Association of polymorphisms in estrogen and thyroid hormone receptors with thyroid cancer risk

Trends of thyroid cancer in children and adolescents over 23 Years in KSA

Objective

This study aimed to determine the incidence of thyroid cancer (TC) in children and adolescents in the Kingdom of Saudi Arabia (KSA) during 23 years from 1994 to 2017.

Methods

Data were extracted from the Saudi National Cancer Registry for individuals aged 0-19 years diagnosed with TC from 1994 to 2017. TC incidence was retrospectively analyzed, age standardized for the Saudi Arabian population, and expressed per 100,000 people based on sex, nationality (Saudi and non-Saudi), and age at diagnosis (0-4, 5-9, 10-14, and 15-19 years). Data regarding the type of TC and tumor, node, and metastasis staging were excluded due to incomplete information.

Results

Overall, 706 patients were diagnosed with TC during the study period and 86.3 % were from KSA. The highest incidence (114) was observed between 2012 and 2014. The lowest crude incidence rate (CIR) was observed in 1994-1996 (4.45/100,000), and the CIR was highest among patients aged 15-16 years (26.7/100,000). Women were disproportionally affected by TC, with an average CIR of 45/100,000 compared with 8.2/100,000 in men. Geographically, Riyadh had the highest CIR, particularly in 2004 (6.9/100,000), 2016 (15.4/100,000), and 2017 (15.1/100,000).

Conclusion

A three-fold increase was observed in the incidence of TC among children and adolescents in KSA from 1994 to 2017, reaching a peak between 2012 and 2014. Further studies are warranted to investigate the factors that contributed to this increasing trend.

The Pattern of Thyroid Cancers in Nigeria: a Systematic Review and Meta-analysis

Thyroid cancer is the most common endocrine cancer. There are various histopathological types requiring different therapeutic approaches and having variable prognoses. The objective of this study was to determine the pattern of thyroid cancers in Nigeria. The systematically searched databases were African Journal Online, Google Scholar, PubMed, and SCOPUS. The pre-print databases Research Square, SciELO, and medRxiv were also systematically searched. Moreover, the available grey literature was equally searched. The quality of the selected studies was assessed using the Newcastle-Ottawa scale. The meta-analysis was done using Meta XL version 5.3. The DerSimonian Laird random effect model was used for the meta-analysis. The heterogeneity of the selected studies was determined using the I2 statistic and Cochran's Q test. Publication bias was assessed with the Luis Furuya-Kanamori (LFK) index and Doi plot. Twenty-six studies met the eligibility criteria. The total sample size was 1224. In Nigeria, thyroid cancer was most common in the 4th and 5th decades of life. It was 3.5 (95% CI 3.0-4.6, p < 0.0001) times commoner in females than males. The pooled proportions of thyroid cancers included papillary thyroid cancer, 46% (95% CI 40-53); follicular thyroid cancer, 39% (95% CI 32-45); medullary thyroid cancer, 7% (95% CI 6-9); and anaplastic thyroid cancer, 5% (95% CI 3-7). The trend showed a change from follicular cancer predominance to papillary cancer over the past two decades. Papillary thyroid cancer is the commonest type in Nigeria. Thyroid cancer is seen more in females and it occurs most commonly in middle age.

A review of complex hormone regulation in thyroid cancer: novel insights beyond the hypothalamus-pituitary-thyroid axis

Like the ovaries and prostate, the thyroid exhibits characteristic hormone secretion and regulation. Thyroid cancer (TC), especially differentiated thyroid carcinoma, has typical sex-specific and age-specific hormone-driven clinical features. Previous research has primarily focused on the effects of thyroid stimulating hormone, thyroid hormones, and estrogens on the onset and progression of TC, while the roles of growth hormone (GH), androgens, and glucocorticoids have largely been overlooked. Similarly, few studies have investigated the interactions between hormones and hormone systems. In fact, numerous studies of patients with acromegaly have shown that serum levels of GH and insulin-like growth factor-1 (IGF-1) may be associated with the onset and progression of TC, although the influences of age, sex, and other risk factors, such as obesity and stress, remain unclear. Sex hormones, the GH/IGF axis, and glucocorticoids are likely involved in the onset and progression of TC by regulating the tumor microenvironment and metabolism. The aim of this review was to clarify the roles of hormones and hormone systems in TC, especially papillary thyroid carcinoma, as references for further investigations.

Spectrum of EGFR mutation and its relation with high-risk predictors in thyroid cancer in Kashmiri population: 2 years prospective study at a tertiary care hospital

Background

EGFR mutation has not been extensively studied in thyroid cancer. This study was conducted to study spectrum of EGFR mutation in thyroid cancer in Kashmiri population for possible therapeutic purpose.

Methods

It was 2 years prospective cross-sectional study conducted at a tertiary care center in which histologically confirmed, untreated thyroid cancers were included. These specimens were subjected to EGFR mutation analysis by AS-PCR method.

Results

There were a total 60 patients with preponderance of females [44(73%) vs 16(27%)]. Most were in the age group of less than 45 years (75%). Most of these patients were non-smokers [50(83.3%) vs 10 (17.3%)]. Papillary thyroid carcinoma (PTC) was the commonest type 48(80%), rest was follicular type (FTC) 12(20%). Well-differentiated carcinoma (WDC) was common than poorly differentiated (PDC) [41(68.4%) vs 19 (31.6%)]. Lymph node metastasis and vascular invasion were present in 32 (53.4%) and 17 (28.4%) respectively. Thirty-two (53.3%) patients were having 15 bp deletion in exon 19 of EGFR. These deletions were common in PTC than FTC, 29(60.5%) vs 3(25%) which was statistically significant (p = 0.04, CI = 0.2). The total mutational rate of T790M in EGFR tyrosine kinase domain (exon 20) was found to be only 8.4% (5 of 60). Only 4 (8.3%) of these mutations were detected in PTC and rest in FTC (1 of 12). Twenty-six (43.3%) of exon 21 were positive for L858R mutation in EGFR tyrosine kinase domain. Married persons and PDC were significant predictors of L858R mutation in EGFR tyrosine kinase domain in thyroid cancer as this was statistically significant in them with p = 0.04, 0.03 respectively.

Conclusion

In our population, PTC is common in females with half of population harboring EGFR mutation and it is statistically significant in poorly differentiated carcinoma and in married individuals.

It implies that EGFR may be used in thyroid cancer as a possible therapeutic agent in our set of population.

MicroRNAs as the critical regulators of cell migration and invasion in thyroid cancer

Thyroid cancer (TC) is one of the most frequent endocrine malignancies that is more common among females. Tumor recurrence is one of the most important clinical manifestations in differentiated TC which is associated with different factors including age, tumor size, and histological features. Various molecular processes such as genetic or epigenetic modifications and non-coding RNAs are also involved in TC progression and metastasis. The epithelial-to-mesenchymal transition (EMT) is an important biological process during tumor invasion and migration that affects the initiation and transformation of early-stage tumors into invasive malignancies. A combination of transcription factors, growth factors, signaling pathways, and epigenetic regulations affect the thyroid cell migration and EMT process. MicroRNAs (miRNAs) are important molecular factors involved in tumor metastasis by regulation of EMT-activating signaling pathways. Various miRNAs are involved in the signaling pathways associated with TC metastasis which can be used as diagnostic and therapeutic biomarkers. Since, the miRNAs are sensitive, specific, and non-invasive, they can be suggested as efficient and optimal biomarkers of tumor invasion and metastasis. In the present review, we have summarized all of the miRNAs which have been significantly involved in thyroid tumor cells migration and invasion. We also categorized all of the reported miRNAs based on their cellular processes to clarify the molecular role of miRNAs during thyroid tumor cell migration and invasion. This review paves the way of introducing a non-invasive diagnostic and prognostic panel of miRNAs in aggressive and metastatic TC patients.

Trends in incidence and histological pattern of thyroid cancer in Ho Chi Minh City, Vietnam (1996-2015): a population-based study

BACKGROUND

The burden and trend of thyroid cancer in Vietnam have not been well documented. This study aimed to investigate the trends in incidence and histological pattern of thyroid cancer in Ho Chi Minh City from 1996 to 2015.

METHODS

A population-based study retrieved data from the Ho Chi Minh City Cancer Registry during 1996-2015. Trends in the incidence of thyroid cancer were investigated based on age, gender, and histology for each 5-year period. Annual percentage change (APC) in incidence rates was estimated using Joinpoint regression analysis.

RESULTS

In the study period, there were 5953 thyroid cancer cases (men-to-women ratio 1:4.5) newly diagnosed in Ho Chi Minh City with the mean age of 42.9 years (±14.9 years). The age-standardized incidence rate of thyroid cancer increased from 2.4 per 100,000 during 1996-2000 (95% confidence interval [95% CI]: 2.2-2.6) to 7.5 per 100,000 during 2011-2015 (95% CI: 7.3-7.9), corresponded to an overall APC of 8.7 (95% CI 7.6-9.9). The APC in men and women was 6.2 (95% CI: 4.2-8.2) and 9.2 (95% CI: 8.0-10.4), respectively. The incidence rate in the < 45 years age group was the highest diagnosed overall and increased significantly in both men (APC 11.0) and women (APC 10.1). Both genders shared similar distribution of subtype incidences, with papillary thyroid cancer constituted the most diagnosed (73.3% in men and 85.2% in women). The papillary thyroid cancer observed a markedly increase overall (APC of 10.7 (95% CI 9.3-12.0)).

CONCLUSIONS

There were appreciable increases in the age-standardized incidence rate of thyroid cancer in both genders, mainly contributed by the papillary subtype. The age of patients at diagnosis decreased gradually. The widespread utilization of advanced diagnostic techniques and healthcare accessibility improvement might play a potential role in these trends. Further investigations are needed to comprehend the risk factors and trends fully.

Cancer Incidence and Survival among Adolescents and Young Adults in Korea: An Update for 2016

PURPOSE

This study investigated the incidence and relative survival rates (RSRs) for cancers among adolescents and young adults (AYAs) aged 15-39 years between 1993 and 2016 in Korea.

Materials and Methods

Data from the Korea Central Cancer Registry were used to calculate percent distributions, age-specific incidence rates, age-standardized incidence rates (ASRs) per million, annual percent changes (APCs), average APCs, and RSRs for cancers diagnosed in AYAs.

RESULTS

ASR of all cancers among AYAs was 654.5 per million. The largest diagnosed group of cancers was carcinomas (almost 80%). Crude incidence increased with age, from 170.4 per million for those aged 15-19 years to 1,639.8 per million for those aged 35-39 years. ASR increased from 414.8 per million to 820.4 per million, with an APC of 9.0%. The incidence of thyroid carcinoma showed the most rapid increment (APC, 14.0%), followed by non-Hodgkin lymphoma (APC, 13.4%). The 5-year RSR among AYAs significantly improved from 62.1% to 90.8%. Survival improvement in AYAs was higher than that in children but lower than that in older adults (APC, 2.1% vs. 1.9% vs. 3.1%). The most marked survival improvement was found for leukemia and lymphoma. Astrocytoma, rhabdomyosarcoma, and carcinoma of the trachea, bronchus, and lung had a 5-year RSR of < 50%.

CONCLUSION

There was an improvement in cancer survivals in AYAs, comparable to that achieved in children. However, survivals in several cancer types do not appear to be improving. Further research focusing on the epidemiology and therapeutic strategies for cancers in AYAs is needed.

A Comprehensive Meta-analysis of Case-Control Association Studies to Evaluate Polymorphisms Associated with the Risk of Differentiated Thyroid Carcinoma

BACKGROUND

Linkage analyses and association studies suggested that inherited genetic variations play a role in the development of differentiated thyroid carcinoma (DTC).

METHODS

We combined the results from a genome-wide association study (GWAS) performed by our group and from published studies on DTC. With a first approach, we evaluated whether a SNP published as associated with the risk of DTC could replicate in our GWAS (using FDR as adjustment for multiple comparisons). With the second approach, meta-analyses were performed between literature and GWAS when both sources suggested an association, increasing the statistical power of the analysis.

RESULTS

rs1799814 (CYP1A1), rs1121980 (FTO), and 3 SNPs within 9q22 (rs965513, rs7048394, and rs894673) replicated the associations described in the literature. In addition, the meta-analyses between literature and GWAS revealed 10 more SNPs within 9q22, six within FTO, two within SOD1, and single variations within HUS1, WDR3, UGT2B7, ALOX12, TICAM1, ATG16L1, HDAC4, PIK3CA, SULF1, IL11RA, VEGFA, and 1p31.3, 2q35, 8p12, and 14q13.

CONCLUSION

This analysis confirmed several published risk loci that could be involved in DTC predisposition.

IMPACT

These findings provide evidence for the role of germline variants in DTC etiology and are consistent with a polygenic model of the disease. Cancer Epidemiol Biomarkers Prev; 25(4); 700-13. ©2016 AACR.

Identification of thyroid carcinoma related genes with mRMR and shortest path approaches

Thyroid cancer is a malignant neoplasm originated from thyroid cells. It can be classified into papillary carcinomas (PTCs) and anaplastic carcinomas (ATCs). Although ATCs are in an very aggressive status and cause more death than PTCs, their difference is poorly understood at molecular level. In this study, we focus on the transcriptome difference among PTCs, ATCs and normal tissue from a published dataset including 45 normal tissues, 49 PTCs and 11 ATCs, by applying a machine learning method, maximum relevance minimum redundancy, and identified 9 genes (BCL2, MRPS31, ID4, RASAL2, DLG2, MY01B, ZBTB5, PRKCQ and PPP6C) and 1 miscRNA (miscellaneous RNA, LOC646736) as important candidates involved in the progression of thyroid cancer. We further identified the protein-protein interaction (PPI) sub network from the shortest paths among the 9 genes in a PPI network constructed based on STRING database. Our results may provide insights to the molecular mechanism of the progression of thyroid cancer.

Association Study of FOS-Like Antigen-2 Promoter Polymorphisms With Papillary Thyroid Cancer in Korean Population

Objectives

FOS-like antigen-2 (FOSL-2), a member of the FOS gene family, encode leucine zipper proteins that can heterodimerize with proteins of Jun family. Thus, activating protein (AP)-1 transcription factor is formed, has a crucial role in proliferation, differentiation and apoptosis of normal tissue as well as oncogenic transformation and progression. We performed an association study of single nucleotide polymorphisms (SNPs) in the FOSL-2 with papillary thyroid cancer (PTC). We also estimated the relationships between the SNPs and the clinicopathologic characteristics of PTC.

Methods

One promoter SNPs (rs925255) of FOSL-2 gene were genotyped with direct sequencing method in 94 PTC and 213 controls. PTC patients were dichotomized and compared with respect to clinical parameters of PTC. Genetic data were analyzed using Helixtree, SNPAnalyzer, SNPStats. Multivariate logistic regression analysis was fulfilled to evaluate the genetic effect with adjustment for age and sex.

Results

SNP (rs925255) in FOSL-2 showed a significant association (codominant 1 model [G/G vs. A/G]: odds ratio [OR], 0.531, 95% confidence interval [CI], 0.293 to 0.96, P=0.036; dominant model: OR, 0.50, 95% CI, 0.28 to 0.89, P=0.015) with PTC. The frequency of allele G in rs925255 was also significantly associated with PTC (OR, 0.59; 95% CI, 0.34 to 0.91; P=0.02). But we fail to prove significant association between this polymorphism (rs925255) and clinico-pathological parameters.

Conclusion

Our findings suggest that the rs925255 SNP and its allele G show significant association with the PTC in Korean population.

Genetic features of thyroid hormone receptors

Thyroid hormone receptors (TR) are prototypes of nuclear transcription factors that regulate the expression of target genes. These receptors play an important role in many physiological processes. Moreover, a dysfunction of these proteins is often implicated in several human diseases and malignancies. Here we report genetic variations and alterations of the TRs that have been described in the literature as well as their potential role in the development of some human diseases including cancers. The functional effects of some mutations and polymorphisms in TRs on disease susceptibility, especially on cancer risk, are now established. Therefore, further investigations are needed in order to use these receptors as therapeutic targets or as biological markers to decide on appropriate forms of treatment.

Interleukin 22 polymorphisms and papillary thyroid cancer

BACKGROUND

IL22RA1 (Interleukin 22 receptor-alpha 1), a member of the class II cytokine receptor family, mediates diverse biologic activities and appears to be important in pathogen defense, wound healing, and tissue reorganization. Polymorphisms in genes encoding inflammatory cytokines are associated with increased cancer risk.

AIM

The aim of this study was to evaluate the association between the single nucleotide polymorphisms (SNP) in the IL22 and IL22RA1 and papillary thyroid cancer (PTC), and to assess the relationship between the SNP in the IL22 and IL22RA1 and the clinical parameters of PTC.

MATERIAL AND METHODS

Study enrolled experimental group of 94 PTC patients and 213 controls. PTC patients were grouped and compared for clinical PTC parameters. One promoter SNP of IL22, -429C/T (rs2227485), and one SNP of IL22RA1, Arg518Gly (rs3795299) were analyzed using direct sequencing. Genetic data were analyzed using Helixtree, SNPAnalyzer Pro, SNPStats, and Haploview.

RESULTS

A SNP in IL22 (rs2227485) was significantly associated with PTC (codominant2 model [C/C vs T/T], odds ratio (OR) 2.39, 95% confidence interval (CI) 1.21-4.71, p=0.012; dominant model, OR 1.89, 95% CI 1.08-3.31, p=0.022). The allele T frequency of rs2227485 in IL22 was also associated with PTC (OR 1.59, 95% CI 1.13-2.25, p=0.009). According to clinical parameters, rs2227485 of IL22 was associated with number of cancers (dominant model, OR 3.03, 95% CI 1.02-9.01, p=0.035). By haplotype analysis, TG was associated with PTC (codominant model, OR 1.52, 95% CI 1.07-2.16, p=0.019; dominant model, OR 1.91, 95% CI 1.13- 3.24, p=0.015). Genotype and allele analysis of rs3795299 in IL22RA1 showed no significant differences between PTC patients and controls.

CONCLUSION

The rs2227485 SNP in IL22 might be associated with the risk and the multifocality of PTC.

TPO genetic variants and risk of differentiated thyroid carcinoma in two European populations

Thyroid cancer risk involves the interaction of genetic and environmental factors. The thyroperoxidase (TPO) has a key role in the iodine metabolism, being essential for the thyroid function. Mutations in the TPO gene are common in congenital hypothyroidism, and there are also signs of the implication of TPO in thyroid cancer. We performed a case-control association study of genetic variants in TPO and differentiated thyroid carcinoma (DTC) in 1,586 DTC patients and 1,769 controls including two European populations (Italy: 1,190 DTC and 1,290 controls; Spain: 396 DTC and 479 controls). Multivariate logistic regression analyses were performed separately for each population and each single-nucleotide polymorphism (SNP). From the three studied polymorphisms, significant associations were detected between DTC and rs2048722 and rs732609 in both populations (p < 0.05). In the Italian population, both SNPs showed a negative association (rs2048722, odds ratio [OR] = 0.79, 95% confidence interval [CI] = 0.63-1.00, p = 0.045; rs732609, OR = 0.72, 95% CI = 0.55-0.94, p = 0.016), whereas in the Spanish population, these SNPs showed a positive association (rs2048722, OR = 1.39, 95% CI = 1.03-1.89, p = 0.033; rs732609, OR = 1.41, 95% CI = 1.06-1.87, p = 0.018). The corresponding associations for papillary or follicular thyroid cancer were similar to those for all DTC, within population. No association was detected for the third TPO polymorphism in the Italian and the Spanish populations. Our results, for the first time, point to TPO as a gene involved in the risk of DTC, and suggest the importance of interactions between TPO variants and other unidentified population-specific factors in determining thyroid cancer risk.

Common genetic variants in pituitary-thyroid axis genes and the risk of differentiated thyroid cancer

Thyroid hormone receptors, THRA and THRB, together with the TSH receptor, TSHR, are key regulators of thyroid function. Alterations in the genes of these receptors (THRA, THRB and TSHR) have been related to thyroid diseases, including thyroid cancer. Moreover, there is evidence suggesting that predisposition to differentiated thyroid cancer (DTC) is related to common genetic variants with low penetrance that interact with each other and with environmental factors. In this study, we investigated the association of single nucleotide polymorphisms (SNPs) in the THRA (one SNP), THRB (three SNPs) and TSHR (two SNPs) genes with DTC risk. A case-control association study was conducted with 398 patients with sporadic DTC and 479 healthy controls from a Spanish population. Among the polymorphisms studied, only THRA-rs939348 was found to be associated with an increased risk of DTC (recessive model, odds ratio=1.80, 95% confidence interval=1.03-3.14, P=0.037). Gene-gene interaction analysis using the genotype data of this study together with our previous genotype data on TG and TRHR indicated a combined effect of the pairwises: THRB-TG (P interaction=0.014, THRB-rs3752874 with TG-rs2076740; P interaction=0.099, THRB-rs844107 with TG-rs2076740) and THRB-TRHR (P interaction=0.0024, THRB-rs3752874 with TRHR-rs4129682) for DTC risk in a Spanish population. Our results confirm that THRA is a risk factor for DTC, and we show for the first time the combined effect of THRB and TG or TRHR on DTC susceptibility, supporting the importance of gene-gene interaction in thyroid cancer risk.

Common genetic variants in sex hormone pathway genes and papillary thyroid cancer risk

BACKGROUND

Hormonal differences are hypothesized to contribute to the approximately ≥2-fold higher thyroid cancer incidence rates among women compared with men worldwide. Although thyroid cancer cells express estrogen receptors and estrogen has a proliferative effect on papillary thyroid cancer (PTC) cells in vitro, epidemiologic studies have not found clear associations between thyroid cancer and female hormonal factors. We hypothesized that polymorphic variation in hormone pathway genes is associated with the risk of developing papillary thyroid cancer.

METHODS

We evaluated the association between PTC and 1151 tag single nucleotide polymorphisms (SNPs) in 58 candidate gene regions involved in sex hormone synthesis and metabolism, gonadotropins, and prolactin in a case-control study of 344 PTC cases and 452 controls, frequency matched on age and sex. Odds ratios and p-values for the linear trend for the association between each SNP genotype and PTC risk were estimated using unconditional logistic regression. SNPs in the same gene region or pathway were aggregated using adaptive rank-truncated product methods to obtain gene region-specific or pathway-specific p-values. To account for multiple comparisons, we applied the false discovery rate method.

RESULTS

Seven SNPs had p-values for linear trend <0.01, including four in the CYP19A1 gene, but none of the SNPs remained significant after correction for multiple comparisons. Results were similar when restricting the dataset to women. p-values for examined gene regions and for all genes combined were ≥0.09.

CONCLUSIONS

Based on these results, SNPs in selected hormone pathway genes do not appear to be strongly related to PTC risk. This observation is in accord with the lack of consistent associations between hormonal factors and PTC risk in epidemiologic studies.

A GA microsatellite in the Fli1 promoter modulates gene expression and is associated with systemic lupus erythematosus patients without nephritis

INTRODUCTION

The transcription factor Fli1 is implicated in the pathogenesis of systemic lupus erythematosus (SLE). Recently, a GA(n) polymorphic microsatellite was characterized in the mouse Fli1 promoter that modulates promoter activity and is truncated in two lupus mouse models compared to non-autoimmune prone mice. In this work, we characterize a homologous GA(n) microsatellite in the human Fli1 promoter. The purpose of this study is to determine the effect of the microsatellite length on Fli1 promoter activity in vitro and to determine if the length of the GA(n) microsatellite is associated with SLE and/or specific disease characteristics.

METHODS

Constructs with variable lengths of the GA(n) microsatellite in the Fli1 promoter were generated and analyzed in promoter/reporter (P/R) assays in a human T cell line. Using three SLE patient cohorts and matched controls, microsatellite length was measured and association with the presence of disease and the occurrence of specific disease manifestations was assessed.

RESULTS

P/R assays demonstrated that the presence of a shorter microsatellite resulted in higher Fli1 promoter activity. A significant association was observed in the lupus cohort SLE in Gullah Health (SLEIGH) between the GA(26) base pair allele and absence of nephritis.

CONCLUSIONS

This study demonstrates that a GA(n) microsatellite in the human Fli1 promoter is highly polymorphic. The length of the microsatellite is inversely correlated to Fli1 promoter activity in a human T cell line. Although no association between microsatellite length and lupus was observed, an association between a specific microsatellite length and patients without nephritis in the SLEIGH cohort was observed.

Thyroid cancer gender disparity

Cancer gender disparity in incidence, disease aggressiveness and prognosis has been observed in a variety of cancers. Thyroid cancer is one of the fastest growing cancer diagnoses worldwide. It is 2.9-times more common in women than men. The less aggressive histologic subtypes of thyroid cancer are more common in women, whereas the more aggressive histologic subtypes have similar gender distribution. The gender disparity in incidence, aggressiveness and prognosis is well established for thyroid cancer but the cause of the disparity is poorly understood. The aim of this article is to evaluate the current evidence on the cause of thyroid cancer gender disparity. Dietary and environmental factors do not appear to have a significant role in thyroid cancer gender disparity. Common somatic mutations in BRAF, rearranged in transformation/papillary thyroid carcinomas (RET/PTC) and neurotrophin receptor-tyrosine kinase (NTRK) also do not account for the gender disparity in thyroid cancer. While reproductive factors would seem a logical hypothesis to account for the gender disparity, there appears to be no conclusive effect on the risk of developing thyroid cancer. Recent studies on estrogen receptor status in thyroid cancer show a difference in the receptor subtypes expressed based on the histology of thyroid cancer. Moreover, the response to estrogen is dependent on the specific estrogen receptor expressed in thyroid cancer cells. However, what determines the tumor-specific sex hormone receptor expression is unclear. No established molecular factors appear to explain gender differences in thyroid cancer. Therefore, the application of high-throughput genomic and proteomic approaches to the study of thyroid cancer gender disparity could be helpful for better understanding the molecular basis for gender differences in thyroid and other cancers.

Genetic polymorphisms in the EGFR (R521K) and estrogen receptor (T594T) genes, EGFR and ErbB-2 protein expression, and breast cancer risk in Tunisia

We evaluated the association of epidermal growth factor receptor (EGFR) 142285G>A (R521K) and estrogen receptor alpha (ESR1) 2014G>A (T594T) single nucleotide polymorphisms with breast cancer risk and prognosis in Tunisian patients. EGFR 142285G>A and ESR1 2014G>A were genotyped in a sample of 148 Tunisian breast cancer patients and 303 controls using PCR-RFLP method. Immunohistochemitsry was used to evaluate the expression levels of EGFR, HER2, ESR1, progesterone receptor and BCL2 in tumors. We found no evidence for an association between EGFR R521K polymorphism and breast cancer risk. However, we found that the homozygous GG (Arg) genotype was more prevalent in patients with lymph node metastasis (P = .03) and high grade tumors (P = .011). The ESR1 2014G allele showed significant association with breast cancer risk (P = .025). The GG genotype was associated with HER2 overexpression and this association withstood univariate and multivariate analyses (P = .009; P = .021, resp.). These data suggest that the R521K might be a prognostic factor, because it correlates with both tumor grade and nodule status. The higher expression of HER2 in ESR1 T594T GG patients suggests the possibility that ESR1 gene polymorphisms accompanied by HER2 expression might influence the pathogenesis of breast cancers.