Dual Specificity Phosphatase Gene Research Articles

Genome-wide characterization and comparative expression profiling of dual-specificity phosphatase genes in yellow catfish (Pelteobagrus fulvidraco) after infection with exogenous Aeromonas hydrophila.

Dual-specificity phosphatases (DUSPs) are crucial regulators in many mammals, managing dephosphorylation and inactivation of mitogen-activated protein kinases (MAPKs) and playing essential roles in immune responses. However, their presence and functions in teleosts, like the yellow catfish (Pelteobagrus fulvidraco), remain unexplored. In this study, eight pfDusp genes (pfDusp1-7 and pfDusp10) were identified in yellow catfish. We characterized their molecular features, conserved protein sequences, and chromosomal localization through genome-wide analyses, and we examined their expression patterns in immune responses. Our findings reveal two conserved motifs, Leu-Phe-Leu-Gly and Ala-Tyr-Leu-Met, within the DSPc domain of DUSP proteins. The genes were mapped across seven chromosomes without evidence of duplication. Comparative analysis showed high conservation of Dusp genes across vertebrates, with evolutionary analysis suggesting Dusp3 as a potential intermediate form. Dusp transcripts were significantly upregulated in the kidney post-A. hydrophila infection. These results suggest the involvement of Dusp genes in the immune response of yellow catfish to bacterial pathogens, providing insights into their evolutionary significance and potential applications in aquaculture and molecular breeding.

Chronic Inflammatory Pain Alters Expression of Limbic MAPK Phosphatases.

Brain mechanisms involved in comorbidity between chronic pain conditions and clinical depression are still largely unknown. Our previous studies demonstrated that expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) is both necessary and sufficient for the development of enhanced behavioral emotionality (i.e., depressive- like behaviors) in rodents. Here, we investigated the role of the dual specificity phosphatase (DUSP) gene family, specifically MKP-1, MKP-2 and MKP-3, in limbic brain areas involved in affective pain processing and stress responses. Male rats exposed to 21 days of peripheral inflammatory pain exhibited a robust increase in MKP-1 gene expression within the hippocampus, prefrontal cortex (PFC) and anterior cingulate cortex (ACC). Similar upregulation of hippocampal MKP-1 was also observed in female animals exposed to the same 21-day paradigm. However, the overall pattern of MKP-1 expression across various limbic areas differed in females exposed to chronic pain, as significant downregulation of MKP-1 was observed in the ACC, while no changes were detected within the PFC. Furthermore, similar limbic region-specific variances in pain-related dysregulation were also observed for MKP-2 and MKP-3. Finally, pain-induced upregulation of limbic MKP-1 was blocked by low-dose ketamine treatment (10 mg/kg) previously shown to produce rapid antidepressant effects in rodents. Overall, the results of this study suggest that chronic pain activates specific MKPs/DUSPs within limbic brain regions, which may underlie previously reported pain-related decreases in MAPK signaling. Thus, dysregulation of MKP-1 and other DUSP genes may play an important role in the development of mood disorders associated with chronic pain state.

Identification and functional analysis of dual-specificity phosphatases (DUSP) genes in Japanese flounder (Paralichthys olivaceus) against temperature and Edwardsiella tarda stress

Dual-specificity Phosphatases (DUSPs) are not only the key regulators of dephosphorylating and inactivating mitogen-activated protein kinases (MAPKs), but play a crucial role in the immune response. However, the role of DUSP genes in Japanese flounder (PoDUSPs) is still unclear. In this study, 28 DUSP genes in Japanese flounder were identified and classified based on the whole genome database. Phylogenetic analysis and protein structure analysis revealed that DUSPs had highly conserved domains in teleosts. Molecular evolution analysis indicated that the PoDUSP genes were conservative during evolution and were functional-constrained. Meanwhile, PoDUSP genes were found to express in different embryonic and larval stages which might play the role of sentinel in healthy organisms. Furthermore, PoDUSP genes’ expression profiles after temperature stress and Edwardsiella tarda (E. tarda) infection were determined in Japanese flounder without precedent, and the results demonstrated that Podusp1, Podusp2 and Podusp16 were more respective to temperature variation whereas Podusp1 and Podusp6 were more respective to E. tarda infection. In summary, our results provide useful resources for understanding the immune responsibilities of DUSP genes in flatfish.

Upregulation of dual-specificity phosphatase-26 is required for transforming growth factor β1(TGFβ1)-induced Epithelial-mesenchymal transition in A549 and PANC1 cells.

Transforming Growth Factor β (TGFβ) proteins are potent inducers of the epithelial-mesenchymal transition (EMT) in tumor cells. Although mitogen-activated protein kinase (MAPK) family has been shown to be involved in TGFβ-induced EMT, role of Dual Specificity Phosphatases (DUSP), key regulators of MAPK activity, in TGFβ-induced EMT is largely unkonwn. Real-time qPCR analyses were performed to determine the effect of TGFβ1 on expression of EMT genes and DUSP proteins in the non-small cell lung cancer model A549 and pancreatic adenocarcinoma model PANC1 cells. Western blot analyses were conducted to study the changes in protein levels of EMT proteins and select DUSP proteins, as well as phosphorylations of MAPK proteins upon TGFβ1 stimulation. Small interfering RNA (siRNA) was utilized to reduce expressions of DUSP genes. We observed that the EMT phenotype coincided with increases in phosphorylations of the MAPK proteins ERK1/2, p38MAPK, and JNK upon TGFβ1 stimulation. Real-time qPCR analysis showed increases in DUSP15 and DUSP26 mRNA levels and Western blot analysis confirmed the increase in DUSP26 protein levels in both A549 and PANC1 cells treated with TGFβ1 relative to control. Silencing of DUSP26 expression by siRNA markedly suppressed the effect of TGFβ1 on E-cadherin and mesenchymal genes in the cells. Data provided suggest that TGFβ1 modulates the expression of DUSP genes and that upregulation of DUSP26 may be required for TGFβ1-promoted EMT in A549 and PANC1 cells. Further studies should be carried out to elucidate the requirement of individual DUSPs in TGFβ1-associated EMT in tumor cells.

DUSP4 Inactivation Leads to Reduced Extracellular Signal‒Regulated Kinase Activity through Upregulation of DUSP6 in Melanoma Cells

A subset of dual-specificity phosphatases is a major negative regulator of MAPKs, and their involvement in tumorigenesis remains controversial. Among them, DUSP4 is reported to preferentially dephosphorylate extracellular signal‒regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase over p38. In this study, we aimed to identify a possible role of DUSP4 in melanoma genesis. An examination of large-scale public data on gene expression and dependency revealed a considerably high DUSP4 expression and dependency of the melanoma cell lines compared with those of other tumor cell lines, which was not apparent for the other 24 dual-specificity phosphatases genes encoded in the human genome. Using two melanoma lines, we confirmed that DUSP4 depletion impaired cell growth without notably inducing apoptosis. Interestingly, immunoblotting and kinase translocation reporter data revealed that DUSP4 depletion induces a decrease in ERK1/2 phosphorylation but barely affects c-Jun N-terminal kinase phosphorylation, suggesting that neither ERK nor c-Jun N-terminal kinase is a direct target of DUSP4 in our experimental setting. Notably, DUSP4 depletion led to an increase in DUSP6 level, possibly through a post-transcriptional process, and DUSP6 knockout almost eliminated the DUSP4-depletion effect on cell growth and ERK activity. Our findings suggest that DUSP4 plays a role in maintaining a high ERK1/2 activity by negatively regulating DUSP6 and thus contributes to the survival and growth of melanoma cells.

Single nucleotide polymorphisms in the dual specificity phosphatase genes and risk of necrotizing enterocolitis in premature infant

Differences in the susceptibility of preterm infants to develop necrotizing enterocolitis (NEC) implicate potential genetic differences in response to the inflammatory stimuli leading to NEC. Dual specificity phosphatases (DUSPs) are a key suppressor pathway of the mitogen-activated protein kinase (MAPK) pro-inflammatory signaling pathway. We hypothesized that inherited single nucleotide polymorphisms (SNPs) in DUSP genes contribute to NEC susceptibility in premature infants. Patients admitted between 2010 and 2015 born at < 32 weeks GA and≤1,500 g BW with stage II+NEC (cases; n = 50) and age, weight-matched controls (n = 38) were included. Blood samples were collected for DNA isolation. Agena Mass Array assay was used to examine 31 SNPs in 9 different DUSP genes. Calculated minor allele frequencies (MAF) for cases and controls were compared using χ2 and logistic regression. The presence of the rs704074 SNP was associated with a 48% decreased risk of developing NEC (OR 0.52; 95% CI 0.27- 1.01, p = 0.04). The odds of surgical NEC decreased by 78% (OR 0.22; 95% CI 0.06- 0.84, p = 0.027) for each copy of rs704074/G allele in patients with NEC. In this small single-center pilot study, DUSP-6 SNP (rs704074) was associated with a lower risk of developing NEC and surgical NEC, the most severe form of NEC, in preterm infants.

Dual-specificity phosphatases in mental and neurological disorders

The dual-specificity phosphatase (DUSP) family includes a heterogeneous group of protein phosphatases that dephosphorylate both phospho-tyrosine and phospho-serine/phospho-threonine residues within a single substrate. These protein phosphatases have many substrates and modulate diverse neural functions, such as neurogenesis, differentiation, and apoptosis. DUSP genes have furthermore been associated with mental disorders such as depression and neurological disorders such as Alzheimer's disease. Herein, we review the current literature on the DUSP family of genes concerning mental and neurological disorders. This review i) outlines the structure and general functions of DUSP genes, and ii) overviews the literature on DUSP genes concerning mental and neurological disorders, including model systems, while furthermore providing perspectives for future research.

Dual-specificity phosphatase (DUSP) genetic variants predict pulmonary hypertension in patients with bronchopulmonary dysplasia.

BACKGROUND:Pulmonary hypertension (PH) in patients with bronchopulmonary (BPD) results from vasoconstriction and/or vascular remodeling, which can be regulated by mitogen-activated protein kinases (MAPK). MAPKs are deactivated by dual specificity phosphatases (DUSPs). We hypothesized that single nucleotide polymorphisms (SNPs) in DUSP genes could be used to predict PH in BPD.METHODS:Preterm infants diagnosed with BPD (n=188) were studied. PH was defined by echocardiographic criteria. Genomic DNA isolated from patient blood samples was analyzed for 31 SNPs in DUSP genes. Clinical characteristics and minor allele frequencies were compared between BPD-PH (cases) and BPD-without PH (control) groups. Biomarker models to predict PH in BPD using clinical and SNP data were tested by calculations of area under the ROC curve.RESULTS:In our BPD cohort, 32% (n=61) had PH. Of the DUSP SNPs evaluated, DUSP1 SNP rs322351 was less common, and DUSP5 SNPs rs1042606 and rs3793892 were more common in cases than in controls. The best fit biomarker model combines clinical and DUSP genetic data with an area under the ROC curve of 0.76.CONCLUSION:We identified three DUSP SNPs as potential BPD-PH biomarkers. Combining clinical and DUSP genetic data yields the most robust predictor for PH in BPD.

Dual-Specificity Phosphatases in Immunity and Infection: An Update.

Kinase activation and phosphorylation cascades are key to initiate immune cell activation in response to recognition of antigen and sensing of microbial danger. However, for balanced and controlled immune responses, the intensity and duration of phospho-signaling has to be regulated. The dual-specificity phosphatase (DUSP) gene family has many members that are differentially expressed in resting and activated immune cells. Here, we review the progress made in the field of DUSP gene function in regulation of the immune system during the last decade. Studies in knockout mice have confirmed the essential functions of several DUSP-MAPK phosphatases (DUSP-MKP) in controlling inflammatory and anti-microbial immune responses and support the concept that individual DUSP-MKP shape and determine the outcome of innate immune responses due to context-dependent expression and selective inhibition of different mitogen-activated protein kinases (MAPK). In addition to the canonical DUSP-MKP, several small-size atypical DUSP proteins regulate immune cells and are therefore also reviewed here. Unexpected and complex findings in DUSP knockout mice pose new questions regarding cell type-specific and redundant functions. Another emerging question concerns the interaction of DUSP-MKP with non-MAPK binding partners and substrate proteins. Finally, the pharmacological targeting of DUSPs is desirable to modulate immune and inflammatory responses.

Modelling the role of dual specificity phosphatases in herceptin resistant breast cancer cell lines

BackgroundBreast cancer remains the most lethal type of cancer for women. A significant proportion of breast cancer cases are characterised by overexpression of the human epidermal growth factor receptor 2 protein (HER2). These cancers are commonly treated by Herceptin (Trastuzumab), but resistance to drug treatment frequently develops in tumour cells. Dual-specificity phosphatases (DUSPs) are thought to play a role in the mechanism of resistance, since some of them were reported to be overexpressed in tumours resistant to Herceptin. ResultsWe used a systems biology approach to investigate how DUSP overexpression could favour cell proliferation and to predict how this mechanism could be reversed by targeted inhibition of selected DUSPs. We measured the expression of 20 DUSP genes in two breast cancer cell lines following long-term (6 months) exposure to Herceptin, after confirming that these cells had become resistant to the drug. We constructed several Boolean models including specific substrates of each DUSP, and showed that our models correctly account for resistance when overexpressed DUSPs were kept activated. We then simulated inhibition of both individual and combinations of DUSPs, and determined conditions under which the resistance could be reversed. ConclusionsThese results show how a combination of experimental analysis and modelling help to understand cell survival mechanisms in breast cancer tumours, and crucially enable us to generate testable predictions potentially leading to new treatments of resistant tumours.

A Phase I/II Study of Vorinostat (SAHA), Cladribine (2-CdA), and Rituximab Shows Significant Activity in Previously Untreated Mantle Cell Lymphoma

Abstract 441Background: Despite significant progress in the treatment of mantle cell lymphoma (MCL), relapse remains the norm and additional therapies are needed especially for patients who are not candidates for aggressive treatment approaches. Increasingly, it has become evident that epigenetic modifications, including DNA hypomethylation and histone deacetylase inhibition, are critical to the pathogenesis and treatment of hematologic malignancies; important to cancer biology; and may be essential to the development of treatment resistance in B-cell malignancies. Further development and understanding of new and effective treatment regimens that target the epigenome are needed.2-CdA has activity in a variety of B and T cell malignancies. In addition to its cytotoxic effects, our preliminary work shows that 2-CdA has hypomethylating properties in lymphoid malignancies. When primary MCL and CLL cells -before and 96 hours after cladribine treatment-were analyzed by HELP (HpaII tiny fragment Enrichment by Ligation mediated PCR), an array based genome-wide methylation assay, 2-CdA affected DNA hypomethylation. One of the genes hypomethylated was identified as DUSP2, a dual specificity phosphatase gene that is a p53 target gene. DUSP2 dephosphorylates phosphoserine/threonine and phosphotyrosine residues, negatively regulating mitogen-activated protein (MAP) kinases ERK1 and ERK2, which are associated with cellular proliferation and differentiation in B-NHL.Vorinostat (SAHA) is a histone deacetylase inhibitor (HDACi), which has shown modest single agent activity in lymphoma and is FDA approved for use in cutaneous T cell lymphoma (CTCL). MCL cell lines treated with cladribine activated DUSP2 mRNA and when treated with the HDAC inhibitor SAHA synergistically increased transcription of DUSP mRNA. Furthermore, MCL treated with cladribine in vitro showed inhibition of global histone methylation. Our hypothesis is that cladribine and vorinostat synergistically activate silenced genes such as but not limited to DUSP 1 and 2 that are important for tumor cell death. The mechanism of rapid tumor cell death is under investigation, and does not appear to involve the classical apoptosis pathway. Given the need for novel therapies and the potential synergy seen with 2-CdA and SAHA, we initiated a Phase I/II trial combining SAHA, 2-CdA, and rituximab (SCR) for the treatment of B-cell non-Hodgkin's Lymphoma (NHL). The Phase I portion has been completed while Phase II is actively enrolling patients including those with newly diagnosed MCL.Methods: Phase I enrolled 10 patients with relapsed/refractory NHL. The MTD of vorinostat for the Phase I was 400 mg (D 1–14) combined with 2-CdA 5mg/m2 IV (D 1–5), and R 375 mg/m2 IV (weekly × 4 for cycle 1 and 1x/month) every 28 days for up to 6 cycles. Phase II eligibility includes relapsed NHL as well as previously untreated mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL). Primary outcome is response rate (ORR). Scientific correlatives include analysis of CD20 expression, histone acetylation, gene microarray and HELP methylation analysis, ERK phosphorylation, and Q-PCR of potential target genes.Results: 52 patients (Phase I/II) have been enrolled and 45 patients have been treated. The ORR in evaluable relapsed patients (3 DLBCL, 10 MCL, 1 FL, 1 MZL, 7 CLL) is 32% (7/22). Among these relapsed patients, complete remissions (CR) have been observed in MCL as well as follicular and marginal zone lymphomas. Of the 20 previously untreated MCL patients, 19 have completed ≥ 2 cycles and are evaluable for response. ORR is 100% (19/19) with 79% (15/19) CR. Toxicities by CTCAE 3.0 criteria have primarily included reversible myelosuppression, fatigue, dehydration, 1 gr. 4 thrombo-embolic event (probably related), and 1 grade 5 pulmonary hemorrhage in a patient with relapsed pulmonary lymphoma. One previously untreated mantle cell lymphoma patient has ongoing Gr. 3 thrombocytopenia six weeks after completing therapy. Preliminary analysis of ongoing correlative studies is available in 1 MCL patient and shows DUSP2 upregulation.Conclusions: The SCR regimen shows activity across a number of B-cell malignancies and shows particular therapeutic promise in patients with previously untreated mantle cell lymphoma. Correlative studies are ongoing and will be presented. Future studies should continue to explore this regimen in previously untreated mantle cell lymphoma. Disclosures:Off Label Use: vorinostat (SAHA) is not FDA approved for the treatment of B cell lymphomas. Okada:Merck: Speakers Bureau. Epner:Merck: Speakers Bureau.

Dual-Specificity Phosphatases (DUSPs) Are Potential Targets for Pharmacologic Induction of Fetal Hemoglobin

AbstractAbstract 2075Morbidities of sickle cell anemia and β-thalassemia can be alleviated by increased fetal hemoglobin (HbF) production. However, currently available HbF inducing agents, such as HU, butyrate, and DNA methyltransferase inhibitors are not ideal due to suppression of hematopoiesis and other short and long-term side effects. Our goal is to identify novel HbF induction strategies that have the safety, efficacy and ease of use to make them applicable to most hemoglobinopathy patients. Recently, we proposed that most inducing agents increase γ-globin gene expression through activation of cell stress signaling pathways, including the p38 MAPK pathway (Mabaera et al, Exp Hematol. 2008). Evidence supporting the involvement of p38 signaling in HbF induction includes publications from multiple groups showing that γ-globin mRNA induction by several agents activates p38 signaling and can be suppressed by inhibitors of p38. Our lab has shown that physical stresses such as hyperosmotic shock, UV and X-ray irradiation, and heat shock are capable of activating p38 and inducing γ-globin mRNA expression in erythroid cells that is blocked by SB203580, a p38 inhibitor. If our model is correct, strategies that increase p38 signaling without cellular stress could be therapeutically beneficial. One possible approach is inhibition of the dual-specificity phosphatases (DUSPs) that are induced by MAPK signaling and then feedback to dephosphorylate activated MAPKs including p38. If this model is correct, suppression of DUSP activity could increase basal levels of p38 signaling without stress. Regulation of specific MAPK pathways by different DUSPs is cell-type and stress-type dependent. To determine which DUSPs are likely to be involved in p38 signaling in erythroid cells, we first used RT-PCR to determine which of ten DUSPs that are known to modulate MAPK signaling (DUSPs 1, 2, 4, 5, 6, 7, 8, 9, 10, and 16) are expressed in human erythroid progenitors and K562 cells. All ten DUSPs were expressed in both cell types. Next, we determined the effects of hemin (10 and 20μM) and Na butyrate (1 and 2mM), two known inducers of HbF and p38 MAPK signaling, on mRNA levels of the ten DUSP genes in K562 cells. γ-globin mRNA was induced by both drugs at these doses. DUSP gene expression was assessed during a short time course ranging from 5 minutes to 5 hours and a longer time course from 24 to 72 hours. At early time points, DUSP5 expression was induced up to 4-fold with both drugs when compared to untreated controls. DUSP5 continued to have the greatest level of induction at later time points (up to 8-fold) while DUSP4 and DUSP6 reached maximum induction (up to 4-fold) at 72 hours. Treatment of K562 cells with a small molecule inhibitor of DUSP1 and DUSP6, (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-iden-1-one (BCI, gift of Dr. John Lazo) at 1μM increased γ-globin mRNA levels 5-fold, similar to levels seen with hemin and butyrate, and increased p38 phosphorylation by western blotting. Together, these data suggest that DUSPs may be a molecular target for the development of novel HbF inducing agents. Disclosures:No relevant conflicts of interest to declare.

Massively Parallel Mate Pair DNA Library Sequencing for Translocation Discovery: Recurrent t(6;7)(p25.3;q32.3) Translocations In ALK-Negative Anaplastic Large Cell Lymphomas

AbstractAbstract 633 Background:To date, the only well characterized chromosomal translocations among peripheral T-cell lymphomas (PTCLs) are those involving ALK, which occur in about half of anaplastic large cell lymphomas (ALCLs). ALK-negative ALCLs remain poorly understood, despite morphology and phenotype similar to ALK-positive ALCLs. We recently described translocations near IRF4 on 6p25.3 in cutaneous ALK-negative ALCLs. In the present study, we utilized massively parallel (Next Generation) sequencing to answer three questions about these translocations: (1) Were they recurrent in the more lethal systemic form of ALK-negative ALCL? (2) What was the translocation partner? (3) What were the likely genetic consequences? Methods:We used a mate pair library approach to juxtapose DNA sequences originally lying ~5 kb apart: these paired sequences map to distinct areas of the genome if a translocation breakpoint lies between them. Because only the ends of the original DNA fragments are sequenced, this approach is more resource efficient than whole genome sequencing. Genomic DNA from a systemic ALK-negative ALCL with an uncharacterized 6p25.3 rearrangement was fragmented to 2–5 kb, biotinylated, and separated on an agarose gel. Fragments ~5-5.5 kb were excised, purified, circularized, and further fragmented to ~300-600 bp. Fragments containing biotin (representing the ends of the original 5 kb fragments) were immobilized on streptavidin beads and amplified using the Illumina library protocol. Paired end sequencing was performed on one lane of a flow cell on an Illumina GAIIx. Sequencing data were mapped to the genome using a binary indexing algorithm. Non-mapping and duplicate sequences were discarded. Candidate translocations suggested by >4 unique mate pairs were examined by BLAT to exclude false positives explained by mapping to homologous regions. PCR and Sanger sequencing of tumor DNA was used for validation. Fluorescence in situ hybridization (FISH) was performed on additional PTCLs. mRNA and miRNA expression was quantified using real-time PCR. Results:Of 28.90×106 paired sequences, 8.61×106 were non-duplicate pairs in which both ends mapped to the human genome (bridged coverage, ~7x). Only one candidate translocation involved 6p25.3, represented by 10 unique mate pairs. PCR and Sanger sequencing confirmed a balanced translocation: one breakpoint disrupted the dual-specificity phosphatase gene, DUSP22, telomeric to IRF4 on 6p25.3; the other was telomeric to the FRAH7 fragile site on 7q32.3. Additional ALK-negative ALCLs with known 6p25.3 rearrangements were tested using a 7q32.3 breakapart FISH probe, which showed a 7q32.3 rearrangement in 13/29 (45%; 7 systemic and 6 cutaneous). Dual fusion FISH confirmed t(6;7)(p25.3;q32.3) in 11/11 cases tested. None of 120 PCTLs (including 39 ALCLs) lacking 6p25.3 rearrangements had a 7q32.3 rearrangement. Levels of 5′ and 3′ DUSP22 mRNA in cases with 6p25.3 rearrangements were decreased relative to those in non-rearranged cases (5′: 0.02±0.01 vs 1.00±0.74, p=.002; 3′: 0.09±0.08 vs 1.00±0.55, p=.0002; mean±SD, t test). IRF4 mRNA levels were similar in both groups. Levels of MIR29A and MIR29B1 within FRAH7 in cases with 7q32.3 rearrangements were increased relative to those in non-rearranged cases (MIR29A: 2.44±2.20 vs 1.00±1.34, p=.15; MIR29B: 4.93±4.68 vs 1.00±1.05, p=.007). Conclusions:The t(6;7)(p25.3;q32.3) is the first recurrent translocation characterized in systemic and cutaneous ALK-negative ALCLs. This translocation was entirely specific for ALK-negative ALCLs, and was present in 45% of cases with 6p25.3 rearrangements. The t(6;7)(p25.3;q32.3) was associated with down-regulation of DUSP22 and up-regulation of MIR29, but not dysregulation of IRF4. DUSP22 inhibits mitogen activated protein kinase activity in T cells, and may represent a novel tumor suppressor in ALCLs. Increased MIR29 levels may additionally contribute to tumorigenesis, as recently shown in acute myeloid leukemias. Finally, clinical testing for t(6;7)(p25.3;q32.3) may aid in differentiating ALK-negative ALCL from other PTCLs. Our findings highlight the utility of mate-pair library sequencing to discover novel translocations in lymphoma and other cancers. Disclosures:No relevant conflicts of interest to declare.

Mutational analysis of mononucleotide repeats in dual specificity tyrosine phosphatase genes in gastric and colon carcinomas with microsatellite instability

Coordinated protein phosphorylation and dephosphorylation are crucial in the regulation of cell signaling, and disruption of the coordination is known to play important roles in cancer development. Recent reports revealed that classical protein tyrosine phosphatase (PTP)-encoded genes are somatically mutated in human colorectal cancer. However, data on dual specificity phosphatase (DPTP) gene mutations in human cancers are lacking. By analyzing a public genomic database, we found that five DPTP genes, CDC14A, MTM1, MTMR3, SSH1, and SSH2, have mononucleotide repeats in their coding DNA sequences. To see whether these genes are mutated in cancers with microsatellite instability (MSI), we analyzed the mononucleotide repeats in 26 gastric cancers (GC) with MSI (MSI-H), 12 GC with low MSI (MSI-L), 45 GC with stable MSI (MSS), 33 colorectal cancers (CRC) with MSI-H, 14 CRC with MSI-L, and 45 CRC with MSS by single-strand conformation polymorphism (SSCP). We found CDC14A and MTMR3 mutations in five and one cancer (s), respectively. These mutations were detected in MSI-H cancers, but not in MSI-L or MSS cancers. The GC and CRC with MSI-H harbored the mutations in 15% and 6%, respectively. The CDC14A and MTMR3 mutations detected in the GC and CRC were deletion or duplication mutations of one base in the nucleotide repeats that would result in premature stops of the amino acid syntheses. Our data show that frameshift mutations of DPTP genes in MSI-H cancers occur at moderate frequencies. The data suggested that alterations in the CDC14A and MTMR3 genes may play a role in the development of GC and CRC with MSI-H by deregulating phosphatase functions possibly together with mutations of classical PTP genes.

Protein tyrosine phosphatases: dual‐specificity phosphatases in health and disease

Dual-specificity phosphatases (DSPs) constitute a subfamily of protein tyrosine phosphatases (PTPs) that dephosphorylates phospho-Tyr, phospho-Ser and nonproteinaceous substrates. DSPs are involved in the regulation of both developmental and postnatal essential processes, such as early embryogenesis, placental development and immune responses. Several DSP genes are implicated in familial and sporadic human diseases, including tumor-related, neurological and muscle disorders, and cardiovascular and inflammatory diseases. This association ranges from disease-causative mutations to disease-risk-prone single-nucleotide polymorphisms, promoter methylation or gene duplication (most often in cancer). Deconvolution of the role of DSPs in disease is challenging. The enzymes' activities are regulated at many levels and they form part of extensive, intricate networks with other signaling components. Here, we review current knowledge of the role of cysteine-based PTP-domain DSPs in health and disease, and their suitability as putative therapeutic targets for drugs is discussed.

DUSP7 and DUSP8 promoter hypermethylations: Predictors of clinical outcomes in advanced epithelial ovarian carcinoma

5501 Background: The Dual specificity phosphatases (DUSPs) are a subclass of the protein tyrosine phosphatase (PTP) gene family which appears to be selective for dephosphorylating the critical phosphothreonine and phosphotyrosine residues within the mitogen-activated protein kinases (MAPKs) leading to inactivation. MAPK activation is a downstream target of several oncogenes and may give rise to oncogenic transformation, and hence DUSPs are potential tumor suppressor genes. The aim of this study was to investigate if DUSPs are subject to methylation-dependent silencing in epithelial ovarian cancer. Methods: In this study, promoter methylation and gene expression of the DUSPs genes (DUSP1, DUSP2, DUSP3, DUSP4, DUSP5, DUSP6, DUSP7, DUSP8 and DUSP10) were investigated in 9 ovarian cancer cell lines and in 74 primary epithelial ovarian tumors (Stage III/IV), using methylation specific PCR (MSP) and Reverse- transcription PCR (RT-PCR). The 74 clinical samples were retrospectively retrieved from a large Phase III RCT (the EORTC 55931/NCIC OV10) with clinical follow-up in excess of 6.5 years. Results: Ovarian Cancer Cell lines: Aberrant CpG methylation detected in DUSP1, DUSP2, DUSP4, DUSP6, DUSP7 and DUSP8. DUSP7 promoter methylation was associated with downregulation of mRNA expression. Primary Ovarian Tumors: Methylation of DUSP1, DUSP2, DUSP7 and DUSP8 was observed in 15–38% of the primary tumors. DUSP7 methylation is a predictor of adverse PFS in both univariate (median PFS 10.6 m versus 13.3m, p=0.002) and multivariate (Cox Regression HR 2.76, p&lt;0.001) analyses, and is associated with a trend for poorer OS (22.1 m versus 29.3 m, p=0.07). In contrast, DUSP8 methylation is an independent predictor of favorable PFS (median 23.7m versus 11.5m; Cox Regression HR 0.30, p=0.006) and OS (HR 0.31, p=0.013). 5-year OS for DUSP8 methylated patients was 58.3% compared with 16.1% for DUSP8 unmethylated (HR 0.277, p=0.005). Conclusion: This is the first report of DUSP methylation in epithelial ovarian cancer. The study suggests that methylation-dependent transcriptional silencing of DUSP7 in advanced epithelial ovarian cancer may represent an independent predictor of adverse PFS. DUSP8 methylation, on the other hand, is a favorable clinical outcome marker. No significant financial relationships to disclose.

Arsenite Slows S Phase Progression via Inhibition of cdc25A Dual Specificity Phosphatase Gene Transcription

Arsenic acts as a toxicant, a carcinogen, and an effective chemotherapeutic agent, but its mechanisms of action are unclear. We have previously shown that treatment of U937 cells with 5 microM sodium arsenite inhibits cell cycle progression through each cell cycle phase, including S phase. Cdc25A dual specificity phosphatase controls entry into and progression through S phase by dephosphorylating sites of inhibitory phosphorylation on cyclin E-cdk2 (Thr14 and Tyr15). Immunoblotting reveals that a 3-h treatment of U937 cells with 5 microM sodium arsenite results in a dramatic decrease in cdc25A protein levels. Coimmunoprecipitation experiments confirm that cyclin E-cdk2 is more phosphorylated at Thr14 and Tyr15 in the presence of arsenite, and kinase activity assays reveal a decrease in cyclin E-associated cdk2 activity. Therefore, arsenite-dependent cdc25A depletion could contribute to S phase inhibition. There exists an S phase checkpoint known to be mediated by proteasomal cdc25A degradation. However, cycloheximide half-life assay reveals that cdc25A is actually stabilized in arsenite-treated cells. Real-time RT-PCR shows that cdc25A mRNA levels are substantially decreased with arsenite treatment, and actinomycin D half-life assay reveals no change in message stability. Decreased cdc25A message translation is shown by sucrose density gradient polysomal analysis to be an unlikely cause for the profound arsenite-dependent reduction in cdc25A protein levels. Studies are ongoing to establish the mechanism by which 5 microM arsenite decreases cdc25A message abundance, but we surmise that, given the lack of effect on mRNA stability, an inhibition of gene transcription is likely involved.

Microarray analysis of phosphatase gene expression in human melanoma

Tyrosine phosphate is abnormally elevated in malignant melanoma, and this has been interpreted to reflect the activity of oncogenic protein tyrosine kinases. However, elevation may also arise due to decreased protein tyrosine phosphatase (PTP) expression. To survey phosphatase gene expression in melanoma cell lines, a benign naevus and normal melanocytes: we searched for downregulation of phosphatase gene expression in malignant cells that may indicate a role as melanoma suppressor genes. Microarray analysis was used to compare gene expression for 133 phosphatase genes, comprising 39 PTPs, 16 dual-specificity phosphatases (DSPs), 47 serine/threonine phosphatases and 31 acid/alkaline and lipid-based phosphatases. Northern blotting analysis was used to study gene expression in human melanoma biopsies. There was decreased expression of four DSP genes (including PTEN); eight receptor PTP genes were downregulated in melanoma, among which were PTP-KAPPA and PTP-PI (consistent with our previous data). In addition, PTP-RF/LAR was downregulated in 13 of 22 metastatic melanomas. The expression of multiple PTP receptors is decreased in melanoma; this may be a mechanism which stimulates autonomous growth in advanced melanoma.

The dual specificity phosphatase transcriptome of the murine thymus

Properly regulated mitogen-activated protein (MAP) kinase activity is critical for normal thymocyte development. MAP kinases are activated by phosphorylation of tyrosine and threonine, and dual specificity phosphatases (DUSPs) can inactivate MAP kinases by dephosphorylating both tyrosine and threonine. However, a role for DUSPs in thymocyte development has not been described. In this study, we have defined the subset of DUSP genes expressed in the murine thymus, and how their expression varies in different thymocyte subsets. Of the murine DUSP genes screened that could potentially dephosphorylate MAP kinases, we found 10 transcribed in the thymus. Seven of these 10 thymic DUSPs are true MAP kinase phosphatases based on the presence of a MAP kinase binding domain and demonstrated phosphatase activity against MAP kinases. Six of the seven thymic MAP kinase phosphatases have been shown to dephosphorylate extracellular regulated kinase (ERK). Quantitative PCR analysis of thymocyte populations isolated from different developmental stages revealed significant changes in DUSP expression as thymocytes progressed through development. Specifically, DUSPs 1, 4, and 5 significantly increase in expression as cells go from small, resting CD4/CD8 double positive cells to the CD4 single positive stage. Additionally, in vitro experiments showed that DUSPs could respond to TCR signaling, as anti-CD3 stimulation of thymocytes transiently increased transcription of six of the 10 thymic DUSP genes within 30 min. Notably, the ERK-specific phosphatase DUSP5 was upregulated 43-fold within 30 min, and returned to baseline within 24 h. Overall, we have identified a subset of DUSPs that could potentially regulate ERK activation in response to TCR signals in thymocytes.

Characterization of the myotubularin dual specificity phosphatase gene family from yeast to human.

X-linked myotubular myopathy (XLMTM) is a severe congenital muscle disorder due to mutations in the MTM1 gene. The corresponding protein, myotubularin, contains the consensus active site of tyrosine phosphatases (PTP) but otherwise shows no homology to other phosphatases. Myotubularin is able to hydrolyze a synthetic analogue of tyrosine phosphate, in a reaction inhibited by orthovanadate, and was recently shown to act on both phosphotyrosine and phosphoserine. This gene is conserved down to yeast and strong homologies were found with human ESTs, thus defining a new dual specificity phosphatase (DSP) family. We report the presence of novel members of the MTM gene family in Schizosaccharomyces pombe, Caenorhabditis elegans, zebrafish, Drosophila, mouse and man. This represents the largest family of DSPs described to date. Eight MTM-related genes were found in the human genome and we determined the chromosomal localization and expression pattern for most of them. A subclass of the myotubularin homologues lacks a functional PTP active site. Missense mutations found in XLMTM patients affect residues conserved in a Drosophila homologue. Comparison of the various genes allowed construction of a phylogenetic tree and reveals conserved residues which may be essential for function. These genes may be good candidates for other genetic diseases.