Phenotype of glutathione S-transferase Mu (GSTM1) and susceptibility to malignant melanoma. MMM group. Multidisciplinary Malignant Melanoma Group

Genotype and Phenotype of Glutathione-S-Transferase in Patients with Head and Neck Carcinoma

OBJECTIVE: Association of glutathione-S-transferase M1 (GSTM1) polymorphisms and cancer has been demonstrated. Possible underlying mechanisms and genotype-phenotype correlations are not adequately investigated. The aim of this study was to investigate the influence of the GSTM1-null-genotype on the level of GSTM enzyme concentration and on the enzyme activity of GST in patients with head and neck cancer (HNC).

METHODS: We investigated in 83 patients and 91 healthy controls the GSTM1 polymorphisms, GSTM1 protein concentration, GSTM1 protein in tumor tissues, and total GST enzyme activity.

RESULTS: Total GST enzyme activity was significantly lower in patients with HNC (208 ± 9 μmol/min1) than in controls (264 ± 11 μmol/min1, P < 0.0001) but did not depend on GSTM1-genotype ( P = 0.1). GSTM protein concentration in null-genotype patients (3.6 ± 2.5 μg/mL, mean ± SE) was significantly lower than in GSTM1 allele carriers (26.7 ± 9.6 μg/ml, P < 0.0001); GSTM protein expression did not depend on GSTM1-genotype ( P > 0.5).

CONCLUSION: GST enzyme activity in patients with HNC is suppressed, indicating impaired detoxification capacity of tobacco-smoke-related carcinogens. This suppression is not correlated with the GSTM1-genotype. (Otolaryngol Head Neck Surg 2004;130:718-25.)

Contribution of glutathione S-transferase gene polymorphisms to development of skin cancer

BACKGROUND

Glutathione S-transferase (GST) family genes are of vital importance in maintaining cellular defence systems, protecting cells against the toxic effects of reactive oxygen produced during the synthesis of melanin, and detoxifying environmental mutagens and chemical or synthetic drugs. As no previous meta-analyses have examined the association of polymorphisms at GSTT1, GSTP1 Ile105Val with skin cancer risk and independently published studies have produced inconsistent conclusions, we were promoted to estimate the associations in the largest study to date.

METHODS

Computer-assisted searches were carried out to systematically identify the studies of GST polymorphisms and skin cancer. The eligibility of studies was evaluated following the requirements of inclusion criteria. Risk of skin cancers (OR and 95% CI) was assessed with the fixed or random effects meta-analysis.

MAJOR FINDINGS

The fixed effects meta-analysis of 15 studies suggested no overall association between GSTT1 null and skin cancer. Nor was there a significant association in any subgroup. However, in the stratified analysis by histologic type for GSTP1 Ile105Val, we found 1.56 times higher risk of malignant melanoma (MM) among people with the 105-Val/Val genotype (Val/Val vs. Ile/Ile: OR = 1.56, 95% CI = 1.05-2.32, pheterogeneity = 0.584).

CONCLUSIONS

These statistical data demonstrate that Ile105Val polymorphism of the GSTP1 gene may have genetic contribution to the development of skin cancer, MM in particular.

High- and low-penetrance cutaneous melanoma susceptibility genes

The aim of this review is to report the current understanding of the molecular genetics of melanoma predisposition. To date, two high-penetrance melanoma susceptibility genes, cyclin-dependent kinas inhibitor (CDKN)2A on chromosome 9p21 and cyclin-dependent kinase (CDK4) on 12q13, have been identified. Germline inactivating mutations of the CDKN2A gene are the most common cause of inherited susceptibility to melanoma. Worldwide, a few families have been found to harbor CDK4 mutations. However, predisposing alterations to familial melanoma are still unknown in a large proportion of kindreds. Other melanoma susceptibility loci have been mapped through genome-wide linkage analysis, although the putative causal genes at these loci have yet to be identified. Much ongoing research is being focused on the identification of low-penetrance melanoma susceptibility genes that confer a lower melanoma risk with more frequent variations. Specific variants of the MC1R gene have been demonstrated to confer an increase in melanoma risk. In addition, conflicting data are available on other potential low-penetrance genes encoding proteins involved in pigmentation, cell growth and differentiation, DNA repair or detoxifying of metabolites.

NBN Gene Polymorphisms and Cancer Susceptibility: A Systemic Review

The relationship between DNA repair failure and cancer is well established as in the case of rare, high penetrant genes in high cancer risk families. Beside this, in the last two decades, several studies have investigated a possible association between low penetrant polymorphic variants in genes devoted to DNA repair pathways and risk for developing cancer. This relationship would be also supported by the observation that DNA repair processes may be modulated by sequence variants in DNA repair genes, leading to susceptibility to environmental carcinogens. In this framework, the aim of this review is to provide the reader with the state of the art on the association between common genetic variants and cancer risk, limiting the attention to single nucleotide polymorphisms (SNPs) of the NBN gene and providing the various odd ratios (ORs). In this respect, the NBN protein, together with MRE11 and RAD50, is part of the MRN complex which is a central player in the very early steps of sensing and processing of DNA double-strand breaks (DSBs), in telomere maintenance, in cell cycle control, and in genomic integrity in general. So far, many papers were devoted to ascertain possible association between common synonymous and non-synonymous NBN gene polymorphisms and increased cancer risk. However, the results still remain inconsistent and inconclusive also in meta-analysis studies for the most investigated E185Q NBN miscoding variant.

Effect of GSTM1 polymorphism on risks of basal cell carcinoma and squamous cell carcinoma: a meta-analysis

Glutathione S-transferases are important enzymes in the detoxification of a wide range of reactive oxygen species produced during melanin synthesis and oxidative stress processes. Glutathione S-transferase M1 (GSTM1) null genotype may be a candidate genetic polymorphism with a role in susceptibility to skin cancer such as basal and squamous cell carcinomas. We conducted a systematic review and meta-analysis to define the effect of GSTM1 null polymorphism on skin cancer risk. We searched the PubMed, Embase, and Web of Science databases to identify published case-control studies investigating the association between GSTM1 null genotype and skin cancer risk. Between-study heterogeneity was assessed using the I (2) statistic. Odds ratios (OR) with corresponding 95 % confidence intervals (95 % CI) from individual studies were pooled using fixed and random effects models. Nineteen case-control studies (4,275 cases and 4,255 controls) were considered eligible and included in the meta-analysis, and 11 of which were on basal cell carcinoma; ten, on melanoma, and seven, on squamous cell carcinoma. Overall, the GSTT1 null genotype was not associated with the risk of skin cancer (OR, 1.01; 95 % CI 0.93-1.11; P = 0.76). Subgroup analysis by histological types showed that GSTT1 null genotype was not associated with risks of basal cell carcinoma (OR, 1.06; 95 % CI 0.92-1.21; P = 0.42), squamous cell carcinoma (OR, 0.97; 95 % CI 0.76-1.24; P = 0.80), and cutaneous malignant melanoma (OR, 1.00; 95 % CI 0.88-1.14; P = 0.60). Therefore, this meta-analysis suggests that GSTM1 null polymorphism is not associated with risks of basal and squamous cell carcinomas.

Expression patterns of carcinogen detoxifying genes (CYP1A1, GSTP1 & GSTT1) in HNC patients

Carcinogen detoxifying genes may be involved in pathogenesis of head and neck cancer (HNC). CYP1A1 is phase I enzyme that converts carcinogens into water soluble compounds which are easily excreted from body. GSTs constitute phase II detoxification enzymes that recognize these highly electrophilic compounds and detoxify them. Abnormal expression of these genes can potentially lead to cancer initiation. In present study, we analyzed protein expression of these genes in a total of 192 HNC patients and noncancerous healthy control serum samples screened for GSTs specific activity by ELISA. Furthermore, expression of these molecules was also determined in 49 HNC tissues/ adjacent control tissue by immunohistochemistry with specific antibodies. Mean serum GSTs specific activity was found to be 7.7 (+11.5)U/L in HNC patients and 11.4 (+7.5)U/L in controls. Significant decrease (P < 0.05) in GSTs specific activity was observed in HNC patients compared with controls (P < 0.001). Data for immunohistochemistry showed that CYP1A1 and GSTT1 was down expressed whereas GSTP1 was over expressed in HNC tissues compared with adjacent normal control tissues. Results of immunohistochemistry revealed 63 % HNC tissues had weak, 27 % moderate and 10 % strong staining for CYP1A1. For GSTT1, 27 % HNC tissues had no staining, 49 % weak staining, 16 % moderate and 8 % strong staining. Similarly for GSTP1, percentages for weak, moderate and strong staining were 6 %, 12 % and 82 % respectively. These reduced proteins observed in cancer patients highlight a potential breach on DNA repair mechanism when compared with control. Thus altered expression of these detoxifying molecules may collectively contribute to HNC development in Pakistani population.

Role of glutathione S-transferases in melanoma susceptibility: association with GSTP1 rs1695 polymorphism

BACKGROUND

Glutathione S-transferases (GSTs) GSTM1, GSTT1 and GSTP1 are multifunctional enzymes involved in the detoxification of a wide range of reactive oxygen species produced during melanin synthesis and oxidative stress processes.

OBJECTIVES

Single nucleotide polymorphisms (SNPs) in GSTP1 and copy number variants in GSTM1 and GSTT1 may be candidate low-penetrance variants with a role in susceptibility to malignant melanoma (MM).

METHODS

In this case-control study, 562 Spanish patients with sporadic MM and 338 cancer-free control subjects were included, and the role of polymorphisms in these GST genes was investigated. Genotypes were established by quantitative real-time polymerase chain reaction for GSTM1 and GSTT1 while TaqMan probes were used to genotype GSTP1 SNPs.

RESULTS

The GSTP1 polymorphism rs1695, which encodes the amino acid change p.Ile105Val, was individually associated with MM [odds ratio (OR): 1·32, 95% confidence interval (CI): 1·06-1·63]. Furthermore, individuals carrying one or two MC1R nonsynonymous changes and GSTP1 rs1695 rare allele had an increased risk of developing MM (OR: 3·34, 95% CI: 1·42-8·09 and OR: 20·42, 95% CI: 2·80-417·42, respectively).

CONCLUSIONS

This is the first time that the GSTP1 rs1695 polymorphism is reported to be associated with MM. In addition, this study is one of the largest GST polymorphism studies undertaken in the Spanish population and the first time that copy number variants have been scrutinized in relation to MM.

Cellular and sub-cellular responses to UVA in relation to carcinogenesis

PURPOSE

UVA radiation (315-400 nm) contributes to skin aging and carcinogenesis. The aim of this review is to consider the mechanisms that underlie UVA-induced cellular damage, how this damage may be prevented or repaired and the signal transduction processes that are elicited in response to it.

RESULTS

Exposure to ultraviolet (UV) light is well-established as the causative factor in skin cancer. Until recently, most work on the mechanisms that underlie skin carcinogenesis focused on shorter wavelength UVB radiation (280-315 nm), however in recent years there has been increased interest in the contribution made by UVA. UVA is able to cause a range of damage to cellular biomolecules including lipid peroxidation, oxidized protein and DNA damage, such as 8-oxoguanine and cyclobutane pyrimidine dimers. Such damage is strongly implicated in both cell death and malignant transformation and cells have a number of mechanisms in place to mitigate the effects of UVA exposure, including antioxidants, DNA repair, and stress signalling pathways.

CONCLUSIONS

The past decade has seen a surge of interest in the biological effects of UVA exposure as its significance to the process of photo-carcinogenesis has become increasingly evident. However, unpicking the unique complexity of the cellular response to UVA, which is only now becoming apparent, will be a major challenge for the field of photobiology in the 21st century.

Molecular genetic analysis of NBS1 in German melanoma patients

The aim of this study was to investigate the role of NBS1 in the pathogenesis of malignant melanoma of the skin. To exclude the common 657del5 founder mutation, a total of 376 melanoma patients from Southern Germany were analyzed for sequence alterations in exon 6 of NBS1 by direct sequencing. Analyses revealed one 657del5 mutation and three nonsynonymous sequence variations in exon 6 of NBS1 (V210F, R215W, and F222L). Analysis of an additional sample of 629 melanoma patients and 604 controls revealed no F222L mutation, indicating that this newly identified sequence alteration is not a common polymorphism. In a case-control association study including 632 melanoma patients and 615 cancer-free control participants from Southern Germany, three publicly known single nucleotide polymorphisms located in the NBS1 gene region were analyzed. No significant associations between single nucleotide polymorphisms (rs9995, rs867185 and rs1063045) or referring calculated haplotypes and melanoma risk were identified. These results suggest that NBS1 does not play a major role in predisposition to melanoma in the Southern German population but that alterations of this gene might contribute to the risk of this cancer.

ICAM-1 polymorphisms and development of cutaneous malignant melanoma

Tumour growth in cutaneous malignant melanoma (CMM) is mediated by cell adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1). ICAM-1 expression is associated with increasing Breslow thickness of vertical growth-phase tumours and, in patients with stage 1 disease, may be associated with disease free and patient survival. In this study we have investigated whether two single nucleotide polymorphisms (SNPs) in the ICAM-1 gene encoding amino acid substitutions in codons 241 and 469 of the expressed ICAM-1 molecule are associated with susceptibility to and markers of prognosis (including tumour Breslow thickness) in CMM. A total of 164 CMM patients and 264 cancer-free controls were genotyped for these SNPs by the 5' nuclease assay for allelic discrimination (TaqMan). No genotypes showed any significant associations with CMM susceptibility, although there was a non-significant increase in frequency of the ICAM-1 469 AA genotype among CMM patients vs. controls (38.4% vs. 29.9%; P = 0.11). However, the ICAM-1 241 GG genotype was significantly decreased in frequency among patients with primary invasive tumours of greater Breslow thickness (72.5% vs. 91.2%; P = 0.013; OR = 0.25 (0.072-0.85)). These results provide no evidence for a role for the ICAM-1 codon 241 and 469 SNPs in determining susceptibility to CMM, but provide preliminary evidence that the role of ICAM-1 polymorphism in modulating tumour growth in CMM requires further investigation in a larger study group.

No Evidence for BRAF as a Melanoma/Nevus Susceptibility Gene

Somatic mutations of BRAF have been identified in both melanoma tumors and benign nevi. Germ line mutations in BRAF have not been identified as causal in families predisposed to melanoma. However, a recent study suggested that a BRAF haplotype was associated with risk of sporadic melanoma in men. Polymorphisms or other variants in the BRAF gene may therefore act as candidate low-penetrance genes for nevus/melanoma susceptibility. We hypothesized that promoter variants would be the most likely candidates for determinants of risk. Using denaturing high-pressure liquid chromatography and sequencing, we screened peripheral blood DNA from 184 familial melanoma cases for BRAF promoter variants. We identified a promoter insertion/deletion in linkage disequilibrium with the previously described BRAF polymorphism in intron 11 (rs1639679) reported to be associated with melanoma susceptibility in males. We therefore investigated the contribution of this BRAF polymorphism to melanoma susceptibility in 581 consecutively recruited incident cases, 258 incident cases in a study of late relapse, 673 female general practitioner controls, and the 184 familial cases. We found no statistically significant difference in either genotype or allele frequencies between cases and controls overall or between male and female cases for the BRAF polymorphism in the two incident case series. Our results therefore suggest that the BRAF polymorphism is not significantly associated with melanoma and the promoter insertion/deletion linked with the polymorphism is not a causal variant. In addition, we found that there was no association between the BRAF genotype and mean total number of banal or atypical nevi in either the cases or controls.

The Relationship Between the Epidermal Growth Factor (EGF) 5′UTR Variant A61G and Melanoma/Nevus Susceptibility

The inheritance of a G allele in position 61 in the 5'UTR of the epidermal growth factor (EGF) gene has been reported to increase melanoma susceptibility, a finding we have investigated in this study. The most potent phenotypic risk factor for melanoma is the atypical mole syndrome (AMS) phenotype. Our hypothesis is that the AMS is genetically determined and that nevus genes are also low penetrance melanoma susceptibility genes. We report that the G allele frequencies were the same in 697 healthy women and 380 melanoma cases (OR 0.97, 95% CI 0.8-1.2 p=0.76). We therefore found no evidence that this polymorphism is a melanoma susceptibility gene. Furthermore, we found no evidence that the polymorphism controls the nevus phenotype (nevus number, number atypical nevi or AMS phenotype). We did find some evidence that the G allele may be associated with decreased tumor Breslow thickness (OR 0.5, 95% CI 0.3-0.9) for the A/A genotype versus A/G and G/G combined in tumors of thickness >3.5 vs < or =3.5 mm and may therefore act as a predictor of survival, although this finding is not in accord with the original report. This is the second study to find no association between EGF +61 and melanoma susceptibility.

Polymorphisms of the BRAF gene predispose males to malignant melanoma

The incidence of malignant melanoma has rapidly increased in recent years. Evidence points to the role of inheritance in melanoma development, but specific genetic risk factors are not well understood. Recent reports indicate a high prevalence of somatic mutations of the BRAF gene in melanomas and melanocytic nevi. Here we report that germ-line single nucleotide polymorphisms (SNPs) in BRAF are significantly associated with melanoma in German males, but not females. At-risk haplotypes of BRAF are shown. Based upon their frequencies, we estimate that BRAF could account for a proportion attributable risk of developing melanoma of 4% in the German population. The causal variant has yet to be determined. The burden of disease associated with this variant is greater than that associated with the major melanoma susceptibility locus CDKN2A, which has an estimated attributable risk of less than 1%.

EGF +61 gene polymorphism and susceptibility to and prognostic markers in cutaneous malignant melanoma

CMM is the most serious cutaneous malignancy and is increasing in frequency among most Caucasian populations, where the most important risk factor is exposure to UV light. Relatively little is known of the genetic factors that mediate susceptibility to and prognosis in sporadic CMM, although a number of genes have been implicated. A striking association between EGF polymorphism and Breslow thickness of invasive CMM has been reported. We have sought confirmation of this finding in an independent study of 159 patients and 310 controls using TaqMan fluorescence-based genotyping for EGF +61. In our study group, there were no significant differences in EGF genotype frequencies between patients and controls nor was EGF genotype associated with tumour growth phase, stage or mitotic count. However, correlation between EGF genotype and Breslow thickness showed a modestly significant increase in frequency of the EGF (G/G) genotype among tumours >3.5 mm thick (30.0% vs. 9.8%, p = 0.03). In summary, in our group, the EGF +61 polymorphism was not a risk factor for CMM susceptibility, but this polymorphism may play a role in disease progression.

Genetics of melanoma predisposition

Predisposition to melanoma is genetically heterogeneous. Two high penetrance susceptibility genes, CDKN2A and CDK4, have so far been identified and mapping is ongoing to localize and identify others. With the advent of a catalogue of millions of potential DNA polymorphisms, attention is now also being focused on identification of genes that confer a more modest contribution to melanoma risk, such as those encoding proteins involved in pigmentation, DNA repair, cell growth and differentiation or detoxification of metabolites. One such pigmentation gene, MC1R, has not only been found to be a low penetrance melanoma gene but has also been shown to act as a genetic modifier of melanoma risk in individuals carrying CDKN2A mutations. Most recently, an environmental agent, ultraviolet radiation, has also been established as a modifier of melanoma risk in CDKN2A mutation carriers. Hence, melanoma is turning out to be an excellent paradigm for studying gene-gene and gene-environment interactions.

GSTM1 enzyme concentration and enzyme activity in correlation to the genotype of detoxification enzymes in squamous cell carcinoma of the oral cavity

BACKGROUND

Differences in genotype and phenotype of detoxification genes could be one reason for conflicting results in studies dealing with gene polymorphisms as susceptibility factors for tobacco associated cancer.

OBJECTIVES

The objective of this study was to investigate gene polymorphisms of detoxification enzymes and to determine whether the enzyme concentration and activity of glutathione S transferase microliter 1 correlates with the genotype in patients with cancer of the oral cavity.

MATERIAL AND METHODS

In 73 cancer patients and 136 matched healthy controls, the polymorphisms of glutathione S-transferase mu1 and theta (GSTM/GSTT), cytochrome p450 1A1 and CYP2D6 were detected. Simultaneously, GSTM1 protein concentration and total GSTM1-activity were determined.

RESULTS

Only the coincidence of GSTM1 and GSTT null genotype was associated with oral cavity cancer. GSTM1 protein concentration and enzyme activity in null-genotype patients was significantly lower than in GSTM1-allele-carrier. But the enzyme concentration did not correlate with the activity.

CONCLUSION

We assume that detoxification enzymes are functionally redundant and that only the simultaneous deficiency of several detoxification enzymes increases the risk for oral cancer.

Influence of GSTT1 and GSTM1 genotypes on sunburn sensitivity

BACKGROUND

Exposure to sunlight may cause sunburn, skin cancer or phototoxic reactions to certain drugs such as Hypericum extract. All these are ultraviolet B (UVB)-mediated reactions which may be modulated by individual genetic susceptibility. UVB exposure results in oxidative stress. Many products of oxidative stress are detoxified by glutathione-S-transferases mu 1 (GSTM1) and theta 1 (GSTT1). Deletion polymorphisms (genotype *0/*0) of GSTM1 and GSTT1 occur in 50% and 20% of Caucasians, respectively. By affecting the individual ability to detoxify oxidative stress-related products, they may influence the severity of the cutaneous photoreaction.

METHODS

Minimal erythema doses (MED) of UVB irradiation on the skin were determined in 110 subjects who were selected according to their GSTT1 genotype (28 GSTT1*0/*0, 54 GSTT1*A/*0, and 28 GSTT1*A/*A). Genotypes were detected with novel polymerase chain reaction (PCR) assays that allow the differentiation between homozygous and heterozygous GSTT1 and GSTM1 deletions.

RESULTS

In the absence of GSTT1 enzyme, the susceptibility of individuals to UVB-induced inflammatory skin reactions increased significantly (p = 0.02, ANCOVA). 'Gene-equivalents' were calculated from the number of functional GSTM1 and GSTT1 alleles as a measure of the gene-dose. UVB sensitivity correlated with gene dose up to a threshold above which additional GSTT1 or GSTM1 alleles did not provide additional protection. Volunteers who were homozygously deficient in GSTT1 and GSTM1 were most sensitive to UVB. Interestingly, individuals with high GSTM1 gene-doses showed increased photosensitization after administration of Hypericum extract (St. John's wort).

CONCLUSION

Individuals harboring the *0/*0 genotype of GSTT1 and/or GSTM1 showed enhanced UVB-induced cutaneous damage. Moreover, GST genotypes modulated Hypericum-induced photosensitization.

Endometriosis: novel etiopathogenetic concepts and clinical perspectives

OBJECTIVE

To discuss current ideas about therapy for endometriosis derived from new observations generated by using molecular biology techniques and in vivo animal models of disease.

METHOD(S)

The MEDLINE database was reviewed for English-language articles on new drugs that affect the endocrine or immunologic system, the possibility that endometriosis has multiple forms, and the association of endometriosis with cancer. Specific attention was given to in vivo studies in animals or humans.

CONCLUSION(S)

Among the novel potential candidate drugs, aromatase inhibitors and raloxifene should be considered for treatment of postmenopausal women with endometriosis. Notable observations have emerged from studies of immunomodulators and antiinflammatory agents in animal models of disease. These findings must be confirmed in women. The histogenesis of ovarian endometriomas is still unclear, thus limiting new experimental approaches to this form of disease. Given the low but established risk for malignant transformation of endometriosis, efforts should be directed toward identification of susceptibility loci for the disease and its potential transformation into cancer.

Association between functional polymorphism in EGF gene and malignant melanoma

BACKGROUND

Malignant melanoma, the most serious cutaneous malignancy, has attracted substantial attention because of its rapidly increasing incidence and the poor prognosis of some tumours. Little is known of the genetic factors that mediate susceptibility to, and outcome of, sporadic malignant melanoma. Because of its role in mitogenesis, which is especially relevant to wound healing, tumorigenesis, and proliferation of epidermal tissues, epidermal growth factor (EGF) is an attractive candidate in which to look for genetic polymorphisms.

METHODS

We enrolled 135 white European patients with malignant melanoma and 99 healthy white European controls, and screened a selection of DNA samples for polymorphisms in the promoter and 5' untranslated region of the EGF gene by analysis. We then screened DNA samples from all participants for the identified polymorphism by restriction-fragment-length polymorphism (RFLP) analysis. In-vitro EGF production was measured in peripheral-blood mononuclear cells from 34 controls, and the results were compared with the individuals' EGF genotypes.

FINDINGS

We identified a single nucleotide substitution (G to A) at position 61 of the EGF gene. Allele frequencies in the controls were 56% EGF 61*A and 44% EGF 61*G. Cells from individuals homozygous for the 61*A allele produced significantly less EGF than cells from 61*G homozygotes (p=0.0004) or heterozygous A/G individuals (p=0.001). Compared with the A/A genotype, G/G was significantly associated with Breslow thickness (p=0.045) and with risk of malignant melanoma (odds ratio 4.9 [95% CI 2.3-10.2], p<0.0001).

INTERPRETATION

This study suggests that high EGF production might be important in the development of malignant melanoma.

Glutathione S-transferase T1 and M1 gene defects in ovarian carcinoma

Glutathione S-transferases (GSTs) M1 and T1 are known to be polymorphic in humans. Both polymorphisms are due to gene deletions, which are responsible for the existence of null genotypes. The gene defect of GSTT1 has been reported to be associated with an increased risk of myelodysplastic syndromes, astrocytoma and meningioma. A lack of GSTM1 was associated with tobacco smoke-induced lung and bladder cancer. In this study we examined whether the GSTT1 and/or GSTM1 homozygous null genotypes were associated with an increased risk of ovarian cancer using a multiplex polymerase chain reaction protocol. The GSTT1 null genotype was observed in 14% of the control subjects that had never suffered from neoplastic disease (n = 115) and in 16% of the patients affected with ovarian cancer (n = 103, OR 0.87, 95% CI 0.39-1.92, P = 0.73). A lack of GSTM1 was observed in 38% of the control subjects and in 46% of the patients (OR 0.77, 95% CI 0.44-1.32). This difference was not significant (P = 0.34). Similarly, no significant differences were obtained if GSTT1 and/or GSTM1 null genotypes were analyzed in subgroups of control subjects and ovarian cancer patients between the ages of 20-40, 41-70 and 71-90 years and in individuals with a positive family history of neoplastic disease. GSTT1 and/or GSTM1 null genotypes were not significantly associated with the histologic type and grade or FIGO (International Federation of Gynecology and Obstetrics) stages of the ovarian carcinomas. In conclusion, GSTT1 and/or GSTM1 null genotypes are not markers for an increased risk of ovarian cancer.

Glutathione S-transferases--biomarkers of cancer risk and chemopreventive response

The critical role of the glutathione S-transferase (GST) multigene family in cellular protection in combination with the large interindividual variability in the expression of these enzymes has prompted an investigation of their importance in cancer prevention and susceptibility. Previous preclinical and clinical studies from this laboratory have established an association between decreased GST activity and increased risk for colorectal cancer. Based upon the increased incidence of colon malignancies among patients with ulcerative colitis, GST activity has been examined in a mouse model of induced colitis. Significant decreases (50% of controls) in the GST activity of colon tissue were observed during the establishment and progression of colitis. These data suggested that depletion of cellular protection may be an important event in the carcinogenic progression of ulcerative colitis. The ability of the dithiolthione oltipraz to induce GST expression within the murine colon has been demonstrated. Use of chemopreventive regimens to induce phase 2 detoxication enzyme expression represents a promising strategy for the prevention of cancer. Clinical studies revealed that the GST activity of blood lymphocytes from individuals with either a personal or family history of colorectal cancer or a personal history of colon polyps was decreased significantly when compared to that of healthy controls. Phase 1 clinical evaluation of oltipraz has demonstrated its ability to induce GST activity as well as the level of transcripts encoding gamma-glutamylcysteine synthetase (gamma-GCS) and DT-diaphorase in the colon mucosa of individuals at increased risk for colorectal cancer. The observed correlation between the posttreatment response in blood lymphocytes and colon mucosa suggested that blood lymphocytes may be used in future trials as a surrogate biomarker of the responsiveness of colon tissue to chemopreventive regimens.

Characterization of the human class Mu glutathione S-transferase gene cluster and the GSTM1 deletion

A partial physical map has been constructed of the human class Mu glutathione S-transferase genes on chromosome 1p13.3. The glutathione S-transferase genes in this cluster are spaced about 20 kilobase pairs (kb) apart, and arranged as 5'-GSTM4-GSTM2-GSTM1-GSTM5-3'. This map has been used to localize the end points of the polymorphic GSTM1 deletion. The left repeated region is 5 kb downstream from the 3'-end of the GSTM2 gene and 5 kb upstream from the beginning of the GSTM1 gene; the right repeated region is 5 kb downstream from the 3'-end of the GSTM1 and 10 kb upstream from the 5'-end of the GSTM5 gene. The GSTM1-0 deletion produces a novel 7.4-kb HindIII fragment with the loss of 10.3- and 11.4-kb HindIII fragments. The same novel fragment was seen in 13 unrelated individuals (20 null alleles), suggesting that most GSTM1-0 deletions involve recombinations between the same two regions. We have cloned and sequenced the deletion junction that is produced at the GSTM1-null locus; the 5'- and 3'-flanking regions are more than 99% identical to each other and to the deletion junction sequence over 2.3 kb. Because of the high sequence identity between the left repeat, right repeat, and deletion junction regions, the crossing over cannot be localized within the 2.3-kb region. The 2.3-kb repeated region contains a reverse class IV Alu repetitive element near one end of the repeat.

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.

Deficiency of glutathione S-transferases T1 and M1 as heritable factors of increased cutaneous UV sensitivity

Glutathione S-transferases (GSTs) play a primary role in cellular defense against electrophilic chemical species and radical oxygen species. Because free radical attack is one mechanism of UV irradiation-caused skin damage, we investigated whether genetic variation at the GST loci GST T1 and GST M1 influences individual UVB sensitivity. In a double-blind clinical trial, 50 healthy volunteers were evaluated for minimal erythema dose of UVB irradiation, MED (J/cm2), skin types were assigned, and internal standard-controlled polymerase chain reaction (PCR) was used to identify their GST T1 and GST M1 genotypes. The five homozygous carriers of the GST T1 deletion (GST T1*0/0) presented with the most intensive inflammatory reactions after irradiation; they were significantly overrepresented among the highly UVB-sensitive subgroups (p = 0.006). Lack of GST M1 (GST M1*0/0, n = 27) tended to be more frequent only in UVB-sensitive subjects, and the proportion of the active GST M1 allelic variants *A and *B was similar in all UVB sensitivity subgroups. Three subjects with deficiencies in GST T1 and GST M1 had the most intense inflammatory responses. No effect of gender or genetic variations at the MC1R gene locus was established. Thus, heritable GST T1 deficiency may be a genetic determinant of individual skin sensitivity toward UV irradiation.

Influence of smoking in the glutathione-S-transferase M1 deficiency--associated risk for squamous cell carcinoma of the bladder in schistosomiasis patients in Egypt

In this study we show an effect of the glutathione-S-transferase M1 (GSTM1) null phenotype on the risk for squamous cell carcinoma (SCC) of the bladder among male smokers in Egypt, with an adjusted odds ratio of 4.8 (95% confidence interval: 1.06-21.77). However, no overall effect of the GSTM1 null phenotype on the risk for bladder SCC was observed.