Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epigenetic mechanisms may be the main driving force for critical changes in gene expression that are responsible for progression of prostate cancers. The three most extensively characterized mechanisms for epigenetic gene-regulation are (i) changing patterns of DNA methylation, (ii) histone acetylations/deacetylations, and (iii) alterations in regulatory feedback loops for growth factors. Several studies have indicated that DNA hypermethylation is an important mechanism in prostate cancer for inactivation of key regulatory genes such as E-cadherin, pi-class glutathione S-transferase, the tumor suppressors CDKN2 and PTEN, and IGF-II. Similarly, histone acetylations and deacetylations are frequently associated respectively with transcriptional activation (e.g. IGFBP-2 and p21) and repression (e.g. Mad:Max dimers) of genes linked to prostate cancer progression. Recently, histone acetyltransferase and deacetylase activities have been shown to be intrinsic with transcriptional coregulator proteins that bind to steroid receptors (e.g. SRC-1 and PCAF). Changes in regulatory feedback loops for growth factors with prostate cancer progression tend toward shifts from paracrine to autocrine control where the receptor and ligand are produced by the same cell. While there are several examples of this progression pattern in prostate tumors such as with IGF, FGF, TGF-alpha and their respective receptors, the precise mechanism (i.e. epigenetic or mutational) is less certain. In the context of treatment options, the contribution of mutational versus epigenetic events to prostate cancer progression is an important consideration. Irreversible genetic changes are likely to be less amenable to therapeutic control than are epigenetic ones.
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PMID:Epigenetic mechanisms for progression of prostate cancer. 1045 84

The tumor suppressor gene PTEN/MMAC-1/TEP-1 (referred to hereafter as PTEN) maps to chromosome 10q23 and encodes a dual specificity phosphatase. The PTEN protein negatively regulates cell migration and cell survival and induces a G1 cell cycle block via negative regulation of the phosphatidylinositol 3'-kinase/protein kinase B/Akt signaling pathway. PTEN is frequently mutated or deleted in both prostate cancer cell lines and primary prostate cancers. A murine polyclonal antiserum was raised against a glutathione S-transferase fusion polypeptide of the COOH terninus of PTEN. Archival paraffin tissue sections from 109 cases of resected prostate cancer were immunostained with the antiserum, using DU145 and PC-3 cells as positive and negative controls, respectively. PTEN expression was seen in the secretory cells. Cases were considered positive when granular cytoplasmic staining was seen in all tumor cells, mixed when areas of both positive and negative tumor cell clones were seen, and negative when adjacent benign prostate tissue but not tumor tissue showed positive staining. Seventeen cases (15.6%) of prostate cancer were positive, 70 cases (64.2%) were mixed, and 22 cases (20.2%) were negative. Total absence of PTEN expression correlated with the Gleason score (P = 0.0081) and correlated more significantly with a Gleason score of 7 or higher (P = 0.0004) and with advanced pathological stage (American Joint Committee on Cancer stages T3b and T4; P = 0.0078). Thus, loss of PTEN protein is correlated with pathological markers of poor prognosis in prostate cancer.
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PMID:Loss of PTEN expression in paraffin-embedded primary prostate cancer correlates with high Gleason score and advanced stage. 1048 74

PTEN/MMAC1 (phosphatase and tensin homolog/mutated in multiple advanced cancers 1) is a tumor suppressor gene, the inactivation of which is an important step in the progression of gliomas to end-stage glioblastoma multiforme. We examined the distribution of PTEN protein in 49 primary human gliomas by immunocytochemistry using polyclonal antibodies that we raised against PTEN-glutathione S-transferase fusion proteins expressed in Escherichia coli. The study group consisted of 6 low-grade astrocytomas, 7 anaplastic astrocytomas, 21 glioblastomas multiforme, 4 low-grade oligodendrogliomas, 6 malignant oligodendrogliomas, and 5 malignant mixed oligoastrocytomas. For each tumor, we determined the percentage of tumor cells showing PTEN immunoreactivity in the most cellular regions of the tumor specimen. In both astrocytomas and oligodendrogliomas, there was an inverse relationship between the percentage of PTEN+ cells and malignancy grade, consistent with a role for PTEN as a tumor suppressor gene, the expression of which declines during glioma progression. In nonneoplastic tissue, PTEN was expressed in human fetal brain at 16, 23, and 27 weeks' gestation, but not in adult brain, indicating that PTEN is developmentally regulated in the CNS. In 21 glioblastomas multiforme, we correlated PTEN protein expression with PTEN gene sequence. Although PTEN-mutant tumors showed significantly diminished PTEN protein expression compared with wild-type cases, suppressed expression of PTEN is more prevalent than predicted from mutation frequencies.
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PMID:Immunocytochemical mapping of the phosphatase and tensin homolog (PTEN/MMAC1) tumor suppressor protein in human gliomas. 1130 23

Expression of enzymatically active mammalian proteins in Escherichia coli can proven to be a challenging task due to poor solubility, improper folding, and lack of adequate posttranslational modification. Expression of mammalian proteins using baculovirus or yeast systems is time-consuming and may also be subject to inadequate modification. In order to overcome these technical difficulties, we have developed a mammalian expression system for the convenient subcloning of cDNA fragments, high-level expression, and one-step purification of enzymatically active proteins. The mammalian expression vector pEBG that expresses glutathione S-transferase fusion proteins was modified to create an SrfI restriction site in the multiple cloning site. The protein coding sequences of MAP kinase phosphatase-1 (MKP-1), MAP kinase phosphatase-2 (MKP-2), and the tumor suppressor PTEN were PCR-amplified using Pfu DNA polymerase and cloned into the SrfI site through SrfI digestion-coupled ligation. The resulting plasmids were transiently transfected into 293T cells using FuGENE 6 transfection reagent. Forty eight hours after transfection, cells were harvested and bioactive recombinant proteins were purified by glutathione-Sepharose beads. Protein yield, which ranged from 200 to 700 microg, was more than adequate for biochemical studies. The usefulness of this versatile system for studying protein function and its potential application for proteomics research are discussed.
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PMID:A mammalian expression system for rapid production and purification of active MAP kinase phosphatases. 1192 65

We previously reported (Rani, M. R., Asthagiri, A. R., Singh, A., Sizemore, N., Sathe, S. S., Li, X., DiDonato, J. D., Stark, G. R., and Ransohoff, R. M. (2001) J. Biol. Chem. 276, 44365-44368) that IFN-beta induction of beta-R1 in fibrosarcoma cells required transcription factors ISGF-3 and NF-kappa B. IFN-beta treatment did not augment the abundance of NF-kappa B, but led to phosphorylation of the NF-kappa B subunit p65 and induced a nuclear activity capable of phosphorylating a p65-GST fusion construct in the carboxy-terminal transactivation domain (TAD), residues 354-551. We now present evidence for the involvement of phosphoinositide 3-kinase (PI3K) in this pathway. Pretreatment of HT1080-derived fibrosarcoma cells with pharmacological inhibitors of PI3K (wortmannin or LY294002) selectively inhibited IFN-beta-induced beta-R1 mRNA accumulation in a dose-dependent manner. In stably transfected cell lines, bovine p85, the regulatory subunit of PI3K, functioned as a dominant-negative inhibitor of interferon (IFN) signaling via PI3K and selectively suppressed IFN-beta-mediated induction of beta-R1. Overexpression of PTEN (phosphatase and tensin homologue mutated on chromosome ten), an antagonist of PI3K, blocked induction of a beta-R1 promoter-reporter construct. Studies with PTEN mutants suggested that the lipid kinase activity of PI3K was essential for IFN-beta-induced transcription of beta-R1. Consistent with this finding, a dominant-negative mutant of the serine-threonine kinase Akt, a downstream effector of PI3K, selectively blocked IFN-beta-mediated induction of the beta-R1 promoter reporter. Furthermore, IFN-beta-mediated phosphorylation of GST-p65 was blocked by pretreatment with LY294002. These data suggest that IFN-beta acts through PI3K to enhance the transactivation competence of NF-kappa B complexes through phosphorylation of p65 within the TAD. The results provide novel insight into the role of PI3K in the transcriptional response to IFN-beta.
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PMID:Requirement of phosphoinositide 3-kinase and Akt for interferon-beta-mediated induction of the beta-R1 (SCYB11) gene. 1216 89

PtdIns(3,4) P (2), a breakdown product of the lipid second messenger PtdIns(3,4,5) P (3), is a key signalling molecule in pathways controlling various cellular events. Cellular levels of PtdIns(3,4) P (2) are elevated upon agonist stimulation, mediating downstream signalling pathways by recruiting proteins containing specialized lipid-binding modules, such as the pleckstrin homology (PH) domain. A recently identified protein, TAPP1 (tandem-PH-domain-containing protein 1), has been shown to interact in vitro with high affinity and specificity with PtdIns(3,4) P (2) through its C-terminal PH domain. In the present study, we have utilized this PH domain tagged with glutathione S-transferase (GST-TAPP1-PH) as a probe in an on-section immunoelectron microscopy labelling procedure, mapping the subcellular distribution of PtdIns(3,4) P (2). As expected, we found accumulation of PtdIns(3,4) P (2) at the plasma membrane in response to the agonists platelet-derived growth factor and hydrogen peroxide. Importantly, however, we also found agonist stimulated PtdIns(3,4) P (2) labelling of intracellular organelles, including the endoplasmic reticulum and multivesicular endosomes. Expression of the 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10) in PTEN-null U87MG cells revealed differential sensitivity of these lipid pools to the enzyme. These data suggest a role for PtdIns(3,4) P (2) in endomembrane function.
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PMID:Detection of novel intracellular agonist responsive pools of phosphatidylinositol 3,4-bisphosphate using the TAPP1 pleckstrin homology domain in immunoelectron microscopy. 1460 33

The Forkhead Box (Fox) proteins are an extensive family of transcription factors that shares homology in the winged helix DNA binding domain. Liver regeneration studies with the -3 kb transthyretin (TTR) promoter-driven FoxM1B transgenic (TG) mice demonstrated that premature hepatocyte nuclear localization of the FoxM1B transgene protein at 16 h following partial hepatectomy (PHx) caused an 8-h acceleration in the onset of hepatocyte DNA replication (S-phase) and mitosis by stimulating earlier expression of cell cycle genes. Whether the FoxM1B transgene protein participates in immediate early events during liver regeneration remains to be determined. Here, we found that the FoxM1B transgene protein translocated to hepatocyte nuclei immediately following PHx, that its nuclear staining persisted for the first 6 h after surgery, and that this translocation was associated with an increase in size of regenerating TG hepatocytes. However, regenerating TTR-FoxM1B liver did not exhibit altered expression of proteins that have been implicated in mediating increased cell size, including serum-and-gucocorticoid-inducible protein kinase (SGK), protein kinase-B/Akt, the tumor suppresser gene PTEN (negative regulator of the PI3K/Akt pathway), c-Myc, or peroxisome proliferation. Moreover, we demonstrated that hepatocyte nuclear translocation of the FoxM1B transgene protein was rapidly induced during the hepatic acute phase response, which occurs during the immediate early stages of liver regeneration. Analysis of cDNA expression arrays identified a number of genes such as immediate early transcription factors (ID-3, Stat3, Nur77), matrix metalloproteinase-9 (MMP-9), and several glutathione S-transferase (GST) isoforms and stress response genes, whose expression is elevated in regenerating TTR-FoxM1B TG livers compared with regenerating wild-type (WT) liver. These liver regeneration studies demonstrate that hepatocyte nuclear translocation of the FoxM1B transgene protein was sustained for the first 6 h after PHx, and was associated with transient hypertrophy of regenerating TG hepatocytes and increased expression of genes that may enhance hepatocyte proliferation.
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PMID:Rapid hepatocyte nuclear translocation of the Forkhead Box M1B (FoxM1B) transcription factor caused a transient increase in size of regenerating transgenic hepatocytes. 1468 88

We examined the impact of purified bacterially synthesized GST-MDA-7 (IL-24) and ionizing radiation on the proliferation and survival of nonestablished human glioblastoma multiforme (GBM) cells. Glioma cell types expressing mutated PTEN and p53 molecules, activated ERBB1VIII, overexpressing wild type ERBB1 or without receptor overexpression were selected. In MTT assays, GST-MDA-7 caused a dose-dependent reduction in the proliferation of nonestablished glioma cells; however only at higher concentrations did GST-MDA-7 reduce cell viability. The anti-proliferative and cytotoxic effects of GST-MDA-7 were enhanced by radiation in a greater than additive fashion that correlated with JNK1/2/3 activation. The reduction in cell growth and enhancement in cell killing by the combination of GST-MDA-7 and radiation were blocked by an ROS scavenger, N-acetyl cysteine (NAC), a JNK1/2/3 inhibitor SP600125, a pan-caspase inhibitor (zVAD) and by an inhibitor of caspase 9 (LEHD), but not by an inhibitor of caspase 8 (IETD). Low concentrations of either GST-MDA-7 or radiation reduced clonogenic survival, however colony formation ability was significantly further decreased when the two treatments were combined, which was also blocked by inhibition of caspase 9 function. In general agreement with activation of the intrinsic caspase pathway, cell death correlated with reduced BCL-XL expression and with increased levels of the pro-apoptotic proteins BAD and BAX. Inhibition of caspase 9 after combination treatment blunted neither JNK1/2/3 activation nor the enhanced expression of BAD and BAX, but did block caspase 3 cleavage, reduced expression of BCL-XL and inhibition of ERK1/2 activity. In contrast, incubation with NAC blocked JNK1/2/3 activation and cell killing, but not the increases in BAD and BAX expression. These findings argue that after combination treatment JNK1/2/3 activation is a primary pro-apoptotic event and loss of BCL-XL expression and ERK1/2 activity are secondary caspase-dependent processes. This data also argues that GST- MDA-7 induces two parallel pro-apoptotic pathways via ROS-dependent and -independent mechanisms. Infection of primary human astrocytes with a recombinant adenovirus to express MDA-7, Ad.mda-7, but not infection with either Ad.cmv or Ad.mda-7SP- lacking MDA-7 secretion, resulted in the suppression of GBM cell colony formation in soft agar overlay assays, an effect that was enhanced in a greater than additive fashion by radiation. Collectively, our findings demonstrate that MDA-7 reduces proliferation and enhances the radiosensitivity of nonestablished human GBM cells in vitro, and when grown in 3 dimensions, and that sensitization occurs independently of basal EGFR/ERK1/2/AKT activity or the functions of PTEN and p53.
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PMID:MDA-7 regulates cell growth and radiosensitivity in vitro of primary (non-established) human glioma cells. 1532 89

Breast cancer is the most frequent cancer in women and represents the second leading cause of cancer death among women (after lung cancer). The etiology of breast cancer is still poorly understood with known breast cancer risk factors explaining only a small proportion of cases. Risk factors that modulate the development of breast cancer discussed in this review include: age, geographic location (country of origin) and socioeconomic status, reproductive events, exogenous hormones, lifestyle risk factors (alcohol, diet, obesity and physical activity), familial history of breast cancer, mammographic density, history of benign breast disease, ionizing radiation, bone density, height, IGF- 1 and prolactin levels, chemopreventive agents. Additionally, we summarized breast cancer risk associated with the following genetic factors: breast cancer susceptibility high-penetrance genes (BRCA1, BRCA2, p53, PTEN, ATM, NBS1 or LKB1) and low-penetrance genes such as cytochrome P450 genes (CYP1A1, CYP2D6, CYP19), glutathione S-transferase family (GSTM1, GSTP1), alcohol and one-carbon metabolism genes (ADH1C and MTHFR), DNA repair genes (XRCC1, XRCC3, ERCC4/XPF) and genes encoding cell signaling molecules (PR, ER, TNFalpha or HSP70). All these factors contribute to a better understanding of breast cancer risk. Nonetheless, in order to evaluate more accurately the overall risk of breast tumorigenesis, novel genetic and phenotypic traits need to be identified.
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PMID:Understanding breast cancer risk -- where do we stand in 2005? 1578 78

We investigated the promotor hypermethylation status of multiple genes in 49 oral squamous cell carcinomas (OSCC), using the methylation-specific PCR (MSP) assay. The genes examined included p16INK4a, p14ARF, RB1, p21Waf1, p27Kip1, PTEN, p73, 0(6)-MGMT, and GST-P. Detailed clinicopathological data, such as patient age, sex, tobacco use, alcohol consumption, lesion site, degree of tumor differentiation, tumor size, presence of lymph node metastasis, and clinical stage, were collected for all 49 samples. Overall, gene methylation was detected in 46.9% (23/49) of samples and was closely correlated with tobacco use or/and alcohol consumption. Of the genes investigated, p16INK4a, p14ARF, 0(6)-MGMT, RB1, PTEN, and p27Kip1 were found to be methylated in 34.7%, 20.4%, 12.2%, 10.2%, 6.1%, and 4.1% of these 49 tumors, respectively, but methylation of p21Waf1, p73, and GST-P was not detected at all. Methylation frequencies were much higher for each gene when computed among informative cases only. Concurrent promotor hypermethylation of p16INK4a and p14ARF correlated significantly with tumor size, lymph node metastasis, and stage III/IV advanced OSCC; p14ARF hypermethylation, in particular, was significantly associated with both lymph node metastasis and late clinical stage. Our results suggest that DNA methylation of multiple genes, especially hypermethylation of the p14ARF promoter, is common in OSCC and is associated with the use of tobacco and/or alcohol consumption. For this type of cancer, the data further implicates gene methylation as playing an important role in tumor progression.
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PMID:Promotor hypermethylation of p14ARF is a key alteration for progression of oral squamous cell carcinoma. 1597 25


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