Detoxifying enzyme genotypes and susceptibility to cutaneous malignancy

Effects of the IL6 -174G>C promoter polymorphism and IL-6 serum levels on the progression of cutaneous malignant melanoma

Cutaneous malignant melanoma (CMM) is one of the most immunogenic types of cancer, with a 6-fold higher rate of spontaneous regression than any other malignancy. In addition to responsiveness to different immunotherapies, the immunogenicity of CMM highlights the important role of the host immune system in the response to CMM. The present study aimed to explore the role of two functional promoter polymorphisms [IL6 -174G>C (rs1800785) and TNFA -308G>A (rs1800629)] in the regulation of the genes encoding the pro-inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-α, specifically in patients with CMM. A total of 76 patients with CMM and 200 control subjects were genotyped using PCR-restriction fragment length polymorphism. The genotype frequencies for both single nucleotide polymorphisms (SNPs) did not differ significantly between the patients and controls (P=0.358 and P=0.810 for IL6 and TNFA, respectively). However, compared with carriers of C-allele genotypes (CG+CC), patients with the IL6 -174GG genotype exhibited more advanced melanoma (Clark scale ≥3; P=0.037) and shorter survival times, particularly those who worked outdoors (in conditions with increased sunlight exposure; P=0.016). Furthermore, the serum IL-6 levels of patients with CMM were significantly higher than those of the control subjects, which were associated with unfavorable blood and serum characteristics and tumor progression (development of new distant metastases; P=0.004), and with a shorter overall survival time (P=0.042). Using a Cox proportional hazard model, the IL6 -174GG genotype was found to be an independent prognostic factor for reduced survival time (P=0.030), together with sex (being male; P=0.004) and occupations with higher exposure to sunlight (P=0.047). In conclusion, the results of the present study indicated that the promoter polymorphisms IL6 -174G>C and TNFA -308G>A are not predisposing factors for CMM. However, the IL6 -174G>C SNP and IL-6 serum concentrations are likely to influence the progression of the disease, and the GG genotype and higher IL-6 serum levels may indicate shorter survival.

Basal cell carcinoma arising from the scrotum: An understated entity

Basal cell carcinoma (BCC) is the most commonly occurring carcinoma among humans. Reports of this lesion on nonexposed areas, such as the scrotum, soles, vulva, groin, pubic region, and axilla, are relatively uncommon. We present the case of a male patient with BCC located in the scrotum with a duration of 12 years who was successfully treated by local excision. Histopathology revealed infiltration by BCC. Our objective of this report is to remind specialists like urologists of the possibility of scrotal BCC when encountering scrotal lesions of unknown origin or not responding to topical treatments in a reasonable time frame.

Droplet Digital PCR Analysis of GSTM1 Deletion Polymorphism in Psoriatic Subjects Treated with Goeckerman Therapy

Goeckerman therapy (GT) represents an effective treatment of psoriasis including a combination of pharmaceutical grade crude coal tar (CCT) and ultraviolet irradiation (UV-R). Coal tar contains a mixture of polycyclic aromatic hydrocarbons. The best known carcinogenic polyaromate - benzo[a]pyrene is metabolized into a highly reactive benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE). Glutathione S-transferase M1 (GSTM1) catalyses the conjugation of drugs, toxins and products of oxidative stress with glutathione. The aim of the study is to found possible associations between GSTM1 genotypes and the level of BPDE-DNA adducts in 46 psoriatic patients treated with GT. For genotyping, droplet digital PCR was applied. The GSTM1 copy number was normalized to β-globin reference gene. In five GSTM1*1/*1 subjects, the GSTM1 to β-globin ratio moved from 0.99 to 1.03 with a median of 1.01. GSTM1*0/*1 heterozygotes (n = 20) contained only one GSTM1 function allele which conditioned the ratio 0.47-0.53 (median 0.50). GSTM1*0/*0 individuals (n = 21) showed no amplification of the null variants because of the large deletion in GSTM1. BPDE-DNA concentrations ranged from 1.8 to 66.3 ng/µg with a median of 12.3 ng/µg. GSTM1*0/*0 and GSTM1*0/*1 genotypes showed non-significantly higher concentrations of BPDE-DNA adducts than the GSTM1*1/*1 one (12.3 and 12.4 vs 7.8 ng/µg). The non-significant relationship between BPDE-DNA adducts and GSTM1 genotypes in psoriatic patients could be associated with relatively low doses of CCT and short-term UV-R exposures used in GT.

Associations of oxidative balance-related exposures with incident, sporadic colorectal adenoma according to antioxidant enzyme genotypes

PURPOSE

Previous research found inverse associations between oxidative balance and risk of colorectal adenoma. However, these measures were limited to extrinsic (dietary and lifestyle) exposures and did not account for intrinsic factors, specifically antioxidant enzymes responsible for cellular defense against oxidative stress. We investigated whether the association between an oxidative balance score (OBS) and colorectal adenoma may vary according to polymorphisms in genes that encode three antioxidant enzymes: Manganese superoxide dismutase (SOD2), catalase (CAT), and glutathione-S-transferase P1 (GSTP1).

METHODS

Using data pooled from three colonoscopy-based case-control studies of incident, sporadic colorectal adenoma, we constructed an OBS reflecting pro- and antioxidant exposures. We used multivariable logistic regression to assess whether the association between the OBS and colorectal adenoma differed according to polymorphisms in the genes encoding the antioxidant enzymes.

RESULTS

OBS was inversely associated with colorectal adenoma; adenoma risk was not associated with the genetic polymorphisms, and there was no consistent pattern of effect modification by individual genotypes or combined gene scores.

CONCLUSIONS

Variations in the antioxidant enzyme genes SOD2, CAT, and GSTP1 do not seem to substantially modify associations of environmental exposures related to oxidative balance with risk for sporadic colorectal adenoma.

Genetic predisposition for dermal problems in hexavalent chromium exposed population

We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108) along with asymptomatic controls (n = 148) from a non contaminated reference community. Exposed symptomatic group consisted of 36.8% subjects who were GSTM1 null genotyped as compared to asymptomatic where only 19.4% subjects were null. The exposed subjects with GSTM1 null genotype were more susceptible to dermal adversities in comparison with wild genotyped subjects (OR = 2.42; 95% CI = 1.071-5.451). Age, smoking, gender or duration of residence were not found to have any confounding effect towards this association. Association with other genes was not statistically significant, nonetheless, possible contribution by these genes cannot be ruled out. In conclusion, variation in the polymorphic status of GSTM1 gene may influence dermal outcomes among residents from Cr(VI) contaminated areas. Further studies are therefore, needed to examine these observations among different population groups.

Nonmelanoma skin cancer

Nonmelanoma skin cancer (NMSC) represents the most common form of cancer in Caucasians, with continuing increase in incidence worldwide. Basal cell carcinoma (BCC) accounts for 75% of cases of NMSC, and squamous cell carcinoma (SCC) accounts for the remaining majority of NMSC cases. Whilst metastasis from BCC is extremely rare, metastasis from high-risk SCC may be fatal. In this article, we review the aetiology, diagnosis and management of NMSC.

GSTM1, GSTT1 and GSTP1 gene polymorphism in polymorphous light eruption

BACKGROUND

Polymorphous light eruption (PLE) is the most common chronic and idiopathic photodermatosis. PLE is assumed to represent an immunological hypersensitivity reaction to a radiation-induced cutaneous antigen involving reactive oxygen species (ROS) on the basis of a genetic predisposition. Among others, cellular protection against ROS is provided by glutathione S-transferases (GSTs). Different variants of the GST enzymes may influence the activity and efficiency of detoxification and biotransformation of unknown UV-induced skin-antigens and other factors that may play an important role in the pathogenesis of PLE.

METHODS

In this study the relationship between isoenzymes of the GST genes GSTM1, GSTT1 and GSTP1 and possible protective or predisposing effects on PLE was examined in 29 patients and 144 controls. Diagnosis of PLE was based on the presence of characteristic clinical features.

RESULTS

No association between the functional polymorphisms of the GST gene family and PLE was found. Prevalence of certain GST isoenzymes or polymorphisms in patients with PLE did not differ from healthy controls.

CONCLUSION

Our data do not support prevalence of GST isoenzymes or polymorphisms as a protective effect against PLE. Especially a higher carrier frequency of GSTP1 Val(105) as a protective factor against PLE which has been published before could not be proved. The GST genotypes GSTM1, GSTT1 and GSTP1 (including SNPs) seem to have no relevant association with PLE.

Could Malassezia yeasts be implicated in skin carcinogenesis through the production of aryl-hydrocarbon receptor ligands?

Malassezia yeasts are found on the skin of all humans and many warm-blooded animals. In vitro they have the ability to synthesize potent ligands (indolo[3,2-b]carbazole, malassezin and indirubin) of the aryl-hydrocarbon receptor (AhR; synonym: dioxin receptor) when the sweat contained L-tryptophan is used as the single nitrogen source. The production of these AhR-ligands has been associated with pathogenic strains of a certain Malassezia species (Malassezia furfur) but recent evidence shows that this property is widely distributed in almost all currently known Malassezia species. AhR is associated with carcinogenesis and the potential connection of these ubiquitous skin symbionts, and putative pathogens, with skin neoplasia should be evaluated mainly focusing on mechanisms related to the distinctive ability of the yeast to produce potent AhR ligands.

HYPOTHESIS

Synthesis of available pertinent data show a possible link between Malassezia produced AhR ligands and skin carcinogenesis, particularly of basal cell carcinoma (BCC). BCCs are almost exclusively observed in animal species colonized by Malassezia. In humans and animals there is overlapping in the skin regions colonized by this yeast and affected by BCC. The potent AhR ligands synthesized by pathogenic Malassezia strains could contribute to tumor promotion by: modification of the UV radiation carcinogenesis, alterations in the salvage/survival of initiated tumor cells, inhibition of cell senescence, interaction with vitamin D metabolism, promotion of immune tolerance and finally pro-carcinogenic modulation of cell cycle progression and apoptosis.

Genetics of basal cell carcinoma

Basal cell carcinoma is the most common human malignancy in populations of European origin, and Australia has the highest incidence of basal cell carcinoma in the world. Great advances in the understanding of the genetics of this cancer have occurred in recent years. Mutations of the patched 1 gene (PTCH1) lead to basal cell carcinoma predisposition in Gorlin syndrome. PTCH1 is part of the hedgehog signalling pathway, and derangements within this pathway are now known to be important in the carcinogenesis of many different cancers including sporadic basal cell carcinoma. The molecular biology of the hedgehog pathway is discussed, and mouse models of basal cell carcinoma based on this pathway are explored. New developments in non-surgical treatment of basal cell carcinoma are based on this knowledge. Other genes of importance to basal cell carcinoma development include the tumour suppressor gene P53 and the melanocortin-1 receptor gene. In addition, we discuss molecules of possible importance such as the glutathione-S-transferases, DNA repair genes, cyclin-dependent kinase inhibitor 2A, Brahma and connexins. Evidence of familial aggregation of this cancer is explored and supports the possibility of genetic predisposition to this common malignancy.

Basal cell carcinoma: 10 years of experience

Introduction. Basal cell carcinoma (BCC) is a locally invasive malignant epidermal tumour. Incidence is increasing by 10% per year; incidence of metastases is minimal, but relapses are frequent (40%–50%). The complete excision of the BCC allows reduction of relapse. Materials and Methods. The study cohort consists of 1123 patients underwent surgery for basal cell carcinoma between 1999 and 2009. Patient and tumor characteristics recorded are: age; gender; localization (head and neck, trunk, and upper and lower extremities), tumor size, excisional margins adopted, and relapses. Results. The study considered a group of 1123 patients affected by basal cell carcinoma. Relapses occurred in 30 cases (2,67%), 27 out of 30 relapses occurred in noble areas, where peripheral margin was <3 mm. Incompletely excised basal cell carcinoma occurred in 21 patients (1,87%) and were treated with an additional excision. Discussion. Although guidelines indicate 3 mm peripheral margin of excision in BCC <2 cm, in our experience, a margin of less than 5 mm results in a high risk of incomplete excisions.

Focus on Basal cell carcinoma

Nonmelanoma skin cancers (NMSCs), which include basal and squamous cell cancers are the most common human cancers. BCCs have a relatively low metastatic rate and slow growth and are frequently underreported. Whilst there is a definite role of sunexposure in the pathogenesis of BCC, several additional complex genotypic, phenotypic and environmental factors are contributory. The high prevalence and the frequent occurrence of multiple primary BCC in affected individuals make them an important public health problem. This has led to a substantial increase in search for newer noninvasive treatments for BCC. Surgical excision with predetermined margins remains the mainstay treatment for most BCC. Of the newer non-invasive treatments only photodynamic therapy and topical imiquimod have become established in the treatment of certain BCC subtypes, while the search for other more effective and tissue salvaging therapies continues. This paper focuses on the pathogenesis and management of BCC.

Evidence that Gsta4 modifies susceptibility to skin tumor development in mice and humans

BACKGROUND

The incidence of nonmelanoma skin cancer (NMSC) is equivalent to that of all other cancers combined. Previously, we mapped the 12-O-tetradecanoylphorbol-13-acetate (TPA) skin tumor promotion susceptibility locus, Psl1, to distal chromosome 9 in crosses of sensitive DBA/2 mice with relatively resistant C57BL/6 mice. Here, we used the mouse two-stage skin carcinogenesis model to identify the gene(s) responsible for the effects of Psl1.

METHODS

Interval-specific congenic mouse strains (n ≥ 59 mice per strain) were used to more precisely map the Psl1 locus. Having identified glutathione S-transferase α4 (Gsta4) as a candidate tumor promotion susceptibility gene that mapped within the delimited region, we analyzed Gsta4-deficient mice (n = 62) for susceptibility to skin tumor promotion by TPA. We used quantitative polymerase chain reaction, western blotting, and immunohistochemistry to verify induction of Gsta4 in mouse epidermis following TPA treatment and biochemical assays to associate Gsta4 activity with tumor promotion susceptibility. In addition, single-nucleotide polymorphisms (SNPs) in GSTA4 were analyzed in a case-control study of 414 NMSC patients and 450 control subjects to examine their association with human NMSC. Statistical analyses of tumor studies in mice were one-sided, whereas all other statistical analyses were two-sided.

RESULTS

Analyses of congenic mice indicated that at least two loci, Psl1.1 and Psl1.2, map to distal chromosome 9 and confer susceptibility to skin tumor promotion by TPA. Gsta4 maps to Psl1.2 and was highly induced (mRNA and protein) in the epidermis of resistant C57BL/6 mice compared with that of sensitive DBA/2 mice following treatment with TPA. Gsta4 activity levels were also higher in the epidermis of C57BL/6 mice following treatment with TPA. Gsta4-deficient mice (C57BL/6.Gsta4(-/-) mice) were more sensitive to TPA skin tumor promotion (0.8 tumors per mouse vs 0.4 tumors per mouse in wild-type controls; difference = 0.4 tumors per mouse; 95% confidence interval = 0.1 to 0.7, P = .007). Furthermore, inheritance of polymorphisms in GSTA4 was associated with risk of human NMSC. Three SNPs were found to be independent predictors of NMSC risk. Two of these were associated with increased risk of NMSC (odds ratios [ORs] = 1.60 to 3.42), while the third was associated with decreased risk of NMSC (OR = 0.63). In addition, a fourth SNP was associated with decreased risk of basal cell carcinoma only (OR = 0.44).

CONCLUSIONS

Gsta4/GSTA4 is a novel susceptibility gene for NMSC that affects risk in both mice and humans.

Polymorphisms of glutathione-S-transferase genes and the risk of aerodigestive tract cancers in the Northeast Indian population

BACKGROUND

Widespread use of tobacco and betel quid consumption and a high incidence of tobacco-associated aerodigestive tract cancers have been reported in different ethnic groups from several regions of Northeast (NE) India. This study was done to explore the possibility of phase II metabolic enzymes being responsible for the high prevalence of cancers in this region of India.

METHODS

Samples from 370 cases with oral, gastric, and lung cancers and 270 controls were analyzed for polymorphism of glutathione-S-transferase (GST) genes using polymerase chain reaction-restriction fragment length polymorphism-based methods.

RESULTS AND CONCLUSIONS

Tobacco smoking and betel quid chewing were found to be high risk factors for oral and lung cancers but not for gastric cancer, whereas tobacco chewing was found to be a risk factor for oral cancer but not for gastric or lung cancer. The variant genotypes of GSTP1 were not associated with any of the aerodigestive tract cancers. GSTT1 and GSTM1 null genotypes appeared to play a protective role for lung cancer (odds ratio [OR] = 0.47, 95% confidence interval [95% CI]: 0.24-0.93, p = 0.03) and (OR = 0.52, 95% CI: 0.28-0.96, p = 0.04), but they were not associated with oral and gastric cancers. However, when data was analyzed in different geographic regions the GSTT1 null genotype was found to be a significant risk factor for oral (OR = 2.58, 95% CI 1.01-6.61, p = 0.05) as well as gastric cancer (OR = 3.08, 95% CI 1.32-7.19, p = 0.009) in samples obtained from the Assam region of NE India. This is the first study on the association of GST polymorphisms and aerodigestive tract cancers in the high-risk region of NE India.

Basal cell carcinoma: what's new under the sun

Basal cell carcinoma (BCC) is the most common skin cancer in white populations with an increasing incidence worldwide, thereby imposing an important public health problem. Its etiology is still unclear, but existing data indicate that the risk for BCC development is of multifactorial origin and results from the interplay of both constitutional and environmental factors. Yet, UV radiation (UVR) is believed to be the predominant causative risk factor in the pathogenesis of BCC. For years, BCC and squamous cell carcinoma (SCC) have been grouped together as "nonmelanoma skin cancer." However, it seems that there are considerable biologic differences between BCC and SCC, and thus each type of epithelial cancer should be addressed separately. The present review provides an overview of the intriguing etiologic link of BCC with UVR and attempts a comprehensive review of recent epidemiologic and molecular evidence that supports this association.

Association study between sick building syndrome and polymorphisms of seven human detoxification genes in the Japanese

Sick building syndrome (SBS) is a chronic disorder caused by exposure to diverse indoor environmental or chemical pollutants. This study examined the association between seven detoxification genes (CYP1A1, CYP2E1, EPHX1, GSTM1, GSTT1, GSTP1, and NAT2) and SBS in the Japanese population. One hundred eighty patients with SBS and 401 healthy controls were enrolled in this study. We examined the prevalence for total of eleven genetic polymorphisms of detoxification genes. However, no statistically significant differences in allele and genotype frequency distributions of eleven genetic polymorphisms of these detoxification genes were found between patients and controls. On this basis, we conclude that the polymorphisms that we assessed for the detoxification genes do not contribute to the etiology of SBS.

Non-melanoma skin cancer

The rising incidence and morbidity of non-melanoma skin cancers has generated great interest in unravelling of their pathogenesis and in the search for new non-invasive treatments. Whereas the role of cumulative sun exposure in pathogenesis of squamous-cell carcinoma seems clear, the relation between sun-exposure patterns and subtypes of basal-cell carcinoma remains undetermined. Several complex genotypic, phenotypic, and environmental factors contribute to pathogenesis of non-melanoma skin cancers. Unlike basal-cell carcinoma, squamous-cell carcinomas can arise from precursor lesions. Diagnosis of non-melanoma skin cancer is made clinically and confirmed by histological testing. Prognosis depends on lesion and host characteristics, which also dictate choice of treatment. Prevention strategies aim at reduction of sun exposure, but are of unproven benefit, especially for basal-cell carcinoma. Surgical excision with predetermined margins is the mainstay of treatment for squamous-cell carcinoma and for most basal-cell carcinomas. Of the new non-invasive treatments, only photodynamic therapy and topical imiquimod have become established treatments for specific subtypes of basal-cell carcinoma, and the search for more effective and tissue-salvaging therapies continues.

Patterns of persistent DNA damage associated with sun exposure and the glutathione S-transferase M1 genotype in melanoma patients

Solar radiation can lead to changes affecting DNA metabolism resulting in loss of DNA integrity. Skin specimens obtained from melanoma patients treated at the Memorial Sloan-Kettering Cancer Center were used to study patterns of DNA fragmentation using the comet assay and levels of deletions in mitochondrial DNA (mtDNA) using real-time PCR. Skin specimens were classified according to the glutathione S-transferase M1 (GSTM1) genotype (either wild type [WT] or null) and patient sunburn history. GSTM1 null individuals with a sunburn history showed increased levels of both DNA fragmentation by comet assays and mtDNA deletions relative to GSTM1 WT patients with little or no sunburn history. Microarray analyses identified a number of genes whose expression was upregulated >or=5-fold in cells from GSTM1-null patients or from those reporting histories of sunburn. These genes encoded small molecule transporters, various growth factor/chemokine receptors, transcription factors and tumor suppressors. Of 17 genes directly involved in DNA repair, three DNA ligases were highly upregulated while the RAD23 UV excision repair gene and the Growth Arrest and DNA Damage gene (GADD45) were downregulated. These findings support the idea that exposure to solar radiation early in life may induce long-term cellular changes that lead to persistent DNA damage and altered patterns of gene expression.

A summary measure of pro- and anti-oxidant exposures and risk of incident, sporadic, colorectal adenomas

Despite compelling basic science evidence, the search for causal associations linking specific pro- and anti-oxidants to presumably oxidative stress-related neoplasms, such as colorectal adenoma, has produced inconsistent results. We developed an oxidative balance score (OBS) to characterize the pro-oxidant and anti-oxidant exposures of 2,305 participants in a case-control study of colorectal adenoma that used both endoscopy-confirmed and community controls. Twelve lifestyle medical and dietary factors with known pro- or anti-oxidant properties were considered. Each high anti-oxidant exposure and low pro-oxidant exposure was awarded one or two points depending on the level of exposure, and the points for each OBS component were summed. We observed a significant inverse association between OBS (continuous variable) and colorectal adenoma in the analyses with either community, or endoscopy controls (each p-trend < 0.01). When the OBS was treated as an ordinal variable and a score of <or=3 points was used as the referent category, in the analyses with the endoscopy controls the adjusted odds ratios for scores of 4-6, 7-9, 10-12, 13-15, and 16+, were 0.42, 0.32, 0.22, 0.20, and 0.19, respectively, with all 95% confidence intervals excluding 1.0. The corresponding analysis for community controls showed a similar trend. Our findings are in line with the basic science evidence supporting the role of oxidative stress in colorectal neoplasia.

GSTM1 and APE1 genotypes affect arsenic-induced oxidative stress: a repeated measures study

BACKGROUND

Chronic arsenic exposure is associated with an increased risk of skin, bladder and lung cancers. Generation of oxidative stress may contribute to arsenic carcinogenesis.

METHODS

To investigate the association between arsenic exposure and oxidative stress, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was evaluated in a cohort of 97 women recruited from an arsenic-endemic region of Bangladesh in 2003. Arsenic exposure was measured in urine, toenails, and drinking water. Drinking water and urine samples were collected on three consecutive days. Susceptibility to oxidative stress was evaluated by genotyping relevant polymorphisms in glutathione-s transferase mu (GSTM1), human 8-oxoguanine glycosylase (hOGG1) and apurinic/apyrimidinic endonuclease (APE1) genes using the Taqman method. Data were analyzed using random effects Tobit regression to account for repeated measures and 8-OHdG values below the detection limit.

RESULTS

A consistent negative effect for APE1 was observed across water, toenail and urinary arsenic models. APE1 148 glu/glu + asp/glu genotype was associated with a decrease in logged 8-OHdG of 0.40 (95%CI -0.73, -0.07) compared to APE1 148 asp/asp. An association between total urinary arsenic and 8-OHdG was observed among women with the GSTM1 null genotype but not in women with GSTM1 positive. Among women with GSTM1 null, a comparison of the second, third, and fourth quartiles of total urinary arsenic to the first quartile resulted in a 0.84 increase (95% CI 0.27, 1.42), a 0.98 increase (95% CI 033, 1.66) and a 0.85 increase (95% CI 0.27, 1.44) in logged 8-OHdG, respectively. No effects between 8-OHdG and toenail arsenic or drinking water arsenic were observed.

CONCLUSION

These results suggest the APE1 variant genotype decreases repair of 8-OHdG and that arsenic exposure is associated with oxidative stress in women who lack a functional GSTM1 detoxification enzyme.

Ultraviolet light induced alteration to the skin

Solar light is the primary source of UV radiation for all living systems. UV photons can mediate damage through two different mechanisms, either by direct absorption of UV via cellular chromophores, resulting in excited states formation and subsequent chemical reaction, or by phosensitization mechanisms, where the UV light is absorbed by endogenous (or exogenous) sensitizers that are excited and their further reactions lead to formation of reactive oxygen species (ROS). These highly reactive species can interact with cellular macromolecules such as DNA, proteins, fatty acids and saccharides causing oxidative damage. Direct and indirect injuries result in a number of harmful effects such as disrupted cell metabolism, morphological and ultrastructural changes, attack on the regulation pathways and, alterations in the differentiation, proliferation and apoptosis of skin cells. Processes like these can lead to erythema, sunburn, inflammation, immunosuppression, photoaging, gene mutation, and development of cutaneous malignancies. The endogenous and exogenous mechanisms of skin photoprotection are discussed.

Hypothesis: oxidative stress score as a combined measure of pro-oxidant and antioxidant exposures

PURPOSE

To explore the hypothesis that a combination of several risk factors acting through the same pathway may produce an overall large increase in risk even in the presence of weak associations with each individual factor.

METHODS

Using oxidative stress pathway as an example, we propose an oxidative stress score (OSS), where high and low pro-oxidant exposures expressed as continuous variables are assigned values of 0 and 1, while high and low antioxidant exposures are assigned values of 1 and 0, respectively. Dichotomous variables for pro-oxidant and antioxidant exposures are scored in a similar fashion. All individual scores are then summed to calculate the overall OSS, where higher and lower values indicate a shift toward antioxidant and pro-oxidant exposures, respectively.

RESULTS

We illustrate this approach by using data from two previously-conducted case-control studies: a colonoscopy-based colorectal adenoma study, and a population-based prostate cancer study. In this pilot illustration we found a substantial decrease in risk associated with a high OSS for both prostate cancer and colorectal adenoma. By contrast, analyses for individual OSS components demonstrated no discernible pattern.

CONCLUSIONS

Our exploratory analyses serve as a demonstration of a method and warrant further confirmation on a larger scale.

DNA repair gene polymorphisms and genetic predisposition to cutaneous melanoma

The incidence of cutaneous melanoma is rising rapidly in a number of countries. The key environmental risk factor is exposure to the ultraviolet (UV) component in sunlight. The nucleotide excision repair (NER) pathway deals with the main forms of UV-induced DNA damage. We have investigated the hypothesis that polymorphisms in NER genes constitute genetic susceptibility factors for melanoma. However, not all melanomas arise on sun-exposed sites and so we investigated the hypothesis that genes involved in other pathways for the repair of oxidative DNA damage may also be involved in susceptibility to melanoma. Scotland, with its high incidence of melanoma and stable homogeneous population, was ideal for this case-control study, involving 596 Scottish melanoma patients and 441 population-based controls. Significant associations were found for the NER genes ERCC1 and XPF, with the strongest associations for melanoma cases aged 50 and under [ERCC1 odds ratio (OR) 1.59, P = 0.008; XPF OR 1.69, P = 0.003]. Although an XPD haplotype was associated with melanoma, it did not contain the variant 751 Gln allele, which has been associated with melanoma in some previous studies. No associations were found for the base excision repair and DNA damage response genes investigated. An association was also found for a polymorphism in the promoter of the vitamin D receptor gene, VDR (OR 1.88, P = 0.005). The products of the two NER genes, ERCC1 and XPF, where associations with melanoma were found, act together in a rate-limiting step in the repair pathway.

Glutathione S-transferase and CYP1A1 gene polymorphisms and non-melanoma skin cancer risk in Italian transplanted patients

Solid organ transplant recipients are at higher risk of non-melanoma skin cancer (NMSC), especially basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Genetic alterations in the production of detoxifying enzymes such as glutathione S-transferase (GST) and CYP1A1 may enhance this risk. We investigated the frequency of GST genotypes (GSTM1, GSTM3, GSTT1 and GSTP1) and CYP1A1 in 239 transplant recipients: 107 cases with NMSC and 132 controls free from NMSC matched for type of transplanted organ, duration of transplantation, sex and age. Allele GSTP1*A was associated with a higher risk of NMSC [odds ratio (OR) 1.7 (1.1-2.5); P = 0.017]. Homozygosity for allele GSTP1 Val(105) was lower in cases [OR 0.3 (0.1-0.8); P = 0.012], especially in patients with SCC [OR 0.1 (0.0-0.7); P = 0.012]. A higher risk of BCC was found in patients with GSTM1 null/null [null/null versus A + B, OR 3.1 (1.4-6.8); P = 0.003]. Analysis of allelism and interaction between allelic variants showed significant association between combined GSTM1 and CYP1A1 Val(462) genotypes, where individuals homozygous for the risk allele GSTM1 null and carrying also the allele CYP1A1 Val(462), show a higher risk of developing NMSC [OR 4.5 (1.1-21.4); P = 0.03], especially SCC [OR 6.5 (1.4-34.4); P = 0.01]. GSTP1 polymorphisms are associated with both BCC and SCC risk. GSTM1 polymorphisms seem to be involved in BCC risk, while GSTM1 null/null genotype combined with CYP1A1 allele Val(462) are associated with a higher risk for SCC, indicating that allelism and/or interactions between allelic variants at other loci may also influence the risk of NMSC, particularly SCC.

Variations of the melanocortin-1 receptor and the glutathione-S transferase T1 and M1 genes in cutaneous malignant melanoma

Variations in the melanocortin-1 receptor (MC1R) and in the glutathione-S transferase genes mu1 (GSTM1) and theta 1 (GSTT1) have been reported to influence UV sensitivity and melanoma risk. MC1R is one of the major genes that determine skin pigmentation because the melanocortin-1 receptor regulates eumelanin synthesis. GSTT1 and GSTM1 are enzymes expressed in the skin that detoxify products of oxidative stress reactions caused by UV irradiation. In this study variations in the MC1R, GSTM1 and T1 genes were analyzed in 347 healthy subjects and 322 patients with cutaneous malignant melanoma by direct cycle sequencing, RFLP and multiplex PCR. Important phenotypic characteristics of the study participants were obtained to assess whether genetic associations occurred independently of phenotypic risk factors for melanoma. We found an association of the MC1R D84E and R151C polymorphisms with melanoma (odds ratios for carriage of the rare allele 4.96, 95% CI [1.06-23.13], P = 0.032, and 1.69, 95% CI [1.12-2.55], P = 0.013, respectively). Melanoma risk increased with the number of variant MC1R alleles carried by an individual (P = 0.003). In a multivariate model, however, only the D84E polymorphism influenced melanoma risk independently of the risk factors fair skin type, high nevus count and high age (P = 0.047). There was no effect of homozygous GST M1 or T1 deletions on melanoma risk. In contrast to previous data, there was no evidence that GSTM1 deficiency influences melanoma risk in the subgroup of individuals with red or blond hair.

Lycopene Intake and Prostate Cancer Risk: Effect Modification by Plasma Antioxidants and the XRCC1 Genotype

Lycopene has been associated with reduced prostate cancer risk, although the results of epidemiological studies have varied. We hypothesize that an effect of lycopene may be modified by XRCC1 genotype and other antioxidants. We used a food-frequency questionnaire to assess lycopene intake in a case-control study of prostate cancer in North Carolina. Plasma alpha-tocopherol and beta-carotene levels were measured using high-performance liquid chromatography. XRCC1 genotypes were detected using polymerase chain reaction-restriction fragment length polymorphism. The final dataset included 77 cases and 174 controls with complete questionnaires, genotyping, and plasma analyses. Among men with the Arg/Arg genotype at codon 399, odds ratios (ORs) for prostate cancer risk associated with medium (732-1,529 microg/day) and high (>1,529 microg/day) lycopene intake were 0.59 (95% confidence interval = 0.23-1.50) and 0.21 (0.06-0.71), respectively (P(trend) < 0.01). Similar analyses for persons with Arg/Gln or Gln/Gln genotypes produced null results. Above-median (1,048 microg/day) lycopene intake combined with above-median levels of alpha-tocopherol and beta-carotene was associated with an OR of 0.11 (0.02-0.65) among men with the Arg/Arg genotype but not those with at least one Gln allele (P(interaction) = 0.01). Although limited by small sample size, these findings indicate that the association between lycopene and prostate cancer is complex and may be modified by other antioxidants and by XRCC1 genotype.

Occupational sunlight exposure, polymorphism of glutathione S-transferase M1, and senile cataract risk

BACKGROUND

The pathogenesis of cataract is influenced by a number of factors including oxidative stress. Glutathione S-transferase (GST) catalyses the nucleophilic addition of the thiol of GST to electrophilic acceptors. It is important for detoxification of xenobiotics in order to protect tissues from oxidative damage.

OBJECTIVES

To examine whether the interaction of polymorphism of GSTM1 gene and occupational sunlight exposure modulate the risk of cataract.

METHODS

Blood samples from 95 subjects with cataract and 95 age and sex matched healthy persons were collected. The genotypes of GSTM1 were determined using PCR.

RESULTS

The null genotype of GSTM1 was associated with an increase in cataract risk in the indoor workplace, but this association was not significant in the outdoor subjects.

CONCLUSION

The active genotype of GSTM1 has lost its protective role in persons who work outdoors. It is suggested that activity of the GSTmu enzyme may be inhibited in the human lens after occupational exposure to UV light.

Molecular mechanisms and biological plausibility underlying the malignant transformation of endometriosis: a critical analysis

Although population-based studies have unequivocally reported an increased risk of ovarian cancer in women with endometriosis, the biological evidence supporting the idea of endometriosis as a preneoplastic condition is scanty and not well substantiated. The fundamental features of human neoplasms (monoclonal growth, genetic changes, mutations in tumour suppressor genes and replicative advantage) have been evaluated in endometriotic lesions but results obtained are discordant. It is plausible that ectopic glands may expand monoclonally but the entity of this phenomenon is debated. According to some allelotyping studies, from one-third to one-half of endometriosis lesions would harbour somatic genetic changes in chromosomal regions supposed to contain genes involved in ovarian tumourigenesis, especially for the endometrioid histotype. These findings would be consistent with the progression model for carcinogenesis from the benign precursor to ovarian cancer but they could not be unequivocally replicated. Gene mutational studies are rare in this context. A single group has found missense mutations and deletions of PTEN gene in about 20% of ovarian endometriotic cysts. Moreover, in a model of genetically engineered mice harbouring an oncogenic allele of K-ras resulting in benign lesions reminiscent of endometriosis, a conditional deletion of PTEN caused the progression towards the endometrioid tumour. Based on these data, the causal link between endometriosis and ovarian endometrioid/clear cell carcinomas remains to be defined both in terms of entity of association and of underlying molecular mechanisms.

Influence of oral antioxidants on ultraviolet radiation-induced skin damage in humans

Ultraviolet radiation (UVR) causes a range of acute and chronic adverse cutaneous effects, in addition to some beneficial effects. In present times, the skin is generally exposed to higher levels of UVR, such that inherent defence mechanisms become overwhelmed. Complications, notably skin malignancies, show a serious rise in incidence. Since many effects of UVR are mediated through generation of reactive oxygen species, antioxidant supplementation provides a strategy to combat their excess generation, and hence reduce the clinical consequences. Human supplementation studies examining the potential of a range of oral agents to protect against UVR-induced skin effects show mixed results; further studies should examine whether certain subgroups of the population may show augmented benefit.

Cytochrome P4501A1 polymorphism is associated with susceptibility to acute lymphoblastic leukemia in adult Mexican patients

We studied the role of cytochrome P4501A1 (CYP1A1 Val/Val) genotypes in the etiology of acute lymphoblastic leukemia (ALL) in adult Mexican patients. Distributions of CYP1A1 Val/Val genotypes in peripheral blood DNA samples from 136 healthy controls and 136 adult patients with ALL were evaluated. There was an increased frequency of the CYP1A1 Val/Val genotype among ALL patients, showing a significant association between this genotype and the risk of developing ALL.

Epidemiology and aetiology of basal cell carcinoma

Basal cell carcinoma is the most common malignancy among caucasians worldwide. Accurate epidemiological data can be difficult to obtain, but does suggest that the overall incidence is increasing. Risk factors include skin type, prior skin cancers and immunosuppression. Research in free radical-mediated cellular injury and innate defence mechanisms, and ultraviolet radiation-induced genetic mutations have improved our understanding of the development of this disorder.

Quantitative real-time reverse transcription-polymerase chain reaction analysis of drug metabolizing and cytoprotective genes in psoriasis and regulation by ultraviolet radiation

There are unpredictable inter-individual differences in response to ultraviolet radiation, used in the treatment of psoriasis and other common skin diseases. It is therefore essential that we attempt to identify phenotypic markers that correlate with individual treatment outcomes. Exposure of human skin to ultraviolet radiation results in the generation of reactive intermediates and oxidative stress. Hepatic drug metabolizing and cytoprotective genes are induced as an adaptive response to xenobiotics and reactive intermediates; as several of these genes are present in skin, we hypothesized that their cutaneous expression and regulation may be implicated in responses to ultraviolet radiation. We used quantitative real-time reverse transcription-polymerase chain reaction to investigate interindividual differences in the cutaneous expression of a variety of drug metabolizing and cytoprotective genes, including cytochrome P450s, glutathione S-transferases and drug transporters, and investigated the regulation of gene expression by ultraviolet radiation and in lesional psoriatic skin. We confirmed significant induction of cyclooxygenase 2 (mean 3.63-fold, range 0.14-22.6, p<0.0001) by ultraviolet radiation and showed more modest (approximately 2-fold) inductions of glutathione peroxidase, and novel inductions of glutathione S-transferase P1 and the drug transporter multidrug resistance associated protein-1. Glutathione S-transferase P1 (3.74-fold, 1.3-33.1, p<0.0001) and multidrug resistance associated protein-1 (4.06-fold, 1.3-24.8, p<0.0001) were also significantly increased in psoriatic plaque, as were P450 CYP2E1 (3.64-fold, 1-28.9 p<0.0001) and heme oxygenase-1 (10.19-fold, 2.9-49.7, p<0.0001), implying a differential adaptive response to oxidant exposure in lesional psoriatic skin. We found considerable interindividual variation in constitutive gene expression and inducibility, indicating that these genes may be associated with individuality in response to ultraviolet radiation.

Exposure to soil contaminated with an environmental PCB/PCDD/PCDF mixture modulates ultraviolet radiation-induced non-melanoma skin carcinogenesis in the Crl:SKH1-hrBR hairless mouse

Chlorinated aromatic contaminants are active in carcinogenic processes within the skin and may have the potential to modulate ultraviolet radiation (UV)-induced skin carcinogenesis. Exposure to a complex environmental PCB/PCDD/PCDF mixture (polychlorinated biphenyls/polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans) during the irradiation phase of photocarcinogenesis was associated with significant (P < or = 0.001) reductions in papilloma incidence and squamous cell carcinoma multiplicity at irradiated skin sites. This protective effect was associated with significantly (P < 0.0001) reduced chronic epidermal thickening in UV and contaminant-exposed mice compared with mice exposed to UV only. Contaminant exposure was also associated with increased UV absorbance of skin methanol extracts implying a sunscreen-like effect.

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.

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.