The Effect of ACTN3 and VDR Polymorphisms on Skeletal Muscle Performance in Axial Spondyloarthropathies.

BACKGROUND: Spondyloarthritis (SpA) are the most common group of chronic inflammatory rheumatic diseases affecting about 1.5% of the adult Caucasian population. Low back pain is the most common symptom. The aetiopathogenesis of SpA is multifactorial, with well-known genetic and environmental contributions. Furthermore, muscle properties might also be involved in the pathophysiological process and these could be modulated by the genetic background. Alpha-actinin-3 (ACTN3) and Vitamin D receptor (VDR) genes are well-known genes related with muscle performance. Our aim was to analyze four SNPs of these genes and to evaluate their influence in axial SpA (axSpA) susceptibility, phenotype and muscle properties. METHODS: We performed a pilot study based on case-control approach involving 56 participants: 28 axSpA patients and 28 healthy controls matched by age, gender and levels of physical activity. Clinical, epidemiological and muscle characterization data-muscle physical properties (stiffness, tone, and elasticity), strength, mass, and performance, were collected. Two different muscles were considered for analysis, the Multifidus and Gastrocnemius. Four SNPs of ACTN3 (rs1815739) and VDR (rs2228570, rs731236, and rs7975232), were selected, analyzed and correlated with clinical, epidemiological and muscle characterization data. RESULTS: In total, 51 individuals (27 axSpA patients and 24 matched controls) were eligible for further genetic analysis, 66.7% being male and with a mean age of 36 years. Muscle physical properties, muscle strength and muscle mass were similar in both groups; however, axSpA patients showed a decrease in muscle performance. None of the studied SNPs were associated with disease susceptibility/phenotype, muscle physical properties, muscle strength or muscle mass. However, ACTN3 rs1815739 and VDR rs2228570 were shown to be associated with muscle performance. CONCLUSION: Our results suggest an association between ACTN3 and VDR polymorphisms and muscle performance in axSpA.

Thyroid Cancer: The Quest for Genetic Susceptibility Involving DNA Repair Genes.

The incidence of thyroid cancer (TC), particularly well-differentiated forms (DTC), has been rising and remains the highest among endocrine malignancies. Although ionizing radiation (IR) is well established on DTC aetiology, other environmental and genetic factors may also be involved. DNA repair single nucleotide polymorphisms (SNPs) could be among the former, helping in explaining the high incidence. To further clarify the role of DNA repair SNPs in DTC susceptibility, we analyzed 36 SNPs in 27 DNA repair genes in a population of 106 DTCs and corresponding controls with the aim of interpreting joint data from previously studied isolated SNPs in DNA repair genes. Significant associations with DTC susceptibility were observed for XRCC3 rs861539, XPC rs2228001, CCNH rs2230641, MSH6 rs1042821 and ERCC5 rs2227869 and for a haplotype block on chromosome 5q. From 595 SNP-SNP combinations tested and 114 showing relevance, 15 significant SNP combinations (p < 0.01) were detected on paired SNP analysis, most of which involving CCNH rs2230641 and mismatch repair variants. Overall, a gene-dosage effect between the number of risk genotypes and DTC predisposition was observed. In spite of the volume of data presented, new studies are sought to provide an interpretability of the role of SNPs in DNA repair genes and their combinations in DTC susceptibility.

The Role of Caspase Genes Polymorphisms in Genetic Susceptibility to Philadelphia-Negative Myeloproliferative Neoplasms in a Portuguese Population.

Our main aim was to evaluate the role of caspases' genes SNPs in Philadelphia-chromosome negative chronic myeloproliferative neoplasms (PN-MPNs) susceptibility. A case-control study in 133 Caucasian Portuguese PN-MPNs patients and 281 matched controls was carried out, studying SNPs in apoptosis related caspases: rs1045485 and rs1035142 (CASP8), rs1052576, rs2308950, rs1132312 and rs1052571 (CASP9), rs2227309 and rs2227310 (CASP7) and rs13006529 (CASP10). After stratification by pathology diagnosis for essential thrombocythemia (ET), female gender or JAK2 positive, there is a significant increased risk for those carrying at least one variant allele for CASP9 (C653T) polymorphism (OR 2.300 CI 95% [1.180-4.484], P = 0.014). However, when considered individually, none of the studied caspases polymorphisms was associated with PN-MPNs risk. Our results do not reveal a significant involvement of caspase genes polymorphisms on the individual susceptibility towards PN-MPNs as a whole. However, for essential thrombocythemia (ET), female gender or JAK2 positive, there is a significant increased risk to those carrying at least one variant allele for CASP9. Although larger studies are required to confirm these results and to provide conclusive evidence of association between these and other caspases variants and PN-MPNs susceptibility, these new data may contribute to a best knowledge of the pathophysiology of these disorders and, in the future, to a more rational and efficient choice of therapeutic strategies to be adopted in PN-MPNs treatment.

Effects of polymorphic DNA genes involved in BER and caspase pathways on the clinical outcome of myeloproliferative neoplasms under treatment with hydroxyurea.

Several single nucleotide polymorphisms (SNPs) influencing DNA repair capacity and apoptotic status may confer genetic predisposition to Philadelphia­chromosome negative myeloproliferative neoplasms (PN­MPNs), and influence therapeutic response and the clinical course. In the present study, whether SNPs in genes involved in apoptosis and the base excision repair (BER) pathway was evaluated. In addition, some known risk factors in PN­MPNs that may influence survival and therapeutic response to hydroxyurea (HU) were analyzed, taking into account three items: Disease progression, predisposition to new non­myeloid neoplasms and thrombotic events. The present study involved a total of 133 Caucasian Portuguese PN­MPNs patients treated with HU, whereby 17 cases showed progression to myelofibrosis/leukemia, 11 developed new non­myeloid neoplasms and 22 presented with thrombotic events. Progression to secondary myelofibrosis/leukemia is influenced by exposure to cytoreductive agents, and caspase and BER polymorphisms {globally, CASP8 3'untranslated region [odds ratio (OR)=0.24; 95% confidence interval (CI), 0.08­0.69], XRCC1 Arg194Trp [OR=3.58; 95% CI, 0.98­13.01]; for essential thrombocythemia patients CASP9 Arg173His [OR=11.27; 95% CI, 1.13­112.28], APEX1 Asp148Glu [OR=0.28; 95% CI, 0.74­1.03], and XRCC1 Arg194Trp [OR=6.60; 95% CI, 1.60­27.06]}. Moreover, globally caspase and BER polymorphisms influenced the development of new nonmyeloid malignancies [CASP8 Asp270His (OR=5.90; 95% CI, 1.42­24.62) and XRCC1 Arg399Gln (OR=0.27; 95% CI, 0.07­1.03)]. On the other hand, only the BER pathway had a role in the presence of thrombotic events [XRCC1 Gln399Arg (OR=0.35; 95% CI, 0.14­0.88)]. JAK2 mutation had no influence on these complications. Larger studies are required to confirm these results, and to provide conclusive evidence of association between these and other variants with PN­MPNs therapeutic response and clinical evolution. However, this study may allow the development of drugs more directly targeted to the pathophysiology of the disease, with high efficacy, fewer adverse effects, contributing to compliance of patients with treatments. The clinical indication for classical drugs, including HU, may be guided by variant genes, which may provide additional beneficial effects.

Mismatch repair single nucleotide polymorphisms and thyroid cancer susceptibility.

Thyroid cancer (TC) is the most common endocrine malignancy and its incidence continues to rise worldwide. Ionizing radiation exposure is the best established etiological factor. Heritability is high; however, despite valuable contribution from recent genome-wide association studies, the current understanding of genetic susceptibility to TC remains limited. Several studies suggest that altered function or expression of the DNA mismatch repair (MMR) system may contribute to TC pathogenesis. Therefore, the present study aimed to evaluate the potential role of a panel of MMR single nucleotide polymorphisms (SNPs) on the individual susceptibility to well-differentiated TC (DTC). A case-control study was performed involving 106 DTC patients and 212 age- and gender-matched controls, who were all Caucasian Portuguese. Six SNPs present in distinct MMR genes (MLH1 rs1799977, MSH3 rs26279, MSH4 rs5745325, PMS1 rs5742933, MLH3 rs175080 and MSH6 rs1042821) were genotyped through TaqMan® assays and genotype-associated risk estimates were calculated. An increased risk was observed in MSH6 rs1042821 variant homozygotes [adjusted odds ratio (OR)=3.42, 95% CI: 1.04-11.24, P=0.04, under the co-dominant model; adjusted OR=3.84, 95% CI: 1.18-12.44, P=0.03, under the recessive model]. The association was especially evident for the follicular histotype and female sex. The association was also apparent when MSH6 was analysed in combination with other MMR SNPs such as MSH3 rs26279. Interestingly, two other SNP combinations, both containing the MSH6 heterozygous genotype, were associated with a risk reduction, suggesting a protective effect for these genotype combinations. These data support the idea that MMR SNPs such as MSH6 rs1042821, alone or in combination, may contribute to DTC susceptibility. This is coherent with the limited evidence available. Nevertheless, further studies are needed to validate these findings and to establish the usefulness of these SNPs as genetic susceptibility biomarkers for DTC so that, in the near future, cancer prevention policies may be optimized under a personalized medicine perspective.

Prevalence of the Janus kinase 2 V617F mutation in Philadelphia-negative myeloproliferative neoplasms in a Portuguese population.

Myeloproliferative neoplasms (MPNs) result from the malignant transformation of a hematopoietic stem-cell (HSC), leading to abnormal amplification and proliferation of myeloid lineages. Identification of the Janus kinase 2 (JAK2) V617F mutation developed the knowledge of Philadelphia-negative (PN)-MPNs, contributing to and influencing the definition of the phenotype and prognostic impact. Considering the lack of Portuguese epidemiological data, the present study intends to characterize the prevalence of the JAK2 mutation in a PN-MPN versus a control Portuguese population. Caucasian Portuguese PN-MPN patients (n=133) and 281 matched control subjects were investigated. No significant differences were identified between the case and control groups concerning age distribution or smoking habits. Pathology distribution was as follows: 60.2% with essential thrombocythemia (ET), 29.3% with polycythemia vera (PV) and 10.5% with primary myelofibrosis (PMF). A total of 75.0% of patients were positive for the presence of the JAK2 V617F mutation. In addition, the prevalence of PV was 87.2%, ET was 73.4% and PMF was 50.0%. The JAK2 V617F mutation is observed in various MPN phenotypes, and has an increased incidence in ET patients and a decreased incidence in PV patients. These data may contribute to improving the knowledge of the pathophysiology of these disorders, and to a more rational and efficient selection of therapeutic strategies to be adopted, notably because most of the patients are JAK2 V617F negative.

DNA repair genes polymorphisms and genetic susceptibility to Philadelphia-negative myeloproliferative neoplasms in a Portuguese population: The role of base excision repair genes polymorphisms.

The role of base excision repair (BER) genes in Philadelphia-negative (PN)-myeloproliferative neoplasms (MPNs) susceptibility was evaluated by genotyping eight polymorphisms [apurinic/apyrimidinic endodeoxyribonuclease 1, mutY DNA glycosylase, earlier mutY homolog (E. coli) (MUTYH), 8-oxoguanine DNA glycosylase 1, poly (ADP-ribose) polymerase (PARP) 1, PARP4 and X-ray repair cross-complementing 1 (XRCC1)] in a case-control study involving 133 Caucasian Portuguese patients. The results did not reveal a correlation between individual BER polymorphisms and PN-MPNs when considered as a whole. However, stratification for essential thrombocythaemia revealed i) borderline effect/tendency to increased risk when carrying at least one variant allele for XRCC1_399 single-nucleotide polymorphism (SNP); ii) decreased risk for Janus kinase 2-positive patients carrying at least one variant allele for XRCC1_399 SNP; and iii) decreased risk in females carrying at least one variant allele for MUTYH SNP. Combination of alleles demonstrated an increased risk to PN-MPNs for one specific haplogroup. These findings may provide evidence for gene variants in susceptibility to MPNs. Indeed, common variants in DNA repair genes may hamper the capacity to repair DNA, thus increasing cancer susceptibility.

Glycidamide genotoxicity modulated by Caspases genes polymorphisms.

Acrylamide (AA) is amongst acknowledged carcinogenic dietary factors. Its DNA-reactive metabolite is glycidamide (GA). The present study intended to correlate the role of key polymorphic genes of apoptosis (CASP7, CASP8, CASP9, CASP10, LTA and TNFRSF1B) with biomarkers of effect of DNA damage, namely the sister chromatid exchange assay (SCE) and the comet assay in whole blood cells exposed to GA. The aim was to assess as a proof of concept the role that pro-apoptotic effector proteins might have in the yields of genotoxic effects when those effector proteins are coded by polymorphic genes. Whole blood from a small group of volunteers was exposed to GA to assess DNA damage and the volunteers were genotyped for polymorphic genes related to apoptosis pathways. A relation between the induction of SCE and several variants of the polymorphism CASP8 rs1035142 G>T was observed. Also, a relation between the % tail DNA and the CASP10 I522L polymorphism was found. Furthermore, associations between % tail DNA and several SNP-SNP interactions of CASP8 and CASP10 were found. A possible correlation between DNA damage and the genetic susceptibility, bestowed by polymorphic genes in the apoptosis inducing pathways was verified.

The role of CCNH Val270Ala (rs2230641) and other nucleotide excision repair polymorphisms in individual susceptibility to well-differentiated thyroid cancer.

Well-differentiated thyroid cancer (DTC) is the most common form of thyroid cancer (TC); however, with the exception of radiation exposure, its etiology remains largely unknown. Several single nucleotide polymorphisms (SNPs) have previously been implicated in DTC risk. Nucleotide excision repair (NER) polymorphisms, despite having been associated with cancer risk at other locations, have received little attention in the context of thyroid carcinogenesis. In order to evaluate the role of NER pathway SNPs in DTC susceptibility, we performed a case-control study in 106 Caucasian Portuguese DTC patients and 212 matched controls. rs2230641 (CCNH), rs2972388 (CDK7), rs1805329 (RAD23B), rs3212986 (ERCC1), rs1800067 (ERCC4), rs17655, rs2227869 (ERCC5), rs4253211 and rs2228529 (ERCC6) were genotyped using TaqMan® methodology, while conventional PCR-RFLP was employed for rs2228000 and rs2228001 (XPC). When considering all DTC cases, only rs2230641 (CCNH) was associated with DTC risk; a consistent increase in overall DTC risk was observed for both the heterozygous genotype (OR=1.89, 95% CI=1.14-3.14) and the variant allele carriers (OR=1.79, 95% CI=1.09-2.93). Histological stratification analysis confirmed an identical effect on follicular TC (OR=2.72, 95% CI=1.19-6.22, for heterozygous; OR=2.44, 95% CI=1.07­5.55, for variant allele carriers). Considering papillary TC, the rs2228001 (XPC) variant genotype was associated with increased risk (OR=2.33, 95% CI=1.05-5.16), while a protective effect was observed for rs2227869 (ERCC5) (OR=0.26, 95% CI=0.08­0.90, for heterozygous; OR=0.25, 95% CI=0.07-0.86, for variant allele carriers). No further significant results were observed. Our results suggest that NER polymorphisms such as rs2230641 (CCNH) and, possibly, rs2227869 (ERCC5) and rs2228001 (XPC), may influence DTC susceptibility. However, larger studies are required to confirm these results.

Polymorphisms in base excision repair genes and thyroid cancer risk.

Thyroid cancer (TC) is the most frequent endocrine malignancy, accounting however for only 1-2% of all human cancers, and the best-established risk factor for TC is radiation exposure, particularly during childhood. Since the BER pathway seems to play an important role in the repair of DNA damage induced by IR and other genotoxicants, we carried out a hospital-based case-control study in order to evaluate the potential modifying role of 6 BER polymorphisms on the individual susceptibility to non-familial TC in 109 TC patients receiving iodine-131, and 217 controls matched for age (± 2 years), gender and ethnicity. Our results do not reveal a significant involvement of XRCC1 Arg194Trp and Arg399Gln, OGG1 Ser326Cys, APEX1 Asp148Glu, MUTYH Gln335His and PARP1 Val762Ala polymorphisms on the individual susceptibility towards TC, mostly in agreement with the limited available evidence. By histological stratification analysis, we observed that the association between the presence of heterozygosity in the MUTYH Gln335His polymorphism and TC risk almost reached significance for the papillary subtype of TC. This was the first time that the putative association between this polymorphism and TC susceptibility was evaluated. However, since the sample size was modest, the possibility of a type I error should not be excluded and this result should, therefore, be interpreted with caution. More in depth studies involving larger populations should be pursued in order to further clarify the potential usefulness of the MUTYH Gln335His genotype as a predictive biomarker of susceptibility to TC and the role of the remaining BER polymorphisms on TC susceptibility.

SNPs/pools: a methodology for the identification of relevant SNPs in breast cancer epidemiology.

The identification of allelic variants of human genes is of great importance when assessing genetic susceptibility. The emerging role of genetic polymorphisms in association studies has created the need for high throughput genotyping methodologies that allow a more rapid identification of relevant polymorphisms related to individual cancer risk enabling the extension to large-scale association studies. DNA pooling methodology may be of great importance considering the cost, time and labor that are involved in large-scale genotyping analysis carried out on individual samples. Alternatively, when using pooled samples which are made up of DNA from many individuals treated as a single sample, these factors are decrease drastically. In this way, the use of DNA pooling methodology, as a pre-selection tool, allows the identification of the most relevant polymorphisms to be studied, facilitating the estimation of the allelic frequency of each SNP in different populations. The present study initially aimed to validate the DNA pooling approach for the identification of genetic polymorphisms potentially associated with individual cancer risk generating pools with known allelic frequencies and using studies ongoing in the laboratory. Finally, our main aim was to test the accuracy of the pooled DNA analysis comparing the results of the allelic frequencies determined using pooled samples with the allelic frequency previously estimated by individual genotyping and previously published. In order to analyze the possibility of establishing differences between populations, we created DNA pools using a Portuguese control population, a breast cancer population and a Xavante Indian population characterized by a total absence of breast cancer cases. The pools were firstly created with known allelic frequencies, previously determined by individual genotyping, and, latter, randomly incremented in sample size to 200 patients and controls. Our results showed that the DNA pooling approach was a useful tool for the analysis of allelic distribution in the different populations studied. Ιn conclusion, our results showed that this methodology can be applied as an effective approach to identify SNPs of importance in genetic susceptibility to disease which may be used in association studies conducted subsequently by individual genotyping.

Breast cancer risk and common single nucleotide polymorphisms in homologous recombination DNA repair pathway genes XRCC2, XRCC3, NBS1 and RAD51.

The possible role for DNA repair deficiencies in cancer development, namely in breast cancer has been the subject of increasing interest since it has been reported that breast cancer patients might be deficient in the repair of DNA damage. Exposure to ionizing radiation has been pointed out as a risk factor for breast cancer, and the type of DNA lesions induced by this carcinogen can be repaired by homologous recombination DNA repair (HRR) pathway. To evaluate the potential modifying role of some single nucleotide polymorphisms (SNP) in HRR involved genes on the individual susceptibility to breast cancer we carried out a hospital based case-control study in a Caucasian Portuguese population (289 histological confirmed breast cancer patients and 548 control individuals). We genotyped 4 SNPs in 4 different HRR pathway genes, XRCC2 (Ex3+442G>A, R188H, rs3218536), XRCC3 (Ex8-5C>T, T241M, rs861539), NBS1 (Ex5-32C>G, E185Q, rs1805794) and RAD51 5'UTR (Ex1-59G>T, rs1801321), tagging 41 SNPs in these genes. The frequency of the different polymorphisms in the Portuguese control population is similar to the ones reported for other Caucasian populations, and the deviation of the Hardy-Weinberg equilibrium was only observed for the XRCC2 (Ex3+442G>A, R188H, rs3218536) polymorphism in the control population. The results obtained, after logistic regression analysis, did not reveal a major role of these polymorphisms on breast cancer susceptibility. However, when the population was stratified according to breast feeding (women that breast fed and women that never breast fed) it is observed, in women that never breast fed, that the heterozygous individuals for the XRCC2 (Ex3+442G>A, R188H, rs3218536) polymorphism have a decreased risk for breast cancer [adjusted OR=0.45; 95% CI=0.22-0.92] (P=0.03). Additionally, after stratification according to menopausal status, our results suggest that post-menopausal women carrying at least one variant allele for the XRCC3 (Ex8-5C>T, T241M, rs861539) polymorphism have a lower risk for breast cancer [adjusted OR=0.67; 95% CI, 0.47-0.94] (P=0.03). Most of the studies suggest that breastfeeding may be responsible for 2/3 of the estimate reduction of breast cancer. The longer the duration of breastfeeding the lower the potential risk associated with breast cancer. Therefore, in our study the potential protective role of the variant allele of XRCC2 (Ex3+442G>A, R188H, rs3218536), in never breast fed women, might be related with a more efficient DNA repair activity.

Association of common variants in mismatch repair genes and breast cancer susceptibility: a multigene study.

BACKGROUND: MMR is responsible for the repair of base-base mismatches and insertion/deletion loops. Besides this, MMR is also associated with an anti-recombination function, suppressing homologous recombination. Losses of heterozygosity and/or microsatellite instability have been detected in a large number of skin samples from breast cancer patients, suggesting a potential role of MMR in breast cancer susceptibility. METHODS: We carried out a hospital-based case-control study in a Caucasian Portuguese population (287 cases and 547 controls) to estimate the susceptibility to non-familial breast cancer associated with some polymorphisms in mismatch repair genes (MSH3, MSH4, MSH6, MLH1, MLH3, PMS1 and MUTYH). RESULTS: Using unconditional logistic regression we found that MLH3 (L844P, G>A) polymorphism GA (Leu/Pro) and AA (Pro/Pro) genotypes were associated with a decreased risk: OR = 0.65 (0.45-0.95) (p = 0.03) and OR = 0.62 (0.41-0.94) (p = 0.03), respectively.Analysis of two-way SNP interaction effects on breast cancer revealed two potential associations to breast cancer susceptibility: MSH3 Ala1045Thr/MSH6 Gly39Glu - AA/TC [OR = 0.43 (0.21-0.83), p = 0.01] associated with a decreased risk; and MSH4 Ala97Thr/MLH3 Leu844Pro - AG/AA [OR = 2.35 (1.23-4.49), p = 0.01], GG/AA [OR = 2.11 (1.12-3,98), p = 0.02], and GG/AG [adjusted OR = 1.88 (1.12-3.15), p = 0.02] all associated with an increased risk for breast cancer. CONCLUSION: It is possible that some of these common variants in MMR genes contribute significantly to breast cancer susceptibility. However, further studies with a large sample size will be needed to support our results.

Association of polymorphisms in genes of the homologous recombination DNA repair pathway and thyroid cancer risk.

BACKGROUND: Ionizing radiation exposure has been pointed out as a risk factor for thyroid cancer. The double-strand breaks induced by this carcinogen are usually repaired by homologous recombination repair pathway, a pathway that includes several polymorphic genes. Since there is a scarcity of data about the involvement of these gene polymorphisms in thyroid cancer susceptibility, we carried out a case-control study in a Caucasian Portuguese population. METHODS: We genotyped 109 patients and 217 controls for the XRCC3 T241M, XRCC2 R188H, NBS1 E185Q, and RAD51 Ex1-59G>T polymorphisms to evaluate their potential main effects on risk for this pathology. RESULTS: The results obtained showed that for the RAD51 Ex1-59G>T polymorphism, the homozigosity for the variant allele was associated with an almost significant increase of the odds ratio (OR) (adjusted OR = 1.9; confidence interval 95%: 1.0-3.5; p = 0.057). Additionaly, when the XRCC3 T241M data were analyzed concerning the presence of at least one wild-type allele, we observed that individuals homozygous for the variant allele had a higher risk for thyroid cancer (adjusted OR = 2.0; confidence interval 95%: 1.1-3.6; p = 0.026). When the data were analyzed according to the number of RAD51 Ex1-59G>T and XRCC3 T241M variant alleles, the coexistence of three or more variant alleles in either gene was associated to a significant higher risk (three variant alleles: adjusted OR = 2.9, p = 0.036; four variant alleles: adjusted OR = 8.0, p = 0.006). CONCLUSIONS: Since XRCC3 is involved in the assembly and stabilization of RAD51 protein multimers at double-strand break sites, we cannot exclude that the interaction of both polymorphisms can lead to a decreased DNA repair capacity and consequently increased risk for thyroid cancer.

The role of GSTA2 polymorphisms and haplotypes in breast cancer susceptibility: a case-control study in the Portuguese population.

Glutathione-S-transferases (GSTs) are a super-family of phase II metabolizing enzymes that catalyse the detoxification of a large range of endogenous and exogenous toxic compounds, playing an important role in protecting cells against damage, through glutathione conjugation with electrophilic substances. Polymorphic variation in these enzymes that affect its activity seems to be related to individual susceptibility to various human diseases, including cancer. Of the GST super-family, the alpha class GSTs have commonly been described as one of the most versatile class, since it is responsible for detoxification of compounds such as bilirubin, bile acids and penicillin, thyroid and steroid hormones, allowing its solubilization and storage in the liver. Among the alpha class, GSTA1 and GSTA2 isoforms are the most widely expressed in human tissues. Additionally, these enzymes can catalyse conjugation of the nitrogen mustard group of alkylating anticancer drugs, some heterocyclic amines and alpha,beta-unsaturated aldehydes. Since some risk factors for increased breast cancer risk could be related to high production of reactive oxygen species during the metabolism of estrogens by catechol estrogens, or to the exposure to genotoxic compounds, and some of these toxic compounds are usually metabolized by GSTA2, we carried out a hospital based case-control study in a Caucasian Portuguese population (291 breast cancer patients without familiar history of breast cancer and 547 controls matched for age, sex and ethnicity) in order to evaluate the potential modifying role of three non-synonymous polymorphisms in the GSTA2 gene (P110S Ex 5+56C>T;, rs2234951; S112T Ex5+63G>C, rs2180314 and E210A Ex7+83A>C, rs6577) on the individual susceptibility to breast cancer. Our data show that the studied polymorphisms are in strong linkage disequilibrium, but no association was observed between individual GSTA2 polymorphisms and haplotypes and individual susceptibility to breast cancer.

Menopausal age and XRCC1 gene polymorphisms: role in breast cancer risk.

BACKGROUND: Recent evidence that some DNA-repair functions are haploinsufficient adds weight to the notion that variants in DNA-repair genes constitute part of the spectrum of defects contributing to cancer risk. X-ray repair cross-complementing group 1 gene (XRCC1) is involved in base excision repair (BER) pathway, acting on spontaneous and induced DNA damage. This gene encodes for a scaffolding protein that brings together different proteins involved in the repair process. Among the non-synonymous polymorphisms in XRCC1 gene, codons 194 and 399 lead to amino acid changes at evolutionary conserved regions, and seem to alter the efficiency of the protein. METHODS: A hospital based case-control study was carried out in a Caucasian Portuguese population (241 cancer patients and 457 controls matched for sex and age) in order to evaluate the potential modifying role of the XRCC1 polymorphisms on the individual susceptibility to breast cancer. RESULTS: Our data did not reveal a positive association between the polymorphisms individually and breast cancer, or with the combination of the different genotypic associations. However, after stratification to the menopausal status, it was observed that carriers of the Gln/Gln genotype of the R399Q polymorphism with a menopausal age above 55 years are at increased risk for breast cancer (OR=4.074; CI=1.562-10.626; P=0.004). Concerning the Arg194Trp polymorphism, after stratification by menopausal status, it was observed that heterozygous individuals (Arg/Trp) with a menopausal age between 45 and 54 are at increased risk for breast cancer (adjusted OR=1.964; CI=1.174-3.288; P=0.01) as well as carriers of the variant allele (Arg/Trp+Trp/Trp) (adjusted OR=1.932; CI=1.156-3.228; P=0.012). CONCLUSIONS: Our results suggest that menopausal age together with Arg194Trp and Arg399Gln XRCC1 gene polymorphisms might be involved in individual susceptibility to breast cancer.

Breast cancer risk and polymorphisms in genes involved in metabolism of estrogens (CYP17, HSD17beta1, COMT and MnSOD): possible protective role of MnSOD gene polymorphism Val/Ala and Ala/Ala in women that never breast fed.

Polymorphisms in genes encoding enzymes involved in estrogen metabolism are held to be candidates for associations with breast disease, since there is evidence that circulating estrogens are associated with breast cancer risk. In this study, we evaluated the frequency of different polymorphisms related with estrogen metabolism [COMT Val158Met, CYP17 (5'UTR, T27C); HSD17beta1 Gly313Ser and MnSOD Val16Ala] in a breast cancer resistant population, the Xavante Indians, and the frequencies were compared with the ones reported in other populations where breast cancer case-control studies dealing with these polymorphisms have been carried out. The data obtained showed that, apart from the MnSOD Val16Ala polymorphism where the frequency of the variant allele was much higher than that reported in other populations, all the others were within the range reported in other populations. Considering these data we carried out a case-control study in the Portuguese population (241 cases and 457 controls) in order to evaluate the potential role of this polymorphism in breast cancer susceptibility. The results obtained did not reveal a significant association between individual genotypes and breast cancer risk. However, when the population was stratified for breast feeding, it was observed that for the patients that never breast fed the presence of the variant allele (Ala) was marginally associated with a decreased risk for this pathology (adjusted OR: 0.575 (0.327-1.011). These data seem to suggest that individuals who never breast fed with MnSOD Val16Ala variant allele are at a lower risk for breast cancer, but larger studies are required to confirm these results.

Association of polymorphisms in ERCC2 gene with non-familial thyroid cancer risk.

The ERCC2 protein is an evolutionary conserved ATP-dependent helicase that is associated with a TFIIH transcription factor complex and plays an important role in nucleotide excision repair. Mutations in this gene are responsible for xeroderma pigmentosum and also for Cocayne syndrome and trichothiodystrophy. Several single nucleotide polymorphisms have been identified in the ERCC2 locus. Among them, a G23591A polymorphism in the codon 312 results in an Asp --> Asn substitution in a conserved region and a A35931C polymorphism in the codon 751 results in a Lys --> Gln substitution. Because these polymorphisms have been associated with an increased risk for several types of cancers, we carried out an hospital based case-control study in a Caucasian Portuguese population to evaluate the potential role of these polymorphisms on the individual susceptibility to thyroid cancer. The results obtained did not reveal a significant association between each individual polymorphism studied (G23591A and A35931C) and an increased thyroid cancer risk, but individuals homozygous for non-wild-type variants are overrepresented in patients group. The evaluation of the different haplotypes generated by these polymorphisms showed that individuals simultaneously homozygous for rare variants of both polymorphisms have an increased risk for thyroid cancer [adjusted odds ratio (OR) 3.084; 95% confidence interval (95% CI), 1.347-7.061; P = 0.008] and for papillary thyroid-type tumors (adjusted OR, 2.997; 95% CI, 1.235-7.272; P = 0.015) but not for follicular thyroid-type tumors. These results suggest that genetic polymorphisms in this gene might be associated with individual susceptibility towards thyroid cancer, mainly papillary-type tumors, but larger studies are required to confirm these results.

Multiplex PCR-single-base extension genotyping of multiple glutathione S-transferase polymorphisms.

Identification of genetic polymorphisms has recently gained increased interest, since they can be used as markers to identify the genes that predispose to disease. This emerging role of genetic polymorphism in clinical association has created the need for high-throughput genotyping methodologies. The present study describes the development of an SBE (single-base extension) methodology for the parallel identification of genetic polymorphisms in glutathione S-transferase genes, a superfamily of phase II drug-metabolizing enzymes. Oligonucleotide PCR primers were designed for simultaneous amplification of GSTM1, GSTP1 and GSTT1 gene loci SBE primers were also designed to be specific for each loci and to stop one nucleotide 5'-upstream of the polymorphic location. A specific tag was associated with each SBE primer to guarantee further discrimination by length. After simultaneous amplification of the target gene loci from genomic DNA extracted from human blood samples, SBE reactions were performed with fluorescently labelled dideoxynucleotide triphosphates. Individual genotypes were identified after separation of each tag-SBE probe by PAGE. The multiplex/SBE methodology was validated with previously genotyped DNA samples extracted from 21 individuals and it was used in a blind assay to genotype additional 64 individuals. The results show that SBE leads to the same results as the current 'gold standard' restriction-fragment-length-polymorphism-based genotyping methodologies, since SBE is a robust and accurate genotyping methodology that enables the parallel identification of multiple polymorphisms in the same reaction.