissues, and ovarian carcinoma-derived SKOV3, 3AO cells. The basic significant level was fixed at P<0.05. Loss of WWOX expression was observed in 32 (28.6%) of 112 ovarian carcinoma samples and was positively correlated with negative estrogen receptor (ER) (P<0.001) and negative progesterone receptor (PR) (P=0.001). A statistically significant correlation was observed between the lack of WWOX expression and the advanced International Federation of Gynecology and Obstetrics (FIGO) stages (P=0.02). Furthermore, negative WWOX staining was significantly correlated with lymph node metastasis (P=0.013), whereas no significant differences were found between WWOX and HER-2/neu staining (P=0.79). WWOX protein expression was moderately detectable in SKOV3 cells but not in 3AO cells. Our results indicate that loss of WWOX expression in epithelial ovarian carcinomas correlates with negative ER, negative PR, advanced FIGO stages, and lymph node metastases.

Overexpression of WW domain-containing oxidoreductase WOX1 preferentially induces apoptosis in human glioblastoma cells harboring mutant p53

PURPOSE

Human WWOX gene encoding WW domain-containing oxidoreductase, named WWOX, FOR, or WOX1, has been studied in various types of cancer cells and shown to be a tumor suppressor with pro-apoptotic properties. Mutation or gain-of-function of p53 in glioma cells is associated with resistance to radiation therapy and poor prognosis. In this study, we overexpressed WOX1 to examine the pro-apoptotic activity against human glioblastoma cells harboring mutant p53.

METHODS

Overexpression of WOX1 in glioblastoma cell lines and apoptosis-related assays were performed.

RESULTS

Our results showed that overexpressed WOX1 induced apoptosis of glioblastoma U373MG harboring mutant p53 by causing hypoploidy and DNA fragmentation. However, ectopic WOX1 had no effect with U87MG possessing wild type p53. Unlike temozolomide, WOX1 induced apoptosis of U373MG cells via a mitochondria-independent and caspase-3-independent pathway.

CONCLUSIONS

Overexpression of WOX1 preferentially inhibited viability and induced apoptosis in human glioblastoma cells expressing mutant p53 via a mechanism independent of the intrinsic apoptotic pathway. Conceivably, the survival of human glioblastoma cells depends upon interactions between the gain-of-function of p53 and WOX1. This suggests that modulation of WOX1 expression may be a novel strategy for treating human glioblastoma cells with mutant p53.

Response of subtype-specific human breast cancer-derived cells to poly(ADP-ribose) polymerase and checkpoint kinase 1 inhibition

When DNA damage is detected, checkpoint signal networks are activated to stop the cell cycle, and DNA repair processes begin. Inhibitory compounds targeting components of DNA damage response pathways have been identified and are being used in clinical trials, in combination with chemotherapeutic agents, to enhance cancer therapy. Inhibitors of checkpoint kinases, Chk1 and Chk2, have been shown to sensitize tumor cells to DNA damaging agents, and treatment of BRCA1/2-deficient tumor cells, as well as triple negative breast cancers, with poly(ADP-ribose) polymerase (PARP) inhibitors has shown promise. But systematic studies to determine which tumor subtypes are likely to respond to these specific inhibitors have not been reported. The current study was designed to test sensitivity of specific breast cancer subtype-derived cells to two classes of these new inhibitory drugs, PARP and Chk1 inhibitors. Luminal, HER2 overexpressing, and triple negative breast cancer-derived cells were tested for sensitivity to killing by PARP inhibitors, ABT-888 and BSI-201, and Chk1 inhibitor, PF-00477736, alone or in combination with gemcitabine or carboplatin. Each of the triple negative breast cancer cell lines showed strong sensitivity to the Chk1 inhibitor, but only the BRCA1-deficient breast cancer cell lines showed sensitivity to the PARP inhibitors, suggesting that in vitro testing of cancer cell lines of specific subtypes, with panels of the different PARP and Chk1 inhibitors, will contribute to stratification of patients for clinical trials using these classes of inhibitors.

Drosophila orthologue of WWOX, the chromosomal fragile site FRA16D tumour suppressor gene, functions in aerobic metabolism and regulates reactive oxygen species

Common chromosomal fragile sites FRA3B and FRA16D are frequent sites of DNA instability in cancer, but their contribution to cancer cell biology is not yet understood. Genes that span these sites (FHIT and WWOX, respectively) are often perturbed (either increased or decreased) in cancer cells and both are able to suppress tumour growth. While WWOX has some tumour suppressor characteristics, its normal role and functional contribution to cancer has not been fully determined. We find that a significant proportion of Drosophila Wwox interactors identified by proteomics and microarray analyses have roles in aerobic metabolism. Functional relationships between Wwox and either CG6439/isocitrate dehydrogenase (Idh) or Cu–Zn superoxide dismutase (Sod) were confirmed by genetic interactions. In addition, altered levels of Wwox resulted in altered levels of endogenous reactive oxygen species. Wwox (like FHIT) contributes to pathways involving aerobic metabolism and oxidative stress, providing an explanation for the ‘non-classical tumour suppressor’ behaviour of WWOX. Fragile sites, and the genes that span them, are therefore part of a protective response mechanism to oxidative stress and likely contributors to the differences seen in aerobic glycolysis (Warburg effect) in cancer cells.

Aberrant expression of DNA damage response proteins is associated with breast cancer subtype and clinical features

Landmark studies of the status of DNA damage checkpoints and associated repair functions in preneoplastic and neoplastic cells has focused attention on importance of these pathways in cancer development, and inhibitors of repair pathways are in clinical trials for treatment of triple negative breast cancer. Cancer heterogeneity suggests that specific cancer subtypes will have distinct mechanisms of DNA damage survival, dependent on biological context. In this study, status of DNA damage response (DDR)-associated proteins was examined in breast cancer subtypes in association with clinical features; 479 breast cancers were examined for expression of DDR proteins γH2AX, BRCA1, pChk2, and p53, DNA damage-sensitive tumor suppressors Fhit and Wwox, and Wwox-interacting proteins Ap2α, Ap2γ, ErbB4, and correlations among proteins, tumor subtypes, and clinical features were assessed. In a multivariable model, triple negative cancers showed significantly reduced Fhit and Wwox, increased p53 and Ap2γ protein expression, and were significantly more likely than other subtype tumors to exhibit aberrant expression of two or more DDR-associated proteins. Disease-free survival was associated with subtype, Fhit and membrane ErbB4 expression level and aberrant expression of multiple DDR-associated proteins. These results suggest that definition of specific DNA repair and checkpoint defects in subgroups of triple negative cancer might identify new treatment targets. Expression of Wwox and its interactor, ErbB4, was highly significantly reduced in metastatic tissues vs. matched primary tissues, suggesting that Wwox signal pathway loss contributes to lymph node metastasis, perhaps by allowing survival of tumor cells that have detached from basement membranes, as proposed for the role of Wwox in ovarian cancer spread.