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.     

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.     

WWOX,large common fragile site genes,and cancer

WWOX is a gene that spans an extremely large chromosomal region. It is derived from within chromosomal band 16q23.2 which is a region with frequent deletions and other alterations in a variety of different cancers. This chromosomal band also contains the FRA16D common fragile site (CFS). CFSs are chromosomal regions found in all individuals which are highly unstable. WWOX has also been demonstrated to function as a tumor suppressor that is involved in the development of many cancers. Two other highly unstable CFSs, FRA3B (3p14.2) and FRA6E (6q26), also span extremely large genes, FHIT and PARK2, respectively, and these two genes are also found to be important tumor suppressors. There are a number of interesting similarities between these three large CFS genes. In spite of the fact that they are derived from some of the most unstable chromosomal regions in the genome, they are found to be highly evolutionarily conserved and the chromosomal region spanning the mouse homologs of both WWOX and FHIT are also CFSs in mice. Many of the other CFSs also span extremely large genes and many of these are very attractive tumor suppressor candidates. WWOX is therefore a member of a very interesting family of very large CFS genes.     

WWOX suppresses prostate cancer cell progression through cyclin D1-mediated cell cycle arrest in the G1 phase

WW domain-containing oxidoreductase (WWOX) has been reported to be a tumor suppressor in multiple cancers, including prostate cancer. WWOX can induce apoptotic responses to inhibit tumor progression, and the other mechanisms of WWOX in tumor suppression have also been reported recently. In this study, we found significant down-regulation of WWOX in prostate cancer specimens and prostate cancer cell lines compared with the normal controls. In addition, an ectopically increased WWOX expression repressed tumor progression both in vitro and in vivo. Interestingly, overexpression of WWOX in 22Rv1 cells led to cell cycle arrest in the G1 phase but did not affect sub-G1 in flow cytometry. GFP-WWOX overexpressed 22Rv1 cells were shown to inhibit cell cycle progression into mitosis under nocodazole treatment in flow cytometry, immunoblotting and GFP fluorescence. Further, cyclin D1 but not apoptosis correlated genes were down-regulated by WWOX both in vitro and in vivo. Restoration of cyclin D1 in the WWOX-overexpressed 22Rv1 cells could abolish the WWOX-mediated tumor repression. In addition, WWOX impair c-Jun-mediated cyclin D1 promoter activity. These results suggest that WWOX inhibits prostate cancer progression through negatively regulating cyclin D1 in cell cycle lead to G1 arrest. In summary, our data reveal a novel mechanism of WWOX in tumor suppression.     

WWOX suppresses prostate cancer cell progression through cyclin D1-mediated cell cycle arrest in the G1 phase

WW domain-containing oxidoreductase (WWOX) has been reported to be a tumor suppressor in multiple cancers, including prostate cancer. WWOX can induce apoptotic responses to inhibit tumor progression, and the other mechanisms of WWOX in tumor suppression have also been reported recently. In this study, we found significant down-regulation of WWOX in prostate cancer specimens and prostate cancer cell lines compared with the normal controls. In addition, an ectopically increased WWOX expression repressed tumor progression both in vitro and in vivo. Interestingly, overexpression of WWOX in 22Rv1 cells led to cell cycle arrest in the G1 phase but did not affect sub-G1 in flow cytometry. GFP-WWOX overexpressed 22Rv1 cells were shown to inhibit cell cycle progression into mitosis under nocodazole treatment in flow cytometry, immunoblotting and GFP fluorescence. Further, cyclin D1 but not apoptosis correlated genes were down-regulated by WWOX both in vitro and in vivo. Restoration of cyclin D1 in the WWOX-overexpressed 22Rv1 cells could abolish the WWOX-mediated tumor repression. In addition, WWOX impair c-Jun-mediated cyclin D1 promoter activity. These results suggest that WWOX inhibits prostate cancer progression through negatively regulating cyclin D1 in cell cycle lead to G1 arrest. In summary, our data reveal a novel mechanism of WWOX in tumor suppression.     

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.     

Helicobacter pylori infection promotes methylation of WWOX gene in human gastric cancer

WW domain-containing oxidoreductase (WWOX), a tumor suppressor gene, was reported to be downregulated in gastric cancer and other tumors. However, the mechanism by which WWOX is inactivated remains unclear. In our study, methylation status of WWOX was determined by MSP and sequencing. Our results showed that WWOX hypermethylation was frequently detected in gastric cancer, and also significantly correlated with Helicobacter pylori (H. pylori) infection. Promoter methylation of WWOX was induced in BCG823 and AGS cells co-cultured with H. pylori. Finally, we found that expression of DNMT1 and DNMT3A were enhanced when cells were co-cultured with H. pylori. Our study indicated that H. pylori infection promoted methylation of WWOX gene in gastric cancer.     

Pleiotropic Functions of Tumor Suppressor WWOX in Normal and Cancer Cells

WW domain-containing oxidoreductase (WWOX), originally marked as a likely tumor suppressor gene, has over the years become recognized for its role in a much wider range of cellular activities. Phenotypic effects displayed in animal studies, along with resolution of WWOX''s architecture, fold, and binding partners, point to the protein''s multifaceted biological functions. Results from a series of complementary experiments seem to indicate WWOX''s involvement in metabolic regulation. More recently, clinical studies involving cases of severe encephalopathy suggest that WWOX also plays a part in controlling CNS development, further expanding our understanding of the breadth and complexity of WWOX behavior. Here we present a short overview of the various approaches taken to study this dynamic gene, emphasizing the most recent findings regarding WWOX''s metabolic- and CNS-associated functions and their underlying molecular basis.     

TIAF1 self-aggregation in peritumor capsule formation, spontaneous activation of SMAD-responsive promoter in p53-deficient environment, and cell death

Self-aggregation of transforming growth factor β (TGF-β)1-induced antiapoptotic factor (TIAF1) is known in the nondemented human hippocampus, and the aggregating process may lead to generation of amyloid β (Aβ) for causing neurodegeneration. Here, we determined that overexpressed TIAF1 exhibits as aggregates together with Smad4 and Aβ in the cancer stroma and peritumor capsules of solid tumors. Also, TIAF1/Aβ aggregates are shown on the interface between brain neural cells and the metastatic cancer cell mass. TIAF1 is upregulated in developing tumors, but may disappear in established metastatic cancer cells. Growing neuroblastoma cells on the extracellular matrices from other cancer cell types induced production of aggregated TIAF1 and Aβ. In vitro induction of TIAF1 self-association upregulated the expression of tumor suppressors Smad4 and WW domain-containing oxidoreductase (WOX1 or WWOX), and WOX1 in turn increased the TIAF1 expression. TIAF1/Smad4 interaction further enhanced Aβ formation. TIAF1 is known to suppress SMAD-regulated promoter activation. Intriguingly, without p53, self-aggregating TIAF1 spontaneously activated the SMAD-regulated promoter. TIAF1 was essential for p53-, WOX1- and dominant-negative JNK1-induced cell death. TIAF1, p53 and WOX1 acted synergistically in suppressing anchorage-independent growth, blocking cell migration and causing apoptosis. Together, TIAF1 shows an aggregation-dependent control of tumor progression and metastasis, and regulation of cell death.     

High plasma concentrations of acyl-coenzyme A binding protein (ACBP) predispose to cardiovascular disease: Evidence for a phylogenetically conserved proaging function of ACBP

Autophagy defects accelerate aging, while stimulation of autophagy decelerates aging. Acyl-coenzyme A binding protein (ACBP), which is encoded by a diazepam-binding inhibitor (DBI), acts as an extracellular feedback regulator of autophagy. As shown here, knockout of the gene coding for the yeast orthologue of ACBP/DBI (ACB1) improves chronological aging, and this effect is reversed by knockout of essential autophagy genes (ATG5, ATG7) but less so by knockout of an essential mitophagy gene (ATG32). In humans, ACBP/DBI levels independently correlate with body mass index (BMI) as well as with chronological age. In still-healthy individuals, we find that high ACBP/DBI levels correlate with future cardiovascular events (such as heart surgery, myocardial infarction, and stroke), an association that is independent of BMI and chronological age, suggesting that ACBP/DBI is indeed a biomarker of “biological” aging. Concurringly, ACBP/DBI plasma concentrations correlate with established cardiovascular risk factors (fasting glucose levels, systolic blood pressure, total free cholesterol, triglycerides), but are inversely correlated with atheroprotective high-density lipoprotein (HDL). In mice, neutralization of ACBP/DBI through a monoclonal antibody attenuates anthracycline-induced cardiotoxicity, which is a model of accelerated heart aging. In conclusion, plasma elevation of ACBP/DBI constitutes a novel biomarker of chronological aging and facets of biological aging with a prognostic value in cardiovascular disease.     

Introduction to the Thematic Minireview Series on Enzyme Evolution

In this thematic minireview series, the JBC presents five provocative articles on Enzyme Evolution. The reviews discuss stimulating concepts that include the emergence of primordial catalysts at temperatures that were considerably warmer than present day ones and the impact of the cooling environment on the evolution of catalytic fitness and the preservation of catalysis-promoting conformational dynamics. They also discuss the use of Urzymes or invariant modules in enzyme superfamilies as paradigms for understanding the evolution of catalytic efficiency and specificity, the use of bioinformatics approaches to understand the roles of substrate ambiguity and catalytic promiscuity as drivers of evolution, and the challenges associated with assigning catalytic function as the number of superfamily members grows rapidly.     

Centrosomal protein FOR20 is essential for S-phase progression by recruiting Plk1 to centrosomes

Centrosomes are required for efficient cell cycle progression mainly by orchestrating microtubule dynamics and facilitating G1/S and G2/M transitions. However, the role of centrosomes in S-phase progression is largely unknown. Here, we report that depletion of FOR20 (FOP-related protein of 20 kDa), a conserved centrosomal protein, inhibits S-phase progression and prevents targeting of Plk1 (polo-like kinase 1) to centrosomes, where FOR20 interacts with Plk1. Ablation of Plk1 also significantly induces S-phase defects, which are reversed by ectopic expression of Plk1, even a kinase-dead mutant, but not a mutant that fails to localize to centrosomes. Exogenous expression of centrosome-tethered Plk1, but not wild-type Plk1, overrides FOR20 depletion-induced S-phase defects independently of its kinase activity. Thus, these data indicate that recruitment of Plk1 to centrosomes by FOR20 may act as a signal to license efficient progression of S-phase. This represents a hitherto uncharacterized role of centrosomes in cell cycle regulation.     

Introduction to Thematic Series: Protein Interactions,Structures, and Networks

Protein interactions are fundamental to the proper functioning of cells, and aberrant formation or regulation of protein interactions is at the heart of many diseases, including cancer. The advancement of methods to study the identity, function, and regulation of protein complexes makes possible the understanding of how those complexes malfunction in human diseases. New methodologies in mass spectrometry, microscopy, and protein structural analysis are rapidly advancing the amount and quality of the data, as well as the level of detail that can be obtained from experiments. With this progress, the questions that can be addressed and the biological landscape are changing. This series of minireviews highlights methodological advances and how they have been applied in novel ways to explore the function and regulation of pathways and dynamic networks in cells.