MicroRNA deregulation in human thyroid papillary carcinomas

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.

DNA microarray and miRNA analyses reinforce the classification of follicular thyroid tumors

CONTEXT

Focusing on mitochondrial function and thyroid tumorigenesis, we used an integrative approach to identify relevant biomarkers for borderline thyroid lesions.

DESIGN

Using cDNA and microRNA (miRNA) microarrays and quantitative RT-PCR analysis (qPCR), we explored samples of various types of thyroid tumors including 25 benign follicular adenomas represented by macrofollicular variants of thyroid adenomas, 38 oncocytic variants of follicular thyroid tumors, 19 papillary thyroid carcinomas, and 10 tumors of uncertain malignant potential, together with 53 normal thyroid tissue samples.

RESULTS

Our transcriptomic analysis, which highlighted discrepancies between controls and tumor tissues, as well as between various tumor types, led to the identification of 13 genes, allowing discrimination between the thyroid adenomas, oncocytic variants of follicular thyroid tumors, and papillary thyroid carcinomas, whereas the tumors of uncertain malignant potential were found to overlap these classes. Five of these genes (TP53, HOXA9, RUNX1, MYD88, and CITED1), with a differential expression confirmed by qPCR analysis, are implicated in tumorigenesis, 4 in mitochondrial metabolism (MRPL14, MRPS2, MRPS28, and COX6A1), and 2 in thyroid metabolic pathways (CaMKIINalpha and TPO). The global miRNA analysis revealed 62 differential miRNAs, the expression level for 10 of these being confirmed by qPCR. The differential expression of the miRNAs was in accordance with the modulation of gene expression and the ontologies revealed by our transcriptomic analysis.

CONCLUSIONS

These findings reinforce the classification of follicular thyroid tumors established by the World Health Organization, and our technique offers a novel molecular approach to refine the classification of thyroid tumors of uncertain malignant potential.

Genetic mutations, molecular markers and future directions in research

Recent molecular studies have described a number of abnormalities associated with the pathogenesis of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development and may serve as prognostic factors and therapeutic targets. A better understanding of the mechanisms involved in thyroid cancer pathogenesis, will hopefully help translate these discoveries to improved patient care.

Association between the expression of four upregulated miRNAs and extrathyroidal invasion in papillary thyroid carcinoma

Background

MicroRNAs (miRNAs) are important diagnostic and prognostic markers in cancer. In the study reported here, we analyzed the potential relationship between miRNA expression and extrathyroidal invasion in papillary thyroid carcinoma (PTC).

Methods

Samples from 91 patients with PTC were collected from January 2008 to April 2012 at our hospital. To detect the levels of miRNA expression in fresh frozen tissues from patients with extrathyroidal invasion (n = 3) and non-extrathyroidal invasion (n = 3), miRNA array was carried out. The upregulated miRNAs between the two groups were confirmed by using real-time reverse transcriptase polymerase chain reaction.

Results

The levels of miR-146b, miR-221, miR-222, and miR-135b were significantly higher in the extrathyroidal invasion group than in the non-extrathyroidal invasion group (P = 0.001, 0.019, 0.004, and 0.006, respectively). In addition, the miR-146b expression level was significantly higher in the massive extrathyroidal invasion group than in the minimal extrathyroidal invasion group (P = 0.016). The expression levels of miR-146b, miR-222, and miR-135b were significantly associated with tumor size (P = 0.018, 0.008, and 0.024, respectively). The upregulation of miR-146b and miR-222 was significantly associated with higher tumor-node-metastasis stage (P = 0.004 and 0.0001, respectively). The expression level of miR-222 was also correlated with age and sex (P = 0.048 and 0.002, respectively).

Conclusion

Our results reveal that the expression of four miRNAs correlated with extrathyroidal invasion and other clinicopathologic features in PTCs, which may support their potential clinical value as prognostic biomarkers for PTCs.

MicroRNAs as new biomarkers in oncology

MicroRNAs (miRNAs) represent a new class of small non-coding RNAs ∼ 22 nucleotides in length that are involved in fine-tuning of gene expression. An increasing number of papers are identifying a link between miRNAs and cancer. The discovery of miRNA expression signatures able to discriminate tumor from normal cells and between various categories of patients with the same type of cancer suggests the possible application of miRNAs as new biomarkers in molecular oncology. In this review, the authors describe the different techniques used to detect miRNAs in tumor samples and their potential for clinical use. The authors review the published evidence testing miRNAs as novel cancer biomarkers and describe the steps necessary to move forward in the application of miRNAs as biomarkers. Finally, the authors consider the utility of miRNAs as tumor predisposition markers in cancer screening programs.

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.

Expression profiles of microRNAs and their target genes in papillary thyroid carcinoma

The incidence of thyroid cancer has recently experienced a rapid increase in China, and papillary thyroid carcinoma (PTC) accounts for nearly 80% of human thyroid cancers. In the present study, the differential expression of microRNAs (miRNAs) and their target genes were identified in order to analyze the potential roles of miRNAs as biomarkers and in papillary thyroid carcinogenesis. One hundred and twenty-six PTC samples were collected from patients at the China-Japan Union Hospital, China, and the gene/miRNA expression profiles were examined with Illumina BeadChips and verified by real‑time RT-PCR. Gene Ontology (GO) categories were determined, and pathway analysis was carried out using KEGG. miRNA target genes were predicted by implementing three computational analysis programs: TargetScanS, DIANA-microT and PicTar. Two hundred and forty-eight miRNAs and 3,631 genes were found to be significantly deregulated (gene, P<0.05; miRNA, P<0.01) in PTC tissues when compared with their matching normal thyroid tissues. hsa-miR-206 (target gene, MET), hsa-miR-299-3p (target gene, ITGAV), hsa-miR-101 (target gene, ITGA3), hsa-miR-103 (target gene, ITGA2), hsa-miR‑222 (target genes, KIT and AXIN2), hsa-miR-15a (target genes, AXIN2 and FOXO1) and hsa-mir-221 (target gene, KIT) were identified. Together with the functions of the target genes, we further elucidated the role of miRNAs in papillary thyroid carcinogenesis and suggest the use of miRNAs as biomarkers for early diagnosis. Our findings provide the basis for future studies in the field of miRNA-based cancer therapy.

Overview of molecular biomarkers for enhancing the management of cytologically indeterminate thyroid nodules and thyroid cancer

OBJECTIVE

To provide information on molecular biomarkers that can help assess cytologically indeterminate thyroid nodules.

METHODS

Published studies on immunohistologic, somatic mutation, gene expression classifier, microRNA, and thyrotropin receptor messenger RNA biomarkers are reviewed, and commercially available molecular test panels are described.

RESULTS

Thyroid nodules are common, and clinical guidelines delineate an algorithmic approach including serum thyroid-stimulating hormone measurement, diagnostic ultrasound examination, and, when appropriate, fine-needle aspiration (FNA) biopsy for determination of a benign versus malignant status. In clinical practice, approximately 20% of FNA-derived cytology reports are classified as "indeterminate" or follicular nodules that do not fulfill either benign or malignant criteria. In this setting, the actual risk for malignancy of a cytologically indeterminate nodule ranges from approximately 15% to 34%. Research describing molecular biomarkers from thyroid cancer tissue has been applied to FNA-derived thyroid nodule material. There is also a serum molecular marker that has been reported with goals similar to those for the FNA-derived molecular markers: to enhance the preoperative diagnosis of thyroid cancer and reduce the large number of patients who have a diagnostic surgical procedure for benign thyroid nodules.

CONCLUSION

Progress toward the foregoing goals has been made and continues to evolve with the recent appearance of molecular biomarker tests that can be selectively applied for further assessment of cytologically indeterminate thyroid nodules.

Inverse correlation of miRNA and cell cycle-associated genes suggests influence of miRNA on benign thyroid nodule tumorigenesis

CONTEXT

The molecular etiology of cold and benign thyroid nodules (CBTNs) is largely unknown. Increased thyroid epithelial cell proliferation is a hallmark of CBTNs. MicroRNAs (miRNAs) are prominent regulators of cell proliferation.

OBJECTIVE

Our objective was to assess the influence of miRNAs on the increased proliferation and thus the molecular etiology of CBTNs.

DESIGN

By using microarrays, we defined the molecular pattern of increased proliferation of CBTNs as a differential expression of cell-cycle-associated genes and miRNAs. In silico integration of differentially expressed miRNAs and mRNAs showed an inverse correlation between the expression of 59 miRNAs and 133 mRNAs. Inverse correlations between cell-cycle-associated genes such as CDKN1C and miR-221, CCND1 and miR-31, GADD45A and miR-130b, or CDKN1A and let-7f suggest a modulation of proliferation in CBTNs by miRNAs. Their expression was validated using quantitative RT-PCR and functionally characterized in cell line models.

RESULTS

Comparative quantitative RT-PCR of 20 samples of CBTNs and their surrounding tissue revealed an 11-fold down-regulation of miR-31 with a 2.6-fold up-regulation of CCND1, and a 2.6-fold up-regulation of miR-130b with a 2.3-fold down-regulation of its target GADD45A. Using HTori and FTC-133 cell lines, we analyzed proliferation, cell cycle, and apoptosis after transfection of miRNA-31 and miRNA-130b mimic and inhibitors. Overexpression of miR-31 and the resultant down-regulation of CCND1 led to an arrest in the cell cycle phase G1. Overexpression of miR-130b led to an increase of apoptosis and necrosis within 72 h.

CONCLUSION

miR-31 and miR-130b may have an effect on tumorigenesis of CBTNs by regulating proliferation and apoptosis and the cell cycle through cyclin D1.

MicroRNA expression array identifies novel diagnostic markers for conventional and oncocytic follicular thyroid carcinomas

OBJECTIVE

The most difficult thyroid tumors to be diagnosed by cytology and histology are conventional follicular carcinomas (cFTCs) and oncocytic follicular carcinomas (oFTCs). Several microRNAs (miRNAs) have been previously found to be consistently deregulated in papillary thyroid carcinomas; however, very limited information is available for cFTC and oFTC. The aim of this study was to explore miRNA deregulation and find candidate miRNA markers for follicular carcinomas that can be used diagnostically.

DESIGN

Thirty-eight follicular thyroid carcinomas (21 cFTCs, 17 oFTCs) and 10 normal thyroid tissue samples were studied for expression of 381 miRNAs using human microarray assays. Expression of deregulated miRNAs was confirmed by individual RT-PCR assays in all samples. In addition, 11 follicular adenomas, two hyperplastic nodules (HNs), and 19 fine-needle aspiration samples were studied for expression of novel miRNA markers detected in this study.

RESULTS

The unsupervised hierarchical clustering analysis demonstrated individual clusters for cFTC and oFTC, indicating the difference in miRNA expression between these tumor types. Both cFTCs and oFTCs showed an up-regulation of miR-182/-183/-221/-222/-125a-3p and a down-regulation of miR-542-5p/-574-3p/-455/-199a. Novel miRNA (miR-885-5p) was found to be strongly up-regulated (>40-fold) in oFTCs but not in cFTCs, follicular adenomas, and HNs. The classification and regression tree algorithm applied to fine-needle aspiration samples demonstrated that three dysregulated miRNAs (miR-885-5p/-221/-574-3p) allowed distinguishing follicular thyroid carcinomas from benign HNs with high accuracy.

CONCLUSIONS

In this study we demonstrate that different histopathological types of follicular thyroid carcinomas have distinct miRNA expression profiles. MiR-885-5p is highly up-regulated in oncocytic follicular carcinomas and may serve as a diagnostic marker for these tumors. A small set of deregulated miRNAs allows for an accurate discrimination between follicular carcinomas and hyperplastic nodules and can be used diagnostically in fine-needle aspiration biopsies.

Expression of miRNAs in Papillary Thyroid Carcinomas Is Associated with BRAF Mutation and Clinicopathological Features in Chinese Patients

MicroRNAs (miRNAs) dysregulation has been shown to play a critical regulatory role in papillary thyroid carcinomas (PTCs). BRAF mutation is associated with poor clinicopathological outcomes in PTC. In order to identify a possible association between dysregulated miRNA expression and BRAF mutation as well as clinicopathological features in Chinese patients with PTC, we examined the expression levels of five reported dysregulated miRNAs (miRNA-221, miRNA-222, miRNA-146b, miRNA-181, and miRNA-21) and determined BRAF mutation status in 52 patients with PTC and 52 patients with benign thyroid nodules (BTNs). The expression levels of all five miRNAs were significantly increased in PTC when compared to BTN. The BRAF mutation occurred more frequently in PTC cases with advanced TNM stage. Importantly, miRNA-221, miRNA-222, miRNA-146b, and miRNA-181 expression levels were significantly higher in PTC patients with BRAF mutation. In addition, enhanced expression of miRNA-221 and miRNA-222 was found in patients with cervical lymph node metastasis and advanced TNM stage. Increased expression of miRNA-221 and miR-181 was evidenced in patients with larger tumors. These findings showed a potential role of this distinct profile of miRNAs in differentiating PTC from BTN. BRAF mutation might regulate or interact with miRNA in the pathogenesis and progression of PTC.

[MicroRNA profiles in fine needle biopsy of the thyroid]

MicroRNAs (miRNAs) are small (20-24 nucleotides), non-coding ribonucleid acids, which regulate gene expression on the post-transcriptional level, thus influencing physiological processes including cellular growth, differentiation and apoptosis. Several miRNAs (e. g. miRNAs 146b, 221 and 222) have been shown to be consistently over-expressed in papillary thyroid carcinoma. The present overview describes and discusses the utilization and problems of miRNA analysis in material from thyroid nodules obtained by fine needle biopsy. Particularly the analysis of defined sets of miRNAs should improve the diagnostic value of this procedure and contribute to a better management of patients with cold thyroid nodules.

Update on thyroid cancer treatment

Surgery and radioiodine therapy are usually effective for most patients with differentiated thyroid cancer. However, poorly differentiated and anaplastic thyroid carcinomas represent a challenge to physicians on the basis of the current cancer treatment modalities. These cancer subtypes are often lethal and refractory to radioiodine therapy as well as most of the common chemotherapy drugs. Several kinase inhibitors are promising targeted therapies for these malignancies; however, clinical trials involving these drugs have provided controversial results and their clinical use is still under debate. Advanced medullary thyroid carcinomas may also be refractory to conventional therapies and novel kinase inhibitors may also be useful to control tumor progression in certain patients. Novel evidence is emerging that thyroid cancer is a stem cell disease, thereby implying that the driving force of thyroid cancers is a subset of undifferentiated cells (thyroid cancer stem cells) with unlimited growth potential and resistance to conventional therapeutic regimens. Thyroid cancer stem cells have been proposed as responsible for tumor invasiveness, metastasis, relapse and differentiation. Therefore, drugs that selectively target these cells could serve as a cornerstone in the treatment of poorly differentiated thyroid cancer.

microRNA-181a is associated with poor prognosis of colorectal cancer

miRNAs regulate gene expression at the post-transcriptional level by degradation of mRNA and translational repression. Recent studies have shown that miR-181a is dysregulated in several types of cancer; however, the clinical significance of miR‑181a in colorectal cancer (CRC) remains unclear. We addressed this question by using quantitative real-time PCR (qRT-PCR) to analyze miR-181a expression in 162 CRC patients. There was no significant difference in miR-181a expression in normal colon vs. colorectal cancer tissue. The cancer tissue samples were categorized into a low and high expression group based on miR-181a expression. Comparison of the clinicopathological factors and prognosis in these two groups showed that the high expression group had a significantly poorer prognosis than the low expression group (P=0.011). Multivariate analysis indicated that high miR-181a expression was an independent significant prognostic factor for CRC. However, there no correlation was observed between miR-181a expression and clinicopathological parameters. In vitro analysis revealed that the overexpression of miR-181a repressed the expression of the tumor suppressor, phosphatase and tensin homolog (PTEN) located on chromosome 10, at the mRNA level. These data suggest that miR-181a may be a new independent prognostic factor for CRC patients.

Thyrotropin regulates thyroid cell proliferation by up-regulating miR-23b and miR-29b that target SMAD3

CONTEXT

MicroRNA (miRNA or miR) have emerged as an important class of short endogenous RNA that act as post-transcriptional regulators of gene expression and have a critical role in cell proliferation and differentiation.

OBJECTIVES

The aim of this study was to elucidate the role of miRNA in the proliferation of differentiated thyroid cells that require TSH for their growth.

DESIGN

To elucidate the role of miRNA in thyroid cell proliferation, we have analyzed the miRNA expression profile of PC Cl 3 cells before and after the stimulation by TSH.

RESULTS

We report the identification of two specific miRNA (miR-23b and miR-29b) whose up-regulation by TSH is required for thyroid cell growth. We identified mothers against decapentaplegic homolog 3 (Smad3), a member of the TGF-β pathway that has an inhibitor role in thyroid follicular cell proliferation as a target of miR-23b and miR-29b. Functional studies demonstrated that the overexpression of miR-23b and miR-29b promotes thyroid cell growth. Interestingly, an increased expression of both these miRNA was also detected in experimental and human goiters.

CONCLUSIONS

These findings support the idea that the regulation of miRNA expression synergizes with the traditional proliferation pathways in promoting cell growth.

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.

Liver tumorigenicity promoted by microRNA-221 in a mouse transgenic model

MicroRNA-221 (miR-221) is one of the most frequently and consistently up-regulated microRNAs (miRNAs) in human cancer. It has been hypothesized that miR-221 may act as a tumor promoter. To demonstrate this, we developed a transgenic (TG) mouse model that exhibits an inappropriate overexpression of miR-221 in the liver. Immunoblotting and immunostaining confirmed a concomitant down-regulation of miR-221 target proteins. This TG model is characterized by the emergence of spontaneous nodular liver lesions in approximately 50% of male mice and by a strong acceleration of tumor development in 100% of mice treated with diethylnitrosamine. Similarly to human hepatocellular carcinoma, tumors are characterized by a further increase in miR-221 expression and a concomitant inhibition of its target protein-coding genes (i.e., cyclin-dependent kinase inhibitor [Cdkn]1b/p27, Cdkn1c/p57, and B-cell lymphoma 2-modifying factor). To validate the tumor-promoting effect of miR-221, we showed that in vivo delivery of anti-miR-221 oligonucleotides leads to a significant reduction of the number and size of tumor nodules.

CONCLUSIONS

This study not only establishes that miR-221 can promote liver tumorigenicity, but it also establishes a valuable animal model to perform preclinical investigations for the use of anti-miRNA approaches aimed at liver cancer therapy.

[Hyalinizing trabecular tumor of the thyroid. An overcautious designation of a benign thyroid tumour?]

Hyalinizing trabecular tumours of the thyroid represent a rare entity of follicular cell derived tumours and are characterized by a marked intratrabecular hyalinisation. These tumours share architectural similarities with medullary thyroid carcinomas and exhibit nuclear features such as nuclear pseudoinclusions resembling papillary thyroid carcinoma. However, the clinical behaviour remains unclear. On the basis of their inconspicuous appearance and absence of invasion or recurrence during follow-up, the tumour was initially classified as an adenoma. Subsequently, molecular findings such as the detection of RET / PTC rearrangements in some hyalinizing trabecular tumours favoured the designation as a variant of papillary thyroid carcinoma. However, miRNA profiling of hyalinizing trabecular tumours compared with benign thyroid lesions and papillary thyroid carcinoma failed to demonstrate the characteristic up-regulation found in papillary thyroid carcinoma. This article summarizes conventional diagnostic criteria with supplementary information regarding molecular pathogenesis of hyalinizing trabecular tumours of the thyroid.

Employing genetic markers to improve diagnosis of thyroid tumor fine needle biopsy

Fine-Needle Aspiration (FNA) is the most widely used and cost-effective preoperative test for the initial evaluation of a thyroid nodule, although it has limited diagnostic accuracy for several types of tumors. Patients will often receive cytological report of indeterminate cytology and are referred to surgery for a more accurate diagnosis. An improved test would help physicians rapidly focus treatment on true malignancies and avoid some unnecessary treatment of benign tumors. This review will discuss current molecular markers that may improve thyroid nodule diagnosis.

microRNAs and thyroid cancer: biological and clinical significance (Review)

Despite recent advances in the management of thyroid cancer, the survival rate of this tumor may still be improved. Therefore, the identification of biological and molecular features of indolent and aggressive disease would be critical to define clinically useful predictors of high-risk lesions. microRNAs (miRNAs) are small RNA molecules with regulatory function and marked tissue specificity that modulate multiple targets belonging to several pathways. They are frequently deregulated in cancer and constitute a new class of blood-based biomarkers useful for cancer detection and prognosis definition, including thyroid cancer. In this review, the role of miRNAs in thyroid cancer development is described. The most common miRNAs detected in thyroid cancer along with their clinical significance are also discussed. Further studies aimed to detect plasma-based miRNA biomarkers in thyroid cancer patients may provide further insight into the management of thyroid cancer.

Overexpression of miR-221 is associated with aggressive clinicopathologic characteristics and the BRAF mutation in papillary thyroid carcinomas

Correlation between clinicopathogenetic features and the expression of specific miRNAs is unclear in papillary thyroid carcinoma (PTC). We therefore sought to assess whether miR-221 was associated with aggressive clinicopathologic characteristics and the BRAF mutation. We studied the expression levels of miR-221 using northern blot quantitated by scion image in 51 cases of PTCs. The status of BRAF of PTCs was analyzed through direct DNA sequencing. Mann-Whitney U test was used to analyze different expression of miR-221 in PTCs with distinct clinicopathogenetic characteristics including gender, age, tumor size, multifocality, extrathyroidal invasion, disease stages, node metastasis, and BRAF status. Compared with the normal thyroid tissues, the relative expression of miR-221 in tumor tissues was significantly upregulated (p < 0.001). Overexpression of miR-221 was significantly associated with extrathyroidal invasion (p = 0.001), lymph node metastasis (p = 0.046), advanced disease stages III-IV (p = 0.001), and the BRAF mutation (p = 0.014). While among BRAF wild tumors, miR-221 was only associated with extarthyroidal invasion, it showed strong association with all above aggressive features among BRAF mutation tumors. MiR-221 may be of potential importance in determining the aggressive properties of PTCs including the BRAF mutation, and it may further refine the risk stratification by BRAF mutation in PTCs.

MicroRNA as a diagnostic tool in fine-needle aspiration biopsy of thyroid nodules

Thyroid cancer accounts for 1.5% of all malignancies in the U.S., and it is the most common endocrine malignancy. Detection of thyroid cancer mostly relies on evaluation of thyroid nodules, which are very common but only 5%-7% harbor malignancy. Fine-needle aspiration biopsy (FNAB) is currently the most important tool for the evaluation of thyroid nodules; however, it is limited in that it provides only a cytology assessment of the aspirated cells, and indeterminate diagnoses are present in up to 30% of FNAB results. This limitation can be overcome by the molecular analysis of FNAB, and more specifically with the use of microRNAs (miRs). miRs constitute a class of endogenous small noncoding RNA fragments that regulate gene expression, and in vitro studies have shown that miRs play a significant role in cancer and regulate major processes, such as proliferation, differentiation, and cell death. Several studies have investigated the miR expression signature in different thyroid cancers, and data support its use as a diagnostic tool that is highly accurate for thyroid nodules. The purpose of this study is to review the accumulated data on miR dysregulation in the different thyroid cancer types, critically assess its diagnostic utility, and conclude with future study strategies.

Altered microRNA expression in cisplatin-resistant ovarian cancer cells and upregulation of miR-130a associated with MDR1/P-glycoprotein-mediated drug resistance

microRNAs (miRNAs) are short non-coding RNA molecules which are involved in the regulation of various biological processes. Drug resistance has become a major obstacle to successful chemotherapy of ovarian cancer. The aim of this study was to investigate microRNA expression profiles in cisplatin-resistant ovarian cancer cells and the role of miR-130a in regulating drug resistance. Analysis of differentially expressed miRNAs between SKOV3 and SKOV3/CIS cells was assessed by miRNA microarrays. Target prediction of miRNAs was determined with the help of PicTar or TargetScan. Among these miRNAs, the expression of miR‑130a was verified using qRT-PCR. The expression of MDR1 mRNA and P-glycoprotein (P-gp) after cellular transfection was examined using qRT-PCR and western blotting, respectively. Cisplatin sensitivity was detected by the MTT assay. We indentified 35 downregulated and 54 upregulated miRNAs in SKOV3/CIS compared to those in SKOV3. We found that miR-130a was upregulated in SKOV3/CIS compared to the parental SKOV3 cells, and PTEN was predicted to be the potential target of miR-130a. Moreover, downregulation of miR-130a could inhibit MDR1 mRNA and P-gp expression and overcome the cisplatin resistance in SKOV3/CIS cells, which indicated that miR-130a may be associated with MDR1/P-gp-mediated drug resistance and plays the role of an intermediate in drug-resistance pathways of PI3K/Akt/PTEN/mTOR and ABC superfamily drug transporters in SKOV3/CIS cells. This study provides important information for the development of targeted gene therapy for reversing cisplatin resistance in ovarian cancer.

The quest for diagnostic molecular markers for thyroid nodules with indeterminate or suspicious cytology

Thyroid nodules are very common and fine needle aspiration (FNA) is a very sensitive means of diagnosis. However, its limitations include the fact that the cytology reports are often indeterminate or suspicious only. The quest for adjunctive measures to improve its specificity has been ongoing for decades, but significant results have remained elusive. The potential use of diagnostic molecular markers appears to be the most promising area of research at this time.

RETRACTED: MicroRNA-19a and -19b regulate cervical carcinoma cell proliferation and invasion by targeting CUL5

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. Upon investigation, it was discovered that 4 out of 8 images contain fabrication. Figures 6D, 6E, 8E and 7F have used the same microscopic image for different experimental settings. The Figure represented in 8E is the correct image placement. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Reference genes for real-time PCR quantification of microRNAs and messenger RNAs in rat models of hepatotoxicity

Hepatotoxicity is associated with major changes in liver gene expression induced by xenobiotic exposure. Understanding the underlying mechanisms is critical for its clinical diagnosis and treatment. MicroRNAs are key regulators of gene expression that control mRNA stability and translation, during normal development and pathology. The canonical technique to measure gene transcript levels is Real-Time qPCR, which has been successfully modified to determine the levels of microRNAs as well. However, in order to obtain accurate data in a multi-step method like RT-qPCR, the normalization with endogenous, stably expressed reference genes is mandatory. Since the expression stability of candidate reference genes varies greatly depending on experimental factors, the aim of our study was to identify a combination of genes for optimal normalization of microRNA and mRNA qPCR expression data in experimental models of acute hepatotoxicity. Rats were treated with four traditional hepatotoxins: acetaminophen, carbon tetrachloride, D-galactosamine and thioacetamide, and the liver expression levels of two groups of candidate reference genes, one for microRNA and the other for mRNA normalization, were determined by RT-qPCR in compliance with the MIQE guidelines. In the present study, we report that traditional reference genes such as U6 spliceosomal RNA, Beta Actin and Glyceraldehyde-3P-dehydrogenase altered their expression in response to classic hepatotoxins and therefore cannot be used as reference genes in hepatotoxicity studies. Stability rankings of candidate reference genes, considering only those that did not alter their expression, were determined using geNorm, NormFinder and BestKeeper software packages. The potential candidates whose measurements were stable were further tested in different combinations to find the optimal set of reference genes that accurately determine mRNA and miRNA levels. Finally, the combination of MicroRNA-16/5S Ribosomal RNA and Beta 2 Microglobulin/18S Ribosomal RNA were validated as optimal reference genes for microRNA and mRNA quantification, respectively, in rat models of acute hepatotoxicity.

Androgen receptor expression in human thyroid cancer tissues: a potential mechanism underlying the gender bias in the incidence of thyroid cancers

Gender bias in the incidence of thyroid cancer is well known, however, the underlying mechanism is largely unknown. The current study determines variations in the molecular characteristics of thyroid cancers between men and women. Normal and cancerous thyroid tissues were collected from a total of 125 men and women who underwent surgical thyroidectomy. Testosterone levels in serum and thyroid cancer tissues were elevated in women while it decreased in men compared to respective control groups; whereas, ligand binding activity increased in men and decreased in women. Androgen receptor (AR) mRNA expression increased in a majority of men while it decreased in a majority of women except those with follicular thyroid carcinoma (FTC). In thyroid cancers of women, Pearson's correlation analysis showed a positive correlation of AR mRNA with AR protein, CBP and Sp1, whereas AR mRNA showed a negative correlation with p53. In case of men, AR mRNA showed a positive correlation with AR and cyclin D1 proteins in papillary thyroid carcinoma (PTC); and CBP and Sp1 in follicular thyroid adenoma (FTA), whereas AR mRNA showed a positive correlation with p53. Our study identified for the first time that AR is posttranscriptionally regulated by miR-124a in thyroid cancer tissues. Further, our in vitro studies with a PTC cell line (NPA-87-1) showed miR-124a as the potent inhibitor of AR that impairs cell proliferation even in the presence of testosterone. Thus, the current study suggests that: (i) the varying pattern of testosterone level and AR status in thyroid tissues of men and women may predispose to the gender specific incidence of thyroid tumors and (ii) miR-124a plays a significant role in determining the AR gene expression pattern and thus, androgen mediated thyroid tumor growth.

Association between two genetic variants in miRNA and primary liver cancer risk in the Chinese population

MicroRNAs (miRNAs) play an important role in the growth and development of human beings. Single nucleotide polymorphisms (SNPs) within miRNA could change their production or affinity with target genes, thus leading to malignant diseases. This case-control study conducted in Western China aimed to explore the relationship between polymorphisms in miR-146a (rs2910164 G>C) and miR-499 (rs3746444 T>C) and primary liver cancers in the Chinese population. 186 primary liver cancer cases and 483 healthy controls were genotyped using polymerase chain reaction-restriction fragment length polymorphism. No significant differences were observed between distributions of the two SNPs and susceptibility of primary liver cancer or diverse clinicopathologic features. However, we found that patients with genotype CG of the SNP in miR-146a tended to have earlier onset and better liver function than patients with genotype CC (average age: 49.9 vs. 54.9, p=0.038; average Child-Pugh grade: 5.55 vs. 6.15, p=0.021), and further analysis showed that patients who had at least one G allele were diagnosed at an earlier age (average age: 49.6 vs. 54.9, p=0.022) and had better liver function (average Child-Pugh grade:5.60 vs. 6.15, p=0.026). Our data suggested lack of association between the two SNPs and primary liver cancer risk, though, interestingly, the miR-146a SNP may influence the age of onset and Child-Pugh grade.

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

BACKGROUND

Thyroid cancer diagnosis in the United States has increased by 2.3-folds in the last three decades. Up to 30% of thyroid fine-needle aspiration biopsy (FNAB) results are inconclusive. Several differentially expressed microRNAs (miRNAs) have been identified as candidate diagnostic markers for thyroid nodules. We hypothesized that these differentially expressed miRNAs may improve the accuracy of FNAB in difficult to diagnose thyroid nodules.

METHODS

Expression levels of four miRNAs (miR-7, -126, -374a, and let-7g) were analyzed using quantitative real-time reverse transcription-polymerase chain reaction in 95 FNAB samples as the training set. A predictor model was formulated based on the most differentially expressed miRNA (miR-7) ΔCt value and the model was applied on a separate cohort of 59 FNAB samples as the validation set.

RESULTS

miR-7 was the best predictor to distinguish benign from malignant thyroid FNAB samples. The other three miRNAs were co-expressed and did not significantly contribute to the predictor model. miR-7 had a sensitivity of 100%, specificity of 29%, positive predictive value (PPV) of 36%, negative predictive value (NPV) of 100%, and overall accuracy of 76% when applied to the validation set. In subgroup analysis of preoperative nondiagnostic, indeterminate, or suspicious FNAB samples, the predictor model had an overall accuracy of 37% with sensitivity of 100%, specificity of 20%, PPV of 25%, and NPV of 100%.

CONCLUSIONS

miR-7 may be a helpful adjunct marker to thyroid FNAB in tumor types which are inconclusive. Given the high NPV of miR-7, a patient with a benign result based on the predictor model may be followed as opposed to performing an immediate diagnostic thyroidectomy. Future prospective clinical trials evaluating its accuracy in a larger cohort are warranted to determine its clinical utility.

A panel of four miRNAs accurately differentiates malignant from benign indeterminate thyroid lesions on fine needle aspiration

PURPOSE

Indeterminate thyroid lesions on fine needle aspiration (FNA) harbor malignancy in about 25% of cases. Hemi- or total thyroidectomy has, therefore, been routinely advocated for definitive diagnosis. In this study, we analyzed miRNA expression in indeterminate FNA samples and determined its prognostic effects on final pathologic diagnosis.

EXPERIMENTAL DESIGN

A predictive model was derived using 29 ex vivo indeterminate thyroid lesions on FNA to differentiate malignant from benign tumors at a tertiary referral center and validated on an independent set of 72 prospectively collected in vivo FNA samples. Expression levels of miR-222, miR-328, miR-197, miR-21, miR-181a, and miR-146b were determined using reverse transcriptase PCR. A statistical model was developed using the support vector machine (SVM) approach.

RESULTS

A SVM model with four miRNAs (miR-222, miR-328, miR-197, and miR-21) was initially estimated to have 86% predictive accuracy using cross-validation. When applied to the 72 independent in vivo validation samples, performance was actually better than predicted with a sensitivity of 100% and specificity of 86%, for a predictive accuracy of 90% in differentiating malignant from benign indeterminate lesions. When Hurthle cell lesions were excluded, overall accuracy improved to 97% with 100% sensitivity and 95% specificity.

CONCLUSIONS

This study shows that that the expression of miR-222, miR-328, miR-197, and miR-21 combined in a predictive model is accurate at differentiating malignant from benign indeterminate thyroid lesions on FNA. These findings suggest that FNA miRNA analysis could be a useful adjunct in the management algorithm of patients with thyroid nodules.

Increased miR-222 in H. pylori-associated gastric cancer correlated with tumor progression by promoting cancer cell proliferation and targeting RECK

Little is known about the potential role of microRNAs (miRNAs) in the carcinogenesis of gastric cancer induced by Helicobacter pylori (H. pylori). Here, we showed that microRNA-222 (miR-222) was up-regulated in H. pylori-infected gastric mucosa and gastric cancer. Ectopic expression of miR-222 promoted cell proliferation and colony formation in vitro. Mechanistically, we identified RECK as a novel target of miR-222, and also confirmed their relationship by the inverse correlation of mRNA expression ex vivo. Furthermore, we found that RNA interference silencing of RECK can mimic the oncogenic effects of miR-222. Collectively, H. pylori may function as an initiator in the process of carcinogenesis by up-regulating miR-222, which further participates in the progression of cancer by promoting proliferation and inhibiting RECK.

Identification of microRNAs that mediate thyroid cell growth induced by TSH

TSH is a major regulator of thyroid cell growth and endocrine function. It is known that cAMP and phosphatidylinositol 3-kinase (PI3K) are responsible for mediating the action of TSH. Activation of these signals results in the induction of a series of transcription factors and cell cycle regulating proteins, which induce cell proliferation. In addition to such canonical transcriptional regulation, it was recently shown that microRNA (miRNA or miR) constitutes another key mechanism for the regulation of gene expression. However, whether TSH action is mediated by miRNA in the thyroid is unknown. In this study, we have performed miRNA microarray analysis and demonstrated that TSH significantly decreases expression of 47 miRNA in thyroid cells. Among these, we have shown, using their specific agonists, that overexpression of miR-16 and miR-195 suppressed cell cycle progression and DNA synthesis that was induced by TSH. In silico analysis predicted that Mapk8, Ccne1, and Cdc6, the expression of which was up-regulated by TSH, are potential target genes for these miRNA, and overexpression of miR-16 and miR-195 suppressed expression of these target genes. The decrease of miR-16 and miR-195 expression by TSH was reproduced by forskolin and N(6),2'-O-dibutyryladenosine cAMP and reversed by the protein kinase A inhibitor H89 and the PI3K inhibitor LY294002. These results suggest that TSH activates cAMP/protein kinase A and PI3K cascades to decrease miR-16 and miR-195, which induce Mapk8, Ccne1, and Cdc6 to activate cell proliferation.

Down-regulation of microRNAs controlling tumourigenic factors in follicular thyroid carcinoma

The molecular determinants of thyroid follicular nodules are incompletely understood and assessment of malignancy is a diagnostic challenge. Since microRNA (miRNA) analyses could provide new leads to malignant progression, we characterised the global miRNA expression in follicular adenoma (FA) and follicular carcinoma (FC). Comparison of carcinoma and adenoma with normal thyroid revealed 150 and 107 differentially expressed miRNAs respectively. Most miRNAs were down-regulated and especially miR-199b-5p and miR-144 which were essentially lost in the carcinomas. Integration of the changed miRNAs with differentially expressed mRNAs demonstrated an enrichment of seed sites among up-regulated transcripts encoding proteins implicated in thyroid tumourigenesis. This was substantiated by the demonstration that pre-miR-199b reduced proliferation when added to cultured follicular thyroid carcinoma cells. The down-regulated miRNAs in FC exhibited a substantial similarity with down-regulated miRNAs in anaplastic carcinoma (AC) and by gene set enrichment analysis, we observed a significant identity between target mRNAs in FC and transcripts up-regulated in AC. To examine the diagnostic potential of miRNA expression pattern in distinguishing malignant from benign nodules we employed a supervised learning algorithm and leave-one-out-cross-validation. By this procedure, FA and FC were identified with a negative predicted value of 83% (data generated by microarray platform) and of 92% (data generated by qRT-PCR platform). We conclude that follicular neoplasia is associated with major changes in miRNA expression that may promote malignant transformation by increasing the expression of transcripts encoding tumourigenic factors. Moreover, miRNA profiling may facilitate the diagnosis of carcinoma vs adenoma.

The emerging important role of microRNAs in the pathogenesis, diagnosis and treatment of human cancers

MicroRNAs are small non-protein-coding RNAs which repress gene expression, through base pair matching with messenger RNA (mRNA). A single microRNA is capable of regulating hundreds of mRNA sequences. Only a small fraction of the over 1000 discovered microRNAs have currently known functions; many are crucial in the regulation of genetic signalling, including cellular processes such as cellular differentiation, growth, proliferation and death. Dysfunction in microRNA signalling is present in all cancers studied thus far, leading to overactive oncogenic and underactive tumour suppressor gene signalling. Current research is actively pursuing the potential to use microRNAs as diagnostic tools and novel therapies in a variety of diseases. This review summarises normal and abnormal maturation and function of microRNAs and their role in the pathogenesis of various human tumours and highlights how microRNAs may be used as diagnostic and treatment tools in human cancers in the future.

MicroRNA signature in thyroid fine needle aspiration cytology applied to "atypia of undetermined significance" cases

BACKGROUND

MicroRNA (miR) expression signatures are proposed to be able to differentiate thyroid cancer from benign thyroid lesions. We selected eight miRs (miR-146b, -221, -187, -197, -346, -30d, -138, and -302c) to examine the potential use of miRs to supplement diagnostic cytology in cases designated as "atypia of undetermined significance."

METHODS

miR expression was measured in thyroid fine needle aspiration (FNA) specimens by quantitative polymerase chain reaction. Gene expression analyses and linear discriminant analysis (LDA) were performed in a training sample set (n=60) to obtain a classification rule to predict FNA cases as benign or malignant. The predictions were cross-validated by comparing with the corresponding histological diagnoses. A validation sample set (n=68) was further tested with the established four-miR LDA classification rule.

RESULTS

A set of four miRs (miR-146b, -221, -187, and -30d) was identified that could differentiate malignant from benign lesions. A four-miR LDA classification rule was obtained and used to predict FNA cases as benign or malignant. For the training sample set, we obtained a diagnostic accuracy of 93.3%, sensitivity of 93.2%, specificity of 93.8%, positive predictive value (PPV) of 0.98, and negative predictive value (NPV) of 0.83. For the validation sample set, we obtained a diagnostic accuracy of 85.3%, sensitivity of 88.9%, specificity of 78.3%, PPV of 0.89, and NPV of 0.78. For the 30 atypia cases in the validation sample set, we obtained a diagnostic accuracy of 73.3%, sensitivity of 63.6%, specificity of 78.9%, PPV of 0.64, and NPV of 0.79. Based on the miR predictions, we classified the atypia cases predicted as "malignant" into "high risk" and those predicted as "benign" into "low risk" categories. While thyroid carcinomas, particularly papillary thyroid carcinomas (PTCs), were relatively enriched in the high-risk category, this particular miR panel is subject to inaccurate results in follicular neoplasias in atypia cases.

CONCLUSIONS

We demonstrate that miR amplification from FNA samples is feasible and that the particular four miR profile in this study can identify PTCs. However, further refinement is required for application to FNA cytology of "atypia of undetermined significance" cases due to low accuracy in classifying follicular neoplasias.

MIR141 Expression Differentiates Hashimoto Thyroiditis from PTC and Benign Thyrocytes in Irish Archival Thyroid Tissues

MicroRNAs (miRNAs) are small non-coding RNAs approximately 22 nucleotides in length that function as regulators of gene expression. Dysregulation of miRNAs has been associated with initiation and progression of oncogenesis in humans. Our group has previously described a unique miRNA expression signature, including the MIR200 family member MIR141, which can differentiate papillary thyroid cancer (PTC) cell lines from a control thyroid cell line. An investigation into the expression of MIR141 in a series of archival thyroid malignancies [n = 140; classic PTC (cPTC), follicular variant PTC, follicular thyroid carcinoma, Hashimoto thyroiditis (HT), or control thyrocytes] was performed. Each cohort had a minimum of 20 validated samples surgically excised within the period 1980-2009. A subset of the HT and cPTC cohorts (n = 3) were also analyzed for expression of TGFβR1, a key member of the TGFβ pathway and known target of MIR141. Laser capture microdissection was used to specifically dissect target cells from formalin-fixed paraffin-embedded archival tissue. Thyrocyte- and lymphocyte-specific markers (TSHR and LSP1, respectively), confirmed the integrity of cell populations in the HT cohort. RNA was extracted and quantitative RT-PCR was performed using comparative CT (ΔΔCT) analysis. Statistically significant (p < 0.05) differential expression profiles of MIR141 were found between tissue types. HT samples displayed significant downregulation of MIR141 compared to both cPTC and control thyrocytes. Furthermore, TGFβR1 expression was detected in cPTC samples but not in HT thyrocytes. It is postulated that the downregulation of this miRNA is due, at least in part, to its involvement in regulating the TGFβ pathway. This pathway is exquisitely involved in T-cell autoimmunity and has previously been linked with HT. In conclusion, HT epithelium can be distinguished from cPTC epithelium and control epithelium based on the relative expression of MIR141.

microRNA-1301-mediated inhibition of tumorigenesis

The relatively recent discovery of microRNAs has added a completely new dimension to the study of the regulation of tumor cells, but how they control cell behavior remains largely elusive. HepG2 cells were assigned to the miR-1301 group and the control group. RT-PCR, Western blotting, wound healing, the Transwell chamber migration and MTT assays, and apoptosis detection assays were used to analyze cell behavior of HepG2 cells after miR-1301 mimic transfection. Our study showed that miR-1301 was downregulated in HepG2 cells, and that miR-1301 inhibited migration and invasion of HepG2 cells and promoted cellular apoptosis after transfection with miR-1301 mimics. In addition, p53 mRNA and p53 protein expression was upregulated, and Bcl-2 and Bcl-xL mRNA and protein expression was downregulated in the miR-1301 group. These results indicate that miR-1301 may be an inhibitor of tumorigenesis in HepG2 cells.

Expression profiling of difficult-to-diagnose thyroid histologic subtypes shows distinct expression profiles and identify candidate diagnostic microRNAs

BACKGROUND

The incidence of thyroid cancer is increasing worldwide. The findings of up to 30% of thyroid fine-needle aspiration biopsies (FNAB) are inconclusive, primarily as a result of several thyroid histologic subtypes with overlapping cytologic features. MicroRNAs (miRNAs) are small noncoding RNAs and have been implicated in carcinogenesis. We hypothesized that there are miRNAs that are differentially expressed between benign and malignant thyroid tumors that are difficult to distinguish by FNAB.

METHODS

The expression of 1263 human miRNAs was profiled in 47 tumor samples representing difficult to diagnose histologic subtypes of thyroid neoplasm (21 benign, 26 malignant). Differentially expressed miRNAs were validated by quantitative real-time reverse transcriptase-polymerase chain reaction. The area under the receiver operating characteristic curve (AUC) was used to determine the diagnostic accuracy of differentially expressed miRNAs.

RESULTS

Supervised hierarchical cluster analysis demonstrated grouping of 2 histologies (papillary and follicular thyroid carcinoma). A total of 34 miRNAs were differentially expressed in malignant compared to benign thyroid neoplasms (P<0.05). A total of 25 of the 34 nonproprietary miRNAs were selected for validation, and 15 of the 25 miRNAs were differentially expressed between benign and malignant samples with P-value<0.05. Seven miRNAs had AUC values of >0.7. miR-7 and miR-126 had the highest diagnostic accuracy with AUCs values of 0.81 and 0.77, respectively.

CONCLUSION

To our knowledge, this is the first study to evaluate the diagnostic accuracy of miRNAs in thyroid histologies that are difficult to distinguish as benign or malignant by FNAB. miR-126 and miR-7 had high diagnostic accuracy and could be helpful adjuncts to thyroid FNAB.

Drosha regulates hMSCs cell cycle progression through a miRNA independent mechanism

Recently we demonstrated that the miRNA regulate human mesenchymal stem cells (hMSCs) differentiation. To determine the role of the miRNA pathway in hMSCs proliferation, Drosha and Dicer knockdown hMSCs were generated using a lentiviral based tetracycline inducible shRNA. hMSCs with reduced Drosha expression had a significantly reduced proliferation rate, while hMSCs with reduced Dicer expression displayed a proliferation rate similar to untransduced cells. Cell cycle analysis identified that unlike Dicer knockdown, Drosha knockdown hMSCs contained an increased number of G1 phase cells, with a reduced level of cells in S phase, compared to controls. ELISAs of hMSCs revealed decreased levels of pRB and stable levels of total RB with Drosha knockdown. Two key regulators of the G1/S phase transition, cyclin dependent kinase inhibitor 2A (p16) and cyclin dependent kinase inhibitor 2B (p15), were increased in Drosha knockdown cells but not in Dicer knockdown. Transcripts of 28S and 18S rRNA were significantly reduced in Drosha knockdown hMSCs, with no change in rRNA levels in Dicer knockdown hMSCs. 45S pre-rRNA transcripts were not significantly different in either knockdown model. The above results indicate that Drosha modifies hMSCs proliferation through a miRNA independent mechanism, potentially by regulating rRNA processing.

Update on the molecular signature of differentiated thyroid cancer: clinical implications and potential opportunities

With the development and maturation of new technologies, there has been a steady incorporation of powerful new tools into the evaluation and management of thyroid nodules and thyroid cancer. An increasing number of reports on oncogene testing and molecular screening in fine-needle aspiration biopsy samples have been published. However, there remains a paucity of data and consensus on combining both conventional and molecular technologies to determine the diagnosis and/or prognosis of disease. All patients with differentiated thyroid cancer stand to benefit from the identification and incorporation of reliable molecular markers into clinical practice. Identification of reliable markers would allow for stratification of treatment, affording the medical and surgical teams an ability to individually tailor evaluation and treatment, applying aggressive therapy and monitoring only when clinically warranted. For the majority of patients with thyroid cancer, the incorporation of a validated, multifaceted molecular profiling system may not improve survival; however, there is great opportunity for these efforts to decrease the morbidity associated with our current approach.

MicroRNAs in thyroid cancer

CONTEXT

Traditionally, factors predisposing to diseases are either genetic ("nature") or environmental, also known as lifestyle-related ("nurture"). Papillary thyroid cancer is an example of a disease where the respective roles of these factors are surprisingly unclear.

EVIDENCE ACQUISITION

Original articles and reviews summarizing our current understanding of the role of microRNA in thyroid tumorigenesis are reviewed and evaluated.

CONCLUSION

The genetic predisposition to papillary thyroid cancer appears to consist of a variety of gene mutations that are mostly either of low penetrance and common or of high penetrance but rare. Moreover, they likely interact with each other and with environmental factors. The culpable genes may not be of the traditional, protein-coding type. A limited number of noncoding candidate genes have indeed been described, and we propose here that the failure to find mutations in traditional protein-coding genes is not coincidental. Instead, a more likely hypothesis is that changes in the expression of multiple regulatory RNA genes, e.g. microRNAs, may be a major mechanism. Our review of the literature strongly supports this notion in that a polymorphism in one microRNAs (miR-146a) predisposes to thyroid carcinoma, whereas numerous other microRNAs are involved in signaling (mainly PTEN/PI3K/AKT and T3/THRB) that is central to thyroid carcinogenesis.

Coupling Aptamers to Short Interfering RNAs as Therapeutics

RNA-based approaches are among the most promising strategies aimed at developing safer and more effective therapeutics. RNA therapeutics include small non-coding miRNAs, small interfering RNA, RNA aptamers and more recently, small activating RNAs. However, major barriers exist to the use of RNAs as therapeutics such as resistance to nucleases present in biological fluids, poor chemical stability, need of specific cell targeted delivery and easy entry into the cell. Such issues have been addressed by several recent reports that show the possibility of introducing chemical modifications in small RNAs to stabilize the molecular conformation and increase by several fold their integrity, while still preserving the functional activity. Further, several aptamers have been developed as excellent candidates for the specific recognition of cell surface targets. In the last few years, by taking advantage of recent advances in the small RNA field, molecular bioconjugates have been designed that permit specific targeting and may act as cargoes for cell internalization of small RNAs acting on gene expression that will be discussed in this review.

MicroRNA expression profiling is a potential diagnostic tool for thyroid cancer

BACKGROUND

Approximately 30% of fine-needle aspiration (FNA) biopsies of thyroid nodules are indeterminate or nondiagnostic. Recent studies suggest microRNA (miRNA, miR) is differentially expressed in malignant tumors and may have a role in carcinogenesis, including thyroid cancer. The authors therefore tested the hypothesis that miRNA expression analysis would identify putative markers that could distinguish benign from malignant thyroid neoplasms that are often indeterminate on FNA biopsy.

METHODS

A miRNA array was used to identify differentially expressed genes (5-fold higher or lower) in pooled normal, malignant, and benign thyroid tissue samples. Real-time quantitative polymerase chain reaction was used to confirm miRNA array expression data in 104 tissue samples (7 normal thyroid, 14 hyperplastic nodule, 12 follicular variant of papillary thyroid cancer, 8 papillary thyroid cancer, 15 follicular adenoma, 12 follicular carcinoma, 12 Hurthle cell adenoma, 20 Hurthle cell carcinoma, and 4 anaplastic carcinoma cases), and 125 indeterminate clinical FNA samples. The diagnostic accuracy of differentially expressed genes was determined by analyzing receiver operating characteristics.

RESULTS

Ten miRNAs showed >5-fold expression difference between benign and malignant thyroid neoplasms on miRNA array analysis. Four of the 10 miRNAs were validated to be significantly differentially expressed between benign and malignant thyroid neoplasms by quantitative polymerase chain reaction (P < .002): miR-100, miR-125b, miR-138, and miR-768-3p were overexpressed in malignant samples of follicular origin (P < .001), and in Hurthle cell carcinoma samples alone (P < .01). Only miR-125b was significantly overexpressed in follicular carcinoma samples (P < .05). The accuracy for distinguishing benign from malignant thyroid neoplasms was 79% overall, 98% for Hurthle cell neoplasms, and 71% for follicular neoplasms. The miR-138 was overexpressed in the FNA samples (P = .04) that were malignant on final pathology with an accuracy of 75%.

CONCLUSIONS

MicroRNA expression differs for normal, benign, and malignant thyroid tissue. Expression analysis of differentially expressed miRNA could help distinguish benign from malignant thyroid neoplasms that are indeterminate on thyroid FNA biopsy.

Can the microRNA signature distinguish between thyroid tumors of uncertain malignant potential and other well-differentiated tumors of the thyroid gland?

The term 'thyroid tumors of uncertain malignant potential' (TT-UMP) was coined by surgical pathologists to define well-differentiated tumors (WDT) showing inconclusive morphological evidence of malignancy or benignity. We have analyzed the expression of microRNA (miRNA) in a training set of 42 WDT of different histological subtypes: seven follicular tumors of UMP (FT-UMP), six WDT-UMP, seven follicular thyroid adenomas (FTA), 11 conventional papillary thyroid carcinomas (C-PTC), five follicular variants of PTC (FV-PTC), and six follicular thyroid carcinomas (FTC), which led to the identification of about 40 deregulated miRNAs. A subset of these altered miRNAs was independently validated by qRT-PCR, which included 18 supplementary TT-UMP (eight WDT-UMP and ten FT-UMP). Supervised clustering techniques were used to predict the first 42 samples. Based on the four possible outcomes (FTA, C-PTC, FV-PTC, and FTC), about 80% of FTA and C-PTC and 50% of FV-PTC and FTC samples were correctly assigned. Analysis of the independent set of 18 WDT-UMP by quantitative RT-PCR for the selection of the six most discriminating miRNAs was unable to separate FT-UMP from WDT-UMP, suggesting that the miRNA signature is insufficient in characterizing these two clinical entities. We conclude that considering FT-UMP and WDT-UMP as distinct and specific clinical entities may improve the diagnosis of WDT of the thyroid gland. In this context, a small set of miRNAs (i.e. miR-7, miR-146a, miR-146b, miR-200b, miR-221, and miR-222) appears to be useful, though not sufficient per se, in distinguishing TT-UMP from other WDT of the thyroid gland.

Cellular oncomiR orthologue in EBV oncogenesis

MicroRNAs are small non-coding RNAs that regulate gene expression at multiple levels. The discovery of virally encoded miRNAs attracted immense attention towards their role in viral replication and pathogenesis. Kaposi's-sarcoma-associated herpes virus encodes miRNA that functions as an orthologue of human cellular miRNA, i.e., hsa-miR-155. Keeping the same view we extended the miRNA-homology search between the miRNAs of humans and Epstein-Barr virus. The In silico analyses shows that EBV encoded miR-BART-5 has a significant 'seed' sequence homology to hsa-miR-18 of humans. Further, the mRNA transcripts of the human genes involved in cellular growth could potentially be targeted by both viral as well as human miRNAs. The known etiological role of hsa-miR-18 as an oncomiR suggests that miR-BART-5 may function as viral oncomiR as observed in EBV-positive gastric carcinoma patients.

Molecular genetics and diagnosis of thyroid cancer

Thyroid cancer is a common type of endocrine malignancy, and its incidence has been steadily increasing in many regions of the world. Initiation and progression of thyroid cancer involves multiple genetic and epigenetic alterations, of which mutations leading to the activation of the MAPK and PI3K-AKT signaling pathways are crucial. Common mutations found in thyroid cancer are point mutation of the BRAF and RAS genes as well as RET/PTC and PAX8/PPARγ chromosomal rearrangements. The mutational mechanisms seem to be linked to specific etiologic factors. Chromosomal rearrangements have a strong association with exposure to ionizing radiation and possibly with DNA fragility, whereas point mutations probably arise as a result of chemical mutagenesis. A potential role of dietary iodine excess in the generation of BRAF point mutations has also been proposed. Somatic mutations and other molecular alterations have been recognized as helpful diagnostic and prognostic markers for thyroid cancer and are beginning to be introduced into clinical practice, to offer a valuable tool for the management of patients with thyroid nodules.