Polymorphism in glutathione S-transferase loci as a risk factor for common cancers

Individual and combined effects of the GSTM1, GSTT1, and GSTP1 polymorphisms on leukemia risk: An updated meta-analysis

Background: Several meta-analyses have analyzed the association of GSTM1 present/null, GSTT1 present/null, and GSTP1 IIe105Val polymorphisms with leukemia risk. However, the results of these meta-analyses have been conflicting. Moreover, they did not evaluate the combined effects of the three aforementioned gene polymorphisms. Furthermore, they did not appraise the credibility of the positive results. Finally, many new studies have been published. Therefore, an updated meta-analysis was conducted.

Objectives: To further explore the relationship of the three aforementioned gene polymorphisms with leukemia risk.

Methods: The crude odds ratios (ORs) and 95% confidence intervals (CIs) were applied to evaluate the association of the individual and combined effects of the three aforementioned genes. Moreover, the false-positive report probability (FPRP) and Bayesian false discovery probability (BFDP) were applied to verify the credibility of these statistically significant associations.

Results: Overall, the individual GSTM1, GSTT1, and GSTP1 IIe105Val polymorphisms added leukemia risk. On combining GSTM1 and GSTT1, GSTM1 and GSTP1, and GSTT1 and GSTP1 polymorphisms, positive results were also observed. However, no significant association was observed between the combined effects of these three polymorphisms with leukemia risk in the overall analysis. Moreover, when only selecting Hardy–Weinberg equilibrium (HWE) and medium- and high-quality studies, we came to similar results. However, when the FPRP and BFDP values were applied to evaluate the credibility of positive results, the significant association was only observed for the GSTT1 null genotype with leukemia risk in Asians (BFDP = 0.367, FPRP = 0.009).

Conclusion: This study strongly suggests a significant increase in the risk of leukemia in Asians for the GSTT1 null genotype.

The Use of Biomarkers as Alternatives to Current Animal Tests on Food Chemicals

Recent developments in biomarkers relating to the interrelationship of diet, disease and health were surveyed. Most emphasis was placed on biomarkers of deleterious effects, since these are of greatest relevance to the subject of this review. The area of greatest activity was found to be that relating to biomarkers of mutagenic, genotoxic and carcinogenic effects. This is also one of the major areas of concern in considerations of the beneficial and deleterious effects of dietary components, and also the area in which regulatory testing requires studies of the longest duration. A degree of progress has also been made in the identification and development of biomarkers relating to certain classes of target organ toxicity. Biomarkers for other types of toxicity, such as immunotoxicity, neurotoxicity, reproductive toxicity and developmental toxicity, are less developed, and further investigation in these areas is required before a comprehensive biomarker strategy can be established. A criticism that recurs constantly in the biomarker literature is the lack of standardisation in the methods used, and the lack of reference standards for the purposes of validation and quality control. It is encouraging to note the growing acknowledgement of the need for validation of biomarkers and biomarker assays. Some validation studies have already been initiated. This review puts forward proposals for criteria to be used in biomarker validation. More discussion on this subject is required. It is concluded that the use of biomarkers can, in some cases, facilitate the implementation of the Three Rs with respect to the testing of food chemicals and studies on the effects of diet on health. The greatest potential is seen to be in the refinement of animal testing, in which biomarkers could serve as early and sensitive endpoints, in order to reduce the duration of the studies and also reduce the number of animals required. Biomarkers could also contribute to establishing a mechanistic basis for in vitro test systems and to facilitating their validation and acceptance. Finally, the increased information that could result from the incorporation of biomarker determinations into population studies could reduce the need for supplementary animal studies. This review makes a number of recommendations concerning the prioritisation of future activities on dietary biomarkers in relation to the Three Rs. It is emphasised, however, that further discussions will be required among toxicologists, epidemiologists and others researching the relationship between diet and health.

Effects of GST variants on the risk odds of hematological malignancy: A meta-analysis

BACKGROUND

Whether glutathione S-transferases (GST) polymorphisms influence the risk odds of hematological malignancy remains controversial. Therefore, we performed this meta-analysis to better analyze correlations between GST polymorphisms and hematological malignancy.

METHODS

Literature retrieve was conducted in PubMed, MEDLINE, and Embase. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Sixty-two studies were enrolled for analyses. Significant associations with hematological malignancy were observed for GSTM1 (P < 0.0001, OR = 1.25, 95% CI, 1.14-1.38), GSTP1 (P = 0.002, OR = 1.20, 95% CI, 1.07-1.34), and GSTT1 (P < 0.0001, OR = 1.57, 95% CI, 1.39-1.76) polymorphisms in overall analyses. Further subgroup analyses by ethnicity revealed that GSTM1 and GSTT1 polymorphisms were both significantly correlated with hematological malignancy in Caucasians, East Asians, and West Asians, whereas GSTP1 polymorphism was only significantly correlated with hematological malignancy in Caucasians and West Asians. When we stratified data according to type of disease, positive results were found for all investigated polymorphisms in patients with certain types of acute leukemia. Moreover, GSTP1 polymorphism was also found to be significantly associated with chronic leukemia and lymphoma.

CONCLUSIONS

Our findings indicated that GSTM1, GSTT1, and GSTP1 polymorphisms may serve as potential genetic biomarkers of hematological malignancy in certain ethnicities.

Effects of GST null genotypes on individual susceptibility to leukemia: A meta-analysis

BACKGROUND

Whether glutathione S-transferases (GST) null genotypes influence individual susceptibility to leukemia remains controversial. Thus, we performed this meta-analysis to better analyze potential influences of GST null genotypes on individual susceptibility to leukemia.

METHODS

Literature retrieve was conducted in PubMed, Web of Science and Embase. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Totally fifty-one studies were enrolled for analyses. Significant associations with elevated individual susceptibility to leukemia were detected for GSTM1 (p < .0001, OR = 1.28, 95%CI 1.16-1.41), GSTP1 (p = .003, OR = 1.22, 95%CI 1.07-1.40) and GSTT1 (p < .0001, OR = 1.53, 95%CI 1.35-1.74) null genotypes in overall analyses. Further subgroup analyses by type of disease revealed that GSTM1, GSTP1 and GSTT1 null genotypes were all significantly associated with elevated individual susceptibility to acute lymphoblastic leukemia, GSTM1 and GSTT1 null genotypes were significantly associated with elevated individual susceptibility to acute myeloid leukemia, and GSTT1 null genotype was also significantly associated with elevated individual susceptibility to chronic leukemia. When we stratified data according to ethnicity of participants, positive results were found for all investigated variants in Caucasians and West Asians. Additionally, GSTM1 null genotype was also significantly correlated with elevated individual susceptibility to leukemia in East Asians.

CONCLUSIONS

Our findings indicated that GSTM1, GSTT1 and GSTP1 null genotypes might serve as potential genetic biomarkers of leukemia in certain ethnicities.

A 6-bp Deletion Variant in a Novel Canine Glutathione-S-Transferase Gene (GSTT5) Leads to Loss of Enzyme Function

OBJECTIVES

Glutathione-S-transferases (GSTs) detoxify reactive xenobiotics, and defective GST gene polymorphisms increase cancer risk in humans. A low activity GST-theta variant was previously found in research beagles. The purpose of our study was to determine the molecular basis for this phenotype and its allele frequency in pet dogs.

METHODS

Banked livers from 45 dogs of various breeds were screened for low GST-theta activity by the substrate 1,2-dichloro-4-nitrobenzene (DCNB), and were genotyped for variants in a novel canine GST gene, GSTT5. Whole-genome sequences from 266 dogs were genotyped at one discovered variant GSTT5 locus.

RESULTS

Canine livers ranged 190-fold in GST-theta activities, and a GSTT5 exon coding variant 385_390delGACCAG (Asp129_Gln130del) was significantly associated with low activity (P < 0.0001) and a marked decrease in hepatic protein expression (P = 0.0026). Recombinant expression of variant GSTT5 led to a 92% decrease in Vmax for DCNB (P = 0.0095). The minor allele frequency (MAF) for 385_390delGACCAG was 0.144 in 45 dog livers, but was significantly higher in beagles (0.444) versus nonbeagles (0.007; P = 0.0004). The homozygous genotype was significantly over-represented in Pembroke Welsh corgis (P < 0.0001) based on available whole-genome sequence data.

CONCLUSIONS

An Asp129_Gln130del variant in canine GSTT5 is responsible for marked loss of GST-theta enzyme activity. This variant is significantly over-represented in purpose-bred laboratory beagles and in Pembroke Welsh corgis. Additional work will determine the prevalence of this variant among other purebred dogs, and will establish the substrate range of this polymorphic canine enzyme with respect to common environmental carcinogens.

Characterization of a low expression haplotype in canine glutathione S-transferase (GSTT1) and its prevalence in golden retrievers

Glutathione S-transferase-theta (GSTT1) is a carcinogen detoxification enzyme, and low activity variants are associated with lymphoma in humans. We recently found a variant in the 3' untranslated region (UTR) of canine GSTT1, *101_102insT, which was predicted to change miRNA binding and was found in 5 of 17 golden retriever (GR) dogs with lymphoma but none of 14 healthy GRs. The aim of this study was to determine whether this variant led to decreased GSTT1 expression and was a discernible risk factor for lymphoma within the GR breed. On resequencing, *101_102insT appeared to be in complete linkage disequilibrium with 3 additional 3'UTR variants, leading to the inferred haplotype *3T>C; *101_102insT; *190C>A; *203T>C. In canine livers that were heterozygous for this variant haplotype, GSTT1 protein expression was significantly lower compared to the reference haplotype (densitometry .40 vs .64, P = .022), and GSTT1 transcript levels by qPCR were also significantly lower (fold difference .52, P = .012), without evidence of substantial allelic expression imbalance. The variant haplotype led to >50% decrease in expression in vitro (.31 ± .07 vs .64 ± .19; P = .019). We found no significant difference in minor allele frequencies between 71 GR dogs with lymphoma (MAF .162) and 33 healthy age-matched controls (MAF .136, P = .69). Our results indicate that the variant GSTT1 3'UTR haplotype containing *101_102insT reduces gene expression, which could lead to impaired carcinogen detoxification, but was not a detectable risk factor for lymphoma in GR dogs.

AS3MT, GSTO, and PNP polymorphisms: impact on arsenic methylation and implications for disease susceptibility

BACKGROUND

Oral exposure to inorganic arsenic (iAs) is associated with adverse health effects. Epidemiological studies suggest differences in susceptibility to these health effects, possibly due to genotypic variation. Genetic polymorphisms in iAs metabolism could lead to increased susceptibility by altering urinary iAs metabolite concentrations.

OBJECTIVE

To examine the impact of genotypic polymorphisms on iAs metabolism.

METHODS

We screened 360 publications from PubMed and Web of Science for data on urinary mono- and dimethylated arsenic (MMA and DMA) percentages and polymorphic genes encoding proteins that are hypothesized to play roles in arsenic metabolism. The genes we examined were arsenic (+3) methyltransferase (AS3MT), glutathione-s-transferase omega (GSTO), and purine nucleoside phosphorylase (PNP). Relevant data were pooled to determine which polymorphisms are associated across studies with changes in urinary metabolite concentration.

RESULTS

In our review, AS3MT polymorphisms rs3740390, rs11191439, and rs11191453 were associated with statistically significant changes in percent urinary MMA. Studies of GSTO polymorphisms did not indicate statistically significant associations with methylation, and there are insufficient data on PNP polymorphisms to evaluate their impact on metabolism.

DISCUSSION

Collectively, these data support the hypothesis that AS3MT polymorphisms alter in vivo metabolite concentrations. Preliminary evidence suggests that AS3MT genetic polymorphisms may impact disease susceptibility. GSTO polymorphisms were not associated with iAs-associated health outcomes. Additional data are needed to evaluate the association between PNP polymorphisms and iAs-associated health outcomes. Delineation of these relationships may inform iAs mode(s) of action and the approach for evaluating low-dose health effects for iAs.

CONCLUSIONS

Genotype impacts urinary iAs metabolite concentrations and may be a potential mechanism for iAs-related disease susceptibility.

Glutathione-S-transferase M1 and T1 genes and gastric cancer: a case control study in North Indian population

BACKGROUND

Difference in the capacity of xenobiotic metabolising enzymes might be an important factor in genetic susceptibility to cancer.

METHODS

A case control study involving forty one gastric cancer patients and one hundred and thirty controls was carried out to determine the frequency of GSTM1 and GSTT1 null genotypes. The frequency of GSTM1 and GSTT1 null genotype was observed by carrying out multiplex PCR.

RESULTS

There was no difference in the frequencies of the GSTM1 and GSTT1 null and the combined GSTM1 and GSTT1 null genotype between patients and control.

CONCLUSIONS

Our data suggest that GSTM1 and GSTT1 status may not influence the risk of developing gastric cancer.

Developmental kinetics and gene expression in male and female bovine embryos produced in vitro with sex-sorted spermatozoa

Using bovine embryos generated in vitro from IVF with X-sorted, Y-sorted and unsorted spermatozoa, we compared the kinetics of male and female embryo development and gene expression between male and female blastocysts. Bovine in vitro-matured oocytes (n = 8858) were fertilised with spermatozoa from each of three different bulls (X-sorted, Y-sorted or unsorted spermatozoa depending on the experiment). The cleavage rate was assessed 24, 27, 30, 33, 36, 40, 44 and 48 h post insemination (h.p.i.) and blastocyst development was recorded on Days 6-9. The relative mRNA abundance of nine genes (GSTM3, DNTM3A, PGRMC1, TP53, BAX, COX2, IGF2R, AKR1B1 and PLAC8) was analysed in male and female Day 7 blastocysts produced with sorted and unsorted spermatozoa from one bull. Cumulative cleavage rate and blastocyst yield were significantly higher in the unsorted group compared with the X- or Y-sorted group from the same bull (P < or = 0.05). Although differences existed between bulls in terms of cleavage rate, no differences were observed in cleavage rate between X- and Y-sorted spermatozoa within a bull. The blastocyst yield was significantly higher only for Bull 3 when the Y-sorted spermatozoa were used (27.1+2.8 v. 19.1+1.4 for Y- and X-sorted spermatozoa, respectively; P < 0.05). There were no differences in the mRNA abundance of the nine genes analysed between embryos of the same sex produced with sorted or unsorted spermatozoa. However, significant differences in polyA mRNA abundance were observed between male and female blastocysts for three genes (GSTM3, DNMT3A and PGRMC1; P < or = 0.05). In conclusion, the use of sorted rather than unsorted spermatozoa in IVF significantly delays the onset of first cleavage. Differences were noted between bulls, but not between X- and Y-sorted spermatozoa, and although no differences were found in terms of the mRNA abundance of the nine genes tested between sorted and unsorted spermatozoa, sex-related differences were found in the case of three genes.

Genetic variations associated with interindividual sensitivity in the response to arsenic exposure

People are exposed to arsenic compounds environmentally, occupationally or therapeutically. In some areas, where arsenic is present in high proportions in the drinking water, this exposure represents an important health concern. Chronic exposure to arsenic leads to hyperkeratosis and loss of skin pigmentation, as well as to significant increases of different types of cancer in skin, lung, bladder and liver; in addition, other pathologies, such as vascular diseases, hepatotoxicity and diabetes, have also been related to arsenic exposure. Since high interindividual variability is observed among people exposed to equivalent doses, genetic susceptibility factors have been postulated to be involved. When inorganic arsenic enters into the body it undergoes metabolic conversion, in a process where methylation plays a crucial role. Trivalent forms, both inorganic and organic, are the most toxic and genotoxic and, for this reason, metabolic variations owing to variant alleles in genes involved in such a process have been the aim of several studies. Genes involved in other mechanisms, such as antioxidant defense and DNA-repair lesions, among others, have also been the subject of association studies. A survey of those studies related to individual susceptibility is summarized here. Results with genes involved in folate one-carbon metabolism and in arsenic transport across the cell membrane provide promising data for future studies.

The gene expression profile of psoralen plus UVA-induced premature senescence in skin fibroblasts resembles a combined DNA-damage and stress-induced cellular senescence response phenotype

After a finite number of population doublings, normal human cells undergo replicative senescence accompanied by growth arrest. We previously described a model of stress-induced premature senescence by treatment of dermal fibroblasts with psoralen plus UVA, a common photodermatological therapy. Psoralen photoactivation has long been used as a therapy for hyperproliferative skin disorders. The repetitive therapeutical treatment is accompanied by premature aging of the skin. Treatment of fibroblasts in vitro with 8-methoxypsoralen (8-MOP) and subsequent ultraviolet A (UVA) irradiation results in growth arrest with morphological and functional changes reminiscent of replicative senescence. For gene expression profiling in two strains of human skin fibroblasts after PUVA treatment, we used a low-density DNA array representing 240 genes involved in senescence and stress response. Twenty-nine genes were differentially expressed after PUVA treatment in the two strains of human skin fibroblasts. These genes are involved in growth arrest, stress response, modification of the extracellular matrix and senescence. This study contributes further to the elucidation of the PUVA model and its validation as a useful stress-induced premature senescence model aiming to characterize the premature senescence of fibroblasts and to identify biomarkers that could be applied in vivo.

Increased frequencies of glutathione-S-transferase (GSTM1 and GSTT1) null genotypes in Indian patients with chronic myeloid leukemia

Inherited differences in the capacity of xenobiotic metabolizing enzymes might be an important factor in genetic susceptibility to cancer. Null genotypes of glutathione-S-transferases (GSTs) exhibit absence of enzymatic activity and are hypothesized to be at increased risk of developing cancers. The aim of the study was to examine whether null genotypes of GSTM1 and GSTT1 confer susceptibility to chronic myeloid leukemia (CML). We carried a case control study involving 80 consecutive North Indian CML patients (58 males, 22 females; age (mean+/-S.D.) 36.2+/-10.9 years) and 105 healthy individuals (59 males, 46 females; age (mean+/-S.D.) 36.8+/-11.3 years). Multiplex PCR was carried out to determine the frequency of GSTM1 and GSTT1 null genotypes. The relationship between GSTM1, GSTT1 genotypes and risk of CML was assessed by means of odds ratio (OR) with 95% confidence limits calculated by logistic regression. A test for trend (P(trend)) in increasing the risk of CML having more than one putative high-risk allele or genotype was evaluated by means of the chi-square test. There was no difference in the frequencies of the GSTM1 null genotype and the combined GSTM1 and GSTT1 null genotypes between patients and controls in the study. However, statistical significance was found with GSTT1 null genotype frequency in CML patients as compared to controls (16/80 (20%) versus 9/105 (8.5%); OR=2.67, 95% CI: 1.03-7.01). It projects a 2.67-fold increased risk for CML in individuals with GSTT1 null genotype as compared to those possessing both alleles of the gene. Our findings suggest that heritable GST status may influence the risk of developing CML.

Gender-specific protective effect of hemoglobin on arsenic-induced skin lesions

Chronic arsenic poisoning remains a public health crisis in Bangladesh. As arsenic has been shown to bind to human hemoglobin (Hb), hematologic mechanisms may play a role in the pathway through which arsenic exerts its toxicity. Two separate studies, a case-control and a cohort, were conducted to investigate the role of Hb in the development of arsenic-induced skin lesions. In the first, conditional logistic regression was used to investigate the effect of Hb on skin lesions among 900 case-control pairs from Pabna, Bangladesh, in which individuals were matched on gender, age, and location. In the second, mixed linear regression models were used to examine the association between toenail arsenic, urinary arsenic, and Hb within a cohort of 184 individuals from 50 families in the same region who did not have arsenic-induced skin lesions. Hb was significantly associated with skin lesions but this association was gender specific. In males, a 40% reduction in the odds of skin lesions occurred for every 1 g/dL increase in Hb (odds ratio, 0.60; 95% confidence interval, 0.49-0.73). No effect was observed for females (odds ratio, 1.16; 95% confidence interval, 0.92-1.46). In the cohort of 184 individuals, no associations between toenail arsenic or urinary arsenic species and Hb levels were observed. Low Hb levels may exacerbate the detrimental health effects of chronic arsenic poisoning. Whereas providing clean water remains the optimal solution to Bangladesh's problem of arsenic poisoning, improving nutrition and reducing iron-deficiency anemia may ameliorate negative health effects, such as skin lesions in individuals who have been exposed.

The molecular epidemiology of gliomas in adults

In this paper the authors highlight recent findings from molecular epidemiology studies of glioma origin and prognosis and suggest promising paths for future research. The reasons for variation in glioma incidence according to time period of diagnosis, sex, age, ancestry and ethnicity, and geography are poorly understood, as are factors that affect prognosis. High-dose therapeutic ionizing irradiation and rare mutations in highly penetrant genes associated with certain rare syndromes—the only two established causes of glioma—can be called upon to explain few cases. Both familial aggregation of gliomas and the inverse association of allergies and immune-related conditions with gliomas have been shown consistently, but the explanations for these associations are inadequately developed or unknown. Several bio-markers do predict prognosis, but only evaluation of loss of 1p and 19q in oligodendroglial tumors are incorporated in clinical practice. Ongoing research focuses on classifying homogeneous groups of tumors on the basis of molecular markers and identifying inherited polymorphisms that may influence survival or risk. Because most cases of glioma have yet to furnish either an environmental or a genetic explanation, the greatest potential for discovery may lie in genomic studies in conjunction with continued evaluation of environmental and developmental factors. Large sample sizes and multidisciplinary teams with expertise in neuropathology, genetics, epidemiology, functional genomics, bioinformatics, biostatistics, immunology, and neurooncology are required for these studies to permit exploration of potentially relevant pathways and modifying effects of other genes or exposures, and to avoid false-positive findings. Improving survival rates for patients harboring astrocytic tumors will probably require many randomized clinical trials of novel treatment strategies.

GSTT1 andGSTM1 gene polymorphisms and gastric cancer in a high-risk italian population

Glutathione S-Transferases (GSTs) are a family of phase II enzymes involved in the detoxification of potential carcinogens and provided of a strong antioxidant function by neutralizing electrophiles and free radicals. The GSTM1 and GSTT1 isoenzymes exhibit deletion polymorphisms, resulting in a lack of activity, and the null genotypes have been associated with increased cancer risk at several sites, including the stomach, although with contrasting results. We carried out a case-control study to evaluate whether these polymorphisms modulate the risk of developing gastric cancer (GC). Genotypes for GSTM1 and GSTT1 were obtained from a series of 175 histologically confirmed GC patients and a large series of 546 healthy controls randomly sampled from the general population of Tuscany, an area at high GC risk. No difference in the frequency of GSTM1 null genotype was observed between cases and controls, whereas the GSTT1 null genotype was more frequent among cases (p = 0.04). Multivariate single-gene analyses adjusted for possible confounders showed that the GSTT1 null genotype, but not the GSTM1 null genotype, was associated with an increased GC risk. Combined-genotype analyses showed a significantly increased GC risk only for the double null (GSTM1-GSTT1) genotype (OR = 2.27; 95% CI: 1.14-4.53). A statistically significant positive interaction between the 2 null genotypes was observed (p = 0.02). Our findings suggest that only subjects lacking both GSTM1 and GSTT1 activity are at increased GC risk. This study provides further support to the hypothesis that the risk of developing GC is influenced by inter-individual variation in both carcinogen detoxification and antioxidant capacity. (c) 2005 Wiley-Liss, Inc.

Polymorphisms of drug metabolizing enzymes and markers of genotoxicity to identify patients with Hodgkin's lymphoma at risk of treatment-related complications

Survivors of childhood Hodgkin's lymphoma (HL) have an increased risk of developing treatment-related complications, especially second malignant neoplasms, as a result of treatment regimens incorporating chemotherapy and radiation therapy. Second cancers include leukemias that generally occur in the first two decades after therapy, and adult-type solid tumors that generally exhibit continued increasing incidence throughout subsequent follow-up. Identified clinical risk factors for second cancers include age at the time of treatment and intensity and type of therapy, with particularly strong associations between the use of radiotherapy and subsequent breast cancer, and alkylator chemotherapy dose-intensity and risk of secondary leukemia. However, second cancers affect a minority of patients, and there is probably great variability in individual susceptibility for this complication. Common genetic polymorphisms in drug-metabolizing enzymes that result in impaired detoxification of chemotherapy or inefficient repair of drug- or radiation-induced genetic damage may lead to increased risk of a second cancer. Studies of the potential role of polymorphisms in the genes encoding the glutathione S-transferases, cytochrome P450 3A4, NAD(P)H:quinone oxidoreductase and myeloperoxidase in the etiology of treatment-related complications are reviewed. Biological markers of drug- and radiation-induced genetic damage may also identify patients at higher risk of immediate and delayed side effects of therapy. The Children's Oncology Group (COG) is examining the roles of polymorphisms in drug metabolizing enzymes and biological markers of genotoxicity in predicting the treatment-related outcomes of patients with HL. These investigations may ultimately allow the use of pharmacogenetically guided therapy to improve the outcome of HL therapy and reduce the risk of therapy-related complications, especially secondary malignancies.

Microsomal epoxide hydrolase and glutathione S-transferase polymorphisms in relation to laryngeal carcinoma risk

Two polymorphic sites of the microsomal epoxide hydrolase gene (EPHX1, 113Tyr-->113His, 139His-->139Arg) and four glutathione S-transferase genes (GSTM1, GSTM3, GSTP1, GSTT1) were genotyped in a group of patients with larynx cancer (N=204) and in a group of healthy controls (N=203), all Spanish caucasians. After adjusting for gender, age, and tobacco smoking, none of the polymorphisms alone were found to be associated with larynx cancer risk. The analysis of EPHX1/GST combinations, however, showed a significant over-representation of patients with a combination of 113Tyr/113Tyr EPHX1 and 105Ile/105Ile GSTP1 (adjusted odds ratio (OR): 1.95; 95% confidence interval (CI): 1.02-3.78). The calculation of the predicted epoxide hydrolase (EH) activity also showed an increased risk for the individuals with both predicted high activity EH and 105Ile/105Ile GSTP1 (OR: 2.90; 95% CI: 1.10-7.67). These results on larynx cancer tend to confirm a former study on lung cancer (Cancer Lett. 173 (2001) 155) suggesting the existence of an interaction between variants of EH and GSTpi, both enzymes being involved in the metabolism of aromatic hydrocarbons, that may increase susceptibility to tobacco-related cancers.

The GSTM1 null genotype confers an increased risk for solar keratosis development in an Australian Caucasian population

Solar keratoses affect approximately 50% of Australian Caucasians aged over 40 y. Solar keratoses can undergo malignant transformation into squamous cell carcinoma followed by possible metastasis and are risk factors for basal cell carcinoma, melanoma, and squamous cell carcinoma. The glutathione-S-transferase genes play a part in detoxification of carcinogens and mutagens, including some produced by ultraviolet radiation. This study examined the role of glutathione-S-transferase M1, T1, P1, and Z1 gene polymorphisms in susceptibility to solar keratoses development. Using DNA samples from volunteers involved in the Nambour Skin Cancer Prevention Trial, allele and genotype frequencies were determined using polymerase chain reaction and restriction enzyme digestion. No significant differences were detected in glutathione-S-transferase P1 and glutathione-S-transferase Z1 allele or genotype frequencies; however, a significant association between glutathione-S-transferase M1 genotypes and solar keratoses development was detected (p=0.003) with null individuals having an approximate 2-fold increase in risk for solar keratoses development (odds ratio: 2.1; confidence interval: 1.3-3.5) and a significantly higher increase in risk in conjunction with high outdoor exposure (odds ratio: 3.4; confidence interval: 1.9-6.3). Also, a difference in glutathione-S-transferase T1 genotype frequencies was detected (p=0.039), although considering that multiple testing was undertaken, this was found not to be significant. Fair skin and inability to tan were found to be highly significant risk factors for solar keratoses development with odds ratios of 18.5 (confidence interval: 5.7-59.9) and 7.4 (confidence interval: 2.6-21.0), respectively. Overall, glutathione-S-transferase M1 conferred a significant increase in risk of solar keratoses development, particularly in the presence of high outdoor exposure and synergistically with known phenotypic risk factors of fair skin and inability to tan.

Immunohistochemical markers for prognosis of cerebral glioblastomas

Glioblastoma is the commonest neuroectodermal tumor and the most malignant in the range of cerebral astrocytic gliomas. The prognostic utility of various biological markers for glioblastomas has been broadly tested but the results obtained are regarded as controversial. In the present study, 302 glioblastoma specimens were studied to evaluate a possible association between clinical outcome and expression of some immunohistochemical variables. Furthermore, tumors examined were subdivided on the three cytological subsets--small-cell (SGB), pleomorphic-cell (PGB) and gemistocytic (GGB). Immunohistochemical variables differed between various subsets: the number of p53-positive tumors was found to be prevailed among the PGB, whereas the number of tumors with EGFR and mdm2 positivity was significantly greater in SGB. GGB contained significantly lowest mean proliferating cell nuclear antigen (PCNA) labeling index (LI), greater number of p21ras positive cases, and higher mean apoptotic index (AI). Survival time in patients with SGB, EGFR and mdm2-positivity and PCNA LI >40% was found to be significantly shorter, whereas presence of p21ras and AI >0.5% were associated with prolonged survival. Multivariate analysis revealed that survival time is associated with SGB, EGFR-positivity, and AI (p = 0.0023, p = 0.0035 and p = 0.0029 respectively). We conclude that although some immunohistochemical variables were found to be significant for glioblastoma outcome, they appear to be closely related to biology of single cytological subsets. Furthermore, these variables exhibited no prognostic value when they were analyzed within each cytological subset separately. Therefore, the glioblastoma subdivision on three cytological subsets proposed by us is carrying some element of rationality but, undoubtedly, requires further prospective studies.

Effects of solar radiation on cutaneous detoxification pathways

Because of its accessibility the human skin is constantly exposed to solar ultraviolet (UV) radiation. It is increasingly appreciated that exposure of the mammalian skin to UV plays a causal and decisive role in acute and chronic skin damage including the development of skin cancer. UV exposure causes sunburn, pigmentation, hyperplasia, immunosuppression, DNA damage, photoaging and photocarcinogenesis. To cope with constant environmental damage the skin possesses elaborate enzymatic detoxification systems. This paper briefly focuses on the effect of solar radiation, particularly UV spectrum, on detoxification pathways in the skin. Specifically the effect of solar radiation on cytochrome P450, glutathione, superoxide dismutase, glutathione peroxidase, catalase, glutathione-S-transferase and ceruloplasmin has been discussed.

Glutathione S-transferase polymorphisms and skin cancer after renal transplantation

BACKGROUND

Susceptibility to skin cancer after transplantation is multifactorial, and risk factors include skin type, sun exposure, and level of immunosuppression. A major mechanism of carcinogenesis is ultraviolet radiation-induced free radical damage, and genetically determined ability to metabolize free radicals may also predispose to skin cancer. The glutathione S-transferase enzymes play a major role in limiting the toxic effects of reactive oxygen species, and this study was designed to determine whether polymorphisms in these enzymes are associated with skin cancers in renal transplant recipients.

METHODS

Two hundred twenty-two long-term survivors of renal transplantation were examined for polymorphisms in the GSTM1, GSTT1, and GSTP1 genes, using a unified polymerase chain reaction with sequence specific primers (PCR-SSP) genotyping method.

RESULTS

The GSTP1*C allele was associated with the development of squamous cell carcinomas (SCCs; P = 0.01). No associations of the GSTM1 null genotype or the GSTT1 null genotype were identified, and the development of basal cell carcinomas was not associated with any GST polymorphism studied.

CONCLUSIONS

These results indicate that genetic variation in enzymes involved in free radical metabolism in the skin are associated with the development of skin cancer. While all renal transplant recipients should be advised to protect themselves from the sun, the identification of transplant patients with a genetic predisposition to skin tumors may permit the targeting of preventative and early intervention strategies to high-risk individuals.

A multiplex-PCR/RFLP procedure for simultaneous CYP2E1, mEH and GSTM1 genotyping

Inter-individual variation in metabolism of environmental toxicants, which is attributed to genetic polymorphism, may be a major risk factor in determining who will develop adverse health effects. This priority research area is the focus of many laboratories, and new techniques need to be developed to enhance the efficiency in generating data. We have developed and validated a new multiplex-polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) procedure for simultaneous genotyping of cytochrome P450 II E1 (CYP2E1), microsomal epoxide hydrolase (mEH), and glutathione S-transferase mu (GSTM1). Enzymes from these three polymorphic genes are involved with the phase I and II metabolism of a variety of environmental toxicants. Therefore, simultaneous characterization of these genes will not only reduce costs but will increase the efficiency of data collection, thereby contributing to health risk assessment efforts.

The chromosome-based challenge assay using fluorescence in situ hybridization: a possible test for increased cancer susceptibility

The challenge assay is a cytogenetic approach to measure the repair competence of cells. For in vitro studies, human lymphocytes are exposed to different substances and are irradiated simultaneously. To investigate subjects exposed occupationally or environmentally, untreated blood samples are directly irradiated without any further treatment. Certain substances like heavy metals reveal carcinogenic potential without well defined mechanism of action. While they are not mutagenic they may have an effect on DNA repair capacity. The challenge assay was successfully applied in vitro experiments with cadmium to detect an interaction of this heavy metal with the repair of X-ray-induced chromosome breaks. CdCl(2) alone had no effect on the formation of chromosome aberrations (CA), not even in the cytotoxic concentration (50 microM). However, cadmium showed an effect on the number of chromosomal rearrangements (CR) after X-ray challenge. For 0.5 microM CdCl(2), CA frequencies were significantly elevated compared to the rates for X-rays alone. For the two higher concentrations the rates showed a slight additional increase. Hence, the challenge assay appears suitable to test for chromosomal sensitivity induced by toxicants. Subsequently, a study of styrene exposed workers was initiated to address the question whether styrene exposure has an influence on the DNA repair. In addition, we investigated whether a polymorphism of genes coding for phase II detoxifying enzymes glutathione-S-transferases GSTM1 and GSTT1 had an influence on chromosomal sensitivity. First and preliminary data are presented. While there is a correlation of the rate of CR with cumulative lifetime exposure of styrene, the most recent styrene exposure had no effect. 'At risk' genotypes with higher incidence of CA could not be identified at this stage of the ongoing study.

CONCLUSION

the challenge assay is able to detect enhanced susceptibility for CR caused by genetic predisposition for DNA repair deficiency. Our data indicate that environmental or occupational exposure to certain substances can interfere with DNA repair processes. As the process of induction of CR is associated with carcinogenesis, the challenge assay may provide a valuable biomarker for cancer epidemiology studies.