Possible role of the WDR3 gene on genome stability in thyroid cancer patients.

The role of the WDR3 gene on genomic instability has been evaluated in a group of 115 differentiated thyroid cancer (DTC) patients. Genomic instability has been measured according to the response of peripheral blood lymphocytes to ionizing radiation (0.5 Gy). The response has been measured with the micronucleus (MN) test evaluating the frequency of binucleated cells with MN (BNMN), both before and after the irradiation. No differences between genotypes, for the BNMN frequencies previous the irradiation, were observed. Nevertheless significant decreases in DNA damage after irradiation were observed in individuals carrying the variant alleles for each of the three genotyped SNPs: rs3754127 [-8.85 (-15.01 to -2.70), P<0.01]; rs3765501 [-8.98 (-15.61 to -2.36), P<0.01]; rs4658973 [-8.70 (-14.94 to -2.46), P<0.01]. These values correspond to those obtained assuming a dominant model. This study shows for the first time that WDR3 can modulate genome stability.

Are thyroid cancer patients sensitive to ionising radiation?

PURPOSE: To determine the ionising radiation sensitivity of peripheral blood lymphocytes in a group of differentiated thyroid cancer (DTC) patients. MATERIAL AND METHODS: A total of 53 thyroid cancer patients (26 women and 27 men) and 50 donors (23 women and 27 men) were included in the study. The cytokinesis-block micronucleus assay (CBMN) in G0 peripheral blood lymphocytes was carried out using the cytochalasin B technique. Four cultures were established per each donor, two were irradiated with 0.5 Gy 137Cs g-rays, while the other two remained untreated. RESULTS: No significant differences were observed in the frequency of binucleated cells with micronuclei (BNMN) between patients and controls, for both spontaneous and after the irradiation frequencies. Nevertheless, a positive and significant correlation was found between the frequencies of both spontaneous and after irradiation DNA damage, for control and patient groups. CONCLUSIONS: We have found that DTC patients do not present particular sensitivity to ionising radiation when an in vitro treatment is performed in G0 stage of the cell cycle, but this result does not discard the hypothesis about an increased sensitivity in other stages of the cell cycle in DTC patients.

Association studies of OGG1, XRCC1, XRCC2 and XRCC3 polymorphisms with differentiated thyroid cancer.

The role of the DNA repair genes OGG1, XRCC1, XRCC2 and XRCC3 on differentiated thyroid cancer (DTC) susceptibility was examined in 881 individuals (402 DTC and 479 controls). DNA repair genes were proposed as candidate genes, since the current data indicate that exposure to ionizing radiation is the only established factor in the development of thyroid cancer, especially when it occurs in early stages of life. We have genotyped DNA repair genes involved in base excision repair (BER) (OGG1, Ser326Cys; XRCC1, Arg280His and Arg399Gln), and homologous recombination repair (HRR) (XRCC2, Arg188His and XRCC3, ISV-14G). Genotyping was carried out using the iPLEX (Sequenom) technique. Multivariate logistic regression analyses were performed in a case-control study design. From all the studied polymorphism, only a positive association (OR=1.58, 95% CI 1.05-2.46, P=0.027) was obtained for XRCC1 (Arg280His). No associations were observed for the other polymorphisms. No effects of the histopathological type of tumor were found when the DTC patients were stratified according to the type of tumor. It must be emphasized that this study include the greater patients group, among the few studies carried out until now determining the role of DNA repair genes in thyroid cancer susceptibility.

Genetic investigation of FOXE1 polyalanine tract in thyroid diseases: new insight on the role of FOXE1 in thyroid carcinoma.

FOXE1 polyalanine tract (poly-Ala) has been associated with thyroid dysgenesis. Recently, the SNP (rs1867277:-238G>A) within the FOXE1 5'UTR was involved in the genetic susceptibility to thyroid cancer (TC). In the aim to assess the influence of FOXE1 poly-Ala length on the genetic susceptibility to TC and autoimmune thyroid diseases (AITD), a case-control design (including 261 Tunisian AITD, 170 Spanish TC and respectively 171 and 218 matched healthy subjects) was performed. The effect of Ala length and rs1867277 alleles on FOXE1 expression was investigated by mRNA relative real time quantification on 8 papillary thyroid carcinoma (PTC) and 10 Graves' disease (GD) genotyped thyroid biopsies. The fluorescent genotyping of poly-Ala polymorphism revealed nine alleles (from 12 to 22 repetitions). The association of poly-Ala polymorphism with AITD was rejected (Pc>0.05). However, a significant association was found with TC. In addition, the genotypic distributions revealed the predispositional effect of the 16/16 genotype (OR = 2.71; 95%CI: 1.36-5.42; p=0.001) and the protector effect of the 14/14 genotype (OR= 0.46; 95%CI: 0.29-0.72; p=0.003). The quantification studies reveal that FOXE1 transcripts were less abundant in PTC than GD samples. Moreover, FOXEI gene was 4,8 fold less expressed among PTC protected patients compared to homozygous 16/16-A/A. In conclusion, by exploring the poly-Ala polymorphism, we confirmed the involvement of {\it FOXE1} gene in the genetic susceptibility to TC and we reported its down expression among PTC tissues.

Strong association of chromosome 1p12 loci with thyroid cancer susceptibility.

Several genes directly related to thyroid cancer development have been described; nevertheless, the genetic pathways of this tumorigenesis process are unknown. Together with environmental factors, susceptibility genes could have an important role in thyroid cancer. Our previous studies suggest that the chromosome 1p12-13 is related to thyroid cancer incidence. Here, we extend the analysis with a case-control association study in a Spanish population. Thus, six single-nucleotide polymorphisms were genotyped, covering 2.4 Mb of the 1p12-13 region. A statistically significant association between thyroid cancer incidence and the rs2145418 and rs4658973 polymorphisms was found (P < 0.0001). No association was detected for the other four polymorphisms studied. The rs2145418 marker showed a significant odds ratio of 5.0 [95% confidence interval (95% CI), 2.85-8.83] and 9.2 (95% CI, 4.50-21.6) for heterozygous and homozygous G-variant alleles, respectively. For rs4658973, the odds ratios were 0.40 (95% CI, 0.26-0.62) and 0.07 (95% CI, 0.03-0.18) for heterozygous and homozygous G-variant alleles, respectively. These markers map into the 1p12 region, and no linkage disequilibrium was found between them, indicating an independent relation of these polymorphisms with thyroid cancer susceptibility. Our data provide evidence of a strong association of the chromosome 1p12 with thyroid cancer risk, and it is the first study describing susceptibility loci for thyroid cancer in this region.

Basal and induced micronucleus frequencies in human lymphocytes with different GST and NAT2 genetic backgrounds.

Basal and induced frequencies of genetic damage can be modulated by different host factors, including genes involved in phase II metabolism. Since polymorphic variants in the glutathione S-transferase (GST) and N-acetyl transferase (NAT) genes have been associated with cancer risk, we explored the possible links between GSTM1, GSTP1, GSTT1 and NAT2 variants and the frequency of micronuclei (MN) in human lymphocytes. This exploratory study was carried out in 30 thyroid cancer patients, before and after receiving an average dose of 109.9+/-1.3 mCi radioactive iodine as a co-adjuvant therapy. The results indicate that none of the polymorphisms studied show any kind of association with the basal level of micronuclei. When the same patients were followed after radioiodine exposure, a significant increase in the frequency of MN was observed in practically all of them (28/30), indicating the genotoxic activity of the ionising radiation exposure. The increase in MN frequency was not associated with any of the GST polymorphisms evaluated. Nevertheless, the presence of slow acetylator phenotypes and, in particular, the presence of the NAT2*7 allele was significantly associated with a lower increase of the MN frequency after radioiodine treatment.

Thyroid cancer susceptibility and THRA1 and BAT-40 repeats polymorphisms.

Although genetic and environmental factors have been identified in the etiology of thyroid cancer, the specific genetic implications in sporadic thyroid tumors are poorly understood but, as in other common cancers, low-penetrance susceptibility genes are believed to be crucial in the tumorigenesis processes. Here, we have carried out a case-control study to investigate whether there is an association between THRA1 CA repeat or BAT-40 A repeat polymorphisms and thyroid cancer risk. The THRA1 repeat resides in the thyroid hormone receptor-alpha1 gene, which is associated with thyroid cancer and whose expression depends on the THRA1 repeat size. We also analyzed the BAT-40 repeat that maps to chromosome 1, a region known to be involved in thyroid cancer. This repeat is located in the 3-beta-hydroxysteroid dehydrogenase gene that is associated with prostate cancer susceptibility. The THRA1 repeat was genotyped in 212 thyroid cancer patients and 141 controls of a Spanish population. From these individuals, 207 patients and 138 controls were also analyzed for the BAT-40 marker. No significant difference in the THRA1 allele distribution between patients and controls was found, although short alleles (<128 bp) might have some protective effect on thyroid cancer risk of carriers (odds ratio, 0.50; 95% confidence interval, 0.22-1.13; P = 0.094). By contrast, the BAT-40 allele distribution in patients was significantly different with respect to control (P = 0.035). Essentially, the difference were found in the genotypes involving the 111- to 115-bp allele range, which seem to be associated with a protective effect on thyroid cancer susceptibility in the studied population (odds ratio, 0.18; 95% confidence interval, 0.01-0.57; P = 0.02). Therefore, our results indicate that the BAT-40 containing region and to a less extend the thyroid hormone receptor-alpha1 gene are related to thyroid cancer susceptibility. To our knowledge, this is the first study reporting the identification of genetic factors for thyroid cancer susceptibility.

Glutathione S-transferase polymorphisms in thyroid cancer patients.

Glutathione S-transferases (GST) are enzymes involved in the metabolism of many carcinogens and mutagens, also acting as important free-radical scavengers. The existence of different genetic polymorphisms in human populations has proven to be a susceptibility factor for different tumours. Nevertheless, as far as we know, for thyroid cancer no study has been conducted until now linking its incidence to genetic susceptibility biomarkers. The present investigation has been conducted to detect the possible association between polymorphism at the GSTM1, GSTT1 and GSTP1 genes and thyroid cancer incidence. Thus, 134 thyroid cancer patients and 116 controls, all from the urban district of Barcelona (Spain), have been included in this study. The results indicate that, according to the calculated odds ratio, the frequencies of the different genotypes found in the group of cancer patients do not significantly differ from those values obtained in the controls. This is true for the overall data as well as for the tumour characterization as follicular and papillar types. In addition, none of the possible combinations of mutant genotypes were shown to be risk factors. Finally, when the sex of the patients, the age of tumour onset, and life-style habits were also taken into account, no influence was observed related to the different genotypes. In conclusion, the results obtained in this study clearly suggest that those susceptibility factors related to the different GST polymorphic enzymes are not a predisposing factor in thyroid cancer disease.