Lysine-Specific Histone Demethylase 1 Promotes Oncogenesis of the Esophageal Squamous Cell Carcinoma by Upregulating DUSP4.

Esophageal squamous cell carcinoma (ESCC) is a predominant subtype of esophageal cancer (EC) and has a poor prognosis due to its aggressive nature. Accordingly, it is necessary to find novel prognostic biomarkers and therapeutic targets for ESCC. Lysine-specific histone demethylase 1 (LSD1) plays a core role in the regulation of ESCC oncogenesis. However, the detailed mechanism of LSD1-regulated ESCC growth has not been elucidated. This study aims to explore molecular mechanism underlying the LSD1-regulated ESCC's oncogenesis. After LSD1 silencing, we detected differentially expressed genes (DEGs) in human ESCC cell line, TE-1, by transcriptome sequencing. Subsequently, we investigated expression pattern of the selected molecules in the ESCC tissues and cell lines by qRT-PCR and Western blotting. Furthermore, we explored the roles of selected molecules in ESCC using gene silencing and overexpression assays. Transcriptome sequencing showed that the expression of dual specificity phosphatase 4 (DUSP4) in TE-1 was significantly attenuated after the LSD1 silencing. In addition, the DUSP4 mRNA expression level was significantly higher in the ESCC tissues, especially in those derived from patients with invasion or metastasis. Moreover, the DUSP4 expression was positively associated with the LSD1 expression in the ESCC tissues. DUSP4 overexpression promoted proliferation, invasion, and migration of the ESCC cells, while DUSP4 silencing had an opposite effect. DUSP4 overexpression also enhanced tumorigenicity of the ESCC cells in vivo, while DUSP4 silencing inhibited tumor growth. Importantly, inhibition of cell proliferation, invasion, and migration by the LSD1 inhibitor (ZY0511) was reversed by DUSP4 overexpression. Conclusively, we found that LSD1 promotes ESCC's oncogenesis by upregulating DUSP4, the potential therapeutic and diagnostic target in ESCC.

Bone marrow macrophage-derived exosomal miR-143-5p contributes to insulin resistance in hepatocytes by repressing MKP5.

OBJECTIVE: In this study, we aim to explore the role of bone marrow macrophage-derived exosomes in hepatic insulin resistance, investigate the substance in exosomes that regulates hepatic insulin signalling pathways, reveal the specific molecular mechanisms involved in hepatic insulin resistance and further explore the role of exosomes in type 2 diabetes. MATERIALS AND METHODS: High-fat diet (HFD)-fed mice were used as obesity-induced hepatic insulin resistance model, exosomes were isolated from BMMs which were extracted from HFD-fed mice by ultracentrifugation. Exosomes were analysed the spectral changes of microRNA expression using a microRNA array. The activation of the insulin signalling pathway and the level of glycogenesis were examined in hepatocytes after transfected with miR-143-5p mimics. Luciferase assay and western blot were used to assess the target of miR-143-5p. RESULTS: BMMs from HFD-fed mice were polarized towards M1, and miR-143-5p was significantly upregulated in exosomes of BMMs from HFD-fed mice. Overexpression of miR-143-5p in Hep1-6 cells led to decreased phosphorylation of AKT and GSK and glycogen synthesis. Dual-luciferase reporter assay and western blot demonstrated that mitogen-activated protein kinase phosphatase-5 (Mkp5, also known as Dusp10) was the target gene of miR-143-5p. Moreover, the overexpression of MKP5 could rescue the insulin resistance induced by transfection miR-143-5p mimics in Hep1-6. CONCLUSION: Bone marrow macrophage-derived exosomal miR-143-5p induces insulin resistance in hepatocytes through repressing MKP5.

Evaluation of exosomal miR-9 and miR-155 targeting PTEN and DUSP14 in highly metastatic breast cancer and their effect on low metastatic cells.

Breast cancer is one of the most prevalent cancers in women. Triple-negative breast cancer consists 15% to 20% of breast cancer cases and has a poor prognosis. Cancerous transformation has several causes one of which is dysregulation of microRNAs (miRNAs) expression. Exosomes can transfer miRNAs to neighboring and distant cells. Thus, exosomal miRNAs can transfer cancerous phenotype to distant cells. We used gene expression omnibus (GEO) datasets and miRNA target prediction tools to find overexpressed miRNA in breast cancer cells and their target genes, respectively. Exosomes were extracted from MDA-MB-231 and MCF-7 cells and characterized. Overexpression of the miRNAs of MDA-MB-231 cells and their exosomes were analyzed using quantitative Real-time PCR. The target genes expression was also evaluated in the cell lines. Luciferase assay was performed to confirm the miRNAs: mRNAs interactions. Finally, MCF-7 cells were treated with MDA-MB-231 cells' exosomes. The target genes expression was evaluated in the recipient cells. GSE60714 results indicated that miR-9 and miR-155 were among the overexpressed miRNAs in highly metastatic triple negative breast cancer cells and their exosomes. Bioinformatic studies showed that these two miRNAs target PTEN and DUSP14 tumor suppressor genes. Quantitative Real-time PCR confirmed the overexpression of the miRNAs and downregulation of their targets. Luciferase assay confirmed that the miRNAs target PTEN and DUSP14. Treatment of MCF-7 cells with MDA-MB-231 cells' exosomes resulted in target genes downregulation in MCF-7 cells. We found that miR-9 and miR-155 were enriched in metastatic breast cancer exosomes. Therefore, exosomal miRNAs can transfer from cancer cells to other cells and can suppress their target genes in the recipient cells.

DUSP5 expression associates with poor prognosis in human neuroblastoma.

Regulation of growth and differentiation of neuroblastoma (NB) cells is the rational of some maintenance therapies for high-risk NB. MAP kinase phosphatases (MKPs) are potential physiologic regulators of neuronal differentiation and survival, but their expression patterns in NB are scarcely known. Here, an expression analysis of the MKP family has been performed using human NB tumor samples and human NB cell lines (SH-SY5Y, SMS-KCNR, and IMR-32) undergoing retinoic acid (RA)-induced differentiation or subjected to stimuli that activate the MAPK ERK1/2 pathway. We have identified candidate MKPs that could modulate differentiation and growth of NB cells. pERK1/2 high expression correlated with high expression of the MKP DUSP5 in NB tumors, and was associated with poor prognosis. ERK1/2 activation on SH-SY5Y cells was accompanied by increased cell proliferation, and correlated with the expression levels of DUSP5. Accordingly, siRNA knock-down of DUSP5 augmented proliferation of SH-SY5Y cells. Our findings provide insights into the dynamic expression of MKPs in NB cells, disclose DUSP5 as a potential marker of NB poor prognosis, and suggest a role for DUSP5 in limiting ERK1/2-mediated NB proliferation.

Up-regulation of DUSP5 and DUSP6 by gonadotropin-releasing hormone in cultured hypothalamic neurons, GT1-7 cells.

Gonadotropin-releasing hormone (GnRH) is secreted from hypothalamic neurons (GnRH neurons) and stimulates anterior pituitary gonadotrophs to synthesize and secrete gonadotropins. In addition to gonadotrophs, GnRH neurons also express GnRH receptors, and the autocrine action of GnRH is reportedly involved in the regulation of functions of GnRH neurons. There is accumulating evidence that extracellular signal-regulated kinase (ERK), one of mitogen-activated protein kinases (MAPKs), is activated by GnRH and involved in various effects of GnRH in GnRH neurons. In the present study, we performed microarray analysis to examine the types of genes whose expression was regulated by GnRH in immortalized mouse GnRH neurons (GT1-7 cells). We found that 257 genes among 55,681 genes examined were up-regulated after 30-min treatment of GT1-7 cells with GnRH. These up-regulated genes included four dual-specificity MAPK phosphatases (DUSPs), DUSP1, DUSP2, DUSP5, and DUSP6. Reverse transcription-polymerase chain reaction analysis confirmed that the mRNA levels of DUSP5 and DUSP6 were robustly increased within 30 min. U0126, an inhibitor of ERK activation, completely inhibited the increases in the mRNA levels of DUSP5 and DUSP6. Immunoblotting analysis revealed that ERK activation peaked at 5 min and declined steeply at 60 min, whereas DUSP5 and DUSP6 proteins were increased from 60 min. It was notable that down-regulation of DUSP6 augmented GnRH-induced ERK activation approximately 1.7-fold at 60 min. These results suggested that the up-regulation of DUSP6 regulates the duration of ERK activation at least in part.

MiR-122-5p inhibits cell migration and invasion in gastric cancer by down-regulating DUSP4.

OBJECTIVE: To explore the relationship between miR-122-5p and DUSP4 and their effects on gastric cancer (GC) cell mobility and invasiveness. METHODS: Abnormally expressed miRNAs and mRNAs were analyzed using microarrays. The miR-122-5p and DUSP4 mRNA expression levels in GC tissues and cells were determined by RT-qPCR. The target relationship between miR-122-5p and DUSP4 was validated by dual luciferase reporter assay. GC cell mobility and invasiveness were respectively observed by wound healing assay and transwell invasion assay. Western blot and immunohistochemistry were used for detection of the expressions of DUSP4 protein and MMP2 and MMP9 proteins related to cell invasion and migration. The migration and invasion abilities of gastric cancer cells in vivo were evaluated according to the number of lung metastatic nodules in mice. RESULTS: The expression of miR-122-5p in GC tissues and cells was significantly down-regulated, whereas DUSP4 expression was up-regulated. Bioinformatics prediction strategies and dual luciferase reporter assay verified the binding sites of miR-122-5p on 3'UTR of DUSP4 and the target relationship between miR-122-5p and DUSP4. Overexpression of miR-122-5p and knockdown of DUSP4 in BGC-823 cells observantly suppressed GC cell mobility and invasiveness, whereas downregulation of miR-122-5p expression promoted cell metastasis. MiR-122-5p inhibited GC cell mobility and invasiveness and pulmonary tumor metastasis via downregulation of DUSP4. CONCLUSION: MiR-122-5p restrained migration and invasion abilities of GC cells by repressing DUSP4.

Nimbolide suppresses non-small cell lung cancer cell invasion and migration via manipulation of DUSP4 expression and ERK1/2 signaling.

Nimbolide plays an important role in treating human diseases. In these years, the anticancer property of nimbolide has been paid more and more attention. However, the role of nimbolide in non-small cell lung cancer (NSCLC) remains unclear. In this study, we found that nimbolide treatment suppressed the invasion and migration of NSCLC cells, in a dose-dependent manner. Moreover, nimbolide treatment dose-dependently inhibited ERK1/2 activation, decreased Snail and MMP-3 expression, and increased E-cadherin expression. Further, we found that nimbolide treatment upregulated DUSP4 expression. DUSP4 knockdown attenuated nimbolide-mediated inhibition of cell invasion, migration and ERK1/2 activation. We also found that DUSP4 knockdown suppressed the effect of nimbolide on MMP-3, Snail and E-cadherin expression. Taken together, our study demonstrates that nimbolide treatment can upregulate the expression of DUSP4, thus inhibiting ERK1/2 activation. Inhibition of ERK1/2 pathway by nimbolide decreases MMP-3 and Snail expression, and increases E-cadherin expression, which finally inhibits NSCLC cell invasion and migration. Therefore, nimbolide may act as a novel drug to inhibit NSCLC invasion and metastasis through manipulation of ERK1/2 signaling and DUSP4 expression.

Cyclin-Dependent Kinase Inhibitor 3 Promotes Cancer Cell Proliferation and Tumorigenesis in Nasopharyngeal Carcinoma by Targeting p27.

Nasopharyngeal carcinoma (NPC) is a common malignancy of the head and neck that arises from the nasopharynx epithelium and is highly invasive. Cyclin-dependent kinase inhibitor 3 (CDKN3) belongs to the dual-specificity protein phosphatase family, which plays a key role in regulating cell division. Abnormal expression of CDKN3 has been found in numerous types of cancer. In the current study, we explored the possible role of CDKN3 in cell proliferation, ability to invade, and radiosensitivity in NPC cells. We reported that CDKN3 was upregulated and p27 was downregulated in NPC tissues and is associated with a worse prognosis for patients. In addition, downregulation of CDKN3 and upregulation of p27 decreased cell proliferation, induced cell cycle arrest, increased apoptosis, decreased cell invasion, and enhanced radiosensitivity. Silencing of p27 significantly inhibited the effects of the knockdown of CDKN3. Moreover, downregulation of CDKN3 and upregulation of p27 inhibited the increase in tumor volume and weight in implanted tumors, decreased the phosphorylation of Akt, and increased the expression of cleaved caspase 3 in tumors. CDKN3 expression was also inversely correlated with p27 expression in NPC patients. Knockdown of CDKN3 increased p27 expression. Silencing of p27 markedly inhibited the effects of CDKN3 on cell proliferation, cell cycle progression, apoptosis, invasion, and radiosensitivity. These results demonstrate that upregulation of p27 is involved in the knockdown of CDKN3-induced decrease in cell proliferation, increase in cell cycle arrest and apoptosis, decrease in invasion, and increase in radiosensitivity. The results demonstrate that the CDKN3/p27 axis may be a novel target in the treatment of NPC.

Dual-specificity phosphatase 26 (DUSP26) stimulates Aß42 generation by promoting amyloid precursor protein axonal transport during hypoxia.

Amyloid beta peptide (Aß) is a pathological hallmark of Alzheimer's disease (AD) and is generated through the sequential cleavage of amyloid precursor protein (APP) by ß- and γ-secretases. Hypoxia is a known risk factor for AD and stimulates Aß generation by γ-secretase; however, the underlying mechanisms remain unclear. In this study, we showed that dual-specificity phosphatase 26 (DUSP26) regulates Aß generation through changes in subcellular localization of the γ-secretase complex and its substrate C99 under hypoxic conditions. DUSP26 was identified as a novel γ-secretase regulator from a genome-wide functional screen using a cDNA expression library. The phosphatase activity of DUSP26 was required for the increase in Aß42 generation through γ-secretase, but this regulation did not affect the amount of the γ-secretase complex. Interestingly, DUSP26 induced the accumulation of C99 in the axons by stimulating anterograde transport of C99-positive vesicles. Additionally, DUSP26 induced c-Jun N-terminal kinase (JNK) activation for APP processing and axonal transport of C99. Under hypoxic conditions, DUSP26 expression levels were elevated together with JNK activation, and treatment with JNK inhibitor SP600125, or the DUSP26 inhibitor NSC-87877, reduced hypoxia-induced Aß generation by diminishing vesicle trafficking of C99 to the axons. Finally, we observed enhanced DUSP26 expression and JNK activation in the hippocampus of AD patients. Our results suggest that DUSP26 mediates hypoxia-induced Aß generation through JNK activation, revealing a new regulator of γ-secretase-mediated APP processing under hypoxic conditions. We propose the role of phosphatase dual-specificity phosphatase 26 (DUSP26) in the selective regulation of Aß42 production in neuronal cells under hypoxic stress. Induction of DUSP26 causes JNK-dependent shift in the subcellular localization of γ-secretase and C99 from the cell body to axons for Aß42 generation. These findings provide a new strategy for developing new therapeutic targets to arrest AD progression.

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.

Epigenetic silencing of DUSP9 induces the proliferation of human gastric cancer by activating JNK signaling.

Dual-specificity phosphatase 9 (DUSP9) is a strong negative regulator of transcription factor activating kinases (ERK, JNK and p38) in the mitogen-activated protein kinase (MAPK) pathways. The aim of this study was to examine the CpG island methylation status of DUSP9 using bisulfite sequencing PCR (BSP) in gastric cancer (GC). The investigation was conducted on 30 clinical GC samples and selected corresponding tumor-free normal gastric mucosa tissues, using BSP for the determination of the promoter methylation status. The methylation status of the tumor samples was compared to the corresponding tumor-free samples. DUSP9 was silenced by promoter region hypermethylation and G2/M phase arrest was induced by DUSP9 in the MKN-1 GC cell line. MKN-1 proliferation was suppressed by DUSP9 by inhibiting c-Jun, which was induced by JNK signaling. The expression levels of CCND1, c-Jun, CDK4 and CDK6 were upregulated while p21 was downregulated by DUSP9 in MKN-1 cells. However, DUSP9-induced resulted in the regulation of the levels of cycle-related molecules, whivh were inhibited when the JNK inhibitor SP600125 was added. In conclusion, DUSP9 was frequently methylated in human GC and the expression of DUSP9 is silenced by promoter region hypermethylation. The results of this study, combined with previous studies, suggested that therapeutic intervention to increase the expression or activity of DUSP9 may enable the activation of anti-proliferation signals in malignant cells.

KAP regulates ROCK2 and Cdk2 in an RNA-activated glioblastoma invasion pathway.

Aberrant splicing of the cyclin-dependent kinase-associated phosphatase, KAP, promotes glioblastoma invasion in a Cdc2-dependent manner. However, the mechanism by which this occurs is unknown. Here we show that miR-26a, which is often amplified in glioblastoma, promotes invasion in phosphatase and tensin homolog (PTEN)-competent and PTEN-deficient glioblastoma cells by directly downregulating KAP expression. Mechanistically, we find that KAP binds and activates ROCK2. Thus, RNA-mediated downregulation of KAP leads to decreased ROCK2 activity and this, in turn, increases Rac1-mediated invasion. In addition, the decrease in KAP expression activates the cyclin-dependent kinase, Cdk2, and this directly promotes invasion by increasing retinoblastoma phosphorylation, E2F-dependent Cdc2 expression and Cdc2-mediated inactivation of the actomyosin inhibitor, caldesmon. Importantly, glioblastoma cell invasion mediated by this pathway can be antagonized by Cdk2/Cdc2 inhibitors in vitro and in vivo. Thus, two distinct RNA-based mechanisms activate this novel KAP/ROCK2/Cdk2-dependent invasion pathway in glioblastoma.

Dual specificity phosphatase 4 gene expression in association with triple-negative breast cancer outcome.

Triple-negative breast cancer (TNBC) is an aggressive cancer with limited treatment options. Dual specificity phosphatase 4 (DUSP4) has recently been suggested as a potential marker of chemotherapy resistance for TNBC. DUSP4 gene expression levels were measured in breast cancer tissue from 469 TNBC patients aged 20-75 years who participated in the Shanghai Breast Cancer Survival Study, and their association with recurrence/breast cancer mortality and total mortality was evaluated. Information on breast cancer diagnosis, treatment, and disease progression was collected via medical chart review and multiple in-person follow-up surveys. A Cox regression model was applied in the data analyses. Over a median follow-up of 5.3 years (range: 0.7-8.9 years), 100 deaths and 92 recurrences/breast cancer deaths were documented. Expression levels of transcript variant 1 (NM_001394) and transcript variant 2 (NM_057158) of the DUSP4 gene were studied and were highly correlated (r = 0.76). Low DUSP4 expression levels, particularly of variant 1, were associated with both increased recurrence/breast cancer mortality and increased overall mortality. Hazard ratios with adjustment for age at diagnosis and TNM stage associated with below versus above the median expression level were 1.97 (95 % confidence interval (CI): 1.27-3.05) for recurrence/breast cancer mortality and 2.09 (95 % CI: 1.38-3.17) for overall mortality. Additional adjustment for expression levels of MKI67 and TP53, common treatment types, breast cancer subtype, and grade did not materially alter the observed associations. Low DUSP4 expression levels predict recurrence and mortality in TNBC patients independently from known clinical and molecular predictors.

DUSP28 contributes to human hepatocellular carcinoma via regulation of the p38 MAPK signaling.

DUSP28, a member of the atypical dual­specificity phosphatase (DUSP) family, is a candidate tumor-related gene in hepatocellular carcinoma (HCC) selected by genome­wide approach, but its pathological role in HCC has not been elucidated. Here, we report for the first time that DUSP28 is involved in HCC progression. Quantitative real­time PCR and semi­quantitative RT-PCR showed notably elevated expression of DUSP28 in HCC specimens compared to that in corresponding adjacent non­tumor liver. DUSP28 overexpression promoted HCC cell proliferation, colony formation and soft agar colony formation in vitro while DUSP28 knockdown resulted in the opposite effects. Furthermore, the flow cytometric analysis indicated that DUSP28 could lead to an increased population of cancer cells in S phase, with a concomitant decrease of cells in G1 phase. Investigation of the mechanism revealed that DUSP28 could activate the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Taken together, these data demonstrate that DUSP28 plays a significant role in HCC progression and may be a feasible molecular target for anti-cancer therapy.

Microarray phosphatome profiling of breast cancer patients unveils a complex phosphatase regulatory role of the MAPK and PI3K pathways in estrogen receptor-negative breast cancers.

Phosphatases are proteins with the ability to dephosphorylate different substrates and are involved in critical cellular processes such as proliferation, tumor suppression, motility and survival. Little is known about their role in the different breast cancer (BC) phenotypes. We carried out microarray phosphatome profiling in 41 estrogen receptor-negative (ER-) BC patients, as determined by immunohistochemistry (IHC), containing both ERBB2+ and ERBB2- in order to characterize the differences between these two groups. We characterized and confirmed the distinct phosphatome of the two main ER- BC subgroups (in two independent microarrays series) and that of ER+ BC (in three large independent series). Our findings point to the importance of the MAPK and PI3K pathways in ER- BCs as some of the most differentially expressed phosphatases (like DUSP4 and DUSP6) sharing ERK as substrate, or regulating the PI3K pathway (INPP4B, PTEN). It was possible to identify a selective group of phosphatases upregulated only in the ER- ERBB2+ subgroup and not in ER+ (like DUSP6, DUSP10 and PPAPDC1A among others), suggesting a role of these phosphatases in specific BC subtypes, unlike other differentially expressed phosphatases (DUSP4 and ENPP1) that seemed to have a role in multiple BC subtypes. Significant correlation was found at the protein level by IHC between the expression of DUSP6 and phospho-ERK (p=0.04) but not of phospho-ERK with DUSP4. To show the potential prognostic relevance of phosphatases as a functional group of genes, we derived and validated in two large independent BC microarray series a multiphosphatase signature enriched in differentially expressed phosphatases, to predict distant metastasis-free survival (DMFS). ER- ERBB2+, ER- ERBB2- and ER+ BC patients have a distinct pattern of phosphatase RNA expression with a potential prognostic relevance. Further studies of the most relevant phosphatases found in this study are warranted.

MEK inhibition as a strategy for targeting residual breast cancer cells with low DUSP4 expression.

Lack of eradication of disseminated breast cancer by chemotherapy is a central clinical problem. Even tumors that show substantial shrinkage after drug treatment frequently relapse and eventually become refractory to all drugs available. The mechanisms underlying this lack of eradication are largely undefined and it is therefore difficult to develop curative strategies using systemic anti-cancer therapy. In a recent article low DUSP4 expression was reported to activate RAS-ERK signaling in residual breast cancer after neoadjuvant chemotherapy. This may be a druggable characteristic because MEK inhibition increases docetaxel sensitivity in a xenograft model.

The inhibitory effect of rapamycin on the oval cell response and development of preneoplastic foci in the rat.

Oval cell activation occurs under conditions of severe liver injury when normal hepatocyte proliferation is blocked. Recent studies have shown that a subset of hepatocellular carcinomas expresses oval cell markers, suggesting that these cells are targets of hepatocarcinogens. However, the signaling pathways that control oval cell activation and proliferation are not well characterized. Based on the role of the nutrient signaling kinase complex, mTORC1, in liver development, we investigated the role of this pathway in oval cell activation. Oval cell proliferation was induced in male Fisher rats by a modification of the traditional choline deficient plus ethionine model (CDE) or by 2-acetylaminoflourene treatment followed by 2/3 partial hepatectomy with or without initiation by diethylnitrosamine. To assess the role of mTOR in the oval cell response and development of preneoplastic foci, the effect of the mTORC1 inhibitor, rapamycin, was studied in all models. Rapamycin induced a significant suppression of the oval cell response in both models, an effect that coincided with a decrease in oval cell proliferation. Rapamycin administration did not affect the abundance of neutrophils or natural killer cells in CDE-treated liver or the expression of key cytokines. Gene expression studies revealed the fetal hepatocyte marker MKP-4 to be expressed in oval cells. In an experimental model of hepatic carcinogenesis, rapamycin decreased the size of preneoplastic foci and the rate of cell proliferation within the foci. mTORC1 signaling plays a key role in the oval cell response and in the development of preneoplastic foci. This pathway may be a target for the chemoprevention of hepatocellular carcinoma.

Cyclin-dependent kinase inhibitor 3 is overexpressed in hepatocellular carcinoma and promotes tumor cell proliferation.

Cyclin-dependent kinase inhibitor 3 (CDKN3) belongs to the protein phosphatases family and has a dual function in cell cycling. The function of this gene has been studied in several kinds of cancers, but its role in human hepatocellular carcinoma (HCC) remains to be elucidated. In this study, we found that CDKN3 was frequently overexpressed in both HCC cell lines and clinical samples, and this overexpression was correlated with poor tumor differentiation and advanced tumor stage. Functional studies showed that overexpression of CDKN3 could promote cell proliferation by stimulating G1-S transition but has no impact on cell apoptosis and invasion. Microarray-based co-expression analysis identified a total of 61 genes co-expressed with CDKN3, with most of them involved in cell proliferation, and BIRC5 was located at the center of CDKN3 co-expression network. These results suggest that CDKN3 acts as an oncogene in human hepatocellular carcinoma and antagonism of CDKN3 may be of interest for the treatment of HCC.

Glutathione peroxidase-1 deficiency augments proinflammatory cytokine-induced redox signaling and human endothelial cell activation.

Glutathione peroxidase-1 (GPx-1) is a crucial antioxidant enzyme, the deficiency of which promotes atherogenesis. Accordingly, we examined the mechanisms by which GPx-1 deficiency enhances endothelial cell activation and inflammation. In human microvascular endothelial cells, we found that GPx-1 deficiency augments intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression by redox-dependent mechanisms that involve NFκB. Suppression of GPx-1 enhanced TNF-α-induced ROS production and ICAM-1 expression, whereas overexpression of GPx-1 attenuated these TNF-α-mediated responses. GPx-1 deficiency prolonged TNF-α-induced IκBα degradation and activation of ERK1/2 and JNK. JNK or NFκB inhibition attenuated TNF-α induction of ICAM-1 and VCAM-1 expression in GPx-1-deficient and control cells, whereas ERK1/2 inhibition attenuated only VCAM-1 expression. To analyze further signaling pathways involved in GPx-1-mediated protection from TNF-α-induced ROS, we performed microarray analysis of human microvascular endothelial cells treated with TNF-α in the presence and absence of GPx-1. Among the genes whose expression changed significantly, dual specificity phosphatase 4 (DUSP4), encoding an antagonist of MAPK signaling, was down-regulated by GPx-1 suppression. Targeted DUSP4 knockdown enhanced TNF-α-mediated ERK1/2 pathway activation and resulted in increased adhesion molecule expression, indicating that GPx-1 deficiency may augment TNF-α-mediated events, in part, by regulating DUSP4.

Characterization of the differential response of endothelial cells exposed to normal and elevated laminar shear stress.

Most acute coronary events occur in the upstream region of stenotic atherosclerotic plaques that experience laminar shear stress (LSS) elevated above normal physiological levels. Many studies have described the atheroprotective effect on endothelial behavior of normal physiological LSS (approximately 15 dynes/cm(2)) compared to static or oscillatory shear stress (OSS), but it is unknown whether the levels of elevated shear stress imposed by a stenotic plaque would preserve, enhance or reverse this effect. Therefore we used transcriptomics and related functional analyses to compare human endothelial cells exposed to laminar shear stress of 15 (LSS15-normal) or 75 dynes/cm(2) (LSS75-elevated). LSS75 upregulated expression of 145 and downregulated expression of 158 genes more than twofold relative to LSS15. Modulation of the metallothioneins (MT1-G, -M, -X) and NADPH oxidase subunits (NOX2, NOX4, NOX5, and p67phox) accompanied suppression of reactive oxygen species production at LSS75. Shear induced changes in dual specificity phosphatases (DUSPs 1, 5, 8, and 16 increasing and DUSPs 6 and 23 decreasing) were observed as well as reduced ERK1/2 but increased p38 MAP kinase phosphorylation. Amongst vasoactive substances, endothelin-1 expression decreased whereas vasoactive intestinal peptide (VIP) and prostacyclin expression increased, despite which intracellular cAMP levels were reduced. Promoter analysis by rVISTA identified a significant over representation of ATF and Nrf2 transcription factor binding sites in genes upregulated by LSS75 compared to LSS15. In summary, LSS75 induced a specific change in behavior, modifying gene expression, reducing ROS levels, altering MAP kinase signaling and reducing cAMP levels, opening multiple avenues for future study.