Theta class glutathione S-transferase GSTT1 genotypes and susceptibility to cervical neoplasia: interactions with GSTM1, CYP2D6 and smoking

Individual effects of GSTM1 and GSTT1 polymorphisms on cervical or ovarian cancer risk: An updated meta-analysis

Background: Studies have shown that glutathione S-transferase M1 (GSTM1) and. glutathione S-transferase T1 (GSTT1) null genotype may increase the risk of cervical cancer (CC) or ovarian cancer (OC), however, the results of published original studies and meta-analyses are inconsistent. Objectives: To investigate the association between GSTM1 present/null and GSTT1 present/null polymorphisms, with the risk of cervical cancer or ovarian cancer. Methods: The odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the association between GSTM1 present/null and GSTT1 present/null polymorphisms and the risk of cervical cancer or ovarian cancer. To assess the confidence of statistically significant associations, we applied false positive reporting probability (FPRP) and bayesian false discovery probability (BFDP) tests. Results: Overall analysis showed that GSTM1 null was associated with an increased risk of cervical cancer, and subgroup analysis showed a significant increase in cervical cancer risk in Indian and Chinese populations; GSTT1 was not found null genotype are significantly associated with cervical cancer. Overall analysis showed that GSTM1 and GSTT1 null were not associated with the risk of ovarian cancer, subgroup analysis showed that GSTM1 null was associated with an increased risk of OC in East Asia, and GSTT1 null was associated with an increased risk of OC in South America. However, when we used false positive reporting probability and bayesian false discovery probability to verify the confidence of a significant association, all positive results showed "low confidence" (FPRP > .2, BFDP > .8). Conclusion: Overall, this study strongly suggests that all positive results should be interpreted with caution and are likely a result of missing plausibility rather than a true association.

Worldwide Systematic Review of GSTM1 and GSTT1 Null Genotypes by Continent, Ethnicity, and Therapeutic Area

Glutathione S-transferase Mu 1 (GSTM1) and glutathione S-transferase theta 1 (GSTT1) enzymes are glutathione-S-transferases with broad significance for susceptibility or resistance to multifactorial human diseases, as well as detoxification of environmental chemicals and drugs. Moreover, some individuals may have a complete deletion of GSTM1 and GSTT1 genes, which can contribute to patient-to-patient variability in drug safety and efficacy. GSTM1 and GSTT1 gene deletion frequencies can vary according to ethnicity and continental origin of the studied population with implications for achieving the goal of precision/personalized medicine in clinical practice. We report here a worldwide systematic review of the null genotypes in these two clinically important genes by continents, ethnicities, and therapeutic areas (TAs). Searches were performed in the PubMed database covering the period from 1992 to 2020. Out of the 1925 articles included, most studies analyzed European individuals, corroborating the literature failure for not adequately considering the non-European ethnicities. The frequency of GSTM1 and GSTT1 null genotypes was higher in patients than in healthy volunteers. Conversely, in East Asians, higher frequencies of the null genotypes were observed in healthy volunteers than patients. Oncology was the most intensively studied TA (57% of the articles) in relation to GSTM1 and GSTT1. In all, these results demonstrate that there is an important gap in the literature in terms of failure to consider a broader range of populations, as well as diseases wherein GSTM1 and GSTT1 variations have clinical and biological implications. To achieve precision/personalized medicine on a global/worldwide scale, with equity and inclusiveness, this knowledge/research gap ought to be remedied in studies of GSTM1 and GSTT1 null genotypes. To the best of our knowledge, this is the largest systematic review conducted to date addressing the GSTM1 and GSTT1 null genotypes worldwide. The analyses from the 1925 articles highlighted the current knowledge gaps in different TAs, ethnicities, and populations. Filling these gaps is of importance, given the role these genes play in relation to the metabolism of substances to which we have frequent contact with, the associations observed between their deletion and diseases such as cancer, in addition to the interethnic differences observed for the deletion frequencies of these genes.

GSTM1, GSTT1, and NQO1 polymorphisms in cervical carcinogenesis

The aim of the study is to investigate the clinical significance of glutathione-S-transferase GSTM1, GSTT1, and NQO1 c.609C>T (rs1800566) genetic polymorphisms in cervical carcinogenesis. GSTM1, GSTT1, and NQO1 polymorphisms together with human papillomavirus (HPV) types were examined in a total of 192 cervical smear in exfoliated cervical cell samples using polymerase chain reaction (PCR) system and real-time polymerase chain reaction (PCR) system. The 19 patients with high-grade squamous intraepithelial lesion had statistically higher frequency of null GSTT1 genotype than 9 with low-grade squamous intraepithelial lesion (LSIL) among the 67 patients with high-risk HPV (P = 0.024). The 24 patients with HSIL had also statistically higher frequency of NQO1 (CT+TT) genotype than 14 with LSIL among the 67 patients with high-risk HPV (P = 0.024). GSTT1 null and NQO1 genotype in cervical cell samples may be associated with more severe precancerous lesions of the cervix in a Japanese population.

Glutathione S-transferase T1 and M1 polymorphisms and risk of uterine cervical lesions in women from central Serbia

The aim of this study was to investigate the frequencies of GSTT1 and GSTM1 deletion polymorphisms in newly-diagnosed patients with uterine cervical lesions from central Serbia. Polymorphisms of GST genes were genotyped in 97 patients with cervical lesions and 50 healthy women using a multiplex polymerase chain reaction (PCR). The GSTM1 null genotype was significantly more prominent among the patients than in controls (74.2% vs 56.0%), the risk associated with lesions being almost 2.3-fold increased (OR=2.26, 95%CI=1.10-4.65, p=0.03) and 3.17-fold higher in patients above >45 years old (95%CI=1.02-9.79, p=0.04). The analysis of the two genotypes demonstrated that GSTM1 null genotype significantly increased risk only for low grade squamous intraepithelial lesion-LSIL (OR=2.81, 95%CI=1.03-7.68, p=0.04). GSTT1 null genotype or different genotype combinations were not found to be risk factors, irrespective to lesion stages, age or smoking. We found that the risk of cervical lesions might be significantly related to the GSTM1 null genotype, especially in women aged above 45 years. Furthermore, the GSTM1 polymorphism might have greater role in development of early stage lesions.

A comprehensive review on host genetic susceptibility to human papillomavirus infection and progression to cervical cancer

Cervical cancer is the second most common cancer in women worldwide. This is caused by oncogenic types of human papillomavirus (HPV) infection. Although large numbers of young sexually active women get HPV-infected, only a small fraction develop cervical cancer. This points to different co-factors for regression of HPV infection or progression to cervical cancer. Host genetic factors play an important role in the outcome of such complex or multifactor diseases such as cervical cancer and are also known to regulate the rate of disease progression. The aim of this review is to compile the advances in the field of host genetics of cervical cancer. MEDLINE database was searched using the terms, ‘HPV’, ‘cervical’, ‘CIN’, ‘polymorphism(s)’, ‘cervical’+ *the name of the gene* and ‘HPV’+ *the name of the gene*. This review focuses on the major host genes reported to affect the progression to cervical cancer in HPV infected individuals.

Genetic Polymorphism of Cancer Susceptibility Genes and HPV Infection in Cervical Carcinogenesis

It is widely accepted that specific human papillomavirus (HPV) types are the central etiologic agent of cervical carcinogenesis. However, a number of infected women do not develop invasive lesions, suggesting that other environmental and host factors may play decisive roles in the persistence of HPV infection and further malignant conversion of cervical epithelium. Although many previous reports have focused on HPV and environmental factors, the role of host susceptibility to cervical carcinogenesis is largely unknown. Here, we review the findings of genetic association studies in cervical carcinogenesis with special reference to polymorphisms of glutathione-S-transferase (GST) isoforms, p53 codon 72, murine double-minute 2 homolog (MDM2) gene promoter 309, and FAS gene promoter -670 together with HPV types including our recent research results.

Null genotypes of GSTM1 and GSTT1 contribute to risk of cervical neoplasia: an evidence-based meta-analysis

Background and Objectives

Glutathione S-transferases (GSTs) are multifunctional enzymes that play a key role in the detoxification of varieties of both endogenous products of oxidative stress and exogenous carcinogens.

Methods

In this meta-analysis, twenty-five studies were identified by searching PubMed, EMBASE, ISI Web of Science and CBM databases: 23 evaluated GSTM1 and 19 evaluated GSTT1. Crude odds ratios with corresponding 95% confidence intervals were used to estimate the association between GSTM1 and GSTT1 polymorphisms and risk of cervical neoplasia. Subgroup analyses were conducted by pathological history, ethnicity, source of DNA for genotyping, quality score, and matching variable.

Results

The null genotypes of GSTM1 and GSTT1 polymorphisms were associated with a significantly increased risk of cervical neoplasia (for GSTM1: OR = 1.40; 95%CI, 1.19–1.65; for GSTT1: OR = 1.30; 95%CI, 1.05–1.62, respectively). Subgroup analyses showed that the null genotype of GSTM1 increased the risk of cervical neoplasia in Asians, studies with DNA isolation from white blood cells and tissue samples, both high and low quality studies, and matched studies. In GSTM1-GSTT1 interaction analysis, individuals with dual null genotype were associated with a significantly increased risk of cervical neoplasia (OR = 1.72; 95%CI, 1.18–2.51).

Conclusion

These findings indicate that GSTM1 and GSTT1 polymorphisms, particularly GSTM1-GSTT1 interaction, may play critical roles in the development of cervical neoplasia. A conservative manner should be adopted to interpret these results because of obvious heterogeneity between-study, unadjusted data, and relatively small sample size in this meta-analysis. Well designed studies with larger sample size are of great value to confirm these results.

Germline polymorphisms of glutathione-S-transferase GSTM1, GSTT1 and p53 codon 72 in cervical carcinogenesis

The clinical significance of glutathione-S-transferase GSTM1, GSTT1 and p53 codon 72 polymorphisms in cervical carcinogenesis was investigated. Germline polymorphisms of GSTM1, GSTT1 and p53 codon 72 together with human papillomavirus (HPV) types were examined in a total of 457 blood and cervical smear samples from normal healthy women and the patients with premalignant and malignant cervical lesions. The 167 patients with low-grade squamous intraepithelial lesion (LSIL), 49 with high-grade SIL (HSIL) and 83 with squamous cell carcinoma (SCC) had significantly higher frequency of high-risk HPV than 158 controls. The 49 patients with HSIL and 83 with SCC had statistically higher frequency of null GSTT1 genotype than 158 controls. There was an increased odds ratio for null GSTT1 genotype in HSIL and SCC cases compared with controls among 191 patients with high-risk HPV. The 67 cases with HPV types 16 and/or 18 had higher frequency of the GSTT1 null genotype than 186 with other types of HPV. There was no statistical difference in the polymorphic frequency of GSTM1 and p53 codon 72 genotypes between SILs and controls with or without high-risk HPV. These results suggest that GSTT1 null genotype may increase the risk of cervical cancer particularly in the cases with high-risk HPV types in a Japanese population.

GST (GSTM1, GSTT1, and GSTP1) polymorphisms in the genetic susceptibility of Turkish patients to cervical cancer

OBJECTIVE

This work investigates the role of glutathione S-transferase M1 (GSTM1), glutathione S-transferase T1 (GSTT1), and glutathione S-transferase P1 (GSTP1) enzymes and polymorphisms, which are found in phase II detoxification reactions in the development of cervical cancer.

METHODS

This study was conducted with 46 patients diagnosed with cervical cancer and 52 people with no cancer history. Multiplex PCR methods were used to evaluate the GSTM1 and GSTT1 gene polymorphism. However, the GSTP1 (Ile105Val) gene polymorphism was studied using a PCR-RFLP method. The patient and control groups were compared using a chi-square test with p<0.05.

RESULTS

In the patient group, statistical significance was determined for gravidity (p=0.03), parity (p=0.01), and the number of living children (p=0.01) compared to the control group. The gene frequency of GSTM1, GSTT1, and GSTP1 polymorphisms was evaluated. We observed that GSTM1 and GSTT1 null genotype frequencies were 54.3% and 32.6% respectively, while GSTP1 (Ile/Val), (Ile/Ile), (Val/Val) genotype frequencies were 52%, 44%, and 4%, respectively, in the cervical cancer patients. No statistical variation was determined between the control and patient groups in terms of GSTM1, GSTT1, and GSTP1 polymorphisms (p>0.05).

CONCLUSION

Our results demonstrate that GSTT1, GSTM1, and GSTP1 polymorphisms are not associated with cervical cancer in Turkish patients.

Evaluating glutathione S-transferase (GST) null genotypes (GSTT1 and GSTM1) as a potential biomarker of predisposition for developing leukopenia

Glutathione S-transferase (GST) enzymes protect cells against xenobiotics and oxidative stress products through an electrophilic conjugation process. We investigated the theta (GSTT1) and mu (GSTM1) null genotypes in a group of leukopenic subjects and normal subjects from Northeast Brazil, evaluating their use as biomarkers of susceptibility for developing leukopenia. In a sample-based case-control study, we analysed white blood cell (WBC) counts and GSTT1 and GSTM1 genotypes. A total of 278 subjects were analysed: 91 with leukopenia and 187 controls. GSTT1 null genotype conferred a 5.92-fold risk for occurrence of leukopenia [odds ratios (OR) = 5.92, CI(MLE): 1.64-26.72, P(MLE) = 0.002] and a 3.90-fold risk of neutropenia (OR = 3.90; CI(MLE): 1.05-13.66; P(MLE) = 0.02), while GSTM1 null genotype conferred a 1.78-fold risk for leukopenia (OR = 1.75; CI(MLE): 1.04-3.06, P(MLE) = 0.017) and no risk of neutropenia (OR = 1.71; CI(MLE): 0.88-3.35; P(MLE) = 0.06). The GSTT1, but not the GSTM1 null genotype, was found to be associated with leukopenia and neutropenia. More cellular and molecular studies are needed to evaluate the existence of genotype interactions, and to confirm the appropriateness of using the GSTT1 and/or GSTM1 null genotypes as biomarkers of susceptibility to white blood-cell deficiencies.

Germline polymorphism of cancer susceptibility genes in gynecologic cancer

The multifactorial process of carcinogenesis involves mutations in oncogenes, or tumor suppressor genes, as well as the influence of environmental etiological factors. Common DNA polymorphisms in low penetrance genes have emerged as genetic factors that seem to modulate an individual's susceptibility to malignancy. Genetic studies, which lead to a true association, are expected to increase understanding of the pathogenesis of each malignancy and to be a powerful tool for prevention and prognosis in the future. Here, we review the findings of genetic association studies of gene polymorphisms in gynecologic cancer with special reference to glutathione-S-transferase, FAS/CD95 and p53 genes including our recent research results.

Glutathione-S-transferase M1 and T1 and cytochrome P1A1 genetic polymorphisms and susceptibility to cervical intraepithelial neoplasia in Greek women

The aim of the study was to determine the importance of genetic polymorphisms of glutathione-S-transferase T1 and M1 and cytochrome P1A1 genes in the development of cervical intraepithelial neoplasia in Greek women. This was a prospective, case-control study conducted by the Cervical Pathology and Colposcopy Unit of a University Ob/Gyn Department from 1999 to 2003. Cervical smears from 114 controls without any cytological and/or colposcopical evidence of cervical pathology and from 166 women with history of cervical intraepithelial neoplasia (56 CIN I, 54 CIN II and 56 CIN III) were examined with polymerase chain reaction for the above-mentioned genetic polymorphisms, taking also in mind their smoking attitudes. Statistical analysis was performed to detect any association between the null genotype of GSTM1 and GSTT1 genes and the CYP1A1 m1 polymorphism and the severity of cervical intraepithelial neoplasia. The distributions of the GSTT1 and GSTM1 wild-type genotypes were 57.48 and 39.75%, respectively. No woman with homozygous GSTT1 and GSTM1 null/null genotype was identified. CYP1A1 m1 polymorphism frequency was 24.49%. No woman with homozygous CYP1A1 m1/m1 genotype was detected as well. No significant difference in the frequencies of the GSTM1 and GSTT1 null alleles, and the CYP1A1 m1 polymorphism, was found between cases and controls. After application of Mantel-Haenszel chi procedure, there was no linear severity of the lesion and the frequency of these polymorphisms. According to our results, glutathione-S-transferase T1 and M1 and cytochrome P1A1 genetic polymporphisms do not appear to be a risk factor for cervical disease irrespective of smoking habits.

Exposure to wood smoke, HPV infection, and genetic susceptibility for cervical neoplasia among women in Colombia

Cervical cancer is the second leading cause of death from cancer among women in Colombia (16/100,000). Infection with high-risk human papillomavirus (HPV) plays a major role in the etiology of high-grade squamous intraepithelial lesions (HSILs). Exposure to chemical agents may be a cofactor for tumor induction, and individual genetic differences in the metabolism of these chemical agents may affect the susceptibility of individuals towards the development of HSIL. In this case-control study, a total of 91 cases with HSIL and 92 healthy controls, frequency-matched by age and place of origin, were recruited, and their frequencies of CYP2E1, GSTM1, and GSTT1 polymorphism were determined. We then evaluated the association of these polymorphisms, by themselves and in combination with wood smoke exposure and HPV-infection status, with the risk of HSIL. The results indicate that GSTM1 and GSTT1 polymorphism were not associated with HSIL, although a small increase in risk was observed for individuals who were GSTT1 null (OR = 1.4, 95% CI = 0.57-3.44). Contrary to other investigations, the c2/c2 variant of the CYP2E1 gene was associated with a significant increase in risk after adjusting for wood smoke exposure (OR = 6.3, 95% CI = 1.10-36.38) or wood smoke exposure and HPV-infection status (OR = 10.7, 95% CI = 1.76-65.58). Wood smoke exposure also increased the risk of HSIL among CYP2E1 c2/c2 HPV-positive women (OR = 3.3, CI = 0.50-22.50); however, the increase did not achieve statistical significance. Our study provides tantalizing evidence that genetic differences in the metabolism of wood smoke carcinogens, particularly metabolism by CYP2E1, may confer susceptibility for HSIL development. Further investigations with larger populations will be needed to confirm this association, which may provide important information for improving cervical cancer prevention programs.

Germline genetic polymorphisms of CYP1A1, GSTM1 and GSTT1 genes in Indian cervical cancer: Associations with tumor progression, age and human papillomavirus infection

OBJECTIVES

Host genetic factors may play a role in human papillomavirus (HPV)-associated tumorigenesis, although the issue continues to be a focus of much debate. Biotransformation is critical in carcinogenic activity of numerous environmental carcinogens. It is therefore possible that polymorphisms of genes producing functional changes in xenobiotic metabolizing enzymes may be susceptible factors in cervical carcinogenesis. This study looked into possible relationships among these factors.

METHODS

In this case-control study, we analyzed leukocyte DNA from a total of 312 subjects for germline polymorphisms of CYP1A1 (m1 and m2), GSTM1 and GSTT1 at various stages of the cervical tumor progression spectrum, using PCR and RFLP.

RESULTS

Both m1 and m2 polymorphisms of the CYP1A1 gene were more frequent among cases (36.1% for m1 and 38.1% for m2) compared to control subjects (18.2% and 17.6% respectively). The odds ratio of a subject with homozygous CYP1A1 m1 and m2 variant being a case was highest (m1 OR = 4.77 [95% CI = 1.28-17.77]; P = 0.02 and m2 OR = 5.48 [95% CI = 1.49-20.19]; P = 0.011) respectively. The distribution of m1 and m2 CYP1A1 genotypes was also studied as a function of age and in relation to the presence of HPV 16 infection. The risk due to CYP1A1 m1 genotype, when adjusted for HPV status, showed a significantly increased risk (OR = 3.58, 95% CI = 1.88-6.81; P = 0.0001). Similar results were observed in the case of CYP1A1 m2 variant and HPV 16. There was a significant over-representation of both m1 (25.9% vs. 13.9%) and m2 (27.9% vs. 13.3%) polymorphisms in older women (46 years or more). GSTM1 and GSTT1 deletions were also prominent among cases (53.7% and 16.3% respectively) compared to controls (32.7% and 9.7% respectively). A higher proportion of both GSTT1 and GSTM1 deletions were also detected in HPV-16-positive subjects.

CONCLUSIONS

These results suggest that polymorphisms in the CYP1A1, GSTM1 and GSTT1 genes may render women more susceptible to the development of cervical cancer. The association between this susceptibility and the presence of human papillomavirus infection further emphasizes the significance of the genetic polymorphisms.

Interaction of passive smoking with GST (GSTM1, GSTT1, and GSTP1) genotypes in the risk of cervical cancer in India

Human papilloma virus (HPV) infection is a major cause of cervix cancer, but a number of infected women do not develop invasive lesions, suggesting that HPV infection in itself is not a sufficient factor and that other cofactors, such as smoking, play an important role in development of cervix cancer. Alongside active cigarette smoking, passive smoking is an independent risk factor for cervix cancer. Smoking maintains cervical HPV infection longer and decreases potential of clearing an oncogenic infection. Thus, it is quite possible that polymorphism at detoxifying enzyme coding loci such as GSTM1, GSTT1, and GSTP1 may determine susceptibility to cervix cancer. This study evaluates the combined effects of genetic polymorphisms of GSTM1, GSTT1, and GSTP1 on susceptibility to cervical cancer and interaction of these genes with smoking. On individual analysis of GSTM1, GSTT1, and GSTP1, it was observed that passive smokers having genotypes GSTM1 (null) (OR = 7.0, 95% CI = 2.19-22.36, P = 0.0005), GSTT1 (null) (OR = 10.2, 95% CI = 1.23-84.18, P = 0.02), and GSTP1 (ile/val) (OR = 6.4, 95% CI = 2.25-18.38, P = 0.0005) have an increased risk of developing cervix cancer. It is thus concluded that cervical cancer risk is increased in passive smokers with GSTM1 (null), GSTT1 (null), and GSTP1 (ile/val) genotypes.

N7-methyldeoxyguanosine levels in DNA isolated from cervical cytology samples are associated with smoking

Smoking has been associated, in epidemiological studies, with an increased risk of cervical neoplasia. This may be in part due to the presence of tobacco-specific nitrosamines in cervical mucous of smokers, which may result in carcinogenic DNA damage. We have thus examined whether cervical DNA contains alkylation damage arising from exposure to methylating agents (N7-methyldeoxyguanosine, N7-MedG). DNA was extracted from cervical cytology samples and N7-MedG levels were measured using an immunoslotblot assay. Ninety percentage of the DNA samples were alkylated and N7-MedG levels (mean, 95% CI) in ever-smokers (1.27, 0.90-1.81 micromol/mol dG) were significantly higher than those in nonsmokers (0.42, 0.20-0.91 micromol/mol dG: p = 0.005). N7-MedG adduct levels were significantly correlated with number of cigarettes smoked per day and pack years of cigarette smoking in current smokers. There was no association with N7-MedG levels and cervical intraepithelial neoplasia status, age, parity or contraception use. Our study suggests that cervical DNA contains alkylation damage that can arise from exposure to cigarette smoke.

HER-2 codon 655 polymorphism in cervical carcinogenesis

HER-2 codon 655 polymorphism together with human papillomavirus (HPV) types were examined in a total of 279 cervical smear samples. Forty-nine patients with high-grade squamous intraepithelial lesion had higher frequency of high-risk HPV than 167 patients with low-grade squamous intraepithelial lesion and 63 controls. There was no statistical difference in the frequencies of HER-2 Ile/Ile, Ile/Val, and Val/Val genotypes between squamous intraepithelial lesions (SILs) and controls. When the Ile/Ile genotype was compared to the Ile/Val + Val/Val genotypes, there was also no statistical difference in the genotype prevalence between SILs and controls either in 91 or 188 patients with or without high-risk HPV, respectively. These results suggest that the HER-2 polymorphism at codon 655 in cervical cell samples is unlikely to be associated with HPV status and the onset of cervical cancer in a Japanese population.

Glutathione-S-transferase and p53 polymorphisms in cervical carcinogenesis

OBJECTIVE

To investigate the clinical significance of glutathione-S-transferase GSTM1, GSTT1 and p53 codon 72 polymorphisms in cervical carcinogenesis.

METHODS

GSTM1, GSTT1 and p53 codon 72 polymorphisms together with human papillomavirus (HPV) types were examined in a total of 198 cervical smear samples using multiplex polymerase chain reaction (PCR) and PCR restriction fragment length polymorphism (RFLP) techniques.

RESULTS

Forty-two patients with high-grade squamous intraepithelial lesion (HSIL) had higher frequency of high-risk HPV and null GSTT1 genotype than 102 with low-grade SIL (LSIL) and 54 controls. Thirty-one patients with HSIL had also statistically higher frequency of null GSTT1 genotype than 28 with LSIL among 69 patients with high-risk HPV. There was no statistical difference in p53 Arg, Arg/Pro and Pro genotypes between SILs and controls with or without high-risk HPV.

CONCLUSION

GSTT1 null genotype in cervical cell samples may be associated with more severe precancerous lesions of the cervix in a Japanese population. The p53 codon 72 polymorphism is unlikely to be related to HPV status and the onset of cervical cancer.

Females with paired occurrence of cancers in the UADT and genital region have a higher frequency of either Glutathione S-transferase M1/T1 null genotype

Upper Aero digestive Tract (UADT) is the commonest site for the development of second cancer in females after primary cervical cancer. Glutathione S-transferase (GSTM1 and / or T1) null genotype modulates the risk of developing UADT cancer (primary as well as second cancer). The aim of this study was to evaluate the difference in GST null genotype frequencies in females with paired cancers in the UADT and genital region as compared to females with paired cancers in the UADT and non-genital region. Forty-nine females with a cancer in the UADT and another cancer (at all sites-genital and non-genital) were identified from a database of patients with multiple primary neoplasms and were analyzed for the GSTM1 and T1 genotype in addition to known factors such as age, tobacco habits, alcohol habits and family history of cancer. Frequencies of GSTM1 null, GSTT1 null, and either GSTM1/T1 null were higher in females with paired occurrence of cancer in the UADT and genital site (54%, 33% and 75% respectively) in comparison to females with paired occurrence of cancer in the UADT and non-genital sites (22%, 6% and 24% respectively). The significantly higher inherited frequency of either GSTM1/T1 null genotype in females with a paired occurrence of cancers in UADT and genital region (p = 0.01), suggests that these females are more susceptible to damage by carcinogens as compared to females who have UADT cancers in association with cancers at non-genital sites.

Genetic polymorphisms of GSTM1, p21, p53 and HPV infection with cervical cancer in Korean women

OBJECTIVES

The aim of this study was to determine whether GSTM1 or GSTT1 might be associated with risk of cervical cancer development in Korean women. The multiplicative interaction of GSTM1 and GSTT1 genotype with p21, p53 polymorphism, and HPV genotype was also investigated.

METHODS

From 1997 to 1999, uterine cervical carcinoma was diagnosed in 215 Korean women at the Department of Obstetrics and Gynecology of Seoul National University Hospital. None of the women in the control groups (n = 98) had any evidence of cervical lesions, which were confirmed by Pap smear. Finally, 81 cases and 86 controls were genotyped for p21, p53, and GSTM1 and T1 and HPV infection. A multiplex PCR method was used for the genotyping of GSTM1 and GSTT1; direct sequencing for p53 codon 72, high-risk HPV, and PCR-RFLP (BsmAI) for p21 codon. The unconditional logistic regression analysis was used to calculate ORs and 95% CI.

RESULTS

Although the GSTM1 and GSTT1 genotype was not significantly associated with cervical cancer development for all women, the GSTM1 null genotype was significantly associated with an increased risk of cervical cancer development in women with high-risk HPV infection (OR = 2.9, 95% CI: 1.0-8.2). Although the frequency of overall GSTT1 null genotype was significantly lower in cervical carcinoma patients with high-risk HPV infection (OR = 0.3, 95% CI: 0.1-1.0), almost 2-fold increased risk was observed among women with GSTT1 null and Arg/Arg genotype (OR = 1.9, 95% CI: 0.7-5.4). Although the cervical cancer risk was 3.3-fold increased in women with null and Arg/Arg genotype compared to women with GSTM1 present and p21 Ser-containing genotype, there was no significant multiplicative interaction between GSTM1 and p21 (P for interaction = 0.785) or p53 (P for interaction = 0.815).

CONCLUSIONS

These findings suggest that the risk of cervical cancer may be related to GSTM1 genotype in women with high-risk HPV infection and that there is a possible gene-gene interaction in the incidence of cervical cancer.

Familial cervical cancer: case reports, review and clinical implications

We report three Dutch families with familial clustering of (pre)neoplastic cervical disease, review the literature on familial risks of cervical intraepithelial neoplasia (CIN) and cervical cancer, and discuss possible practical guidelines for women with a family history of cervical cancer. Daughters and sisters of women with cervical cancer have been reported to have a relative risk of 1.5-2.3 to develop this type of cancer. From a practical clinical point of view, we suggest that as in women with an increased non-genetic risk to develop cervical cancer (e.g. because of immunosuppressive therapy) increased surveillance to detect this tumour should be considered in women with an increased risk based on family history. Cessation of smoking should be advised. As the use of condoms at least prevents HPV re-infection its use can be recommended as a way to lower the cervical cancer risk. Future studies to determine the genetic contribution to the development of cervical cancer should include the paternal family history of cancer and, because genetic predisposition might express itself as a higher risk to develop precursors of cervical cancer, carcinoma in situ and CIN grade II-III.

Effect of epoxide hydrolase polymorphisms on chromosome aberrations and risk for lung cancer

Microsomal epoxide hydrolase (mEH) gene is polymorphic and its enzyme is involved in the activation and subsequent detoxification of several tobacco carcinogens, for example polycyclic aromatic hydrocarbons. Therefore, we have investigated the association of two polymorphisms at exons 3 and 4 of the mEH gene with the development of lung cancer in 110 patients and 119 matched controls. In addition, we have investigated the relationship between the different mEH alleles and the frequency of chromosome aberrations (CA), as an approach to understand the role of genetic susceptibility on cancer risk. Our results show that only the homozygous exon 4 fast genotype is significantly associated with increased risk for lung cancer (odds ratio [OR]=6.26; 95% confidence interval [CI]=1.02-38.3). When the exons 3 and 4 polymorphisms are considered together, patients carrying the high enzyme activity genotype have a significantly increased risk for lung cancer (OR=2.46; 95% CI=1.06-5.68). More importantly, the increased risk for this group is confirmed by their having the highest frequency of CA compared to any other genotype groups. In addition, genotypes with higher risk had consistently more CA than those with lower risk. Our CA data also indicates that the low activity genotype may exert a protective role in cigarette smokers, as it was associated with a significant decrease in CA compared to the high and intermediate activity genotypes. In conclusion, the CA data provides evidence to support that susceptibility mEH alleles are significantly involved with the development of lung cancer from cigarette smoking.

A population-based study of glutathione S-transferase M1, T1 and P1 genotypes and risk for lung cancer

A deletion polymorphism for glutathione S-transferase M1 (GSTM1) has been related to risk for lung cancer among smokers in some studies but not in others. We examined GSTM1, a GSTT1 deletion polymorphism and a common GSTP1 gene variant (iso-->val), as risk factors for lung cancer in a population-based case-control study of men. Cases (N=274) were males identified from 1993 to 1996 through the Fred Hutchinson Cancer Research Center Cancer Surveillance System registry for western Washington State. Male age-matched controls (N=501) were selected by random-digit dialing. Subjects participated in a telephone interview and blood draw. GSTM1 and GSTT1 were genotyped with a multiplex PCR assay using beta-globin as a positive control, and GSTP1 single nucleotide variant determined with PCR-based oligonucleotide ligation assays. GSTM1 absence was associated with a modest elevation in risk among all cases (odds ratio=1.27, 95% CI 0.91-1.77) and among non-small cell cancers (adenocarcinoma OR=1.58, 95% CI 0.99-2.52; squamous cell OR=1.40, 95% CI 0.83-2.34). Risk associated with GSTM1 null was increased two to sixfold among heavy smokers. GSTT1 was not associated with lung cancer risk and GSTP1 val was non-significantly associated with a modest reduction in risk, particularly among heavy smokers. No specific combination of GST genotypes was particularly associated with risk. These results support previous reports that the GSTM1 null genotype is associated with a modest increase in risk for lung cancer, particularly among heavy smokers, suggest no role for GSTT1 and the need for further study of GSTP1.

Polymorphisms for chemical metabolizing genes and risk for cervical neoplasia

Infection with high-risk human papillomavirus (HPV) plays a major role in the etiology of cervical cancer (CC). However, most infected women do not develop cancer. Therefore, exposure to other carcinogenic agents may be a contributing risk factor for CC. We investigated the hypothesis that environmental exposure to cigarette smoke and inheritance of polymorphic chemical metabolizing genes (CYP2E1, GSTM1, and mEH) significantly increase the risk for neoplasia. We selected 76 cases with high-grade cervical neoplasia or with invasive CC and 75 matched healthy controls. The collected data support the well-established observation that infection with high-risk HPV is the major risk factor for CC (OR = 75; 95% CI = 26-220). In addition, our data show that women who smoked more than 15 "pack-year" had a significant 6.9-fold increase in risk (95% CI = 1.2-40.3) after adjustment for HPV infection. The CYP2E1 variant genotype did not significantly increase the risk for neoplasia. A significant increase in risk for neoplasia was observed for the low-activity mEH 113 His allele after adjustment for smoking (OR = 3.0; 95% CI = 1.4-6.3). The GSTM1 null genotype was associated with a significant 3.3-fold increased risk for neoplasia (95% CI = 1.0-11.8) compared to women who were GSTM1-positive after adjustment for smoking and HPV infection. Our study suggests that genetic differences in the metabolism of cigarette smoke, particularly GSTM1, may confer susceptibility to CC. Further studies using larger populations will be needed to confirm our observations and to validate data for disease prevention.

Childhood acute lymphoblastic leukemia: genetic determinants of susceptibility and disease outcome

The origin of acute lymphoblastic leukemia (ALL), the most common pediatric cancer, can be explained by a combination of genetic factors and environmental exposure. The environmental toxicants to which an individual is exposed are biotransformed and eliminated from the body after metabolic conversion mediated by Phase I and Phase II xenobiotic-metabolizing enzymes. Phase I enzymes catalyze hydroxylation, reduction and oxidation reactions of xenobiotics (carcinogens/drugs), often converting them into more active or toxic compounds. Phase II enzymes catalyze conjugation reactions (glucuronidation, acetylation, methylation), thereby converting the metabolites into non-reactive, water-soluble products that are eliminated from the organism. The genetic polymorphism underlying the variation in enzyme activity can modify susceptibility to diverse adult cancers, probably by influencing the activation and removal of toxicants or drugs. Here we present an overview of the role of genetic variants of certain Phase I and Phase II enzymes in the development of childhood ALL, a good model for such studies because of its short latency period. The genetic contribution to the development of ALL is examined by association studies that analyze the loci of Phase I enzymes (cytochrome P-450, myeloperoxidase) and Phase II enzymes (quinone-oxidoreductase, glutathione-S-transferase, N-acetyltransferase). The loci of the enzyme variants CYPlA1, CYP2E1, NQO1, GSTM1, GSTP1, NAT2 are associated with disease development, and evidence of gene-gene interactions has emerged as well. Despite the improvements in treatment, resistant cases of ALL remain a leading cause of cancer-related death in children. Although the underlying mechanism of drug resistance is not well understood, differences in the capacity of ALL patients to process drugs and environmental carcinogens could play a role by modifying the risk of recurrent malignancy, as well as the response to therapy. Therefore, polymorphic genes encoding carcinogen- and drug-metabolizing enzymes may not only increase the risk of ALL but also influence the risk of relapse in patients. We found that the prognosis of patients with CYPlA1 and NQO1 variants was worse than that of patients who lack these variants. We conclude that genotyping ALL patients for functional polymorphisms of candidate genes can become an important tool in predicting disease outcome.

Increased risk for acute myeloid leukaemia in individuals with glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) gene defects

OBJECTIVES

Glutathione S-transferases (GST) modulate the effects of exposure to various cytotoxic and genotoxic agents, including those associated with increased risks of the myelodysplastic syndrome (MDS), acute myeloid leukaemia (AML) and aplastic anemia (AA). Both the GST mu 1 (GSTM1) and GST theta 1 (GSTT1) genes have a null variant allele in which the entire gene is absent. In this study, we tested whether null genotypes for the GSTM1 and GSTT1 genes altered the risks for MDS, AML and AA.

METHODS

Genomic DNA from 49 MDS, 38 AML and 37 AA patients and 276 controls was analysed using the polymerase chain reaction (PCR).

RESULTS

The frequencies of GSTM1 (73.6%) and GSTT1 (34.2%) null genotypes were significantly higher in AML patients than in the controls (36.9 and 18.1%, respectively). A higher frequency of the combined null genotype for both genes was also observed in patients with AML (26.3% compared with 5.0% in the controls). In contrast, no differences in the frequencies of the null genotypes were found among MDS patients, AA patients and the controls.

CONCLUSION

Our observation of a 4.7-fold (95% CI: 2.1-11.0) and 2.3-fold (95% CI: 1.0-5.2) increased risk associated with the GSTM1 and GSTT1 null genotypes, respectively, and a 6.6-fold (95% CI: 2.4-7.9) increased risk associated with the combined null genotype presents preliminary evidence that the inherited absence of this carcinogen detoxification pathway may be an important determinant of AML.

CYP1A1, GSTM1, and GSTT1 polymorphisms and the risk of cervical squamous intraepithelial lesions in a multiethnic population

OBJECTIVE

In this investigation, we explored the hypothesis that genetic polymorphisms in the cytochrome P4501A1 (T3801C) and glutathione S-transferase classes mu and theta (GSTM1 and GSTT1) gene deletions promote the development of cervical dysplasia by moderating the activation and detoxification of polycyclic hydrocarbons and other compounds that influence oxidative stress and DNA adduct formation.

METHODS

A multiethnic, case-control study of 131 women with biopsy-confirmed cervical squamous intraepithelial lesions (SIL) and 180 controls with cytologically normal cervical (Pap) smears was conducted between 1992 and 1996 in Honolulu, Hawaii. We collected in-person interviews, a blood sample to extract genomic DNA, and an exfoliated cervical cell sample to determine the presence and type of human papillomavirus (HPV) using PCR dot-blot hybridization. Genotyping for the CYP1A1 MspI allelic variant and deletion of the GSTM1 and GSTT1 gene loci followed a PCR method.

RESULTS

Women who were homozygous, but not heterozygous, for the CYP1A1 MspI variant allele were at significantly increased risk of cervical SIL (odds ratio (OR) = 3.4; 95% confidence interval (CI) = 1.1-10.7) compared to women who were homozygous for the wild-type allele. Subjects with the GSTM1 null genotype had a nonsignificant elevated risk of cervical SIL (OR = 1.6; 95% CI = 0.8-3.0) compared to women with the gene present. No difference in the risk of cervical disease was associated with the GSTT1 null genotype. The combination of the CYP1A1 homozygous variant and the GSTM1 null genotypes increased the odds ratio for cervical SIL to 5.1 (95% CI = 1.3-20.7). There was no evidence for an interaction between genotype and exposure to tobacco smoke, alcohol drinking, or HPV DNA positivity.

CONCLUSIONS

These findings, although based on a small number of subjects, suggest that the CYP1A1 MspI polymorphism may be a susceptibility factor for early, premalignant changes in the cervical epithelium.

Advances in molecular toxicology-towards understanding idiosyncratic drug toxicity

Idiosyncratic drug toxicity is a major complication of drug therapy and drug development. Such adverse drug reactions (ADRs) include anaphylaxis, blood dyscrasias, hepatotoxicity and severe cutaneous reactions. They are usually serious and can be fatal. At present, prediction of idiosyncratic ADRs at the preclinical stage of drug development is not possible because there are no suitable animal models and we do not understand the basic mechanisms involved in the toxicity when it does occur in man. Many idiosyncratic reactions appear to have an immunological aetiology. For example, there is increasing evidence for the role of T lymphocytes in severe skin reactions. Nevertheless, the sequence of events by which a simple chemical can elicit severe tissue damage remains poorly understood and alternative novel mechanisms of toxicity must also be explored. The purpose of this article will be to review the currently accepted mechanisms of idiosyncratic drug toxicity at the chemical and the molecular levels. In particular, we will consider how recent advances in cellular immunology and molecular biology can improve our understanding of both the chemical and clinical aspects of drug hypersensitivity. Recent advances in the role of both inter- and intra-cellular signalling in the regulation of the immune response to drugs and their metabolites will be discussed. The long-term aim of such research is to provide test systems for the evaluation of drug safety and patient susceptibility to idiosyncratic drug toxicity.

Mammalian class theta GST and differential susceptibility to carcinogens: a review

Glutathione S-transferases (GSTs) are an important part of the cellular detoxification system and, perhaps, evolved to protect cells against reactive oxygen metabolites. Theta is considered the most ancient among the GSTs and theta-like GSTs are found in mammals, fish, insects, plants, unicellular algae, and bacteria. It is thought that an ancestral theta-gene underwent an early duplication before the divergence of fungi and animals and further duplications generated the variety of the other classes of GSTs (alpha, mu, phi, etc.). The comparison of the aminoacidic homologies among mammals suggests that a duplication of an ancient GST theta occurred before the speciation of mammals and resulted in the subunits GSTT1 and GSTT2. The ancestral GST theta has a dehalogenase activity towards several halogenated compounds, such as the dichloromethane. In fact, some aerobic and anaerobic methylotrophic bacteria can use these molecules as the sole carbon and energy source. The mammalian GST theta cannot sustain the growth of bacteria but still retains the dehalogenating activity. Therefore, although mammalian GST theta behaves as a scavenger towards electrophiles, such as epoxides, it acts also as metabolic activator for halogenated compounds, producing a variety of intermediates potentially dangerous for DNA and cells. For example, mice exposed to dichloromethane show a dose-dependent incidence of cancer via the GSTT1-1 pathway. Because GSTT1-1 is polymorphic in humans, with about 20% of Caucasians and 80% of Asians lacking the enzyme, the relationship between the phenotype and the incidence of cancer has been investigated extensively in order to detect GSTT1-1-associated differential susceptibility towards endogenous or exogenous carcinogens. The lack of the enzyme is related to a slightly increased risk of cancer of the bladder, gastro-intestinal tract, and for tobacco-related tumors (lung or oral cavity). More pronounced risks were found in males with the GSTT1-null genotype for brain diseases and skin basal cell carcinomas not related to sunlight exposures. Moreover, there was an increased risk of kidney and liver tumors in humans with the GSTT1-1 positive genotype following exposures to halogenated solvents. Interestingly, the liver and kidney are two organs that express the highest level of GST theta in the human body. Thus, the GSTT1-1 genotype is suspected to confer decreased or increased risk of cancer in relation to the source of exposure; in vitro studies, mostly conducted on metabolites of butadiene, confirm the protective action of GSTT1-1, whereas, thus far, experimental studies prove that the increasing risk is limited.

Combined analysis of germline polymorphisms of p53, GSTM1, GSTT1, CYP1A1, and CYP2E1: relation to the incidence rate of cervical carcinoma

BACKGROUND

The authors established the genotype frequencies of cytochrome P450 (CYP1A1/MspI, CYP2E1/PstI, and CYP2E1/DraI), glutathione-S-transferase (GSTM1 and GSTT1), and p53 (exon 4/AcclI and intron 3/16-base pair duplication) gene polymorphisms in cervical carcinoma patients and controls and evaluated the association between the specific genotype or genotype combinations of these polymorphisms and the risk of cervical carcinoma.

METHODS

In this case-control study, the genotypes of 181 human papillomavirus (HPV)-16 or HPV-18 positive cervical carcinoma patients and 1-to-1 age-matched controls were determined using a polymerase chain reaction-based technique.

RESULTS

Among these polymorphisms, the individuals carrying arginine/proline genotypes of p53 showed a 9.5-fold increase of cervical carcinoma risk (95% confidence interval [CI], 4.9-18.6) compared with those individuals carrying arginine/arginine genotypes. The frequency of overall GSTT1 null genotypes also was significantly higher in cervical carcinoma patients compared with that of GSTT1 positive genotypes (P = 0.003; odds ratio [OR] = 1.9; 95% CI, 1.2-2.9). The genotype combination of p53 and GST played a more important role in describing the relative risk of cervical carcinoma. The individuals carrying both the arginine/proline genotype of p53 and the null genotype of GSTT1 showed a 3.5-fold increase of cervical carcinoma risk (95% CI, 1.8-7.1) compared with those individuals carrying both the arginine/arginine genotype of p53 and the GSTT1 positive genotype. In the patients who were stratified into the two age groups, the null genotypes of GSTT1 (69.1% vs. 45.5%; P = 0.016) and GSTM1 (61.8% vs. 40.0%; P = 0.028) in cervical carcinoma were significantly overrepresented in the younger age subgroup (age 40 years or younger) compared with those of controls. Especially in this age group, the individuals carrying both null genotypes of GSTT1 and GSTM1 showed a 17.8-fold increase of cervical carcinoma risk (95% CI, 2.2-141.0) compared with the individuals carrying both positive genotypes of GSTT1 and GSTM1.

CONCLUSIONS

The results of the current study suggested that the arginine/proline genotype of p53, independently or in conjunction with the GSTT1 null genotype, could affect the genetic susceptibility for cervical carcinoma, and HPV positive women carrying both null genotypes of GSTT1 and GSTM1 have an increased risk of cervical carcinoma developing before age 40 years.

Glutathione S-transferase genotypes in children who develop treatment-related acute myeloid malignancies

Epipodophyllotoxin-associated secondary myeloid leukemia is a devastating complication of acute lymphoblastic leukemia (ALL) therapy. The risk factors for treatment-related myeloid leukemia remain incompletely defined. Genetic deficiencies in glutathione S-transferase (GST) activities have been linked to higher frequencies of a number of human malignancies. Our objective was to determine whether the null genotype for GSTM1, GSTT1, or both, was more frequent in children with ALL who developed treatment-related myeloid malignancies as compared to those who did not. A PCR technique was used to assay for the null genotype for GSTM1 and GSTT1 in 302 children with ALL, 57 of whom also subsequently developed treatment-related acute myeloid leukemia or myelodysplastic syndrome. Among children with ALL who did not develop treatment-related myeloid malignancies, the frequencies of GSTM1 and GSTT1 wild-type, GSTM1 null-GSTT1 wild-type, GSTM1 wild-type-GSTT1 null, and GSTM1 and GSTT1 null genotypes were 40%, 42%, 9% and 9%, respectively. The corresponding frequencies for patients who developed acute myeloid malignancies were 42%, 32%, 11% and 16%, respectively (P = 0.26). A statistically significant increase in the frequency of the GST null genotype was observed in male patients who developed myeloid malignancies as compared to male ALL control patients (P = 0.036), but was not observed in female patients (P = 0.51). Moreover, a logistic regression analysis of possible predictors for myeloid malignancies, controlling for gender and race, did not reveal an association of GSTM1 or GSTT1 null genotypes (P = 0.62 and 0.11, respectively) with treatment-related malignancies. Our data suggest that GSTM1 and GSTT1 null genotypes may not predispose to epipodophyllotoxin-associated myeloid malignancies.

Detoxifying enzyme genotypes and susceptibility to cutaneous malignancy

While ultraviolet (UV) exposure is thought to be a major risk factor for basal cell carcinoma (BCC) and squamous cell carcinoma, more recent research has focused on genetic factors predisposing to these cancers. UV constitutes an oxidative stress with generation of free radicals, leading to lipid and DNA damage and gene mutation. It could therefore be hypothesized that individual ability to deal with these products may be important in cutaneous carcinogenesis. It is clear from recent studies that polymorphisms in detoxifying enzyme genes are important in determining susceptibility to skin cancer. The magnitude of effect in BCC is similar to that seen with many other previously described risk factors. However, uncertainties exist regarding the phenotypic consequences of some of these polymorphisms and relevant substrates. This review describes the influence of polymorphisms in detoxifying enzymes in determining susceptibility to skin cancer (in particular to BCC) and give a brief overview of the biochemistry of the detoxification process.

Susceptibility to Childhood Acute Lymphoblastic Leukemia: Influence of CYP1A1, CYP2D6, GSTM1, and GSTT1 Genetic Polymorphisms

Although acute lymphoblastic leukemia (ALL) is the most common childhood cancer, factors governing susceptibility to this disease have not yet been identified. As such, ALL offers a useful opportunity to examine the glutathione S-transferase and cytochrome P450 genes in determining susceptibility to pediatric cancers. Both enzymes are involved in carcinogen metabolism and have been shown to influence the risk a variety of solid tumors in adults. To determine whether these genes played a similar role in childhood leukemogenesis, we compared the allele frequencies of 177 childhood ALL patients and 304 controls for the CYP1A1, CYP2D6, GSTM1, and GSTT1 genes. We chose the French population of Quebec as our study population because of its relative genetic homogeneity. The GSTM1 null and CYP1A1*2A genotypes were both found to be significant predictors of ALL risk (odds ratio [OR] = 1.8). Those possessing both genotypes were at an even greater risk of developing the disease (OR = 3.3). None of the other alleles tested for proved to be significant indicators of ALL risk. Unexpectedly, girls carrying the CYP1A1∗4 were significantly underrepresented in the ALL group (OR = 0.2), suggesting that a gender-specific protective role exists for this allele. These results suggest that the risk of ALL may indeed be associated with xenobiotics-metabolism, and thus with environmental exposures. Our findings may also explain, in part, why ALL is more prevalent among males than females.

Susceptibility to Childhood Acute Lymphoblastic Leukemia: Influence of CYP1A1, CYP2D6, GSTM1, and GSTT1 Genetic Polymorphisms

Although acute lymphoblastic leukemia (ALL) is the most common childhood cancer, factors governing susceptibility to this disease have not yet been identified. As such, ALL offers a useful opportunity to examine the glutathione S-transferase and cytochrome P450 genes in determining susceptibility to pediatric cancers. Both enzymes are involved in carcinogen metabolism and have been shown to influence the risk a variety of solid tumors in adults. To determine whether these genes played a similar role in childhood leukemogenesis, we compared the allele frequencies of 177 childhood ALL patients and 304 controls for the CYP1A1, CYP2D6, GSTM1, and GSTT1 genes. We chose the French population of Quebec as our study population because of its relative genetic homogeneity. The GSTM1 null and CYP1A1*2A genotypes were both found to be significant predictors of ALL risk (odds ratio [OR] = 1.8). Those possessing both genotypes were at an even greater risk of developing the disease (OR = 3.3). None of the other alleles tested for proved to be significant indicators of ALL risk. Unexpectedly, girls carrying the CYP1A1∗4 were significantly underrepresented in the ALL group (OR = 0.2), suggesting that a gender-specific protective role exists for this allele. These results suggest that the risk of ALL may indeed be associated with xenobiotics-metabolism, and thus with environmental exposures. Our findings may also explain, in part, why ALL is more prevalent among males than females.

Polymorphisms of N-acetyltransferases, glutathione S-transferases, microsomal epoxide hydrolase and sulfotransferases: influence on cancer susceptibility

It has become clear that several polymorphisms of human drug-metabolizing enzymes influence an individual's susceptibility for chemical carcinogenesis. This review gives an overview on relevant polymorphisms of four families of drug-metabolizing enzymes. Rapid acetylators (with respect to N-acetyltransferase NAT2) were shown to have an increased risk of colon cancer, but a decreased risk of bladder cancer. In addition an association between a NAT1 variant allele (NAT*10, due to mutations in the polyadenylation site causing approximately two fold higher activity) and colorectal cancer among NAT2 rapid acetylators was observed, suggesting a possible interaction between NAT1 and NAT2. Glutathione S-transferases M1 and T1 (GSTM1 and GSTT1) are polymorphic due to large deletions in the structural gene. Meta-analysis of 12 case-control studies demonstrated a significant association between the homozygous deletion of GSTM1 (GSTM1-0) and lung cancer (odds ratio: 1.41; 95% CI: 1.23-1.61). Combination of GSTM1-0 with two allelic variants of cytochrome P4501A1 (CYP1A1), CYP1A1 m2/m2 and CYP1A1 Val/Val further increases the risk for lung cancer. Indirect mechanisms by which deletion of GSTM1 increases risk for lung cancer may include GSTM1-0 associated decreased expression of GST M3 and increased activity of CYP1A1 and 1A2. Combination of GST M1-0 and NAT2 slow acetylation was associated with markedly increased risk for lung cancer (odds ratio: 7.8; 95% CI: 1.4-78.7). In addition GSTM1-0 is clearly associated with bladder cancer and possibly also with colorectal, hepatocellular, gastric, esophageal (interaction with CYP1A1), head and neck as well as cutaneous cancer. In individuals with the GSTT1-0 genotype more chromosomal aberrations and sister chromatid exchanges (SCEs) were observed after exposure to 1,3-butadiene or various haloalkanes or haloalkenes. Evidence for an association between GSTT1-0 and myelodysplastic syndrome and acute lymphoblastic leukemia has been presented. A polymorphic site of GSTP1 (valine to isoleucine at codon 104) decreases activity to several carcinogenic diol epoxides and was associated with testicular, bladder and lung cancer. Microsomal expoxide hydrolase (mEH) is polymorphic due to amino acid variation at residues 113 and 139. Polymorphic variants of mEH were associated with hepatocellular cancer (His-113 allele), ovarian cancer (Tyr-113 allele) and chronic obstructive pulmonary disease (His-113 allele). Three human sulfotransferases (STs) are regulated by genetic polymorphisms (hDHEAST, hM-PST, TS PST). Since a large number of environmental mutagens are activated by STs an association with human cancer risk might be expected.

Concordance between enzyme activity and genotype of glutathione S-transferase theta (GSTT1)

Blood samples from 140 healthy German volunteers were used to further characterize the genetic polymorphism of the human theta class glutathione S-transferase 1 (GSTT1). For measurements of GSTT1 activity, hemolysates were incubated in vitro with different concentrations of dichloromethane. The resulting enzymatically mediated production of formaldehyde was determined colorimetrically by the Nash reaction. GSTT1 genotyping was performed by polymerase chain reaction (PCR) methods using genomic DNA from total white blood cells. The prevalence of homozygous deletion of the GSTT1 gene was 19.3% (95% confidence limits: 12.2-27.7%). There was a high agreement between genotyping and phenotyping data. The individuals with the null genotype had a rate of formaldehyde production below the limit of quantification. In addition, in the group of GSTT1-positive individuals, we could differentiate highly active people (35.7%) from individuals with an intermediate enzyme activity (45.0%). It can be concluded that the PCR method is suitable to quickly genotype large populations, whereas the phenotyping assay at present offers the advantage of differentiating heterozygously from homozygously active subjects. Our results confirm the ethnic differences in the prevalence of the homozygous deleted genotype which were previously observed and seem to exist even between closely related ethnic groups such as German and Swedish populations.

Putative susceptibility markers of coronary artery disease: association between VDR genotype, smoking, and aromatic DNA adduct levels in human right atrial tissue

Cancer and cardiovascular diseases share risk factors such as smoking, and the onset of both diseases have been suggested to have a common mechanistic basis. The binding of carcinogens to DNA (carcinogen-DNA adducts), genetic polymorphisms in carcinogen-detoxifying enzymes glutathione S-transferases (GSTs), and genetic polymorphisms in the vitamin D receptor (VDR) are among the candidates for modifiers of cancer risk. We determined whether these biomarkers could be related to individual characteristics of patients suffering from cardiovascular diseases. For that purpose, DNA from the right atrial appendage of 41 patients who underwent open heart surgery was analyzed for smoking-related DNA adducts and polymorphisms in GSTM1, GSTT1, and VDR genes. Statistical analysis was used to identify any patient's characteristics associated with these molecular markers. Our results showed that heart tissue of cigarette smokers contained a variety of aromatic DNA adducts in significantly elevated levels compared to ex-smokers (P<0.01) or nonsmokers (P<0.001). A linear relationship was observed between DNA adduct levels and daily cigarette smoking (rs=0.73; P=0.0003). Since cardiac myocytes are terminally differentiated cells that have lost their ability to divide and seemingly have limited DNA repair capacities, their levels might accumulate with time and thereby affect heart cell function or viability. Substantial interindividual differences between DNA adduct levels were observed, and persons with severe coronary artery disease (CAD), as assessed by coronary angiography, had higher DNA adduct levels than persons with no or mild CAD (P=0.04). As polymorphisms in GST genes have been shown to modulate DNA adduct levels and risk for lung cancer in smokers, we explored for the first time whether the GST polymorphisms could also explain deviating heart DNA adduct levels and CAD risk. However, no relation could be found between these covariants. In contrast, a VDR genotype, which has been associated with decreased serum levels of the active hormonal form of vitamin D and increased risk for certain cancers, seemed to be related to severity of CAD (P=0.025). Our findings support the hypothesis that smoking-related DNA damage may be involved in the onset of cardiovascular diseases and suggest that VDR genotype may be a useful susceptibility marker of CAD.

Prevalence of homozygosity for the deleted alleles of glutathione S-transferase mu (GSTM1) and theta (GSTT1) among distinct ethnic groups from Brazil: relevance to environmental carcinogenesis?

Environmental related diseases due to occupational carcinogens and toxic substances are a serious problem particularly in developing countries. The glutathione S-transferase system is fundamental for the detoxification of numerous carcinogens and mutagens. The individual inherited susceptibility to chemical carcinogenesis due to glutathione S-transferase mu (GSTM1) and theta (GSTT1) varies significantly among distinct ethnic groups. In this study we determined the prevalence of the null genotype of the GSTM1 and GSTT1 genes among individuals from three distinct Brazilian racial groups using a multiplex-PCR methodology. The results showed that the highest prevalence of the null genotype for the GSTM1 occurred among Caucasians (55%, allele frequency = 0.74), followed by 33% among Brazilian Black subjects (allele frequency = 0.57), and 20% among Amazonian Indians (allele frequency = 0.45). For GSTT1 a homogenous distribution of the null genotype was found among Caucasian and African descendants (18.5 and 19% homozygotes, respectively, allele frequency = 0.43), with a lower prevalence among Amazonian Indians (11% of homozygotes, allele frequency = 0.34). Whether the deficiency of the GST system contributes to a predisposition to environmental related carcinogenesis in specific populations in Brazil remains to be determined.

Higher Frequency of Glutathione S-Transferase Deletions in Black Children With Acute Lymphoblastic Leukemia

The genetic polymorphisms in human glutathione S-transferases (GST) M1 and T1 have been associated with race, disease risk, and outcome of some adult cancers. Also, there are racial differences in the incidence and characteristics of childhood acute lymphoblastic leukemia (ALL). Our objectives were to compare the frequency of the null genotype for GSTM1, GSTT1, or both in children with ALL to that in healthy controls, and to determine whether GST genotype was associated with treatment outcome and prognostic factors. We studied GSTM1 and GSTT1 genotypes in somatic cell DNA from black children and white children with ALL and in 416 healthy controls, using a polymerase chain reaction technique. Ninety of 163 (55.2%) white ALL patients and 14 of 34 (41.2%) black patients were GSTM1 null, frequencies not significantly different (P = .19) than healthy controls (53.5% in whites and 27.6% in blacks), although there was a trend toward more null genotypes in black ALL patients. Twenty-three of 163 (14.1%) white ALL patients and 12 of 34 (35.3%) black ALL patients were GSTT1 null, not different (P = .34) than the frequencies in healthy controls (15.0% in whites and 24.1% in blacks). However, the frequency of the “double-null” genotype, lacking both GSTM1 and GSTT1, was higher in black patients with ALL (8 of 34 or 23.5%) than in black controls (3.9%) (P = .0005), but this was not the case in white patients with ALL (10 of 163 or 6.1%) compared to white controls (8.0%) (P = .68). In stratified analyses, the GST double-null genotype was not associated with other characteristics that might differ between whites and blacks with ALL, such as age, T-lineage immunophenotype, presenting white blood cell count, DNA index, or insurance status. The null genotype for GSTM1, GSTT1, or both was not found to be a prognostic factor for disease-free survival or probability of hematologic remission; central nervous system relapse tended to be less common in those with the GSTM1 null genotype (P = .054) . The double-null genotype for GSTM1 and GSTT1 is more common among blacks but not whites with childhood ALL. These data suggest that GST genotype, coupled with unidentified additional risk factors, may play a role in risk of childhood ALL in American blacks.

Higher Frequency of Glutathione S-Transferase Deletions in Black Children With Acute Lymphoblastic Leukemia

The genetic polymorphisms in human glutathione S-transferases (GST) M1 and T1 have been associated with race, disease risk, and outcome of some adult cancers. Also, there are racial differences in the incidence and characteristics of childhood acute lymphoblastic leukemia (ALL). Our objectives were to compare the frequency of the null genotype for GSTM1, GSTT1, or both in children with ALL to that in healthy controls, and to determine whether GST genotype was associated with treatment outcome and prognostic factors. We studied GSTM1 and GSTT1 genotypes in somatic cell DNA from black children and white children with ALL and in 416 healthy controls, using a polymerase chain reaction technique. Ninety of 163 (55.2%) white ALL patients and 14 of 34 (41.2%) black patients were GSTM1 null, frequencies not significantly different (P = .19) than healthy controls (53.5% in whites and 27.6% in blacks), although there was a trend toward more null genotypes in black ALL patients. Twenty-three of 163 (14.1%) white ALL patients and 12 of 34 (35.3%) black ALL patients were GSTT1 null, not different (P = .34) than the frequencies in healthy controls (15.0% in whites and 24.1% in blacks). However, the frequency of the “double-null” genotype, lacking both GSTM1 and GSTT1, was higher in black patients with ALL (8 of 34 or 23.5%) than in black controls (3.9%) (P = .0005), but this was not the case in white patients with ALL (10 of 163 or 6.1%) compared to white controls (8.0%) (P = .68). In stratified analyses, the GST double-null genotype was not associated with other characteristics that might differ between whites and blacks with ALL, such as age, T-lineage immunophenotype, presenting white blood cell count, DNA index, or insurance status. The null genotype for GSTM1, GSTT1, or both was not found to be a prognostic factor for disease-free survival or probability of hematologic remission; central nervous system relapse tended to be less common in those with the GSTM1 null genotype (P = .054) . The double-null genotype for GSTM1 and GSTT1 is more common among blacks but not whites with childhood ALL. These data suggest that GST genotype, coupled with unidentified additional risk factors, may play a role in risk of childhood ALL in American blacks.

Genetic polymorphisms in human drug-metabolizing enzymes: potential uses of reverse genetics to identify genes of toxicological relevance

The human mind was engaged with fundamental questions on the nature of heredity long before the study of genetics became a scientific discipline. Many traits, such as height, eye color, blood pressure, or cancer susceptibility, have been known to run in families, although the genes or combination of genes that underlie these observable characteristics remain unknown in most cases. Differences in susceptibility to environmental agents in humans are likewise determined by variations in genetic background--genetic polymorphisms. In this article, we review the current status of studies on human polymorphisms in drug-metabolizing enzymes and discuss various approaches to the analysis of genetic polymorphisms. We expect that in the near future, novel methods in genetic analysis of human populations will be likely to play a key role in the identification of genes of toxicological relevance.

Cytochrome P450 2D6 and glutathione S-transferase genotype in sudden infant death syndrome

OBJECTIVES

The risk of sudden infant death syndrome (SIDS) has been linked with xenobiotic exposures, race and inheritance. Because cytochrome P450 2D6 (CYP2D6) and glutathione S-transferases (GSTM1 and GSTT1) are genetically regulated, polymorphically distributed, and responsible for detoxification of many centrally acting exogenous and endogenous bioactive compounds, our objective was to determine whether the prevalences of deficiencies in CYP2D6, GSTM1, and GSTT1 differ in SIDS victims compared to healthy controls.

METHODS

CYP2D6 mutations (deletion, A, B, and T alleles) and GSTM1 and GSTT1 null genotypes were assessed in DNA from 50 SIDS victims. CYP2D6 phenotype, assigned using dextromethorphan urinary ratios, was assessed in 25 unrelated parents of SIDS victims.

RESULTS

The CYP2D6B mutation was the only mutant CYP2D6 allele found in SIDS victims, present in 26.2% of patients (11/42) and 13.1% (11/84) of alleles. Adjusting for race, the prevalence of wild-type CYP2D6 alleles and of homozygous wild-type CYP2D6 phenotype was not different in SIDS victims compared to controls (P = 0.585 and 0.224, respectively). Among the 25 parents of SIDS victims, all subjects were extensive metabolizers, a prevalence not different from controls (P = 0.243). The prevalence of the null genotype for GSTM1, GSTT1 and double-null for GSTM1 and GSTT1 was 33.3%, 21.4% and 9.5%, respectively, among SIDS victims, and was not different than controls (P = 0.61, 0.1, 0.28, respectively). The combination of CYP2D6 homozygous wild-type genotype and the null genotype for GSTM1, GSTT1, or both GSTM1 + GSTT1 also did not differ in SIDS victims and controls.

CONCLUSIONS

The frequencies of CYP2D6 mutant genotypes and the null genotypes for GSTM1 and GSTT1 were not different among SIDS victims compared to normal controls, and thus these polymorphisms are unlikely to identify families with a high risk of SIDS.

Susceptibility to endometrial cancer: influence of allelism at p53, glutathione S-transferase (GSTM1 and GSTT1) and cytochrome P-450 (CYP1A1) loci

A case-control study was designed to identify associations between polymorphisms at p53, cytochrome P-450 (CYP1A1) and glutathione-S-transferases and endometrial cancer susceptibility. Among all polymorphisms analysed, an insertional variant in p53 (P53PIN3) and two polymorphisms in the 3'-end and exon 7 of CYP1A1 showed significant association with enhanced endometrial cancer risk.

Glutathione S-transferase and cytochrome-P-450 polymorphism as risk factors for squamous cell carcinoma of the larynx

PURPOSE

While cigarette smoking and alcohol consumption are recognized covariates for laryngeal carcinoma, the role of genetic factors in determining individual susceptibility is unknown. We describe the influence of polymorphism in carcinogen-metabolizing enzymes on susceptibility to squamous cell carcinoma of the larynx.

MATERIAL AND METHODS

We investigated 269 patients with T1-T4 laryngeal carcinoma and 216 controls. Enzyme genotypes at the glutathione-S-transferase GSTM1 (A, B, A/B, null), GSTM3 (A, B), GSTT1 (null and expressors), and cytochrome P-450, CYP2D6 (intron 3/exon 4 boundary mutation and exon 5 deletion), CYP1A1 (3'-mutation and exon 7 mutation), and CYP2E1 (mutation at the 5' flanking region) loci were determined using polymerase chain reaction and restriction-based approaches.

RESULTS

While the frequencies of the heterozygote GSTM1 A/B and homocygote GSTM3 B/ B were statistically significantly lower in cases than controls, the frequency of the GSTT1 null genotype was higher in the cases than controls. Genotype frequencies of 123 patients suffering squamous cell carcinomas located at different sites within the upper aerodigestive tract showed no differences between cases and controls.

CONCLUSIONS

The data provide evidence that susceptibility to laryngeal carcinoma, but not pharyngeal carcinoma, is mediated by allelism at a number of loci encoding enzymes involved in the detoxification of electrophils derived from environmental pollution including cigarette smoke.

Modulating factors of individual sensitivity to diepoxybutane: sister chromatid exchanges induced in vitro in human lymphocytes

Spontaneous and diepoxybutane (DEB)-induced sister chromatid exchanges (SCEs) were examined in cultured peripheral lymphocytes (PBL) from 122 healthy donors. SCE-inducing activity under defined experimental conditions and individual sensitivity to genotoxic stress were assessed. SCE means distribution appeared asymmetrical, identifying about 22% of subjects characterized by a 'high-respondent' phenotype with more than 111 SCEs/cell. Confounding factors, such as smoking habit, wine and coffee consumption, work activity and hematological factors, showed a limited capacity to affect individual SCE responsiveness, however hemoglobin and uric acid seemed to antagonize DEB genotoxicity.

Purification and characterization of a recombinant human Theta-class glutathione transferase (GSTT2-2)

A cDNA encoding the human Theta-class glutathione transferase GSTT2-2 was expressed in Escherichia coli as a ubiquitin fusion protein. The co-translational removal of the ubiquitin by a cloned ubiquitin-specific protease, Ubp1, generates enzymically active GSTT2-2 without any additional N-terminal residues. The recombinant isoenzyme was purified to apparent homogeneity by DEAE anion-exchange, gel filtration, dye ligand chromatography and high resolution anion-exchange chromatography on Mono Q FPLC. The recombinant enzyme had significant activity with a range of substrates, including cumene hydroperoxide and 1-menapthyl sulphate. The activity of GSTT2-2 with a range of secondary lipid peroxidation products such as the trans,trans-alka-2,4-dienals and trans-alk-2-enals, as well as its glutathione peroxidase activity with organic hydroperoxides, suggest that it may play a significant role in protection against the products of lipid peroxidation.