Frequent downregulation and loss of WWOX gene expression in human hepatocellular carcinoma

Single-cell resolved ploidy and chromosomal aberrations in nonalcoholic steatohepatitis-(NASH) induced hepatocellular carcinoma and its precursor lesions

Nonalcoholic steatohepatitis (NASH)-induced hepatocellular carcinoma (HCC) and its precursor, nonalcoholic fatty liver disease (NAFLD) are an unmet health issue due to widespread obesity. We assessed copy number changes of genes associated with hepatocarcinogenesis and oxidative pathways at a single-cell level. Eleven patients with NASH-HCC and 11 patients with NAFLD were included. Eight probes were analyzed using multiplex interphase fluorescence in situ hybridization (miFISH), single-cell imaging and phylogenetic tree modelling: Telomerase reverse transcriptase (TERT), C-Myc (MYC), hepatocyte growth factor receptor tyrosine kinase (MET), tumor protein 53 (TP53), cyclin D1 (CCND1), human epidermal growth factor receptor 2 (HER2), the fragile histidine triad gene (FHIT) and FRA16D oxidoreductase (WWOX). Each NASH-HCC tumor had up to 14 distinct clonal signal patterns indicating multiclonality, which correlated with high tumor grade. Changes frequently observed were TP53 losses, 45%; MYC gains, 36%; WWOX losses, 36%; and HER2 gains, 18%. Whole-genome duplications were frequent (82%) with aberrant tetraploid cells evolving from diploid ancestors. Non-tumorous NAFLD/NASH biopsies did not harbor clonal copy number changes. Fine mapping of NASH-HCC using single-cell multiplex FISH shows that branched tumor evolution involves genome duplication and that multiclonality increases with tumor grade. The loss of oxidoreductase WWOX and HER2 gains could be potentially associated with NASH-induced hepatocellular carcinoma.

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.

WWOX activation by toosendanin suppresses hepatocellular carcinoma metastasis through JAK2/Stat3 and Wnt/β-catenin signaling

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related deaths worldwide. Loss of WW-domain containing oxidoreductase (WWOX) has been proven to be associated with malignant metastasis in patients with HCC. In this study, by using a non-biased CRISPR knockout genetic screen targeting 19,050 human genes, we found that toosendanin (TSN) is a novel druggable WWOX candidate agonist for metastatic HCC patients. We also found that TSN exhibited significant anti-proliferative and anti-metastatic effects on HCC cells in a WWOX-dependent manner. Overexpression and knockdown of WWOX in vitro and in vivo confirmed that the suppression of HCC by TSN involved WWOX. TSN regulated Stat3, DVL2, and GSK3β by transforming their interactions with WWOX as demonstrated by a Co-IP assay. TSN accelerated the degradation of β-catenin by promoting the function of APC, AXIN1, CK1, and GSK3β complex. Nuclear translocation of p-Stat3 Y705 and β-catenin was impeded by the TSN-induced blockade of JAK2/Stat3 and Wnt/β-catenin signaling, accompanied by the inhibition of MMPs and C-MYC.

Downregulated Expression of WWOX in Cervical Carcinoma: A Case-Control Study

Integration of human papilloma virus (HPV) in human genome is a random event, and fragile sites are one of the most susceptible sites for viral integrations. WWOX (WW-domain containing oxidoreductase) gene harbours the second most common fragile site, FRA16D, and can be an important candidate for HPV integration and cervical carcinogenesis. Our aim was to evaluate the potential role of WWOX in cervical carcinogenesis. Presence of HPV and its genotype was detected by PCR in normal cervix tissues and human cervical carcinoma. The expression of WWOX transcript and its protein was examined by RT-PCR, RNA in situ hybridization, and immunoblotting. Southern blotting and sequencing were used to determine the alternative transcripts of WWOX. Statistical analysis were performed by Mann Whitney U-test, Pearson correlation coefficient test at significance level of P value < 0.05. Prevalence of HPV was observed in cervicitis (40%), cervical intraepithelial neoplasia patients (50%), and invasive cervical carcinoma patients (89.6%). Clinicopathological findings suggested a correlation of reduced level of WWOX protein and progression of cervical carcinoma deciphering its role in tumorigenesis. Furthermore, we observed aberrant WWOX transcript having deleted exon 6-8 region in invasive cervical cancer tissues as well as normal cervix samples. More than 60% of cervical carcinoma samples showed reduced protein level with an increase in wild type transcript level suggesting the involvement of a negative regulator, pAck1 (activated Cdc42- associated kinase) which might ubiquitinate WWOX protein leading to its degradation. Also, nuclear retention of WWOX transcript in invasive cervical carcinoma tissues suggests its regulation at post-transcriptional level. Our findings suggest that WWOX acts as a tumor suppressor in cervical carcinoma and could act as a potential therapeutic target for the disease.

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.

Expression of B Cell-Specific Moloney Murine Leukemia Virus Integration Site 1 (BMI-1) and WW Domain-Containing Oxidoreductase (WWOX) in Liver Cancer Tissue and Normal Liver Tissue

Background

The aim of this study was to compare the expression levels of mRNA of the B cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) and the WW domain-containing oxidoreductase (WWOX) genes and their protein products in tissues from patients with liver cancer with normal liver tissues from patients without liver cancer.

Material/Methods

The liver cancer group (N=56) included patients with available tissue samples of histologically confirmed liver cancer. The control group (N=24) included histologically confirmed normal liver tissue samples. Immunofluorescence staining and Western blot were used to detect and compare protein expression of Bmi-1 and WWOX in liver tissues in the liver cancer group and the control group. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect and compare mRNA expression of BMI-1 and WWOX in liver tissues in the liver cancer group and the control group. Expression levels of the protein and mRNA levels and the clinicopathological features including patient prognosis in liver cancer were evaluated statistically using analysis of variance (ANOVA).

Results

There were significant differences in the expression levels of protein and mRNA of BMI-1 and WWOX between the liver cancer group and the control group. BMI-1 mRNA and protein expression were significantly increased, and WWOX mRNA and protein expression were significantly reduced in liver cancer tissue, compared with normal liver tissue (p<0.05).

Conclusions

In liver cancer tissue compared with normal liver, the expression of BMI-1 and WWOX mRNA and their protein products were upregulated and down-regulated, respectively.

WWOX controls hepatic HIF1α to suppress hepatocyte proliferation and neoplasia

Liver cancer is one of the most lethal malignancies with very poor prognosis once diagnosed. The most common form of liver cancer is hepatocellular carcinoma (HCC). The WW domain-containing oxidoreductase (WWOX) is a large gene that is often perturbed in a wide variety of tumors, including HCC. WWOX has been shown to act as a tumor suppressor modulating cellular metabolism via regulating hypoxia-inducible factor 1α (HIF-1α) levels and function. Given that WWOX is commonly inactivated in HCC, we set to determine whether specific targeted deletion of murine Wwox affects liver biology and HCC development. WWOX liver-specific knockout mice (Wwox ΔHep ) showed more potent liver regeneration potential and enhanced proliferation as compared with their control littermates. Moreover, WWOX deficiency in hepatocytes combined with diethylnitrosamine treatment increased the tumor burden, which was associated with increased HIF1α levels and target gene transactivation. Inhibition of HIF1α by systemic treatment with digoxin significantly delayed HCC formation. Our work suggests that WWOX inactivation has a central role in promoting HCC through rewiring of cellular metabolism and modulating proliferation.

Oncogenic roles of the SETDB2 histone methyltransferase in gastric cancer

SETDB2 is a histone H3 lysine 9 (H3K9) tri-methyltransferase that is involved in transcriptional gene silencing. Since it is still unknown whether SETDB2 is linked to carcinogenesis, we studied alterations and functions of SETDB2 in human gastric cancers (GCs). SETDB2 protein was highly expressed in 30 of 72 (41.7%) primary GC tissues compared with their normal counterparts by immunohistochemistry. SETDB2 overexpression was significantly associated with the late stage of GCs (P<0.05) and poor prognosis of GC patients (P<0.05). The GC cell lines with SETDB2 knockdown and overexpression significantly decreased and increased cell proliferation, migration and invasion, respectively (P<0.05). Knockdown of SETDB2 in MKN74 and MKN45 cells reduced global H3K9 tri-methylation (me3) levels. Microarray analysis indicated that expression of WWOX and CADM1, tumor suppressor genes, was significantly enhanced in MKN74 cells after SETDB2 knockdown. Chromatin immunoprecipitation assays showed that the H3K9me3 levels at the promoter regions of these two genes corresponded to the SETDB2 expression levels in GC cells. Moreover, ectopic SETDB2 protein was recruited to their promoter regions. Our data suggest that SETDB2 is associated with transcriptional repression of WWOX and CADM1, and hence overexpression of SETDB2 may contribute to GC progression.

Combinations of single nucleotide polymorphisms WWOX-rs13338697, GALNT14-rs9679162 and rs6025211 effectively stratify outcomes of chemotherapy in advanced hepatocellular carcinoma

AIM

A genome-wide association study (GWAS) had identified a single nucleotide polymorphism (SNP), GALNT14-rs9679162, capable of predicting chemotherapy responses in advanced hepatocellular carcinoma (HCC). Here, we revisited the GWAS database to search for necessary SNPs that could improve our outcome prediction.

METHODS

A cohort of 116 HCC patients receiving split-dose chemotherapy composed of 5-fluorouracil, mitoxantrone and cisplatin was enrolled. The GALNT14-rs9679162 together with four other leading candidate SNPs (rs6025211, rs715171, LOC105369482-rs1955024 and WWOX-rs13338697) was genotyped and correlated with time-to-tumor progression (TTP) and overall survival (OS).

RESULTS

GALNT14-rs9679162-TT genotype remained an effective predictor for favorable TTP and OS (P = 0.012 and 0.002). Additionally, it was found that WWOX-rs13338697-CT genotype was associated with unfavorable TTP (P = 0.031), independent of GALNT14-rs9679162 genotype (adjusted P = 0.045), and rs6025211-CT genotype was associated with unfavorable OS (P = 0.014), independent of GALNT14-rs9679162 genotype (adjusted P = 0.025). Combinations of these SNPs stratified patients into three groups with differential treatment outcomes. Patients with GALNT14-rs9679162-TT/WWOX-rs13338697-non-CT genotypes achieved the most favorable treatment outcomes (n = 19; median TTP, median OS and response rate were 3.9 months, 6.8 months and 4/19 [21.1%], respectively); whereas patients with GALNT14-rs9679162-non-TT/rs6025211-CT genotypes associated with the most unfavorable treatment outcomes (n = 40; median TTP, median OS and response rate were 1.9 months, 3.5 months and 1/40 [2.5%], respectively). The remaining patients constituted a third subgroup with intermediate clinical outcomes.

CONCLUSIONS

Three genetic variants, GALNT14-rs9679162, WWOX-rs13338697 and rs6025211, stratified advanced HCC patients into three groups with differential treatment outcomes.

Atypical regulators of Wnt/β-catenin signaling as potential therapeutic targets in Hepatocellular Carcinoma

Hepatocellular carcinoma is one of the most common causes of cancer-related death worldwide. Hepatocellular carcinoma development depends on the inhibition and activation of multiple vital pathways, including the Wnt signaling pathway. The Wnt/β-catenin pathway lies at the center of various signaling pathways that regulate embryonic development, tissue homeostasis and cancers. Activation of the Wnt/β-catenin pathway has been observed frequently in hepatocellular carcinoma. However, activating mutations in β-catenin, Axin and Adenomatous Polyposis Coli only contribute to a portion of the Wnt signaling hyper-activation observed in hepatocellular carcinoma. Therefore, besides mutations in the canonical Wnt components, there must be additional atypical regulation or regulators during Wnt signaling activation that promote liver carcinogenesis. In this mini-review, we have tried to summarize some of these well-established factors and to highlight some recently identified novel factors in the Wnt/β-catenin signaling pathway in hepatocellular carcinoma. Impact statement Early recurrence of human hepatocellular carcinoma (HCC) is a frequent cause of poor survival after potentially curative liver resection. Among the deregulated signaling cascades in HCC, evidence indicates that alterations in the Wnt/β-catenin signaling pathway play key roles in hepatocarcinogenesis. In this review, we summarize the potential molecular mechanisms how the microtubule-associated Protein regulator of cytokinesis 1 (PRC1), a direct Wnt signaling target previously identified in our laboratory to be up-regulated in HCC, in promoting cancer proliferation, stemness, metastasis and tumorigenesis through a complex regulatory circuitry of Wnt3a activities.

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.

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.

Deregulated WWOX is involved in a negative feedback loop with microRNA-214-3p in osteosarcoma

WW domain-containing oxidoreductase (WWOX) is frequently inactivated in human osteosarcoma, and the restoration of its expression can suppress tumorigenicity in WWOX-negative OS cells. However, its regulatory mechanisms remain to be fully elucidated. In the present study, we demonstrate that WWOX is downregulated and that it regulates proliferation and epithelial-to-mesenchymal transition (EMT)-associated protein expression in osteosarcoma. As shown by our results, WWOX overexpression by transfection with WWOX overexpression plasmids suppressed the proliferation, migration and invasion of osteosarcoma MG63 cells (as shown by MTT and migration and invasion assays). The silencing of microRNA (miR)‑214‑3p by transfection with anti-miR‑14‑3p upregulated WWOX protein expression and also inhibited the proliferation, migration and invasion of osteosarcoma cells. Additionally, we found that WWOX negatively regulated miR‑214‑3p and miR‑10b expression. Our findings define a negative feedback pathway in control of WWOX and miR‑214‑3p expression, thus providing novel molecular targets for the treatment of osteosarcoma.

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.

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.

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

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

Expression of WW domain-containing oxidoreductase WWOX in pterygium

PURPOSE

Pterygium was traditionally regarded as a degenerative disease, but certain characteristics suggest that pterygium is probably premalignant tissue. The human WWOX gene, encoding the WW domain containing oxidoreductase (WWOX, FOR, or WOX1), is a candidate tumor suppressor gene. In this study, we investigated the WWOX gene and protein expression in pterygium.

METHODS

Pterygium tissues were obtained from patients (n=16, primary=8, recurrent=8) who received surgical excisions. Each tissue sample was further divided into head and body regions. The WWOX gene and protein expression were examined with immunohistochemistry, western blot, and quantitative PCR. For comparison, normal superior temporal bulbar conjunctivas were used as controls.

RESULTS

Compared to the controls, upregulation of WWOX and its Tyr33 phosphorylation was observed in the head region of all pterygium specimens. In the head and body of the pterygium specimens, WWOX expression was significantly higher than in the controls. In addition, WWOX expression was stronger in recurrent pterygia than in primary pterygia.

CONCLUSIONS

Increased WWOX expression, especially in the head region, is probably due to the invasiveness of the pterygium. Our results indicate that WWOX may play a role in pterygium progression and recurrence.

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, 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.

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.

Overexpression of activated Cdc42-associated kinase1 (Ack1) predicts tumor recurrence and poor survival in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers in China. Recent research suggested that activated Cdc42-associated kinase 1 (Ack1) played an important role in facilitating tumorigenesis, tumor invasion and metastasis. However, the role of Ack1 in HCC is not clear. Herein, the expression level of Ack1 mRNA in 30 fresh HCC specimens (carcinoma, peri-carcinoma and distal-carcinoma tissues) was detected by reverse transcription-polymerase chain reaction (RT-PCR), while the expression of Ack1 protein in 18 fresh HCC specimens (carcinoma, peri-carcinoma and distal-carcinoma tissues) was analyzed by Western blotting. Immunohistochemical (IHC) staining was also employed to assess both the expression level and distribution of Ack1 protein in HCC tissues collected from 173 lesions, so as to study the correlations between Ack1 protein expression and other HCC-related clinicopathologic parameters. The results showed that both Ack1 mRNA and protein were significantly over-expressed in HCC tissues than that of either peri-carcinoma or distal-carcinoma tissues (P < 0.001, P = 0.012, respectively), while there was no significant difference between peri-carcinoma and distal-carcinoma tissues. Furthermore, the results of IHC indicated that the rates of Ack1 expressions in the patients with capsular invasion, hepatic vessel involvement and recurrence were higher than without above three conditions (P = 0.037, P = 0.036, P = 0.019, respectively), whereas the patients with overexpression of Ack1 protein had low survival rate (P = 0.007). Ack1 expression, tumor size and recurrence were independently related to survival (P = 0.014, P = 0.018, P < 0.001, respectively). Thus, the level of Ack1 is associated with tumor invasion potential, and the expression of Ack1 plays an important role as predictor of recurrence and poor outcome in HCC patients.

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

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

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.

Upregulation of the putative oncogene COTE1 contributes to human hepatocarcinogenesis through modulation of WWOX signaling

Family with sequence similarity 189, also known as COTE1, has been found to be significantly upregulated in hepatocellular carcinoma (HCC) specimens and cell lines and is associated with tumor size and differentiation. Furthermore, COTE1 contributes to hepatocellular carcinogenesis. The overexpression of COTE1 enhanced in vitro cell viability and colony formation in soft agar, and in vivo tumorigenicity of HCC-derived Focus and Huh7 cells. In contrast, COTE1 knockdown via RNAi markedly suppressed these phenotypes in YY-8103 and WRL-68 HCC cell lines. Mechanistic analyses indicated that COTE1 physically associated with WW domain-containing oxidoreductase (WWOX) and modulated WWOX tyrosine phosphorylation. The ectopic overexpression of COTE1 inhibited the WWOX-p53 signaling pathway by reducing the phosphorylation of WWOX at the Tyr33 residue in Focus cells. Conversely, COTE1 silencing activated tyrosine 33 phosphorylation of WWOX and induced WWOX-p53 mediated mitochondrial apoptosis in WRL-68 cells. In addition, COTE1 upregulation in Huh7 cells blocked the WWOX-cyclin D1 pathway via dephosphorylation of WWOX Tyr287, stimulating cell cycle progression whereas phosphorylation of Tyr287 of WWOX induced by COTE1 silencing resulted in activation of WWOX-cyclin D1 signaling, leading to cell cycle arrest in YY-8103 cells. Together, our findings suggest that the cytoplasmic protein COTE1 contributes to HCC tumorigenesis by regulating cell proliferation through the modulation of WWOX signaling.

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.

Correlation of WWOX, RUNX2 and VEGFA protein expression in human osteosarcoma

Background

To investigate associations between WW domain-containing oxidoreductase (WWOX), runt-related transcription factor 2 (RUNX2) and vascular endothelial growth factor alpha (VEGFA) in human osteosarcoma (OS).

Methods

Copy number aberrations of WWOX, RUNX2and VEGFA genes were detected by microarray comparative genomic hybridization (aCGH) in 10 fresh OS tissue samples. VEGFA gene alterations were also investigated and validated by fluorescence in situ hybridization (FISH) in 54 formalin-fixed and paraffin-embedded (FFPE) OS samples. Protein expression of WWOX, RUNX2 and VEGFA were examined in 54 FFPE OS samples by immunohistochemistry (IHC).

Results

Analysis of previously published OS aCGH data (GSE9654) and aCGH data from this study (GSE19180) identified significant deletion of WWOX in 30% (6/20) of OS samples, whilst significant increase in both RUNX2 and VEGFA gene copy numbers were detected in 55% (11/20) and 60% (12/20) of OS samples, respectively. FISH demonstrated increased VEGFA gene copy number in 65.9% (31/47) of evaluable samples, in either focal or large fragment forms. Compared with positive expression of WWOX in 38.9% of the OS samples, positive expression of RUNX2 and VEGFA protein was found in 48.1 and 75.9% of samples. Although there was no significant association between gene copy number aberration and protein expression for WWOX and RUNX2, significant positive correlation between increased VEGFA gene copy number and VEGFA protein expression was observed. Although there was no significant reverse association between WWOX and RUNX2 expression, a significantly positive relationship was observed between RUNX2 and VEGFA protein expression.

Conclusions

Our data show increased RUNX2 and VEGFA gene copy numbers and elevation of their respective proteins in human OS. Positive correlation of RUNX2 and VEGFA suggests that both increased VEGFA gene copy number and RUNX2 overexpression facilitate increased expression of VEGFA.

Expression of WWOX and FHIT is downregulated by exposure to arsenite in human uroepithelial cells

Ecological studies in Taiwan, Chile, Argentina, Bangladesh, and Mexico have confirmed significant dose-dependent associations between ingestion of arsenic-contaminated drinking water and the risk of various human malignancies. The FHIT and WWOX genes are active in common fragile sites FRA3B and FRA16D, respectively. Reduced expression of FHIT or WWOX is known to be an early indicator of carcinogen-induced cancers. However, the effect of arsenite on the expressions and molecular mechanisms of these markers is still unclear. The aims of this study were (i) to observe the expression of ATR, WWOX and FHIT proteins in urothelial carcinoma (UC) between endemic and non-endemic areas of blackfoot disease (BFD) by immunohistochemical analyses; (ii) to compare expression of these genes between arsenite-treated SV-HUC-1 human epithelial cells and rat uroepithelial cells; and (iii) to determine the role of DNMT and MEK inhibitors on expressions of WWOX and FHIT in response to arsenite in SV-HUC-1. The experiments revealed that expressions of ATR, WWOX and FHIT in UC significantly differed between BFD areas and non-BFD areas (p=0.003, 0.009 and 0.021, respectively). In fact, the results for the arsenite-treated groups showed that ATR, WWOX and FHIT are downregulated by arsenite in SV-HUC-1. However, the inhibitors suppressed the effects of arsenite on WWOX and FHIT proteins and mRNA expression. In conclusion, arsenite decreased expressions of ATR, WWOX and FHIT via ERK1/2 activation in SV-HUC-1 cells. These findings confirm that dysregulations of these markers may contribute to arsenite-induced carcinogenesis.

MYO5B is epigenetically silenced and associated with MET signaling in human gastric cancer

BACKGROUND

Our previous study has shown that MYO5B is downregulated in gastric cancer. However, the mechanism by which the expression of MYO5B was inhibited remains unknown.

METHODS

Inspection of the human MYO5B locus uncovered a large and dense CpG island within the 5' region of this gene. Methylation-specific PCR (MSP) and bisulfite sequencing (BSP) were used for determination of MYO5B promoter methylation in gastric cancer cell lines and gastric cancer samples. Involvement of histone H3 methylation in those cell lines were examined by ChIP assay.

RESULTS

The densely methylated MYO5B promoter region was confirmed by MSP and BSP. Enhanced gene expression was detected when the cells were treated with the DNA-demethylating agent 5-aza-2'-deoxycytidine (DAC) and trichostatin A (TSA), a histone deacetylase inhibitor. Knockdown of MYO5B expression in gastric cancer cells expressing endogenous MYO5B inhibits HGF-stimulated MET degradation, concomitant with sustained c-MET levels and signaling.

CONCLUSION

The results of our study showed for the first time that MYO5B is epigenetically silenced in gastric cancer cells by aberrant DNA methylation and histone modification. Inactivation of MYO5B expression in gastric cancer cells expressing endogenous MYO5B inhibits HGF-stimulated MET degradation, concomitant with sustained c-MET levels and 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 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.

The expression and significance of WWOX and β-catenin in hepatocellular carcinoma

WW domain-containing oxidoreductase (WWOX) is a novel tumor suppressor gene, and its expression is reduced in various cancers, including hepatocellular carcinoma (HCC). WWOX has been reported to be downregulated in HCC cell lines as well as in primary HCC tissues. It has been suggested that WWOX is implicated in Wnt/β-catenin pathway, which is frequently affected in HCC. The aim of this study was to evaluate the expression of WWOX, β-catenin and T-cell factor 4 (TCF4) in HCC. Our result showed that downregulation of WWOX in HCC was correlated with cytoplasmic accumulation of β-catenin. In addition, strong nuclear TCF4 expression was associated with tumor grade and stage in HCC. In conclusion, our result implied that downregulation of WWOX might lead to accumulation of cytoplasmic β-catenin and the subsequent activation of Wnt/β-catenin signaling pathway in HCC.

The polymorphisms and haplotypes of WWOX gene are associated with the risk of lung cancer in southern and eastern Chinese populations

The WW domain-containing oxidoreductase (WWOX) gene is an identified tumor suppressor gene, of which several single nucleotide polymorphisms have been reported to contribute to cancer susceptibility. We hypothesized that genetic variations in WWOX are associated with lung cancer risk. In two independent case-control studies conducted in southern and eastern Chinese, we genotyped five tagSNPs of WWOX gene (rs10220974C > T, rs3764340C > G, rs12918952G > A, rs383362G > T, and rs12828G > A) in 1,559 lung cancer cases and 1,679 controls. Logistic regression analysis showed that two tagSNPs (rs3764340C > G; rs383362G > T) were significantly associated with lung cancer risk in dominant model (rs3764340C > G, GC/GG vs. CC: adjust OR = 1.35, 95% CI = 1.11-1.65; rs383362G > T, TG + TT vs. GG: adjust OR = 1.33, 95% CI = 1.14-1.55). The haplotype analysis further shown that the haplotype "G-T" was associated with the highest increased risk of lung cancer (OR = 2.20; 95% CI = 1.43-3.37). After combined these two loci, the number of the risk genotypes was associated with increased cancer risk in a dose-response manner (Ptrend  = 3.16 × 10(-6) ). In addition, a gene-based association analysis by using VEGAS software suggested the WWOX as a susceptible gene for lung cancer (P = 0.009). However, for rs10220974C > T, rs12918952G > A, and rs12828G > A, no significant association was observed for lung cancer risk. Taken together, our data suggested that genetic variants in WWOX may be genetic biomarkers for susceptibility to lung cancer.

Role of DLC1 tumor suppressor gene and MYC oncogene in pathogenesis of human hepatocellular carcinoma: potential prospects for combined targeted therapeutics (review)

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death, and its incidence is increasing worldwide in an alarming manner. The development of curative therapy for advanced and metastatic HCC is a high clinical priority. The HCC genome is complex and heterogeneous; therefore, the identification of recurrent genomic and related gene alterations is critical for developing clinical applications for diagnosis, prognosis and targeted therapy of the disease. This article focuses on recent research progress and our contribution in identifying and deciphering the role of defined genetic alterations in the pathogenesis of HCC. A significant number of genes that promote or suppress HCC cell growth have been identified at the sites of genomic reorganization. Notwithstanding the accumulation of multiple genetic alterations, highly recurrent changes on a single chromosome can alter the expression of oncogenes and tumor suppressor genes (TSGs) whose deregulation may be sufficient to drive the progression of normal hepatocytes to malignancy. A distinct and highly recurrent pattern of genomic imbalances in HCC includes the loss of DNA copy number (associated with loss of heterozygosity) of TSG-containing chromosome 8p and gain of DNA copy number or regional amplification of protooncogenes on chromosome 8q. Even though 8p is relatively small, it carries an unusually large number of TSGs, while, on the other side, several oncogenes are dispersed along 8q. Compelling evidence demonstrates that DLC1, a potent TSG on 8p, and MYC oncogene on 8q play a critical role in the pathogenesis of human HCC. Direct evidence for their role in the genesis of HCC has been obtained in a mosaic mouse model. Knockdown of DLC1 helps MYC in the induction of hepatoblast transformation in vitro, and in the development of HCC in vivo. Therapeutic interventions, which would simultaneously target signaling pathways governing both DLC1 and MYC functions in hepatocarcinogenesis, could result in progress in the treatment of liver cancer.

Global gene profiling of spontaneous hepatocellular carcinoma in B6C3F1 mice: similarities in the molecular landscape with human liver cancer

Hepatocellular carcinoma (HCC) is an important cause of morbidity and mortality worldwide. Although the risk factors of human HCC are well known, the molecular pathogenesis of this disease is complex, and in general, treatment options remain poor. The use of rodent models to study human cancer has been extensively pursued, both through genetically engineered rodents and rodent models used in carcinogenicity and toxicology studies. In particular, the B6C3F1 mouse used in the National Toxicology Program (NTP) two-year bioassay has been used to evaluate the carcinogenic effects of environmental and occupational chemicals, and other compounds. The high incidence of spontaneous HCC in the B6C3F1 mouse has challenged its use as a model for chemically induced HCC in terms of relevance to the human disease. Using global gene expression profiling, we identify the dysregulation of several mediators similarly altered in human HCC, including re-expression of fetal oncogenes, upregulation of protooncogenes, downregulation of tumor suppressor genes, and abnormal expression of cell cycle mediators, growth factors, apoptosis regulators, and angiogenesis and extracellular matrix remodeling factors. Although major differences in etiology and pathogenesis remain between human and mouse HCC, there are important similarities in global gene expression and molecular pathways dysregulated in mouse and human HCC. These data provide further support for the use of this model in hazard identification of compounds with potential human carcinogenicity risk, and may help in better understanding the mechanisms of tumorigenesis resulting from chemical exposure in the NTP two-year carcinogenicity bioassay.

Oncogenetic tree modeling of human hepatocarcinogenesis

Classical comparative genomic hybridization (CGH) has been used to identify recurrent genomic alterations in human HCC. As hepatocarcinogenesis is considered as a stepwise process, we applied oncogenetic tree modeling on all available classical CGH data to determine occurrence of genetic alterations over time. Nine losses (1p, 4q, 6q, 8p, 9p, 13q, 16p, 16q and 17p) and ten gains (1q, 5p, 6p, 7p, 7q, 8q, 17q, 20p, 20q and Xq) of genomic information were used to build the oncogenetic tree model. Whereas gains of 1q and 8q together with losses of 8p formed a cluster that represents early etiology-independent alterations, the associations of gains at 6q and 17q as well as losses of 6p and 9p were observed during tumor progression. HBV-induced HCCs had significantly more chromosomal aberrations compared to HBV-negative tumors. Losses of 1p, 4q and 13q were associated with HBV-induced HCCs, whereas virus-negative HCCs showed an association of gains at 5p, 7, 20q and Xq. Using five aberrations that were significantly associated with tumor dedifferentiation a robust progression model of stepwise human hepatocarcinogensis (gain 1q → gain 8q → loss 4q → loss 16q → loss 13q) was developed. In silico analysis revealed that protumorigenic candidate genes have been identified for each recurrently altered hotspot. Thus, oncogenic candidate genes that are coded on chromosome arms 1q and 8q are promising targets for the prevention of malignant transformation and the development of biomarkers for the early diagnosis of human HCC that may significantly improve the treatment options and thus prognosis of HCC patients.

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.

WWOX gene and gene product: tumor suppression through specific protein interactions

The WWOX gene, an archetypal fragile gene, encompasses a chromosomal fragile site at 16q23.2, and encodes the approximately 46-kDa Wwox protein, with WW domains that interact with a growing list of interesting proteins. If the function of a protein is defined by the company it keeps, then Wwox is involved in numerous important signal pathways for bone and germ-cell development, cellular and animal growth and death, transcriptional control and suppression of cancer development. Because alterations to genes at fragile sites are exquisitely sensitive to replication stress-induced DNA damage, there has been an ongoing scientific discussion questioning whether such gene expression alterations provide a selective advantage for clonal expansion of neoplastic cells, and a parallel discussion on why important genes would be present at sites that are susceptible to inactivation. We offer some answers through a description of known WWOX functions.

Oncosuppressor proteins of fragile sites are reduced in cervical cancer

FHIT and WWOX are tumor suppressor genes that span the common fragile sites FRA3B and FRA16D, respectively. To analyze possible synergisms among these genes in cervical cancer progression, we considered 159 cervical intraepithelial neoplasias, and 58 invasive squamous cell carcinomas of the uterine cervix. All cases were previously selected as high risk HPV. FHIT and WWOX proteins were examined by immunohistochemistry and their expression was inversely correlated with precancerous vs. invasive lesions. Statistics among biological markers indicated an association between FHIT and WWOX. Protein expression of these two genes was also absent or reduced in cancer cell lines. Thus, WWOX may be considered as a novel important genetic marker in cervical cancer and the association between the altered expression of FHIT and WWOX may be a critical event in the progression of this neoplasia.

[Molecular mechanisms of hepatitis B virus-associated hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is one of the most common malignant diseases in the world. The hepatitis B virus (HBV) replicates non-cytopathically in hepatocytes, and most of the liver injury associated with this infection reflects the immune response. Epidemiological studies have clearly demonstrated that a chronic HBV infection is a major etiological factor in the development of HCC. The pathogenesis of HBV-associated HCC has been studied extensively, and the molecular changes during the malignant transformation have been identified. The main carcinogenic mechanism of HBV-associated HCC is related to the long term-inflammatory changes caused by a chronic hepatitis B infection, which might involve the integration of the HBV. Integration of the HBV DNA into the host genome occurs at the early steps of clonal tumorous expansion. The hepatitis B x protein (HBx) is a multifunctional regulatory protein that communicates directly or indirectly with a variety of host targets, and mediates many opposing cellular functions, including its function in cell cycle regulation, transcriptional regulation, signaling, encoding of the cytoskeleton and cell adhesion molecules, as well as oncogenes and tumor suppressor genes. Continued study of the mechanisms of hepatocarcinogenesis will refine our current understanding of the molecular and cellular basis for neoplastic transformations in the liver. This review summarizes the current knowledge of the mechanisms involved in HBV-associated hepatocarcinogenesis.

The JNK inhibitor SP600129 enhances apoptosis of HCC cells induced by the tumor suppressor WWOX

BACKGROUND/AIMS

The FRA16D fragile site gene WWOX is a tumor suppressor that participates in p53-mediated apoptosis. The c-jun N-terminal kinase JNK1 interacts with WWOX and inhibits apoptosis. We investigated the function of WWOX in human hepatocellular carcinoma (HCC) and the effect of JNK inhibition on WWOX-mediated apoptosis.

METHODS

Allelic imbalance on chromosome 16 was analyzed in 73 HCCs using 53 microsatellite markers. WWOX mRNA in HCC cell lines and primary HCCs was measured by real-time RT-PCR. Effects of WWOX on proliferation and apoptosis and the interaction between WWOX and JNK inhibition were examined.

RESULTS

Loss on chromosome 16 occurred in 34 of 73 HCCs. Of 11 HCC cell lines, 2 had low, 7 intermediate, and 2 had high WWOX mRNA. Of 51 primary tumors, 23 had low WWOX mRNA. Forced expression of WWOX in SNU387 cells decreased FGF2-mediated proliferation and enhanced apoptosis induced by staurosporine and the JNK inhibitor SP600129. Conversely, knockdown of WWOX in SNU449 cells using shRNA targeting WWOX increased proliferation and resistance to SP600129-induced apoptosis.

CONCLUSIONS

WWOX induces apoptosis and inhibits human HCC cell growth through a mechanism enhanced by JNK inhibition.

Loss of WWOX expression in human extrahepatic cholangiocarcinoma

OBJECTIVES

WW domain-containing oxidoreductase (WWOX) is a tumor suppressor gene that maps to the common fragile site FRA16D on chromosome 16q23.3-24.1. To investigate the role of the WWOX gene in the development of extrahepatic cholangiocarcinoma (ECC), 30 tissue samples of ECC were examined.

METHODS

Loss of heterozygosity (LOH), real time reverse transcription PCR (RT-PCR), and immunohistochemistry were used to assess the role of WWOX in cholangiocarcinoma.

RESULTS

LOH was observed in 50% of cases, loss of mRNA was observed in 46.67% of the cases and loss of WWOX protein expression was found in 56.67% of ECC tissue samples. LOH, mRNA, and protein expression had a significant correlation with histological grading. The correlation coefficients were -0.623, -0.475 and -0.543, respectively. However, WWOX expression had no correlations with other clinicopathological factors such as age, gender, clinical staging or the status of preoperative hepatic function (p > 0.05). Poorly differentiated ECC had significantly lower expression of WWOX than that of moderately or well differentiated ones (p < 0.05).

CONCLUSIONS

Loss of WWOX may be involved in the tumorigenesis of extrahepati cholangiocarcinoma.

Low levels of WWOX protein immunoexpression correlate with tumour grade and a less favourable outcome in patients with urinary bladder tumours

AIMS

To correlate the immunohistochemical detection of WWOX with histological measures and disease progression within the whole spectrum of urothelial bladder neoplasms.

METHODS AND RESULTS

One hundred and one patients with primary bladder tumours were retrospectively analysed. Immunohistochemically, a polyclonal antibody was utilized and the level of WWOX protein expression was analysed by using a combined score system based on intensity of the reaction and percentage of immunoreactive tumour cells. WWOX protein expression was consistently expressed in non-neoplastic urothelium, whereas a progressive loss of immunoreactivity was observed as tumour grade and stage increased (P < 0.05). Principal component analysis showed that reduced WWOX immunoexpression was significantly associated with high histological grades (P = 0.001), advanced stage (P = 0.002), tumour size (P = 0.04) and cancer progression (P = 0.028). Invasive urothelial carcinomas of the bladder with squamous metaplasia presented the lowest levels of WWOX protein. Kaplan-Meier analyses demonstrated a significant correlation between loss of WWOX expression and a shorter progression-free survival (P = 0.042), whereas the prediction of overall survival achieved borderline significance (P = 0.053).

CONCLUSION

Loss of WWOX immunoexpression strongly correlates with classical clinicopathological factors and appears to be a potential predictive marker of progressive disease.

Tumor suppressor and hepatocellular carcinoma

A few signaling pathways are driving the growth of hepatocellular carcinoma. Each of these pathways possesses negative regulators. These enzymes, which normally suppress unchecked cell proliferation, are circumvented in the oncogenic process, either the over-activity of oncogenes is sufficient to annihilate the activity of tumor suppressors or tumor suppressors have been rendered ineffective. The loss of several key tumor suppressors has been described in hepatocellular carcinoma. Here, we systematically review the evidence implicating tumor suppressors in the development of hepatocellular carcinoma.

DMD and IL1RAPL1: two large adjacent genes localized within a common fragile site (FRAXC) have reduced expression in cultured brain tumors

Common fragile sites (CFSs) are large regions of profound genomic instability found in all individuals. Spanning the center of the two most frequently expressed CFS regions, FRA3B (3p14.3) and FRA16D (16q23.2), are the 1.5 Mb FHIT gene and the 1.0 Mb WWOX gene. These genes are frequently deleted and/or altered in many different cancers. Both FHIT and WWOX have been demonstrated to function as tumor suppressors, both in vitro and in vivo. A number of other large CFS genes have been identified and are also frequently inactivated in multiple cancers. Based on these data, several additional very large genes were tested to determine if they were derived from within CFS regions, but DCC and RAD51L1 were not. However, the 2.0 Mb DMD gene and its immediately distal neighbor, the 1.8 Mb IL1RAPL1 gene are CFS genes contained within the FRAXC CFS region (Xp21.2-->p21.1). They are abundantly expressed in normal brain but were dramatically underexpressed in every brain tumor cell line and xenograft (derived from an intracranial model of glioblastoma multiforme) examined. We studied the expression of eleven other large CFS genes in the same panel of brain tumor cell lines and xenografts and found reduced expression of multiple large CFS genes in these samples. In this report we show that there is selective loss of specific large CFS genes in different cancers that does not appear to be mediated by the relative instability within different CFS regions. Further, the inactivation of multiple large CFS genes in xenografts and brain tumor cell lines may help to explain why this type of cancer is highly aggressive and associated with a poor clinical outcome.