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Hadi S, Fan G, Hird A, Chow E. Disintegration of Symptom Clusters: Indicators of Response to Palliative Radiotherapy in Patients With Bone Metastases. Int J Radiat Oncol Biol Phys 2007. [DOI: 10.1016/j.ijrobp.2007.07.1839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Simmons MJ, Fan G, Zong WX, Degenhardt K, White E, Gélinas C. Bfl-1/A1 functions, similar to Mcl-1, as a selective tBid and Bak antagonist. Oncogene 2007; 27:1421-8. [PMID: 17724464 PMCID: PMC2880719 DOI: 10.1038/sj.onc.1210771] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The prosurvival Bcl-2-family member Bfl-1/A1 is a transcriptional target of nuclear factor-kappaB (NF-kappaB) that is overexpressed in many human tumors and is a means by which NF-kappaB inhibits apoptosis, but its mode of action is controversial. To better understand how Bfl-1 functions, we investigated its interaction with proapoptotic multidomain proteins Bax and Bak, and the BH3-only proteins Bid and tBid. We demonstrate that in living cells Bfl-1 selectively interacts with Bak and tBid, but not with Bax or Bid. Bfl-1/Bak interaction is functional as Bfl-1 suppressed staurosporine (STS)-induced apoptosis in wild-type and Bax-deficient cells, but not in Bak-/- cells. We also show that Bfl-1 blocks tumor necrosis factor-alpha (TNFalpha)-induced activation of Bax indirectly, via association with tBid. C-terminal deletion decreased Bfl-1's interaction with Bak and tBid and reduced its ability to suppress Bak- and tBid-mediated cell death. These data indicate that Bfl-1 utilizes different mechanisms to suppress apoptosis depending on the stimulus. Bfl-1 associates with tBid to prevent activation of proapoptotic Bax and Bak, and it also interacts directly with Bak to antagonize Bak-mediated cell death, similar to Mcl-1. Thus, part of the protective function of NF-kappaB is to induce Mcl-1-like activity by upregulating Bfl-1.
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Chow E, Harris K, Fan G, Tsao M, Sze W, Wu J. Meta-analysis of Palliative Radiotherapy Trials for Bone Metastases. Clin Oncol (R Coll Radiol) 2007. [DOI: 10.1016/j.clon.2007.01.346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Dutta J, Fan Y, Gupta N, Fan G, Gélinas C. Current insights into the regulation of programmed cell death by NF-kappaB. Oncogene 2006; 25:6800-16. [PMID: 17072329 DOI: 10.1038/sj.onc.1209938] [Citation(s) in RCA: 341] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The nuclear factor-kappaB (NF-kappaB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-kappaB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-kappaB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-kappaB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-kappaB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-kappaB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-kappaB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-kappaB in many disease conditions including tumor development, tumor progression and anticancer treatment.
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Malempati S, Tibbitts D, Cunningham M, Akkari Y, Olson S, Fan G, Sears RC. Aberrant stabilization of c-Myc protein in some lymphoblastic leukemias. Leukemia 2006; 20:1572-81. [PMID: 16855632 PMCID: PMC2322939 DOI: 10.1038/sj.leu.2404317] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 04/30/2006] [Accepted: 06/05/2006] [Indexed: 11/09/2022]
Abstract
Overexpression of the c-Myc oncoprotein is observed in a large number of hematopoietic malignancies, and transgenic animal models have revealed a potent role for c-Myc in the generation of leukemias and lymphomas. However, the reason for high c-Myc protein levels in most cases is unknown. We examined whether aberrant protein stabilization could be a mechanism of c-Myc overexpression in leukemia cell lines and in primary bone marrow samples from pediatric acute lymphoblastic leukemia (ALL) patients. We found that c-Myc protein half-life was prolonged in the majority of leukemia cell lines and bone marrow samples tested. There were no mutations in the c-myc gene in any of the leukemia cell lines that could account for increased c-Myc stability. However, abnormal phosphorylation at two conserved sites, Threonine 58 and Serine 62, was observed in leukemia cell lines with stabilized c-Myc. Moreover, stabilized c-Myc from the ALL cell lines showed decreased affinity for glycogen synthase kinase3beta, the kinase that phosphorylates c-Myc at Threonine 58 and facilitates its degradation. These findings reveal that deregulation of the c-Myc degradation pathway controlled by Serine 62 and Threonine 58 phosphorylation is a novel mechanism for increased expression of a potent oncoprotein known to be involved in hematopoietic malignancies.
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Barnes E, Librach L, Chow E, Harris K, Fan G, Tsao M, Barbera L, Danjoux C. 25 Involvement of family physicians in the care of patients receiving palliative radiotherapy. Radiother Oncol 2006. [DOI: 10.1016/s0167-8140(06)80766-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Fan G, Sinclair E, Christakis M, Erhlich L, Zubovits J, Chow E. Solitary bone metastasis beneath the shoulder shield: coincidence or cause? Curr Oncol 2006; 13:121-3. [PMID: 17576452 PMCID: PMC1891183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Post-mastectomy radiotherapy has been demonstrated to improve locoregional control in breast cancer patients. We report a case involving a 44-year-old breast cancer patient who presented with a solitary bone metastasis in the area beneath the shoulder shield, likely from a coincidental recurrence.
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Fan G, Sinclair E, Christakis M, Erhlich L, Zubovits J, Chow E. Solitary Bone Metastasis beneath the Shoulder Shield: Coincidence or Cause? Curr Oncol 2006. [DOI: 10.3747/co.v13i4.98] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Post-mastectomy radiotherapy has been demonstrated to improve locoregional control in breast cancer patients. We report a case involving a 44-year-old breast cancer patient who presented with a solitary bone metastasis in the area beneath the shoulder shield, likely from a coincidental recurrence.
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Thaker A, Hutnick L, Fan G. Dna Hypomethylation and Neuronal Survival. J Investig Med 2006. [DOI: 10.1177/108155890605401s04] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Thaker A, Hutnick L, Fan G. 120 DNA HYPOMETHYLATION AND NEURONAL SURVIVAL. J Investig Med 2006. [DOI: 10.2310/6650.2005.x0004.119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Ho A, Atencio D, Fan G, Green S, Formenti S, Haffty B, Bernstein J, Iyengar P, Stock R, Cesaretti J, Rosenstein B. ATM Sequence Variants as Predictors for Late Normal Tissue Responses in Breast Cancer Patients Treated with Radiotherapy. Int J Radiat Oncol Biol Phys 2005. [DOI: 10.1016/j.ijrobp.2005.07.779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Fan G, Ma X, Wong PY, Rodrigues CMP, Steer CJ. p53 dephosphorylation and p21(Cip1/Waf1) translocation correlate with caspase-3 activation in TGF-beta1-induced apoptosis of HuH-7 cells. Apoptosis 2005; 9:211-21. [PMID: 15004518 DOI: 10.1023/b:appt.0000018803.11260.02] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The p53 tumor suppressor gene product plays an important role in the regulation of apoptosis. Transforming growth factor beta1 (TGF-beta1)-induced apoptosis in hepatic cells is associated with reduced expression of the retinoblastoma protein (pRb) and subsequent E2F-1-activated expression of apoptosis-related genes. In this study, we explored the potential role of p53 in TGF-beta1-induced apoptosis. HuH-7 human hepatoma cells were either synchronized in G1, S and G2/M phases, or treated with 1 nM TGF-beta1. The results indicated that greater than 90% of the TGF-beta1-treated cells were arrested in G1 phase of the cell cycle. This was associated with enhanced p53 dephosphorylation and p21(Cip1/Waf1) expression, which coincided with decreased Cdk2, Cdk4, and cyclin E expression, compared with synchronized G1 cells. In addition, p53 dephosphorylation coincided with caspase-3 activation, and translocation of p21(Cip1/Waf1) and p27(Kip1) into the cytoplasm, all of which were suppressed by caspase inhibition of TGF-beta1-induced apoptosis. Finally, phosphatase inhibition and pRb overexpression partially inhibited p53-mediated apoptosis. In conclusion, the results demonstrated that TGF-beta1-induced p53 dephosphorylation is associated with caspase-3 activation, and cytosolic translocation of p21(Cip1/Waf1) and p27(Kip1), resulting in decreased expression of Cdks and cyclins. Further, p53 appears to mediate TGF-beta1-induced apoptosis downstream of the pRb/E2F-1 pathway.
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Fan G, Sun B, Wu Z, Guo Q, Guo Y. In vivo single-voxel proton MR spectroscopy in the differentiation of high-grade gliomas and solitary metastases. Clin Radiol 2004; 59:77-85. [PMID: 14697379 DOI: 10.1016/j.crad.2003.08.006] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
AIM To determine whether single-voxel proton magnetic resonance spectroscopy (1HMRS) could be used to differentiate gliomas from metastases on the basis of differences in metabolite levels in the different involved regions. MATERIALS AND METHODS Twenty-two patients (age range from 32 to 62 years, with a median age of 46.7 years) with a solitary brain tumour (14 gliomas, eight metastases) underwent conventional, gadolinium-DTPA enhanced T1-weighted images, and 1HMRS before surgical resection. Spectra from the enhancing tumour, the peritumoural region, and normal brain were obtained from 1HMRS. A point resolved spectroscopy sequence was required for 1HMRS. The metabolites in the spectra include: N-acetylaspartate (NAA), choline (CHO), creatine compounds (CR), myo-inositol (MI), lactate (LAC), glutamate and glutamine (Glu-n). Relative concentrations of metabolites were related to the peak area, and expressed with reference to CR. Student's t-test was used to determine whether there was a statistically significant difference in relative metabolic ratios between high-grade gliomas and metastases. Meanwhile, 16 of all 22 patients were re-examined using magnetic resonance imaging (MRI) within 6 months of surgical resection. Recurrence was present in three patients (two gliomas, one metastasis). RESULTS Of the 14 patients with gliomas, the peaks of NAA were reduced in three cases; the peaks of LAC, which were elevated, appeared as typical double-peaks in the peritumoural region in nine cases; the peaks of Glu-n, which were also elevated, had a zigzag appearance in seven cases. The peaks of MI were increased in the tumoural region in eight cases, and CHO levels were elevated in all 14 cases. Of the eight patients with metastases, Glu-n peaks in the tumoural region in three cases and CHO peaks in the tumoural region in four cases were elevated, respectively, while the peaks of CR were reduced in three cases, and the peaks of NAA were markedly reduced in four cases within the enhancing tumoural region. Elevated CHO levels (CHO-to-CR ratio was 4.98:1.46, 2.65:0.32) in both the tumoural and peritumoural regions of gliomas but not in the metastases (CHO-to-CR ratio was 1.37:0.92, 1.22:0.38), and elevated MI levels were present (MI-to-CR ratio was 1.67:0.35) within the enhancing foci of gliomas but not in the metastases (MI-to-CR ratio was 0.89:0.31). The difference was statistically significant (p<0.01). Elevated Glu-n and lipid levels were present in all three patients with recurrences. CONCLUSION 1HMRS is a useful method in the distinction of these two kinds of tumours. It may also may provide useful prognostic information.
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Abstract
The retinoblastoma gene and its protein product (Rb) have been studied intensively for their role in development, oncogenesis, cell growth, differentiation and cell cycle regulation. In addition, Rb appears to be a key factor in protecting cells from apoptosis. It is likely that Rb plays an essential role in cell survival by regulating the activity of multiple apoptotic mediators. Rb expression as a nuclear phosphoprotein is essential for normal cell cycle function. Clearly, any damage to the cell cycle or to DNA integrity is a potent trigger of apoptosis and Rb involvement. The E2F transcription factor is a critical component in the Rb-dependent apoptotic pathway(s), and can act either in concert or independently of the p53 tumour suppressor. Until recently, it was suggested that Rb, E2F and p53 modulate the apoptotic threshold by acting upstream of certain death proteases involved in programmed cell death. However, Rb activity can also be regulated downstream by the interleukin-converting enzyme-like (ICE-like) proteases, which abolish Rb activity by cleavage of aspartate-enriched regions within its C-terminus. Finally, Bcl-2, which inhibits multiple-factorial-induced apoptosis, does so, in part, by modulating the phosphorylation state of Rb. Taken together, Rb acts not only as a tumour suppressor protein which controls cell cycle function, but also determines the final destiny of a cell through apoptosis.
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Fan G, Jaenisch R, Kucera J. Corrigendum to “a role for p75 receptor in neurotrophin-3 functioning during the development of limb proprioception”. Neuroscience 2003. [DOI: 10.1016/s0306-4522(02)00914-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fan G, Siniaia M, Poon CS, Jaenisch R. Effect of DNA hypomethylation on neural control of respiration: a genetic model. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 499:195-200. [PMID: 11729877 DOI: 10.1007/978-1-4615-1375-9_30] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Endres M, Fan G, Meisel A, Dirnagl U, Jaenisch R. Effects of cerebral ischemia in mice lacking DNA methyltransferase 1 in post-mitotic neurons. Neuroreport 2001; 12:3763-6. [PMID: 11726790 DOI: 10.1097/00001756-200112040-00032] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
DNA methylation is important for controlling gene expression and is catalyzed by DNA methyltransferase (Dnmt1) an enzyme abundant in brain. We recently demonstrated that mice expressing reduced levels of Dnmt1 are protected from cerebral ischemia. Here, we used the cre/loxP system to produce conditional mutants that lack Dnmt 1 in postmitotic neurons of the postnatal brain. We demonstrate that animals heterozygous for the conditional allele (Dnmt11lox/+) have significantly smaller infarcts following 1 h middle cerebral artery occlusion/reperfusion compared to their wildtype litters. Surprisingly, mice with a deletion of Dnmt1 in post-mitotic neurons (Dnmt11lox/c) were not protected. In conclusion, we demonstrate that reduced levels of Dnmt1, but not its absence, in post-mitotic neurons protect from ischemic brain injury.
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Li Y, Xing G, Wang Q, Li M, Wei H, Fan G, Chen J, Yang X, Wu C, Chen H, He F. Hepatopoietin acts as an autocrine growth factor in hepatoma cells. DNA Cell Biol 2001; 20:791-5. [PMID: 11879572 DOI: 10.1089/104454901753438606] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Hepatopoietin (HPO) is a novel human hepatotrophic factor. Its known function is mainly limited to supporting liver regeneration. Recently, it was shown by our laboratory that HPO acts as a mitogen for hepatoma cell lines and that there are HPO-specific receptors on the surface of these cells (Wang, G., et al., J Biol Chem 1999;274:11469-11472), indicating that HPO might be involved in oncogenesis in the liver. To study this hypothesis, we first conducted experiments in vitro to identify the existence of an autocrine loop of HPO/HPO receptor in hepatoma cell lines. It was demonstrated that HPO was actually expressed by hepatoma cells, such as HepG2, Bel 7402, and SMMC-7721, and secreted into the culture medium. Furthermore, it was shown that HPO-neutralizing antibody has an inhibitory effect on the uptake of tritiated thymidine by hepatoma cells. The results strongly suggest that HPO acts as an autocrine factor for hepatoma cells in vitro.
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Rios M, Fan G, Fekete C, Kelly J, Bates B, Kuehn R, Lechan RM, Jaenisch R. Conditional deletion of brain-derived neurotrophic factor in the postnatal brain leads to obesity and hyperactivity. Mol Endocrinol 2001; 15:1748-57. [PMID: 11579207 DOI: 10.1210/mend.15.10.0706] [Citation(s) in RCA: 499] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Brain-derived neurotrophic factor has been associated previously with the regulation of food intake. To help elucidate the role of this neurotrophin in weight regulation, we have generated conditional mutants in which brain-derived neurotrophic factor has been eliminated from the brain after birth through the use of the cre-loxP recombination system. Brain-derived neurotrophic factor conditional mutants were hyperactive after exposure to stressors and had higher levels of anxiety when evaluated in the light/dark exploration test. They also had mature onset obesity characterized by a dramatic 80-150% increase in body weight, increased linear growth, and elevated serum levels of leptin, insulin, glucose, and cholesterol. In addition, the mutants had an abnormal starvation response and elevated basal levels of POMC, an anorexigenic factor and the precursor for alpha-MSH. Our results demonstrate that brain derived neurotrophic factor has an essential maintenance function in the regulation of anxiety-related behavior and in food intake through central mediators in both the basal and fasted state.
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Fan G, Mar W, Park MK, Choi EW, Kim K, Kim S. A novel class of inhibitors for steroid 5alpha-reductase: synthesis and evaluation of umbelliferone derivatives. Bioorg Med Chem Lett 2001; 11:2361-3. [PMID: 11527731 DOI: 10.1016/s0960-894x(01)00429-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A series of umbelliferone derivatives was prepared and their 5alpha-reductase type 1 inhibitory activities were evaluated in cell culture systems. Our studies have identified a new series of potent 5alpha-reductase type 1 inhibitors and provided the basis for further development for the treatment of human endocrine disorders associated with overproduction of DHT by 5alpha-reductase type 1. The preliminary structure-activity relationship was described to elucidate the essential structural requirements.
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Akbarian S, Bates B, Liu RJ, Skirboll SL, Pejchal T, Coppola V, Sun LD, Fan G, Kucera J, Wilson MA, Tessarollo L, Kosofsky BE, Taylor JR, Bothwell M, Nestler EJ, Aghajanian GK, Jaenisch R. Neurotrophin-3 modulates noradrenergic neuron function and opiate withdrawal. Mol Psychiatry 2001; 6:593-604. [PMID: 11526474 DOI: 10.1038/sj.mp.4000897] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2000] [Revised: 02/02/2001] [Accepted: 02/02/2001] [Indexed: 11/08/2022]
Abstract
Somatic symptoms and aversion of opiate withdrawal, regulated by noradrenergic signaling, were attenuated in mice with a CNS-wide conditional ablation of neurotrophin-3. This occurred in conjunction with altered cAMP-mediated excitation and reduced upregulation of tyrosine hydroxylase in A6 (locus coeruleus) without loss of neurons. Transgene-derived NT-3 expressed by noradrenergic neurons of conditional mutants restored opiate withdrawal symptoms. Endogenous NT-3 expression, strikingly absent in noradrenergic neurons of postnatal and adult brain, is present in afferent sources of the dorsal medulla and is upregulated after chronic morphine exposure in noradrenergic projection areas of the ventral forebrain. NT-3 expressed by non-catecholaminergic neurons may modulate opiate withdrawal and noradrenergic signalling.
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Lei L, Fan G, Wang R, Han D, Yang W, Wu Z. [Effect of p14ARF gene on cell growth of human laryngeal tumor cells and expression of endogenous p53 protein]. ZHONGHUA ER BI YAN HOU KE ZA ZHI 2001; 36:135-7. [PMID: 12761983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
OBJECTIVE To explore the inhibitory effect of p14ARF on the cell growth of laryngeal carcinoma and the expression on endogenous p53. METHODS p14ARF cDNA was transferred to the cell line Hep-2 of squamous cell carcinoma of the larynx by gene transfer to study the cell cycles and the expression of endogenous wild type p53 using flow cytometry, polymerase chain reaction(PCR) and Western-Blotting. RESULTS Expression of p14ARF significantly affected the Hep-2 cell growth. The clone-forming efficiency of the Hep-2 cells transferred with p14ARF was 57%, compared with empty vector pcDNA3. The number of 48 hours after transfer with p14ARF cDNA at both G0/G1 and G2/M was two fold as the control. The expression of endogenous wild type p53 was significantly enhanced. CONCLUSION Expression of p14ARF can up-regulate the expression of endogenous wild type p53 and inhibit the Hep-2 cell growth of human laryngeal squamous cell carcinoma at both G0/G1 and G2/M.
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Sun Y, Nadal-Vicens M, Misono S, Lin MZ, Zubiaga A, Hua X, Fan G, Greenberg ME. Neurogenin promotes neurogenesis and inhibits glial differentiation by independent mechanisms. Cell 2001; 104:365-76. [PMID: 11239394 DOI: 10.1016/s0092-8674(01)00224-0] [Citation(s) in RCA: 585] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The mechanisms by which neural stem cells give rise to neurons, astrocytes, or oligodendrocytes are beginning to be elucidated. However, it is not known how the specification of one cell lineage results in the suppression of alternative fates. We find that in addition to inducing neurogenesis, the bHLH transcription factor neurogenin (Ngn1) inhibits the differentiation of neural stem cells into astrocytes. While Ngn1 promotes neurogenesis by functioning as a transcriptional activator, Ngn1 inhibits astrocyte differentiation by sequestering the CBP-Smad1 transcription complex away from astrocyte differentiation genes, and by inhibiting the activation of STAT transcription factors that are necessary for gliogenesis. Thus, two distinct mechanisms are involved in the activation and suppression of gene expression during cell-fate specification by neurogenin.
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Fan G, Beard C, Chen RZ, Csankovszki G, Sun Y, Siniaia M, Biniszkiewicz D, Bates B, Lee PP, Kuhn R, Trumpp A, Poon C, Wilson CB, Jaenisch R. DNA hypomethylation perturbs the function and survival of CNS neurons in postnatal animals. J Neurosci 2001; 21:788-97. [PMID: 11157065 PMCID: PMC6762314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2000] [Revised: 10/30/2000] [Accepted: 11/02/2000] [Indexed: 02/18/2023] Open
Abstract
DNA methyltransferase I (Dnmt1), the maintenance enzyme for DNA cytosine methylation, is expressed at high levels in the CNS during embryogenesis and after birth. Because embryos deficient for Dnmt1 die at gastrulation, the role of Dnmt1 in the development and function of the nervous system could not be studied by using this mutation. We therefore used the cre/loxP system to produce conditional mutants that lack Dnmt1 in neuroblasts of embryonic day 12 embryos or in postmitotic neurons of the postnatal animal. Conditional deletion of the Dnmt1 gene resulted in rapid depletion of Dnmt1 proteins, indicating that the enzyme in postmitotic neurons turns over quickly. Dnmt1 deficiency in postmitotic neurons neither affected levels of global DNA methylation nor influenced cell survival during postnatal life. In contrast, Dnmt1 deficiency in mitotic CNS precursor cells resulted in DNA hypomethylation in daughter cells. Whereas mutant embryos carrying 95% hypomethylated cells in the brain died immediately after birth because of respiratory distress, mosaic animals with 30% hypomethylated CNS cells were viable into adulthood. However, these mutant cells were eliminated quickly from the brain within 3 weeks of postnatal life. Thus, hypomethylated CNS neurons were impaired functionally and were selected against at postnatal stages.
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Li Y, Li M, Xing G, Hu Z, Wang Q, Dong C, Wei H, Fan G, Chen J, Yang X, Zhao S, Chen H, Guan K, Wu C, Zhang C, He F. Stimulation of the mitogen-activated protein kinase cascade and tyrosine phosphorylation of the epidermal growth factor receptor by hepatopoietin. J Biol Chem 2000; 275:37443-7. [PMID: 10982794 DOI: 10.1074/jbc.m004373200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hepatopoietin (HPO) is a novel human hepatotrophic growth factor, which specifically stimulates proliferation of cultured primary hepatocytes in vitro and liver regeneration after liver partial hepatectomy in vivo. Recently, the identification of the mitogenic effect of HPO on hepatoma cell lines and the existence of HPO-specific receptors indicate that HPO acts via its specific cell surface receptor. However, the molecular mechanism of HPO action is not fully elucidated. In this report, we examined the signal transduction events induced by HPO in hepatoma cell line (HepG2). Our results demonstrated that HPO induces phosphorylation of mitogen-activated protein kinase kinase and mitogen-activated protein kinase (MAPK) in a rapid and transient manner. HPO stimulates tyrosine phosphorylation of epidermal growth factor receptor (EGFR). Furthermore, we observed that both MAPK activation and the mitogenic effect of HPO on HepG2 cells were completely blocked by AG1478, a specific inhibitor of EGFR tyrosine kinase activity. However, the effects of HPO were not antagonized by an EGFR-blocking antibody, mAb528, which blocks the interaction between epidermal growth factor and EGFR, indicating that stimulation of tyrosine phosphorylation of EGFR by HPO was not mediated by epidermal growth factor. In contrast, genistein, a general tyrosine kinase inhibitor, significantly attenuated the tyrosine phosphorylation of EGFR in response to HPO. In conclusion, our results suggest that tyrosine phosphorylation of EGFR may play a critical role in MAPK activation and mitogenic stimulation by HPO.
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