Specific pattern of RAS oncogene mutations in follicular thyroid tumors

Cribriform adenocarcinoma of minor salivary glands may express galectin-3, cytokeratin 19, and HBME-1 and contains polymorphisms of RET and H-RAS proto-oncogenes

The aim of the study was to further elucidate the immunohistochemical and genetic characteristics of cribriform adenocarcinoma of minor salivary glands (CAMSG). The study comprised five CAMSG from two males and three females, aged 21-72 years. Four tumors were localized at the base of tongue and one in the floor of mouth. At the time of diagnosis, four tumors had metastasised to regional lymph nodes. After tumor resection, two patients were treated by radiotherapy and one by chemoradiotherapy. During the follow-up (median 14 months), two patients developed lymph node metastasis. Microscopically, all tumors showed cribriform, papillary, follicular, and microcystic growth patterns. The tumor cells displayed vesicular nuclei with intranuclear grooves. Immunohistochemically, all tumors showed expression of cytokeratin (CK) 7, CK8, CK18, vimentin, smooth muscle actin, calponin, S-100 protein, and p16 protein. In addition, we observed expression of galectin-3, CK19, and HBME-1, but not of thyroglobulin and TTF-1. No mutations of RET, BRAF, K-RAS, H-RAS, and N-RAS proto-oncogenes were detected. However, in RET proto-oncogene, we found polymorphisms Gly691Ser (exon 11) and Ser904Ser (exon 15) in one case, p.Leu769Leu (exon 13) in one case, and variant p.IVS14-24 G/A of intron 14 in two cases, and in H-RAS proto-oncogene we found polymorphism 81 T-C (exon 1) in three cases. Thyroglobulin and TTF-1 are the only useful markers in the differential diagnosis between CAMSG and papillary thyroid carcinoma as both tumors may express galectin-3, CK19, and HBME-1. The RET, H-RAS, and N-RAS proto-oncoogenes are not mutated in CAMSG.

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.

Diagnostic and prognostic markers in differentiated thyroid cancer

The MAPK/ERK (mitogen-activated protein kinase/extracellular signal- regulated kinase signaling pathway) and PI3K/Akt (lipid kinase phoshoinositide-3-kinase signaling pathway) play an important role in transmission of cell signals through transduction systems as ligands, transmembrane receptors and cytoplasmic secondary messengers to cell nucleus, where they influence the expression of genes that regulate important cellular processes: cell growth, proliferation and apoptosis. The genes, coding the signaling cascade proteins (RET, RAS, BRAF, PI3K, PTEN, AKT), are mutated or aberrantly expressed in thyroid cancer derived from follicular thyroid cell. Genetic and epigenetic alternations, concerning MAPK/ERK and PI3K/Akt signaling pathways, contribute to their activation and interaction in consequence of malignant follicular cell transformation. Moreover, it is additionally pointed out that genetic, as well as epigenetic DNA changing via aberrant methylation of several tumor suppressor and thyroid-specific genes is associated with tumor aggressiveness, being a jointly responsible mechanism for thyroid tumorigenesis. In the present manuscript the currently developed diagnostic and prognostic genetic/epigenetic markers are presented; the understanding of this molecular mechanism provides access to novel molecular therapeutic strategies.

RET/PTC rearrangement is prevalent in follicular Hürthle cell carcinomas

AIMS

The molecular alterations underlying follicular Hürthle cell carcinomas (FHCCs) are largely unknown. In an attempt to clarify this issue, we analysed a series of Hürthle cell tumours for the presence of RET/PTC and PAX8/PPARG rearrangements and BRAF, HRAS and NRAS mutations.

METHODS AND RESULTS

We investigated a series of 20 follicular Hürthle cell tumours [17 FHCCs and three follicular Hürthle cell adenomas (FHCAs)]. RET/PTC rearrangements were found in 33% of FHCAs and in 38% of FHCCs. All RET/PTC-positive FHCCs had a solid pattern of growth. PAX8/PPARG rearrangement was present in 27% of the FHCCs which displayed, in most cases, a follicular architecture. NRAS mutation was detected in one FHCC. An FHCC with a solid/microfollicular growth pattern scored positive for both RET/PTC and PAX8/PPARG rearrangement.

CONCLUSIONS

Our study has shown a significant association between RET/PTC rearrangements and FHCCs with a solid growth pattern, thus raising the possibility of using tyrosine kinase inhibitors for the treatment of patients with FHCCs, which are often refractory to radioiodine treatment.

The associations between RAS mutations and clinical characteristics in follicular thyroid tumors: new insights from a single center and a large patient cohort

BACKGROUND

Many studies on thyroid follicular tumors have reported the presence of somatic mutations to three forms of RAS: HRAS, KRAS, and NRAS. However, the frequency and clinical significance of these RAS mutations remain unclear, in large part due to the different methodologies being used for mutation analysis and the limited number of cases featured in studies. To clarify the significance of RAS mutations, we examined a large number of follicular adenomas and carcinomas obtained from a single institute using established methods for the analysis of RAS.

METHODS

Tumor samples from 40 follicular adenoma and 58 follicular carcinoma patients treated at the Kanagawa Cancer Center Hospital were analyzed. The three RAS mutations at codons 12 and 61 were assessed with a polymerase chain reaction-based loop-hybrid mobility shift assay followed by confirmation with direct sequencing. The relationships between mutation status and clinicopathological features at the time of the initial operation and the prognosis of the patients were also analyzed.

RESULTS

Twelve out of 40 (30%) adenomas harbored RAS mutations. In contrast, 33 out of 58 (57%) follicular carcinomas harbored RAS mutations, and the mutation was predominantly found in the NRAS codon 61 (22/33, 67%, p<0.01). The rate of gene mutations was significantly higher in the carcinomas than in the adenomas (p<0.01). The NRAS codon 61 mutation in follicular carcinomas was positively associated with distant metastases through the entire clinical course of the patients (p<0.05), and RAS mutations were associated with poor overall patient survival (p<0.05).

CONCLUSIONS

We investigated the frequency of RAS mutations in follicular thyroid tumors from a large number of cases obtained from a single institute. The predominance of NRAS codon 61 mutations as a feature of carcinomas indicates that the diagnosis of adenoma alongside the presence of this mutation should be made cautiously. Our study raises the possibility that follicular adenomas with the RAS mutations have an inherent malignant potential; however, the clinical significance of this finding should be further investigated in more patients and over a longer follow-up period.

A high-resolution melting protocol for rapid and accurate differential diagnosis of thyroid nodules

A large majority of thyroid nodules are benign, and only 5% have malignant features on cytological examination. Unfortunately, fine-needle aspiration is inconclusive in approximately 30% of all thyroid biopsies, because the cytological features are indeterminate (suspicious for malignancy but not completely diagnostic or nondiagnostic). Wide panels of somatic mutations have been identified in thyroid cancers, and detection of genetic alterations in fine-needle aspirate has been demonstrated to improve diagnostic accuracy. Nevertheless, the relatively high number of genetic targets to be investigated, in comparison with the low percentage of malignant samples, makes the usual diagnostic protocol both time-consuming and expensive. We developed a reliable and sensitive protocol based on high-resolution melting analysis for the rapid screening of mutations of KRAS, HRAS, NRAS, and BRAF oncogenes in thyroid fine-needle aspirations. The entire procedure can be completed in approximately 48 hours, with a dramatic reduction in costs. The proposed protocol was applied to the analysis of 260 consecutive fine-needle aspiration biopsy (FNAB) samples. In 35 of 252 samples, 36 sequence variants were detected for BRAF (17 samples), NRAS (6 samples), HRAS (3 samples), KRAS codon 12 (9 samples), and KRAS codon 61 (1 sample).

Unilateral follicular variant of papillary thyroid carcinoma with unique KRAS mutation in struma ovarii in bilateral ovarian teratoma: a rare case report

Background

Struma ovarii (SO) is a rare form of ovarian mature teratoma in which thyroid tissue is the predominant element. Because of its rarity, the differential diagnosis between benign and malignant SO has not been clearly defined. It is believed that malignant transformation of SO has similar molecular features with and its prognosis corresponds to that of malignant tumors originating in the thyroid.

Case presentation

We report 35-year-old woman with bilateral ovarian cysts incidentally detected by ultrasound during the first trimester of pregnancy. Four months after delivery of a healthy child without complication she was admitted to the hospital for acute abdominal pain. Laparoscopic left adnexectomy was performed initially in a regional hospital; right cystectomy was done later in a specialized clinic. Intraoperative frozen section and a final pathology revealed that the cyst from the left ovary was composed of mature teratomatous elements, normal thyroid tissue (>50%) and a non-encapsulated focus of follicular variant of papillary thyroid carcinoma (PTC).

Normal and cancerous thyroid tissues were tested for BRAF and RAS mutations by direct sequencing, and for RET/PTC rearrangements by RT-PCR/Southern blotting. A KRAS codon 12 mutation, the GGT → GTT transversion, corresponding to the Gly → Val amino acid change was identified in the absence of other genetic alterations commonly found in PTC.

Conclusion

To the best of our knowledge, this is the first time this mutation is described in a papillary thyroid carcinoma arising in struma in the ovarii. This finding provides further evidence that even rare mutations specific for PTC may occur in such tumors. Molecular testing may be a useful adjunct to common differential diagnostic methods of thyroid malignancy in SO.

Follicular variant of papillary thyroid cancer: encapsulated, nonencapsulated, and diffuse: distinct biologic and clinical entities

OBJECTIVE

To examine genotypic and clinical differences between encapsulated, nonencapsulated, and diffuse follicular variant of papillary thyroid carcinoma (EFVPTC, NFVPTC, and diffuse FVPTC, respectively), to characterize the entities and identify predictors of their behavior.

DESIGN

Retrospective medical chart review and molecular analysis.

SETTING

Referral center of a university hospital.

PATIENTS

The pathologic characteristics of 484 consecutive patients with differentiated thyroid cancer who underwent surgery by the 3 members of the New York University Endocrine Surgery Associates from January 1, 2007, to August 1, 2010, were reviewed. Forty-five patients with FVPTC and in whom at least 1 central compartment lymph node was removed were included.

MAIN OUTCOME MEASURES

Patients with FVPTC were compared in terms of age, sex, tumor size, encapsulation, extrathyroid extension, vascular invasion, central nodal metastases, and the presence or absence of mutations in BRAF, H-RAS 12/13, K-RAS 12/13, N-RAS 12/13, H-RAS 61, K-RAS 61, N-RAS 61, and RET/PTC1.

RESULTS

No patient with EFVPTC had central lymph node metastasis, and in this group, 1 patient (4.5%) had a BRAF V600E mutation and 2 patients (9%) had RAS mutations. Of the patients with NFVPTC, none had central lymph node metastasis (P > .99) and 2 (11%) had a BRAF V600E mutation (P = .59). Of the patients with diffuse FVPTC, all had central lymph node metastasis (P < .001), and 2 (50%) had a BRAF V600E mutation (P = .06).

CONCLUSIONS

FVPTC consists of several distinct subtypes. Diffuse FVPTC seems to present and behave in a more aggressive fashion. It has a higher rate of central nodal metastasis and BRAF V600E mutation in comparison with EFVPTC and NFVPTC. Both EFVPTC and NFVPTC behave in a similar fashion. The diffuse infiltrative pattern and not just presence or absence of encapsulation seems to determine the tumor phenotype. Understanding the different subtypes of FVPTC will help guide appropriate treatment strategies.

The pituitary tumor transforming gene in thyroid cancer

The pituitary tumor transforming gene (PTTG) is a multifunctional proto-oncogene that is over-expressed in various tumors including thyroid carcinomas, where it is a prognostic indicator of tumor recurrence. PTTG has potent transforming capabilities in vitro and in vivo, and many studies have investigated the potential mechanisms by which PTTG contributes to tumorigenesis. As the human securin, PTTG is involved in critical mechanisms of cell cycle regulation, whereby aberrant expression induces aneuploidy. PTTG may further contribute to tumorigenesis through its role in DNA damage response pathways and via complex interactions with hormones and growth factors. Furthermore, PTTG over-expression negatively impacts upon the efficacy of radioiodine therapy in thyroid cancer, through repression of expression and function of the sodium iodide symporter. Given its various roles at all disease stages, PTTG appears to be an important oncogene in thyroid cancer. This review discusses the current knowledge of PTTG with particular focus on its role in thyroid cancer.

Approach to and treatment of differentiated thyroid carcinoma

Thyroid cancer is the most common endocrine malignancy, although representing fewer than 1% of all human tumors. Differentiated thyroid carcinoma (DTC) includes the papillary and follicular histotypes and their variants, accounting for more than 90% of all thyroid cancers. Given the changing presentation of DTC in the last years, the aim of DTC management is to ensure the most effective but least invasive treatment, and adequate follow-up for a disease that nowadays is mostly cured just with surgery and is rarely fatal. This review addresses the multiple steps of current management, based on previous assumptions.

Targeting the MAPK-RAS-RAF signaling pathway in cancer therapy

INTRODUCTION

The MAPK pathway comprises several key signaling components and phosphorylation events that play a role in tumorigenesis. These activated kinases transmit extracellular signals that regulate cell growth, differentiation, proliferation, apoptosis and migration functions. Alteration of the RAS-RAF-MEK-ERK-MAPK (RAS-MAPK) pathway has been reported in human cancer as a result of abnormal activation of receptor tyrosine kinases or gain-of-function mutations mainly in the RAS or RAF genes. These pathways are considered potential therapeutic targets for cancer treatment. Recently, several small-molecule inhibitors targeting this pathway have been developed and are currently being tested in clinical trials.

AREAS COVERED

The biological role of the RAS-MAPK pathway, the consequence of its disregulation and the development of small-molecule inhibitors. The rationale for targeting the RAS-MAPK pathway and the application and the results of various inhibitory molecules as anticancer agents in clinical trials.

EXPERT OPINION

Inhibitors of MEK and particularly of RAF kinases have shown effectiveness in clinical trials with manageable side effects. RAS and BRAF genes need to be analyzed for mutations as markers of response to treatments and to avoid paradoxical effects. Further characterization of the RAS-MAPK molecular mechanisms regulation in malignant cells or underlying the acquired resistance to RAF inhibitors will facilitate development of novel combination therapies.

Gene expression profile of human thyroid cancer in relation to its mutational status

This review describes the gene expression profile changes associated with the presence of different mutations that contribute to thyroid cell carcinogenesis. The results are discussed in the context of thyroid cancer biology and of the implications for disease prognosis, while the diagnostic aspect has been omitted. For papillary thyroid cancer (PTC), the most characteristic gene expression profile is associated with the presence of BRAF mutation. BRAF-associated PTC differ profoundly from RET/PTC or RAS-associated cancers. Simultaneously, they retain many characteristic gene expression features common for all PTCs, induced by the alternative mutations activating MAPK pathway. Although the difference between papillary and follicular thyroid cancer (FTC) is significant at the gene expression profile level, surprisingly, the RAS-related signature of FTC is not well specified. PAX8/peroxisome proliferator-activated receptor γ (PPARγ) rearrangements, which occur in FTC as an alternative to the RAS mutation, are associated with specific changes in gene expression. Furthermore, the difference between well-differentiated thyroid cancers and poorly differentiated and anaplastic thyroid cancers is mainly a reflection of tumor degree of differentiation and may not be attributed to the presence of characteristic mutations.

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.

Dissecting molecular events in thyroid neoplasia provides evidence for distinct evolution of follicular thyroid adenoma and carcinoma

Benign hypofunctional cold thyroid nodules (CTNs) are a frequent scintiscan finding and need to be distinguished from thyroid carcinomas. The origin of CTNs with follicular morphologic features is unresolved. The DNA damage response might act as a physiologic barrier, inhibiting the progression of preneoplastic lesions to neoplasia. We investigated the following in hypofunctional follicular adenoma (FA) and follicular thyroid cancer (FTC): i) the mutation rate of frequently activated oncogenes, ii) the activation of DNA damage response checkpoints, and iii) the differential proteomic pattern between FA and FTC. Both FTC and FA, which did not harbor RAS, phosphoinositide-3-kinase, or PAX/peroxisome proliferator activated receptor-γ mutations, express various proteins in common and others that are more distinctly expressed in FTC rather than in FA or normal thyroid tissue. This finding is in line with the finding of constitutive DNA damage checkpoint activation (p-Chk2, γ-H2AX) and evidence for replicative stress causing genomic instability (increased cyclin E, retinoblastoma, or E2F1 mRNA expression) in FTC but not FA. We discuss the findings of the increased expression of translationally controlled tumor protein, phosphatase 2A inhibitor, and DJ-1 in FTC compared with FA identified by proteomics and their potential implication in follicular thyroid carcinogenesis. Our present findings argue for the definition of FA as a truly benign entity and against progressive development of FA to FTC.

Thyroid cancer: pathogenesis and targeted therapy

Therapeutic options for advanced, unresectable radioiodine-resistant thyroid cancers have historically been limited. Recent progress in understanding the pathogenesis of the various subtypes of thyroid cancer has led to increased interest in the development of targeted therapies, with potential strategies including angiogenesis inhibition, inhibition of aberrant intracellular signaling in the MAPK and PI3K/AKT/mTOR pathways, radioimmunotherapy, and redifferentiation agents. On the basis of a recent positive phase III clinical trial, the RET, vascular endothelial growth factor receptor (VEGFR), and epidermal growth factor receptor (EGFR) inhibitor vandetanib has received FDA approval as of April 2011 for use in the treatment of advanced medullary thyroid cancer. Several other recent phase II clinical trials in advanced thyroid cancer have demonstrated significant activity, and multiple other promising therapeutic strategies are in earlier phases of clinical development. The recent progress in targeted therapy is already revolutionizing management paradigms for advanced thyroid cancer, and will likely continue to dramatically expand treatment options in the coming years.

Analysis of the efficacy and toxicity of sorafenib in thyroid cancer: a phase II study in a UK based population

AIM

To evaluate the tolerability and efficacy of sorafenib in patients with thyroid carcinoma.

METHODS

Patients with progressive locally advanced/metastatic medullary thyroid carcinoma (MTC), or differentiated thyroid carcinoma (DTC) with non-radioiodine-avid disease, were treated with sorafenib 400 mg twice daily until disease progression. The primary endpoint was the radiological response rate (RR) at 6 months. Secondary endpoints were RR at 3, 9 and 12 months, biochemical responses, toxicity, biomarker analyses and progression free and overall survival (OS).

RESULTS

A total of 34 patients were recruited to the study (15 medullary and 19 differentiated). After 6 months, the RR rate was 15% and a further 74% of patients achieved stable disease in the first 6 months. After 12 months of treatment, the RR was 21%. In the MTC patients, the RR at 12 months was 25% and OS was 100%. In DTC patients corresponding rates were 18 and 79% respectively. Median overall and progression-free survival points were not reached at 19 months. Commonest adverse events included hand-foot syndrome, other skin toxicities, diarrhoea and alopecia. Dose reduction was required in 79% patients. Median time on treatment was 16.5 months.

CONCLUSION

This study demonstrates that sorafenib is tolerable at reduced doses over prolonged periods of time in patients with thyroid cancer. Sorafenib leads to radiological and biochemical stabilisation of disease in the majority of these patients despite dose reductions.

Telomere length is related to alternative splice patterns of telomerase in thyroid tumors

Telomere dysfunction and aberrant telomerase expression play important roles in tumorigenesis. In thyroid tumors, three possibly inhibitory splice variants of the active full-length isoform of human telomerase reverse transcriptase (hTERT) may be expressed. These variants might regulate telomerase activity and telomere length because it is the fraction of the full-length isoform, rather than the total transcript level, that correlates with enzymatic activity. Telomerase reactivation may be critical in the early stages of tumorigenesis, when progressive telomere shortening may be limiting cell viability. The aim of this study was to investigate the relationship between telomere length and hTERT splice variant expression patterns in benign and well-differentiated malignant thyroid tumors. Telomere lengths of 61 thyroid tumors were examined by fluorescence in situ hybridization, comparing tumors with adjacent normal thyroid tissue on the same slide. Expression patterns of hTERT splice variants were evaluated by quantitative and nested RT-PCR. Telomere length was inversely correlated with percentage of full-length hTERT expression rather than with total hTERT expression levels. Short telomeres and high fractions of full-length hTERT transcripts were associated with follicular and papillary thyroid carcinomas, whereas long telomeres and low levels of full-length hTERT were associated with benign thyroid nodules. Intermediate levels of full-length hTERT and telomere length were found in follicular variant of papillary thyroid carcinomas and follicular adenomas.

The role of epigenetic alterations in papillary thyroid carcinogenesis

Papillary thyroid carcinoma (PTC) accounts for over 80% of all thyroid malignancies. The molecular pathogenesis remains incompletely clarified although activation of the RET fusion oncogenes, and RAS and BRAF oncogenes, has been well characterized. Novel technologies using genome-wide approaches to study tumor genomes and epigenomes have provided great insights into tumor development. Growing evidence shows that acquired epigenetic abnormalities participate with genetic alterations to cause altered patterns of gene expression/function. It has been established beyond doubt that promoter cytosine methylation in CpG islands, and the subsequent gene silencing, is intimately involved in cancer development. These epigenetic events very likely contribute to significant variation in gene expression profiling, phenotypic features, and biologic characteristics seen in PTC. Hypermethylation of promoter regions has also been analyzed in PTC, and most studies have focused on individual genes or a small cohort of genes implicated in tumorigenesis.

Recent advances in molecular diagnosis of thyroid cancer

Recent molecular studies have described a number of abnormalities associated with the progression and dedifferentiation of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development. In particular, remarkable advances have occurred in several major biological areas of thyroid cancer, including the molecular alterations for the loss of radioiodine avidity of thyroid cancer, the pathogenic role of the MAP kinase and PI3K/Akt pathways and their related genetic alterations, and the aberrant methylation of functionally important genes in thyroid tumorigenesis and pathogenesis. Recognition of these features is crucial to the management of patients with thyroid cancer. Novel treatments are being designed based on our enhanced understanding of this disease process.

Well differentiated follicular thyroid neoplasia: impact of molecular and technological advances on detection, monitoring and treatment

Our understanding of the molecular mechanisms responsible for follicular thyroid cell oncogenesis has been advanced significantly in recent years. Specific genetic alterations and the molecular pathways they affect have been associated with particular histologic subtypes of well-differentiated thyroid cancer and are now being evaluated for their utility as clinical tools with diagnostic, prognostic and even therapeutic relevance. This paper focuses on the most common and clinically relevant genetic alterations shown to be consistently associated with well-differentiated thyroid carcinoma. We review the impact of recent molecular and technological advances on thyroid cancer standard of care and the practice of clinical medicine.

Mutational and clinico-pathological analysis of papillary thyroid carcinoma in Serbia

Molecular pathogenesis of papillary thyroid carcinoma (PTC) is largely associated with mutational changes in the BRAF, RAS family and RET genes. Our aim was to assess clinico-pathological and prognostic correlations of these PTC-specific gene alterations, with a particular emphasis on the BRAF mutation, in a group of 266 Serbian PTC patients, for the first time. The reference center-based retrospective cohort included 201 (75.6%) females and 65 (24.4%) males aged 48.0±16.1 years (8-83 years old, range) diagnosed and treated for PTC during 1993-2008. Follow-up period was 53.1±41.6 months (7-187 months, range). BRAF and RAS mutations were determined by direct sequencing of genomic DNA. RET/PTC rearrangements were analyzed by RT-PCR/Southern blotting. Genetic alterations were detected in 150/266 tumors (56.4%). One tumor displayed two genetic alterations. The BRAF(V600E) was found in 84/266 (31.6%) cases, RAS mutations in 11/266 (4.1%) and RET/PTC in 55/266 (20.7%; 42/266 (15.8%) RET/PTC1 and 13/266 (4.9%) RET/PTC3). On multivariate analysis BRAF(V600E) was associated with the classical papillary morphology (P = 0.05), the higher pT category (P = 0.05) and advanced clinical stage (P = 0.03). In a proportional hazard model, BRAF(V600E) did not appear to be an independent risk factor for the faster recurrence (P = 0.784). We conclude that under the extensive thyroid surgery and limited application of radioiodine ablation BRAF(V600E) may not be an indicator of poorer disease-free survival during the short to middle follow-up period. However, it has a potential to contribute to patients stratification into high- and low-risk groups.

Prevalence of RET/PTC rearrangement in benign and malignant thyroid nodules and its clinical application

Fine-needle aspiration cytology (FNAC) is the primary means to distinguish benign thyroid nodules from malignant ones. About 20% of FNAC yields indeterminate results leading to unnecessary or delayed surgery. Many studies of tissue samples, the majority of which are retrospective advocate testing for RET rearrangements as a diagnostic adjunctive tool in thyroid nodules with indeterminate cytological findings. Because of the uncertain prevalence of RET rearrangements, its utility as a tumor marker is still controversial. The goal of this study was to establish the prevalence and the utility of testing for RET rearrangements in FNAC suspicious of cancer in a clinical setting. In this prospective study, we analysed a large series of thyroid aspirates by RT-PCR only and Southern blot on RT-PCR products for type 1 and 3 RET rearrangements. Results were compared with clinical findings, cytological diagnosis and final histopathology. By the higher sensitive Southern-blot on RT-PCR method, RET rearrangements were present in 36% of papillary thyroid carcinomas (RET/PTC-1, 12%; RET/PTC-3, 20%; both, 4%) and of 13.3% of benign nodules. By means of RT-PCR only, RET rearrangements were disclosed only in 14.3% of PTC and in 3.6% of benign nodules. No significant correlation was found between RET rearrangements and clinicopathological features of patients. These results indicate that molecular testing of thyroid nodules for RET/PTC must take into account of its high prevalence in benign nodules, inducing false positive diagnoses when the highly sensitive assay Southern-blot on RT-PCR is used. Its searching by means of RT-PCR only, has a specificity superior of conventional cytology and can be used to refine inconclusive FNAC.

Identification of several novel non-p.R132 IDH1 variants in thyroid carcinomas

CONTEXT

Somatic mutations at residue R132 of isocitrate dehydrogenase 1 (IDH1) were recently discovered in gliomas and leukaemia at a high frequency. IDH1 is a metabolic gene, and the R132 mutations create a new enzymatic activity.

OBJECTIVES

To determine whether IDH1 had somatically acquired mutations in thyroid carcinomas.

DESIGN

Exons 4 and 6 of IDH1 were sequenced in a large panel of thyroid tumours (n=138) and compared with the patients normal DNA (n=26). We also correlated IDH1 mutations with clinical-pathological data and BRAF and RAS mutational status.

RESULTS

We identified four novel and two previously described non-synonymous variants in thyroid carcinomas, which were absent in benign tumours and paired normal thyroid. Although IDH1 variants occurred at higher frequency in follicular thyroid carcinomas, follicular variant of papillary thyroid carcinoma (PTC) and undifferentiated thyroid carcinomas than the observed variants in classical PTC (15/72 vs 3/37), it was not significant (P=0.1). Sequence alignment across several species shows that all IDH1 genetic alterations occurred at evolutionarily conserved residues located within the active site, and therefore, are likely to affect protein function. Unlike other tumours, IDH1 and BRAF or RAS mutations are not mutually exclusive. There was no association between IDH1 mutational status and clinical characteristics.

CONCLUSION

IDH1-acquired genetic alterations are highly prevalent in thyroid carcinomas (16%). Our findings not only extend our understanding of the molecular mechanism underlying pathogenesis of thyroid tumours, but also emphasize the biological differences between tumour types. Those tumours with IDH1 mutations might benefit from therapies that exploit this alteration.

Importance of Hormones and Proteins Determination in the Material Obtained by Fine-Needle Aspiration

More than a half century of experience with aspiration punch of nodal changes in the thyroid gland has confirmed this procedure as a golden standard in the examination of thyroid nodal disease. Although sensitivity, specificity, reliability and reproducibility are incontestably high, this procedure cannot give a simple answer on whether the change examined is benign or malignant. Numerous attempts to improve the procedure resulted in considerably advanced findings. Besides refining the cytopathologic examination techniques, confirmation or determination of hormones, proteins and other substances in the material obtained by fine-needle aspiration are actually the greatest contribution to improvement the of procedure's diagnostic value. These markers are actually followed, in most medical centers, in aspirates of thyroid nodal changes but also surrounding lymph nodes in order to evaluate with greater certainty the type, volume and spread; this is important to establish treatment procedures and to evaluate the residual disease after accomplishing the treatment.

Targeted molecular therapies in thyroid carcinoma

Thyroid cancer incidence has significantly increased in the last three decades and many patients seek medical attention for its treatment every year. Among follicular cell-derived tumors, the majority are differentiated thyroid carcinomas (DTC), whose prognosis is very good with only 15% of the cases presenting disease persistence or recurrence after initial treatment. Medullary thyroid carcinoma has a worse prognosis, especially in patients with diffused cancers at the time of initial surgery. Traditional treatment options for persistent or recurrent disease include additional surgery, radioiodine treatment and TSH-suppression in DTC patients; external beam radiotherapy, and cytotoxic chemotherapy, often have low efficacy and many patients with advanced disease ultimately die. In the last two decades many of the molecular events involved in cancer formation have been uncovered. This knowledge has prompted the development of novel therapeutic strategies mainly based on the inhibition of key molecular mediators of the tumorigenic process. In particular the class of small-molecule tyrosine kinase inhibitors was enriched by many compounds that have reached clinical trials and in some cases have had approval for clinical use in specific cancers. Many of these compounds entered clinical trials also for locally advanced or metastatic thyroid carcinomas showing very promising results.

Genetic alterations in the RAS/RAF/mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt signaling pathways in the follicular variant of papillary thyroid carcinoma

BACKGROUND

The follicular variant of papillary thyroid carcinoma (FVPTC) is the second most common histotype among papillary thyroid cancers (PTCs). Although the prognosis of FVPTC is similar to the conventional phenotype, differential diagnostic difficulties may not be uncommon with other follicular thyroid neoplasms, and little is known about their genetic alterations. Defining these alterations may lead to the identification of diagnostic and biologic markers.

METHODS

In this study, the authors evaluated genetic alterations and downstream-activated signals of the Ras/Raf-mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene (Akt) (PI3K/Akt) signaling pathways in 30 FVPTC tissue specimens. Tumors and matched normal thyroid samples were tested for RAS, for the v-raf murine sarcoma viral oncogene (BRAF) substitution of valine (V) for glutamate (E) at codon 600 (the V600E mutation), for phosphatase and tensin homolog (PTEN), for catalytic PI3k p110 subunit alpha (PIK3CA), for AKT, and for the presence of rearranged during transfection (ret) proto-oncogene/PTC (RET-PTC) and paired box-8 (PAX8)/peroxisome proliferator-activated receptor gamma (PPARgamma) fusion protein (PAX8-PPARgamma) rearrangements by direct sequencing and reverse transcriptase-polymerases chain reaction analyses, respectively. Western blot analysis was used to assess the effects of these gene abnormalities on the activation of the 2 pathways.

RESULTS

Genetic alterations were identified in 70% of FVPTCs. Activation of the MAPK and PI3K pathways was observed in 74% and 22% of tumors, respectively. The alterations that were identified in the genes of the 2 pathways were mutually exclusive. Chromosomal RET-PTC and PAX8-PPARgamma rearrangements were observed in 20% and 17% of tumors, respectively. It was noteworthy that some FVPTCs with RET-PTC had the coactivation of both pathways.

CONCLUSIONS

RET-PTC and PAX8-PPARgamma rearrangements and mutations of the neuroblastoma RAS viral oncogene homolog N-RAS at codon 61 were the most common genetic alterations in FVPTCs. Activation of the MAPK pathway was a frequent event in FVPTCs, and the PI3K signaling pathway could be coactivated in RET-PTC tumors. These findings may have important therapeutic implication in patients with FVPTC.

Genetic alterations in the phosphatidylinositol-3 kinase/Akt pathway in thyroid cancer

BACKGROUND

Aberrant activation of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway plays a fundamental role in thyroid tumorigenesis, particularly in follicular thyroid cancer (FTC) and aggressive thyroid cancer, such as anaplastic thyroid cancer (ATC). As the drivers of this process, many genetic alterations activating the PI3K/Akt pathway have been identified in thyroid cancer in recent years.

SUMMARY

This review summarizes the current knowledge on major genetic alterations in the PI3K/Akt pathway. These include PIK3CA mutations and genomic amplification/copy gain, Ras mutations, PTEN mutations, RET/PTC and PPARgamma/Pax8 rearrangements, as well as amplification/copy gain of PIK3CB, PDK1, Akt, and various receptor tyrosine kinase genes. Most of these genetic alterations are particularly common in FTC and many of them are even more common in ATC; they are generally less common in papillary thyroid cancer (PTC), in which the MAP kinase (MAPK) pathway activated by the BRAF mutation instead plays a major role. Methylation and, thus, epigenetic silencing of PTEN, a major negative regulator of the PI3K/Akt pathway, occurs in close association with activating genetic alterations of the PI3K/Akt pathway, constituting a unique self-enhancement mechanism for this pathway. Many of these genetic alterations are mutually exclusive in differentiated thyroid tumors, but with increasing concurrence from benign tumors to FTC to ATC. RET/PTC, Ras, and receptor tyrosine kinase could dually activate the PI3K/Akt and MAPK pathways. Most cases of ATC harbor genetic alterations in these genes or other genetic combinations that can activate both pathways. It is proposed that genetic alterations in the PI3K/Akt pathway promote thyroid cell transformation to FTC and that genetic alterations in the MAPK pathway promote cell transformation to PTC; accumulation of multiple genetic alterations that can activate both pathways promotes thyroid cancer aggressiveness and progression to ATC.

CONCLUSIONS

Genetic alterations are common in the PI3K/Akt pathway in thyroid cancer and play a fundamental role in the tumorigenesis and progression of this cancer. This provides a strong basis for the emerging development of novel genetic-based diagnostic, prognostic, and therapeutic strategies for thyroid cancer.

Absence of BRAF, NRAS, KRAS, HRAS mutations, and RET/PTC gene rearrangements distinguishes dominant nodules in Hashimoto thyroiditis from papillary thyroid carcinomas

Dominant nodules within Hashimoto thyroiditis (HT) may present with unique morphological features that overlap with but are not diagnostic of papillary thyroid carcinoma (PTC). Activating BRAF point mutations, RAS aberrations, and RET rearrangements are mutually exclusive events in the oncogenesis of papillary thyroid carcinoma, and RET rearrangements have been previously described in dominant nodules of HT. We identified 28 cases of Hashimoto thyroiditis with a dominant nodule, from 345 consecutive HT thyroidectomies. Screening for BRAF, RET, KRAS, NRAS, and HRAS mutations, as well as RET-PTC1 and RET-PTC3 rearrangements, was performed on paraffin-embedded material from 17 of these dominant nodules. Patients ranged in age from 29 to 76 years and were predominantly female, and the nodules ranged from 1.5 to 6.2 cm. No BRAF or RAS mutations or RET-PTC rearrangements were identified in a dominant nodule, including those with atypical, worrisome histopathologic features. Of ten cases with diagnostic concomitant or incidental papillary carcinoma, three had a V600E point mutation in BRAF, and one case had a BRAF exon 15 deletion (600-604E), while the dominant nodules were negative for mutation, supporting the notion that dominant nodules are neither malignant nor precursor lesions, and strict histological, clinical, and molecular criteria must be met for the diagnosis of papillary thyroid carcinoma.

Genetic markers differentiating follicular thyroid carcinoma from benign lesions

Thyroid nodules are commonly encountered during routine medical care. The main problem established by a discovery of a thyroid nodule is to discriminate between a benign and malignant lesion. Fine-needle aspiration (FNA) is the most widely used and cost-effective preoperative test for initial evaluation of a thyroid nodule. While the overall accuracy of FNA for classical papillary thyroid carcinoma (PTC) approaches 100%, it has limited accuracy with follicular lesions. Patients with a cytological report of indeterminate or follicular lesions are referred to surgery for a more accurate diagnosis. A more acute molecular-based test for thyroid nodules is needed not only to improve treatment decisions, but also to potentially reduce the long-term health costs. Several studies have looked into biologic markers that could be used as an adjuvant to distinguish the benign from malignant nodules. This review will focus on those biomarkers that are potentially useful in the diagnosis of thyroid lesions commonly classified as indeterminate.

Concurrent occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma in the same thyroid should be considered as coincidental

OBJECTIVES

The simultaneous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) in the same thyroid gland is documented. In this study, we evaluated the prevalence and characteristics of patients with concurrent MTC and PTC. Design Retrospective analysis of patients with MTC in a single centre and review of the literature.

PATIENTS AND MEASUREMENTS

Patients with MTC who underwent initial surgical treatment between 1996 and 2006 at Asan Medical Centre, Seoul, Korea were enrolled. We additionally reviewed the medical records of patients who initially underwent surgery for Graves' disease (GD) or follicular thyroid carcinoma (FTC) during the same period. The concurrent occurrence rate of PTC in MTC patients was compared with that in GD and FTC patients.

RESULTS

Ten of 53 (19%) MTC patients displayed the concomitant PTC. In all 10 cases, the MTC and PTC components were separated by normal thyroid tissue, with the maximal diameters of PTC being less than 1.0 cm in the majority of patients. The rates of concurrent PTC in patients with MTC, GD and FTC were 19%, 15% and 19%, respectively, which were not significantly different.

CONCLUSIONS

Our results suggest that the occurrence of concurrent MTC/PTC is generally a simple reflection of incidental papillary microcarcinoma.

Evaluation of the PAX8/PPARG translocation in follicular thyroid cancer with a 4-color reverse-transcription PCR assay and automated high-resolution fragment analysis

BACKGROUND

Molecular testing of thyroid malignancies, in combination with cytologic and histologic examination, is becoming increasingly attractive as a tool for refining traditional morphologic diagnosis. The molecular changes associated with follicular thyroid carcinoma (FTC) are point mutations in RAS oncogenes or the presence of PAX8/PPARG (paired box 8/peroxisome proliferator-activated receptor gamma) rearrangement.

METHODS

We developed and validated a clinical assay for the detection of PAX8/PPARG rearrangements that uses a 4-color reverse-transcription PCR (RT-PCR) assay and high-resolution fragment analysis.

RESULTS

The RT-PCR assay is applicable for detecting the various described fusion transcripts of PAX8/PPARG in formalin-fixed, paraffin-embedded thyroid tissue and in fine-needle aspirate biopsy washes from thyroid nodules. The analytical sensitivity of the assay is 1 abnormal cell in a background of 100-10 000 translocation-negative cells. A comparison of the RT-PCR assay with dual-fusion fluorescence in situ hybridization showed an overall concordance of 95%. With this assay, we obtained a prevalence for the PAX8/PPARG rearrangement in FTC of 62% (13 of 21 cases), compared with a 5% prevalence (3 of 55) for other follicular cell-derived neoplasms.

CONCLUSIONS

The introduction of this assay into clinical practice could provide useful information for the diagnosis and possibly for the prognosis and treatment of thyroid cancer in the future.

Differential miRNA expression profiles in variants of papillary thyroid carcinoma and encapsulated follicular thyroid tumours

Background:

Recent studies showed a significant upregulation of distinct microRNAs (miRNAs) in papillary thyroid carcinoma (PTC). The objective of this study was to explore whether this upregulation could also be assigned to distinct histomorphological variants of PTC, especially the follicular variant and other encapsulated follicular thyroid tumours.

Methods:

We used total RNA of 113 formalin-fixed paraffin-embedded tissues of 50 PTCs ((10 conventional type (PTC-CT), 10 tall cell variants (PTC-TCVs), 30 follicular variants (PTC-FVs)), 10 follicular adenomas (FAs), 10 multinodular goitres (MNGs), 21 follicular thyroid carcinomas and 22 well-differentiated tumours of unknown malignant potential (WDT-UMP) to analyse the miRNA expression pattern of five selected miRNAs (146b, 181b, 21, 221 and 222) using RT–PCR TaqMan miRNA assay to explore the diagnostic utility of this method.

Results:

The mean values of the expression pattern of all miRNAS in PTCs show a statistically significant difference from those in MNG and FA with fold changes up to 90 for miRNA 146b, P<0.001. No differences in expression pattern could be showed between MNG and FA. The PTC-FVs differ significantly from FA in all five miRNAS, from MNG in three and from WDT-UMP in one miRNA with fold changes between 1.7 and 21.2, but failed to be of diagnostic value regarding individual cases with substantial overlaps.

Conclusion:

We conclude that analysis of a set of five selected miRNAS distinguish common variants of PTC from FA/MNG but failed to be a useful diagnostic method in individual and doubtful cases, especially in the differential diagnosis of encapsulated follicular thyroid tumours.

Clinicopathologic and molecular disease prognostication for papillary thyroid cancer

Despite its increasing incidence over the last 30 years, the mortality rate of papillary thyroid cancer (PTC) has decreased significantly. Nevertheless, a minority of patients still present with an aggressive form of PTC that can lead to death, even after a prolonged period of survival. Many classifications exist that allow one to stratify the clinical risk of recurrence and death in patients with PTC; however, the parameters upon which they are established are pathological and molecular and, therefore, are revealed only after surgery. The preoperative identification of these aggressive variants of PTC would allow one to schedule a more aggressive operation (e.g., total thyroidectomy together with central and/or mono- or bi-lateral node dissections) in patients with high-risk PTC. This article reviews the parameters used most commonly to differentiate low-risk PTCs from their more aggressive variants and describes some of the newest molecular therapies for this latter group of tumors.

Encapsulated thyroid tumors of follicular cell origin with high grade features (high mitotic rate/tumor necrosis): a clinicopathologic and molecular study

Encapsulated thyroid tumors of follicular cell origin with high-grade features (EFHG) are unusual neoplasms. In current classification schemes, they are called atypical adenomas or follicular, papillary, or poorly differentiated carcinoma. When noninvasive, EFHG create a major therapeutic/diagnostic dilemma stemming from their rarity, low-stage, high-grade appearance, and lack of long-term follow-up studies. All cases of EFHG were defined as encapsulated tumors of follicular cell origin with at least 5 mitoses per 10 high-power fields and/or tumor necrosis. Available tissues were subjected to a thyroid carcinoma platform for mass spectrometry high-throughput genotyping, which consisted of 111 known mutations in 16 different genes: BRAF, RET, NRAS, HRAS, KRAS, PIK3CA, AKT1, and other related genes. Twenty-five cases met the selection criteria. Tumor necrosis was present in 56.0% (n = 14). Extensive vascular invasion was identified in 24.0% (n = 6). Eight (32%) of 25 tumors were noninvasive. Twenty-two patients (88%) were free of disease (median follow up: 8.5 years). All 8 noninvasive tumor did not recur despite focal/extensive tumor necrosis in 3 cases and a median follow-up of 11.9 years. EFHG with no vascular invasion did not recur. In patients without distant metastases at presentation (n = 24), 33% (2/6) of patients with extensive angioinvasion relapsed, whereas none of 18 with absent/focal vascular invasion recurred (P = .054). Mutations were found in 10 (45%) of 22 cases tested: 8 had NRAS codon 61, 1 KRAS codon 61, and 1 had coexistent BRAF V600E and AKT1. There was a higher frequency of RAS (9/22, 41%) than BRAF mutations (1/22, 4.5%) (P = .009). Noninvasive EFHG have an indolent behavior even in the presence of extensive tumor necrosis. EFHG with absent vascular invasion have an excellent prognosis despite the frequent occurrence of tumor necrosis. NRAS mutations are the most frequent oncogenic event in EFHG.

Increasing the number of thyroid lesions classes in microarray analysis improves the relevance of diagnostic markers

Background

Genetic markers for thyroid cancers identified by microarray analysis have offered limited predictive accuracy so far because of the few classes of thyroid lesions usually taken into account. To improve diagnostic relevance, we have simultaneously analyzed microarray data from six public datasets covering a total of 347 thyroid tissue samples representing 12 histological classes of follicular lesions and normal thyroid tissue. Our own dataset, containing about half the thyroid tissue samples, included all categories of thyroid lesions.

Methodology/Principal Findings

Classifier predictions were strongly affected by similarities between classes and by the number of classes in the training sets. In each dataset, sample prediction was improved by separating the samples into three groups according to class similarities. The cross-validation of differential genes revealed four clusters with functional enrichments. The analysis of six of these genes (APOD, APOE, CLGN, CRABP1, SDHA and TIMP1) in 49 new samples showed consistent gene and protein profiles with the class similarities observed. Focusing on four subclasses of follicular tumor, we explored the diagnostic potential of 12 selected markers (CASP10, CDH16, CLGN, CRABP1, HMGB2, ALPL2, ADAMTS2, CABIN1, ALDH1A3, USP13, NR2F2, KRTHB5) by real-time quantitative RT-PCR on 32 other new samples. The gene expression profiles of follicular tumors were examined with reference to the mutational status of the Pax8-PPARγ, TSHR, GNAS and NRAS genes.

Conclusion/Significance

We show that diagnostic tools defined on the basis of microarray data are more relevant when a large number of samples and tissue classes are used. Taking into account the relationships between the thyroid tumor pathologies, together with the main biological functions and pathways involved, improved the diagnostic accuracy of the samples. Our approach was particularly relevant for the classification of microfollicular adenomas.

Clinical implications of molecular markers in follicular cell-derived thyroid cancer

The increasing use/applications of molecular biology techniques have provided new insights on the genetic changes that underlie carcinogenesis and tumor progression in thyroid cancer. Molecular analysis may improve the histopathologic evaluation of follicular cell-derived thyroid carcinoma, not only elucidating some unresolved problems related to the diagnosis and disease prognosis, but also by improving patient management. Besides increasing our comprehension of cancer biology, either genetic alterations or gene expression profiles implicated in thyroid carcinogenesis shed new light on innovative diagnostic procedures as well as on targeted therapies.

BRAFV600E mutation in papillary thyroid carcinoma: a potential target for therapy?

This article reviews the therapeutic significance of the close genotype-phenotype association in papillary thyroid carcinoma, namely regarding the association between genetic alterations in RET, BRAF or RAS genes and the histopathological variants of papillary thyroid carcinoma. Based upon the aforementioned review on morphology and molecular pathology, the most recent prognostic and therapeutic data are reviewed and the role of targeted therapies, namely those interfering with BRAF-activated pathways are discussed, which may play a role in the treatment of patients with papillary thyroid carcinoma unresponsive to radioactive iodine.

Role of NKX2-1 in N-bis(2-hydroxypropyl)-nitrosamine-induced thyroid adenoma in mice

NKX2-1 is a homeodomain transcription factor that is critical for genesis of the thyroid and transcription of the thyroid-specific genes. Nkx2-1-thyroid-conditional hypomorphic mice were previously developed in which Nkx2-1 gene expression is lost in 50% of the thyroid cells. Using this mouse line as compared with wild-type and Nkx2-1 heterozygous mice, a thyroid carcinogenesis study was carried out using the genotoxic carcinogen N-bis(2-hydroxypropyl)-nitrosamine (DHPN), followed by sulfadimethoxine (SDM) or the non-genotoxic carcinogen amitrole (3-amino-1,2,4-triazole). A significantly higher incidence of adenomas was obtained in Nkx2-1-thyroid-conditional hypomorphic mice as compared with the other two groups of mice only when they were treated with DHPN + SDM, but not amitrole. A bromodeoxyuridine incorporation study revealed that thyroids of the Nkx2-1-thyroid-conditional hypomorphic mice had >2-fold higher constitutive cell proliferation rate than the other two groups of mice, suggesting that this may be at least partially responsible for the increased incidence of adenoma in this mouse line after genotoxic carcinogen exposure. Thus, NKX2-1 may function to control the proliferation of thyroid follicular cells following damage by a genotoxic carcinogen.

Multiple genetic alterations in papillary thyroid cancer are associated with younger age at presentation

BACKGROUND

There is a significant gender and age disparity in thyroid cancer incidence and outcome. The molecular basis for these divergent clinical presentations and outcome are essentially unknown.

METHODS

The primary tumor genotype in 217 patients with papillary thyroid cancer was determined for six common somatic genetic alterations (RET/PTC1, RET/PTC3, and NTRK1 rearrangements, and BRAF V600E, KRAS, and NRAS hotspot mutations) by PCR and direct sequencing, and nested PCR. Univariate and multivariate analyses were performed to determine the association of genetic changes and age, gender, and other clinicopathologic factors.

RESULTS

One hundred twenty-one of the 190 conventional papillary thyroid carcinoma samples (63.7%) had at least one genetic alteration, and 27 of the samples (14.2%) had more than one alteration. In the follicular variant of papillary thyroid carcinomas, 13 of the 27 samples (48.1%) had at least one genetic alteration and three of the 27 samples (11.1%) had more than one. The presence of multiple genetic alterations was associated with younger age at diagnosis (P=0.034), mean difference of 8 y earlier. We found no significant association with the number or type of genetic alterations present by gender, tumor size, extent of tumor differentiation, multicentricity, lymph node metastasis, distant metastases, TNM stage, and the AMES risk group. The association of multiple genetic alterations and younger age were independent of tumor size, lymph node or distant metastasis, TNM stage, or AMES risk group.

CONCLUSIONS

Multiple genetic alterations are more common in younger patients with papillary thyroid cancer, but there is no difference in the type or number of genetic alterations by gender. Our findings suggest that multiple genetic alterations in thyroid cancer may be associated with earlier disease initiation and or progression.

Transcriptional Profile of Ki-Ras-Induced Transformation of Thyroid Cells

In the last years, an increasing number of experiments has provided compelling evidence for a casual role of Ras protein mutations, resulting in their constitutive activation, in thyroid carcinogenesis. However, despite the clear involvement of Ras proteins in thyroid carcinogenesis, the nature of most of the target genes, whose expression is modulated by the Ras-induced signaling pathways and that are ultimately responsible for Ras-induced cellular transformation, remains largely unknown. To analyze Ras-dependent modulation of gene expression in thyroid cells we took advantage of a differentiated rat thyroid cell line, FRTL-5. As a model for Ras-dependent thyroid transformation, we used FRTL-5 cells infected with the Kirsten murine sarcoma virus, carrying the v-Ki-Ras oncogene. The infected cells (FRTL-5 v-Ki-Ras) have lost expression of the thyroid differentiation markers and also are completely transformed. We hybridized two different Affimetrix chips containing probe sets interrogating both known rat genes and ESTs for a total of more than 17,000 sequences using mRNA extracted from FRTL-5 and FRTL-5 v-Ki-Ras cell lines. We identified about 50 genes whose expression was induced and about 40 genes whose expression was downregulated more than 10-fold by Ras. We confirmed the differential expression of many of these genes in FRTL-5 v-Ki-Ras as compared to parental cells by using alternative techniques. Remarkably, we investigated the expression of some of the Ras-regulated genes in human thyroid carcinoma cell lines and tumor samples, our results, therefore, providing a new molecular profile of the genes involved in thyroid neoplastic transformation.

Recent advances in molecular biology of thyroid cancer and their clinical implications

Thyroid cancer is the most common endocrine malignancy. With a rapidly rising incidence in recent years, novel efficient management strategies are increasingly needed for this cancer. Remarkable advances have occurred in understanding several major biologic areas of thyroid cancer, including the molecular alterations for the loss of radioiodine avidity of thyroid cancer, the pathogenic role of the MAP kinase and PI3K/Akt pathways and their related genetic alterations, and the aberrant methylation of functionally important genes in thyroid tumorigenesis and pathogenesis. These exciting advances provide unprecedented opportunities for the development of molecular-based novel diagnostic, prognostic, and therapeutic strategies for thyroid cancer.

How molecular pathology is changing and will change the therapeutics of patients with follicular cell-derived thyroid cancer: Table 1

Well-differentiated thyroid carcinomas comprise two well-defined histological types: papillary and follicular (PTCs and FTCs, respectively). Despite being derived from the same cell (thyroid follicular cell), these two types of tumour accumulate distinct genetic abnormalities during progression. The molecular pathology of thyroid cancer is now better understood because of our ability to identify RET/PTC rearrangements and BRAF mutations in the aetiopathogenesis of the large majority of PTCs and the high prevalence of RAS mutations and PAX8/PPARγ rearrangements in follicular patterned carcinomas (FTCs and follicular variant of PTCs). This review summarises most of the molecular alterations currently used as targets for new biological treatments and looks at some of the changes that are already occurring or may occur in the treatment of patients with thyroid cancer. For simplicity, the review is divided up according to the major genetic alterations identified in well-differentiated thyroid carcinomas (RET/PTC rearrangements, BRAF mutations, RAS mutations and mitochondrial DNA deletions and mutations) and their respective treatments.