Impact of molecular alterations of BRAF in the pathogenesis of thyroid cancer

Role of Genetic Testing in the Management of Indeterminate Thyroid Nodules in the Indian Setting

The increased detection of thyroid nodules in the human population has led to an increase in the number of thyroid surgeries without an improvement in survival outcomes. Though the choice for surgery is straightforward in malignant thyroid nodules, the decision is far more complex in those nodules that get categorized into indeterminate thyroid nodules (ITN) by fine needle aspiration. Therefore, there is a pressing need to develop a tool that will aid in decision-making among the ITN. In this context, the development of various molecular testing (MT) panels has helped to confirm or rule out malignancy, reducing unnecessary surgeries and potentially guiding the extent of surgery as well. Currently, such tests are widely used among the Western population but these MT panels are not used by the South Asian population because of non-availability of validated panels and the high cost involved. There is a need to develop a suitable panel which is population-specific and validate the same. In this review, we would focus on current trends in the management of ITN among the South Asian population and how to develop a novel MT panel which is cost-effective, with high diagnostic accuracy obviating the need for expensive panels that already exist.

Biomarker Discovery for Early Diagnosis of Papillary Thyroid Carcinoma Using High-Throughput Enhanced Quantitative Plasma Proteomics

The incidence of thyroid cancer (TC) has been increasing over the last 50 years worldwide. A higher rate of overdiagnosis in indolent thyroid lesions has resulted in unnecessary treatment. An accurate detection of TC at an early stage is highly demanded. We aim to develop an enhanced isobaric labeling-based high-throughput plasma quantitative proteomics to identify biomarkers in a discovery cohort. Selected candidates were tested by enzyme-linked immunosorbent assay (ELISA) in the training cohort and validation cohort. In total, 1063 proteins were quantified, and 129 proteins were differentially expressed between patients and healthy subjects. Serum levels of ISG15 and PLXNB2 were significantly elevated in patients with papillary thyroid cancer (PTC) or thyroid adenoma, compared to healthy subjects (p < 0.001) and patients with nodular goiter (p < 0.001). Receiver operating characteristic (ROC) analysis of combined markers (ISG15 and PLXNB2) significantly distinguished PTC from healthy control (HC) subjects. Similar differentiations were also found between thyroid adenoma and HC subjects. Notably, this combined marker could distinguish stage-I PTC from HC subjects (area under the curve (AUC) = 0.872). Our results revealed that ISG15 and PLXNB2 are independent diagnostic biomarkers for PTC and thyroid adenoma, showing a promising value for the early detection of PTC.

Thyroid Cancer Diagnostics Related to Occupational and Environmental Risk Factors: An Integrated Risk Assessment Approach

There are still many questions remaining about the etiopathogenesis of thyroid cancer, the most common type of endocrine neoplasia. Numerous occupational and environmental exposures have been shown to represent important risk factors that increase its incidence. Updated information about thyroid cancer diagnostics related to occupational and environmental risk factors is reviewed here, considering an integrated risk assessment approach; new data concerning thyroid cancer etiology and pathogenesis mechanisms, diagnostic biomarkers and methodologies, and risk factors involved in its pathogenesis are presented. A special emphasis is dedicated to specific occupational risk factors and to the association between environmental risk agents and thyroid cancer development. The occupational environment is taken into consideration, i.e., the current workplace and previous jobs, as well as data regarding risk factors, e.g., age, gender, family history, lifestyle, use of chemicals, or radiation exposure outside the workplace. Finally, an integrative approach is presented, underlying the need for an accurate Risk Assessment Matrix based on a systematic questionnaire. We propose a complex experimental design that contains different inclusion and exclusion criteria for patient groups, detailed working protocols for achieving coherent and sustainable, well-defined research stages from sample collection to the identification of biomarkers, with correlations between specific oncometabolites integrated into the Risk Assessment Matrix.

Variations in MAP kinase gladiators and risk of differentiated thyroid carcinoma

Thyroid carcinoma (TC) accounts for ~2.1% of newly diagnosed cancer cases. Mutations in KRAS, HRAS, NRAS and BRAF are primary participants in the development and progression of various types of malignancy, including differentiated TC (DTC). Therefore, the present prospective cohort study aimed to screen patients with DTC for variations in RAS gene family and BRAF gene. Exon 1 and 2 of KRAS, HRAS, NRAS and exon 15 of BRAF gene were screened for hotspot mutations in 72 thyroid tumor and adjacent normal tissue samples using di-deoxy Sanger sequencing. HRAS T81C mutation was found in 21% (15 of 72) of DTC tissue samples, therefore this mutation was investigated in blood samples from patients with DTC and controls as a genetic polymorphism. In addition, HRAS T81C genotypes were determined in 180 patients with DTC and 220 healthy controls by performing restriction fragment length polymorphism. BRAF^V600E mutation was confined to classical variant of papillary thyoid cancer (CPTC; 44.4%) and was significantly associated with multifocality and lymph node (LN) metastasis. No mutation was found in exons 1 and 2 of KRAS and NRAS and exon 2 of HRAS genes, however, mutation was detected in exon 1 of HRAS gene (codon 27) at nucleotide position 81 in 21% (15 of 72) of DTC tumor tissue samples. Furthermore, HRAS T81C single nucleotide polymorphism was significantly associated with the risk of DTC with variant genotypes more frequently detected in cases compared with controls (P≤0.05). Moreover, frequency of variant genotypes (TC+CC) was significantly higher among DTC cases with no history of smoking, males, greater age, multifocality and LN metatasis compared with healthy controls (P<0.05). BRAF^V600E mutation was primarily present in CPTC and associated with an aggressive tumor phenotype but mutations in RAS gene family were not present in patients with DTC. HRAS T81C polymorphism may be involved in the etiopathogenesis of DTC in a Pakistani cohort. Furthermore, testing for the BRAF^V600E mutation may be useful for selecting initial therapy and follow-up monitoring.

circZFR regulates thyroid cancer progression by the miR-16/MAPK1 axis

Previous studies have identified the dysregulation of various circRNAs in many types of human cancers including thyroid cancer (TC). Circular RNA ZFR (circZFR) serves as an oncogenic circRNA in TC. However, the detailed molecular mechanism of circZFR in TC progression remains to be further explored. CircZFR and miR-16 expressions in TC cells were analyzed through qRT-PCR. Cell viability, invasion, and apoptosis were detected using CCK-8, transwell invasion assay, and flow cytometry analysis, respectively. The relationship between circZFR and miR-16 was explored using luciferase reporter assay, RNA pull-down assay, and qRT-PCR. The relationship between miR-16 and mitogen-activated protein kinase 1 (MAPK1) was explored using luciferase reporter assay and western blot analysis. Results showed that circZFR was upregulated and miR-16 was downregulated in TC cells. CircZFR knockdown inhibited the viability and invasion and induced apoptosis in TC cells. CircZFR inhibited miR-16 expression by sponging miR-16 and miR-16 repressed MAPK1 expression by targeting MAPK1. Moreover, circZFR positively regulated MAPK1 expression in TC cells by serving as a ceRNA of miR-16. Mechanistically, circZFR knockdown-induced inhibition of cell viability and invasion and promotion of apoptosis were overturned after miR-16 downregulation and promotion of MAPK1. Collectively, circZFR knockdown retarded TC progression by sponging miR-16 and modulating MAPK1 expression.

BRAFV600E hot spot mutation in thyroid carcinomas: first Moroccan experience from a single-institution retrospective study

BACKGROUND

The incidence of thyroid cancer is increasing worldwide at an alarming rate. BRAF^V600E mutation is described to be associated with a worse prognostic of thyroid carcinomas, as well as extrathyroidal invasion and increased mortality.

OBJECTIVE

To our knowledge, there are no reported studies neither from Morocco nor from other Maghreb countries regarding the prevalence of BRAF^V600E mutation in thyroid carcinomas. Here we aim to evaluate the frequency of BRAF^V600E oncogene in Moroccan thyroid carcinomas.

METHODS

In this Single-Institution retrospective study realized in the Anatomic Pathology and Histology Service in the Military Hospital of Instruction Mohammed V 'HMIMV' in Rabat, we report, using direct genomic sequencing, the assessment of BRAF^V600E in 37 thyroid tumors.

RESULTS

We detected BRAF^V600E mutation exclusively in Papillary Thyroid Carcinomas 'PTC' with a prevalence of 28% (8 PTC out 29 PTC). Like international trends, Papillary Thyroid Carcinomas 'PTC' is more frequent than Follicular Thyroid Carcinomas 'FTC' and Anaplastic Thyroid Carcinomas 'ATC' (29 PTC, 7 FTC and 1 ATC).

CONCLUSION

Our finding gives to the international community the first estimated incidence of this oncogene in Morocco showing that this prevalence falls within the range of international trends (30% to 90%) reported in distinct worldwide geographic regions.

Prevalence of BRAFV600E mutation in Asian series of papillary thyroid carcinoma-a contemporary systematic review

Papillary thyroid carcinoma (PTC), the most common malignancy of the endocrine system, is frequently driven by BRAFV600E mutation, which was reported in 35-60% cases in Western series. Numerous studies have recently emerged from Asian countries and regions; however sufficient summary is lacking to date. BRAF mutation serves as a diagnostic and prognostic tool in thyroid cancer, therefore establishing a rate of BRAF on the national scale could be of practical significance. We performed systematic reviews of available literature to investigate the prevalence of BRAF mutation in series of PTC from various Asian countries and regions. Out of the total 3,966 reports identified via initial screening, 138 studies encompassing over 40,000 PTCs were included for the final analysis. A vast majority (90.2%) of PTCs with known BRAF status were from East Asia, including China, South Korea, and Japan, with BRAF mutation rates of 71.2%, 75.5%, and 70.6%, respectively. Less abundant Indian and Saudi Arabian series found 45.6% and 46.3% prevalence of BRAFV600E in PTC, respectively. Much limited evidence was available from Thailand, Iran, Kazakhstan, Taiwan, Singapore, Indonesia, Hong Kong, Philippines, Vietnam, Iraq, and Myanmar. No relevant publications were found from other highly populated countries, such as Pakistan, Bangladesh, and Malaysia. After grouping by geographic region, we found that the highest rate of BRAFV600E was reported in the PTC series from East Asia (76.4%). Much lower rate (45-48%) was seen in PTC cohorts from South Asia, Central Asia, and the Middle East while the Southeast Asian series were in between (57%). Further subgroup analysis revealed that studies employing fresh frozen tissue and fine-needle aspirates showed higher rates of BRAF compared to those used formalin-fixed paraffin-embedded tissues. We found that the PTC series enrolled patients' cohorts after 2010 demonstrated a higher rate of BRAF compared to the earlier series. Finally, pediatric PTCs had lower BRAF prevalence compared to the baseline rate for the country. In conclusion, despite considerable among and within countries heterogeneity, the Asian PTC series showed a higher prevalence of BRAFV600E mutation than that in Western series. Causes of geographic heterogeneity, whether genuine (etiology, genetics) or methodology-related should be further investigated.

LncRNA NBR2 Inhibits the Malignancy of Thyroid Cancer, Associated With Enhancing the AMPK Signaling

Long non-coding RNA NBR2 is a transcript of the neighbor of BRCA1 gene 2 and can regulate tumor development. However, there is little information on the role of NBR2 in the progression of thyroid cancers (TC). Here, we show that NBR2 expression is down-regulated in TC tissues and associated with histologic subtypes of TC. NBR2 expression was variably reduced in different TC cells. While NBR2 silencing significantly enhanced the malignancy of BCPAP cells by increasing cell proliferation, clonogenicity, wound healing, and invasion as well as tumor growth in vivo, and decreasing spontaneous apoptosis, NBR2 over-expression had opposite effects in BHT101 cells. Furthermore, treatment with A-769662 (a specific AMPK activator), like NBR2 over-expression, significantly attenuated the malignancy of BHT101 cells while treatment with Compound C (a specific AMPK inhibitor) significantly rescued that NBR2-reduced malignancy of BHT101 cells. In comparison with non-tumor thyroid epithelial Nthy-ori 3-1 cells, obviously increased GLUT-1 expression, but decreased AMPK and ACC phosphorylation were detected in TC cells. While NBR2 silencing further enhanced GLUT-1 expression and reduced AMPK and ACC phosphorylation as well as the EMT process in BCPAP cells. NBR2 over-expression also had opposite effects in BHT101 cells. Similar patterns of GLUT-1 expression and AMPK and ACC phosphorylation were detected in the different types of xenograft TC tumors in vivo. Therefore, such data indicated that NBR2 acted as a tumor suppressor of thyroid cancers associated with enhancing the AMPK signaling and NBR2 may be a potential biomarker and therapeutic target for thyroid cancers.

MicroRNA-26a-5p inhibits proliferation, invasion and metastasis by repressing the expression of Wnt5a in papillary thyroid carcinoma

Background

Thyroid cancer (TC) is considered as the fastest growing malignancy in the human endocrine system, particularly papillary thyroid cancer (PTC). MicroRNAs (miRs) serve as a role in promoting or suppressing tumors in various types of malignant tumor including PTC. This study aims to explore whether microRNA-26a-5p (miR-26a-5p) could affect the proliferation, invasion and metastasis ability of PTC cells by regulating Wnt5a.

Materials and methods

The expression of miR-26a-5p was examined by qRT-PCR in PTC tissue samples (58 cases, mean age 53 years old) and PTC cell lines (K1 and BCPAP). Cell proliferation, invasion and migration were tested with CCK8 assay, colony formation assay, transwell invasion assay and wound healing assay, respectively. Luciferase reporting experiment was used to verify that Wnt5a is a molecular target of miR-26a-5p. The relationship between miR-26a-5p and Wnt5a was analyzed by qRT-PCR and Western blot and was further proved by Pearson's correlation analysis. Animal (24 nude mice) experiments were used to demonstrate that miR-26a-5p inhibits tumor growth by targeting Wnt5a.

Results

The expression of miR-26a-5p declined in PTC tissues (P<0.01). The expression of miR-26a-5 was also significantly down-regulated in PTC tissues with advanced TNM stages (P<0.01) and lymph node metastasis (P<0.01) compared with normal thyroid tissues. Compared with normal human thyroid cell line Nthy-ori 3-1, the expression of miR-26a-5p in K1 cells and BCPAP cells were nearly 4.02-fold (P<0.01) and 2.51-fold (P<0.01) reduced. Up regulation of miR-26a-5p inhibited proliferation, colony formation, invasion and migration of PTC cells. MiR-26a-5p negatively regulated Wnt5a expression (r=-0.887, P<0.01), yet Wnt5a overexpression reversed the tumor-suppressive effect of miR-26a-5p in PTC. Animal experiments further verified that miR-26a-5p inhibited PTC growth by targeting Wnt5a.

Conclusion

Overexpression of miR-26a-5p depresses proliferation, invasion, metastasis of PTC via Wnt5a. Therefore, miR-26a-5p may represent a potentially effective target gene for PTC.

RET/PTC Gene Rearrangements in Thyroid Carcinogenesis: Assessment and Clinico-Pathological Correlations

Rearranged during transfection (RET) is a proto oncogene implicated in thyroid carcinogenesis of papillary type (PTC). The RET proto-oncogene in PTC is constitutively activated by fusion of its tyrosine kinase domain with the 5 ´region of another gene thereby generating chimeric products collectively named RET/PTCs. RET/PTC1 and RET/PTC3 are best characterized among all RET/PTC rearrangements. Kashmir valley has witnessed an alarming increase in thyroid cancer incidence in young women. Therefore, we investigated the occurrence of RET/PTC 1 & 3 rearrangements by semi quantitative and qPCR in thyroid cancer patients (n = 48) of Kashmiri population and interrelated results with various clinicopathological characteristics. We observed that all the RET/PTC rearrangements were confined to PTC cases (10/40). Presence of RET/PTC rearrangement significantly correlated with gender, elevated TSH levels and lymph node metastasis. Overall, our study advocates that RET/PTC3 rearrangement is a frequent event in the carcinogenesis of thyroid gland in Kashmiri population although a study with a larger sample size is needed to get a clear scenario.

Presurgical Screening of Fine Needle Aspirates from Thyroid Nodules for BRAF Mutations: A Prospective Single Center Experience

OBJECTIVE

Analysis of BRAF V600E mutation in thyroid fine needle aspirates (FNA) is an important adjunct to cytology, particularly among FNA placed in the "indeterminate category." However, such a prospective evaluation of FNA obtained from patients with thyroid nodules has been lacking from India.

MATERIAL AND METHODS

FNA from 277 patients were prospectively evaluated for BRAF mutations by Sanger's sequencing. A subset of 30 samples was also analyzed by pyrosequencing using the PyroMark BRAF mutation kit.

RESULTS

Overall, 27.2% of FNA samples were positive for mutations including 19 (35.8%) of the 53 histologically confirmed papillary thyroid carcinoma (PTC), 2 of the 25 follicular variants of PTC, and 1 anaplastic thyroid carcinoma. Only 1 (2.7%) of the 37 samples in the atypia of undetermined significance/follicular lesion of unknown significance category was BRAF positive. The sensitivity of cytology improved marginally from 67.1% to 68.3% when evaluated with BRAF. Further, a comparison of the clinicopathological characteristics of BRAF positive and negative PTCs showed a significant association (P = 0.05) between lymph node metastasis and BRAF positivity.

CONCLUSION

BRAF positivity was lower than that reported from East Asia with the test being useful in confirming malignancies among the suspicious of malignancy and malignant categories.

Mutational Profile of Papillary Thyroid Carcinoma in an Endemic Goiter Region of North India

INTRODUCTION

Mitogen activated protein kinase (MAPK) pathway is regularly altered in papillary thyroid carcinomas (PTCs). Serine/threonine-protein kinase B-Raf (BRAF) V600E mutations were observed very frequently in PTC along with less frequent rat sarcoma (RAS) and rearranged during transfection (RET) gene, also known as RET/PTC translocation. The present study aimed to analyze the mutational profile of PTCs from an endemic Goiter area of North India.

METHODOLOGY

Tissues from 109 PTC patients were used to isolate DNA and RNA. BRAF V600E was detected by restriction fragment length polymorphism-polymerase chain reaction (PCR). RAS mutations were screened by using Sanger's sequencing method. RET/PTC rearrangements were analyzed by real-time PCR.

RESULTS

BRAF V600E mutation was detected in 51.38% (56/109) of PTCs, whereas RAS mutations were less frequent. No RET/PTC rearrangements were observed. BRAF V600E was found to be associated with the aggressive clinicopathological features such as lymph node metastasis, distant metastasis, higher tumor-node-metastasis stages, and high-risk groups.

CONCLUSION

The prevalence of BRAF V600E is high in patients from Indian Subcontinent and found to be associated with aggressive features of PTC. Concomitant mutations of BRAF V600E and RAS mutations impart more aggressiveness to PTCs.

MicroRNA-625-3p promotes the proliferation, migration and invasion of thyroid cancer cells by up-regulating astrocyte elevated gene 1

BACKGROUND

Thyroid cancer is the most common malignancy in human endocrine system. This study aimed to investigate the effects of microRNA-625-3p (miR-625-3p) on thyroid cancer cell proliferation, migration, invasion and apoptosis, as well as underlying potential mechanism.

METHODS

The relative expressions of miR-625-3p in tumor tissues and adjacent normal tissues of 20 patients with papillary thyroid cancer (PTC) were assessed using qRT-PCR. Cell transfection was used to up-regulate or down-regulate the expressions of miR-625-3p in thyroid cancer SW579 and TPC-1 cells. Effects of miR-625-3p overexpression or suppression on SW579 and TPC-1 cell viability, migration, invasion and apoptosis were detected respectively. The regulatory effect of miR-625-3p on astrocyte elevated gene 1 (AEG-1) expression was also analyzed. Then, the roles of AEG-1 in SW579 and TPC-1 cell proliferation, migration, invasion and apoptosis, as well as Wnt/β-catenin and c-Jun N-terminal kinase (JNK) pathways activation, were evaluated.

RESULTS

miR-625-3p had high expressions in tumor tissues, compared to adjacent normal tissues. Overexpression of miR-625-3p significantly promoted SW579 and TPC-1 cell proliferation, migration and invasion but had no influence on cell apoptosis. Knockdown of miR-625-3p had opposite effects, but induced cell apoptosis. AEG-1 was up-regulated by miR-625-3p overexpression and participated in the effects of miR-625-3p on SW-579 and TPC-1 cells. In addition, overexpression of AEG-1 induced the activation of Wnt/β-catenin and JNK pathways in SW579 and TPC-1 cells.

CONCLUSION

miR-625-3p promoted proliferation, migration and invasion of thyroid cancer cells by enhancing the expression of AEG-1 and activating downstream Wnt/β-catenin and JNK pathways.

The correlations between DNA methylation and polymorphisms in the promoter region of the human telomerase reverse transcriptase (hTERT) gene with postoperative recurrence in patients with thyroid carcinoma (TC)

Background

This study aims at exploring the correlations between DNA methylation and polymorphisms in the promoter region of the human telomerase reverse transcriptase (hTERT) gene and postoperative recurrence in patients with thyroid carcinoma (TC).

Methods

A total of 312 patients diagnosed with TC were chosen for the study and categorized into recurrence (n = 75) and non-recurrence (n = 237) groups. The hTERT rs2736100 and rs2736098 polymorphisms were detected by performing polymerase chain reaction-restriction fragment length polymorphism. DNA methylation in the promoter region of hTERT gene was evaluated by pyrosequencing. A telephonic and/or outpatient follow-up was conducted for all patients. The correlations of DNA methylation and polymorphisms in the promoter region of hTERT with postoperative recurrence of TC patients underwent analysis.

Results

The patient in the recurrence group showed evidently different pathological types and tumor stages in comparison to the non-recurrence group. The GG genotype of hTERT rs2736100 might increase the recurrence risk of TC patients. No correlations between hTERT rs2736098 polymorphisms and recurrence risk were observed. Compared to the TT + TG genotype frequency, the rs2736100 GG genotype frequency increased in patients without multicentricity, patients with extrathyroidal invasion, patients with lymph node metastasis, patients with undifferentiated carcinoma, and patients in the III + IV stage. The recurrence group showed significantly higher DNA methylation level compared to the non-recurrence group. The DNA methylation level was closely associated to tumor stage and lymph node metastasis of TC patients in the recurrence group.

Conclusions

The DNA methylation and rs2736100 polymorphisms in the promoter region of hTERT gene might be in correlation to postoperative recurrence of TC patients.

Associations between BRAF(V600E) and prognostic factors and poor outcomes in papillary thyroid carcinoma: a meta-analysis

Background

The objective of this study is to perform a meta-analysis to evaluate the associations between the BRAF^V600E mutation status and aggressive clinicopathological features and poor prognostic factors in papillary thyroid cancer.

Methods

A literature search was performed within the PubMed, MEDLINE, Web of Science databases, and EMBASE databases using the Medical Subject Headings and keywords from January 2003 to July 2015. Individual study-specific odds ratios and confidence intervals were calculated, as were the Mantel-Haenszel pooled odds ratios for the combined studies.

Results

Sixty-three studies of 20,764 patients were included in the final analysis. Compared with wild-type BRAF, the BRAF^V600E mutation was associated with aggressive clinicopathological factors, including extrathyroidal extension, higher TNM stage, lymph node metastasis, and recurrence, and was associated with reduced overall survival; however, there was no significant association between the presence of BRAF mutation and distant metastasis.

Conclusions

BRAF mutations are closely associated with aggressive clinicopathological characteristics and poorer prognosis in papillary thyroid cancer. Accordingly, aggressive treatment should be considered for papillary thyroid cancer patients with BRAF mutation.

Clinical Manifestations and Gene Expression in Patients with Conventional Papillary Thyroid Carcinoma Carrying the BRAF(V600E) Mutation and BRAF Pseudogene

BACKGROUND

The association of BRAF(V600E) with the clinical manifestations of papillary thyroid carcinoma (PTC) remains controversial. Recent studies have shown that the BRAF pseudogene can activate the MAPK pathway and induce tumorigenesis. This study investigated the association of BRAF(V600E), the BRAF pseudogene, and their mRNA levels with clinical features and thyroid-specific gene expression in conventional PTCs.

MATERIALS AND METHODS

A total of 78 specimens were collected from patients with conventional PTCs. RNA was isolated, and quantitative polymerase chain reaction was used to measure the mRNA levels of BRAF, the BRAF pseudogene, and thyroid-specific and tumor-related genes. Immunohistochemical (IHC) staining of BRAF, ERK, sodium-iodide symporter (NIS), thyrotropin receptor, glucose transporter 1, and Ki67 was also performed.

RESULTS

BRAF(V600E) and the BRAF pseudogene were detected in 73.0% (57/78) and 91.7% (44/48), respectively, of the conventional PTCs. The presence of BRAF(V600E) was not associated with the multiple clinical features assessed or the recurrence rate during 76.9 ± 47.2 months of follow-up. Neither was it associated with IHC staining or tumor-related/thyroid-specific gene expression, except for decreased NIS gene expression. The BRAF pseudogene was not associated with clinical characteristics or thyroid-specific gene expression, except for decreased decoy receptor 3 (DCR3) expression. High BRAF mRNA levels were associated with bilateral and multifocal lesions, and BRAF-pseudogene mRNA levels were positively correlated with BRAF mRNA levels (r = 0.415, p = 0.009).

CONCLUSION

These results do not support the use of the BRAF(V600E) mutation as a prognostic marker of conventional PTC. However, the association of high BRAF mRNA levels with more advanced clinical features suggests that BRAF mRNA levels might be a more useful clinical marker of PTCs, independent of the BRAF(V600E) mutation status. The correlation between BRAF-pseudogene mRNA levels and BRAF mRNA levels in PTCs is in agreement with the hypothesis that the BRAF pseudogene regulates BRAF expression during tumorigenesis by acting as competitive noncoding RNA. However, additional studies with larger sample sizes are required to confirm these findings.

Correlation between polymorphisms of BRAF gene and papillary thyroid carcinoma

BACKGROUND

Papillary thyroid carcinoma (PTC), which accounts for 80% of all thyroid cancers, has an increasing incidence over these years. Single nucleotide polymorphisms (SNPs) of BRAF were considered to be one of well-established risk factors leading to development of PTC. The aim of this study was to investigate whether the common mutations of BRAF could elevate significantly the risk of PTC in a Chinese population.

METHODS

Four SNPs (rs11762469, rs17623204, rs1267636 and rs3748093) of BRAF were selected through our filter by Haploview 4.2 software with HapMap databases. We used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to genotype the four SNPs in blood samples of 618 subjects (206 patients with PTC and 412 healthy controls). The correlation between BRAF polymorphisms and PTC risk was assessed using student t-test and chi-square test.

RESULTS

The results showed that mutation in rs3748093 was significantly associated with an increased risk of PTC in allele model (A allele vs. T allele, OR = 1·68, 95% CI = 1·16-2·43, P = 0·006), dominant model (TA + AA vs TT, OR = 1·64, 95% CI = 1·08-2·48, P = 0·019) and homozygote model (AA vs. TT, OR = 2·94, 95% CI = 1·00-8·61, P = 0·040). However, the other three SNPs (rs11762469, rs17623204 and rs1267636) were shown to have no association with the risk of PTC.

CONCLUSIONS

Our results indicated that polymorphism of rs3748093*A was significantly correlated with an increased risk of PTC in a Chinese population. Further investigation on the aetiological mechanism of PTC is needed to validate our results.