Natassia Elena Bufalo

Smoking and susceptibility to thyroid cancer: an inverse association with CYP1A1 allelic variants

In contrast to most human malignancies, epidemiologic studies have frequently reported a reduced risk of differentiated thyroid cancer in tobacco consumers. Cytochrome P4501A1 (CYP1A1) gene variants may be related to an increased capacity to activate polycyclic aromatic hydrocarbons, producing highly reactive electrophilic intermediates that might damage DNA. Hence, the germline inheritance of a wild-type CYP1A1 gene may decrease the susceptibility for thyroid cancer. The present study was designed to investigate CYP1A1 (m1 and m2) role in thyroid tumorigenesis and its connection with GSTM1, GSTT1, GSTP1, GSTO1, and codon 72 of p53 genotypes. A total of 248 patients with thyroid nodules, including 67 benign goiters, 13 follicular adenomas, 136 papillary carcinomas, and 32 follicular carcinomas, and 277 controls with similar ethnic backgrounds were interviewed on their lifetime dietary and occupational histories, smoking habit, previous diseases, and other anamnestic data. DNA was extracted from a blood sample and submitted to PCR-restriction fragment length polymorphism assays. The wild-type CYP1A1m1 genotype was more frequent among papillary carcinoma patients (74.26%) than in the control population (62.45%; P=0.0147), reducing the risk for this type of cancer (odds ratio=0.564; 95% confidence interval=0.357-0.894). A multiple logistic regression analysis showed an inverse correlation between cigarette smoking (P=0.0385) and CYP1A1 germline inheritance (P=0.0237) with the susceptibility to papillary carcinomas. We were not able to find any correlation between smoking, clinical features, parameters of aggressiveness at diagnosis or during follow-up, and any of the GST or CYP genotypes considered separately or in different combinations. We suggest that CYP1A1 genotype might be associated with the reported reduced risk to papillary carcinomas among smokers.

The influence of the environment on the development of thyroid tumors: a new appraisal

Most epidemiological studies concerning differentiated thyroid cancers (DTC) indicate an increasing incidence over the last two decades. This increase might be partially explained by the better access to health services worldwide, but clinicopathological analyses do not fully support this hypothesis, indicating that there are carcinogenetic factors behind this noticeable increasing incidence. Although we have undoubtedly understood the biology and molecular pathways underlying thyroid carcinogenesis in a better way, we have made very little progresses in identifying a risk profile for DTC, and our knowledge of risk factors is very similar to what we knew 30-40 years ago. In addition to ionizing radiation exposure, the most documented and established risk factor for DTC, we also investigated the role of other factors, including eating habits, tobacco smoking, living in a volcanic area, xenobiotics, and viruses, which could be involved in thyroid carcinogenesis, thus, contributing to the increase in DTC incidence rates observed.

Genetic polymorphisms associated with cigarette smoking and the risk of Graves’ disease

Objective  Cigarette smoking is a well‐recognized risk factor of Graves’ disease and, particularly, Graves’ ophthalmopathy. Hence, germline polymorphisms of detoxification genes and genes belonging to the major DNA repair–apoptosis pathways might have an important role in disease susceptibility. In addition, as some of these genes are regulated by thyroid hormones, they may affect the patients’ outcomes. We aimed to assess the influence of the GST, CYP and TP53 gene polymorphisms in the risk of Graves’ disease and its outcome.

Identifying a Risk Profile for Thyroid Cancer

The large use of simple and effective diagnostic tools has significantly contributed to the increase in diagnosis of thyroid cancer over the past years. However, there is compelling evidence that most micropapillary carcinomas have an indolent behavior and may never evolve into clinical cancers. Therefore, there is an urgent need for new tools able to predict which thyroid cancers will remain silent, and which thyroid cancers will present an aggressive behavior. There are a number of well-established clinical predictors of malignancy and recent studies have suggested that some of the patients laboratory data and image methods may be useful. Molecular markers have also been increasingly tested and some of them appear to be very promising, such as BRAF, a few GST genes and p53 polymorphisms. In addition, modern tools, such as immunocytochemical markers, and the measure of the fractal nature of chromatin organization may increase the specificity of the pathological diagnosis of malignancy and help ascertain the prognosis. Guidelines designed to select nodules for further evaluation, as well as new methods aimed at distinguishing carcinomas of higher aggressiveness among the usually indolent thyroid tumors are an utmost necessity.

Role of the N-Acetyltransferase 2 Detoxification System in Thyroid Cancer Susceptibility

Purpose: Genetic polymorphisms in genes encoding for enzymes involved in the biotransformation of carcinogens have been shown to be relevant as risk for cancer and may be of considerable importance from a public health point of view. Considering that N-acetyltransferase 2 (NAT2) polymorphisms modulate the response to ionizing radiation, the strongest risk factor recognized to cause differentiated thyroid cancer (DTC) thus far, we sought to determine the influence of NAT2 detoxification system on thyroid cancer susceptibility. Experimental Design: We conducted a prospective case-control study, comparing 195 patients presenting with DTC that were previously genotyped for GSTT1, GSTM1, GSTP1, and CYP1A1, comprising 164 papillary carcinomas and 31 follicular carcinomas, with 196 control individuals paired for gender, age, ethnicity, diet routine, lifetime occupational history, smoking history, general health conditions, and previous diseases. We used PCR-RFLP assays and the combination of 6 variant alleles to define 18 NAT2 haplotypes that characterized slow, intermediate, or rapid phenotypes. Results: A multivariate logistic regression analysis identified the presence of *12A and the absence of *12B, *13, *14B, *14D, *6A, and *7A NAT2 haplotypes as risk factors for DTC. The inheritance of a rapid acetylation phenotype doubled the risk for a papillary carcinoma (odds ratio, 2.024; 95% confidence interval, 1.252-3.272). We found no relationship between genotypes and clinical, pathologic, or laboratory features of patients or between genotypes and outcome. Conclusions: We showed that NAT2 genotypes and the NAT2 rapid acetylation phenotype are important susceptibility factors for DTC, suggesting that NAT2 detoxification system is involved in this tumor pathogenesis.

Evidence that polymorphisms in detoxification genes modulate the susceptibility for sporadic medullary thyroid carcinoma

AIM Polymorphic low-penetrance genes have been consistently associated with the susceptibility to a series of human tumors, including differentiated thyroid cancer. METHODS To determine their role in medullary thyroid cancer (MTC), we used TaqMan SNP method to genotype 47 sporadic MTC (s-MTC) and a control group of 578 healthy individuals for CYP1A2*F, CYP1A1m1, GSTP1, NAT2 and 72TP53. A logistic regression analysis showed that NAT2C/C (OR=3.87; 95% CI=2.11-7.10; P=2.2×10(-5)) and TP53C/C genotypes (OR=3.87; 95% CI=1.78-6.10; P=2.8×10(-4)) inheritance increased the risk of s-MTC. A stepwise regression analysis indicated that TP53C/C genotype contributes with 8.07% of the s-MTC risk. RESULTS We were unable to identify any relationship between NAT2 and TP53 polymorphisms suggesting they are independent factors of risk to s-MTC. In addition, there was no association between the investigated genes and clinical or pathological features of aggressiveness of the tumors or the outcome of MTC patients. CONCLUSION In conclusion, we demonstrated that detoxification genes and apoptotic and cell cycle control genes are involved in the susceptibility of s-MTC and may modulate the susceptibility to the disease.

Genes of detoxification are important modulators of hereditary medullary thyroid carcinoma risk

Different inherited profiles of genes involved in cellular mechanisms of activation and detoxification of carcinogenic products can provide specific protection or determine the risk for cancer. Low‐penetrance polymorphic genes related to the biotransformation of environmental toxins have been associated with susceptibility to and the phenotype of, human tumours.

Investigation on the association between thyroid tumorigeneses and herpesviruses

Herpesviruses have been associated with various human malignancies and with thyroid autoimmunity. Aiming to investigate the presence of these viruses in thyroid nodules, we analyzed serum and thyroid tissue from 183 patients (83 benign and 100 malignant thyroid nodules). We also obtained 104 normal thyroid tissues extracted from the contralateral lobe of these patients. We used ELISA to screen the serology of all patients and a real-time quantitative PCR to analyze thyroid tissue viral load in antibody-positive patients. In addition, the presence of herpesviruses was tested by histological analysis in 20 EBV-positive tissues using the expression of LMP-1 by immunohistochemistry (IHC) and EBER by in situ hybridization (ISH). There was no evidence of HSV-2 or CMV DNA, but we found EBV DNA sequences in 29 (16%) thyroid tissue samples. We also found 7 positive EBV cases out of 104 normal tissues. Viral load was higher in tumors than in their respective normal tissues (p = 0.0002). ISH analysis revealed EBER expression in 11 out of 20 (52%) EBV-positive tissues, mostly in malignant cases (8/11, 73%). The presence of high EBV copy numbers in thyroid tumors and the expression of EBER only in malignant cases suggest an association between EBV and thyroid malignancies. However, we did not find any association between the presence of EBV and/or its viral load and any clinical or pathological tumor feature. Further studies aiming to clarify the mechanisms of EBV infection in thyroid cells are necessary to support a possible role in the development of thyroid cancer.

Diagnostic utility of DREAM gene mRNA levels in thyroid tumours

OBJECTIVE The transcriptional repressor DREAM is involved in thyroid-specific gene expression, thyroid enlargement and nodular development, but its clinical utility is still uncertain. In this study we aimed to investigate whether DREAM mRNA levels differ in different thyroid tumors and how this possible difference would allow the use of DREAM gene expression as molecular marker for diagnostic and/or prognosis purpose. MATERIALS AND METHODS We quantified DREAM gene mRNA levels and investigated its mutational status, relating its expression and genetic changes to diagnostic and prognostic features of 200 thyroid tumors, being 101 malignant [99 papillary thyroid carcinomas (PTC) and 2 anaplastic thyroid carcinomas] and 99 benign thyroid lesions [49 goiter and 50 follicular adenomas (FA)]. RESULTS Levels of mRNA of DREAM gene were higher in benign (0.7909 ± 0.6274 AU) than in malignant (0.3373 ± 0.6274 AU) thyroid lesions (p < 0.0001). DREAM gene expression was able to identify malignancy with 66.7% sensitivity, 85.4% specificity, 84.2% positive predictive value (PPV), 68.7% negative predictive value (NPV), and 75.3% accuracy. DREAM mRNA levels were also useful distinguishing the follicular lesions FA and FVPTC with 70.2% sensitivity, 73.5% specificity, 78.5% PPV, 64.1% NPV, and 71.6% accuracy. However, DREAM gene expression was neither associated with clinical features of tumor aggressiveness, nor with recurrence or survival. Six different genetic changes in non-coding regions of DREAM gene were also found, not related to DREAM gene expression or tumor features. CONCLUSION We suggest that DREAM gene expression may help diagnose thyroid nodules, identifying malignancy and characterizing follicular-patterned thyroid lesions; however, it is not useful as a prognostic marker.

Thyroid Disruptors: How They Act and How We React

1.1 Actual thyroid disease demographics Thyroid diseases increase in a ubiquitous global phenomenon suspected to further rise in the upcoming decades (Dua et al. 2008). Thyroid cancer is the most common endocrine malignancy, representing 2% of all malignancies. A rapid global rise in its incidence has been seen in recent decades, especially concerning the papillary type, which has been increasing in several countries (Liu et al. 2001; Reynolds et al. 2005; Davies and Welch 2006; Enewold et al. 2009; Kilfoy, Devesa et al. 2009; Kilfoy, Zheng et al. 2009). An estimated 44,670 new cases of thyroid cancer are expected to be diagnosed in the United States of America in 2010, with three out of four cases occurring in women. The incidence rate of thyroid cancer has been increasing sharply since the mid-1990s, and it is the fastest growing cancer in both men and women, as well as the ninth most common human malignancy in the USA (American Cancer Society: Cancer Facts and Figures 2010). The reasons for the increase in occurrences of this type of cancer are still unclear and controversial. Earlier studies suspected that the upward trend was caused by the widespread use of radiation therapy for benign conditions of the head and neck among children and adolescents from the early 1920s to the late 1950s (Weiss 1979; Pottern et al. 1980). Other studies suggested that this trend could be associated with atmospheric nuclear fallouts (Catelinois et al. 2004; Gilbert et al. 1998; Kazakov, Demidchik, and Astakhova 1992; Kerber et al. 1993; Takahashi et al. 2003) or constant diagnostic X-ray exposures (Prokop 2001; Ron et al. 1995) suffered especially by children (Brenner et al. 2001; Golding and Shrimpton 2002; Maitino et al. 2003). More recent studies suggested that the prevalence of thyroid nodules depends on the screening method and population evaluated according to geographic regions and racial groups, indicating that the widespread use of ultrasonography and socioeconomic indicators of health care access could be the major players in this new demography of the thyroid cancer (Morris and Myssiorek 2010; Sprague, Warren Andersen, and Trentham-Dietz 2008). The steep increase in thyroid cancer is certainly related to better cancer detection by ultrasonography and other imaging techniques in a population growing older, as well as a larger and easier access to health care and robust laboratory diagnostic tools such as TSH and thyroid antibody dosages (Davies and Welch 2006; Ward and Graf 2008). However,