Influence of GSTT1 and GSTM1 genotypes on sunburn sensitivity

Influence of functional variants Asp312Asn and Lys751Gln of Xeroderma Pigmentosum Group D (XPD) and Glutathione S-transferase Mu 1 (GSTM1) and Theta 1 (GSTT1) genes on cutaneous melanoma susceptibility and prognosis

We aimed to evaluate whether variants in repair (XPD Asp312Asn, XPD Lys751Gln) and detoxification (GSTM1, GSTT1) genes alter risk, clinicopathological aspects and survival of cutaneous melanoma (CM). Genotyping was performed in 229 CM patients and 258 controls. Individuals with XPD 312Asp/Asn or Asn/Asn plus GSTT1 null genotype were under 2.00 (95% CI: 1.06-3.79), and XPD 312Asn/Gln haplotype was under 1.44-fold (95% CI: 0.99-2.08) increased risks to CM than others. Individuals with GSTM1 plus GSTT1 null genotype had 9.61-fold (95% CI: 2.28-40.38) increased risk of metastatic CM. At 60 months of follow-up, patients with XPD 751Gln/Gln plus GSTT1 null and GSTM1 null plus GSTT1 null genotype presented 7.36 and 3.05 more chances of evolving to death in multivariate Cox analysis, respectively. In conclusion, our data indicate, for the first time, that specific variant combinations of XPD, GSTM1 and GSTT1 may increase susceptibility to CM and influence patients' clinicopathological features and survival.

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.

Induction of the phase 2 response in mouse and human skin by sulforaphane-containing broccoli sprout extracts

The isothiocyanate sulforaphane was isolated from broccoli extracts in a bioactivity-guided fractionation as the principal and very potent inducer of cytoprotective phase 2 enzymes and subsequently shown to inhibit tumor development in animal models that involve various carcinogens and target organs. Because broccoli and broccoli sprouts are widely consumed, extracts obtained from them are viewed as convenient vehicles for sulforaphane delivery to humans. In relation to our current interest in devising strategies for protection against UV light-induced skin cancer, it was necessary to examine the safety and efficacy of topical application of sulforaphane-containing broccoli sprout extracts as single and multiple doses in both mice and humans. Topical application of an extract delivering 100 nmol sulforaphane/cm(2) increased the protein levels of NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione S-transferase A1, and heme oxygenase 1, three representative phase 2 enzymes, in mouse skin epidermis. Quantitative assessment of the activity of NQO1 24 h after dosing showed increases of 1.5- and 2.7-fold after application of single and multiple (thrice, every 24 h) doses, respectively. A dose-escalation safety study in healthy human subjects revealed no adverse reactions when doses as high as 340 nmol of sulforaphane in the form of broccoli sprout extracts were applied topically to the center of a 1-cm-diameter circle drawn on the volar forearm. A subsequent efficacy study showed that despite the interindividual differences in basal levels, the enzyme activity of NQO1 in homogenates of 3-mm full thickness skin punch biopsies increased in a dose-dependent manner, with maximum increases of 1.5- and 4.5-fold after application of 150 nmol doses, once or three times (at 24 h-intervals), respectively, thus providing direct evidence for induction of the phase 2 response in humans.

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.

Regulation of cutaneous drug-metabolizing enzymes and cytoprotective gene expression by topical drugs in human skin in vivo

BACKGROUND

Individuality in the expression and regulation of hepatic drug-metabolizing enzymes (DMEs) and cytoprotective (CP) genes is an important determinant of treatment response. There is increasing evidence that many DMEs and CP genes are also expressed in human skin. Responses to topical drugs used to treat common skin diseases, such as psoriasis, are unpredictable and may potentially be rationalized, at least in part, by interindividual differences in cutaneous DME and CP gene expression.

OBJECTIVES

We investigated whether three topical drugs [coal tar, all-trans retinoic acid (atRA) and clobetasol 17-propionate] used in routine clinical practice modulated the expression of a variety of DME and CP genes [cytochrome P450s, glutathione S-transferases (GSTs) and drug transporters] in healthy human skin in vivo.

METHODS

Healthy adult volunteers (n = 30) were invited to participate in the study. Each subject was randomly allocated to receive two of the three study chemicals and one control site application. Crude coal tar (n = 13), atRA (n = 14) or clobetasol 17-propionate (n = 10) was applied under occlusion to photoprotected buttock skin for 96 h. A vehicle control (white soft paraffin) was also applied under the same conditions at an adjacent site in all subjects. Full-thickness punch biopsies (4-mm diameter) were then taken from treated and control sites. Total RNA was extracted and reverse transcribed into cDNA, which was used as a template in subsequent real-time polymerase chain reaction analysis, where fluorescent output was directly proportional to input cDNA concentration. Triplicate measurements of skin mRNA expression were made from each sample, and the arithmetic mean values taken. After logarithmic transformation, the paired t-test was used to compare values between treated and control skin.

RESULTS

Cytochrome P450s CYP1A1, CYP1A2, CYP1B1, CYP2C18, quinone reductase (NQO-1), GSTP1, gamma-glutamyl cysteine synthetase (gamma-GCS), glutathione peroxidase-1 (GPx-1), cyclooxygenase-2 (COX-2) and haem oxygenase-1 (HO-1) were induced by coal tar; CYP26, NADPH P450 reductase (CPR), GSTP1 and HO-1 by atRA; and CYP3A5 by clobetasol 17-propionate. In contrast, CYP1A1 and CYP1A2 expression was suppressed by atRA, and gamma-GCS and MRP1 by clobetasol 17-propionate. Marked interindividual variation in gene regulation by topical drugs was seen for the majority of genes examined.

CONCLUSIONS

These data demonstrate that topical drugs can modulate DME gene expression in human skin in vivo and indicate that variation in the expression and regulation of these genes may be a determinant of individuality in response to topical therapies for common skin diseases.

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.

[Solar keratosis: from precancerous lesion to pre-invasive squamous cell carcinoma--therapeutic approach with a bioinductive method]

BACKGROUND

Solar keratoses are precancerous lesions in chronically UV-damaged skin with histological features consistent with pre-invasive squamous cell carcinoma. They require therapeutic intervention in order to prevent progression towards invasive carcinoma. Treatment options include topical medications and destructive methods. We report on a new approach--topical bioinductive therapy with imiquimod 5% cream.

PATIENTS AND METHODS

In a prospective case series, 7 patients with solar keratoses have been treated with topical imiquimod 5%. The cream was applied 5 days/week over 2 weeks. After end of treatment, the outcome was assessed at regular control visits and, in some cases, histologically confirmed. One patient was followed up as untreated control.

RESULTS

In 6 of the 7 treated patients, the lesions cleared completely; one patient did not respond. The patients did not show new solar keratoses during a follow-up period of about 2 years. The untreated patient showed spontaneous clearance of his keratoses. Local skin reactions during treatment included erythema, oedema and erosions in varying degrees, all of which completely resolved.

CONCLUSIONS

Bioinductive therapy with imiquimod 5% cream represents a promising therapeutic approach for cutaneous precancerous lesions such as solar keratoses.

Proteomic identification of potential susceptibility factors in drug-induced liver disease

Drug-induced liver disease (DILD) causes significant morbidity and mortality and impairs new drug development. Currently, no known criteria can predict whether a drug will cause DILD or what risk factors make an individual susceptible. Although it has been shown in mouse studies that the disruption of key regulatory factors, such as cyclooxygenase-2 (COX-2), interleukin (IL)-6, and IL-10, increased susceptibility to DILD caused by acetaminophen (APAP), no single factor seems to be absolute. As an approach to better understand the multifactorial basis of DILD, we compared the hepatic proteome of mice that are resistant (SJL) and susceptible (C57Bl/6) to APAP-induced liver disease (AILD), using solution-based isotope-coded affinity tag (ICAT) liquid chromatography mass spectrometry. Several novel factors were identified that were more highly expressed in the livers of SJL mice, including those involved in stress response, cell proliferation and tissue regeneration, and protein modification, implicating these proteins as potential hepatoprotective factors. There was also a selective loss of several mitochondrial proteins from the livers of the susceptible C57Bl/6 mice, suggesting that the loss of functional mitochondria may indeed play a role in AILD. These findings indicate that comparative hepatic proteomic analyses of susceptible and resistant mouse strains may provide a global approach for identifying potential risk factors and mechanistic pathways responsible for DILD.

Glutathione S -transferase T1 polymorphisms are associated with outcome in colorectal cancer

Colorectal cancer (CRC) remains a significant cause of mortality accounting for approximately 10% of all deaths from malignancy in the western world. Polymorphism in the glutathione S-transferase GSTT1 gene has been associated with CRC risk in some but not all studies. In this study, we examined associations between GSTT1 genotypes and CRC risk, and prognosis in 361 cases and 881 unrelated controls. GSTT1 null was associated with a small but significant increase in risk (P = 0.0006, odds ratio (OR) = 1.65, 95% confidence interval (CI) = 1.22-2.24). GSTT1 null was also associated with a significantly younger age at diagnosis (mean 65.2 years) compared with GSTT1 A (mean 67.6 years, P = 0.031). There were no significant associations between GSTT1 genotypes and clinical factors (e.g. Dukes stage, differentiation and tumour node metastasis classification) in the total case group. However, following stratification by age (<70 versus > or =70 years at diagnosis), in the patients diagnosed <70 years of age, GSTT1 null was more common in Dukes grade A/B tumours (P = 0.046), stage T1/T2 tumours (P = 0.053) and those with a pushing margin (P = 0.066). We also identified associations between GSTT1 null and increased prevalence of host lymphocyte response, particularly in the younger patients (P = 0.036). Furthermore, GSTT1 null was associated with improved survival in younger patients (P = 0.017, hazards ratio (HR) = 0.52, 95% CI = 0.31-0.89) but poorer survival in older patients (P = 0.017, HR = 1.89, 95% CI = 1.12-3.20). We proposed a model based on the dual functionality of GSTT1 to explain these contrasting results. We suggest that the null genotype is associated with improved immune response in younger patients, but poorer detoxification in older patients. These findings may also provide an explanation for the contrasting finding of other studies on the role of this gene in CRC.

The genetics of sun sensitivity in humans

Humans vary >100-fold in their sensitivity to the harmful effects of ultraviolet radiation. The main determinants of sensitivity are melanin pigmentation and less-well-characterized differences in skin inflammation and repair processes. Pigmentation has a high heritability, but susceptibility to cancers of the skin, a key marker of sun sensitivity, is less heritable. Despite a large number of murine coat-color mutations, only one gene in humans, the melanocortin 1 receptor (MC1R), is known to account for substantial variation in skin and hair color and in skin cancer incidence. MC1R encodes a 317-amino acid G-coupled receptor that controls the relative amounts of the two major melanin classes, eumelanin and pheomelanin. Most persons with red hair are homozygous for alleles of the MC1R gene that show varying degrees of diminished function. More than 65 human MC1R alleles with nonsynonymous changes have been identified, and current evidence suggests that many of them vary in their physiological activity, such that a graded series of responses can be achieved on the basis of (i) dosage effects (of one or two alleles) and (ii) individual differences in the pharmacological profile in response to ligand. Thus, a single locus, identified within a Mendelian framework, can contribute significantly to human pigmentary variation.

High-throughput detection of glutathione s-transferase polymorphic alleles in a pediatric cancer population

Polymorphisms of glutathione S-transferase (GST) enzymes have been correlated with altered risk of several cancers, as well as altered response and toxicity from cancer chemotherapy. We report a low cost, highly reproducible and specific PCR-based high-throughput assay for genotyping different GSTs designed for use in large clinical trials. In comparison to an alternative genotyping method (single nucleotide extension), the sensitivity and specificity of the high throughput assay was shown to be 92 and 97%, respectively, depending on the source of genomic DNA. Using the high-throughput assay, we demonstrate by multivariate analysis an increased risk of acute lymphoblastic leukemia, glial brain tumors, and osteosarcoma for patients carrying nonnull alleles of GSTM1 and/or GSTT1.

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.