Disabled Homolog 2 Research Articles

Toxoplasma gondii infection induces cell apoptosis via multiple pathways revealed by transcriptome analysis

Toxoplasma gondii is a worldwide parasite that can infect almost all kinds of mammals and cause fatal toxoplasmosis in immunocompromised patients. Apoptosis is one of the principal strategies of host cells to clear pathogens and maintain organismal homeostasis, but the mechanism of cell apoptosis induced by T. gondii remains obscure. To explore the apoptosis influenced by T. gondii, Vero cells infected or uninfected with the parasite were subjected to apoptosis detection and subsequent dual RNA sequencing (RNA-seq). Using high-throughput Illumina sequencing and bioinformatics analysis, we found that pro-apoptosis genes such as DNA damage-inducible transcript 3 (DDIT3), growth arrest and DNA damage-inducible α (GADD45A), caspase-3 (CASP3), and high-temperature requirement protease A2 (HtrA2) were upregulated, and anti-apoptosis genes such as poly(adenosine diphosphate (ADP)-ribose) polymerase family member 3 (PARP3), B-cell lymphoma 2 (Bcl-2), and baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5) were downregulated. Besides, tumor necrosis factor (TNF) receptor-associated factor 1 (TRAF1), TRAF2, TNF receptor superfamily member 10b (TNFRSF10b), disabled homolog 2 (DAB2)‍-interacting protein (DAB2IP), and inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) were enriched in the upstream of TNF, TNF-related apoptosis-inducing ligand (TRAIL), and endoplasmic reticulum (ER) stress pathways, and TRAIL-receptor 2 (TRAIL-R2) was regarded as an important membrane receptor influenced by T. gondii that had not been previously considered. In conclusion, the T. gondii RH strain could promote and mediate apoptosis through multiple pathways mentioned above in Vero cells. Our findings improve the understanding of the T. gondii infection process through providing new insights into the related cellular apoptosis mechanisms.

RETRACTED: Baicalin exerts anti-tumor effects in oral squamous cell carcinoma by inhibiting the microRNA-106b-5p-Wnt/β-catenin pathway via upregulating disabled homolog 2

The aim of this study was to investigate the role and molecular regulatory mechanisms of baicalin in oral squamous cell carcinoma (OSCC) progression. Gene expression in OSCC cells was detected by quantitative reverse transcription polymerase chain reaction (RT-qPCR). OSCC cell viability, migration, invasion and stemness were measured by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-ethynyl-2'-deoxyuridine (EdU), wound healing, Transwell, and sphere formation assays. The target genes of miR-106b-5p were predicted using bioinformatic tools. The interaction between microRNA-miR-106b-5p (miR-106b-5p) and disabled homolog 2 (DAB2) was confirmed by a luciferase reporter assay. TOP/FOP-Flash reporter assay and western blot analysis were used to analyze the activity of the Wnt/β-catenin pathway. Baicalin inhibited OSCC cell viability, migration, invasion, and stemness. Baicalin downregulated miR-106b-5p expression. In addition, MiR-106b-5p upregulation reversed the effects of baicalin on OSCC cells. As a target gene of miR-106b-5p, DAB2 was negatively regulated by miR-106b-5p and upregulated by baicalin in OSCC cells. MiR-106b-5p activated Wnt/β-catenin pathway in OSCC cells by inhibiting DAB2. Baicalin suppressed Wnt/β-catenin pathway by upregulating DAB2. In rescue assays, miR-106b-5p overexpression-induced promotion of OSCC cellular processes was attenuated by DAB2 upregulation. Baicalin exerts anti-tumor effects in OSCC by inhibiting the miR-106b-5p-Wnt/β-catenin pathway via upregulating DAB2.

Short chain fatty acids delay the development of hepatocellular carcinoma in HBx transgenic mice

Chronic infection with hepatitis B virus (HBV) is a major risk factor for the development of hepatocellular carcinoma (HCC). The HBV encoded oncoprotein, HBx, alters the expression of host genes and the activity of multiple signal transduction pathways that contribute to the pathogenesis of HCC by multiple mechanisms independent of HBV replication. However, it is not clear which pathways are the most relevant therapeutic targets in hepatocarcinogenesis. Short chain fatty acids (SCFAs) have strong anti-inflammatory and anti-neoplastic properties, suggesting that they may block the progression of chronic liver disease (CLD) to HCC, thereby identifying the mechanisms relevant to HCC development. This hypothesis was tested in HBx transgenic (HBxTg) mice fed SCFAs. Groups of HBxTg mice were fed with SCFAs or vehicle from 6 to 9 months of age and then assessed for dysplasia, and from 9 to 12 months of age and then assessed for HCC. Livers from 12 month old mice were then analyzed for changes in gene expression by mass spectrometry-based proteomics. SCFA-fed mice had significantly fewer dysplastic and HCC nodules compared to controls at 9 and 12 months, respectively. Pathway analysis of SCFA-fed mice showed down-regulation of signaling pathways altered by HBx in human CLD and HCC, including those involved in inflammation, phosphatidylinositol 3-kinase, epidermal growth factor, and Ras. SCFA treatment promoted increased expression of the tumor suppressor, disabled homolog 2 (DAB2). DAB2 depresses Ras pathway activity, which is constitutively activated by HBx. SCFAs also reduced cell viability in HBx-transfected cell lines in a dose-dependent manner while the viability of primary human hepatocytes was unaffected. These unique findings demonstrate that SCFAs delay the pathogenesis of CLD and development of HCC, and provide insight into some of the underlying mechanisms that are relevant to pathogenesis in that they are responsive to treatment.

009 Hyperthermia controls DAB2 transcription in macrophage through inducing the separation of cJun and cFos heterodimers

Sporotrichosis is an emergent subcutaneous mycosis of humans and some animals caused by dimorphic fungi of the Sporothrix schenckii. Hyperthermia can effectively treat sporotrichosis by regulating the phenotypic regulation of macrophages which is critical for controlling tissue inflammation and resolution. The adaptor protein disabled homolog 2 (DAB2), a regulator of phenotypic polarization in macrophages, have been identified to inhibit an inflammatory phenotype of the macrophages. However, whether and how hyperthermia act on the immune regulation of macrophages through DAB2 needs more research and complement. In this study, mouse bone marrow extracted primary macrophages (BMDMs) and cell line ANA-1 were used to investigate the regulation of DAB2 gene transcription by hyperthermia in vitro. Immunofluorescence was used to examine sub-localization of AP-1 complex within the cells under the 42°C conditions. Chromatin immunoprecipitation was used to detect whether 42°C stimulation affect the binding of AP-1complex to DAB2 gene. Conditional DAB2 knockout mice were used to evaluate the role of DAB2 in Sporotrichosis. Our results show that 42°C stimulation downregulated the expression of c-Jun and c-Fos, and led to the separation of c-Jun and c-Fos dimers, causing the downregulated transcription of DAB2. In conclusion, topical hyperthermia treatment can inhibit the transcription of DAB2 gene, promote macrophage M1 polarization, and promote the treatment of sporotrichosis via AP-1 complex.

Utility of SOX6 and DAB2 for the Diagnosis of Malignant Mesothelioma.

The separation of malignant mesothelioma from non-small cell lung carcinomas can be a difficult problem. Sex-determining region Y box 6 (SOX6) and disabled homolog 2 (DAB2) have recently been proposed as sensitive/specific markers of mesothelial lineage, but have not yet been independently tested for utility in mesothelioma diagnosis. Using tissue microarrays containing mesotheliomas (epithelioid: n=40, sarcomatoid: n=23) and non-small cell lung carcinomas (adenocarcinoma: n=52, squamous cell carcinoma: n=57, large cell carcinoma: n=12) we evaluated the performance of SOX6 and DAB2 by themselves, in conjunction with other established mesothelioma markers (calretinin, WT1, D2-40, CK5/6, HEG1) and combined with 3 broad-spectrum established carcinoma markers: claudin-4, MOC31, and BerEP4. For epithelioid mesothelioma, SOX6 and DAB2 had sensitivities of 85% and 98%, respectively. For sarcomatoid mesothelioma, SOX6 had a sensitivity of 13% and DAB2 could not be assessed due to background stromal staining. For SOX6 alone, specificity for mesothelioma versus adenocarcinoma, squamous cell carcinoma, and large cell carcinoma was 94%, 79%, and 92%, respectively, while for DAB2 specificity was 77%, 86%, and 67%. Combinations of SOX6 and established mesothelioma markers produced sensitivities of 95% or greater. A combination of SOX6 positive/claudin-4 negative staining was 95% to 100% specific for mesothelioma versus carcinoma with a sensitivity of 85%. SOX6 is a promising marker for the diagnosis of mesothelioma and potentially could be combined with other mesothelial markers or a broad-spectrum carcinoma marker to reach an accurate diagnosis with relatively few immunostains, The relatively low specificity and difficulty of interpreting DAB2 staining limits its utility for mesothelioma diagnosis.

In This Issue

In This Issue

Emerging Roles of Disabled Homolog 2 (DAB2) in Immune Regulation.

Disabled-2 (DAB2) is a clathrin and cargo binding endocytic adaptor protein recognized for its multifaceted roles in signaling pathways involved in cellular differentiation, proliferation, migration, tumor suppression, and other fundamental homeostatic cellular mechanisms. The requirement for DAB2 in the canonical TGFβ signaling in fibroblasts suggested that a similar mechanism may exist in immune cells and that DAB2 may contribute to immunological tolerance and suppression of inflammatory responses. In this review, we synthesize the current state of knowledge on the roles of DAB2 in the cells of the innate and adaptive immune system, with particular focus on antigen presenting cells (APCs; macrophages and dendritic cells) and regulatory T cells (Tregs). The emerging role of DAB2 in the immune system is that of an immunoregulatory molecule with significant roles in Treg-mediated immunosuppression, and suppression of TLR signaling in APC. DAB2 itself is downregulated by inflammatory stimuli, an event that likely contributes to the immunogenic function of APC. However, contrary findings have been described in neuroinflammatory disorders, thus suggesting a highly context-specific roles for DAB2 in immune cell regulation. There is need for better understanding of DAB2 regulation and its roles in different immune cells, their specialized sub-populations, and their responses under specific inflammatory conditions.

Disabled Homolog 2 (DAB2) Protein in Tumor Microenvironment Correlates with Aggressive Phenotype in Human Urothelial Carcinoma of the Bladder.

Disabled homolog-2 (DAB2) has been reported to be a tumor suppressor gene. However, a number of contrary studies suggested that DAB2 promotes tumor invasion in urothelial carcinoma of the bladder (UCB). Here, we investigated the clinical role and biological function of DAB2 in human UCB. Immunohistochemical staining analysis for DAB2 was carried out on UCB tissue specimens. DAB2 expression levels were compared with clinicopathological factors. DAB2 was knocked-down by small interfering RNA (siRNA) transfection, and then its effects on cell proliferation, invasion, and migration, and changes to epithelial-mesenchymal transition (EMT)-related proteins were evaluated. In our in vivo assays, tumor-bearing athymic nude mice subcutaneously inoculated with human UCB cells (MGH-U-3 or UM-UC-3) were treated by DAB2-targeting siRNA. Higher expression of DAB2 was associated with higher clinical T category, high tumor grade, and poor oncological outcome. The knock-down of DAB2 decreased both invasion and migration ability and expression of EMT-related proteins. Significant inhibitory effects on tumor growth and invasion were observed in xenograft tumors of UM-UC-3 treated by DAB2-targeting siRNA. Our findings suggested that DAB2 expression was associated with poor prognosis through increased oncogenic properties including tumor proliferation, migration, invasion, and enhancement of EMT in human UCB.

Epstein-Barr virus miR-BART1-3p suppresses apoptosis and promotes migration of gastric carcinoma cells by targeting DAB2.

Although Epstein-Barr virus (EBV) is known to encode over 40 different miRNAs of its own, the roles of most EBV miRNAs remain unknown. Disabled homolog 2 (DAB2) is a putative tumor suppressor, but its role in gastric carcinoma (GC), especially in EBV-associated GC, needs to be clarified. Our qRT-PCR and mRNA microarray results showed that DAB2 expression was down-regulated in EBV-positive GC cells compared to EBV-negative cells. Four BART miRNAs that might target DAB2 were predicted, and we found, using a luciferase reporter assay, that miR-BART1-3p directly targeted the 3'-UTR of DAB2. The miR-BART1-3p transfection decreased DAB2 expression at both mRNA and protein levels, while transfection of an inhibitor of miR-BART1-3p, miR-BART1-3p(i), increased DAB2 expression. In addition, miR-BART1-3p as well as siDAB2 increased migration and decreased apoptosis. Meanwhile, miR-BART1-3p(i) or pcDNA3.1-DAB2 transfection decreased migration and increased apoptosis in EBV-infected GC cells. Furthermore, decreased migration by miR-BART1-3p(i) was abrogated by co-transfected siDAB2, while decreased migration by miR-BART1-3p(i) was further suppressed by a co-transfected DAB2 over-expression vector. Our data suggest that miR-BART1-3p plays an important role in the tumorigenesis of EBV-associated GC by directly targeting DAB2.

Rapid Downregulation of DAB2 by Toll-Like Receptor Activation Contributes to a Pro-Inflammatory Switch in Activated Dendritic Cells.

Dendritic cells (DCs) are pivotal in regulating tolerogenic as well as immunogenic responses against microorganisms by directing both the innate and adaptive immune response. In health, phenotypically different DC subsets found in the gut mucosa are maintained in their tolerogenic state but switch to a pro-inflammatory phenotype during infection or chronic autoinflammatory conditions such as inflammatory bowel disease (IBD). The mechanisms that promote the switch among the mucosal DCs from a tolerogenic to an immunogenic, pro-inflammatory phenotype are incompletely understood. We hypothesized that disabled homolog 2 (DAB2), recently described as a negative regulator of DC immunogenicity during their development, is regulated during intestinal inflammation and modulates mucosal DC function. We show that DAB2 is highly expressed in colonic CD11b+CD103− DCs, a subset known for its capacity to induce inflammatory Th1/Th17 responses in the colon, and is downregulated predominantly in this DC subset during adoptive T cell transfer colitis. Administration of Dab2-deficient DCs (DC2.4Dab2−/− cells) modulated the course of DSS colitis in wild-type mice, enhanced mucosal expression of Tnfa, Il6, and Il17a, and promoted neutrophil recruitment. In bone-marrow derived dendritic cells (BMDC), DAB2 expression correlated with CD11b levels and DAB2 was rapidly and profoundly inhibited by TLR ligands in a TRIF- and MyD88-dependent manner. The negative modulation of DAB2 was biphasic, initiated with a quick drop in DAB2 protein, followed by a sustained reduction in Dab2 mRNA. DAB2 downregulation promoted a more functional and activated DC phenotype, reduced phagocytosis, and increased CD40 expression after TLR activation. Furthermore, Dab2 knockout in DCs inhibited autophagy and promoted apoptotic cell death. Collectively, our results highlight the immunoregulatory role for DAB2 in the intestinal dendritic cells and suggest that DAB2 downregulation after microbial exposure promotes their switch to an inflammatory phenotype.

MiR-93 functions as a tumor promoter in prostate cancer by targeting disabled homolog 2 (DAB2) and an antitumor polysaccharide from green tea (Camellia sinensis) on their expression

Our previous work has demonstrated that the role of miR-93 in prostate cancer (PC) progression. The aim of this study was to determine the downstream gene regulated by miR-93 and the molecular mechanisms underlying its roles in PC. Bioinformatics analysis and luciferase reporter assays predicted disabled homolog 2 (DAB2) as a direct target gene of miR-93. Real time quantitative polymerase chain reaction (qRT-PCR) and Western blot analysis revealed that DAB2 was tumor repressor in PC cells, and its mRNA expression was negatively correlated with miR-93 in PC tissues. Gain and loss of function experiments also indicated DAB2 overexpression significantly suppressed PC cells proliferation, invasion and migration, while knockdown of its expression came to the opposite effect. Furthermore, a rescue experiment indicated miR-93 directly regulated PC cell growth and migration, as well as AKT and ERK activation by targeting DAB2. Additionally, antitumor effect of a Green tea polysaccharide (GTP) on PC-3 cells could be achieved by increasing DAB2 protein expression and inactivating AKT and ERK1/2 signaling. Our study suggests that miR-93 promoted PC progression and metastasis by repressing DAB2 to activate Akt/ERK1/2 pathway, and elevation of DAB2 and inactivation of Akt/ERK1/2 might be a potential therapeutic target for PC by GTP.

MiR-106b targets DAB2 to promote hepatocellular carcinoma cell proliferation and metastasis.

MicroRNAs (miRNAs) have been proven to have important effects on the proliferation and metastasis of multiple cancers, including hepatocellular carcinoma (HCC). In the present study, our aim was to explore the biological function of miR-106b in HCC cell proliferation and metastasis. qPCR analysis showed that miR-106b was expressed at higher levels, while disabled homolog 2 (DAB2) was expressed at lower levels in HCC tissues and cells. Moreover, the aberrant miR-106b expression in HCC affected the cell proliferative and migratory ability by MTT and Transwell assay. DAB2 was identified as a specific target of miR-106b in HCC by luciferase reporter assay and regression analysis showed a negative correlation between DAB2 and miR-106b expression. In addition, DAB2 may attenuate the miR-106b promotion effect on HCC cell proliferation and migration. In short, miR-106b may promote HCC cell proliferation and migration by targeting DAB2.

Tu1853 - Downregulation of Disabled Homolog 2 (DAB2) Expression by Microbial Components in Dendritic Cells in Inflammatory Bowel Disease Contributes to Dendritic Cells Function and Intestinal Inflammation

Tu1853 - Downregulation of Disabled Homolog 2 (DAB2) Expression by Microbial Components in Dendritic Cells in Inflammatory Bowel Disease Contributes to Dendritic Cells Function and Intestinal Inflammation

Bovine lineage specification revealed by single-cell gene expression analysis from zygote to blastocyst.

Preimplantation embryos undergo zygotic genome activation and lineage specification resulting in three distinct cell types in the late blastocyst. The molecular mechanisms underlying this progress are largely unknown in bovines. Here, we sought to analyze an extensive set of regulators at the single-cell level to define the events involved in the development of the bovine blastocyst. Using a quantitative microfluidics approach in single cells, we analyzed mRNA levels of 96 genes known to function in early embryonic development and maintenance of stem cell pluripotency in parallel in 384 individual cells from bovine preimplantation embryos. The developmental transitions can be distinguished by distinctive gene expression profiles and we identified NOTCH1, expressed in early developmental stages, while T-box 3 (TBX3) and fibroblast growth factor receptor 4 (FGFR4), expressed in late developmental stages. Three lineages can be segregated in bovine expanded blastocysts based on the expression patterns of lineage-specific genes such as disabled homolog 2 (DAB2), caudal type homeobox 2 (CDX2), ATPase H+/K+ transporting non-gastric alpha2 subunit (ATP12A), keratin 8 (KRT8), and transcription factor AP-2 alpha (TFAP2A) for trophectoderm; GATA binding protein 6 (GATA6) and goosecoid homeobox (GSC) for primitive endoderm; and Nanog homeobox (NANOG), teratocarcinoma-derived growth factor 1 (TDGF1), and PR/SET domain 14 (PRDM14) for epiblast. Moreover, some lineage-specific genes were coexpressed in blastomeres from the morula. The commitment to trophectoderm and inner cell mass lineages in bovines occurs later than in the mouse, and KRT8 might be an earlier marker for bovine trophectoderm cells. We determined that TDGF1 and PRDM14 might play pivotal roles in the primitive endoderm and epiblast specification of bovine blastocysts. Our results shed light on early cell fate determination in bovine preimplantation embryos and offer theoretical support for deriving bovine embryonic stem cells.

Disabled homolog 2 controls macrophage phenotypic polarization and adipose tissue inflammation.

Acute and chronic tissue injury results in the generation of a myriad of environmental cues that macrophages respond to by changing their phenotype and function. This phenotypic regulation is critical for controlling tissue inflammation and resolution. Here, we have identified the adaptor protein disabled homolog 2 (DAB2) as a regulator of phenotypic switching in macrophages. Dab2 expression was upregulated in M2 macrophages and suppressed in M1 macrophages isolated from both mice and humans, and genetic deletion of Dab2 predisposed macrophages to adopt a proinflammatory M1 phenotype. In mice with myeloid cell-specific deletion of Dab2 (Dab2fl/fl Lysm-Cre), treatment with sublethal doses of LPS resulted in increased proinflammatory gene expression and macrophage activation. Moreover, chronic high-fat feeding exacerbated adipose tissue inflammation, M1 polarization of adipose tissue macrophages, and the development of insulin resistance in DAB2-deficient animals compared with controls. Mutational analyses revealed that DAB2 interacts with TNF receptor-associated factor 6 (TRAF6) and attenuates IκB kinase β-dependent (IKKβ-dependent) phosphorylation of Ser536 in the transactivation domain of NF-κB p65. Together, these findings reveal that DAB2 is critical for controlling inflammatory signaling during phenotypic polarization of macrophages and suggest that manipulation of DAB2 expression and function may hold therapeutic potential for the treatment of acute and chronic inflammatory disorders.

Disabled homolog 2 is required for migration and invasion of prostate cancer cells.

Disabled homolog 2 (DAB2) is frequently deleted or epigenetically silenced in many human cancer cells. Therefore, DAB2 has always been regarded as a tumor suppressor gene. However, the role of DAB2 in tumor progression and metastasis remains unclear. In this study, DAB2 expression was upregulated along with human prostate cancer (PCa) progression. DAB2 overexpression or knockdown effects in LNCaP and PC3 cell lines were verified to address the biological functions of DAB2 in PCa progression and metastasis. LNCaP and PC3 cell lines were generated from human PCa cells with low and high metastatic potentials, respectively. The results showed that DAB2 shRNA knockdown can inhibit the migratory and invasive abilities of PC3 cells, as well as the tumorigenicity, whereas DAB2 overexpression enhanced LNCaP cell migration and invasion. Further investigation showed that DAB2 regulated the cell migration associated genes in PC3 cells, and the differential DAB2 expression between LNCaP and PC3 cells was partly regulated by histone 4 acetylation. Therefore, DAB2 may play an important role in PCa progression and metastasis.

Effects of miR-145 on the migration and invasion of prostate cancer PC3 cells by targeting DAB2

It was reported that miR-145, which is significantly decreased in a variety of tumor cells, is associated with cell proliferation and metastasis. In this study, using bioinformatics analysis and in vitro assays, we identified DAB2 (Disabled homolog 2) as a downstream target gene of miR-145 during tumor metastasis process. DAB2 has been characterized as an important tumor suppressor, and is usually expressed at low levels in tumor cells. However, in this study, the relative high-level expression of DAB2 gene was observed in the highly invasive prostate cancer PC3 cells. Moreover, enforced expression of miR-145 could significantly down-regulate the expression level of DAB2 in PC3 cells, and inhibit the migration and invasion of PC3 cells. Notably, dysfunction of PC3 cells induced by miR-145 overexpression can be rescued by co-overexpression of DAB2. These results demonstrate that miR-145 regulates the migration and invasion of highly invasive prostate cancer cells through targeting DAB2 gene.

Altered expression of inflammation-associated genes in oviductal cells following follicular fluid exposure: Implications for ovarian carcinogenesis

Evidence indicates that high-grade serous ovarian carcinoma (HGSOC) may originate from lesions within the distal fallopian tube epithelium (FTE). Our previous studies indicate that fallopian tube epithelial cells from carriers of germline mutations in breast cancer susceptibility genes exhibit a pro-inflammatory gene expression signature during the luteal phase, suggesting that delayed resolution of postovulatory inflammatory signaling may contribute to predisposition to this ovarian cancer histotype. To determine whether exposure of tubal epithelial cells to periovulatory follicular fluid alters expression of inflammation-associated genes, we used an ex vivo culture system of bovine oviductal epithelial cells. Oviductal cells grown on collagen IV-coated transwell membranes assumed a cobblestone appearance and immunocytochemistry for FoxJ1 and Pax8 indicated that both ciliated and secretory epithelial cells were maintained in the cultures. Oviductal cells were exposed to human follicular fluid or culture medium for 24 h following which total cellular RNA was extracted at various time points. Expression of genes associated with inflammation was determined by quantitative real-time RT-PCR. Exposure to follicular fluid transiently increased the transcript levels of interleukin 8 (IL8) and cyclooxygenase 2 (PTGS2), and decreased the expression of mitochondrial superoxide dismutase (SOD2), glutathione peroxidase 3 (GPX3), disabled homolog 2 (DAB2), and glucocorticoid receptor (NR3C1). Tumor necrosis factor (TNF) and IL6 levels were also decreased while those of nicotinomide phosphoribosyltransferase (NAMPT) were unaffected. This study demonstrates that periovulatory follicular fluid can act directly upon oviductal epithelial cells to alter gene expression that might contribute to early carcinogenic events. Furthermore, these findings illustrate the potential use of bovine oviductal cells to study signaling events implicated in ovarian carcinogenesis.

MiR-93-directed downregulation of DAB2 defines a novel oncogenic pathway in lung cancer

The disabled homolog 2 (DAB2) gene was recently identified as a tumor suppressor gene with its expression down-regulated in multiple cancer types. The role of DAB2 in lung tumorigenesis, however, is not fully characterized, and the mechanisms of DAB2 dysregulation in lung cancer are not defined. Here we show that low DAB2 levels in lung tumor specimens are significantly correlated with poor patient survival, and that DAB2 over-expression significantly inhibits cell growth in cultured lung cancer cells, indicating its potent tumor suppressor function. We next identify that microRNA miR-93 functions as a potent repressor of DAB2 expression by directly targeting the 3′UTR of the DAB2 mRNA. Using in vitro and in vivo approaches, we demonstrate that miR-93 over-expression plays an important role in promoting lung cancer cell growth, and that its oncogenic function is primarily mediated by down-regulating DAB2 expression. Our clinical investigations further indicate that high tumor levels of miR-93 are correlated with poor survival of lung cancer patients. The correlations of both low DAB2 and high miR-93 expression with poor patient survival strongly support the critical role of the miR-93/DAB2 pathway in determining lung cancer progression.

Abstract 3096: miR-93-directed down-regulation of Dab2 defines a novel oncogenic pathway in lung cancer.

Abstract Introduction. The Disabled homolog 2 (DAB2) gene is located on human chromosome 5p13 and expresses a mitogen-responsive phosphoprotein. Previous studies have indicated that DAB2 is a tumor suppressor gene and is down-regulated in multiple cancer types, suggesting that repressed DAB2 expression plays an important role in oncogenesis. Loss of Dab2 protein expression has also been observed in lung cancer. The molecular and clinical consequences of loss of Dab2 expression in lung cancers, however, have not been fully evaluated, and the mechanisms of its dysregulation in cancers need to be defined. Aims and Methods. We aim to determine the role of DAB2 in lung tumorigenesis, and the role of microRNAs (miRNAs) in regulating Dab2 expression in lung cancer cells. Using in silico and in vitro approaches, we identified DAB2 as a direct target of miR-93. Using in vitro approaches, we investigated the function of Dab2 and miR-93 in regulating lung cancer cell growth. To investigate the clinical significance of DAB2 and miR-93 dysregulation in lung cancer patients, we examined the correlation of miR-93 and DAB2 tumor levels with lung cancer patient survival, and investigated the correlation between miR-93 and DAB2 expression in lung tumor specimens. Results and Conclusions. We show that Dab2 overexpression significantly arrests cell growth in lung cancer cells in vitro, and that low DAB2 mRNA levels in human lung tumor specimens are significantly correlated with poor patient survival. These results indicate that Dab2 is a potent tumor suppressor in lung cancer and that DAB2 levels may be an important factor in determining lung cancer progression and prognosis. We show that miR-93 directly targets the 3’UTR of DAB2 mRNA, and that miR-93 levels are negatively correlated with DAB2 mRNA levels in lung cancer specimens. We also show that high miR-93 levels are correlated with poor patient survival. Together these results support the clinical importance of the miR-93/Dab2 regulatory pathway in lung cancer. Overall, our study identifies a novel oncogenic pathway in lung cancer mediated by over-expression of miR-93 and subsequent down-regulation of its target DAB2. The significant correlations of both DAB2 and miR-93 expression with patient survival highlight the critical role of this pathway in lung tumorigenesis. Future studies are needed to investigate whether therapeutic tools targeting this pathway could be developed for lung cancer treatment, and whether this pathway provides a valuable prognostic biomarker for lung cancer patient survival. Citation Format: Liqin Du, Zhenze Zhao, Emily Young, Xiuye Ma, Ignacio Wistuba, Alexander Pertsemlidis. miR-93-directed down-regulation of Dab2 defines a novel oncogenic pathway in lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3096. doi:10.1158/1538-7445.AM2013-3096