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)

Human ovarian carcinoma cells (C70 and C200) made resistant to cisplatin from A2780 cells demonstrated an approximately 20-fold resistance to the drug. These same cell lines showed no collateral resistance (as compared with the wild-type) to a novel glutathione S-transferase pi-activated prodrug [gamma-glutamyl-alpha-amino-beta[2-ethyl-N,N,N',N'-tetrakis (2-chloroethyl) phosphorodiamidate]-sulfonyl-propionyl-(R)-(-) phenylglycine; TLK286]. Previous results have shown a direct correlation between levels of GST pi expression and cytotoxicity for TLK286 (L. A. Rosario et al., Mol. Pharmacol., 58: 167-174, 2000.). However, protein levels of the isozyme were identical in wild-type C70 and C200 cell lines. In analyzing the DNA repair capacity of C70 and C200, an altered expression of the DNA-dependent protein kinase (DNA-PK) complex (catalytic subunit DNA-PKcs, and the heterodimers Ku70 and Ku80) was found. In C70 and C200 cells, DNA-PKcs was overexpressed at both the transcript and protein levels, whereas amounts of Ku70 and Ku80 were higher only at the level of protein expression. TLK286 in either its parent or activated form inhibited the catalytic kinase activity of purified DNA-PK with an IC50 value of approximately 1 microM. Coimmunoprecipitation of Ku70 after TLK286 treatment of purified DNA-PK and C70 cells showed a drug-induced destabilization of the protein-protein interaction between the catalytic subunit and the Ku heterodimer. Overall, these results implicate inhibition of DNA-PK as a component of TLK286 cytotoxicity and provide a rationale for its use in the clinical management of cisplatin-resistant ovarian cancer.
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PMID:Efficacy of a glutathione S-transferase pi-activated prodrug in platinum-resistant ovarian cancer cells. 1248 32

BRCA1 is a tumor suppressor gene mutated in cases of hereditary breast and ovarian cancer. BRCA1 protein is involved in apoptosis and growth/tumor suppression. In this study, we present evidence that p65/RelA, one of the two subunits of the transcription factor NF-kappaB, binds to the BRCA1 protein. Treatment of 293T cells with the cytokine tumor necrosis factor-alpha induces an interaction between endogenous p65/RelA and BRCA1. GST-protein affinity assay experiments reveal that the Rel homology domain of the p65/RelA subunit of NF-kappaB interacts with multiple sites within the N-terminal region of BRCA1. Transient transfection of BRCA1 significantly enhances the ability of the tumor necrosis factor-alpha or interleukin-1beta to activate transcription from the promoters of NF-kappaB target genes. Mutation of the NF-kappaB-binding sites in the NF-kappaB reporter blocks the effect of BRCA1 on transcription. Also the ability of BRCA1 to activate NF-kappaB target genes is inhibited by a super-stable inhibitor of NF-kappaB and by the chemical inhibitor SN-50. These data indicate that BRCA1 acts as a co-activator with NF-kappaB. In addition, we show that cells infected with an adenovirus expressing BRCA1 up-regulate the endogenous expression of NF-kappaB target genes Fas and interferon-beta. Together, this information suggests that BRCA1 may play a role in cell life-death decisions following cell stress by modulation of the activity of NF-kappaB.
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PMID:BRCA1 augments transcription by the NF-kappaB transcription factor by binding to the Rel domain of the p65/RelA subunit. 1270 Feb 28

It has been suggested that histologic subtype of ovarian cancer is a factor that determines the chemoresponsiveness of tumor. In this study, we wanted to clarify the prognostic significance of histologic subtype and its correlation to expression of chemoresistance-related proteins (CRPs) in ovarian cancer. A total of 93 stage II-IV ovarian cancers, where the proportion of serous, endometrioid, mucinous, and clear cell subtype was 61.3%, 14.0%, 7.5%, and 17.2%, respectively, were investigated for glutathione S-transferase-pi (GST-pi), MDR (multidrug resistance)-1, and p53 expression using immunohistochemistry. GST-pi expression was detected in 62.4% of the tumors and was not related to histologic subtype of tumor. MDR-1 expression was observed in 12.9% of the tumors tested and was more frequently detected in clear cell adenocarcinomas than other histologic subtypes of tumor (10/ 16 vs. 2 / 77, P < 0.001). P53 expression was found in 49.1% of serous, 53.8% of endometrioid, and 50% of mucinous adenocarcinomas. In contrast, none of 16 clear cell adenocarcinomas showed positive p53 staining. In univariate analysis, no direct correlations were found between CRPs and overall survival. Histology of mucinous/clear cell tumors (P = 0.0063), as well as FIGO stage III/IV (P = 0.0091) and residual tumor >or= 2 cm (P = 0.0045), was found to have independent prognostic value in multivariate analysis. In conclusion, histologic subtype proved to be the significant independent prognostic factor in addition to FIGO stage and residual tumor in stage II-IV ovarian cancer. GST-pi, MDR-1, and p53 expression pattern is closely related to histologic subtype of ovarian cancer, although they are not significant predictors of survival.
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PMID:Multivariate analysis for prognostic significance of histologic subtype, GST-pi, MDR-1, and p53 in stages II-IV ovarian cancer. 1467 14

We have used structure-based design techniques to introduce the drug O(2)-[2,4-dinitro-5-(N-methyl-N-4-carboxyphenylamino) phenyl] 1-N,N-dimethylamino)diazen-1-ium-1,2-diolate (PABA/NO), which is efficiently metabolized to potentially cytolytic nitric oxide by the pi isoform of glutathione S-transferase, an enzyme expressed at high levels in many tumors. We have used mouse embryo fibroblasts (MEFs) null for GSTpi (GSTpi(-/-)) to show that the absence of GSTpi results in a decreased sensitivity to PABA/NO. Cytotoxicity of PABA/NO was also examined in a mouse skin fibroblast (NIH3T3) cell line that was stably transfected with GSTpi and/or various combinations of gamma-glutamyl cysteine synthetase and the ATP-binding cassette transporter MRP1. Overexpression of MRP1 conferred the most significant degree of resistance, and in vitro transport studies confirmed that a GSTpi-activated metabolite of PABA/NO was effluxed by MRP1 in a GSH-dependent manner. Additional studies showed that in the absence of MRP1, PABA/NO activated the extracellular-regulated and stress-activated protein kinases ERK, c-Jun NH(2)-terminal kinase (JNK), and p38. Selective inhibition studies showed that the activation of JNK and p38 were critical to the cytotoxic effects of PABA/NO. Finally, PABA/NO produced antitumor effects in a human ovarian cancer model grown in SCID mice.
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PMID:Tumor cell responses to a novel glutathione S-transferase-activated nitric oxide-releasing prodrug. 1510 35

TLK 286 [TELCYTA] is an antitumour agent in clinical development with Telik. It was developed through the application of Telik's proprietary TRAP chemogenomics technology. TLK 286 works by targeting tumours that overexpress glutathione S-transferase (GST) P1-1, an enzyme that has been implicated in drug resistance and poor prognosis, and is elevated in solid tumours such as head and neck, breast, gastrointestinal, lung and ovarian tumours. TLK 286 is activated by GST P1-1 and, subsequently, initiates apoptosis in targeted tumour cells. Telik owns worldwide rights to TLK 286 and intends to commercialise it in the North American market. The company plans to select a collaborator in other territories with capabilities in manufacturing, sales and marketing. Telik was previously collaborating with Taiho, Japan, on development of TLK 286, but this agreement appears to have been terminated. Telik announced in October 2002 that it had begun the first of a series of planned clinical trials of TLK 286 in combination with docetaxel in patients with non-small cell lung cancer. A phase II trial was initiated in May 2001 in patients with ovarian cancer. Two additional combination trials were initated in ovarian cancer patients in December 2002. One of the trials will evaluate the combination of TLK 286 with Doxil in patients who have failed platinum-based chemotherapy. The second trial will evaluate TLK 286 in combination with carboplatin in patients who have recurrent, platinum-sensitive ovarian cancer. Telik held a successful phase III meeting with the US FDA to discuss plans for the first registration trial of TLK 286, and in March 2003 it was announced that a phase III registration trial of TLK 286 as monotherapy had been initiated in platinum-refractory ovarian cancer patients. The multinational trial has been designated the ASSIST-1 (Assessment of Survival in Solid Tumours-1) trial. Telik plans to enrol approximately 440 women who will be assigned to either TLK 286 treatment or a control (doxorubicin liposomal or topotecan).
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PMID:TLK 286. 1529 75

Claudins are integral membrane proteins essential in the formation and function of tight junctions (TJs). Disruption of TJs, which have essential roles in cell permeability and polarity, is thought to contribute to epithelial tumorigenesis. Claudin-3 and -4 are frequently overexpressed in ovarian cancer, but the molecular pathways involved in the regulation of these proteins are unclear. Interestingly, several studies have demonstrated a role for phosphorylation in the regulation of TJ complexes, although evidence for claudin phosphorylation is scarce. Here, we showed that claudin-3 and -4 can be phosphorylated in ovarian cancer cells. In vitro phosphorylation assays using glutathione S-transferase fusion constructs demonstrated that the C terminus of claudin-3 is an excellent substrate for cAMP-dependent protein kinase (PKA). Using site-directed mutagenesis, we identified a PKA phosphorylation site at amino acid 192 in the C terminus of claudin-3. Overexpression of the protein containing a T192D mutation, mimicking the phosphorylated state, resulted in a decrease in TJ strength in ovarian cancer cell line OVCA433. Our results suggest that claudin-3 phosphorylation by PKA, a kinase frequently activated in ovarian cancer, may provide a mechanism for the disruption of TJs in this cancer. In addition, our findings may have general implications for the regulation of TJs in normal epithelial cells.
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PMID:Phosphorylation of claudin-3 at threonine 192 by cAMP-dependent protein kinase regulates tight junction barrier function in ovarian cancer cells. 1590 76

Because most patients presenting with advanced ovarian cancer are not curable by surgery alone, chemotherapy represents an essential component of treatment. The disease may be considered as chemosensitive, as in around three-quarters of patients major (complete) responses are seen to initial treatment with the platinum-containing drugs cisplatin and carboplatin either used alone or in combination with the taxane, paclitaxel. However, only 15-20% of patients experience long-term remission as tumours often become resistant. The probability of achieving a second response depends on the duration of remission after first-line therapy: if this is < 6 months (considered as platinum resistant) second responses are uncommon and usually short-lived; if this is > 6, and especially if > 12 months (platinum sensitive), responses may be seen in about a quarter of patients, to the same drugs as used first line or to drugs such as pegylated liposomal doxorubicin, topotecan and hexamethylmelamine (all three are approved in this setting by the FDA). Gemcitabine, oral etoposide, docetaxel and oxaliplatin also show some activity either in sequential addition to existing approved of first-line therapy (as with gemcitabine) or as second-line therapy. However, there is an urgent unmet clinical need for new drugs capable of prolonging survival either by increasing long-term remission rates and/or duration as first-line treatment or to improve on outcomes of second-line treatment. Strategies currently being exploited in clinical trials include attempts to deliver more killing selectively to tumours (e.g., intraperitoneal administration of cisplatin or radiolabelled monoclonal antibodies), agents designed to target drug resistance mechanisms (e.g., TLK-286 activated by glutathione transferase), agents targeting proteins/receptors shown to be selectively expressed in the disease (e.g., monoclonal antibodies recognising CA-125 or HER1; small molecules targeting HER1 such as gefitinib) and disrupting established tumour vasculature (e.g., 5,6-dimethyl xanthenone 4-acetic acid). At the pre-clinical level, agents being developed to target the phosphatidylinositol 3 kinase/AKT/mTOR pathway, and K-Ras inhibitors, may offer efficacy in the future.
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PMID:Emerging drugs for ovarian cancer. 1593 76

Resistance to cis- or carboplatin represents the principal cause of therapeutic failures in ovarian carcinoma. The phenomenon of resistance to platinum-based drugs is partly related to expression of metallothionein (MT) and of glutathione S-transferase pi (GST-pi), but opinion on the subject is discordant. Documentation of a negative predictive effect of MT and GST-pi expression for the therapy employing platinum-based drugs would permit to select resistant cases in which other therapeutic approaches could be employed. The present study aimed at examining the relation between intensities of MT and GST-pi expressions in ovarian carcinomas and dynamics of the clinical course in the neoplastic disease in a group of cisplatin-treated patients. The analyses were performed on samples of ovarian carcinoma originating from 43 first-look laparotomies (FLLs) and, in 30 cases, from second-look laparotomies (SLL) from the same patients. Immunohistochemical reactions were performed on paraffin sections of studied tumors, using monoclonal antibodies to MT and GST-pi. The calculations showed that in cases with augmented expression of MT, mortality was higher. On the other hand, augmented expression of GST-pi predisposed to more frequent relapses, deaths and progression of the tumor. Kaplan-Meier analysis showed that a significantly shorter survival time was linked to cases of higher expression of MT at FLL and of higher expression of GST-pi at FLL, whereas a shorter progression-free time was manifested by cases with higher expression of GST-pi at FLL. The performed investigations indicate that augmented expressions of MT at FLL and GST-pi at FLL in ovarian cancer represent an unfavourable predictive factor in cisplatin-treated patients.
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PMID:Augmented expression of metallothionein and glutathione S-transferase pi as unfavourable prognostic factors in cisplatin-treated ovarian cancer patients. 1596 47

Cigarette smoking is a risk factor for colon adenoma. The glutathione S-transferase enzymes are involved in the detoxification of carcinogenic compounds including those found in tobacco smoke, and thus, may be important modifiers of individual risk of developing this disease. We examined the prevalence of GSTM1 and GSTT1 gene deletions, and two GSTP1 polymorphisms in 772 cases with advanced colorectal adenomas (>1 cm, villous elements or high-grade dysplasia) of the distal colon (descending or sigmoid colon or rectum) and 777 sigmoidoscopy negative controls enrolled in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Epidemiologic data on smoking was collected by self-administered questionnaire and DNA was extracted from whole blood or buffy coat. For GSTM1 and GSTT1, we used a newly developed TaqMan-based assay capable of discriminating heterozygous (+/-) individuals from those with two active alleles (+/+) and homozygous deletions (-/-). For GSTP1, the I105V and the A114V substitutions were identified using end point 5' nuclease assays (TaqMan). Adjusted odds ratios (OR) and 95% confidence intervals (95% CI) were determined using unconditional logistic regression, controlling for age, race, and gender. Advanced adenoma risk was increased in current/former smokers (OR, 1.4; 95% CI, 1.2-1.8). Risks were decreased in subjects with > or =1 inactive GSTM1 alleles (OR, 0.6; 95% CI, 0.4-0.9); and the association was independent of smoking status (P interaction = 0.59). Having > or =1 inactive GSTT1 allele was associated with increased risk among smokers (OR, 1.4; 95% CI, 1.1-1.9; P trend = 0.02) but not among never smokers (OR, 0.9; 95% CI, 0.6-1.3) and a significant interaction between smoking and genotype was observed (P interaction = 0.05). In summary, this is the first study to report associations between colorectal adenomas and GSTM1 wild-type and GSTT1 null allele among smokers. These findings only became apparent using a newly developed assay able to distinguish heterozygous from wild-type individuals. Our data provide evidence that phenotypic differences between these two groups exist.
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PMID:GSTM1, GSTT1, and GSTP1 polymorphisms and risk of advanced colorectal adenoma. 1603 Jan 23

Associations between genotypes of phase 2 enzymes and cancer risk are extracted from epidemiological studies, namely case-control studies. Variant alleles in glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), and N-acetyltransferase (NAT) have been used as molecular genetic biomarkers of risk. GSTM(my)1 has been associated with an increased risk of colorectal cancer, lung cancer, and bladder cancer and GSTP(pi)1 with prostate cancer. UGT1A1*28 and *37 are both associated with an increased risk of breast cancer as is SULT1A1*2. The presence of UGT1A1*28 results in an increased risk of ovarian cancer and NAT2 of colorectal and lung cancer. A high frequency of SULT1A1*1 has been identified in patients with breast cancer; the role in colorectal cancer is more controversial. This chapter discusses the balance between carcinogen activation and detoxification in relation to phase 2 enzymes.
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PMID:Cancer and molecular biomarkers of phase 2. 1639 74


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