The WWOX gene in brain development and pathology.

IMPACT STATEMENT: WW domain-containing oxidoreductase encoded by the WWOX gene is a transcription regulator and a key player in a number of cellular and biological processes such as tumor suppression, cell proliferation, apoptosis induction, steroid metabolism, and central nervous system development. This review provides a comprehensive summary of currently known roles and discusses the importance of WWOX gene for CNS development and functioning.

WWOX--the FRA16D cancer gene: expression correlation with breast cancer progression and prognosis.

AIMS: WWOX is a tumour suppressor gene involved in various tumours including breast cancer. High chromosomal abnormalities in a genomic region spanned by WWOX are associated with the fact that this gene covers approximately 1 million base pairs of the second most affected among common chromosomal fragile sites FRA16D. We evaluated WWOX expression levels in breast cancer samples in association with diagnostics-prognostics markers. METHODS: We performed quantitative real-time RT-PCR to analyse levels of expression of WWOX in 132 cases of breast cancer. We evaluated the relationship between WWOX mRNA levels, clinico-pathological factors, expression of aberrant WWOXDelta6-8 mRNA and other cancer related genes. RESULTS: Expression of WWOX was higher in patients younger than 50 years old, in ER and PR positive tumours vs negative for those receptors and tumours without lymph node metastasis vs LN+. WWOX mRNA levels were also higher in tumours with higher apoptotic index (Bcl2/Bax ratio). Negative associations were found between WWOX expression and cytokeratins 5/6 and 17 (P<0.05). High level expression of WWOX was also associated with better disease free survival. Presence of WWOXDelta6-8 transcripts were accompanied with lower WWOX wild type mRNA level. CONCLUSIONS: Reduced WWOX expression commonly observed in various neoplasias in cases of breast cancer is associated with markers of bad prognosis. Our findings reveal additional evidence that WWOX may be involved in steroid (estrogens) metabolism and signaling pathways. WWOX can be considered as a new target for gene therapy development due to the association of high WWOX expression with improved disease free survival.

Cyclin E expression in breast cancer correlates with negative steroid receptor status, HER2 expression, tumor grade and proliferation.

The main objective of this retrospective study was to investigate relations between cyclin E and pathoclinical factors in patients with operable breast cancer. Expression of cyclin E was analyzed by immunohistochemistry in specimens of invasive ductal breast cancer tissue obtained from 189 women during radical mastectomy. Overall, 110 tumor samples were regarded to be cyclin E positive. Cyclin E expression was more often seen in tumors with: negative steroid receptor status (p<0.0001), higher proliferative index (p=0.0014), higher tumor grade (p=0.0017), and presence of HER2 (p=0.0171). With a median follow-up of 58 months, expression of cyclin E together with negative steroid receptor status determined poor prognosis with a 5-year cancer-specific survival rate of 58%. It differed significantly from a survival curve of cyclin E negative and steroid receptor positive patients (87%, p=0.0005). No significant difference was observed in comparison with survival of cyclin E positive and steroid receptor positive patients (68%, p=0.221). We demonstrated that cyclin E expression in breast cancer cells was associated with negative steroid receptor status, HER2 presence, higher tumor grade and higher proliferation index. Expression of cyclin E together with lack of steroid receptors determined poor prognosis.

WWOX, a novel WW domain-containing protein mapping to human chromosome 16q23.3-24.1, a region frequently affected in breast cancer.

Studies were conducted with the final goal of identifying genes of interest mapping to the chromosome region 16q23.3-24.1, an area commonly affected by allelic losses in breast cancer. To this end we generated a detailed physical map of the genomic region spanning between sequence-tagged site markers D16S518 and D16S516. To identify candidate genes, we used shotgun genomic sequencing as well as isolation and analysis of transcripts mapping to the area of interest. We identified and cloned a novel gene, the genomic structure of which spans the whole region of interest. We named this gene WWOX because it contains two WW domains coupled to a region with high homology to the short-chain dehydrogenase/reductase family of enzymes. The ORF of WWOX is 1245 bp long, encoding a 414-amino acid protein. This gene is composed of nine exons. We performed a mutation screening of WWOX exons in a panel of breast cancer lines, most of which are hemizygous for the 16q genomic region indicated. We found no evidence of mutations, thus indicating that WWOX is probably not a tumor suppressor gene. However, we observed that one case of homozygous deletion as well as two previously described translocation breakpoints map to intronic regions of this gene. We speculate that WWOX may span the yet uncharacterized common fragile site FRA16D region. In expression studies we found overexpression of WWOX in breast cancer cell lines when compared with normal breast cells and tissues. The highest normal expression of WWOX was observed in hormonally regulated tissues such as testis, ovary, and prostate. This expression pattern and the presence of a short-chain dehydrogenase/reductase domain and specific amino acid features suggest a role for WWOX in steroid metabolism. Interestingly, the presence of WW domains in the structure of WWOX indicate the likelihood that this protein physically interacts with other proteins. The unique features of WWOX and its possible association with cancer processes make it an interesting target for further investigation.

WWOX, the FRA16D gene, behaves as a suppressor of tumor growth.

We recently reported the cloning of WWOX, a gene that maps to the common fragile site FRA16D region in chromosome 16q23.3-24.1. It was observed that the genomic area spanned by WWOX is affected by chromosomal translocations and homozygous deletions. Furthermore, the high incidence of allelic loss in breast, ovarian, prostate, and other cancers affecting this region suggests that WWOX is a candidate tumor suppressor gene. Expression of WWOX is highly variable in breast cancer cell lines, with some cases showing low or undetectable levels of expression. In this report, we demonstrate that ectopic WWOX expression strongly inhibits anchorage-independent growth in soft agar of breast cancer cell lines MDA-MB-435 and T47D. Additionally, we observed that WWOX induces a dramatic inhibition of tumorigenicity of MDA-MB-435 breast cancer cells when tested in vivo. We also detected the common occurrence of aberrant WWOX transcripts with deletions of exons 5-8 or 6-8 in various carcinoma cell lines, multiple myeloma cell lines, and primary breast tumors. These aberrant mRNA forms were not detected in normal tissues. Interestingly, we further observed that proteins encoded by such aberrant transcripts display an abnormal nuclear localization in contrast to the wild-type WWOX protein that localizes to the Golgi system. Our data indicate that WWOX behaves as a potent suppressor of tumor growth and suggest that abnormalities affecting this gene at the genomic and transcriptional level may be of relevance in carcinogenesis.

Effects of estrogen on global gene expression: identification of novel targets of estrogen action.

The important role played by the sex hormone estrogen in disease and physiological processes has been well documented. However, the mechanisms by which this hormone elicits many of its normal as well as pathological effects are unclear. To identify both known and unknown genes that are regulated by or associated with estrogen action, we performed serial analysis of gene expression on estrogen-responsive breast cancer cells after exposure to this hormone. We examined approximately 190,000 mRNA transcripts and monitored the expression behavior of 12,550 genes. Expression levels for the vast majority of those transcripts were observed to remain constant upon 17beta estradiol (E2) treatment. Only approximately 0.4% of the genes showed an increase in expression of > or =3-fold by 3 h post-E2 treatment. We cloned five novel genes (E2IG1-5), which were observed up-regulated by the hormonal treatment. Of these the most highly induced transcript, E2IG1, appears to be a novel member of the family of small heat shock proteins. The E2IG4 gene is a new member of the large family of leucine-rich repeat-containing proteins. On the basis of architectural and domain homology, this gene appears to be a good candidate for secretion in the extracellular environment and, therefore, may play a role in breast tissue remodeling and/or epithelium-stroma interactions. Several interesting genes with a potential role in the regulation of cell cycle progression were also identified to increase in expression, including Pescadillo and chaperonin CCT2. Two putative paracrine/autocrine factors of potential importance in the regulation of the growth of breast cancer cells were identified to be highly up-regulated by E2: stanniocalcin 2, a calcium/phosphate homeostatic hormone; and inhibin-beta B, a TGF-beta-like factor. Interestingly, we also determined that E2IG1 and stanniocalcin 2 were exclusively overexpressed in estrogen-receptor-positive breast cancer lines, and thus they have the potential to serve as breast cancer biomarkers. This data provides a comprehensive view of the changes induced by E2 on the transcriptional program of human E2-responsive cells, and it also identifies novel and previously unsuspected gene targets whose expression is affected by this hormone.

The influence of the WWOX gene on the regulation of biological processes during endometrial carcinogenesis.

The purpose of the present study was to investigate the role of WW domain containing oxidoreductase (WWOX) downregulation in biological cancer-related processes in normal (non-malignant) and cancer endometrial cell lines. We created an in vitro model using the normal endometrial cell line, THESC, and 2 endometrial cancer cell lines with varying degrees of differentiation, the Ishikawa (well-differentiated) and the MFE296 (moderately differentiated) cells, in which the WWOX tumor suppressor gene was silenced using Gipz lentiviral shRNA. In this model, we examined the changes in invasiveness via biological assays, such as zymography, migration through a basement membrane, the adhesion of cells to extracellular matrix proteins, anchorage-independent growth and colony formation assay. We also evaluated the correlation between the mRNA expression of the WWOX gene and genes involved in the processes of carcinogenesis, namely catenin beta-1 (CTNNB1) and zinc finger E-box binding homeobox 1 (ZEB1) (gene transcription), cadherin 1 (CDH1) and ezrin (EZR) (cell adhesion), vimentin (VIM) (structural proteins), as well as phosphatase and tensin homolog (PTEN) (tumor suppression) and secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) (SPARC) (cell growth regulation) by RT-qPCR. Downregulation of the WWOX gene in the moderately differentiated MFE296 cell line caused decreased migratory capacity, and a reduction of matrix metalloproteinase-2 (MMP-2) activity. However, these cells grew in semisolid medium and exhibited higher expression of CDH1 and EZR (cell adhesion) and secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) (cell growth regulation). Moreover, in the well-differentiated endometrial cancer (Ishikawa) cell line, WWOX gene silencing resulted in an increased ability of the cells to proliferate indefinitely. Additionally, WWOX regulated changes in adhesion potential in both the normal and cancer cell lines. Our results suggest that the WWOX tumor suppressor gene modulated the processes of cell motility, cell adhesion, gene expression and remodeling in endometrial cell lines.

Constitutive telomerase activity in cells with tissue-renewing potential from estrogen-regulated rat tissues.

To investigate the role of telomerase in estrogen-regulated rodent tissues, we assayed the activity levels of this enzyme and measured cell proliferation and indicators of cellularity in vagina, mammary gland, and uterus from virgin, pregnant, ovariectomized, and ovariectomized estradiol-treated rats. No association was observed between telomerase activity and increased cell proliferation. Telomerase activity was significantly higher (P=0.003) in vagina obtained from ovariectomized rats (very low proliferation) than in vagina from ovariectomized and estradiol-treated rats (high proliferation, high differentiation). The high telomerase levels observed in vagina from ovariectomized rats indicates that the same epithelial compartment (i.e., basal layer) that has the potential to reconstitute the epithelium also contains the cells that express telomerase. The lower telomerase activity in the keratinized (differentiated) vagina was probably due to dilution of the number of telomerase-producing cells by the terminally differentiated non-telomerase-producing cells. Similar results were observed in uterus from ovariectomized versus ovariectomized and estradiol-treated rats. Telomerase activity was highest in uterus from pregnant rats. Telomerase levels in samples from total mammary gland fat pads varied considerably between groups and appeared to be representative of the amount of epithelium present in the sample. Interestingly, when mammary gland samples from the same animals were obtained from pure epithelial organoid preparations, no differences in telomerase activity could be distinguished between animals or groups. Overall these data suggest that telomerase activity, particularly in rat vagina and uterus, appears to be associated with a cell subpopulation showing proliferative and tissue reconstitution potential and not directly associated with proliferation status per se.

Analysis of telomerase activity levels in breast cancer: positive detection at the in situ breast carcinoma stage.

Telomerase activity has been implicated to be associated with most human malignant tumors, including breast cancer. To evaluate possible associations with well-known prognostic factors in breast cancer, we performed a semi-quantitative analysis of telomerase activity levels using the very sensitive PCR-mediated telomeric repeat amplification protocol. Telomerase activity was detected in 99 of 104 breast cancer samples analyzed (95.2%), whereas no activity was detected in 10 of 10 adjacent nonmalignant breast tissues. Analysis of five breast fibroadenoma samples revealed telomerase activity in one (20%). In contrast to previous observations, we observed that 100% of stage I breast tumors were positive for telomerase activity. More interestingly, we detected telomerase activity in six of six ductal carcinoma in situ samples (i.e., stage 0). In our semiquantitative analysis of levels of enzymatic activity, we found no statistically significant correlation at the P < h 0.05 level between telomerase levels and lymph node metastasis status, estrogen and progesterone receptor status, tumor size, S-phase fraction, and ploidy. The only statistically significant correlation was found with patient age (rho = -0.3; P = 0.03). We observed no statistically significant difference in the telomerase activity levels of early tumors (stages 0 and 1) versus more advanced lesions (stages II to IV). Nevertheless, stage IV tumors displayed a tendency for higher telomerase activity levels. In summary, no clear association was observed between telomerase levels and known breast cancer prognostic indicators. However, telomerase detection by the telomeric repeat amplification protocol method, due to its high sensitivity, may be of value in early breast cancer diagnosis and detection, because our data indicate that telomerase reactivation appears to constitute a relatively early event in breast carcinogenesis.

WWOX, the common chromosomal fragile site, FRA16D, cancer gene.

Gross chromosomal rearrangements and aneuploidy are among the most common somatic genomic abnormalities that occur during cancer initiation and progression, in particular in human solid tumor carcinogenesis. The loss of large chromosomal regions as consequence of gross rearrangements (e.g. deletions, monosomies, unbalanced translocations and mitotic recombination) have been traditionally associated with the existence of tumor suppressor genes within the areas affected by the loss of genetic material. The long arm of chromosome 16 was identified as being frequently associated with structural abnormalities in multiple neoplasias, that led us to focus attention on the detailed genetic dissection of this region resulting in the cloning of the putative tumor suppressor gene, WWOX (WW domain containing Oxidoreductase). Interestingly, the WWOX gene resides in the very same region as that of the common chromosomal fragile site 16D (FRA16D). The WWOX gene encodes a protein that contains two WW domains, involved in protein-protein interactions, and a short chain dehydrogenase (SDR) domain, possibly involved in sex-steroid metabolism. We have identified the WWOX WW domain ligand as the PPXY motif confirming the biochemical activity of this domain. WWOX normally resides in the Golgi and we will demonstrate that Golgi localization requires an intact SDR. Inactivation of the WWOX gene during tumorigenesis can occur by homozygous deletions and possibly mutation, however, aberrantly spliced forms of WWOX mRNA have been observed even when one allele is still intact. The aberrantly spliced mRNAs have deletions of the exons that encode the SDR and these WWOX protein isoforms display abnormal intracellular localization to the nucleus possibly functioning as dominant negative inhibitors of full length WWOX. Thus, generation of aberrant transcripts of WWOX may represent a novel mechanism to functionally inactivate WWOX without genomic alteration of the remaining allele. In this article we will review the cloning and identification of WWOX as the target of FRA16D. In addition, we will discuss the possible biochemical functions of WWOX and present evidence that ectopic WWOX expression inhibits tumor growth.

WWOX, the tumour suppressor gene affected in multiple cancers.

WWOX is a tumour suppressor gene affected in multiple cancers, especially in breast, prostate and ovary. This gene is located at the chromosomal area 16q23.3-24.1, which was identified as a common chromosomal fragile site FRA16D. WWOX turned out to possess tumour suppressor features despite the fact that the most basic (classical) way of tumour suppressor gene inactivation involves both alleles (e.g. through deletions, point mutations and promoter methylation), which is very rare event in a case of WWOX, occurring only in few cell lines. A large number of papers corroborate the phenomenon of correlation between the loss of WWOX expression and more aggressive/worse prognosis in many different types of tumours, for example breast cancer, nonsmall cell lung cancer, bladder cancer, gastric cancer or sporadic meningiomas. Ectopically increased WWOX expression promotes migration through basal membrane, however suppresses anchorage independent growth and induces normal-like colony formation in matrigel.

Evaluation of oestrogen receptor expression in breast cancer by quantification of mRNA.

AIMS: cDNA microarrays have subclassified breast carcinomas into molecular subtypes with oestrogen receptor-alpha (ER) gene expression as a main marker. The aim was to compare ER expression in 97 patients with operable breast cancer estimated by real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR) and by routine immunohistochemistry, and to determine which method was reliable for molecular subtyping in relation to basal-type keratins and HER2 gene expression. METHODS AND RESULTS: Frozen tumour samples were analysed by real-time RT-PCR for the expression of ER, HER2, keratin 5 and keratin 17 genes. In a group of 27 tumours with a low level of ER mRNA (<1.00), there were eight ER+ cases as assessed by immunohistochemistry, and of 70 cases with a high level of ER mRNA (>or=1.00), 26 were ER- by immunohistochemistry (P = 0.003). Lack of prognostic relevance of ER mRNA level was demonstrated, whereas assessment by immunohistochemistry was related to clinical outcome. Expression of basal keratins and HER2 genes differed significantly between ER+ and ER- tumours based on immunohistochemistry, but not on mRNA level. CONCLUSIONS: These results throw doubt on the assessment of ER mRNA as a key factor in the molecular distinction between breast tumours.

Telomerase and cell proliferation in mouse skin papillomas.

The progression of chemically induced mouse skin papillomas is paralleled by an increase in telomerase activity. In this study, we compared telomerase activity and rate of cell proliferation in papillomas obtained early versus late in papilloma progression. Eighteen early papillomas (after 15 wk of promotion) showed no evidence of telomerase activity, and their average cell proliferation index was 26.6% +/- 6.3. On the other hand, most of the papillomas harvested after 25 wk of promotion showed high levels of telomerase activity, but their average cell proliferation index (30.8% +/- 6.2) was not different from that of the early lesions. We concluded that there appears to be no association between the level of telomerase activity observed in mouse skin papillomas and the rate of cell proliferation of each individual tumor. Telomerase expression may indicate the existence of more abundant tumor subpopulations in advanced papillomas with proliferative potential for autonomous growth.