Genetic polymorphism of glutathione S-transferase P1 and breast cancer risk

To evaluate the potential association between the GSTP1 genotype and the development of breast cancer, a hospital based case-control study was conducted on Korean women. The study population consisted of 171 histologically confirmed incident breast cancer cases and 171 age-matched controls with no present or previous history of cancer. PCR-RFLP was used for the GSTP1 genotyping and statistical evaluations were performed using an unconditional logistic regression model. Postmenopausal women with the GSTP1 Val allele were found to have a reduced risk of breast cancer (OR = 0.3, 95 % CI = 0.10-0.74). A significant interaction was observed between the GSTP1 genotype and alcohol consumption (p for interaction = 0.01); compared with never-drinking women with Ile/Ile genotype, ever-drinking women with the GSTP1 Val allele had almost a three-fold risk of breast cancer (OR = 2.9, 95 % CI = 1.05-7.85), whereas never-drinking women with Val allele had half this risk (OR = 0.5, 95 % CI = 0.27-0.93). Our findings suggest that the GSTP1 polymorphism influences individual susceptibility to breast cancer in the Korean women and this effect may be modified by alcohol consumption.     

A meta-analysis of the association of glutathione S-transferase P1 gene polymorphism with the susceptibility of breast cancer

Glutathione S-transferase P1 (GSTP1) is one of the important mutant sites for the cancer risk at present. The conclusions of the published reports on the relationship between GSTP1 A/G gene polymorphism and the risk of breast cancer are still debated. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of breast cancer. The association reports were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. 35 investigations were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and breast cancer susceptibility, consisting of 40,347 subjects (18,665 patients with breast cancer and 21,682 controls). The association between GSTP1 A/G gene polymorphism and breast cancer risk was not found for overall population, Caucasians and Africans. Interestingly, the GSTP1 A/G gene polymorphism was associated with the susceptibility of breast cancer in Asians (G allele: OR = 1.10, 95 % CI: 1.04–1.17, P = 0.001; GG genotype: OR = 1.36, 95 % CI: 1.14–1.62, P = 0.0008; AA genotype: OR = 0.92, 95 % CI: 0.85–0.98, P = 0.02). Furthermore, the GSTP1 A/G gene polymorphism was associated with the susceptibility of breast cancer for the analysis of the controls from hospital. In conclusion, GSTP1 A/G gene polymorphism is associated with the breast cancer susceptibility in Asians. However, more studies on the relationship between GSTP1 A/G gene polymorphism and the risk of breast cancer should be performed in further.     

Polymorphism of glutathione S-transferase P1 gene affects human vitamin C metabolism

There are large inter-individual differences in the metabolism of vitamin C (VC), which is composed of both ascorbic acid (AsA) and dehydroascorbic acid (DAsA). AsA is oxidized to DAsA in a series of xenobiotic reactions. Thus, the effects of polymorphism A313G (Ile105Val) in the gene for glutathione S-transferases P1 (GSTP1), one of the most active xenobiotic enzymes, on human VC metabolism were studied. The variant frequency of GSTP1 among the present subjects (n = 210) was AA 71.0%; GA 27.0% and GG 1.9%. At 24 h after administration of 1 mmol of VC to young women (n = 17; age, 21.0 ± 1.1 y), total VC excretion (46.7 ± 18.1 mg) by AA homozygotes of GSTP1 was greater (p < 0.0069) than that (28.2 ± 14.0 mg) by GA heterozygotes. One hour after administration of VC, blood total VC levels were also significantly different (p < 0.0036) between the homozygotes and heterozygotes. The effects of other polymorphisms in xenobiotic enzymes on VC metabolism were small.     

Tocotrienols inhibit human glutathione S-transferase P1-1

Tocopherols and tocotrienols are food ingredients that are believed to have a positive effect on health. The most studied property of both groups of compounds is their antioxidant action. Previously, we found that tocopherols and diverse tocopherol derivatives can inhibit the activity of human glutathione S-transferase P1-1 (GST P1-1). In this study we found that GST P1-1 is also inhibited, in a concentration-dependent manner, by alpha- and gamma-tocotrienol. The concentration giving 50% inhibition of GST P1-1 is 1.8 +/- 0.1 microM for alpha-tocotrienol and 0.7 +/- 0.1 microM for gamma-tocotrienol. This inhibition of GST P1-1 is noncompetitive with respect to both substrates CDNB and GSH. We also examined the 3D structure of GST P1-1 for a possible tocopherol/tocotrienol binding site. The enzyme contains a very hydrophobic pit-like structure where the phytyl tail of tocopherols and tocotrienols could fit in. Binding of tocopherol and tocotrienol to this hydrophobic region might lead to bending of the 3D structure. In this way tocopherols and tocotrienols can inhibit the activity of the enzyme; this inhibition can have far-reaching implications for humans.     

Association of glutathione S-transferase P1 gene polymorphism with the susceptibility of lung cancer

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) gene polymorphism and the risk of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Forty-four reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and lung cancer susceptibility, consisting of 12,363 patients with lung cancer and 13,948 controls. The association between GSTPI G allele and lung cancer risk was found in this meta-analysis (OR 1.08, 95?% CI 1.02–1.15, P?=?0.01). However, the GG genotype and AA genotype were not associated with the susceptibility of lung cancer. Furthermore, there was no association between GSTP1 A/G gene polymorphism and the risk of lung cancer in Caucasians, and East-Asians. In conclusion, GSTP1 G allele is associated with the lung cancer susceptibility. However, more studies on the relationship between GSTP1 A/G gene polymorphism and the risk of lung cancer should be performed in the future.     

Relation of glutathione S-transferase T1, M1 and P1 genotypes and breast cancer risk

The aim of this study was to investigate associations between genetic variability in specific Glutathione S-transferases (GST) genes (GSTM1, GSTT1 and GSTP1) and susceptibility to breast cancer. Genotypes of blood specimen DNA were determined for 65 women with incident cases of breast cancer and 108 control subjects. Associations between specific genotypes and the development of breast cancer were examined by the use of logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Neither GSTT1 nor GSTM1 homozygous null genotype was associated with a significant increased risk of developing breast cancer. The presence of valine alleles compared to isoleucine alleles in codon 105 in GSTP1 did not increase the risk of breast cancer development. The risk of breast cancer associated with a combined GSTT1 and GSTM1 null genotype was 3.37 (95% CI = 0.76-2.95, p = 0.115). The only significant association between increased risk of breast cancer development and GSTs polymorphisms was found when GSTT1 null, GSTM1 null and the presence of valine in GSTP1 in codon 105 were combined (p < 0.048, OR = 3.75, 95% CI = 1.01-13.90). Our findings suggest that combined genetic variability in members of the GST gene family may be associated with an increased susceptibility to breast cancer.     

Inhibition of human glutathione S-transferase P1-1 by the flavonoid quercetin

In the present study, the inhibition of human glutathione S-transferase P1-1 (GSTP1-1) by the flavonoid quercetin has been investigated. The results show a time- and concentration-dependent inhibition of GSTP1-1 by quercetin. GSTP1-1 activity is completely inhibited upon 1 h incubation with 100 microM quercetin or 2 h incubation with 25 microM quercetin, whereas 1 and 10 microM quercetin inhibit GSTP1-1 activity to a significant extent reaching a maximum of 25 and 42% inhibition respectively after 2 h. Co-incubation with tyrosinase greatly enhances the rate of inactivation, whereas co-incubation with ascorbic acid or glutathione prevents this inhibition. Addition of glutathione upon complete inactivation of GSTP1-1 partially restores the activity. Inhibition studies with the GSTP1-1 mutants C47S, C101S and the double mutant C47S/C101S showed that cysteine 47 is the key residue in the interaction between quercetin and GSTP1-1. HPLC and LC-MS analysis of trypsin digested GSTP1-1 inhibited by quercetin did not show formation of a covalent bond between Cys 47 residue of the peptide fragment 45-54 and quercetin. It was demonstrated that the inability to detect the covalent quercetin-peptide adduct using LC-MS is due to the reversible nature of the adduct-formation in combination with rapid and preferential dimerization of the peptide fragment once liberated from the protein. Nevertheless, the results of the present study indicate that quinone-type oxidation products of quercetin likely act as specific active site inhibitors of GSTP1-1 by binding to cysteine 47.     

Curcumin-glutathione interactions and the role of human glutathione S-transferase P1-1

Curcumin (diferuloylmethane), a yellow pigment of turmeric with antioxidant properties has been shown to be a cancer preventative in animal studies. It contains two electrophilic alpha, beta-unsaturated carbonyl groups, which can react with nucleophilic compounds such as glutathione (GSH), but formation of the GSH-curcumin conjugates has not previously been demonstrated. In the present studies, we investigated the reactions of curcumin with GSH and the effect of recombinant human glutathione S-transferase(GST)P1-1 on reaction kinetics. Glutathionylated products of curcumin identified by FAB-MS and MALDI-MS included mono- and di-glutathionyl-adducts of curcumin as well as cyclic rearrangement products of GSH adducts of feruloylmethylketone (FMK) and feruloylaldehyde (FAL). The presence of GSTP1-1 significantly accelerated the initial rate of GSH-mediated consumption of curcumin in 10 mM potassium phosphate, pH 7.0, and 1 mM GSH. GSTP1-1 kinetics determined using HPLC indicated substrate inhibition (apparent K(m) for curcumin of 25+/-11 microM, and apparent K(i) for curcumin of 8+/-3 microM). GSTP1-1 was also shown to catalyze the reverse reaction leading to the formation of curcumin from GSH adducts of FMK and FAL.     

Association of glutathione S-transferase P1 gene polymorphism with the risk of small-cell carcinoma of lung cancer

Abstract

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) gene polymorphism and the risk of small-cell carcinoma of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of small-cell carcinoma of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Ten reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and small-cell carcinoma of lung cancer. The G allele and GG genotype were not associated with the susceptibility of risk of small-cell carcinoma in overall populations, East-Asians and Turkish population. However, there was an association between GG genotype with the risk of small-cell carcinoma in Caucasians. In conclusion, GG genotype was associated with the risk of small-cell carcinoma in Caucasian patients with lung cancer. However, GSTP1 A/G gene polymorphism is not associated with the susceptibility of small-cell carcinoma in overall populations, East-Asians and Turkish population.     

Association of glutathione S-transferase P1 gene polymorphism with the histological types of lung cancer: a meta-analysis

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) A/G gene polymorphism and the histological types of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and histological types of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Seventeen reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and histological types of lung cancer. The G allele and GG genotype were not associated with the susceptibility of risk of squamous cell carcinomas, adenocarcinomas, small cell carcinoma, non-small cell carcinoma or large cell carcinoma. However, in the sub-group analysis, there was an association between G allele/GG genotype with the risk of squamous cell carcinomas in East-Asians and GG genotype was associated with the risk of small cell carcinoma in Caucasians. In conclusion, GSTP1 A/G gene polymorphism is not associated with the susceptibility of squamous cell carcinomas, adenocarcinomas, small cell carcinoma, non-small cell carcinoma or large cell carcinoma.     

Overexpression of glutathione S-transferase pi enhances the adduct formation of cisplatin with glutathione in human cancer cells

In this paper, we provide direct evidence that glutathione S-transferase π (GSTπ) detoxifies cisplatin (CDDP). We used human colonic cancer HCT8 cells sensitive and resistant to CDDP, the level of cisplatin-glutathione adduct (DDP-GSH) being higher in the resistant cells. There was an overexpression of GSTπ mRNA in these CDDP-resistant cells. Incubation of the cells with CDDP resulted in the formation of DDP-GSH dependent on the CDDP concentration and the incubation time. The formation of DDP-GSH was abolished when the cells were pre-treated with ethacrynic acid or ketoprofen, inhibitors of GSTπ. Purified GSTπ also catalyzed the formation of DDP-GSH in vitro, with an apparent K_m of 0.23 mM for CDDP and an apparent V_max of 4.9 nmol/min/mg protein. The increase in DDP-GSH produced by GSTπ was linear with incubation time up to 3 h and optimal of pH 7.4. A GSTπ transfectant cell line was constructed in HCT8 cells using a pcDNA3.1 (-)/Myc-His B with an expression vector containing cDNA for GSTπ. Transfection of GSTπ cDNA into HCT8 cells resulted in an increase in the expression of GSTπ by 1.4-fold in parallel with an augmentation of the formation of DDP-GSH. These results suggest that GSTπ plays a role in the formation of DDP-GSH and the acquisition of resistance to CDDP in cancer cells.     

Site-directed mutagenesis of amino acid residues involved in the glutathione binding of human glutathione S-transferase P1-1.

The four residues of human glutathione S-transferase P1-1 whose counterparts were indicated by X-ray crystallography to reside in the GSH-binding site of pig glutathione S-transferase P1-1 were individually replaced with threonine or alanine by site-directed mutagenesis to obtain mutants R13T, K44T, Q51A, and Q64A. The kinetic parameters, susceptibilities to an inhibitor, S-hexyl-GSH, and affinities for GSH-Sepharose of the latter were compared with those of the wild-type enzyme, and pKa of the thiol group of GSH bound in R13T was shown to be equivalent to that in the wild type. From the results, Lys44, Gln51, and Gln64 were deduced to contribute to the binding of GSH. On the other hand, Arg13 seems to be essential for the enzymatic activity as mainly involved in the construction of a proper structure of the active site.     

Expression and purification of hexahistidine-tagged human glutathione S-transferase P1-1 in Escherichia coli

The bacterial expression and purification of human pi class glutathione S-transferase (hGST P1-1) as a hexahistidine-tagged polypeptide was performed. The expression plasmid for hGST P1-1 was constructed by ligation of the cDNA which codes for the protein into the expression vector pET-15b. The expressed protein was purified by either glutathione or metal (Co(2+)) affinity column chromatography, which produced the pure and fully active enzyme in one step with a yield of more than 30 mg/liter culture. The activity of the purified protein was 130 units mg(-1) from the GSH affinity column and 112 units mg(-1) from the Co(2+) affinity column chromatography. The purity of the protein was assessed by electrospray ionization mass spectrometry and size-exclusion chromatography. It showed that the real molecular weight of the hexahistidine-tagged hGST P1-1 polypeptide chain agreed with the calculated value and that the purified protein eluted as an apparent homodimer on the gel filtration column. Our expression system allows the expression and purification of active hexahistidine-tagged hGST P1-1 in high yield with no need of removal of the hexahistidine tag and gives pure protein in one purification step allowing further study of this enzyme.     

Characterization and regulation of glutathione S-transferase gene from Schizosaccharomyces pombe

A glutathione S-transferase (GST) gene has been cloned from Schizosaccharomyces pombe for the first time. The nucleotide sequence determined was found to contain 2030 base pairs including an open reading frame of 229 amino acids that would encode a protein of a molecular mass of 27017 Da. The cloned GST gene was expressed and was found to function in S. pombe, Saccharomyces cerevisiae, and Escherichia coli. The plasmid pGT207 encoding the S. pombe GST gene appeared to be able to accelerate the growth of a wild type S. pombe culture. In a culture of S. pombe containing plasmid pGT207, the growth was inhibited less by mercuric chloride than in a culture with vector alone. The 1088 bp region upstream from the GST gene as well as the region encoding the N-terminal 14 amino acids was transferred into the promoterless beta-galactosidase gene of plasmid YEp357R to yield the fusion plasmid pYSH2000. beta-Galactosidase synthesis was induced by cadmium chloride, mercuric chloride, hydrogen peroxide, and menadione. It was also induced by high temperature. These results suggest that the cloned S. pombe GST gene is involved in the oxidative stress response.