Expression Of Dual-specificity Phosphatase Research Articles

RNA-seq transcriptome analysis of breast cancer cell lines under shikonin treatment

Shikonin is a naphthoquinone isolated from the dried root of Lithospermum erythrorhizon, an herb used in Chinese medicine. Although several studies have indicated that shikonin exhibits antitumor activity in breast cancer, the mechanism of action remains unclear. In the present study, we performed transcriptome analysis using RNA-seq and explored the mechanism of action of shikonin in regulating the growth of different types of breast cancer cells. The IC50 of shikonin on MCF-7, SKBR-3 and MDA-MB-231 cells were 10.3 μΜ, 15.0 μΜ, 15.0 μΜ respectively. Our results also demonstrated that shikonin arrests the progression of cell cycle and induces apoptosis in MDA-MB-231 cells. Using RNA-seq transcriptome analysis, we found 38 common genes that significantly express in different types of breast cancer cells under shikonin treatment. In particular, our results indicated that shikonin induces the expression of dual specificity phosphatase (DUSP)-1 and DUSP2 in both RNA and protein levels. In addition, shikonin also inhibits the phosphorylation of JNK and p38, the downstream signaling molecules of DUSP1 and DUSP2. Therefore, our results suggest that shikonin induces the expression of DUSP1 and DUSP2 which consequently switches off JNK and p38 MAPK pathways and causes cell cycle arrest and apoptosis in breast cancer cells.

Gefitinib enhances sensitivity of endometrial cancer cells to progestin therapy via dual-specificity phosphatase 1.

In this study, we investigated if Gefitinib, an epidermal growth factor receptor (EGFR) inhibitor, augments endometrial cancer (EC) therapy with medroxyprogesterone acetate (MPA). Combined treatment with Gefitinib plus MPA decreased the proliferation and invasiveness of the Ishikawa and RL952 EC cell lines more effectively than MPA treatment alone. Moreover, combined treatment with Gefitinib plus MPA reduced growth of EC xenografts in Balb/c nude mice more than either Gefitinib or MPA alone. The therapeutic efficacy of combined Gefitinib plus MPA treatment was dependent on expression of dual-specificity phosphatase 1 (DUSP1). DUSP1 knockdown in Ishikawa cells treated with Gefitinib plus MPA showed greater proliferation and invasiveness than parental Ishikawa cells treated similarly. EC cells treated with the combination of Gefitinib plus MPA also showed DUSP1-dependent reductions in phospho-ERK1/2 and increases in E-Cadherin. Thus, Gefitinib appears to DUSP1-dependently enhance the therapeutic efficacy of progestin in EC cells.

Expression Profiling of the MAP Kinase Phosphatase Family Reveals a Role for DUSP1 in the Glioblastoma Stem Cell Niche.

The dual specificity phosphatases (DUSPs) constitute a family of stress-induced enzymes that provide feedback inhibition on mitogen-activated protein kinases (MAPKs) critical in key aspects of oncogenic signaling. While described in other tumor types, the landscape of DUSP mRNA expression in glioblastoma (GB) remains largely unexplored. Interrogation of the REpository for Molecular BRAin Neoplasia DaTa (REMBRANDT) revealed induction (DUSP4, DUSP6), repression (DUSP2, DUSP7-9), or mixed (DUSP1, DUSP5, DUSP10, DUSP15) DUSP transcription of select DUSPs in bulk tumor specimens. To resolve features specific to the tumor microenvironment, we searched the Ivy Glioblastoma Atlas Project (Ivy GAP) repository, which highlight DUSP1, DUSP5, and DUSP6 as the predominant family members induced within pseudopalisading and perinecrotic regions. The inducibility of DUSP1 in response to hypoxia, dexamethasone, or the chemotherapeutic agent camptothecin was confirmed in GB cell lines and tumor-derived stem cells (TSCs). Moreover, we show that loss of DUSP1 expression is a characteristic of TSCs and correlates with expression of tumor stem cell markers in situ (ABCG2, PROM1, L1CAM, NANOG, SOX2). This work reveals a dynamic pattern of DUSP expression within the tumor microenvironment that reflects the cumulative effects of factors including regional ischemia, chemotherapeutic exposure among others. Moreover, our observation regarding DUSP1 dysregulation within the stem cell niche argue for its importance in the survival and proliferation of this therapeutically resistant population.

Characterization of MK-4166, a Clinical Agonistic Antibody That Targets Human GITR and Inhibits the Generation and Suppressive Effects of T Regulatory Cells.

GITR is a T-cell costimulatory receptor that enhances cellular and humoral immunity. The agonist anti-mouse GITR antibody DTA-1 has demonstrated efficacy in murine models of cancer primarily by attenuation of Treg-mediated immune suppression, but the translatability to human GITR biology has not been fully explored. Here, we report the potential utility of MK-4166, a humanized GITR mAb selected to bind to an epitope analogous to the DTA-1 epitope, which enhances the proliferation of both naïve and tumor-infiltrating T lymphocytes (TIL). We also investigated the role of GITR agonism in human antitumor immune responses and report here the preclinical characterization and toxicity assessment of MK-4166, which is currently being evaluated in a phase I clinical study. Expression of human GITR was comparable with that of mouse GITR in tumor-infiltrating Tregs despite being drastically lower in other human TILs and in many human peripheral blood populations. MK-4166 decreased induction and suppressive effects of Tregsin vitro In human TIL cultures, MK-4166 induced phosphorylation of NFκB and increased expression of dual specificity phosphatase 6 (DUSP6), indicating that MK-4166 activated downstream NFκB and Erk signaling pathways. Furthermore, MK-4166 downregulated FOXP3 mRNA in human tumor infiltrating Tregs, suggesting that, in addition to enhancing the activation of TILs, MK-4166 may attenuate the Treg-mediated suppressive tumor microenvironment. Cancer Res; 77(16); 4378-88. ©2017 AACR.

Long non-coding RNA MIAT promotes breast cancer progression and functions as ceRNA to regulate DUSP7 expression by sponging miR-155-5p.

Long non-coding RNAs (lncRNA) have been reported as key regulators in the progression and metastasis of breast cancer. In this study, we found that the lncRNA myocardial infarction associated transcript (MIAT) expression was upregulated in breast cancer in The Cancer Genome Atlas (TCGA) data sets. We validated that MIAT was higher in breast cancer cell lines and advanced breast tumors than in normal controls. And MIAT overexpression associated with TNM stage and lymphnode metastasis. Knockdown MIAT inhibited breast cancer cell proliferation and promoted apoptosis. Also MIAT downregulation suppressed epithelial-mesenchymal transition (EMT) and decreased migration and invasion in MDA-MB-231 and MCF-7 breast cancer cell lines. More importantly, knockdown MIAT inhibited tumor growth in vivo. Our results suggested that MIAT acted as a competing endogenous RNA (ceRNA) to regulate the expression of dual specificity phosphatase 7 (DUSP7) by taking up miR-155-5p in breast cancer. There were positive correlation between MIAT and DUSP7 expression in breast cancer patients. We conclude that MIAT promotes breast cancer progression and functions as ceRNA to regulate DUSP7 expression by sponging miR-155-5p in breast cancer.

Macrophage responses to lipopolysaccharide are modulated by a feedback loop involving prostaglandin E2, dual specificity phosphatase 1 and tristetraprolin

In many different cell types, pro-inflammatory agonists induce the expression of cyclooxygenase 2 (COX-2), an enzyme that catalyzes rate-limiting steps in the conversion of arachidonic acid to a variety of lipid signaling molecules, including prostaglandin E2 (PGE2). PGE2 has key roles in many early inflammatory events, such as the changes of vascular function that promote or facilitate leukocyte recruitment to sites of inflammation. Depending on context, it also exerts many important anti-inflammatory effects, for example increasing the expression of the anti-inflammatory cytokine interleukin 10 (IL-10), and decreasing that of the pro-inflammatory cytokine tumor necrosis factor (TNF). The tight control of both biosynthesis of, and cellular responses to, PGE2 are critical for the precise orchestration of the initiation and resolution of inflammatory responses. Here we describe evidence of a negative feedback loop, in which PGE2 augments the expression of dual specificity phosphatase 1, impairs the activity of mitogen-activated protein kinase p38, increases the activity of the mRNA-destabilizing factor tristetraprolin, and thereby inhibits the expression of COX-2. The same feedback mechanism contributes to PGE2-mediated suppression of TNF release. Engagement of the DUSP1-TTP regulatory axis by PGE2 is likely to contribute to the switch between initiation and resolution phases of inflammation.

DUSP1 and KCNJ2 mRNA upregulation can serve as a biomarker of mechanical asphyxia-induced death in cardiac tissue.

The incidence of death by asphyxia is second to the incidence of death by mechanical injury; however, death by mechanical asphyxia may be difficult to prove in court, particularly in cases in which corpses do not exhibit obvious signs of asphyxia. To identify a credible biomarker of asphyxia, we first examined the expression levels of 47,000 mRNAs in human cardiac tissue specimens from individuals who died of mechanical asphyxia and compared the expression levels with the levels of the corresponding mRNAs in specimens from individuals who died of craniocerebral injury using microarray. We selected 119 differentially expressed mRNAs, examined the expression levels of these mRNAs in 44 human cardiac tissue specimens of individuals who died of mechanical asphyxia, craniocerebral injury, hemorrhagic shock, or other causes. That the expression of dual-specificity phosphatase 1 (DUSP1) and potassium voltage-gated channel subfamily J member 2 (KCNJ2) was upregulated in human cardiac tissues from the mechanical asphyxia group compared with control tissues, regardless of age, environmental temperature, and postmortem interval (PMI), indicating that DUSP1 and KCNJ2 may be associated with mechanical asphyxia-induced death and can thus serve as useful biomarkers of death by mechanical asphyxia.

The Lactobacillus rhamnosus R0011 secretome attenuates TNFα-induced pro-inflammatory gene expression in human HT-29 intestinal epithelial cells

Abstract Probiotic lactic acid bacteria have been associated with a wide array of host-immune modulatory effects including modulation of pro-inflammatory gene expression. However, many questions remain about the exact cellular mechanisms through which these bacteria modulate host cell responses following pro-inflammatory challenge. The aim of this study was to elucidate the effects of the Lactobacillus rhamnosus R0011 secretome on TNFα-induced pro-inflammatory gene expression. Previous analysis has shown that the <10kDa fraction of the Lr R0011 secretome attenuates TNFα-induced IL-8 production from HT-29 intestinal epithelial cells (IECs). Whole-genome wide microarray analysis was used to further interrogate the impact of the <10kDa fraction of the Lr R0011 secretome on TNFα-induced gene expression. Contact with the <10kDa secretome fraction alone induced minimal changes in global gene expression by HT-29 IECs, with no increases in pro-inflammatory gene expression. However, the <10kDa fraction of the Lr R0011 secretome attenuated TNFα-induced expression of the pro-inflammatory mediators CCL10, CXCL1, CXCL10, CXCL11, IL-1β, IL-8, IL-17C, IL-23A, IL-32, and PTGS2, when compared to HT-29 IEC treated with TNFα alone. Co-challenge of HT-29 IECs with the <10kDa fraction of the Lr R0011 secretome and TNFα also resulted in an increase in the expression of dual specificity phosphatase 1 (DUSP1), a key regulator of the MAPK pathway, and of activating transcription factor 3 (ATF3), a negative regulator of innate immunity, relative to HT-29 IECs treated with TNFα alone. This provides insight into mechanisms through which these bacteria may influence innate immune activity at the IEC level through soluble mediators.

Loss of cohesin complex components STAG2 or STAG3 confers resistance to BRAF inhibition in melanoma.

The protein kinase V-Raf murine sarcoma viral oncogene homolog B (BRAF) is an oncogenic driver and therapeutic target in melanoma. Inhibitors of BRAF (BRAFi) have shown high response rates and extended survival in melanoma patients bearing tumors that express BRAF Val600 mutations, but a vast majority of these patients develop drug resistance. Here we show that loss of Stromal antigen 2 or 3 (STAG2 or STAG3), which encode subunits of the cohesin complex, in melanoma cells results in resistance to BRAFi. We identified loss-of-function mutations in STAG2 as well as decreased expression of STAG2 or STAG3 proteins in several tumor samples from patients with acquired resistance to BRAFi and in BRAFi-resistant melanoma cell lines. Knockdown of STAG2 or STAG3 decreased sensitivity of Val600Glu BRAF-mutant melanoma cells and xenograft tumors to BRAFi. Loss of STAG2 inhibited CCCTC-binding factor (CTCF)-mediated expression of dual specificity phosphatase 6 (DUSP6), leading to reactivation of ERK signaling. Our studies unveil a previously unknown genetic mechanism of BRAFi resistance and provide new insights into the tumor suppressor function of STAG2 and STAG3.

Long Noncoding RNA PICSAR Promotes Growth of Cutaneous Squamous Cell Carcinoma by Regulating ERK1/2 Activity

Keratinocyte-derived cutaneous squamous cell carcinoma (cSCC) is the most common metastatic skin cancer, and its incidence is increasing globally. Long noncoding RNAs (lncRNA) are involved in various biological processes, and their role in cancer progression is emerging. Whole transcriptome analysis of cSCC cells (n= 8) and normal human epidermal keratinocytes (n= 4) revealed overexpression of long intergenic ncRNA (LINC00162) in cSCC cells. The expression of LINC00162 in cSCC cells was upregulated by inhibition of the p38α and p38δ mitogen-activated protein kinases. Analysis of tissue sections by RNA in situ hybridization showed that LINC00162 is specifically expressed by tumor cells in cSCCs but not by keratinocytes in normal skin invivo. Knockdown of LINC00162 inhibited proliferation and migration of cSCC cells, and suppressed the growth ofhuman cSCC xenografts invivo. Furthermore, knockdown of LINC00162 inhibited extracellular signal-regulated kinase 1/2 activity and upregulated expression of dual specificity phosphatase 6 (DUSP6) in cSCC cells. Based on these observations, LINC00162 was named p38 inhibited cutaneous squamous cell carcinoma associated lincRNA (PICSAR). Our results provide mechanistic evidence for the role of PICSAR in promoting cSCC progression via activation of extracellular signal-regulated kinase 1/2 signaling pathway by downregulating DUSP6 expression. These results also identify PICSAR as a biomarker and putative therapeutic target incSCC.

Integrin-linked Kinase Controls Renal Branching Morphogenesis via Dual Specificity Phosphatase 8.

Integrin-linked kinase (ILK) is an intracellular scaffold protein with critical cell-specific functions in the embryonic and mature mammalian kidney. Previously, we demonstrated a requirement for Ilk during ureteric branching and cell cycle regulation in collecting duct cells in vivo Although in vitro data indicate that ILK controls p38 mitogen-activated protein kinase (p38MAPK) activity, the contribution of ILK-p38MAPK signaling to branching morphogenesis in vivo is not defined. Here, we identified genes that are regulated by Ilk in ureteric cells using a whole-genome expression analysis of whole-kidney mRNA in mice with Ilk deficiency in the ureteric cell lineage. Six genes with expression in ureteric tip cells, including Wnt11, were downregulated, whereas the expression of dual-specificity phosphatase 8 (DUSP8) was upregulated. Phosphorylation of p38MAPK was decreased in kidney tissue with Ilk deficiency, but no significant decrease in the phosphorylation of other intracellular effectors previously shown to control renal morphogenesis was observed. Pharmacologic inhibition of p38MAPK activity in murine inner medullary collecting duct 3 (mIMCD3) cells decreased expression of Wnt11, Krt23, and Slo4c1 DUSP8 overexpression in mIMCD3 cells significantly inhibited p38MAPK activation and the expression of Wnt11 and Slo4c1. Adenovirus-mediated overexpression of DUSP8 in cultured embryonic murine kidneys decreased ureteric branching and p38MAPK activation. Together, these data demonstrate that Ilk controls branching morphogenesis by regulating the expression of DUSP8, which inhibits p38MAPK activity and decreases branching morphogenesis.

Decreased expression of dual specificity phosphatase 22 in colorectal cancer and its potential prognostic relevance for stage IV CRC patients.

Dual specificity phosphatase 22 (DUSP22) is a novel dual specificity phosphatase that has been demonstrated to be a cancer suppressor gene associated with numerous biological and pathological processes. However, little is known of DUSP22 expression profiling in colorectal cancer and its prognostic value. Our study aims to investigate the role of DUSP22 expression in the prognosis of colorectal cancer. We detected the mRNA expression in 92 paired primary colorectal cancer tissues and the corresponding adjacent normal tissues by using QuantiGenePlex assay. The Friedman test was used to determine the statistical difference of gene expression. Kaplan-Meier survival analysis was performed. Mann-Whitney test and Kruskal-Wallis test were used to conduct data analyses to determine the prognostic value. Statistical significance was set at P < 0.05. In 74 of 92 cases, DUSP22 mRNA was reduced in primary colorectal cancer tissues, compared to the adjacent normal tissues. The mRNA levels of DUSP22 were significantly lower in colorectal cancer tissues than in adjacent normal tissues (0.0290 vs. 0.0658; P < 0.001). Low expression of DUSP22 correlated significantly with large tumor size (P = 0.013). No association was observed between DUSP22 mRNA expression and differentiation, histopathological type, tumor invasion, lymph node metastases, metastases, TNM stage, and Duke's phase (all P > 0.05). Kaplan-Meier analysis indicated that DUSP22 expression had no significant relationship with overall survival in all patients (P > 0.05). Interestingly, low expression level of DUSP22 in stage IV patients had a poor survival measures with a marginal P value (P = 0.07). Reduced DUSP22 expression was found in colorectal cancer specimens. Low expression level of DUSP22 in stage IV patients had a poor survival outcome. Further study is required for the investigation of the role of DUSP22 in colorectal cancer.

Su1960 The Expression of Dual Specificity Phosphatases 1, 5 and 6 Is Modulated by Acid and Bile Acid Exposure and Varies at Different Stages of Esophageal Carcinogenesis

Su1960 The Expression of Dual Specificity Phosphatases 1, 5 and 6 Is Modulated by Acid and Bile Acid Exposure and Varies at Different Stages of Esophageal Carcinogenesis

Disruption of a regulatory loop between DUSP1 and p53 contributes to hepatocellular carcinoma development and progression

Altered expression of dual specificity phosphatase 1 (DUSP1) is common in tumors including hepatocellular carcinoma (HCC), and is predictive of tumor progression and poor prognosis. However, the tumor suppressive role of DUSP1 has yet to be clearly elucidated. The molecular mechanisms of tumor suppression that were investigated were induction of apoptosis, cell cycle inhibition, and regulation of p53. Additionally, the antitumor effect of DUSP1 was assessed using a mouse model. Associated signaling pathways in HCC cells and tissues were examined. Downregulation of DUSP1 expression was significantly correlated with poor differentiation (p<0.001) and advanced HCC stage (p=0.023). DUSP1 expression resulted in HCC suppression and longer survival (p=0.0002) in a xenoplant mice model. DUSP1 inhibited p38 MAPK phosphorylation and subsequently suppressed HSP27 activation, resulting in enhanced p53 phosphorylation at sites S15, S20, and S46 in HCC cells. Enhanced p53 activation induced the expression of target genes p21 and p27, which are linked to cell cycle arrest and apoptosis. Thus, DUSP1 was potentially linked to p53 activation via the p38 MAPK/HSP27 pathway. Wild-type but not mutant p53 transcriptionally upregulated DUSP1 via its DNA-binding domain. DUSP1 and p53 might collaborate to suppress tumors in hepatocarcinogenesis via a positive regulatory loop. Our results revealed that disruption of a positive regulatory loop between DUSP1 and p53 promoted HCC development and progression, providing a rationale for a therapeutic agent that restores DUSP1 in HCC.

Platelet-Activating Factor Induces Du-al-Specificity Phosphatase 1 and 5 Gene Expression

Platelet-activating factor (PAF) is a potent inflammatory phospholipid mediator that is known to play a role in early-phase responses in asthma and other diseases. Through its high affinity receptor, PAFR, PAF is known to activate multiple signalling pathways contributing to its proinflammatory effects. Of these pathways, the mitogen-activated protein kinase (MAPK) cascade is initiated upon PAF stimulation, leading to the activation of the conventional MAPKs ERK1/2, p38 and JNK. Since dual-specificity phosphatases (DUSP) downregulated MAPK activity, we postulated that PAF could also enhance DUSP expression and thus induced an autoregulatory loop. In this report, we studied the effect of PAF on DUSP mRNA expression in human monocytes. Our results demonstrate that PAF induces DUSP1 and DUSP5 gene expression in a time- and concentration-dependent manner, with maximal effects at PAF 100 nM and at 20 - 30 min of stimulation. In contrast, DUSP2 and DUSP6 gene expression was not enhanced by PAF. Moreover, leukotriene D4, another lipid mediator of inflammation, was unable to modulate DUSP expression. PAF-induced DUSP expression was prevented by the PAFR antagonist WEB2170 and by pretreatment with the transcriptional inhibitor Actinomycin D. Moreover, enhanced DUSP5, but not DUSP1 expression was prevented by pretreatment with the ERK inhibitor PD98059 or the PI3K inhibitor Wortmannin. Taken together, our results indicate that PAF selectively enhances DUSP1 and DUSP5 gene expressions through PAFR activation, and suggest that PAF may have an active role in the resolution of inflammation by its ability to upregulate the two DUSPs and thus provide a negative auto-regulatory signalling mechanism.

MTORC2 modulates feedback regulation of p38 MAPK activity via DUSP10/MKP5 to confer differential responses to PP242 in glioblastoma.

Dual-specificity phosphatases (DUSPs) dephosphorylate MAP kinases (MAPKs) resulting in their inactivation. Activation of MAPK signaling leads to enhanced DUSP expression, thus establishing feedback regulation of the MAPK pathway. The DUSPs are subject to regulation at the post-translational level via phosphorylation resulting in alterations of protein stability. Here we report that mTORC2 function leads to stabilization of the p38 MAPK phosphatase, DUSP10, thereby inhibiting p38 activity. We demonstrate that mTORC2 binds DUSP10 and phosphorylates DUSP10 on serine residues 224 and 230. These phosphorylation events block DUSP10 turnover resulting in inactivation of p38 signaling. We further show that insulin-stimulated PI3K/mTORC2 signaling regulates DUSP10 stability and p38 activity. Importantly, knockdown of DUSP10 or ectopic overexpression of nonphosphorylatable or phosphomimetic DUSP10 mutants was sufficient to confer differential mTOR kinase inhibitor responses to GBM cells in vitro and in murine xenografts. Finally, DUSP10 was shown to be overexpressed in a significant number of GBM patients. These data demonstrate the ability of the mTORC2 pathway to exert regulatory effects on the DUSP10/p38 feedback loop to control the cellular effects of mTOR kinase inhibitors in GBM and support the use of DUSP10 expression as a surrogate biomarker to predict responsiveness.

Metastatic tumor cells induce a crosstalk between endothelial p38 and ERK1/2 MAPK pathways activating endothelial MMP system (LB838)

Our recent results demonstrate that metastatic cell adhesive interactions with endothelial cells (EC) are stabilized by the endothelial integrin α3β1 leading to the activation of p38 and ERK1/2 pathways in endothelial cells when they interact with tumor cells. Here we demonstrate that, while FAK/Src/RhoA/ROCK/MKK3/6/p38 pathway is fully activated downstream of α3β1 in EC, endothelial ERK1/2 is progressively dephosphorylated despite time‐dependent MEK1/2 activation. We further demonstrate that ERK1/2 dephosphorylation results from a crosstalk between p38 and ERK1/2 pathways whereby p38‐dependent increase in the expression of dual specificity phosphatase MKP‐3 causes progressive ERK1/2 deactivation. The resulting outcome of this complex crosstalk between the two major endothelial MAP kinases is p38‐dependent activation of MT1‐MMP, increase in MMP‐9 expression, and progressive release of MMP‐2 from ECs. We conclude that upon interaction with ECs, metastatic cells highjack EC MMP system via α3β1‐induced crosstalk between major MAPK pathways to facilitate tumor cell extravasation.Grant Funding Source: Supported by the VA BLR&amp;D Service Award 1I01BX000609 and NIH Grant R01CA160461 to VV Glinsky

Expression of Dual-Specificity Phosphatase 5 Pseudogene 1 (DUSP5P1) in Tumor Cells

Sequencing of individual clones from a newly established cDNA library from the chemoresistant Hodgkin's lymphoma cell line L-1236 led to the isolation of a cDNA clone corresponding to a short sequence from chromosome 1. Reverse transcriptase-polymerase chain reaction indicated high expression of this sequence in Hodgkin's lymphoma derived cell lines but not in normal blood cells. Further characterization of this sequence and the surrounding genomic DNA revealed that this sequence is part of a human endogenous retrovirus locus. The sequence of this endogenous retrovirus is interrupted by a pseudogene of the dual specificity phosphatase 5 (DUSP5). Reverse transcriptase-polymerase chain reaction revealed high expression of this pseudogene (DUSP5P1) in HL cell lines but not in normal blood cells or Epstein-Barr virus-immortalized B cells. Cells from other tumor types (Burkitt's lymphoma, leukemia, neuroblastoma, Ewing sarcoma) also showed a higher DUSP5P1/DUSP5 ratio than normal cells. Furthermore, we observed that higher expression of DUSP5 in relation to DUSP5P1 correlated with the expression of the pro-apoptotic factor B cell leukemia/lymphoma 2-like 11 (BCL2L11) in peripheral blood cells and HL cells. Knock-down of DUSP5 in HL cells resulted in down-regulation of BCL2L11. Thus, the DUSP5/DUSP5P1 system could be responsible for regulation of BCL2L11 leading to inhibition of apoptosis in these tumor cells.

Obstructive sleep apnea and intermittent hypoxia increase expression of dual specificity phosphatase 1

ObjectiveDual specificity phosphatase 1 (DUSP1) inhibits mitogen activated protein kinase activity, and is activated by several stimuli such as sustained hypoxia, oxidative stress, and hormones. However, the effect of intermittent hypoxia is not known. The aim of this study was to evaluate the role of intermittent hypoxia on DUSP1 expression, and to validate its role in a human model of intermittent hypoxia, as seen in obstructive sleep apnea (OSA). OSA is characterized by recurrent episodes of hypoxemia/reoxygenation and is a known risk factor for cardiovascular morbidity. MethodsIn-vitro studies using human coronary artery endothelial cells (HCAEC) and ex-vivo studies using white blood cells isolated from healthy and OSA subjects. ResultsIntermittent hypoxia induced DUSP1 expression in human coronary artery endothelial cells (HCAEC), and in granulocytes isolated from healthy human subjects. Functionally, DUSP1 increased the expression and activity of manganese superoxide dismutase (MnSOD) in HCAEC. Further, significant increases in DUSP1 mRNA from total blood, and in DUSP1 protein in mononuclear cells and granulocytes isolated from OSA subjects, were observed in the early morning hours after one night of intermittent hypoxemia due to untreated OSA. This early-morning OSA-induced augmentation of DUSP1 gene expression was attenuated by continuous positive airway pressure (CPAP) treatment of OSA. ConclusionIntermittent hypoxia increases MnSOD activity via increased DUSP1 expression in HCAEC. Similarly, overnight intermittent hypoxemia in patients with OSA induces expression of DUSP1, which may mediate increases of MnSOD expression and activity. This may contribute significantly to neutralizing the effects of reactive oxygen species, a consequence of the intermittent hypoxemia/reperfusion elicited by OSA.

Arsenite suppression of BMP signaling in human keratinocytes

Arsenic, a human skin carcinogen, suppresses differentiation of cultured keratinocytes. Exploring the mechanism of this suppression revealed that BMP-6 greatly increased levels of mRNA for keratins 1 and 10, two of the earliest differentiation markers expressed, a process prevented by co-treatment with arsenite. BMP also stimulated, and arsenite suppressed, mRNA for FOXN1, an important transcription factor driving early keratinocyte differentiation. Keratin mRNAs increased slowly after BMP-6 addition, suggesting they are indirect transcriptional targets. Inhibition of Notch1 activation blocked BMP induction of keratins 1 and 10, while FOXN1 induction was largely unaffected. Supporting a requirement for Notch1 signaling in keratin induction, BMP increased levels of activated Notch1, which was blocked by arsenite. BMP also greatly decreased active ERK, while co-treatment with arsenite maintained active ERK. Inhibition of ERK signaling mimicked BMP by inducing keratin and FOXN1 mRNAs and by increasing active Notch1, effects blocked by arsenite. Of 6 dual-specificity phosphatases (DUSPs) targeting ERK, two were induced by BMP unless prevented by simultaneous exposure to arsenite and EGF. Knockdown of DUSP2 or DUSP14 using shRNAs greatly reduced FOXN1 and keratins 1 and 10 mRNA levels and their induction by BMP. Knockdown also decreased activated Notch1, keratin 1 and keratin 10 protein levels, both in the presence and absence of BMP. Thus, one of the earliest effects of BMP is induction of DUSPs, which increases FOXN1 transcription factor and activates Notch1, both required for keratin gene expression. Arsenite prevents this cascade by maintaining ERK signaling, at least in part by suppressing DUSP expression.