Multiple cutaneous basal cell carcinomas: glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) polymorphisms influence tumour numbers and accrual

Natural product-loaded lipid-based nanocarriers for skin cancer treatment: An overview

The skin is essential for body protection and regulating physiological processes. It is the largest organ and serves as the first-line barrier against UV radiation, harmful substances, and infections. Skin cancer is considered the most prevalent type of cancer worldwide, while melanoma skin cancer is having high mortality rates. Skin cancer, including melanoma and non-melanoma forms, is primarily caused by prolonged exposure to UV sunlight and pollution. Currently, treatments for skin cancer include surgery, chemotherapy, and radiotherapy. However, several factors hinder the effectiveness of these treatments, such as low efficacy, the necessity for high concentrations of active components to achieve a therapeutic effect, and poor drug permeation into the stratum corneum or lesions. Additionally, low bioavailability at the target site necessitates high doses, leading to skin irritation and further obstructing drug absorption through the stratum corneum. To overcome these challenges, recent research focuses on developing a medication delivery system based on nanotechnology as an alternative to this traditional approach. Nano-drug delivery systems have demonstrated great promise in treating skin cancer by providing a more effective means of delivering drugs with better stability and drug absorption. An overview of various lipid-based nanocarriers is given in this review article that are utilized to carry natural compounds to treat skin cancer.

Exposure to nickel chloride induces epigenetic modification on detoxification enzyme glutathione S-transferase M2

Nickel (Ni) is a human carcinogen with genotoxic and epigenotoxic effects. Environmental and occupational exposure to Ni increases the risk of cancer and chronic inflammatory diseases. Our previous findings indicate that Ni alters gene expression through epigenetic regulation, specifically impacting E-cadherin and angiopoietin-like 4 (ANGPTL4), involved in epithelial-mesenchymal transition and migration. GST-M2, a member of the glutathione S-transferase (GST) enzyme family, plays a crucial role in cellular defense against oxidative damage and has been increasingly associated with cancer. GST-M2 overexpression inhibits lung cancer invasion and metastasis in vitro and in vivo. Hypermethylation of its promoter in cancer cells reduces gene expression, correlating with poor prognosis in non-small-cell lung cancer patients. The impact of Ni on GST-M2 remains unclear. We will investigate whether nickel exerts regulatory effects on GST-M2 through epigenetic modifications. Additionally, metformin, an antidiabetic drug, is being studied as a chemopreventive agent against nickel-induced damage. Our findings indicate that nickel chloride (NiCl2 ) exposure, both short-term and long-term, represses GST-M2 expression. However, the expression can be restored by demethylation agent 5-aza-2'-deoxycytidine and metformin. NiCl2 promotes hypermethylation of the GST-M2 promoter, as confirmed by methylation-specific PCR and bisulfite sequencing. Additionally, NiCl2 also influences histone acetylation, and metformin counteracts the suppressive effect of NiCl2 on histone H3 expression. Metformin reestablishes the binding of specificity protein 1 to the GST-M2 promoter, which is otherwise disrupted by NiCl2 . These findings elucidate the mechanism by which Ni reduces GST-M2 expression and transcriptional activity, potentially contributing to Ni-induced lung carcinogenesis.

Recent Advances in Diagnostic and Therapeutic Approaches for Breast Cancer: A Comprehensive Review

A silent monster, breast cancer, is a challenging medical task for researchers. Breast cancer is a leading cause of death in women with respect to other cancers. A case of breast cancer is diagnosed among women every 19 seconds, and every 74 seconds, a woman dies of breast cancer somewhere in the world. Several risk factors, such as genetic and environmental factors, favor breast cancer development. This review tends to provide deep insights regarding the genetics of breast cancer along with multiple diagnostic and therapeutic approaches as problem-solving negotiators to prevent the progression of breast cancer. This assembled data mainly aims to discuss omics-based approaches to provide enthralling diagnostic biomarkers and emerging novel therapies to combat breast cancer. This review article intends to pave a new path for the discovery of effective treatment options.

Development of Multiple-Lesion Basal Cell Carcinoma of the Skin: A Comprehensive Review

An interesting clinical feature of basal cell carcinoma (BCC) of the skin is a marked variation in tumor number, sites, and accrual. Some individuals develop only a single BCC lesion with no impact on health status, while a significant proportion is affected repeatedly with new primary tumors at various body sites. Approximately 29% of patients with a first BCC will develop at least 1 more lesion during their lifetime. The candidate predictors for multiple BCC development include younger age and a superficial BCC subtype at the time of the first diagnosis, red hair phenotype, initial or frequent tumor location on the trunk or on the upper limbs, and male gender. The pathogenesis of multiple BCC development does not seem to be related to greater UVR exposure. Individual genetic susceptibility may have a greater impact than extrinsic factors. In clinical practice, it is meaningful to estimate the probability of new BCC development in patients who have an initial lesion. A reliable prediction model for individualized risk stratification remains a subject of continued research; however, a focus on the risk factor profile is beneficial for clinical screening and may help clinicians to determine the individuals who should be followed up more closely.

Evidence-based update on rosacea comorbidities and their common physiologic pathways

Rosacea is a common chronic inflammatory disease affecting the facial skin whose etiology and pathophysiology are the subject of much investigation. Risk factors include genetic and environmental elements that may predispose individuals to localized inflammation and abnormal neurovascular responses to stimuli. Recent studies have introduced an array of systemic rosacea comorbidities, such as inflammatory bowel disease and neurologic conditions, that can be challenging to synthesize. We critically review the current data behind reported rosacea comorbidities and identify and highlight underrecognized physiologic mediators shared among rosacea and associated comorbidities. This information may be helpful in addressing patient questions about potential systemic implications of rosacea and can serve as a candidate platform for future research to understand rosacea and improve treatments.

Basal Cell Carcinoma: Review of Epidemiology, Pathogenesis, and Associated Risk Factors

Background:

Basal cell carcinoma (BCC) is extremely common, and its incidence continues to rise.

Objective:

This review presents the literature pertaining to the epidemiology, pathogenesis, and risk factors associated with BCC.

Conclusions:

The risk of developing BCC depends on both genetic predisposition and exposure to risk. Fair-skinned people account for the overwhelming majority of patients, beyond what would be expected by skin phototype alone. Damage to multiple lines of defense appears to be necessary for cancer development and spread. This damage distorts the concerted effort of deoxyribonucleic acid (DNA) repair, immunosurveillance, and cellular growth regulation to protect against malignant progression. Ultraviolet light exposure is the most critical modifiable factor determining early expression and frequency of BCC development.

Elevated 8-Isoprostane Levels in Basal Cell Carcinoma and in Uva Irradiated Skin

Isoprostanes are prostaglandin isomers produced from the peroxidation of polyunsaturated fatty acids from the cellular membrane. They have been used as a specific index of cellular lipoperoxidation and as an indirect measure of oxidative stress. However, these molecules also present several biological activities. An oxidative environment measured as the presence of other indirect measurements of reactive oxygen species lipoperoxidation has recently been described in basal cell carcinoma, the most frequent type of non-melanoma skin cancer. This study aims to measure the levels of 8-isoprostaglandin F2α, an isoprostane widely studied in other models as a by-product of ROS-induced lipid peroxidation, in basal cell carcinoma and in UVA irradiated healthy skin. We found that 8-iso-PGF2α is present in higher levels in BCC specimens compared to healthy non sun-exposed skin, confirming previous studies on the production of lipoperoxidation in this tumor. Moreover, we demonstrated that topical pre-treatment with a compound containing vitamin E is capable of reducing 8-iso-PGF2α formation in UV irradiated skin suggesting a role for isoprostanes in UV induced inflammation and eventually carcinogenesis and confirming the function of vitamin E as an antioxidant in this model.

Etiology and pathogenesis of basal cell carcinoma

Basal cell carcinoma (BCC) is the most common cancer among Caucasians. It generally occurs on sun-exposed areas of the body, mostly on the head and neck (80%), trunk (15%), rarely on arms and legs. Basal cell carcinoma is a good example of a disease caused by a combination of genetic and environmental factors. Ultraviolet (UV) radiation plays a dual role in the development of BCC: it causes DNA damage and immunosuppression. UVA and UVB rays damage the DNA via various mechanisms. UVB radiation directly damages DNA within skin cells, causing cytosine → thymine mutations at dipyrimidine sites, whereas UVA radiation is 10.000 times less mutagenic, but it is significantly more present in the natural UV radiation. Also, UVA photons have lower energy than UVB photons and do not induce mutations. UV radiation exerts immune suppression by decreasing the antigen presenting cells ability and by producing immunosuppressive cytokines, such as interleukin-10 (IL-10) and tumor necrosis factor alpha (TNF-α). Mediators of UV-induced immunosuppression are DNA and cis-urocanic acid. Several studies showed a significant association between the development of BCC and sun-exposure during childhood and adolescence, and a strong relation with family history of skin cancer. Exposure to ionizing radiation increases the risk of nonmelanoma skin cancers by three times, while the risk is proportional to the radiation dose. Chemical carcinogens, such as arsenic, tar, psoralen, and pesticides, increase risks for nonmelanoma skin cancers, predominantly for squamous cell carcinoma (SCC). Regarding genetic predisposition, there is glutathione S-transferase (GST) as an important part of cellular defense against endogenous and exogenous chemicals. Several polymorphisms in GST family members have been associated with impaired detoxification, thus influencing the risk for some cancers, including nonmelanoma skin cancers. Cytochrome P450 enzymes are involved in detoxification of photosensitizing agents, and thus involved in BCC carcinogenesis. PTCH is a tumor suppressor gene first identified in patients with Gorlin syndrome. Abnormal activation of this gene and its pathways result in various types of tumorigenesis. BCC is associated with homozygous PTCH gene deletion. With regard to acquired genetic mutations, it was found that aggressive BCCs are significantly associated with increased p53 protein expression, probably representing the mutated form, although that assertion could not be established with certainty. Considering the apparently limited contribution of DNA damage and chromosome instability to the expression of BCC phenotype, the relevance of p53 mutations for BCC growth remains to be demonstrated. Data on the role of Bcl-2 gene family in the development of BCC are scarce. It is unclear whether Bcl-2 has a functional role in the development of BCC, or it only indicates the level of gene expression in tumor stem cells. Activation of Ras gene may play an important role during early stages in the development of nonmelanoma skin cancers, and it is often found on UV-exposed skin in BCC, actinic keratosis and SCC. Concerning immunologic factors, studies have shown that tumor necrosis factor-α (TNF-α) is the critical mast cell product involved in ultraviolet-induced immunosuppression: mast cells contain high quantities of TNF-α which is released after activation; the level of TNF-α is increased in the skin exposed to UV radiation disrupting the morphology and function of Langerhans cells, the principal antigen-presenting cells of the skin. An animal study suggests that the degree of susceptibility to ultraviolet-B-induced local immunosuppression depends on TNF-α level within the epidermis after UVB. It has been established that mast cell-derived histamine stimulates prostaglandin E2 (PGE2) production from keratinocytes. PGE2 alters the cytokine balance in favor of the immunosuppressive interleukin-10 (IL-10) against the immunostimulatory IL-12; histamine also increases suppressor T-cell function by binding to the H2 receptors, which in turn release higher levels of immune suppressive cytokines including IL-10 and induce apoptosis of antigen-presenting cells. All this results in a shift of the immune response from T helper 1 (Th1) cytokine profile to T helper 2 (Th2) cytokine profile, inhibiting antigen-presenting cells to induce antitumor activity.

Effects of glutathione-S-transferase polymorphisms on the risk of breast cancer: a population-based case-control study in Pakistan

Cancer is widely accepted as one of the major health issues. Diet composition and exposure to environmental genotoxic and carcinogenic agents such as polycyclic aromatic hydrocarbons (PAHs) are among the causative factors for various types of cancers, including breast cancer. Low penetrance genes including glutathione S transferases (GST) in association with environmental factors can contribute greatly in the development of breast cancer. We were interested to investigate the association of the polymorphisms of GSTM1, GSTT1, GSTP1 and GSTO2 with the risk of breast cancer in the Pakistani population. One hundred women visiting the Department of Radiology and Oncology, Nishter Hospital, Multan with pathologically confirmed breast cancer, and 100 healthy volunteers from central Pakistan were enrolled in the present study. The strength of the association of various factors with breast cancer was measured by calculating odd ratios (ORs) which were determined by logistic regression. All P values cited are two-sided; differences resulting in a P value of less or equal to 0.05 were declared statistically significant. The Hardy Weinberg equilibrium was tested for the genotype proportions in the control group, as a measure of quality control. Those aged 36-45, in menopause or with a history of cancer in the family had a significantly higher prevalence of breast cancer compared with controls. The frequency of GSTM1 and GSTT1 was similar in both control and patients suggesting no association with the risk of cancer development, however GSTM1 and GSTT1 were significantly linked with the risk of breast cancer in smokers and in women with a history of breast cancer in the family respectively. Similarly women homozygous for GSTP1 or GSTO2 and with a history of breast cancer, or in menopause, were at greater risk of breast cancer than wild type or heterozygotes. Our data suggest that genetic differences in some GST genes may be linked with an increased susceptibility to breast cancer. Furthermore it also gives an insight into the interaction between the GST polymorphisms and pre-menopausal diagnosis of breast cancer.

Effect of GSTM1-Polymorphism on Disease Progression and Oxidative Stress in HIV Infection: Modulation by HIV/HCV Co-Infection and Alcohol Consumption

Objective

To examine the effects of GSTM1 null-allele polymorphism on oxidative stress and disease progression in HIV infected and HIV/hepatitis C (HCV) co-infected adults.

Methods

HIV-infected and HIV/HCV co-infected participants aged 40–60 years old with CD4 cell count >350 cells/ µl, were recruited. GSTM1 genotype was determined by quantitative PCR. Oxidative stress (mitochondrial 8-oxo-2’-deoxyguanosine [8-oxo-dG], malondialdehyde [MDA], oxidized glutathione and Complexes I and IV), apoptosis and HIV disease (CD4 count and viral load) markers were measured. Gene copies were not quantified, thus the Hardy-Weinberg formula was not applicable.

Results

Of the 129 HIV-infected participants, 58 were HIV/HCV co-infected. GSTM1 occurred in 66% (62/94) in those of African descent, and 33% (11/33) of the Caucasians. Those with GSTM1 coding for the functional antioxidant enzyme Glutathione S-transferase (GST), had higher CD4 cell count (β=3.48, p=0.034), lower HIV viral load (β=−0.536, p=0.018), and lower mitochondrial 8-oxo-dG (β=−0.28, p=0.03). ART reduced oxidative stress in the participants with the GSTM1 coding for the functional antioxidant enzyme. HIV/HCV co-infected participants with the GSTM1 coding for the functional antioxidant enzyme also had lower HIV viral load, lower 8-oxo-dG and lower rate of apoptosis, but also higher oxidized glutathione. Alcohol consumption was associated with lower HIV viral load but higher oxidized glutathione in those with the GSTM1 genotype coding for the functional antioxidant enzyme.

Conclusion

The GSTM1 genotype coding for the functional antioxidant enzyme is associated with lower HIV disease severity, and with lower oxidative stress, compared to GSTM1 null-allele polymorphism. HCV co-infection and alcohol use may be associated with increased oxidative stress even in the presence of the GSTM1 coding for the functional antioxidant enzyme. The null-gene, on the contrary, appears to have a detrimental effect on immune function, viral load control, and antioxidant status, suggesting a potential benefit from antioxidants in HIV infected patients with the defective gene.

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.

Changing pathology with changing drugs: skin cancer

Today skin cancer is mainly treated by surgical interventions. New findings concerning molecular biology and the signaling pathways in epithelial skin cancers such as basal cell carcinoma, squamous cell carcinoma or melanoma, and mesenchymal skin cancers such as angiosarcoma and dermatofibrosarcoma protuberans (DFSP) have identified new molecular targets for a systemic or local treatment approach. For DFSP there is an opportunity already today to reduce the intensity of surgical procedures by pretreatment with targeted therapy. This article highlights important aspects in several skin cancer types.

ASIP genetic variants and the number of non-melanoma skin cancers

Patients with primary non-melanoma skin cancers (NMSCs) tend to develop these cancers at multiple independent sites. We examined the genetic factors in the development of multiple NMSCs among Caucasian women with 28 years of follow-up. We initially evaluated 19 SNPs in nine pigmentation genes with the number of NMSCs in 492 cases and 619 controls without a history of NMSC. We found nominal significant associations between two ASIP gene-related SNPs, rs1885120 and rs910873, and an ASIP haplotype (AH) (rs4911414 allele T and rs1015362 allele G) and an increased number of NMSCs, with p-values of 0.008, 0.01, and 0.01, respectively. We further evaluated these two SNPs and AH haplotype in three data sets. In a joint analysis with 1,507 cases and 4,335 controls, AH haplotype was independently associated with the number of NMSCs with odds ratio (OR) (95% confidence interval (CI)) of 1.45(1.25-1.68) (p-value = 6.2E-07). The AH haplotype was associated with an increased risk of developing one NMSC (OR 1.32; 95% CI, 1.07-1.63). The OR increased to 1.45(1.18-1.78) for those with 2-4 NMSCs and 1.84(1.34-2.53) for those with at least five. The findings suggest that ASIP locus is associated with the number of NMSCs.

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.

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.

Mosquito immune responses and compatibility between Plasmodium parasites and anopheline mosquitoes

BACKGROUND

Functional screens based on dsRNA-mediated gene silencing identified several Anopheles gambiae genes that limit Plasmodium berghei infection. However, some of the genes identified in these screens have no effect on the human malaria parasite Plasmodium falciparum; raising the question of whether different mosquito effector genes mediate anti-parasitic responses to different Plasmodium species.

RESULTS

Four new An. gambiae (G3) genes were identified that, when silenced, have a different effect on P. berghei (Anka 2.34) and P. falciparum (3D7) infections. Orthologs of these genes, as well as LRIM1 and CTL4, were also silenced in An. stephensi (Nijmegen Sda500) females infected with P. yoelii (17XNL). For five of the six genes tested, silencing had the same effect on infection in the P. falciparum-An. gambiae and P. yoelii-An. stephensi parasite-vector combinations. Although silencing LRIM1 or CTL4 has no effect in An. stephensi females infected with P. yoelii, when An. gambiae is infected with the same parasite, silencing these genes has a dramatic effect. In An. gambiae (G3), TEP1, LRIM1 or LRIM2 silencing reverts lysis and melanization of P. yoelii, while CTL4 silencing enhances melanization.

CONCLUSION

There is a broad spectrum of compatibility, the extent to which the mosquito immune system limits infection, between different Plasmodium strains and particular mosquito strains that is mediated by TEP1/LRIM1 activation. The interactions between highly compatible animal models of malaria, such as P. yoelii (17XNL)-An. stephensi (Nijmegen Sda500), is more similar to that of P. falciparum (3D7)-An. gambiae (G3).

Hepatoprotective effects of Solanum nigrum Linn extract against CCl(4)-induced oxidative damage in rats

Solanum nigrum L. (SN) is an herbal plant that has been used as hepatoprotective and anti-inflammation agent in Chinese medicine. In this study, the protective effects of water extract of SN (SNE) against liver damage were evaluated in carbon tetrachloride (CCl4)-induced chronic hepatotoxicity in rats. Sprague-Dawley (SD) rats were orally fed with SNE (0.2, 0.5, and 1.0 g kg(-1) bw) along with administration of CCl4 (20% CCl4/corn oil; 0.5 mL kg(-1) bw) for 6 weeks. The results showed that the treatment of SNE significantly lowered the CCl4-induced serum levels of hepatic enzyme markers (GOT, GPT, ALP, and total bilirubin), superoxide and hydroxyl radical. The hepatic content of GSH, and activities and expressions of SOD, GST Al, and GST Mu that were reduced by CCl4 were brought back to control levels by the supplement of SNE. Liver histopathology showed that SNE reduced the incidence of liver lesions including hepatic cells cloudy swelling, lymphocytes infiltration, hepatic necrosis, and fibrous connective tissue proliferation induced by CCl4 in rats. Therefore, the results of this study suggest that SNE could protect liver against the CCl4-induced oxidative damage in rats, and this hepatoprotective effect might be contributed to its modulation on detoxification enzymes and its antioxidant and free radical scavenger effects.

Genetic factors associated with skin cancer in renal transplant patients

BACKGROUND

Non-melanoma skin cancer represents a significant cause of morbidity and mortality among renal transplant recipients. Established risk factors that increase susceptibility to skin cancer after transplantation include skin type, sun exposure and level of immunosuppression.

METHODS

A comprehensive literature review was carried out to discuss relevant genetic polymorphism for the development of skin cancer in organ transplant recipients. These include genetic polymorphisms in glutathione S-transferase, interleukin-10, retinoblastoma and p53 genes. We also discuss genetic polymorphisms in the folate pathway, melanocortin 1 receptor and vitamin D receptor recently discovered in our group.

RESULTS

No single factor is causative in cutaneous carcinogenesis in transplant recipients. Interactions of some of the above mechanisms with known environmental factors lead to increased risk.

CONCLUSION

Polymorphisms in methylenetetrahydrofolate reductase are potentially correctable with folic acid supplementation; however, further evaluation is required in adequately powered prospective clinical trials. Avoidance of known oncogenic environmental factors and genetic risk evaluation may improve outcomes in transplant patients.

Genetics of endometriosis: heritability and candidate genes

Endometriosis is a complex gynecologic disorder that affects as many as 10-15% of premenopausal women. Epidemiologic studies have confirmed that this disease is a genetic disorder of polygenic/multifactorial inheritance. The disorder has long been recognized to show heritable tendencies with recurrence risks of 5-7% for first-degree relatives. The current investigational goal is to determine the number and location of causative genes, a process that has been made possible by recent advances in molecular technology. This chapter discusses heritability studies supporting polygenic/multifactorial inheritance, the scientific basis of genome-wide strategies for identifying causative genes and potential candidate genes.

Case-control study in basal cell carcinoma of the skin: single nucleotide polymorphisms in three interleukin promoters pre-analysed in pooled DNA

BACKGROUND

Basal cell carcinoma (BCC) is one of the most common neoplasms in the world. Development of BCC is associated with environmental factors (especially sun exposure) as well as heritable factors.

OBJECTIVES

To analyse three single nucleotide polymorphisms (SNPs) in the promoter regions of interleukin (IL) genes in genomic DNA from 527 cases of BCC and 530 matched controls and to examine if DNA pooling is a useful method on which to base decisions regarding further SNP analysis.

METHODS

The SNPs analysed were IL6-597, IL10-1082 and IL1B-511. The SNPs were first analysed from pooled DNA and afterwards from individual samples. The DNA pools resulted from a division of the samples into cases and controls, female and male, and three age groups. In these pools the allele frequencies were estimated by two methods, real-time polymerase chain reaction with allele-specific primers, and quantitative sequencing.

RESULTS

No significant association was found when the allele frequencies in cases and controls were compared. However, by analysis of the individual genotypes we found SNP IL6-597 G/A to be significantly associated with BCC risk (P =0.007). Hereby the heterozygous genotype 'GA' had a protective effect (odds ratio 0.64, 95% confidence interval 0.49-0.84). No significant association was found for IL10-1082 and IL1B-511.

CONCLUSIONS

The association of SNP IL6-597 with BCC could be found only by individual genotyping, but would have been missed if only data from the pooling analysis had been known.

MC1R and PTCH Gene Polymorphism in French Patients with Basal Cell Carcinomas

In this study, we assessed the role of melanocortin 1 receptor (MC1R) variants and of two patched (PTCH) polymorphisms (c.3944C>T (P1315L), insertion 18 bp IVS1-83) as risk factors for basal cell carcinoma (BCC) in the French population. The population investigated comprised 126 BCC patients who were enrolled on the basis of specific criteria (multiple and/or familial BCC and/or onset before the age of 40 years and/or association with another tumor)--and 151 controls matched for ethnicity, age, and sex. MC1R variants appeared as a moderate risk factor for BCC (odds ratio (OR) for one and two variants, 2.17 [1.28-3.68] and 7.72 [3.42-17.38], respectively), independently of pigmentation characteristics (OR = 2.53 [1.34-4.8]). Interestingly, in addition to the predictable red hair color (RHC) alleles, two non-RHC alleles (V60L and V92M) were also closely associated with BCC risk (OR 3.21 [1.91-5.38] and 2.87 [1.5-5.48], respectively), which differs from the situation in the Celtic population. In addition, the PTCH c.3944C/C genotype was also associated with BCC risk (OR 1.94 [1.2-3.1]), especially in the subgroup of patients with multiple tumors (OR 2.16 [1.3-3.6]). Thus, our data show that MC1R and PTCH variants are associated with BCC risk in the French population. We further suggest that assessing MC1R and PTCH status could be useful, combined with the assessment of clinical risk factors, in identifying high-risk patients to be targeted for prevention or more rigorous surveillance.

Influence of glutathione-S-transferase (GSTM1, GSTP1, GSTT1) and cytochrome p450 (CYP1A1, CYP2D6) polymorphisms on numbers of basal cell carcinomas (BCCs) in families with the naevoid basal cell carcinoma syndrome

BACKGROUND

The naevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant multisystem disorder with variable expression. NBCCS patients have variable susceptibility to development of basal cell carcinoma (BCC). Previous studies have shown that polymorphisms of some metabolic genes encoding the cytochrome p450 (CYP) and glutathione-S-transferase (GST) enzymes influenced the numbers of BCCs in sporadic BCC cases.

OBJECTIVE

To determine whether allelic variants of these genes contribute to the variation in numbers of BCCs observed in NBCCS families.

METHODS

Genotyping and analysis was carried out in 152 members (69 affected and 83 unaffected) of 13 families with NBCCS for seven polymorphisms in five metabolic genes including CYP1A1, CYP2D6, GSTM1, GSTP1, and GSTT1.

RESULTS

GSTP1 Val105 and GSTP1 Val114 alleles were significantly associated with fewer BCC numbers (odds ratio (OR)105 = 0.55 (95% confidence interval, 0.35 to 0.88); OR114 = 0.20 (0.05 to 0.88)). The Val(105) allele showed a dose dependent effect (OR(Ile/Val) = 0.58 (0.34 to 0.88); OR(Val/Val) = 0.34 (0.14 to 0.78)). In addition, fewer jaw cysts were observed in carriers of the three p450 polymorphisms (CYP1A1m1, CYP1A1m2, and CYP2D6*4) (OR(CYP1A1m1) = 0.27 (0.12 to 0.58); OR(CYP1A1m2) = 0.25 (0.08 to 0.78); OR(CYP2D6*4) = 0.33 (0.18 to 0.60)).

CONCLUSIONS

Genetic variants might contribute to the variation in numbers of BCCs and jaw cysts observed in NBCCS families.

Protection effect of piper betel leaf extract against carbon tetrachloride-induced liver fibrosis in rats

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of detoxication, antioxidation, and antimutation. In this study, we evaluated the antihepatotoxic effect of PBL extract on the carbon tetrachloride (CCl(4))-induced liver injury in a rat model. Fibrosis and hepatic damage, as reveled by histology and the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were induced in rats by an administration of CCl(4) (8%, 1 ml/kg body weight) thrice a week for 4 weeks. PBL extract significantly inhibited the elevated AST and ALT activities caused by CCl(4) intoxication. It also attenuated total glutathione S-transferase (GST) activity and GST alpha isoform activity, and on the other hand, enhanced superoxide dismutase (SOD) and catalase (CAT) activities. The histological examination showed the PBL extract protected liver from the damage induced by CCl(4) by decreasing alpha-smooth muscle actin (alpha-sma) expression, inducing active matrix metalloproteinase-2 (MMP2) expression though Ras/Erk pathway, and inhibiting TIMP2 level that consequently attenuated the fibrosis of liver. The data of this study support a chemopreventive potential of PBL against liver fibrosis.

Genetics and risk factors for basal cell carcinoma

Nonmelanoma skin cancer (NMSC) is the commonest cancer in whites and its incidence is increasing worldwide. The prevalence of this cancer is predicted to equal that of all others combined and it was estimated that there were over 2 million cases diagnosed in the U.S.A. in 2004. Patients exhibit marked differences in clinical phenotype with variations in tumour numbers, rate of tumour accrual, site and histological subtype. Furthermore, patients are at increased risk of other cutaneous and noncutaneous cancers. The factors accounting for this variation are complex and still not completely understood. Clearly, ultraviolet light (UV) exposure is a major influence but its relationship to clinical phenotype is not yet clear. In addition, immunosuppression is a significant risk factor. Our group has identified high-risk groups for the development of further basal cell carcinoma (BCC), namely patients with truncal BCC and those presenting with tumour clusters. This presentation will concentrate on these clinical subgroups as well as immunosuppressed patients. These groups represent significant management challenges and are areas where novel, nonsurgical treatment options may make a significant clinical impact in patient care. The risk factors predisposing to these clinical phenotypes will be discussed, including genetic factors and UV exposure. Potential clinical applications, including predictive indices, will be considered.

The small-molecule immune response modifier imiquimod – its mode of action and clinical use in the treatment of skin cancer

Due to its good clinical efficacy against malignant skin tumours, the topical immune response modifier, imiquimod, has attracted much interest among researchers and clinicians alike. Imiquimod exerts its antitumoural effect, at least in part, through agonistic stimulation of TLR-7 and TLR-8 on dendritic cells, followed by NF-kappaB-dependent secretion of a multitude of pro-inflammatory cytokines. The net result of this pro-inflammatory activity is a profound tumour-directed cellular immune response. Recent research has revealed an additional mode of action inasmuch as imiquimod interferes with adenosine receptor signalling, even in TLR-7- and TLR-8-negative cells, thereby presumably augmenting inflammatory signalling cascades. Moreover, at higher concentrations imiquimod also exerts direct proapoptotic activity against tumour cells. This mode of action appears to be independent of membrane-bound death receptors but is mediated, at least in part, through Bcl-2-dependent release of mitochondrial cytochrome c and subsequent caspase activation. Overall, a combination of several complementary antitumoural modes of action appears to underlie the great utility of imiquimod for treating cutaneous tumours.

Increased sensitivity of Hep G2 cells toward the cytotoxicity of cisplatin by the treatment of piper betel leaf extract

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of de-toxication, anti-oxidation and anti-mutation. In this study we first examined the effect of PBL extract on the activity of Glutathione S-transferase (GST) isoforms, and found that it inhibited total GST and the alpha class of GST (GSTA), but not the pi class of GST (GSTP), and the mu class of GST (GSTM), activity in Hep G2 cells. RT-PCR results verified a reduction in the expression of GSTA1. Next, we examined whether PBL extract could increase the sensitivity of Hep G2 cells to anti-cancer drugs. The data showed that the cytotoxicity of cisplatin was significantly enhanced by the presence of PBL extract, accompanied by a reduction in the expression of multidrug resistance protein 2 (MRP2). These effects of PBL extract were compared to its major constitute, eugenol. Although eugenol decreased MRP2 level more effectively than PBL extract, it exhibited less sensitizing effect. In conclusion, we demonstrated that PBL extract was able to increase the sensitivity of Hep G2 cells to cisplatin via at least two mechanisms, reducing the expression of MRP2 and inhibiting the activity of total GST and the expression of GSTA. The data of this study support an application of PBL as an additive to reduce drug resistance.

GSTM1, GSTT1 and GSTP1 polymorphisms in the Korean population

The isoenzymes of the glutathione s transferase (GST) family play a vital role in phase II of biotransformation of many substances. Using a multiplex polymerase chain reaction and a direct sequencing analysis, the frequencies of GSTM1, GSTT1, and GSTP1 polymorphisms were evaluated in 1,051 Korean male subjects. We found that 53.8% of the individuals had the GSTM1 null genotype and 54.3% had the GSTT 1 null genotype. The genotypic distribution of GSTP1 was Ile105/Ile105 in 68.4%, Ile105/Val105 in 29.1% and Val105/Va105 in 2.5%. The most frequently observed combination of GSTM1, GSTP1 and GSTT1 genotypes was Null type/Ile105/Ile105/Null type, while the combination of Non-null type/Val105/Val105/Non-Null type was not observed. We found that the genotype distributions of three GST isoenzymes in the Koreans are similar to those reported in Asians and previously reported Koreans. We believe our results, which are represented by a large population, are reliable estimates of the frequencies of the polymorphic GST alleles in the Koreans and will help future researches on GST polymorphisms.

Geniposide activates GSH S-transferase by the induction of GST M1 and GST M2 subunits involving the transcription and phosphorylation of MEK-1 signaling in rat hepatocytes

Geniposide, an iridoid glycoside isolated from the fruit of Gardenia jasminoides Ellis, has biological capabilities of detoxication, antioxidation, and anticarcinogenesis. We have recently found that geniposide possesses a potential for detoxication by inducing GST activity and the expression of GST M1 and GST M2 subunits. In this study, the signaling pathway of geniposide leading to the activation of GSH S-transferase (GST) was investigated. Primary cultured rat hepatocytes were treated with geniposide in the presence or absence of mitogen-activated protein kinase (MAPK) inhibitors and examined for GST activity, expression of GST M1 and M2 subunits, and protein levels of MAPK signaling proteins. Western blotting data demonstrated that geniposide induced increased protein levels of GST M1 and GST M2 (approximately 1.76- and 1.50-fold of control, respectively). The effect of geniposide on the increased protein levels of GST M1 and GST M2 was inhibited by the MEK-1 inhibitor PD98059, but not by other MAPK inhibitors. The GST M1 and GST M2 transcripts as determined by RT-PCR and GST activity were also inhibited concurrently by the MEK-1 inhibitor PD98059. The protein levels of up- and down-stream effectors of the MEK-1, including Ras, Raf, and Erk1/2, and the phosphorylation state of Erk1/2 were found to be induced by geniposide, indicating a two-phase influence of geniposide. The results suggest that geniposide induced GST activity and the expression of GST M1 and GST M2 acting through MEK-1 pathway by activating and increasing expression of Ras/Raf/MEK-1 signaling mediators.

GSTM1, GSTT1 and CYP1A1 detoxification gene polymorphisms and their relationship with advanced stages of endometriosis in South Indian women

OBJECTIVE(S)

Studies on association between endometriosis and various phase I and phase II detoxification genes such as glutathione S-transferase M1 and theta 1 (GSTM1 and GSTT1) and cytochrome P450 (CYP1A1) have produced inconsistent results possibly because of ethnic differences. The present study was undertaken to investigate the frequency of the CYP1A1 (6235T>C) polymorphism and GSTM1, GSTT1 null mutations in a South Indian women's population with and without endometriosis.

METHODS

The frequencies of variants were studied in 310 women with laparoscopically proven endometriosis (rAFS III=101; IV=209) and 215 women without endometriosis using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

The GSTM1 null deletion showed significant association (P=0.028) with endometriosis. No significant difference was found in the frequencies of the GSTT1 null deletion in cases and controls. The frequencies of the variant CYP1A1 homozygous and heterozygous alleles in the cases were 9% and 44.2% against 14.4% and 42.3% in the controls. Further, we observed a considerable difference in the GSTM1 null deletion frequency in this population when compared with other populations of the world.

CONCLUSIONS

We observed an association between endometriosis and the GSTM1 null deletion, but not with GSTT1 null deletions or the CYP1A1 MspI polymorphism in South Indian women.

Molecular aetiology and pathogenesis of basal cell carcinoma

Recent insights into the cell biology of the epidermis and its appendages are transforming our understanding of the pathogenesis of basal cell carcinoma (BCC). The significant progress that has been made warrants a comprehensive review of the molecular and cellular pathology of BCC. The items addressed include environmental and genetic risk factors, the biology of the putative precursor cell(s), and the contribution of aberrations in processes such as apoptosis, cell proliferation, differentiation and signalling to carcinogenesis. Furthermore, established and novel treatment modalities are discussed with particular attention to future biological approaches.

Basal cell carcinoma: from host response and polymorphic variants to tumour suppressor genes

The molecular factors and events that characterize susceptibility and outcome in cutaneous basal cell carcinoma (BCC) have been the focus of much research interest. As a result, we are beginning to understand the complex relationships between exposure to ultraviolet radiation (UVR), host response and the resulting damage to key genes that characterize these tumours. In this review, we will focus on genetic factors that influence susceptibility and outcome. While the search for susceptibility genes has generally resulted in the identification of low penetrance allelic variants, studies on modifier genes influencing outcome variables such as tumour number, age of onset and tumour subtype have identified factors with higher potential impact. Here we will briefly describe some recent work on the genetic basis of the immune response to UVR, the effect of UVR on the generation of reactive oxygen species and their detoxification, and the role of onco- and tumour suppressor genes. Areas for further research are highlighted, together with a consideration of possible applications in clinical practice.

Genetic Basis of Endometriosis

Endometriosis is a complex gynecologic disorder that has long been recognized as showing heritable tendencies, with recurrence risks of 5-7% for first-degree relatives. Familial and epidemiologic studies support that this disease is a genetic disorder of polygenic/multifactorial inheritance. The current investigational challenge is to determine the number and location of causative genes. Recent advances in molecular technology make identification and elucidation of these genes now possible. In this review, we update previous communications in which we also reviewed heritability studies supporting polygenic/multifactorial inheritance, discuss the scientific basis of genomewide strategies for identifying causative genes, and identify potential candidate genes.

Molecular interactions of B-CAM (basal-cell adhesion molecule) and laminin in epithelial skin cancer

Molecular events underlying the progression of malignant tumors through the surrounding tissue are largely mediated by membrane-bound adhesion molecules. Basal-cell adhesion molecule (B-CAM), a 90-kDa laminin receptor of the immunoglobulin superfamily, is induced in some epithelial malignancies. Its function in these tumors, however, still remains obscure. We demonstrated that expression of B-CAM is very weak, if detectable at all, in normal epidermis but is strongly induced in both basal cell carcinomas and squamous cell carcinomas of the skin, and most pronounced at the basal surface of the tumor nests. Interestingly, the only known B-CAM ligand, laminin, was markedly upregulated within corresponding microanatomical sites surrounding the tumor nests, suggesting that both molecules may interact there. Consistent with this hypothesis, we were able to directly demonstrate binding of a B-CAM/Fc chimeric molecule to the peritumoral stroma in situ. Finally, in proof-of-principle experiments, human B-CAM was overexpressed both in murine and in human fibroblasts. The haptotactic migration of these novel B-CAM+ cell populations on a laminin matrix was significantly increased (P = 0.02) as compared to mock-transfected cells when integrin-mediated adhesion was blocked by chelation of divalent cations. Thus, our findings provide the first direct experimental evidence that interactions of B-CAM and laminin may be involved in progression of epithelial skin tumors.

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.

Tumor-selective induction of apoptosis and the small-molecule immune response modifier imiquimod

BACKGROUND

The incidence of nonmelanoma skin cancer, basal cell carcinomas (BCCs), and squamous cell carcinomas (SCCs) is increasing, representing a major medical and economic problem. Imiquimod, a topical small-molecule immune response modifier, has shown efficacy toward BCC and actinic keratoses in clinical trials. Imiquimod acts both indirectly, via cytokine-mediated stimulation of cellular immune responses, and directly, through unknown mechanisms against tumor cells. We examined the mechanism by which imiquimod induces apoptosis in cancer cells.

METHODS

Apoptosis was assessed by enzyme-linked immunosorbent assay, western blot analysis, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays in five SCC cell lines, HaCaT cells (a spontaneously immortalized human keratinocyte cell line), and normal keratinocytes treated with imiquimod, with its analog resiquimod, or with neither. Expression of death receptors, caspases, and cytochrome c in the apoptotic signaling cascade was analyzed using western blot and flow cytometric analyses. The functional relevance of imiquimod-induced cytochrome c release was assessed by transfection of HaCaT cells with Bcl-2. Apoptosis in BCCs in vivo was assessed by TUNEL assays of imiquimod-treated and untreated tumors from three patients. Differences between treated and untreated cells and tumors were determined using a two-tailed Student's t test.

RESULTS

Imiquimod, but not resiquimod, induced apoptosis in all SCC cell lines and HaCaT cells. This induction involved activation of several caspases and Bcl-2-dependent cytosolic translocation of cytochrome c but was independent of the membrane-bound death receptors Fas, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-R1-R4 receptors, and tumor necrosis factor-R1 and -R2 receptors. Topical application of imiquimod to BCC tumors in vivo induced apoptosis.

CONCLUSION

Imiquimod has the potential to induce apoptosis in skin cancer cells, possibly by circumventing mechanisms developed by malignant tumors to resist apoptotic signals.

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.

Genetics of endometriosis

Endometriosis long has been recognized as showing heritable tendencies, with recurrence risks of 5% to 7% for first-degree relatives. The risk indicates that polygenic and multifactorial etiology is far more likely to be the cause than mendelian inheritance. The current task is to determine the number and location of genes responsible for endometriosis. Molecular advances of the past decade make identification and elucidation of these genes a reality. The authors review the basis for concluding that endometriosis is a genetic disorder of polygenic/multifactorial inheritance. Genome-wide strategies for identifying causative genes are considered and available data on association or linkage to putative candidate genes systematically reviewed.

Heritability and candidate genes for endometriosis

Endometriosis is inherited in polygenic/multifactorial fashion, with recurrence risks of 5-7% for first-degree relatives. The current task is to determine the number and location of causative genes. This review initially supports the basis for polygenic/multifactorial inheritance and then outlines genome-wide strategies for identifying causative genes. Potential candidate genes are surveyed, and discrepant results emphasized. Finally, a hypothesis for endometriosis, having a multi-step pathogenesis analogous to the pathogenesis of neoplasia, is considered.

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.

GSTT1-null genotype is a protective factor against bladder cancer

OBJECTIVES

To investigate the effects of homozygous deletions of GSTM1 and GSTT1 and smoking on bladder cancer, we conducted a case-control and ecological study.

METHODS

The case group consisted of 216 patients with bladder cancer and the control group of 449 healthy Koreans. Every subject was personally interviewed to obtain a detailed smoking history, and a multiplex polymerase chain reaction method was used to detect the presence or absence of the GSTM1 and GSTT1 genes. In the ecological study, age-standardized bladder cancer incidence and frequencies of GSTM1 and GSTT1-null types, estimated prevalence of cigarette smoking, and estimated per capita consumption of cigarettes per adult according to nationality and ethnicity were included.

RESULTS

In the Korean case-control data, smoking history and the GSTT1-null genotype were significantly associated with bladder cancer, and the GSTM1-null genotype was not. In the univariate and multivariate analyses with the ecological data of various countries and ethnic groups, cigarette smoking positively, but the frequency of the GSTT1-null type negatively, correlated with the age-standardized bladder cancer incidence.

CONCLUSIONS

These results suggest that the GSTT1-negative genotype might not be a risk factor but a protective factor of bladder cancer.

Environment, phenotype and genetics: risk factors associated with BCC of the skin

Basal cell carcinoma is the most common cancer in Caucasians and its incidence is rising. Whilst not life threatening, the tumor can cause substantial morbidity and because of long follow-up, it places a major burden on healthcare agencies worldwide. Patients with the disease demonstrate wide phenotypic diversity with respect to tumor numbers, rate of tumor appearance and site. The factors involved in patient susceptibility to basal cell carcinoma are not well understood although exposure to ultraviolet radiation in sunlight appears critical. In this review we discuss the role of environmental and genetic factors on predisposition to basal cell carcinoma and illustrate how stratification of the basal cell carcinoma cohort into high-risk subgroups is helpful in identifying factors significant in disease susceptibility.

Parameters related to oxygen free radicals in human skin: a study comparing healthy epidermis and skin cancer tissue

In vitro studies with tumor cells have demonstrated that oxygen free radicals are involved in the development of skin cancers and that variations in the body's defense mechanisms can modify the course of the disease. To assess the validity of this hypothesis in spontaneous tumors, we determined glutathione S-transferase, superoxide dismutase, reduced and oxidized glutathione, and thiobarbituric acid reactive substances in healthy whole skin (n = 95), dermis (n = 73), and epidermis (n = 69). The values were compared with those obtained in three types of skin cancer: basal cell carcinoma (n = 16), squamous cell carcinoma (n = 6), and melanoma (n = 33). In healthy skin, glutathione S-transferase, superoxide dismutase, reduced glutathione, and oxidized glutathione were higher in epidermis than in dermis, whereas thiobarbituric acid reactive substances were higher in dermis than in epidermis; whole skin had intermediate values. These results suggest that there is an induction of some anti-oxygen free radicals mechanisms in epidermis as a result of increased oxygen free radicals production. Glutathione S-transferase and thiobarbituric acid reactive substances were higher in all types of tumor than in healthy epidermis but oxidized glutathione was lower. Reduced glutathione and superoxide dismutase activity were lower in basal cell carcinoma and squamous cell carcinoma samples. Glutathione S-transferase increased, whereas superoxide dismutase and thiobarbituric acid reactive substances decreased in melanoma samples in direct relation to the Clark levels. Higher glutathione S-transferase activity, particularly in the most invasive forms of melanoma, indicates that this type of cancer is more malignant. Similarly, a decrease in superoxide dismutase activity can also encourage progression of the tumor. These results are in accord with those from tumor cell cultures and could suggest new strategies (gene therapy) for managing skin cancer.

Susceptibility and modifier genes in cutaneous basal cell carcinomas and their associations with clinical phenotype

While ultraviolet radiation (UV) is critical in the pathogenesis of basal cell carcinomas (BCC), its role in determining the phenotypic variation shown by patients is unknown. Thus, patients manifest variation in BCC numbers, patterns of presentation and tumour site. We have used this diversity to classify patients into subgroups that are associated with different risks of developing tumours. Two phenotypes are particularly interesting. Firstly, presentation with clusters of BCC. These patients, termed multiple presentation phenotype (MPP), had two to five BCC at one presentation, suggesting rapid accrual over short periods of time. They comprised 15% of our 1200 BCC patients. A minority of patients demonstrated multiple clustering events, a phenomenon that is associated with a genetic pre-disposition. The second risk phenotype, characterised by tumours on the trunk, is also associated with a pre-disposition. Both phenotypes were characterised by a susceptibility to develop numerous BCC. Thus, all our patients with more than five BCC had one or both of these phenotypes. We are using a candidate gene approach to identify loci associated with risk of these phenotypes (susceptibility genes) and tumour numbers in them (modifier genes). Interestingly, we did not identify differences in UV exposure between patients with high- and low-risk phenotypes.

Glutathione-S-transferase family of enzymes

The loci encoding the glutathione-S-transferase (GST) enzymes comprise a large supergene family located on at least seven chromosomes. The function of the GST enzymes has traditionally been considered to be the detoxication of electrophiles by glutathione conjugation. A wide variety of endogenous (e.g. by-products of reactive oxygen species activity) and exogenous (e.g. polycyclic aromatic hydrocarbons) electrophilic substrates have been identified. Interestingly, recent data has suggested a role, at least for the pi class gene product, in jun kinase inhibition. Since many GST genes are polymorphic, there has been considerable interest in determining whether particular allelic variants are associated with altered risk (or outcome) of a variety of diseases. We describe recent studies in patients with asthma and cutaneous basal cell carcinoma that demonstrate associations between GSTP1 and GSTT1 genotypes and disease phenotypes. Thus, GSTP1val(105)/val(105) was protective against asthma symptoms and GSTT1 null was associated with a subgroup of basal cell carcinoma patients who develop large numbers of primary tumours in clusters. Importantly, these associations were characterised by relatively large odds ratios (0.11 and 7.4, respectively) implying that the allelic variants exert a substantial biological effect. These and other data indicate the importance of GST polymorphism in determining disease phenotype.