Evaluation of candidate diagnostic microRNAs in thyroid fine-needle aspiration biopsy samples

Diagnosis of thyroid cancer: state of art

INTRODUCTION

Thyroid cancer is the most common endocrine cancer in the USA and its incidence is increasing worldwide. Thyroid fine-needle aspiration biopsy (FNA) and cytologic analysis is the most cost-effective approach to distinguish between malignant and benign thyroid nodules. However, up to 30% of thyroid FNA biopsy results are inconclusive.

AREAS COVERED

In this article, the authors provide an update on the current status and emerging approaches for improving thyroid cancer diagnosis. This review covers imaging, genetic and genomic approaches being used or in development to help distinguish between malignant and benign thyroid nodules.

EXPERT OPINION

There has been considerable progress in improving thyroid cancer diagnosis. The molecular markers analysis to avoid diagnostic surgeries seems to be promising. However, the clinical utility and accuracy of some markers reported in this review are not conclusive and need to be validated as clinical diagnostic tool.

Expressions of miRNAs in papillary thyroid carcinoma and their associations with the BRAFV600E mutation

OBJECTIVE

Alterations in microRNA (miRNA) expression have been described in thyroid tumors, suggesting a role for miRNAs in thyroid carcinogenesis. BRAF(V600E) is the most frequently identified genetic alteration in papillary thyroid carcinoma (PTC). We investigated the link between BRAF(V600E) status and the expression of miRNAs in PTC and analyzed the associations of these factors with clinicopathological characteristics.

DESIGN AND METHODS

Prospective study of patients who underwent thyroid surgery between October 8, 2008 and November 1, 2010. BRAF(V600E) status was determined by mutant allele-specific amplification PCR and direct sequencing of exon 15 of the BRAF gene in 69 PTC tissues and 69 respective paracancerous normal thyroid tissues. Initially, miRNA expression was analyzed in 12 PTC tissues and three associated paracancerous tissues using a miRNA microarray. miRNAs differentially expressed between BRAF(V600E)-positive and -negative PTC tissues were then validated by real-time quantitative PCR on 69 PTC tissues and 69 paracancerous tissues. We also explored the associations between BRAF(V600E) status or differential miRNA expression and clinicopathological characteristics.

RESULTS

The mutation rate of BRAF(V600E) in PTC was 47.8%. Twelve miRNAs were upregulated and six were downregulated in PTC tissues, among which miR-15a, 15a*, 34a*, 34b*, 551b, 873, 876-3p, and 1274a were first identified. miR-21* and 203 were significantly dysregulated (P<0.05) in PTC tissues with BRAF(V600E). Additionally, there were significant associations (P<0.05) between BRAF(V600E) and a higher tumor-node-metastasis staging (III/IV), and between miR-21* over-expression and lymph node metastasis.

CONCLUSIONS

We identified two miRNAs that are differentially expressed in PTC tissues with BRAF(V600E) and revealed their associations with clinicopathological features. These findings may lead to the development of a potential diagnostic biomarker or prognostic indicator of PTC.

Upregulation of miR-2861 and miR-451 expression in papillary thyroid carcinoma with lymph node metastasis

MicroRNA (miRNA) expression is deregulated in many types of human cancers, including thyroid cancer. The purpose of this study was to investigate miRNA deregulation in papillary thyroid carcinoma (PTC), particularly with lymph node (LN) metastasis. To identify the miRNA signature in PTC with LN metastasis, miRNAs isolated from PTC patients with LN metastasis (n = 3) and without LN (NLN) metastasis (n = 3) were used for microarray analysis. Four differentially expressed miRNAs including miR-2861, miR-451, miR-193b, and miR-1202 were selected for further validation between the LN group (n = 51) and the NLN group (n = 36) using real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The miRNA microarray results showed that compared to the NLN group, upregulation of four miRNAs including miR-2861, miR-451, miR-193b, and miR-1202 was associated with LN metastasis, whereas four other miRNAs including miR-let-7i, miR-542-5p, miR-664*, and miR-564 were downregulated in the LN group. In the validation cohort, the expression of either miR-2861 or miR-451 in the LN group was significantly greater than that in the NLN group (P = 0.004 and 0.026, respectively). Furthermore, the expression levels of miR-2861 and miR-451 in lateral lymph node (LLN) metastasis were significantly greater than those in central lymph node (CLN) metastasis (P = 0.007 and 0.001, respectively). Upregulated expression of miR-2861 and miR-451 in PTC with LN metastasis represents a unique miRNA signature associated with the prognosis and progression of PTC.

Classification of follicular cell-derived thyroid cancer by global RNA profiling

The incidence of thyroid cancer is increasing worldwide and thyroid nodules are a frequent clinical finding. Diagnosing follicular cell-derived cancers is, however, challenging both histopathologically and especially cytopathologically. The advent of high-throughput molecular technologies has prompted many researchers to explore the transcriptome and, in recent years, also the miRNome in order to generate new molecular classifiers capable of classifying thyroid tumours more accurately than by conventional cytopathological and histopathological methods. This has led to a number of molecular classifiers that may differentiate malignant from benign thyroid nodules. Molecular classification models based on global RNA profiles from fine-needle aspirations are currently being evaluated; results are preliminary and lack validation in prospective clinical trials. There is no doubt that molecular classification will not only contribute to our biological insight but also improve clinical and pathological examinations, thus advancing thyroid tumour diagnosis and ultimately preventing superfluous surgery. This review evaluates the status of classification and biological insights gained from molecular profiling of follicular cell-derived thyroid cancers.

Diagnostic use of molecular markers in the evaluation of thyroid nodules

OBJECTIVE

To describe the molecular markers thus far evaluated for use in the care of patients with clinically relevant thyroid nodules.

METHODS

We review the currently available molecular tests that have been applied to patients with thyroid nodules.

RESULTS

In the United States, approximately 450 000 diagnostic fine-needle aspirates will be performed on patients with thyroid nodules this year in an effort to identify thyroid cancer. Unfortunately, this test is imprecise and, at times, inaccurate. Because of this, novel diagnostic testing modalities have been pursued, the most promising of which involve molecular analysis of thyroid tissue. Immunohistochemical staining, analysis for mutations and gene rearrangements, and microarray analysis have all been investigated with regard to their performance characteristics in targeted patient populations.

CONCLUSIONS

Molecular tests to evaluate thyroid nodules demonstrate variable performance characteristics. Further evaluation of available and emerging molecular tests will necessarily rely on prospective real-world test validation in the clinical setting.

MicroRNA expression profiles in differentiated thyroid cancer, a review

MicroRNAs (miRNAs) are a class of short endogenous non-coding RNAs regulating gene expression in many biological processes, including proliferation, apoptosis and differentiation. The deregulation of miRNA expression is believed to be an important regulator of tumor development and progression of thyroid cancer. In this review, we discussed important roles and expression profiles of miRNA in differentiated thyroid cancer (DTC) as well as the promising implication in clinical practice.

MicroRNA expression profile helps to distinguish benign nodules from papillary thyroid carcinomas starting from cells of fine-needle aspiration

OBJECTIVE

MicroRNAs (miRNAs) are small endogenous noncoding RNAs that pair with target messengers regulating gene expression. Changes in miRNA levels occur in thyroid cancer. Fine-needle aspiration (FNA) with cytological evaluation is the most reliable tool for malignancy prediction in thyroid nodules, but cytological diagnosis remains undetermined for 20% of nodules.

DESIGN

In this study, we evaluated the expression of seven miRNAs in benign nodules, papillary thyroid carcinomas (PTCs), and undetermined nodules at FNA.

METHODS

The prospective study included 141 samples obtained by FNA of thyroid nodules from 138 patients. miRNA expression was evaluated by quantitative RT-PCR and statistical analysis of data was performed. Genetic analysis of codon 600 of BRAF gene was also performed.

RESULTS

Using data mining techniques, we obtained a criterion to classify a nodule as benign or malignant on the basis of miRNA expression. The decision model based on the expression of miR-146b, miR-155, and miR-221 was valid for 86/88 nodules with determined cytology (97.73%), and adopting cross-validation techniques we obtained a reliability of 78.41%. The prediction was valid for 31/53 undetermined nodules with 16 false-positive and six false-negative predictions. The mutated form V600E of BRAF gene was demonstrated in 19/43 PTCs and in 1/53 undetermined nodules.

CONCLUSIONS

The expression profiles of three miRNAs allowed us to distinguish benign from PTC starting from FNA. When the assay was applied to discriminate thyroid nodules with undetermined cytology, a low sensitivity and specificity despite the low number of false-negative predictions was obtained, limiting the practical interest of the method.