Genetic polymorphism of cytochrome P450 1A1 (Cyp1A1) and glutathione transferases (M1, T1 and P1) among Africans

Frequency of CYP1A1*2A polymorphisms and deletion of the GSMT1 gene in a Peruvian mestizo population

The polymorphic variants of CYP1A1 and the deletion of GSTM1 are present in the Peruvian mestizo population. Wild type and mutated genotypes (WT/*2A and *2A/ *2A) were identified, whose allele frequencies are 0.31 (T allele) and 0.69 (C allele), respectively; 53% with wild type GSTM1 (+) and 47% with null GSTM1. The frequency in Iquiteño emigrants was 0.72 CYP1A1*2A and 25% GSTM1 (-); from Lima 0.67 CYP1A1*2A and 33% of GSTM1 (-). The Hardy-Weinberg equilibrium test for the studied population showed that both frequencies are out of balance, p > .05.

The presence of the risk allele of the CYP1A1*2A polymorphism and the deletion in the GSTM1 gene are high, which could be indicative of a phase I and II metabolic imbalance in this group of Peruvian populations, with potential risks of activating agents procarcinogens thus affecting the incidence of tumor pathologies with an environmental component.

Genetic Polymorphism of GSTP-1 Affects Cyclophosphamide Treatment of Autoimmune Diseases

Cyclophosphamide is one of the most potent and reliable anti-cancer and immunosuppressive drugs. In our study, 33 individuals with different autoimmune diseases were treated with cyclophosphamide according to standard protocols. The responses to the treatments were determined by measuring the alteration of several typical parameters characterizing the given autoimmune diseases over time. We concluded that about 45% of the patients responded to the treatment. Patients were genotyped for polymorphisms of the CYP3A4, CYP2B6, GSTM1, GSTT1, and GSTP1 genes and disease remission cases were compared to the individual polymorphic genotypes. It was found that the GSTP1 I105V allelic variation significantly associated with the cyclophosphamide treatment-dependent disease-remissions. At the same time the GSH content of the erythrocytes in the patients with I105V allelic variation did not change. It appears that the individuals carrying the Ile105Val SNP in at least one copy had a significantly higher response rate to the treatment. Since this variant of GSTP1 can be characterized by lower conjugation capacity that results in an elongated and higher therapeutic dose of cyclophosphamide, our data suggest that the decreased activity of this variant of GSTP1 can be in the background of the more effective disease treatment.

Glutathione S-transferase M1 and T1 genes deletion polymorphisms and risk of developing essential hypertension: a case-control study in Burkina Faso population (West Africa)

BACKGROUND

Glutathione S-transferases play a key role in the detoxification of persistent oxidative stress products which are one of several risks factors that may be associated with many types of disease processes such as cancer, diabetes, and hypertension. In the present study, we characterize the null genotypes of GSTM1 and GSTT1 in order to investigate the association between them and the risk of developing essential hypertension.

METHODS

We conducted a case-control study in Burkina Faso, including 245 subjects with essential hypertension as case and 269 control subjects with normal blood pressure. Presence of the GSTT1 and GSTM1 was determined using conventional multiplex polymerase chain reaction followed by gel electrophoresis analysis. Biochemical parameters were measured using chemistry analyzer CYANExpert 130.

RESULTS

Chi-squared test shows that GSTT1-null (OR = 1.82; p = 0.001) and GSTM1-active/GSTT1-null genotypes (OR = 2.33; p <  0.001) were significantly higher in cases than controls; the differences were not significant for GSTM1-null, GSTM1-null/GSTT1-active and GSTM1-null/GSTT1-null (p > 0.05). Multinomial logistic regression revealed that age ≥ 50 years, central obesity, family history of hypertension, obesity, alcohol intake and GSTT1 deletion were in decreasing order independent risk factors for essential hypertension. Analysis by gender, BMI and alcohol showed that association of GSTT1-null with risk of essential hypertension seems to be significant when BMI < 30 Kg/m², in non-smokers and in alcohol users (all OR ≥ 1.77; p ≤ 0.008). Concerning GSTT1, GSTM1 and cardiovascular risk markers levels in hypertensive group, we found that subjects with GSTT1-null genotype had higher waist circumference and higher HDL cholesterol level than those with GSTT1-active (all p <  0.005), subjects with GSTM1-null genotype had lower triglyceride than those with GSTM1-active (p = 0.02) and subjects with the double deletion GSTM1-null/GSTT1-null had higher body mass index, higher waist circumference and higher HDL cholesterol than those with GSTM1-active/GSTT1-active genotype (all p = 0.01).

CONCLUSION

Our results confirm that GSTT1-null genotype is significantly associated with risk of developing essential hypertension in Burkinabe, especially when BMI < 30 Kg/m², in non-smokers and in alcohol users, and it showed that the double deletion GSTM1-null/GSTT1-null genotypes may influence body lipids repartition.

Genetic polymorphism of drug metabolism enzymes (GSTM1, GSTT1 and GSTP1) in the healthy Malian population

Glutathione S-transferase genes, known to be highly polymorphic, are implicated in the process of phase II metabolism of many substrates, including xenobiotics, anticancer and anti-infective drugs. The detoxification activity is linked to individual genetic makeup. Therefore, the identification of alleles and genotypes in these genes within a population may help to better design genetic susceptibility and pharmacogenetic studies. We performed the present study to establish the frequencies of the GSTM1, GSTT1, and GSTP1 c. 313A > G (rs1695) polymorphisms in 206 individuals of the Malian healthy population. GSTM1 and GSTT1 were genotyped by using multiplex polymerase chain reaction, whereas genotypes of GSTP1 were identified by polymerase chain reaction followed by restriction fragment length polymorphism. The frequencies of GSTM1-null and GSTT1-null genotypes were respectively 24.3 and 41.3%. The observed genotype frequencies for GSTP1 were 25.73% homozygous wild-type AA, 49.03% heterozygous AG and 25.24% homozygous mutant GG. The frequency of GSTP1-A allele was 50.24% versus 49.76% for the GSTP1-G allele. The distribution of these three genes was homogeneous between men and women (p > 0.05). We found no statistical association between the presence of a particular profile of GSTM1 or GSTT1 with the genotypes of GSTP1 (p > 0.05). Nevertheless, we noticed that the majority of the individuals harboring the GSTM1-present or the GSTT1-present harbor also the GSTP1-AG genotype. In addition, the triple genotype GSTM1-present/GSTT1-present/AG was the most frequent with 25.2%. Our findings will facilitate future studies regarding genetic associations of multifactorial diseases and pharmacogenetic, thus opening the way to personalized medicine in our population.

GSTT1 and GSTM1 null variants in Mestizo and Amerindian populations from northwestern Mexico and a literature review

The GSTT1 and GSTM1 genes are key molecules in cellular detoxification. Null variants in these genes are associated with increase susceptibility to developing different types of cancers. The aim of this study was to determine the prevalence of GSTT1 and GSTM1 null genotypes in Mestizo and Amerindian individuals from the Northwestern region of Mexico, and to compare them with those reported worldwide. GSTT1 and GSTM1 null variants were genotyped by multiplex PCR in 211 Mestizos and 211 Amerindian individuals. Studies reporting on frequency of GSTT1 and GSTM1 null variants worldwide were identified by a PubMed search and their geographic distribution were analyzed. We found no significant differences in the frequency of the null genotype for GSTT1 and GSM1 genes between Mestizo and Amerindian individuals. Worldwide frequencies of the GSTT1 and GSTM1 null genotypes ranges from 0.10 to 0.51, and from 0.11 to 0.67, respectively. Interestingly, in most countries the frequency of the GSTT1 null genotype is common or frequent (76%), whereas the frequency of the GSMT1 null genotype is very frequent or extremely frequent (86%). Thus, ethnic-dependent differences in the prevalence of GSTT1 and GSTM1 null variants may influence the effect of environmental carcinogens in cancer risk.

Impact of glutathione transferases genes polymorphisms in nevirapine adverse reactions: a possible role for GSTM1 in SJS/TEN susceptibility

PURPOSE

Nevirapine (NVP) is used in developing countries as first-line treatment of HIV infection. Unfortunately, its use is associated with common serious adverse drug reactions, such as liver toxicity and the most severe and rare Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). GSTT1 and GSTM1 genes code for enzymes involved in the metabolism of a wide range of drugs. We hypothesized that this gene variability could be implicated in NVP adverse reactions.

METHODS

We analyzed the GSTM1 and GSTT1 null genotypes by multiplex PCR in a population of 181 patients from Mozambique, treated with NVP. A case/control association study was performed. We also counted the number of risk alleles in SJS/TEN patients and in controls, including the GSTM1 null genotype and four previously identified risk alleles in CYP2B6, HCP5, and TRAF3IP2 genes.

RESULTS

Among patients, 27 had developed SJS/TEN and 76 had developed hepatotoxicity during the treatment. The GSTM1 null genotype was more frequent in the cases with SJS/TEN than in the controls (OR = 2.94, P = 0.027). This association is also observed when other risk factors are taken into account, by a multivariate analysis (P = 0.024 and OR = 3.58). The risk allele counting analysis revealed a significantly higher risk for SJS/TEN in patients carrying three or four risk alleles. Moreover, all subjects with five or six risk alleles developed SJS/TEN, while subjects without any risk alleles were present only in the control group.

CONCLUSIONS

We observed an association between GSTM1 and SJS/TEN susceptibility. Moreover, GSTM1 contributes to the definition of a genetic risk profile for SJS/TEN susceptibility.

Hydrogel microarray for detection of polymorphisms in the UGT1A1, DPYD, GSTP1 and ABCB1 genes

BACKGROUND

Improving the efficacy of anticancer therapy remains an urgent and very important task. Screening of the individual genetic metabolism of cancer patients allows for prescribing adequate medication in the correct dose as well as for decreasing side effects associated with drug toxicity.

OBJECTIVE

Estimation of a microarray-based method for genotyping of the UGT1A1, DPYD, GSTP1, and ABCB1 metabolic regulation genes to evaluate for an increased risk of toxicity of anticancer drugs.

METHODS

The microarray was used to conduct genotyping of specimens taken from 115 cancer patients and 31 healthy donors.

RESULTS

A microarray-based method for identification of the rs8175347, rs3918290, rs1695, and rs1045642 polymorphisms in the corresponding UGT1A1, DPYD, GSTP1, and ABCB1 genes has been developed for genotyping. The results obtained were in full concordance with those obtained using control sequencing. The frequencies of the rs8175347, rs3918290, rs1695, and rs1045642 genetic variations were 0.38, 0, 0.35, and 0.56, respectively.

CONCLUSION

The implementation of this biochip-based method in diagnostic practice should increase the overall survival and quality of life of cancer patients, decrease the length of their hospital stay, and reduce treatment costs.

Analyses of Genetic Variations of Glutathione S-Transferase Mu1 and Theta1 Genes in Bangladeshi Tannery Workers and Healthy Controls

Glutathione S-transferases (GSTs) belong to a group of multigene detoxification enzymes, which defend cells against oxidative stress. Tannery workers are at risk of oxidative damage that is usually detoxified by GSTs. This study investigated the genotypic frequencies of GST Mu1 (GSTM1) and GST Theta1 (GSTT1) in Bangladeshi tannery workers and healthy controls followed by their status of oxidative stress and total GST activity. Of the 188 individuals, 50.0% had both GSTM1 and GSTT1 (+/+), 12.2% had GSTM1 (+/-), 31.4% had GSTT1 (-/+) alleles, and 6.4% had null genotypes (-/-) with respect to both GSTM1 and GSTT1 alleles. Among 109 healthy controls, 54.1% were double positive, 9.2% had GSTM1 allele, 32.1% had GSTT1 allele, and 4.6% had null genotypes. Out of 79 tannery workers, 44.3% were +/+, 16.8% were +/-, 30.5% were -/+, and 8.4% were -/-. Though the polymorphic genotypes or allelic variants of GSTM1 and GSTT1 were distributed among the study subjects with different frequencies, the differences between the study groups were not statistically significant. GST activity did not vary significantly between the two groups and also among different genotypes while level of lipid peroxidation was significantly higher in tannery workers compared to controls irrespective of their GST genotypes.

Evaluation of Glutathione-S-Transferase P1 Polymorphism and its Relation to Bone Mineral Density in Egyptian Children and Adolescents with Beta-Thalassemia Major

BACKGROUND

Osteoporosis is a major complication of beta thalassemia major (TM). Increased oxidative stress and its controlling genes were linked to osteoporosis. Ile105 Val variant is a functional polymorphism of Glutathione S-transferase P1 (GSTP1), with reduced anti-oxidative property. No data are available about this variant or its association with osteoporosis among thalassemia patients yet.

OBJECTIVES

To investigate Ile105Val polymorphism and its possible association with bone mineral density (BMD) values in a group of TM children.

METHODS

Thirty five TM children and 30 age and sex matched healthy controls were included. Liver and renal functions, serum ferritin, calcium, phosphorous, alkaline phosphatase and osteocalcin were assayed. BMD was determined by DXA with calculation of Z-scores at lumbar spine (LS) and femoral neck (FN). Height for age Z- score (HAZ) adjusted BMD Z-scores were calculated. GSTP1 Ile105Val polymorphism was studied by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The relative frequency of 105 Val allele was significantly higher in TM patients than the controls (p<0.0001). Significant association between genotype subgroups and BMD parameters was detected. Compared to wild homozygotes, polymorphic homozygotes had lower LS-BMD (p =0.029), LS-BMD Z -score (p=0.008 ), LS- BMD haz - Z-score (p=0.011), FN- BMD (p= 0.001), FN- BMD Z -score (p=0.02) and FN-BMD haz - Z-score (p=0.001). They exhibited higher osteocalcin levels compared to heterozygotes and wild homozygotes (p=0.012, p=0.013, respectively).

CONCLUSION

Ile105Val polymorphism was frequent among TM patients and could increase their susceptibility to reduced BMD. Large sample studies are required to confirm these findings.

GST M1-T1 null allele frequency patterns in geographically assorted human populations: a phylogenetic approach

Genetic diversity in drug metabolism and disposition is mainly considered as the outcome of the inter-individual genetic variation in polymorphism of drug-xenobiotic metabolizing enzyme (XME). Among the XMEs, glutathione-S-transferases (GST) gene loci are an important candidate for the investigation of diversity in allele frequency, as the deletion mutations in GST M1 and T1 genotypes are associated with various cancers and genetic disorders of all major Population Affiliations (PAs). Therefore, the present population based phylogenetic study was focused to uncover the frequency distribution pattern in GST M1 and T1 null genotypes among 45 Geographically Assorted Human Populations (GAHPs). The frequency distribution pattern for GST M1 and T1 null alleles have been detected in this study using the data derived from literatures representing 44 populations affiliated to Africa, Asia, Europe, South America and the genome of PA from Gujarat, a region in western India. Allele frequency counting for Gujarat PA and scattered plot analysis for geographical distribution among the PAs were performed in SPSS-21. The GST M1 and GST T1 null allele frequencies patterns of the PAs were computed in Seqboot, Gendist program of Phylip software package (3.69 versions) and Unweighted Pair Group method with Arithmetic Mean in Mega-6 software. Allele frequencies from South African Xhosa tribe, East African Zimbabwe, East African Ethiopia, North African Egypt, Caucasian, South Asian Afghanistan and South Indian Andhra Pradesh have been identified as the probable seven patterns among the 45 GAHPs investigated in this study for GST M1-T1 null genotypes. The patternized null allele frequencies demonstrated in this study for the first time addresses the missing link in GST M1-T1 null allele frequencies among GAHPs.

Genetic polymorphism of glutathione S-transferase P1 (GSTP1) in Delhi population and comparison with other global populations

Glutathione S-transferases (GSTs) belong to a super family of phase II detoxification enzymes, which play an important role in protecting cells from damage caused by endogenous and exogenous compounds by conjugating reactive intermediates with glutathione to produce less reactive water-soluble compounds. In the present study, we determined the frequencies of two polymorphisms in exon 5 and exon 6 of GSTP1 gene in 500 normal individuals from Delhi. GSTP1 polymorphism was analysed by PCR-RFLP using amplification refractory mutation system (ARMS) assay. Two polymorphic sites in GSTP1 (Ile105 → Val105; Ala114 → Val114) have been analysed simultaneously, which results in four alleles: GSTP1*A (wild-type Ile105; Ala114), GSTP1*B (Val105; Ala114), GSTP1*C (Val105; Val114) and GSTP1*D (Ile105; Val114). The GSTP1 allele frequency in Delhi population was 0.663, 0.248, 0.069, and 0.020 for GSTP1*A, GSTP1*B, GSTP1*C, and GSTP1*D respectively. The frequency of Ile105 and Val105 allele was 0.683 and 0.317 respectively and it was calculated for the purpose of comparison with published data where all the four alleles were not analysed. GSTP1 alleles from Delhi population were compared with reported frequencies from all over India, and from other ethnic groups worldwide. This study would provide a basic database for future genetic studies.

Cytochrome P450 pharmacogenetics in African populations

The Cytochrome P450 (CYP450) family of enzymes is involved in the oxidative metabolism of many therapeutic drugs, carcinogens and various endogenous substrates. These enzymes are highly polymorphic at an inter-individual and inter-ethnic level. Polymorphisms or genetic variations account for up to 30% of inter-individual differences seen in a variety of drug responses. The frequencies of the different metabolizer categories (slow, intermediate, extensive and ultra-rapid), the distribution of genetic variants, genotype-phenotype correlations and the clinical importance of the CYP450 enzymes have been extensively documented in Caucasian and Oriental populations. Limited data exists for African populations, despite the fact that this knowledge is critically important for these populations who experience a heavy burden of communicable and non-communicable diseases. In addition, the costs incurred through adverse drug reactions and non-responsiveness to therapy could be reduced through the wide-scale application of pharmacogenetics. This review provides an overview and investigation of CYP450 genotypic and phenotypic reports published from 1980 to present in African populations. Our findings confirm the high degree of variability that is expected when comparing individuals of African origin to other ethnic groups and also highlight the distribution of clinically relevant CYP450 alleles amongst the various African populations. The notable discordance in genotypic and phenotypic data amongst African populations exemplifies the need for in-depth and well-orchestrated molecular and pharmacological investigations of these populations in the future, for which whole genome sequencing and association studies will be critical.

Cytochrome 1A1 and 1B1 gene diversity in the Zanzibar islands

Amodiaquine (AQ) is a 4-aminoquinoline widely used in the treatment of malaria as part of the artemisinin combination therapy (ACT). AQ is metabolised towards its main metabolite desethylamodiaquine mainly by cytochrome P450 2C8 (CYP2C8). CYP1A1 and CYP1B1 play a minor role in the metabolism but they seem to be significantly involved in the formation of the short-lived quinine-imine. To complete the genetic variation picture of the main genes involved in AQ metabolism in the Zanzibar population, previously characterised for CYP2C8, we analysed in this study CYP1A1 and CYP1B1 main genetic polymorphisms. The results obtained show a low frequency of the CYP1A1*2B/C allele (2.4%) and a high frequency of CYP1B1*6 (approximately 42%) followed by CYP1B1*2 (approximately 27%) in Zanzibar islands. Genotype data for CYP1A1 and CYP1B1 show a low incidence of fast metabolisers, revealing a relatively safe genetic background in Zanzibar's population regarding the appearance of adverse effects.

Association of a deletion of GSTT2B with an altered risk of oesophageal squamous cell carcinoma in a South African population: a case-control study

Background

Polymorphisms in the Glutathione S-transferase genes are associated with altered risks in many cancers, but their role in oesophageal cancer is unclear. Recently a 37-kb deletion polymorphism of GSTT2B that reduces expression of GSTT2 has been described. We evaluated the influence of the GSTT1 and GSTT2B deletion polymorphisms, and the GSTP1 Ile105Val polymorphism (rs1695) on susceptibility to oesophageal squamous cell carcinoma (OSCC) in the Black and Mixed Ancestry populations of South Africa.

Methods and Results

The GSTT1, GSTT2B and GSTP1 variants were genotyped in 562 OSCC cases and 907 controls, and tested for association with OSCC and for interaction with smoking and alcohol consumption. Linkage disequilibrium (LD) between the deletions at GSTT1 and GSTT2B was determined, and the haplotypes tested for association with OSCC. Neither the GSTT1 deletion nor the GSTP1 Ile105Val polymorphism was associated with OSCC risk in the Black or Mixed Ancestry populations. The GSTT2B deletion was not associated with OSCC risk in the Black population, but was associated with reduced risk of OSCC in the Mixed Ancestry population (OR = 0.71; 95% CI 0.57–0.90, p = 0.004). Case-only analysis showed no interaction between the GST polymorphisms and smoking or alcohol consumption. LD between the neighboring GSTT1 and GSTT2B deletions was low in both populations (r²_Black = 0.04; r²_MxA = 0.07), thus these deletions should be assessed independently for effects on disease risk.

Conclusions

Although there was no association between the GSTT1 deletion polymorphism or the GSTP1 Ile105Val polymorphism with OSCC, our results suggest that the presence of the recently described GSTT2B deletion may have a protective effect on the risk of OSCC in the Mixed Ancestry South African population. This is the first report of the contribution of the GSTT2B deletion to cancer risk.

Polymorphisms of cytochrome P450 1A1, glutathione s-transferases M1 and T1 genes in Ouangolodougou (Northern Ivory Coast)

In this study, the frequencies of CYP1A1, GSTM1, and GSTT1 gene polymorphisms were determined in 133 healthy individuals from Ouangolodougou, a small rural town situated in the north of the Ivory Coast. As appeared in several published studies, ethnic differences in these frequencies have been found to play an important role in the metabolism of a relevant number of human carcinogens. In the studied sample, the frequencies of Ile/Ile (wild type), Ile/Val (heterozygous variant), and Val/Val (homozygous variant) CYP1A1 genotypes were 0.271, 0.692, and 0.037, respectively. Frequencies of GSTM1 and GSTT1 null genotypes were 0.361 and 0.331, respectively. No significant differences were noted between men and women. In contrast to published data for Africans, CYP1A1 *Val Allele frequency (0.383) was significantly high (p < 0.001) in this specific population. For the GSTT1 null genotype, no differences were found between the studied and other African populations, the contrary to what occurred for the GSTM1 null genotype in relation to Gambia and Egypt.

GSTT1 and GSTM1 gene polymorphisms in European and African populations

Glutathione S-transferases (GSTs) are a superfamily of detoxificant enzymes. Pharmacogenomic studies have revealed interethnic differences in GST allelic frequencies. This study is focused on GSTT1 (gene deletion, rs17850155, rs2234953, and rs11550605) and GSTM1 (gene deletion) gene frequency distributions in two population samples of Europe origin (Italy, n = 120; Spain, n = 94) and two population samples of Africa origin (Cameroon, n = 126; Ethiopia, n = 153). Detection of GSTT1 and GSTM1 null genotypes was performed by multiplex PCR analysis, while the other GSTT1 gene polymorphisms were detected using allele specific PCR and sequencing. GSTT1 and GSTM1 null frequencies in the samples analyzed fit with the variability range observed in European and African populations, respectively. The SNP analysis in GSTT1 gene did not highlight any nucleotide substitution in 493 individuals analyzed. The comparisons among GSTM1 and GSTT1 null phenotype frequencies in worldwide populations show different patterns between Asians, Africans, and Europeans. Important insights into the effects of GSTM1 and GSTT1 gene deletions on the pathogenesis of human diseases have been hypothesized. Detailed studies on the geography of GST variants could therefore increase knowledge about the relationship between ethnicity and the prevalence of certain diseases.

The 341C/T polymorphism in the GSTP1 gene is associated with increased risk of oesophageal cancer

Background

The Glutathione S-transferases (GSTs) comprise a group of enzymes that are critical in the detoxification of carcinogens. In this study the effects of polymorphisms in these genes on the risk of developing oesophageal squamous cell carcinoma (OSCC) were evaluated in a hospital-based case-control study in two South African population groups. Genetic polymorphisms in GSTs were investigated in 245 patients and 288 controls samples by PCR-RFLP analysis.

Results

The GSTP1 341T variant was associated with significantly increased risk of developing OSCC as observed from the odds ratios for the GSTP1 341C/T and GSTP1 341T/T genotypes (OR = 4.98; 95%CI 3.05-8.11 and OR = 10.9; 95%CI 2.43-49.1, respectively) when compared to the homozygous GSTP1 341C/C genotype. The risk for OSCC in the combined GSTP1 341C/T and T/T genotypes was higher in tobacco smokers (OR = 7.51, 95% CI 3.82-14.7), alcohol consumers (OR = 15.3, 95% CI 1.81-12.9) and those using wood or charcoal for cooking and heating (OR = 12.1, 95% CI 3.26-49) when compared to those who did not smoke tobacco, or did not consume alcohol or user other forms of fuel for cooking and heating. Despite the close proximity of the two GSTP1 SNPs (313A>G and 341C>T), they were not in linkage disequilibrium in these two population groups (D':1.0, LOD: 0.52, r²: 0.225). The GSTP1 313A/G polymorphism on the other hand, did not display any association with OSSC. The homozygous GSTT1*0 genotype was associated with increased risk of OSCC (OR = 1.71, 95%CI 1.18-2.46) while the homozygous GSTM1*0 genotype was associated with significantly decreased risk of OSCC in the Mixed Ancestry subjects (OR= 0.39, 95%CI 0.25-0.62).

Conclusions

This study shows that the risk of developing OSCC in the South African population can be partly explained by genetic polymorphisms in GST coding genes and their interaction with environmental factors such as tobacco smoke and alcohol consumption.

Population analysis of xenobiotic metabolizing genes in South Brazilian Euro and Afro-descendants

Individual variability in xenobiotic metabolism has been associated with susceptibility to developing complex diseases. Genes involved in xenobiotic metabolism have been evaluated in association studies; the difficulty of obtaining accurate gene frequencies in mixed populations makes interpretation of the results difficult. We sought to estimate population parameters for the cytochrome P450 and glutathione S-transferase gene families, thus contributing to studies using these genes as markers. We describe the frequencies of six genes (CYP1A1, CYP2D6, CYP2E1, GSTM1, GSTT1, and GSTP1) and estimate population parameters in 115 Euro-descendants and 196 Afro-descendants from Curitiba, South of Brazil. PCR-based methods were used for genotyping, and statistical analysis were performed by AMOVA with ARLEQUIN software. The mutant allele frequencies in the Afro-descendants and Euro-descendants, respectively, were: CYP1A1*2A = 30.1% and 15.2%; CYP2D6*4 = 14.5% and 21.5%; CYP2E1*5B = 7.9% and 5%; GSTP1*B = 37.8% and 28.3%. The null genotype frequencies were: GSTM1*0 = 36.8% and 46.1%; GSTT1*0 = 24.2% and 17.4%.

Influence of ethnicity on pharmacogenetic variation in the Ghanaian population

It has been well established that the frequencies of genomic variants can vary greatly between the populations of different countries. We sought to quantify the intra-population variability in Ghana to determine the value of genotyping studies done at a nationwide level. Further, we investigated the differences between the Ghanaian and other African populations to determine the quality of genomic representation provided by a small subgroup within the continent with regard to the general population. We genotyped 934 unrelated Ghanaian individuals for 15 single nucleotide polymorphisms (SNPs) from genes defined as clinically relevant based on their reported roles in the transport of, metabolism of, or as targets of the medicines listed in the World Health Organization Essential Medicines list. Populations within Ghana and between nations in Western Africa were genetically cohesive. In contrast, populations in other areas of Africa were genetically divergent. Gene allele frequency also differed significantly between the populations in African nations and the United States for several of the SNPs. These results demonstrate that national populations in similar geographic regions, like Africa, may have widely varying genetic allele frequencies for clinically relevant SNPs. Further genotyping studies of specific populations are necessary to provide the best medical care to all individuals.

Pharmacogenetically relevant polymorphisms in Portugal

OBJECTIVE

Most drugs are developed based on data from European-derived 'reference' populations; however, clinically relevant DNA polymorphisms often demonstrate population-specific patterns of allele frequencies. Given that the knowledge of the frequency distribution of functional polymorphisms in a population may guide national planning for selection of therapeutic options, in the present study we examined the allele frequencies of enzymes responsible for drug disposition in Portugal.

PATIENTS & METHODS

Using PCR- and Pyrosequencing-based methods, the current study assessed the frequencies of 15 key polymorphisms from genes encoding enzymes involved in Phases I, II and III of drug metabolism, DNA repair and intracellular metabolism in 135 healthy individuals from Portugal.

RESULTS

Allele frequencies were derived for cytochrome P450 (CYP)2C9*2 (13.2%), CYP2C9*3 (8%), CYP2C19*2 (14%), CYP3A4*1B (7%), CYP3A5*3C (87.5%), glutathione S-transferase (GST)M1*0 (77.9%), GSTP1 313A>G (33%), inosine triphosphatase 94C>A (7%), UDP-glucuronosyltransferase (UGT)1A1*28 (28%), UGT1A1 -3156G>A (23%), ATP-binding cassette (ABC)B1 1236C>T (46%), ABCB1 2677G>A/T (2 and 42%), ABCG2 421C>A (8%), excision repair cross-complementing rodent repair deficiency 2 2251A>C (3%) and thymidylate synthetase 1494del (31%).

CONCLUSION

Although, on the whole, the frequency distributions among the Portuguese fitted the patterns commonly found in other Europeans well, evidence for some degree of African influence was observed. This is the most comprehensive study on pharmacogenetically relevant variations in Portugal to date, and the baseline of pharmacogenetic data might be important for determining policy guidelines for cancer prevention and drug treatments in the Portuguese population.

Multiplex PCR detection of GSTM1, GSTT1, and GSTP1 gene variants: simultaneously detecting GSTM1 and GSTT1 gene copy number and the allelic status of the GSTP1 Ile105Val genetic variant

The glutathione S-transferase (GST) genes GSTM1, GSTT1, and GSTP1 are involved in the detoxification of a broad range of toxic substances. Genetic polymorphisms in these genes have been studied intensively for their potential role in cancer susceptibility and drug response. In Caucasians, the enzyme activity of GSTM1 and GSTT1 is absent in approximately 50 and 15% of the population, respectively, due to deletions of both chromosomal copies of the genes. A trimodal phenotype pattern exists in which individuals with two, one, or no functional genes are fast, intermediate, or slow "conjugators," respectively. Most studies investigating the effect of the GSTM1 and GSTT1 deletions do not distinguish between fast and intermediate conjugators because the applied genotyping assays only detect if at least one copy of either gene is present. We present a multiplex PCR assay that detects if an individual has none, one, or two copies of the GSTM1 and GSTT1 genes and simultaneously detects the allelic status of the GSTP1 Ile105Val genetic variant. A total of 200 Danes, 100 Somalis, and 100 Greenlanders were genotyped. This multiplex PCR assay enables future large-scale studies to investigate the role of GSTs.

Maternal and fetal single nucleotide polymorphisms in the epoxide hydrolase and gluthatione S-transferase P1 genes are not associated with pre-eclampsia in the Coloured population of the Western Cape, South Africa

Oxidative stress is thought to play an important role in the pathophysiology of pre-eclampsia. A defect in certain enzymes responsible for detoxification may cause prolonged exposure to reactive by-products and contribute to maternal endothelial as well as placental damage. Two polymorphisms affecting the function of the biotransformation enzymes epoxide hydrolase and glutathione S-transferase P1 were shown previously to be associated with pre-eclampsia in a Dutch population. The aim of this study was to determine if these two polymorphisms (maternal or fetal) contribute to pre-eclampsia in an anthropologically distinct population (the Western Cape region of South Africa) with a high incidence of the disease. Genomic DNA of mother - infant pairs with severe pre-eclampsia (n = 144), a population control group (n = 156) and control mother - infant pairs with uncomplicated pregnancy outcome (n = 45) were analysed for the EPHX and GSTP1 polymorphisms by polymerase chain reaction amplification and restriction enzyme digestion. Each polymorphism had a similar distribution in case and control subjects (mother and infant). The Val105/Val105 genotype of GSTP1 occurred at a higher frequency than reported for other populations. Neither maternal nor fetal EPHX Tyr113His and GSTP1 Ile105Val polymorphisms appear to contribute significantly to the pathophysiology of pre-eclampsia in the Coloured population of the Western Cape region of South Africa.

CYP3A5 genotypes and risk of oesophageal cancer in two South African populations

CYP3A5 is the major cytochrome P450 enzyme in the oesophagus and metabolises many potentially carcinogenic compounds. The frequencies of CYP3A5 allelic variants, CYP3A5*2, *3, *6 and *7 which code for enzymes with severely decreased activities were compared between 241 oesophageal cancer patients and 272 controls in Black and Mixed Ancestry South Africans. A significantly higher frequency of CYP3A5*3 was observed in the controls compared to patients amongst the Mixed Ancestry group (P=0.025). Individuals homozygous for defective CYP3A5 had reduced risk of developing oesophageal cancer (P=0.032).

Genetic analysis of glutathione S-transferase A1 and T1 polymorphisms in a Japanese population

Novel allelic variants have been found in the glutathione S-transferase (GST) A1 and T1 genes. The former GSTA1*B allele is associated with low expression and the latter GSTT1*B allele lacks GSTT1 activity. The information on frequencies of both variants is poorly documented in the Japanese population. In this study we determined the frequencies of allelic variants of GSTA1 and GSTT1 in a Japanese population using PCR-restriction fragment length polymorphism and allele-specific PCR. The frequencies of GSTA1*B, GSTT1*0 and GSTT1*B alleles in the subjects were 16.0%, 71.1% and 0%, respectively. This is the first report on the frequencies of allelic variants of GSTA1 and GST-1 in a Japanese population.

Polymorphism of glutathione S-transferase mu 1 and theta 1 genes and hepatocellular carcinoma in southern Guangxi, China

AIM: Glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) genes are involved in the metabolism of a wide range of carcinogens, but deletions of the genes are commonly found in the population. The present study was undertaken to evaluate the association between GSTM1 and GSTT1 gene polymorphisms and hepatocellular carcinoma (HCC) risk.

METHODS: The genetic polymorphisms were studied at an aflatoxin highly contaminated region in Guangxi, China. Polymerase chain reaction (PCR) technique was used to detect the presence or absence of the GSTM1 and GSTT1 genes in blood samples. The case group was composed of 181 patients of HCC identified by the pathologists and the control group was composed of 360 adults without any tumor.

RESULTS: The frequencies of GSTM1 and GSTT1 null genotypes in the control were 47.8% and 42.7%, while those in the HCC group were 64.6% and 59.7%, respectively. The differences between HCC group and control group were very significant (P<0.01). GSTM1 and GSTT1 combined null genotypes in HCC group and control group were 38.2% and 18.5% respectively, and the difference was significant (P<0.05).

CONCLUSION: The GSTM1 and GSTT1 null genotypes are associated with an increased risk of HCC in a special geographic environment. Combination of the two null genotypes in an individual is substantially increased twice the risk of HCC.

Oxygen free radical scavenger enzyme polymorphisms in systemic sclerosis

We performed a case-control study of polymorphisms of glutathione S-transferase (GST) isoenzymes and manganese superoxide dismutase (MnSOD) in black South Africans with systemic sclerosis (SSc). The frequency of the GSTM1*B phenotype was significantly decreased in the overall SSc group compared with controls (OR=0.19, p(corr)<.05), implying a possible protective effect against development of the disease. There was also a trend toward increased MnSODAla allele and phenotype frequencies in the diffuse cutaneous SSc subset compared with controls (OR=2.11 and 3.15, respectively, p(corr)<.1). Our findings provide new data on the distribution of GST and MnSOD polymorphisms in healthy Africans and further evidence that genetic factors may have a contributory role to play in predisposing to oxidative stress in SSc.

Allele frequencies for glutathione S-transferase and N-acetyltransferase 2 differ in African population groups and may be associated with oesophageal cancer or tuberculosis incidence

Glutathione S-transferase (GST) and arylamine N-acetyltransferase 2 (NAT2) metabolise many environmental and chemotherapeutic agents, which influence susceptibility to disease. Polymorphisms in these enzymes result in different host phenotypes and contribute to different disease profiles or responses to toxic or chemotherapeutic agents, depending on their frequency in different populations. GST and NAT2 polymorphisms were investigated in different population groups, including African populations, and a range of allelic frequencies have been observed. The GSTM1 null genotype frequency, reported in this paper in two South African ethnic groups, is the lowest reported (0.19-0.21). In contrast, these same groups have a high GSTT1 null frequency (0.41-0.54), which is considerably higher than in African-Americans, or other Africans. The GSTT1 null frequency is comparable to the Chinese, a population with a very high oesophageal cancer incidence, similar to that in the African group. The frequency of the GSTPi Val105 variant in the South African Xhosas was also high (0.53), differing significantly from the low frequency in other Africans. These variants could therefore be associated with high cancer susceptibility. In addition, the high proportion of NAT2 "fast" alleles may partially explain the high tuberculosis prevalence in South Africans, due to reduced isoniazid efficacy in the presence of rapid acetylation.