Masatoshi Ichihara

Chubu University, Касугай, Aichi, Japan

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Publications (66)315.1 Total impact

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    ABSTRACT: Although expression of gangliosides and their synthetic enzyme genes in malignant melanomas has been well studied, that in normal melanocytes has been scarcely analyzed. In particular, changes in expression levels of glycosyltransferase genes responsible for ganglioside synthesis during evolution of melanomas from melanocytes are very important to understand roles of gangliosides in melanomas. Here, expression of glycosyltransferase genes related to the ganglioside synthesis was analyzed using RNAs from cultured melanocytes and melanoma cell lines. Quantitative RT-PCR revealed that melanomas expressed high levels of mRNA of GD3 synthase and GM2/GD2 synthase genes and low levels of GM1/GD1b synthase genes compared with melanocytes. As a representative exogenous stimulation, effects of ultraviolet B (UVB) on the expression levels of 3 major ganglioside synthase genes in melanocytes were analyzed. Although direct UVB irradiation of melanocytes caused no marked changes, culture supernatants of UVB-irradiated keratinocytes (HaCaT cells) induced definite up-regulation of GD3 synthase and GM2/GD2 synthase genes. Detailed examination of the supernatants revealed that inflammatory cytokines such as TNFα and IL-6 enhanced GD3 synthase gene expression. These results suggest that inflammatory cytokines secreted from UVB-irradiated keratinocytes induced melanoma-associated ganglioside synthase genes, proposing roles of skin microenvironment in the promotion of melanoma-like ganglioside profiles in melanocytes.
    Biochemical and Biophysical Research Communications 03/2014; · 2.28 Impact Factor
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    ABSTRACT: Abstract Reactive oxygen species (ROS) play a key role in neoplastic growth and tumor invasion is supported by various experimental data. In this study, we analyzed the participation of ROS in the RET tyrosine auto-phosphorylation. The NIH3T3 cell lines transfected with cRET, MEN2A and MEN2B individually (designated NIH3T3cRET, NIH3T3 RET-MEN2A and NIH3T3RET-MEN2B) showed the elevated levels of intracellular ROS, and concomitantly increased Rac1 expression, as well as down-regulation of Mn SOD and Cu/Zn SOD in comparison with the parental cell line expressing RET. H2O2 enhanced the constitutive tyrosine auto-phosphorylation of RET-MEN2A and RET-MEN2B proteins, and this increase was attenuated by treatment with the NOX inhibitor diphenyliodonium (DPI) or catalase. We also showed that DPI inhibited dimerization of RET-MEN2A. Elevated ROS derived from NOX1 activation and down-regulation of SOD in NIH3T3RET-MEN2A and NIH3T3RET-MEN 2B cells may be involved in RET constitutive tyrosine auto-phosphorylation, and scavengers of ROS such as catalase and blocking NOX1 are useful for targeting RET tyrosine kinase activation in cancer.
    Free Radical Research 01/2014; · 3.28 Impact Factor
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    ABSTRACT: CD109, a glycosylphosphatidylinositol-anchored glycoprotein, is expressed at high levels in some human tumors including squamous cell carcinomas. As CD109 is reportedly cleaved by furin and its soluble form is secreted into culture medium in vitro, we hypothesized that CD109 could serve as a tumor marker in vivo. In this study, we investigated CD109 as a novel serum tumor marker using transgenic mice that overexpress mouse CD109 (mCD109-TG mice) and tumor xenografted mice inoculated with human CD109 (hCD109)-overexpressing HEK293 cells. In sera and urine of mCD109-TG mice, mCD109 was detected using western blotting. In xenografted mice, hCD109 secreted from inoculated tumors was detected in sera, using western blotting and CD109 ELISA. Concentrations of tumor-secreted CD109 increased proportionally as tumors enlarged. Concentrations of secreted CD109 decreased notably by 17 h after tumor resection, and became undetectable 48 h after resection. The half-life of tumor-secreted CD109 was about 5.86±0.17 h. These results indicate that CD109 is present in serum as a soluble form, and suggest its potential as a novel tumor marker in patients with cancers that express CD109.
    PLoS ONE 01/2014; 9(1):e83385. · 3.53 Impact Factor
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    ABSTRACT: Sphingosine kinase 1 (SPHK1) overexpresion in malignant cells has been reported. Mouse Friend cells showed higher SPHK1 but not SPHK2 expression compared with other mouse cell lines. A Sphk1 promoter analysis demonstrated the region between -53bp and the first exon as the minimal promoter. Further promoter truncation revealed the importance of a MYB-binding site. EMSA using this region as the probe demonstrated one band containing c-MYB protein, and its intensity decreased during erythroid differentiation with hexamethylane bisacetamide (HMBA), a potent inducer of erythroid differentiation of Friend cells. ChIP assay also revealed in vivo binding of c-MYB. c-MYB overexpression and siRNA for c-Myb affected SPHK1 expression, confirming the important regulatory role of c-MYB in SPHK1 expression. HMBA reduced c-MYB expression rapidly. Induced differentiation by HMBA caused a marked and rapid reduction of SPHK1 mRNA, protein and enzyme activity leading to the rapid decrease of cellular sphingosine 1-phosphate level. Moreover, terminally differentiated cells did not resume SPHK1 expression. Compared with original Friend cells, stable overexpression of wild-type SPHK1 showed higher cell proliferation, resistance to cell death by serum depletion. Interestingly, HMBA-induced differentiation of these cells was delayed but not completely suppressed. In contrast, SPHK inhibitor and its siRNA inhibited cell growth and enhanced HMBA-induced differentiation significantly, suggesting that SPHK1 delayed HMBA-induced differentiation by its cell proliferation-promoting activity. Effects of pertussis toxin, a G-protein-coupled receptor inhibitor, and S1P receptor antagonist on Friend cell growth and differentiation were negligible, suggesting the importance of the intracellular SPHK1/S1P signaling in Friend cells.
    Biochimica et Biophysica Acta 01/2013; · 4.66 Impact Factor
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    ABSTRACT: CD109, a glycosylphosphatidylinositol-anchored glycoprotein, is highly expressed in several types of human cancer tissues, in particular, squamous cell carcinomas. In normal human tissues, human CD109 expression is limited to certain cell types including myoepithelial cells of the mammary, lacrimal, salivary, and bronchial glands and basal cells of the prostate and bronchial epithelium. Although CD109 has been reported to negatively regulate transforming growth factor-β signaling in keratinocytes in vitro, its physiologic role in vivo remains largely unknown. To investigate the function of CD109 in vivo, we generated CD109-deficient (CD109(-/-)) mice. Although CD109(-/-) mice were born normally, transient impairment of hair growth was observed. At histologic analysis, kinked hair shafts, ectatic hair follicles with an accumulation of sebum, and persistent hyperplasia of the epidermis and sebaceous glands were observed in CD109(-/-) mice. Immunohistochemical analysis revealed thickening of the basal and suprabasal layers in the epidermis of CD109(-/-) mice, which is where endogenous CD109 is expressed in wild-type mice. Although CD109 was reported to negatively regulate transforming growth factor-β signaling, no significant difference in levels of Smad2 phosphorylation was observed in the epidermis between wild-type and CD109(-/-) mice. Instead, Stat3 phosphorylation levels were significantly elevated in the epidermis of CD109(-/-) mice compared with wild-type mice. These results suggest that CD109 regulates differentiation of keratinocytes via a signaling pathway involving Stat3.
    American Journal Of Pathology 07/2012; 181(4):1180-9. · 4.60 Impact Factor
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    ABSTRACT: Lactulose is a synthetic disaccharide that can be catalyzed only by intestinal bacteria in humans and rodents, and a large amount of hydrogen is produced by bacterial catalysis of lactulose. We previously reported marked effects of ad libitum administration of hydrogen water on prevention of a rat model of Parkinson's disease (PD). End-alveolar breath hydrogen concentrations were measured in 28 healthy subjects and 37 PD patients, as well as in 9 rats after taking hydrogen water or lactulose. Six-hydroxydopamine (6-OHDA)-induced hemi-PD model was stereotactically generated in rats. We compared effects of hydrogen water and lactulose on prevention of PD. We also analyzed effects of continuous and intermittent administration of 2% hydrogen gas. Hydrogen water increased breath hydrogen concentrations from 8.6 ± 2.1 to 32.6 ± 3.3 ppm (mean and SEM, n = 8) in 10 min in healthy subjects. Lactulose increased breath hydrogen concentrations in 86% of healthy subjects and 59% of PD patients. Compared to monophasic hydrogen increases in 71% of healthy subjects, 32% and 41% of PD patients showed biphasic and no increases, respectively. Lactulose also increased breath hydrogen levels monophasically in 9 rats. Lactulose, however, marginally ameliorated 6-OHDA-induced PD in rats. Continuous administration of 2% hydrogen gas similarly had marginal effects. On the other hand, intermittent administration of 2% hydrogen gas prevented PD in 4 of 6 rats. Lack of dose responses of hydrogen and the presence of favorable effects with hydrogen water and intermittent hydrogen gas suggest that signal modulating activities of hydrogen are likely to be instrumental in exerting a protective effect against PD.
    Medical gas research. 05/2012; 2(1):15.
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    ABSTRACT: Effects of all-trans retinoic acid (ATRA) on sphingomyelinase expression were examined using MCF-7 (ATRA-sensitive) and MDA-MB-231 (ATRA-resistant) breast cancer cells. Increased NSMase activity, NSMase2 mRNA and protein were observed in ATRA-treated MCF-7 but not in ATRA-treated MDA-MB-231. Increased NSMase2 mRNA of ATRA-treated MCF-7 was mostly due to enhanced transcription. Promoter analysis revealed the important 5'-promoter region of NSMase2 between -148 and -42 bp containing three Sp1 sites but no retinoic acid responsive elements. Experiments using mutated Sp1 sites of the NSMase2 promoter, Mithramycin A (a Sp inhibitor) and Sp family over-expression demonstrated the importance of Sp family protein and the three Sp1 sites for ATRA-induced NSMase2 transcription of MCF-7 cells. Although no quantitative change of bound Sp1 on NSMase2 promoter region after ATRA treatment was detected, Sp1 phosphorylation (activation) by ATRA was observed. Interestingly, PKCδ was involved in ATRA-induced increased NSMase2 transcription. ATRA-induced PKCδ phosphorylation and then activated PKCδ phosphorylated Sp1. Chromatin immunoprecipitation (ChIP) assay showed Sp1, RARα and RXRα complex formation in MCF-7 cells regardless of ATRA treatment and ATRA-induced acetylated histone H3 of the 5'-promoter. Thus, NSMase2 mRNA expression enhanced by ATRA was due to increased transcription via phosphorylated Sp1 caused by PKCδ activation, followed by chromatin remodelling with histone H3 acetylation.
    Journal of Biochemistry 04/2012; 151(6):599-610. · 3.07 Impact Factor
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    ABSTRACT: Growth-inhibitory effects of mimosine, a plant amino acid, on rat C6 glioma cells were analyzed. Mimosine markedly inhibited proliferation and induced apoptosis of C6 glioma cells in a dose- and time-dependent manner. Mimosine-mediated apoptosis was accompanied by promoting reactive oxygen species (ROS) generation in mitochondria, and by decreased mitochondrial membrane potential (Δψ), and release of cytochrome c from mitochondria, followed by caspase 3 activation. Furthermore, mimosine increased the phosphorylation level of c-Jun-N-terminal protein kinase and p38, which was the downstream effect of ROS accumulation. Mimosine was confirmed to show profound effects on apoptosis of C6 glioma cells by ROS-regulated mitochondria pathway, and these results bear on the hypothesized potential for mimosine as promising agents in the treatment of malignant gliomas.
    Neurochemical Research 02/2012; 37(2):417-27. · 2.13 Impact Factor
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    ABSTRACT: Invasive diseases such as toxic shock syndrome caused by Streptococcus pyogenes (S. pyogenes) are re-emerging infectious diseases. The mechanism of pathogenesis is not completely understood although the virulence of this organism has been analyzed using animal model systems, particularly using mice. The analysis of the progression of infection, however, is difficult. Computed tomography (CT) scanning is an extremely powerful technique that we applied to the mouse model of cutaneous infection with S. pyogenes. Two or three days after subcutaneous administration of bacteria, high density reticular areas were detected in the lung by CT. Histopathological examination of the lung was performed to examine the results of CT. Increased numbers of cytokeratin-positive epithelial cells, probably alveolar type II epithelial cells, were detected but no remarkable increase of inflammatory cell infiltrates was observed. Our results show that the pathological lesions of the lung in this model, wherein relatively few numbers of neutrophils were in the alveoli, are well correlated with the lung of a part of streptococcal toxic shock syndrome patients. Therefore, CT may be useful in assessing the progression of S. pyogenes infection, particularly in the pathological lesions of the lung in this model.
    Pathology International 02/2012; 62(2):99-104. · 1.72 Impact Factor
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    ABSTRACT: Recently, miR-143 and miR-145 have been shown to belong to a subset of microRNAs whose expression is controlled by a complex of a tumor suppressor p53 and DEAD-box RNA helicase subunits p68/p72. While accumulating studies have acknowledged that both miRNAs function as tumor suppressors and are similarly regulated, evidence of their coordinated action against tumorigenesis has been poorly presented. Herein, we establish transgenic mice that express miR-143 under the control of the CAG regulatory unit. When crossbred with Apc(Min/+) mice, the development of tumors in the small intestines is significantly attenuated. In the transgenic small intestine tumors, the endogenous miR-145 is also enhanced and the expression of c-Myc and p68/p72, both of which have been reported to be pivotal for gut tumor development, is suppressed, corresponding to the downregulation of ERK5. We demonstrate that the combination of miR-143 and miR-145 inhibits the expression of c-Myc in human colon cancer cells, whereas miR-145 retards that of p72. Moreover, we show the possibilities that miR-145 modulates p72 expression through its 3' untranslated region and that c-Myc downregulation is involved in both p68 suppression and miR-145 induction. These findings suggest that forced expression of miR-143, probably interacting with endogenous miR-145, inhibits ERK5/c-Myc and p68/p72/β-catenin signaling and hampers small intestine tumor development in Apc(Min/+) mice. This unique cascade, in turn, may prevent overproduction of a subset of tumor suppressive miRNAs by repressing their own modulators, p68/p72.
    PLoS ONE 01/2012; 7(8):e42137. · 3.53 Impact Factor
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    Kinji Ohno, Mikako Ito, Masatoshi Ichihara, Masafumi Ito
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    ABSTRACT: Effects of molecular hydrogen on various diseases have been documented for 63 disease models and human diseases in the past four and a half years. Most studies have been performed on rodents including two models of Parkinson's disease and three models of Alzheimer's disease. Prominent effects are observed especially in oxidative stress-mediated diseases including neonatal cerebral hypoxia; Parkinson's disease; ischemia/reperfusion of spinal cord, heart, lung, liver, kidney, and intestine; transplantation of lung, heart, kidney, and intestine. Six human diseases have been studied to date: diabetes mellitus type 2, metabolic syndrome, hemodialysis, inflammatory and mitochondrial myopathies, brain stem infarction, and radiation-induced adverse effects. Two enigmas, however, remain to be solved. First, no dose-response effect is observed. Rodents and humans are able to take a small amount of hydrogen by drinking hydrogen-rich water, but marked effects are observed. Second, intestinal bacteria in humans and rodents produce a large amount of hydrogen, but an addition of a small amount of hydrogen exhibits marked effects. Further studies are required to elucidate molecular bases of prominent hydrogen effects and to determine the optimal frequency, amount, and method of hydrogen administration for each human disease.
    Oxidative Medicine and Cellular Longevity 01/2012; 2012:353152.
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    ABSTRACT: Glial cell line-derived neurotrophic factor (GDNF) is important for the development and maintenance of dopamine neurons (Lin et al. [1993] Science 260: 1130-1132). GDNF is neuroprotective in animal models of Parkinson disease, where dopamine neurons show selective degeneration. We previously reported GDNF-induced SPHK1 gene expression in a neuroblastoma cell line, TGW (Murakami et al. [2007] J Neurochem 102: 1585-1594). In the present study, we focused on the regulatory mechanism of GAP43 (GDNF-induced neuronal phenotype) transcription to further elucidate physiological roles of GDNF-induced SPHK1 expression and activity. Stable wild-type (SPHK1-WT) but not dominant-negative SPHK1 (SPHK1-DN) overexpression increased both control- and GDNF-induced GAP43 expression. SPHK1-WT cells showed enhanced GDNF-induced sphingosine 1-phosphate (S1P) secretion compared with mock- and SPHK1-DN cells. Exogenous S1P also increased GAP43 expression. In TGW cells, PD98059, a MEK inhibitor, but not SB203580 (a p38 MAPK inhibitor) and LY294002 (a PI3K inhibitor) inhibited GDNF-induced GAP43 expression, suggesting the MEK/ERK pathway has a major role in GDNF-induced GAP43 transcription. A G-protein-coupled receptor inhibitor, pertussis toxin, and S1P(1) and S1P(3) receptor antagonists (VPC23019 and CAY10444) also inhibited ERK activation. Moreover, both S1P1 and S1P3 were serine-phosphorylated by GDNF, suggesting their activated states. C/EBPβ transcription factor was induced by GDNF, and DNA pull-down and chromatin immunoprecipitation assays revealed the C/EBP binding site between -131 bp and -98  bp from the first exon of GAP43. Taken together, our results showed that in TGW cells, GDNF increased SPHK1 transcription, leading to the production and secretion of S1P. Through MEK/ERK pathway, S1P stimulates GAP43 transcription with increased binding of C/EBPβ to the 5'-promoter.
    Journal of Cellular Biochemistry 07/2011; 112(11):3449-58. · 3.06 Impact Factor
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    ABSTRACT: Molecular hydrogen has been reported to be effective for a variety of disorders and its effects have been ascribed to the reduction of oxidative stress. However, we have recently demonstrated that hydrogen inhibits type I allergy through modulating intracellular signal transduction. In the present study, we examined the hydrogen effects on lipopolysaccharide/interferon γ LPS/IFNγ-induced nitric oxide (NO) production in murine macrophage RAW264 cells. Treatment with hydrogen reduced LPS/IFNγ-induced NO release, which was associated with a diminished induction of inducible isoform of nitric oxide synthase (iNOS). Hydrogen treatment inhibited LPS/IFNγ-induced phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) and its downstream signaling molecules, p38 MAP kinase and JNK, as well as IκBα, but did not affect activation of NADPH oxidase and production of reactive oxygen species (ROS). As ROS is an upstream activator of ASK1, inhibition of ASK1 by hydrogen without suppressing ROS implies that a potential target molecule of hydrogen should be located at the receptor or immediately downstream of it. These results suggested a role for molecular hydrogen as a signal modulator. Finally, oral intake of hydrogen-rich water alleviated anti-type II collagen antibody-induced arthritis in mice, a model for human rheumatoid arthritis. Taken together, our studies indicate that hydrogen inhibits LPS/IFNγ-induced NO production through modulation of signal transduction in macrophages and ameliorates inflammatory arthritis in mice, providing the molecular basis for hydrogen effects on inflammation and a functional interaction between two gaseous signaling molecules, NO and molecular hydrogen.
    Biochemical and Biophysical Research Communications 06/2011; 411(1):143-9. · 2.28 Impact Factor
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    ABSTRACT: Ceramide is the central lipid in the sphingolipid metabolism. Ceramide kinase (CERK) and its product, ceramide 1-phosphate, have been implicated in various cellular functions. However, the regulatory mechanism of CERK gene expression remains to be determined. Here, we examined CERK mRNA level during all-trans retinoic acid (ATRA)-induced differentiation of a human neuroblastoma cell line, SH-SY5Y. ATRA reduced CERK mRNA and protein levels. Over-expression and small interfering RNA (siRNA) of CERK revealed that CERK is inhibitory against ATRA-induced neuronal differentiation and cell growth arrest. ATRA inhibited the transcriptional activity of 5'-promoter of CERK. Truncation and mutation study suggests that ATRA-responsible region was mainly located in the tandem retinoic acid responsive elements (RARE) between -40 bp and the first exon. The electrophoresis mobility shift assay revealed that ATRA produced two retarded bands, which were erased by antibody against chicken ovalbumin upstream promoter transcription factor I (COUP-TFI), RARalpha, and RXRalpha, respectively. DNA pull-down assay confirmed increased binding of these transcription factors to RARE. Transient expression of RAR, RXR, and COUP-TFI and siRNA transfection of these genes revealed that COUP-TFI inhibited CERK mRNA. Furthermore, chromatin immunoprecipitation assay showed the recruitment of co-repressors as well as three transcription factors. These results suggest that COUP-TFI was the ATRA-responsive suppressive transcription factor of CERK gene transcription.
    Journal of Neurochemistry 11/2009; 112(2):511-20. · 3.97 Impact Factor
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    ABSTRACT: Molecular hydrogen ameliorates oxidative stress-associated diseases in animal models. We found that oral intake of hydrogen-rich water abolishes an immediate-type allergic reaction in mice. Using rat RBL-2H3 mast cells, we demonstrated that hydrogen attenuates phosphorylation of the FcepsilonRI-associated Lyn and its downstream signal transduction, which subsequently inhibits the NADPH oxidase activity and reduces the generation of hydrogen peroxide. We also found that inhibition of NADPH oxidase attenuates phosphorylation of Lyn in mast cells, indicating the presence of a feed-forward loop that potentiates the allergic responses. Hydrogen accordingly inhibits all tested signaling molecule(s) in the loop. Hydrogen effects have been solely ascribed to exclusive removal of hydroxyl radical. In the immediate-type allergic reaction, hydrogen exerts its beneficial effect not by its radical scavenging activity but by modulating a specific signaling pathway. Effects of hydrogen in other diseases are possibly mediated by modulation of yet unidentified signaling pathways. Our studies also suggest that hydrogen is a gaseous signaling molecule like nitric oxide.
    Biochemical and Biophysical Research Communications 09/2009; 389(4):651-6. · 2.28 Impact Factor
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    ABSTRACT: Molecular hydrogen serves as an antioxidant that reduces hydroxyl radicals, but not the other reactive oxygen and nitrogen species. In the past year, molecular hydrogen has been reported to prevent or ameliorate eight diseases in rodents and one in human associated with oxidative stress. In Parkinson's disease, mitochondrial dysfunction and the associated oxidative stress are major causes of dopaminergic cell loss in the substantia nigra. We examined effects of approximately 50%-saturated molecular hydrogen in drinking water before or after the stereotactic surgery on 6-hydroxydopamine-induced nigrostrital degeneration in a rat model of Parkinson's disease. Methamphetamine-induced behavioral analysis showed that molecular hydrogen prevented both the development and progression of the nigrostrital degeneration. Tyrosine hydroxylase staining of the substantia nigra and striatum also demonstrated that pre- and post-treatment with hydrogen prevented the dopaminergic cell loss. Our studies suggest that hydrogen water is likely able to retard the development and progression of Parkinson's disease.
    Neuroscience Letters 05/2009; 453(2):81-5. · 2.03 Impact Factor
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    ABSTRACT: Intestinal ganglioneuromatosis (GN) is an uncommon disease of the enteric nervous system (ENS) and its pathogenesis remains unclear. Here we describe a unique case of diffuse GN of the intestinal wall associated with colon adenocarcinoma occurring in a 38-year-old female. Because it is well-known that glial cell line-derived neurotrophic factor (GDNF) and its receptor components, GDNF family receptor-alpha 1 (GFR-alpha 1) and RET receptor tyrosine kinase, play a crucial role in the development of ENS, their expression was analyzed by immunohistochemistry. Interestingly, GDNF as well as a related neurotrophic factor, neurturin (NTN), were expressed at high levels in adenocarcinoma cells whereas expression of GFR alpha 1 and RET was undetectable in them. In contrast, GFR-alpha 1 showed positive staining in both proliferating ganglion cells and glial cells, and RET immunoreactivity was found mainly in ganglion cell bodies. These findings suggested that GDNF and NTN expression in adenocarcinoma cells may play an important role in the pathogenesis of GN.
    Clinical neuropathology 01/2009; 28(2):105-12. · 1.34 Impact Factor
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    ABSTRACT: Germline mutations in the RET tyrosine kinase gene are responsible for the development of multiple endocrine neoplasia 2A and 2B (MEN2A and MEN2B). However, knowledge of the fundamental principles that determine the mutant RET-mediated signaling remains elusive. Here, we report increased expression of mitogen-activated protein kinase phosphatase-2 (MKP-2) in carcinomas developed in transgenic mice carrying RET with the MEN2A mutation (RET-MEN2A). The expression of MKP-2 was not only induced by RET-MEN2A or RET-MEN2B mutant proteins but also by the activation of endogenous RET by its ligand, glial cell line-derived neurotrophic factor (GDNF). MKP-2 expression was also evident in the MKK-f cell line, which was established from a mammary tumor developed in a RET-MEN2A transgenic mouse. Inhibition of MKP-2 attenuated the in vitro and in vivo proliferation of MKK-f cells, which was mediated by the suppression of cyclin B1 expression. Furthermore, we found that MKP-2 is highly expressed in medullary thyroid carcinomas derived from MEN2A patients. These findings suggest that the increased expression of MKP-2 may play a crucial role in oncogenic signaling downstream of mutant RET, leading to deregulation of cell cycle.
    Oncogene 07/2008; 27(43):5684-95. · 8.56 Impact Factor
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    ABSTRACT: The Krüppel-associated box (KRAB)-containing zinc finger proteins (ZFPs) comprise the largest family of zinc finger transcription factors that function as transcriptional repressors. In the study of glial cell line-derived neurotrophic factor (GDNF)-RET signaling, we have identified bone marrow zinc finger 3 (BMZF3), encoding a KRAB-ZFP, as a GDNF-inducible gene by differential display analysis. The expression of BMZF3 transcripts in the human neuroblastoma cell line TGW increased 1h after GDNF stimulation, as determined by Northern blotting and quantitative reverse-transcriptase polymerase chain reaction. The BMZF3 possesses transcriptional repressor activity in the KRAB domain. BMZF3 interacts with a co-repressor protein, KRAB-associated protein 1 (KAP-1), through the KRAB domain and siRNA-mediated knockdown of KAP-1 abolished the transcriptional repressor activity of BMZF3, indicating that KAP-1 is necessary for BMZF3 function. Furthermore, siRNA-mediated silencing of BMZF3 inhibited cell proliferation. These findings suggest that BMZF3 is a transcriptional repressor induced by GDNF that plays a role in cell proliferation.
    Biochemical and Biophysical Research Communications 03/2008; 366(1):226-32. · 2.28 Impact Factor
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    ABSTRACT: RET, the receptor of glial cell line-derived neurotrophic factor (GDNF) family ligands, is important for the development of kidney and peripheral neurons. GDNF promotes survival and differentiation of neurons. Mutation of RET leads to the constitutive signal activation causing papillary thyroid carcinoma and multiple endocrine neoplasia type 2 (MEN2). In this study, we report that GDNF/RET signaling up-regulates sphingosine kinase (SPHK) enzyme activity, SPHK1 protein and SPHK1 message in TGW human neuroblastoma cells. Silencing of SPHK1 using siRNA inhibited GDNF-induced neurite formation, GAP43 expression, and cell growth, suggesting the important role of SPHK1 in GDNF signal transduction. Furthermore, NIH3T3 cells transfected with MEN2A type mutated RET but not c-RET demonstrated the up-regulation of SPHK activity, SPHK1 protein and SPHK1 message compared with NIH3T3 cells. The cell growth and anchorage-independent colony formation of MEN2A-NIH3T3 was inhibited with siRNA of SPHK1, while no effect of scramble siRNA was observed. These results suggest the oncogenic role of SPHK1 in MEN2A type tumor. Promoter analysis showed that activator protein 2 and specificity protein 1 binding motif of the 5' promoter region of SPHK1 gene is important for its induction by GDNF. Furthermore, we demonstrated that ERK1/2 and PI3 kinase are involved in GDNF-induced SPHK1 transcription by using specific inhibitors.
    Journal of Neurochemistry 10/2007; 102(5):1585-94. · 3.97 Impact Factor

Publication Stats

1k Citations
315.10 Total Impact Points

Institutions

  • 2007–2014
    • Chubu University
      • • College of Life and Health Sciences
      • • Department of Biomedical Sciences
      Касугай, Aichi, Japan
  • 2001–2012
    • Nagoya University
      • • Center for Neural Diseases and Cancer
      • • Division of Pathology
      Nagoya-shi, Aichi-ken, Japan
  • 2011
    • National Center for Geriatrics and Gerontology
      • Department of Oral Disease Research
      Ōbu, Aichi-ken, Japan
  • 2009
    • Japan Society for the Promotion of Science
      Edo, Tōkyō, Japan
  • 1997
    • The University of Tokyo
      • Institute of Molecular and Cellular Biosciences
      Tokyo, Tokyo-to, Japan
  • 1995
    • Palo Alto Institute for Research and Education
      Palo Alto, California, United States