RET/PTC rearrangement in benign and malignant thyroid diseases: a clinical standpoint

Risk factors for central lymph node metastasis in patients with papillary thyroid carcinoma: a retrospective study

Introduction

Thyroid cancer is the most prevalent endocrine malignancy, with its global incidence increasing annually in recent years. Papillary carcinoma is the most common subtype, frequently accompanied by cervical lymph node metastasis early on. Central lymph node metastasis (CLNM) is particularly the common metastasis form in this subtype, and the presence of lymph node metastasis correlates strongly with tumor recurrence. However, effective preoperative assessment methods for CLNM in patients with papillary thyroid carcinoma (PTC) remain lacking.

Methods

Data from 400 patients diagnosed with PTC between January 1, 2018, and January 1, 2022, at the Shandong Provincial Hospital were retrospectively analyzed. This data included clinicopathological information of the patients, such as thyroid function, BRAF V600E mutation, whether complicated with Hashimoto's thyroiditis, and the presence of capsular invasion. Univariate and multivariate logistic regression analyses were performed to assess the risk factors associated with cervical CLNM in patients with PTC. Subsequently, a clinical prediction model was constructed, and prognostic risk factors were identified based on univariate and multivariate Cox regression analyses.

Results

Univariate and multivariate analyses identified that age >45 years (P=0.014), body mass index ≥25 (P=0.008), tumor size ≥1 cm (P=0.001), capsular invasion (P=0.001), and the presence of BRAF V600E mutation (P<0.001) were significantly associated with an increased risk of CLNM. Integrating these factors into the nomogram revealed an area-under-the-curve of 0.791 (95% confidence interval 0.735-0.846) and 0.765 (95% confidence interval: 0.677-0.852) for the training and validation sets, respectively, indicating strong discriminative abilities. Subgroup analysis further confirmed that patients with papillary thyroid microcarcinoma and BRAF V600E mutations who underwent therapeutic central compartment neck dissection had significantly better 3-year disease-free survival than those who had prophylactic central compartment neck dissection (P<0.001).

Conclusion

The study revealed that age >45 years, body mass index ≥25, tumor size ≥1 cm, BRAF V600E mutation, and capsular invasion are the related risk factors for CLNM in patients with PTC. For patients with clinically nodal-negative (cN0) papillary thyroid microcarcinoma, accurately identifying the BRAF V600E mutation is essential for guiding the central lymph node dissection approach and subsequent treatments.

A study to evaluate association of nuclear grooving in benign thyroid lesions with RET/PTC1 and RET/PTC3 gene translocation

INTRODUCTION

Papillary thyroid carcinoma (PTC) is the most common malignant lesion of the thyroid characterized by unique histological features like nuclear grooving, nuclear clearing, and intra-nuclear inclusions. However, nuclear grooves are observed even in benign thyroid lesions (BTL) like nodular goiter (NG), Hashimoto's thyroiditis (HT), and follicular adenoma (FA) resulting in diagnostic dilemma of the presence of PTC in such BTL. RET/PTC gene translocation is one of the most common oncogenic rearrangements seen in PTC, known to be associated with nuclear grooving. Among different types of RET/PTC translocations, RET/PTC1 and RET/PTC3 gene translocations are the most common types. These translocations have also been identified in many BTL like hyperplastic nodules and HT. Our study aimed to determine the frequency of nuclear grooving in BTL and evaluate their association with RET/PTC1 and RET/PTC3 gene translocation.

METHODS

Formalin-fixed, paraffin-embedded (FFPE) tissue blocks of NG, HT, and FA were included in the study. The hematoxylin and eosin (H&E) stained sections were evaluated for the presence of nuclear grooving/high power field (hpf) and a scoring of 0 to 3 was used for the number of grooves. Sections of 10 μ thickness were cut and the cells containing the nuclear grooves were picked using Laser-Capture microdissection. About 20 to 50 such cells were microdissected in each of the cases followed by RNA extraction, cDNA conversion, realtime-polymerase chain reaction (RQ-PCR) for RET/PTC1 and RET/PTC3 gene translocation, and the findings were analyzed for statistical significance.

RESULTS

Out of 87 BTL included in the study, 67 (77.0%) were NG, 12 (13.7%) were HT, and 8 (9.2%) were FA. Thirty-two cases (36.8%) had nuclear grooving with 18 out of 67 NG, 6 out of 12 HT, and all 8 cases of FA showing a varying number of nuclear grooves. A significant association between the number of nuclear grooves with RET/PTC gene translocation (p-value of 0.001) was obtained. A significant association of HT with RET/PTC gene translocation (p-value of 0.038) was observed. RET/PTC1 and RET/PTC3 translocation were seen in 5 out of 87 cases, with HT showing positivity in 2 and FA in 1 case for RET/PTC1 and HT in 1 and FA in 2 cases for RET/PTC3 gene translocation with 1 case of FA being positive for both RET/PTC1 and RET/PTC3 gene translocation.

CONCLUSIONS

The frequency of nuclear grooving among BTLs in our study was 36.8%. Our study shows, that when BTLs, show nuclear grooves, with an increase in the nuclear size, oval and elongated shape, favors the possibility of an underlying genetic aberration like RET/PTC gene translocation, which in turn supports the reporting pathologist to suggest a close follow up of the patients on seeing such nuclear features on cytology or histopathology sample, particularly in HT.

The Difference in Clinical Behavior of Gene Fusions Involving RET/PTC Fusions and THADA/IGF2BP3 Fusions in Thyroid Nodules

BACKGROUND

Molecular testing has been used as an adjunct to morphological evaluation in the workup of thyroid nodules. This study investigated the impact of two gene fusions, RET/PTC and THADA/IGF2BP3, that have been described as oncogenic events in thyroid neoplasms.

METHODS

We performed a retrospective, single-centered study at a McGill University teaching hospital in Montreal, Canada, from January 2016 to August 2021. We included patients who underwent surgery for thyroid nodules that pre-operatively underwent molecular testing showing either RET/PTC or THADA/IGF2BP3 gene fusion.

RESULTS

This study included 697 consecutive operated thyroid nodules assessed using molecular testing, of which five had the RET/PTC fusion and seven had the THADA/IGF2BP3 fusion. Of the five nodules in the RET/PTC group, 100% were malignant and presented as Bethesda V/VI. Eighty percent (4/5) were found to have lymph node metastasis. Twenty percent (1/5) had extrathyroidal extensions. Sixty percent (3/5) were a diffuse sclerosing variant of papillary thyroid carcinoma, and the rest were the classical variant. Of the seven THADA/IGF2BP3 nodules, all presented as Bethesda III/IV and 71.4% (5/7) were malignant based on the final pathology analysis, and 28.6% (2/7) were NIFTP. All the THADA/IGF2BP3 fusion malignancies were a follicular variant of papillary thyroid carcinoma. None had lymph node metastasis or displayed extrathyroidal extensions.

CONCLUSIONS

RET/PTC nodules presented as Bethesda V/VI and potentially had more aggressive features, whereas THADA/IGF2BP3 nodules presented as Bethesda III/IV and had more indolent behavior. This understanding may allow clinicians to develop more targeted treatment plans, such as the extent of surgery and adjuvant radioactive iodine treatment.

Novel thrombospondin-1 transcript exhibits distinctive expression and activity in thyroid tumorigenesis

Thrombospondin 1 (TSP1) is known for its cell-specific functions in cancer progression, such as proliferation and migration. It contains 22 exons that may potentially produce several different transcripts. Here, we identified TSP1V as a novel TSP1-splicing variant produced by intron retention (IR) in human thyroid cancer cells and tissues. We observed that TSP1V functionally inhibited tumorigenesis contrary to TSP1 wild-type, as identified in vivo and in vitro. These activities of TSP1V are caused by inhibiting phospho-Smad and phospho-focal adhesion kinase. Reverse transcription polymerase chain reaction and minigene experiments revealed that some phytochemicals/non-steroidal anti-inflammatory drugs enhanced IR. We further found that RNA-binding motif protein 5 (RBM5) suppressed IR induced by sulindac sulfide treatment. Additionally, sulindac sulfide reduced phospho-RBM5 levels in a time-dependent manner. Furthermore, trans-chalcone demethylated TSP1V, thereby preventing methyl-CpG-binding protein 2 binding to TSP1V gene. In addition, TSP1V levels were significantly lower in patients with differentiated thyroid carcinoma than in those with benign thyroid nodule, indicating its potential application as a diagnostic biomarker in tumor progression.

Immunocytochemistry Profile of Benign Thyroid Nodules Not Responding to Thermal Ablation: A Retrospective Study

Purpose

Thermal ablations (TA) are gaining ground as alternative options to conventional therapies for symptomatic benign thyroid nodules. Little is known about the impact of nodule biology on the outcomes of TA. The aim of our study was to evaluate the baseline immunocytochemistry profile of thyroid nodules that were poorly responsive to TA in order to identify potential predictors of the treatment response.

Methods

From a cohort of 406 patients with benign thyroid nodules treated with TA and followed for 5 years, we retrospectively selected two groups of patients: NONRESPONDERS (patients who did not respond to TA and were later surgically treated) and RESPONDERS (patients who responded to TA). The fine-needle aspiration cytology (FNAC) slides obtained before TA were stained for Galectin-3, HBME-1, CK-19, and Ki-67.

Results

Benign nodules of NONRESPONDERS (n = 19) did not express CK-19 (p = 0.03), as compared to RESPONDERS (n = 26). We combined the absence of CK-19 and the presence of Ki-67 to obtain a composite biomarker of resistance to TA, which discriminated between likelihood of retreatment and no retreatment with an AUC of 0.68 (95%CI: 0.55-0.81) and a sensitivity, specificity, PPV, and NPV of 29%, 91%, 71%, and 64%, respectively.

Conclusion

In benign thyroid nodules, the absence of CK-19 was associated with resistance to TA, while the presence of CK-19 was predictive of response to TA. If confirmed, this finding could provide rapid and inexpensive information about the potential outcome of TA on benign thyroid nodules. In addition, as CK-19 can be expressed in adenomatous hyperplasia, it could be speculated that these nodules, rather than follicular adenomas, might be better candidates for TA.

Molecular features of aggressive thyroid cancer

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) have a worse prognosis with respect to well differentiated TC, and the loss of the capability of up-taking ¹³¹I is one of the main features characterizing aggressive TC. The knowledge of the genomic landscape of TC can help clinicians to discover the responsible alterations underlying more advance diseases and to address more tailored therapy. In fact, to date, the antiangiogenic multi-targeted kinase inhibitor (aaMKIs) sorafenib, lenvatinib, and cabozantinib, have been approved for the therapy of aggressive radioiodine (RAI)-resistant papillary TC (PTC) or follicular TC (FTC). Several other compounds, including immunotherapies, have been introduced and, in part, approved for the treatment of TC harboring specific mutations. For example, selpercatinib and pralsetinib inhibit mutant RET in medullary thyroid cancer but they can also block the RET fusion proteins-mediated signaling found in PTC. Entrectinib and larotrectinib, can be used in patients with progressive RAI-resistant TC harboring TRK fusion proteins. In addition FDA authorized the association of dabrafenib (BRAF^V600E inhibitor) and trametinib (MEK inhibitor) for the treatment of BRAF^V600E-mutated ATC. These drugs not only can limit the cancer spread, but in some circumstance they are able to induce the re-differentiation of aggressive tumors, which can be again submitted to new attempts of RAI therapy. In this review we explore the current knowledge on the genetic landscape of TC and its implication on the development of new precise therapeutic strategies.

Advances in pharmacotherapy for advanced thyroid cancer of follicular origin (PTC, FTC). New approved drugs and future therapies

INTRODUCTION

The most common altered signaling found in aggressive iodine-refractory Thyroid cancer derived from follicular cells (RAI-TC) are RTK, MAPK, PI3K, WNT, BRAF, RAS, RET, and TP53. Tyrosine Kinase Inhibitors (TKI) are multi-kinase inhibitors able to act against different pathways, that elicit an anti-neoplastic activity.

AREAS COVERED

The aim of this paper is to review recent novel molecular therapies of RAI-TC. Recently, sorafenib and lenvatinib, have been approved for the treatment of aggressive RAI-TC. Other studies are evaluating vandetanib and selumetinib in RAI-TC. Furthermore, preliminary studies have evaluated dabrafenib, and vemurafenib in BRAF mutated RAI-TC patients to re-induce 131-iodine uptake. The interplay between cells of the immune system and cancer cells can be altered by immune checkpoints inhibitors. The expression of PDL1 in RAI-TC was related to tumor recurrence and poor survival. Several clinical trials are investigating a combination of different therapies, such as lenvatinib and pembrolizumab.

EXPERT OPINION

Mechanisms of resistance to TKIs inhibitors can be of intrinsic or acquired origin. An acquired resistance to lenvatinib, or sorafenib can be due to upregulation of FGFR; therefore anti-FGFR agents are evaluated. A new strategy is to combine TKIs with immunotherapy. Several studies are evaluating lenvatinib and pembrolizumab in RAI-TC patients.

A comparison of DP-TOF Mass Spectroscopy (MS) and Next Generation Sequencing (NGS) methods for detecting molecular mutations in thyroid nodules fine needle aspiration biopsies

Mutations in the B-Raf proto-oncogene, serine/threonine kinase (BRAF), have been linked to a variety of solid tumors such as papillary thyroid carcinoma. The purpose of this study was to compare the DP-TOF, a DNA mass spectroscopy (MS) platform, and next-generation sequencing (NGS) methods for detecting multiple-gene mutations (including BRAF^V600E) in thyroid nodule fine-needle aspiration fluid. In this study, we collected samples from 93 patients who had previously undergone NGS detection and had sufficient DNA samples remaining. The MS method was used to detect multiple-gene mutations (including BRAF^V600E) in DNA remaining samples. NGS detection method was used as the standard. The MS method's overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 95.8%, 100%, 100%, and 88%, respectively in BRAF^V600E gene mutation detection. With a kappa-value of 0.92 (95%CI 0.82-0.99), the level of agreement between these methods was incredibly high. Furthermore, when compared to NGS in multiple-gene detection, the MS method demonstrated higher sensitivity and specificity, 82.9% and 100%, respectively. In addition, we collected the postoperative pathological findings of 50 patients. When the postoperative pathological findings were used as the standard, the MS method demonstrated higher sensitivity and specificity, at 80% and 80%, respectively. Our findings show that the MS method can be used as an inexpensive, accurate, and dependable initial screening method to detect genes mutations and as an adjunct to clinical diagnosis.

The Combination of Sonographic Features and the Seven-Gene Panel May be Useful in the Management of Thyroid Nodules With Indeterminate Cytology

Introduction

The management of patients with indeterminate thyroid nodules, which account for 10-25% of thyroid fine needle aspiration biopsies (FNABs), is still very challenging.

Aim

To verify the utility of the seven-gene panel in combination with ultrasound features in the clinical management of indeterminate thyroid nodules.

Results

The study group included 188 indeterminate thyroid nodules, divided into TIR3A (56.4%) and TIR3B (43.6%). A significant correlation between US categories and both cytological and molecular results was observed. In detail, TIR3B cytology was more frequent in EU-TIRADS 4 and 5 nodules (54.7 and 50%, respectively) than in EU-TIRADS 2 and 3 nodules (31%, p = 0.04). Similarly, the rate of a nodule with a mutation increased with the increase of US risk class (6.0% in EU-TIRADS 2 and 3, 9.3% in EUTIRADS-4 and 27.8% in EUTIRAD-5, p = 0.01). Among thyroid nodules submitted to surgery, final histology was benign in 61.4% nodules, while malignancy was diagnosed in 38.6% nodules. Using US score as tool for decision-making in TIR3A subgroup, we correctly classified 64.5% of thyroid nodules. The second tool (seven-gene panel test) was used in the subgroup of US high-risk nodules. By multiple tests with a series approach (US in all cases and US plus seven-gene panel in US high risk nodules) 84% of cases were correctly classified. In TIR3B nodules, using only seven-gene panel as tool for decision making, we correctly classified 61.9% of indeterminate nodules. By multiple tests with series approach (seven-gene panel in all cases and seven-gene panel plus US score in non-mutated nodules) only a slight improvement of thyroid nodule classification (66.6%) was observed.

Conclusions

US score seems able to correctly discriminate between TIR3A nodules in which a conservative approach may be used, and those in which additional test, such as molecular test, may be indicated. On the contrary, in TIR3B nodules both US risk stratification and seven-gene panel seem to be of little use, because the risk of thyroid cancer remains high regardless of US score and mutational status.

Molecular targets of tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer (TC) is the eighth most frequently diagnosed cancer worldwide with a rising incidence in the past 20 years. Surgery is the primary strategy of therapy for patients with medullary TC (MTC) and differentiated TC (DTC). In DTC patients, radioactive iodine (RAI) is administered after thyroidectomy. Neck ultrasound, basal and thyroid-stimulating hormone-stimulated thyroglobulin are generally performed every three to six months for the first year, with subsequent intervals depending on initial risk assessment, for the detection of possible persistent/recurrent disease during the follow up. Distant metastases are present at the diagnosis in ∼5 % of DTC patients; up to 15 % of patients have recurrences during the follow up, with a survival reduction (70 %-50 %) at 10-year. During tumor progression, the iodide uptake capability of DTC cancer cells can be lost, making them refractory to RAI, with a negative impact on the prognosis. Significant advances have been done recently in our understanding of the molecular pathways implicated in the progression of TCs. Several drugs have been developed, which inhibit signaling kinases or oncogenic kinases (BRAF^V600E, RET/PTC), such as those associated with Platelet-Derived Growth Factor Receptor and Vascular Endothelial Growth Factor Receptor. Tyrosine kinase receptors are involved in cancer cell proliferation, angiogenesis, and lymphangiogenesis. Several tyrosine kinase inhibitors (TKIs) are emerging as new treatments for DTC, MTC and anaplastic TC (ATC), and can induce a clinical response and stabilize the disease. Lenvatinib and sorafenib reached the approval for RAI-refractory DTC, whereas cabozantinib and vandetanib for MTC. These TKIs extend median progression-free survival, but do not increase the overall survival. Severe side effects and drug resistance can develop in TC patients treated with TKIs. Additional studies are needed to identify a potential effective targeted therapy for aggressive TCs, according to their molecular characterization.

Clinical and Translational Challenges in Thyroid Cancer

Thyroid cancer is the most common endocrine malignancy and it accounts for 1% of all newly diagnosed tumors. Approximately 10% of patients with differentiated thyroid carcinomas (DTC) and 30% with medullary thyroid carcinoma (MTC) could not be cured with locoregional treatment and could develop metastatic disease. In addition, one of the most aggressive solid tumors can arise from the thyroid gland, the anaplastic thyroid carcinoma, with a median overall survival of less than 6 months. Currently, only four drugs are approved for the treatment of DTC and MTC and several unmet needs are focusing the scientific discussions, including the resistant setting, the off-target side effects that may reduce the efficacy and the molecular knowledge-based combinations. In this review, we aimed to discuss the current molecular landscape and treatment of thyroid cancers, and the ongoing clinical and translational research lines focusing on new drugs and drug combinations to improve the inhibition of driver mutations, such as BRAF and RET, and how systemic therapies that improved outcomes of other cancer types, like immunotherapy and peptide receptor radionuclide therapy, may play a role in the future management of advanced thyroid cancers.

Primary cell cultures for the personalized therapy in aggressive thyroid cancer of follicular origin

Thyroid cancer (TC) is the most prevalent endocrine malignancy. More than 90 % of TC is represented by differentiated TC (DTC) arising from the follicular thyroid cells. DTC includes papillary TC (PTC), follicular TC (FTC), and Hürthle cell TC. Anaplastic TC (ATC) accounts for 1% of TC, and it represents 15-40 % of TC death. Current treatment strategies are not completely effective against aggressive DTC or ATC, and mortality is one of the most important challenges. Recently, progresses have been obtained in the understanding of the molecular/genetic basis of TC progression, and new drugs have been introduced [i.e. tyrosine kinase inhibitors (TKIs)], able to block the oncogenic or signaling kinases, associated with cellular growth. Thyroid cell lines, obtained from tumoral cells and chosen for high proliferation in vitro, have been used as preclinical models. Actually, these cells lose the characteristic features of the primary tumor, because they adapt to in vitro growth conditions. For these reasons, the use of these cell lines has important limitations, and more recently human primary cell cultures have been established as monolayer cultures, and investigated for their biological behavior. Moreover, in the past, primary TC cells could be collected only through surgical biopsies, while recently human primary cell cultures can be established also from samples of fine-needle aspiration citology from aggressive dedifferentiated DTC or ATC. Testing in vitro different TKIs in each patient can help to develop new personalized treatments, without using ineffective drugs. In conclusion, personalized medicine and precise oncology, which consider both patients and their disease features, represent the future of the treatment approach, and further progress is needed in this direction.

Occurrence of paratesticular ganglioneuroma 18 years after concurrent adrenal ganglioneuroma and papillary thyroid carcinoma - a case report

BACKGROUND

Ganglioneuromas (GNs) are composed of mature ganglion cells and Schwann cells with a fibrous stroma; GNs are most often observed in children and young adults. The majority of non-cranial GNs are located in the retroperitoneum and posterior mediastinum. Other reported rare sites include the adrenal gland, small intestine, colon and urinary bladder. However, para-testicular GNs are even more rare.

CASE PRESENTATION

Herein, we report the case of a patient with concurrent adrenal GN and thyroid papillary carcinoma who developed paratesticular GN eighteen years later.

CONCLUSIONS

We conclude that there is an association among papillary thyroid carcinoma, GN and MEN2 syndromes. This case report may provide important information for the proposed association. However, further studies are required.

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

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

Novel rearrangements involving the RET gene in papillary thyroid carcinoma

BACKGROUND

In the field of gene fusions driving tumorigenesis in papillary thyroid carcinoma (PTC), rearrangement of the proto-oncogene RET is the most frequent alteration. Apart from the most common rearrangement of RET to CCDC6, more than 15 partner genes are yet reported. The landscape of RET rearrangements in PTC ("RET-PTC") can notably be enlarged by modern targeted next-generation sequencing, indicating similarities between oncogenic pathways in other cancer types with identical genetic alterations.

METHODS

Targeted next-generation sequencing was performed for two cases of BRAF-wild type PTC with confirmation of the results by Sanger sequencing. A "UniProt" database research was performed to assess protein alterations resulting from RET rearrangements.

RESULTS

RUFY2-RET and KIAA1468-RET were detected. The fusion genes were not present in normal tissue of the index patients. The rearrangement RUFY2-RET lead to a fusion of the RET tyrosine kinase domain to a RUN domain and a coiled-coil domain. For KIAA1468-RET, a fusion to a LisH domain and two coiled-coil domains resulted.

CONCLUSIONS

RUFY2-RET and KIAA1468-RET are novel RET/PTC rearrangements. The fusions were previously described in non-small cell lung cancer. The rearrangement results in a fusion of the RET tyrosine kinase to regulatory domains of RUFY2 and KIAA1468.

Molecular testing in the diagnosis of differentiated thyroid carcinomas

Different genetic mutations and other molecular alterations in papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) can be detected in fine-needle aspiration (FNA) of thyroid nodules, and can be used successfully to ameliorate cancer diagnosis and management of patients with thyroid nodules. The greatest experience has been obtained with the diagnostic use of BRAF mutation that is strongly specific for malignancy when detected using well-validated techniques. The strongest diagnostic result can be obtained testing FNA samples for a panel of mutations that typically involve TERT, BRAF, PAX8/PPARγ, RAS, and RET/PTC. Finding any of these mutations in a thyroid nodule provides strong indication for malignancy and helps to refine clinical management for a significant proportion of patients with indeterminate cytology. The use of molecular markers, as TERT, BRAF, PAX8/PPARγ, RAS, and RET/PTC, may be considered for patients with indeterminate FNA cytology (FNAC) to help guide management. In patients with indeterminate TIR3 FNA, the combination of precise molecular marker expression analysis with molecular mutations evaluations could ameliorate significantly the accuracy of cancer diagnosis. However other prospective studies are needed to identify more accurate molecular markers. Finally, the knowledge of these molecular pathways has permitted the development of new targeted therapies for aggressive TC.

Epigenetic modifications in poorly differentiated and anaplastic thyroid cancer

Well-differentiated thyroid cancer accounts for the majority of endocrine malignancies and, in general, has an excellent prognosis. In contrast, the less common poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) are two of the most aggressive human malignancies. Recently, there has been an increased focus on the epigenetic alterations underlying thyroid carcinogenesis, including those that drive PDTC and ATC. Dysregulated epigenetic candidates identified include the Aurora group, KMT2D, PTEN, RASSF1A, multiple non-coding RNAs (ncRNA), and the SWI/SNF chromatin-remodeling complex. A deeper understanding of the signaling pathways affected by epigenetic dysregulation may improve prognostic testing and support the advancement of thyroid-specific epigenetic therapies. This review outlines the current understanding of epigenetic alterations observed in PDTC and ATC and explores the potential for exploiting this understanding in developing novel therapeutic strategies.

Detection of RET (rearranged during transfection) variants and their downstream signal molecules in RET rearranged lung adenocarcinoma patients

BACKGROUND

We screened resected tumor tissues from patients with lung cancer for EGFR mutations, ALK rearrangements, and rearranged during transfection (RET) gene variants (including RET rearrangements and the Kinesin Family Member 5B (KIF5B)-RET fusion gene) using various methods including reverse transcription polymerase chain reaction (RT-PCR), transcript assays, fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC). We also examined the protein expression of associated downstream signaling molecules to assess the effect of these variants on patient outcome.

METHOD

We constructed a tissue microarray (TMA) comprising 581 resected tumor tissues from patients with lung adenocarcinoma and analyzed the microarray by both FISH (using RET break-apart and KIF5B-RET SY translocation probes) and a commercial RET transcript assay. We evaluated the expression of RET and RET-related signaling molecules, including p-AKT and p-ERK, by TMA -based IHC staining.

RESULTS

Among the 581 specimens, 51 (8.8%) specimens harbored RET rearrangements, including 12 cases (2.1%) carrying a KIF5B-RET fusion gene. Surprisingly, RET expression was lower in KIF5B-RET fusion gene-positive than in RET wild-type specimens. We detected activating EGFR mutations in 11 (21.6%) of the 51 RET variant-positive specimens. Among the KIF5B-RET fusion gene-positive specimens, p-ERK expression was significantly lower in the EGFR mutation subgroup showing RET expression than in the EGFR mutation subgroup that did not express RET. Similarly, the RET rearrangement group showed significant variation in the expression level of p-AKT (P = 0.028) and p-ERK, whose expression remarkably increased in specimens not expressing RET. The expression of p-ERK markedly increased in the RET rearrangement group regardless of RET expression.

CONCLUSION

This result suggests that a combination of RET and ERK inhibitors may be an effective treatment strategy for lung adenocarcinoma patients harboring RET variants.

Enhanced cytotoxic effect of camptothecin nanosponges in anaplastic thyroid cancer cells in vitro and in vivo on orthotopic xenograft tumors

Anaplastic carcinoma of the thyroid (ATC) is a lethal human malignant cancer with median survival of 6 months. To date, no treatment has substantially changed its course, which makes urgent need for the development of novel drugs or novel formulations for drug delivery. Nanomedicine has enormous potential to improve the accuracy of cancer therapy by enhancing availability and stability, decreasing effective doses and reducing side effects of drugs. Camptothecin (CPT) is an inhibitor of DNA topoisomerase-I with several anticancer properties but has poor solubility and a high degradation rate. Previously, we reported that CPT encapsulated in β-cyclodextrin-nanosponges (CN-CPT) increased solubility, was protected from degradation and inhibited the growth of prostate tumor cells both in vitro and in vivo. The aim of this study was to extend that work by assessing the CN-CPT effectiveness on ATC both in vitro and in vivo. Results showed that CN-CPT significantly inhibited viability, clonogenic capacity and cell-cycle progression of ATC cell lines showing a faster and enhanced effect compared to free CPT. Moreover, CN-CPT inhibited tumor cell adhesion to vascular endothelial cells, migration, secretion of pro-angiogenic factors (IL-8 and VEGF-α), expression of β-PIX, belonging to the Rho family activators, and phosphorylation of the Erk1/2 MAPK. Finally, CN-CPT significantly inhibited the growth, the metastatization and the vascularization of orthotopic ATC xenografts in SCID/beige mice without apparent toxic effects in vivo. This work extends the previous insight showing that β-cyclodextrin-nanosponges are a promising tool for the treatment of ATC.

Anaplastic thyroid carcinoma: from clinicopathology to genetics and advanced therapies

Anaplastic thyroid carcinoma (ATC) is a rare malignancy, accounting for 1-2% of all thyroid cancers. Although rare, ATC accounts for the majority of deaths from thyroid carcinoma. ATC often originates in a pre-existing thyroid cancer lesion, as suggested by the simultaneous presence of areas of differentiated or poorly differentiated thyroid carcinoma. ATC is characterized by the accumulation of several oncogenic alterations, and studies have shown that an increased number of oncogenic alterations equates to an increased level of dedifferentiation and aggressiveness. The clinical management of ATC requires a multidisciplinary approach; according to recent American Thyroid Association guidelines, surgery, radiotherapy and/or chemotherapy should be considered. In addition to conventional therapies, novel molecular targeted therapies are the most promising emerging treatment modalities. These drugs are often multiple receptor tyrosine kinase inhibitors, several of which have been tested in clinical trials with encouraging results so far. Accordingly, clinical trials are ongoing to evaluate the safety, efficacy and effectiveness of these new agents. This Review describes the updated clinical and pathological features of ATC and provides insight into the molecular biology of this disease. The most recent literature regarding conventional, newly available and future therapies for ATC is also discussed.

The role of molecular diagnostic testing in the management of thyroid nodules

INTRODUCTION

Fine needle aspiration (FNA) with cytologic examination remains the standard of care for investigation of thyroid nodules. However, as many as 30% of FNA samples are cytologically indeterminate for malignancy, which confounds clinical management. To reduce the burden of repeat diagnostic testing and unnecessary surgery, there has been extensive investigation into molecular markers that can be detected on FNA specimens to more accurately stratify a patient's risk of malignancy. Areas covered: In this review, the authors discuss recent evidence and progress in molecular markers used in the diagnosis of thyroid cancer highlighting somatic gene alterations, molecular technologies and microRNA analysis. Expert commentary: The goal of molecular markers is to improve diagnostic accuracy and aid clinicians in the preoperative management of thyroid lesions. Modalities such as direct mutation analysis, mRNA gene expression profiling, next-generation sequencing, and miRNA expression profiling have been explored to improve the diagnostic accuracy of thyroid nodule FNA. Although no perfect test has been discovered, molecular diagnostic testing has revolutionized the management of thyroid nodules.

A Concise Atlas of Thyroid Cancer Next-Generation Sequencing Panel ThyroSeq v.2

The next-generation sequencing technology allows high out-put genomic analysis. An innovative assay in thyroid cancer, ThyroSeq® was developed for targeted mutation detection by next generation sequencing technology in fine needle aspiration and tissue samples. ThyroSeq v.2 next generation sequencing panel offers simultaneous sequencing and detection in >1000 hotspots of 14 thyroid cancer-related genes and for 42 types of gene fusions known to occur in thyroid cancer. ThyroSeq is being increasingly used to further narrow the indeterminate category defined by cytology for thyroid nodules. From a surgical perspective, genomic profiling also provides prognostic and predictive information and closely relates to determination of surgical strategy. Both the genomic analysis technology and the informatics for the cancer genome data base are rapidly developing. In this paper, we have gathered existing information on the thyroid cancer-related genes involved in the initiation and progression of thyroid cancer. Our goal is to assemble a glossary for the current ThyroSeq genomic panel that can help elucidate the role genomics play in thyroid cancer oncogenesis.

RAS Mutations, and RET/PTC and PAX8/PPAR-gamma Chromosomal Rearrangements Are Also Prevalent in Benign Thyroid Lesions: Implications Thereof and A Systematic Review

BACKGROUND

Molecular markers associated with thyroid malignancy are increasingly being used as differential diagnostic tools for thyroid nodules. However, little has been reported recently regarding the prevalence of these markers in benign lesions. The literature was systematically reviewed to examine studies that reported on the prevalence of these markers in benign thyroid lesions.

METHODS

Appropriate studies published between January 1, 2000, and April 30, 2015, and cataloged in PubMed, Embase, Cochrane, Scopus, and Web of Science databases were searched for by combining different keywords for "thyroid tumor" with both general and specific keywords for "molecular marker" by using "AND" as the Boolean operator. All studies meeting criteria that reported the prevalence of RAS mutations, and RET/PTC and PAX8/PPAR-gamma chromosomal rearrangements in benign thyroid lesions were included for study.

RESULTS

A total of 64 articles (including 8162 patients, of whom 42.5% had benign lesions) that met all the study criteria were systematically reviewed and abstracted. Among 35 studies examining RAS mutations, the reported prevalence of RAS mutation in benign lesions ranged from 0% to 48%. In 38 studies examining RET/PTC rearrangements, the prevalence in benign lesions ranged from 0% to 68%. PAX8/PPAR-gamma rearrangements were examined in 27 studies, with the prevalence in benign lesions ranging from 0% to 55%.

CONCLUSION

The presence of these biomarkers and the tremendous variation in reports of their prevalence in benign lesions suggests the need for caution when including these markers in diagnostic decisions. Further understanding of the importance of these markers, as well as newly discovered markers of thyroid malignancy, may be required in order to avoid overtreatment of patients with benign thyroid tumors.

Values of molecular markers in the differential diagnosis of thyroid abnormalities

INTRODUCTION

Thyroid cancer (TC), follicular adenoma (FA) and Hashimoto's thyroiditis (HT) are three of the most frequently reported abnormalities that affect the thyroid gland. A frequent co-occurrence along with similar histopathological features is observed between TC and FA as well as between TC and HT. The conventional diagnostic methods such as histochemical analysis present complications in differential diagnosis when these abnormalities occur simultaneously. Hence, the authors recognize novel methods based on screening genetic defects of thyroid abnormalities as viable diagnostic and prognostic methods that could complement the conventional methods.

METHODS

We have extensively reviewed the existing literature on TC, FA and HT and also on three genes, namely braf, nras and ret/ptc, that could be used to differentially diagnose the three abnormalities. Emphasis was also given to the screening methods available to detect the said molecular markers.

RESULTS AND CONCLUSION

It can be conferred from the analysis of the available data that the utilization of braf, nras and ret/ptc as markers for the therapeutic evaluation of FA and HT is debatable. However, molecular screening for braf, nras and ret/ptc mutations proves to be a conclusive method that could be employed to differentially diagnose TC from HT and FA in the instance of a suspected co-occurrence. Thyroid cancer patients can be highly benefited from the screening for the said genetic markers, especially the braf gene due to its diagnostic value as well as due to the availability of personalized medicine targeted specifically for braf mutants.

Application of molecular biology of differentiated thyroid cancer for clinical prognostication

Although cancer outcome results from the interplay between genetics and environment, researchers are making a great effort for applying molecular biology in the prognostication of differentiated thyroid cancer (DTC). Nevertheless, role of molecular characterisation in the prognostic setting of DTC is still nebulous. Among the most common and well-characterised genetic alterations related to DTC, including mutations of BRAF and RAS and RET rearrangements, BRAF^V600E is the only mutation showing unequivocal association with clinical outcome. Unfortunately, its accuracy is strongly limited by low specificity. Recently, the introduction of next-generation sequencing techniques led to the identification of TERT promoter and TP53 mutations in DTC. These genetic abnormalities may identify a small subgroup of tumours with highly aggressive behaviour, thus improving specificity of molecular prognostication. Although knowledge of prognostic significance of TP53 mutations is still anecdotal, mutations of the TERT promoter have showed clear association with clinical outcome. Nevertheless, this genetic marker needs to be analysed according to a multigenetic model, as its prognostic effect becomes negligible when present in isolation. Given that any genetic alteration has demonstrated, taken alone, enough specificity, the co-occurrence of driving mutations is emerging as an independent genetic signature of aggressiveness, with possible future application in clinical practice. DTC prognostication may be empowered in the near future by non-tissue molecular prognosticators, including circulating BRAF^V600E and miRNAs. Although promising, use of these markers needs to be refined by the technical sight, and the actual prognostic value is still yet to be validated.

Molecular perspectives in differentiated thyroid cancer

Progress in understanding the molecular genetics of thyroid cancer in the last 20 years has accelerated recently with the advent of high-throughput sequencing technologies known as Next-Generation Sequencing. Besides classical molecular abnormalities involving the MAPK (Mitogen Activated Protein Kinase) and PI3K (PhosphoInositide 3-Kinase) pathways that play a key role in follicular-derived thyroid tumorigenesis, new molecular abnormalities have been discovered. The major advances in recent years have been the discovery of new somatic driver gene point mutations (such as RASAL1 [RAS protein activator Like 1] mutations in follicular cancer) and/or mutations that have prognostic value (such as TERT [Telomerase reverse transcriptase] promoter mutations); new chromosomal rearrangements, usually having close connection with exposure to ionizing radiation (such as ALK [Anaplastic Lymphoma Kinase] rearrangements); and deregulation of some gene or microRNA expression representing a molecular signature. Progress made in understanding the molecular mechanisms of thyroid cancer offers new perspectives for the diagnosis of the benign or malignant status of a thyroid nodule, to refine prognosis and offer new perspectives of targeted therapy for radioiodine-refractory cancers.

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the age-dependent sensitivity to radiation carcinogenesis, including the effects of in-utero exposure.

Iodine regulates G2/M progression induced by CCL21/CCR7 interaction in primary cultures of papillary thyroid cancer cells with RET/PTC expression

Treatment with high iodine concentrations can delay oncogenic activation effects, reduce cell growth and return thyroid-specific gene and protein expression levels to normal. During rearranged during transfection (RET)/papillary thyroid carcinoma (PTC) 3 activation, excess iodine can act as a protective agent in thyroid follicular cells. The chemokine receptor CCR7 serves a critical role in lymphocyte trafficking into and within lymph nodes, the preferential metastatic site for PTC. However, the potential associations between chemokine (C‑C motif) ligand 21 (CCL21)/C‑C chemokine receptor type 7 (CCR7) interaction and iodine concentrations in primary cultures of PTC with RET/PTC expression remain unclear. Proliferation assays of primary cultures of PTC cells with RET/PTC1 and RET/PTC3 expression indicated that CCR7 activation by its specific ligand, CCL21, was associated with significantly increased cell proliferation. Flow cytometry data indicated that CCL21/CCR7 interaction significantly increased the fraction of cells in the G2/M phase of the cell cycle. Western blotting indicated that CCL21/CCR7 interaction significantly upregulated cyclin A, cyclin B1 and cyclin‑dependent kinase 1 (CDK1) expression. Western blotting determined that CCL21/CCR7 interaction significantly enhanced the levels of phosphorylated extracellular signal‑regulated kinase (P‑ERK). Co-immunoprecipitation confirmed that there was interaction between P‑ERK and cyclin A, cyclin B1 or CDK1, particularly in the presence of CCL21. Sodium iodide (NaI, 10-5 M) significantly abolished the effects of exogenous CCL21. These results suggest that CCL21/CCR7 interaction contributes to G2/M progression of RET/PTC‑expressing cells via the ERK pathway in association with 10‑5 M NaI.

[Intracellular signaling mechanisms in thyroid cancer]

BACKGROUND

Thyroid cancer is the most common malignancy of the endocrine system, the papillary variant accounts for 80-90% of all diagnosed cases. In the development of papillary thyroid cancer, BRAF and RAS genes are mainly affected, resulting in a modification of the system of intracellular signaling proteins known as «protein kinase mitogen-activated» (MAPK) which consist of «modules» of internal signaling proteins (Receptor/Ras/Raf/MEK/ERK) from the cell membrane to the nucleus. In thyroid cancer, these signanling proteins regulate diverse cellular processes such as differentiation, growth, development and apoptosis. MAPK play an important role in the pathogenesis of thyroid cancer as they are used as molecular biomarkers for diagnostic, prognostic and as possible therapeutic molecular targets. Mutations in BRAF gene have been correlated with poor response to treatment with traditional chemotherapy and as an indicator of poor prognosis.

OBJECTIVE

To review the molecular mechanisms involved in intracellular signaling of BRAF and RAS genes in thyroid cancer.

CONCLUSIONS

Molecular therapy research is in progress for this type of cancer as new molecules have been developed in order to inhibit any of the components of the signaling pathway (RET/PTC)/Ras/Raf/MEK/ERK; with special emphasis on the (RET/PTC)/Ras/Raf section, which is a major effector of ERK pathway.

Selective use of sorafenib in the treatment of thyroid cancer

Sorafenib is a multiple kinase inhibitor (MKI) approved for the treatment of primary advanced renal cell carcinoma and advanced primary liver cancer. It was recently approved by several health agencies around the world as the first available MKI treatment for radioactive iodine-refractory advanced and progressive differentiated thyroid cancer. Sorafenib targets C-RAF, B-RAF, VEGF receptor-1, -2, -3, PDGF receptor-β, RET, c-kit, and Flt-3. As a multifunctional inhibitor, sorafenib has the potential of inhibiting tumor growth, progression, metastasis, and angiogenesis and downregulating mechanisms that protect tumors from apoptosis and has shown to increase the progression-free survival in several Phase II trials. This led to the Phase III trial (DECISION) which showed that there was an improvement in progression-free survival of 5 months for patients on sorafenib when compared to those on placebo. Adverse events with this drug are common but usually manageable. The development of resistance after 1 or 2 years is almost a rule in most patients who showed partial response or stabilization of the disease while on sorafenib, which makes it necessary to think of a plan for subsequent therapies. These may include the use of another MKI, such as lenvatinib, the second approved MKI for advanced differentiated thyroid cancer, or include patients in clinical trials or the off-label use of other MKIs. Given sorafenib's earlier approval, most centers now have access to its prescription. The goal of this review was to improve the care of these patients by describing key aspects that all prescribers will need to master in order to optimize outcomes.

Sorafenib in the treatment of thyroid cancer

Sorafenib has been evaluated in several Phase II and III studies in patients with locally advanced/metastatic radioactive iodine-refractory differentiated thyroid carcinomas (DTCs), reporting partial responses, stabilization of the disease and improvement of progression-free survival. Best responses were observed in lung metastases and minimal responses in bone lesions. On the basis of these studies, sorafenib was approved for the treatment of metastatic DTC in November 2013. Few studies suggested that reduction of thyroglobulin levels, or of average standardized uptake value at the fluorodeoxyglucose-PET, could be helpful for the identification of responding patients; but further studies are needed to confirm these results. Tumor genetic marker levels did not have any prognostic or predictive role in DTC patients.The most common adverse events observed included skin toxicity and gastrointestinal and constitutional symptoms. Encouraging results have also been observed in patients with medullary thyroid cancer. Many studies are ongoing to evaluate the long-term efficacy and tolerability of sorafenib in DTC patients.

Break-apart interphase fluorescence in situ hybridization assay in papillary thyroid carcinoma: on the road to optimizing the cut-off level for RET/PTC rearrangements

OBJECTIVE

Chromosomal rearrangements of the RET proto-oncogene is one of the most common molecular events in papillary thyroid carcinoma (PTC). However, their pathogenic role and clinical significance are still debated. This study aimed to investigate the prevalence of RET/PTC rearrangement in a cohort of BRAF WT PTCs by fluorescence in situ hybridization (FISH) and to search a reliable cut-off level in order to distinguish clonal or non-clonal RET changes.

DESIGN

Forty BRAF WT PTCs were analyzed by FISH for RET rearrangements. As controls, six BRAFV600E mutated PTCs, 13 follicular adenomas (FA), and ten normal thyroid parenchyma were also analyzed.

METHODS

We performed FISH analysis on formalin-fixed, paraffin-embedded tissue using a commercially available RET break-apart probe. A cut-off level equivalent to 10.2% of aberrant cells was accepted as significant. To validate FISH results, we analyzed the study cohort by qRT-PCR.

RESULTS

Split RET signals above the cut-off level were observed in 25% (10/40) of PTCs, harboring a percentage of positive cells ranging from 12 to 50%, and in one spontaneous FA (1/13, 7.7%). Overall, the data obtained by FISH matched well with qRT-PCR results. Challenging findings were observed in five cases showing a frequency of rearrangement very close to the cut-off.

CONCLUSIONS

FISH approach represents a powerful tool to estimate the ratio between broken and non-broken RET tumor cells. Establishing a precise FISH cut-off may be useful in the interpretation of the presence of RET rearrangement, primarily when this strategy is used for cytological evaluation or for targeted therapy.

Hypothesis: Artifacts, Including Spurious Chimeric RNAs with a Short Homologous Sequence, Caused by Consecutive Reverse Transcriptions and Endogenous Random Primers

Recent RNA-sequencing technology and associated bioinformatics have led to identification of tens of thousands of putative human chimeric RNAs, i.e. RNAs containing sequences from two different genes, most of which are derived from neighboring genes on the same chromosome. In this essay, we redefine "two neighboring genes" as those producing individual transcripts, and point out two known mechanisms for chimeric RNA formation, i.e. transcription from a fusion gene or trans-splicing of two RNAs. By our definition, most putative RNA chimeras derived from canonically-defined neighboring genes may either be technical artifacts or be cis-splicing products of 5'- or 3'-extended RNA of either partner that is redefined herein as an unannotated gene, whereas trans-splicing events are rare in human cells. Therefore, most authentic chimeric RNAs result from fusion genes, about 1,000 of which have been identified hitherto. We propose a hypothesis of "consecutive reverse transcriptions (RTs)", i.e. another RT reaction following the previous one, for how most spurious chimeric RNAs, especially those containing a short homologous sequence, may be generated during RT, especially in RNA-sequencing wherein RNAs are fragmented. We also point out that RNA samples contain numerous RNA and DNA shreds that can serve as endogenous random primers for RT and ensuing polymerase chain reactions (PCR), creating artifacts in RT-PCR.

BRAF(V600E) Mutation, RET/PTC1 and PAX8-PPAR Gamma Rearrangements in Follicular Epithelium Derived Thyroid Lesions - Institutional Experience and Literature Review

BACKGROUND

Thyroid cancers are the most frequently occurring endocrine malignancy worldwide. In Turkey, thyroid cancers are ranked 2(nd) on the incidence list in women, with a rate of 16.2%, but they are not included among the top 10 cancer types in men.

AIMS

To identify the contribution of the BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements in the diagnosis and differential diagnosis of follicular epithelial-derived thyroid lesions.

STUDY DESIGN

Retrospective clinical and molecular genetic study.

METHODS

A total of 86 thyroid cases diagnosed between 2001 and 2012 at the Department of Pathology were included in the retrospective study group. Samples best representing the lesion and comprising capsules were chosen in the selection of paraffin blocks pertaining to the cases. The BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements were investigated in all cases.

RESULTS

The BRAF(V600E) mutation was observed in 12 out of 37 papillary carcinoma cases (32.4%), in 1 out of 15 follicular carcinoma cases (6.6%), and in 1 out of 7 undifferentiated carcinoma cases (14.3%). No mutation was detected in benign lesions. The RET/PTC1 rearrangement was detected in 2 out of 7 undifferentiated carcinoma cases (28.6%), and in 1 out of 15 follicular carcinoma cases (6.6%). No gene rearrangement was detected in benign lesions. The PAX8-PPARγ rearrangement was detected in 5 out of 15 follicular thyroid carcinoma cases (33.3%) and in 1 out of 15 follicular adenoma cases (6.6%).

CONCLUSION

The BRAF(V600E) mutation and RET/PTC1 rearrangement were effective in distinguishing the follicular epithelium-derived benign and malignant lesions of the thyroid in the resection materials. The BRAF(V600E) mutation was rather specific to papillary carcinoma in the thyroid, and in cases where the BRAF(V600E) mutation was detected, multi-centricity, lymph node metastasis and capsular invasion findings were observed more frequently compared to cases in which no mutation was observed. The PAX8-PPARγ rearrangement was observed to be more effective in the differentiation of adenomas and carcinomas in follicular neoplasms of the thyroid, whereas the RET/PTC1 analysis contributed to the differential diagnosis of papillary carcinoma histogenesis at a frequency of 29% in undifferentiated thyroid carcinomas.

Relevance of BRAF(V600E) mutation testing versus RAS point mutations and RET/PTC rearrangements evaluation in the diagnosis of thyroid cancer

BACKGROUND

A molecular profile including BRAF and RAS mutations as well as RET/PTC rearrangement evaluation has been proposed to provide an accurate presurgical assessment of thyroid nodules and to reduce the number of unnecessary diagnostic surgeries, sparing patients' health and saving healthcare resources. However, the application of such molecular analyses may provide different results among different centers and populations in real-life settings. Our aims were to evaluate the diagnostic utility of assessing the presence of BRAF and RAS mutations and RET/PTC1 and RET/PTC3 rearrangements in all cytological categories in an Italian group of thyroid nodule patients assessed prospectively, and to understand whether and which mutation testing might be helpful in cytologically indeterminate nodules.

METHODS

A total of 911 patients were submitted to ultrasound and fine-needle aspiration biopsy examination. Cytological evaluation was performed in parallel with molecular testing and compared to pathological results in 940 thyroid nodules, including 140 indeterminate lesions.

RESULTS

BRAF mutation testing provided the best contribution to cancer diagnosis, allowing the disease to be detected at an early stage, and identifying indeterminate nodules in which diagnostic lobectomy could be spared. On the contrary, RAS and RET/PTC analysis did not further increase diagnostic sensitivity for thyroid cancer. In addition, we found RET/PTC rearrangements in benign lesions, indicating that this molecular marker might not be useful for the detection of thyroid cancer.

CONCLUSION

BRAF(V600E) mutation analysis is superior to RAS point mutations and evaluation of RET/PTC rearrangements in the diagnosis of thyroid cancer, even in indeterminate lesions.

Thyroid nodules: pathophysiological insight on oncogenesis and novel diagnostic techniques

Thyroid nodules are a very frequent pathology among common population. Despite the vast majority of them are of benign origin, the incidence of thyroid cancer is currently rather rising. Although there are several risk factors of thyroid cancer and several clinical, ultrasound, biochemical and molecular diagnostic markers, the exact mechanisms of thyroid oncogenesis and the linkage between thyroid nodule ultrasound appearance and its biological character remain unclear. While ionizing radiation is the only one well-known risk factor for thyroid cancer, the significance of some others remains unclear. The aim of our review was to discuss some not completely known pathophysiological mechanisms involved in thyroid oncogenesis as hypothyroidism, mutations of genes regulating cell proliferation, thyroid autoimmunity and pregnancy and to describe pathophysiological background of some ultrasound markers of thyroid cancer (size, echogenicity, vascularization, calcifications and stiffness). Better knowledge in this field is crucial for development of novel diagnostic techniques and therapeutic approaches. For example, the analysis of BRAF, RAS and other mutations in cytological samples may help to distinction between follicular thyroid carcinoma and follicular thyroid adenoma and may significantly decrease the number of unnecessary surgery among patients with thyroid nodules. Alternatively, the different malign cells growth, angiogenesis, destructions of thyroid follicles, reparative changes, growth retardation, fibrosis and increased interstitial fluid pressure implicate the typical ultrasound appearance of papillary thyroid cancer (hypoechogenicity, irregular vascularization, microcalcifications, stiffness) which is essential to catch the suspicious nodules on the basis of their ultrasound appearance among large amount of benign nodules.

Molecular Targeted Therapies of Aggressive Thyroid Cancer

Differentiated thyroid carcinomas (DTCs) that arise from follicular cells account >90% of thyroid cancer (TC) [papillary thyroid cancer (PTC) 90%, follicular thyroid cancer (FTC) 10%], while medullary thyroid cancer (MTC) accounts <5%. Complete total thyroidectomy is the treatment of choice for PTC, FTC, and MTC. Radioiodine is routinely recommended in high-risk patients and considered in intermediate risk DTC patients. DTC cancer cells, during tumor progression, may lose the iodide uptake ability, becoming resistant to radioiodine, with a significant worsening of the prognosis. The lack of specific and effective drugs for aggressive and metastatic DTC and MTC leads to additional efforts toward the development of new drugs. Several genetic alterations in different molecular pathways in TC have been shown in the past few decades, associated with TC development and progression. Rearranged during transfection (RET)/PTC gene rearrangements, RET mutations, BRAF mutations, RAS mutations, and vascular endothelial growth factor receptor 2 angiogenesis pathways are some of the known pathways determinant in the development of TC. Tyrosine kinase inhibitors (TKIs) are small organic compounds inhibiting tyrosine kinases auto-phosphorylation and activation, most of them are multikinase inhibitors. TKIs act on the aforementioned molecular pathways involved in growth, angiogenesis, local, and distant spread of TC. TKIs are emerging as new therapies of aggressive TC, including DTC, MTC, and anaplastic thyroid cancer, being capable of inducing clinical responses and stabilization of disease. Vandetanib and cabozantinib have been approved for the treatment of MTC, while sorafenib and lenvatinib for DTC refractory to radioiodine. These drugs prolong median progression-free survival, but until now no significant increase has been observed on overall survival; side effects are common. New efforts are made to find new more effective and safe compounds and to personalize the therapy in each TC patient.

Ras oncoprotein disrupts the TSH/CREB signaling upstream adenylyl cyclase in human thyroid cell

Activating mutations in RAS genes and p21 Ras overactivation are common occurrences in a variety of human tumors. p21 Ras oncoproteins deregulate a number of signaling pathways, dedifferentiating the thyroid cell, and negatively regulating the expression of thyroid specific genes. In rat thyroid cells, Ras oncoproteins inhibit the TSH pathway by reducing PKA activity and thus the expression of thyroid specific genes, while in mouse melanocytes, Ras oncoproteins reduce the αMSH-stimulated cAMP signaling by increasing the expression of the phosphodiesterase-4B. Given these cell-dependent differences, we investigated if and how the TSH/CREB pathway is modulated by Ras oncoprotein in a human thyroid cell line. CREB phosphorylation was stimulated by TSH and forskolin in TAD-2 cells. Ras(V12) expression negatively regulated the TSH-stimulated CREB phosphorylation but was ineffective on forskolin-stimulated CREB phosphorylation. Phosphodiesterase inhibition by IBMX enhanced TSH-stimulated CREB phosphorylation, but did not restore TSH-stimulated CREB phosphorylation inhibited by Ras oncoprotein. These data indicate that Ras oncoprotein disrupts the TSH/CREB pathway, upstream adenylyl cyclase, and highlight the existence of mechanisms of interaction between Ras and the cAMP pathway different in human and in rat thyroid cells.

Gain of copy number and amplification of the RET gene in lung cancer

RET rearrangement represents a unique molecular subset of lung cancer. The identification of specific clinicopathologic characteristics and RET gene status would provide critical information on targeted therapeutics. In this study, we investigated the patterns of RET gene in a series of lung carcinomas. Of one hundred and sixteen tumors, a low frequency (1.7%) of RET translocation was identified. Only two specimens of lung adenocarcinomas displayed the rearrangement of RET in 54% and 78% of tumor cells respectively. A high incidence of gain of copy number (3-4 copies) and amplification (≥ 5 copies) of the RET gene was observed in 52% and 12% of all 116 samples. An association between increased copy number of RET and EGFR mutation was statistically significant (p < 0.05) in these lung carcinomas. This study sheds light on the unique molecular characteristics of the RET gene in lung carcinomas.

Effects of siRNA on RET/PTC3 junction oncogene in papillary thyroid carcinoma: from molecular and cellular studies to preclinical investigations

RET/PTC3 junction oncogene is typical of radiation-induced childhood papillary thyroid carcinoma (PTC) with a short latency period. Since, RET/PTC3 is only present in the tumour cells, thus represents an interesting target for specific therapy by small interfering RNA (siRNA). Our aim is to demonstrate in vitro and in vivo molecular and cellular effects of siRNA on RET/PTC3 knockdown for therapeutic application.First, we established a novel cell line stably expressing RET/PTC3 junction oncogene, named RP3 which was found tumorigenic in nude mice compared to NIH/3T3 mouse fibroblasts. Among four siRNAs and five concentrations tested against RET/PTC3, an efficient siRNA RET/PTC3 and an appropriate dose (50 nM) were selected which showed significant inhibition (p<0.001) of gene (RT-qPCR) and protein (Western blot) expressions. This siRNA was found efficient in RP3 cells (harbouring RET/PTC3) but non-efficient in BHP10-3 SCmice cell line (harbouring RET/PTC1) showing that a specific siRNA against fusion sequence is required to target the junction oncogene. In vitro siRNA RET/PTC3 showed significant (p<0.001) inhibitory effects on RP3 cell viability (MTT assay) and on invasion/migration (IncuCyte scratch test) with blockage of cell cycle at G0/G1 phase (flow cytometry) and induced apoptosis by caspase-3 and PARP1 cleavage (WB). After intravenous injection in nude mice, respective squalene (SQ) nanoparticles (NPs) of siRNA RET/PTC3 significantly (p<0.001) reduced RP3 tumour growth, oncogene and oncoprotein expressions, induced apoptosis and partially restored differentiation (decrease in Ki67). Hence, our findings highly support the use of siRNA RET/PTC3-SQ NPs as a new promising treatment for patients affected by PTC expressing RET/PTC3.