Hyunsuk Kil

WWOX binds the specific proline-rich ligand PPXY: identification of candidate interacting proteins

WWOX, the gene that maps to common chromosomal fragile site FRA16D, is frequently affected by aberrations in multiple types of cancers. WWOX encodes a 46 kDa protein that contains two WW domains and a short-chain oxidoreductase (SDR) domain. We recently demonstrated that ectopic expression of WWOX inhibits xenograft tumor growth of tumorigenic breast cancer cells. Little is known of the biochemical function(s) of WWOX. The SDR domain is predicted to be involved in sex-steroid metabolism and the WW domains are likely involved in protein–protein interactions. In this report, we identify the specific proline-rich ligand for WWOX as PPXY and show that the amino-terminal WW domain is responsible for this interaction. Using the WWOX WW domains as a probe, we screened high-density protein arrays and identified five candidate-binding partners. The binding to one of these candidates, small membrane protein of the lysosome/late endosome (SIMPLE), was further analysed, and we observed that a specific PPSY motif in the SIMPLE amino-acid sequence was required to interact with the amino-terminal WW domain of WWOX. In addition, immunofluorescence staining demonstrated that endogenous WWOX and SIMPLE co-localize to perinuclear compartments of MCF-7 human breast cancer cells. These studies demonstrate that WWOX contains a Group I WW domain that binds known cellular proteins containing the specific ligand PPXY. Identification and characterization of WWOX interacting proteins will lead to an understanding of the biological functions of WWOX in normal and tumor cells.

Frequent loss of WWOX expression in breast cancer: correlation with estrogen receptor status.

WWOX is a cancer gene, spanning the common chromosomal fragile site 16D. Genomic and expression aberrations affecting this gene and locus are common in various neoplasias including breast cancer. The aim of the present study was to evaluate the relationship between WWOX expression at the protein level with respect to clinico-pathological characteristics. We performed immunohistochemical analyses on breast specific tissue microarrays representing, human normal breast epithelium (n=16), ductal carcinoma in situ (n=15) and invasive breast cancer cases (n=203). Staining intensity measurements were objectively determined utilizing an image analysis system. Western blot analyses were also performed on an independent set of 23 invasive breast carcinomas. All normal breast epithelial samples express WWOX protein abundantly while 34% (69/203 cases) of invasive breast carcinomas were ‘completely negative’ for WWOX expression and an additional 26% (52/203) of cases expressed WWOX very weakly. For DCIS samples five out of 15 (33%) were negative or weak for WWOX staining. Interestingly, we found a statistically significant correlation between WWOX expression and estrogen receptor (ER) status, 27% of ER+ breast carcinomas were completely negative for WWOX expression versus 46% for ER−cases (p = 0.0054). Furthermore, when negative plus weakly WWOX stained cases were considered the difference became more significant with 51% of ER+ cases and 73% for the ER − group, with a p = 0.003. These data indicate that loss of WWOX expression is a common event in breast cancer. It is unclear at this point whether loss of WWOX expression is a consequence of tumor progression or represents a subclass of breast carcinomas. The strong association of WWOX expression with ER status reinforces the suggested role of this protein as an enzyme involved in sex steroid metabolism.

WWOX hypomorphic mice display a higher incidence of B-cell lymphomas and develop testicular atrophy

WWOX is a putative tumor suppressor gene encoded within common chromosomal fragile site region FRA16D, in chromosome band 16q23. Multiple studies have demonstrated that WWOX expression is often reduced or lost in various tumor types. WWOX tumor suppressor activity was suggested by re‐expressing WWOX in breast, ovarian, and lung tumor cell lines leading to tumor growth inhibition in vivo. To determine whether loss of Wwox gene expression has a role in tumorigenesis, we generated a mouse strain containing a Wwox gene mutated by a gene‐trap vector. Homozygous Wwox gene‐trap mice (Wwoxgt/gt) had no detectable Wwox protein in most tissues examined, although, a low level could be detected in a minority of tissues. Because of these observations, we concluded that these mice are Wwox hypomorphs. Remarkably, Wwox hypomorphic mice are viable in contrast to the recently reported postnatal lethality of Wwox knockout mice. Testes from Wwoxgt/gt males had high numbers of atrophic seminiferous tubules and reduced fertility when compared with wild‐type counterparts. We observed that the Wwoxgt/gt mice had a significantly shorter lifespan, and female hypomorphs had a higher incidence of spontaneous B‐cell lymphomas. In conclusion, we describe a novel Wwox hypomorphic mouse model that overcomes postnatal lethality that was recently observed in Wwox knockout mice. Therefore, tumorigenesis studies using this model more closely recapitulates the loss of WWOX expression observed in human cancers. Importantly, our observation that Wwox hypomorphs had an increased incidence of B‐cell lymphomas supports a role of Wwox as a tumor suppressor.

Generation and characterization of mice carrying a conditional allele of the Wwox tumor suppressor gene

WWOX, the gene that spans the second most common human chromosomal fragile site, FRA16D, is inactivated in multiple human cancers and behaves as a suppressor of tumor growth. Since we are interested in understanding WWOX function in both normal and cancer tissues we generated mice harboring a conditional Wwox allele by flanking Exon 1 of the Wwox gene with LoxP sites. Wwox knockout (KO) mice were developed by breeding with transgenic mice carrying the Cre-recombinase gene under the control of the adenovirus EIIA promoter. We found that Wwox KO mice suffered from severe metabolic defect(s) resulting in growth retardation and all mice died by 3 wk of age. All Wwox KO mice displayed significant hypocapnia suggesting a state of metabolic acidosis. This finding and the known high expression of Wwox in kidney tubules suggest a role for Wwox in acid/base balance. Importantly, Wwox KO mice displayed histopathological and hematological signs of impaired hematopoeisis, leukopenia, and splenic atrophy. Impaired hematopoeisis can also be a contributing factor to metabolic acidosis and death. Hypoglycemia and hypocalcemia was also observed affecting the KO mice. In addition, bone metabolic defects were evident in Wwox KO mice. Bones were smaller and thinner having reduced bone volume as a consequence of a defect in mineralization. No evidence of spontaneous neoplasia was observed in Wwox KO mice. We have generated a new mouse model to inactivate the Wwox tumor suppressor gene conditionally. This will greatly facilitate the functional analysis of Wwox in adult mice and will allow investigating neoplastic transformation in specific target tissues.

SAGE profiling of UV-induced mouse skin squamous cell carcinomas, comparison with acute UV irradiation effects

Ultraviolet (UV) irradiation is the primary environmental insult responsible for the development of most common skin cancers. To better understand the multiple molecular events that contribute to the development of UV‐induced skin cancer, in a first study, serial analysis of gene expression (SAGE) was used to compare the global gene expression profiles of normal SKH‐1 mice epidermis with that of UV‐induced squamous cell carcinomas (SCCs) from SKH‐1 mice. More than 200 genes were found to be differentially expressed in SCCs compared to normal skin (P < 0.0005 level of significance). As expected, genes related to epidermal proliferation and differentiation were deregulated in SCCs relative to normal skin. However, various novel genes, not previously associated with skin carcinogenesis, were also identified as deregulated in SCCs. Northern blot analyses on various selected genes validated the SAGE findings: caspase‐14 (reduced 8.5‐fold in SCCs); cathepsins D and S (reduced 3‐fold and increased 11.3‐fold, respectively, in SCCs); decorin, glutathione S‐transferase omega‐1, hypoxia‐inducible factor 1α, insulin‐like growth factor binding protein‐7, and matrix metalloproteinase‐13 (increased 18‐, 12‐, 12‐, 18.3‐, and 11‐folds, respectively, in SCCs). Chemokine (C‐C motif), ligand 27 (CCL27), which was found downregulated 12.7‐fold in SCCs by SAGE, was also observed to be strongly downregulated 6–24 h after a single and multiple UV treatments. In a second independent study we compared the expression profile of UV‐irradiated versus sham‐treated SKH‐1 epidermis. Interestingly, numerous genes determined to be deregulated 8 h after a single UV dose were also deregulated in SCCs. For instance, genes whose expression was upregulated both after acute UV‐treated skin and SCCs included keratins 6 and 16, small proline‐rich proteins, and S100 calcium binding protein A9. Studies like those described here do not only provide insights into genes and pathways involved in skin carcinogenesis but also allow us to identify early UV irradiation deregulated surrogate biomarkers of potential use in chemoprevention studies.

Conditional Wwox Deletion in Mouse Mammary Gland by Means of Two Cre Recombinase Approaches

Loss of WWOX expression has been reported in many different cancers including breast cancer. Elucidating the function of this gene in adult tissues has not been possible with full Wwox knockout models. Here we characterize the first conditional models of Wwox ablation in mouse mammary epithelium utilizing two transgenic lines expressing Cre recombinase, keratin 5-Cre (BK5-Cre) and MMTV-Cre. In the BK5-Cre model we observed very efficient Wwox ablation in KO mammary glands. However, BK5-Cre Wwox KO animals die prematurely for unknown reasons. In the MMTV-Cre model we observed significant ablation of Wwox in mammary epithelium with no effect on survival. In both of these models we found that Wwox deletion resulted in impaired mammary branching morphogenesis. We demonstrate that loss of Wwox is not carcinogenic in our KO models. Furthermore, no evidence of increase proliferation or development of premalignant lesions was observed. In none of the models did loss of a single Wwox allele (i.e. haploinsufficiency) have any observable phenotypic effect in mammary gland. To better understand the function of Wwox in the mammary gland, transcriptome profiling was performed. We observed that Wwox ablation results in the deregulation of genes involved in various cellular processes. We found that expression of the non-canonical Wnt ligand, Wnt5a, was significantly upregulated in Wwox KO mammary epithelium. Interestingly, we also determined that components of the Jak/Stat3 signaling pathway were upregulated in KO mice and this correlated with a very robust increase in phospho-Stat3 signaling, which warrants further testing. Even though the loss of Wwox expression in breast and other cancers is very well documented, our findings suggest that Wwox does not act as a classical tumor suppressor as previously thought.

The WWOX Gene Modulates High-Density Lipoprotein and Lipid Metabolism

Background—Low levels of high-density lipoprotein (HDL) cholesterol constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase (WWOX) gene and HDL cholesterol levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results—Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in 2 multigenerational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep−/− and total Wwox−/− mice models, where we found decreased ApoA-I and Abca1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox−/−, but not Wwoxhep−/− littermates, also showed marked reductions in serum HDL cholesterol concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a sex-specific effect in female Wwoxhep−/− mice, where microarray analyses revealed an increase in plasma triglycerides and altered lipid metabolic pathways. We further identified a significant reduction in ApoA-I and Lpl and an upregulation in Fas, Angptl4, and Lipg, suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions—Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.Background —Low high-density lipoprotein-cholesterol (HDL-C) constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase ( WWOX ) gene and HDL-C levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results —Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in two multi-generational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep-/- and total Wwox-/- mice models, where we found decreased ApoA-I and ABCA1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox-/- , but not Wwoxhep-/- littermates, also showed marked reductions in serum HDL-C concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a gender-specific effect in female Wwoxhep-/- mice, where an increase in plasma triglycerides and altered lipid metabolic pathways by microarray analyses were observed. We further identified a significant reduction in ApoA-I and LPL , and upregulation in Fas , Angptl4 and Lipg , suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions —Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.

The WWOX Gene Modulates HDL and Lipid Metabolism

Background—Low levels of high-density lipoprotein (HDL) cholesterol constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase (WWOX) gene and HDL cholesterol levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results—Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in 2 multigenerational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep−/− and total Wwox−/− mice models, where we found decreased ApoA-I and Abca1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox−/−, but not Wwoxhep−/− littermates, also showed marked reductions in serum HDL cholesterol concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a sex-specific effect in female Wwoxhep−/− mice, where microarray analyses revealed an increase in plasma triglycerides and altered lipid metabolic pathways. We further identified a significant reduction in ApoA-I and Lpl and an upregulation in Fas, Angptl4, and Lipg, suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions—Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.Background —Low high-density lipoprotein-cholesterol (HDL-C) constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase ( WWOX ) gene and HDL-C levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results —Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in two multi-generational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep-/- and total Wwox-/- mice models, where we found decreased ApoA-I and ABCA1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox-/- , but not Wwoxhep-/- littermates, also showed marked reductions in serum HDL-C concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a gender-specific effect in female Wwoxhep-/- mice, where an increase in plasma triglycerides and altered lipid metabolic pathways by microarray analyses were observed. We further identified a significant reduction in ApoA-I and LPL , and upregulation in Fas , Angptl4 and Lipg , suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions —Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.

DMBA induced mouse mammary tumors display high incidence of activating Pik3caH1047 and loss of function Pten mutations

Controversy always existed on the utility of chemically induced mouse mammary carcinogenesis models as valid equivalents for the study of human breast cancer. Here, we performed whole exome and RNA sequencing on long latency mammary tumors (218 ± 27 days) induced by the carcinogen 7,12-Dimethylbenzathracene (DMBA) and short latency tumors (65 ± 11 days) induced by the progestin Medroxyprogesterone Acetate (MPA) plus DMBA in CD2F1 mice. Long latency tumors displayed a high frequency of Pi3kca and/or Pten mutations detected in 11 of 13 (85%) long latency cases (14/22, 64% overall). Eighty-two percent (9/11) of tumors carried the Pik3ca H1047L/R hot-spot mutation, as frequently found in human breast cancer. These tumors were luminal-like and mostly ER/PR+, as in humans. Transcriptome profiling indicated a significant activation of the PI3K-Akt pathway (p=3.82e-6). On the other hand MPA+DMBA induced short latency tumors displayed mutations in cancer drivers not commonly found mutated in human breast cancer (e.g. Hras and Apc). These tumors were mostly basal-like and MPA exposure led to Rankl overexpression (60 fold induction) and immunosuppressive gene expression signatures. In summary, long latency DMBA induced mouse mammary tumors reproduce the molecular profile of human luminal breast carcinomas representing an excellent preclinical model for the testing of PIK3CA/Akt/mTOR pathway inhibitory therapies and a good platform for the developing of additional preclinical tools such as syngeneic transplants in immunocompetent hosts.

The WWOX Gene Modulates High-Density Lipoprotein and Lipid MetabolismClinical Perspective

Background—Low levels of high-density lipoprotein (HDL) cholesterol constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase (WWOX) gene and HDL cholesterol levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results—Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in 2 multigenerational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep−/− and total Wwox−/− mice models, where we found decreased ApoA-I and Abca1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox−/−, but not Wwoxhep−/− littermates, also showed marked reductions in serum HDL cholesterol concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a sex-specific effect in female Wwoxhep−/− mice, where microarray analyses revealed an increase in plasma triglycerides and altered lipid metabolic pathways. We further identified a significant reduction in ApoA-I and Lpl and an upregulation in Fas, Angptl4, and Lipg, suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions—Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.Background —Low high-density lipoprotein-cholesterol (HDL-C) constitutes a major risk factor for atherosclerosis. Recent studies from our group reported a genetic association between the WW domain-containing oxidoreductase ( WWOX ) gene and HDL-C levels. Here, through next-generation resequencing, in vivo functional studies and gene microarray analyses, we investigated the role of WWOX in HDL and lipid metabolism. Methods and Results —Using next-generation resequencing of the WWOX region, we first identified 8 variants significantly associated and perfectly segregating with the low-HDL trait in two multi-generational French Canadian dyslipidemic families. To understand in vivo functions of WWOX, we used liver-specific Wwoxhep-/- and total Wwox-/- mice models, where we found decreased ApoA-I and ABCA1 levels in hepatic tissues. Analyses of lipoprotein profiles in Wwox-/- , but not Wwoxhep-/- littermates, also showed marked reductions in serum HDL-C concentrations, concordant with the low-HDL findings observed in families. We next obtained evidence of a gender-specific effect in female Wwoxhep-/- mice, where an increase in plasma triglycerides and altered lipid metabolic pathways by microarray analyses were observed. We further identified a significant reduction in ApoA-I and LPL , and upregulation in Fas , Angptl4 and Lipg , suggesting that the effects of Wwox involve multiple pathways, including cholesterol homeostasis, ApoA-I/ABCA1 pathway, and fatty acid biosynthesis/triglyceride metabolism. Conclusions —Our data indicate that WWOX disruption alters HDL and lipoprotein metabolism through several mechanisms and may account for the low-HDL phenotype observed in families expressing the WWOX variants. These findings thus describe a novel gene involved in cellular lipid homeostasis, which effects may impact atherosclerotic disease development.