Selumetinib-enhanced radioiodine uptake in advanced thyroid cancer

Iodide transport: implications for health and disease

Disorders of the thyroid gland are among the most common conditions diagnosed and managed by pediatric endocrinologists. Thyroid hormone synthesis depends on normal iodide transport and knowledge of its regulation is fundamental to understand the etiology and management of congenital and acquired thyroid conditions such as hypothyroidism and hyperthyroidism. The ability of the thyroid to concentrate iodine is also widely used as a tool for the diagnosis of thyroid diseases and in the management and follow up of the most common type of endocrine cancers: papillary and follicular thyroid cancer. More recently, the regulation of iodide transport has also been the center of attention to improve the management of poorly differentiated thyroid cancer. Iodine deficiency disorders (goiter, impaired mental development) due to insufficient nutritional intake remain a universal public health problem. Thyroid function can also be influenced by medications that contain iodide or interfere with iodide metabolism such as iodinated contrast agents, povidone, lithium and amiodarone. In addition, some environmental pollutants such as perchlorate, thiocyanate and nitrates may affect iodide transport. Furthermore, nuclear accidents increase the risk of developing thyroid cancer and the therapy used to prevent exposure to these isotopes relies on the ability of the thyroid to concentrate iodine. The array of disorders involving iodide transport affect individuals during the whole life span and, if undiagnosed or improperly managed, they can have a profound impact on growth, metabolism, cognitive development and quality of life.

The role of preclinical models in radiopharmaceutical therapy

Radiopharmaceutical therapy (RPT) is a treatment modality that involves the use of radioactively labeled targeting agents to deliver a cytotoxic dose of radiation to tumor while sparing normal tissue. The biologic function of the target and the biologic action of the targeting agent is largely irrelevant as long as the targeting agent delivers cytotoxic radiation to the tumor. Preclinical RPT studies use imaging and ex vivo evaluation of radioactivity concentration in target and normal tissues to obtain biodistribution and pharmacokinetic data that can be used to evaluate radiation absorbed doses. Since the efficacy and toxicity of RPT depend on radiation absorbed dose, this quantity can be used to translate results from preclinical studies to human studies. The absorbed dose can also be used to customize therapy to account for pharmacokinetic and other differences among patients so as to deliver a prespecified absorbed dose to the tumor or to dose-limiting tissue. The combination of RPT with other agents can be investigated and optimized by identifying the effect of other agents on tumor or normal tissue radiosensitivity and also on how other agents change the absorbed dose to these tissues. RPT is a distinct therapeutic modality whose mechanism of action is well understood. Measurements can be made in preclinical models to help guide clinical implementation of RPT and optimize combination therapy using RPT.

Time to re-consider the meaning of BRAF V600E mutation in papillary thyroid carcinoma

The BRAF V600E mutation, resulting from the BRAFT1799A transversion, is the most common genetic mutation in papillary thyroid carcinoma (PTC), with a mean frequency close to 50% among all cases. A large number of studies in the past decade have tried to dissect the relevance and the function of the V600E mutation in controlling oncogenesis and progression of thyroid cancer. However, several works published in the latest years have provided new evidence, in partial conflict with the previous knowledge, suggesting the need of reconsidering the meaning of the BRAF V600E mutation in PTC. In this work, we attempt to discuss some of the most recent molecular, preclinical and clinical evidence to construct a more exhaustive model of function for the BRAF V600E in development, progression and therapeutic approach of thyroid cancer.

The clinical development of MEK inhibitors

Aberrant activation of the RAS-RAF-MEK-ERK1/2 pathway occurs in more than 30% of human cancers. As part of this pathway, MEK1 and MEK2 have crucial roles in tumorigenesis, cell proliferation and inhibition of apoptosis and, therefore, MEK1/2 inhibition is an attractive therapeutic strategy in a number of cancers. Highly selective and potent non-ATP-competitive allosteric MEK1/2 inhibitors have been developed and assessed in numerous clinical studies over the past decade. These agents are not efficacious in a broad range of unselected cancers, although single-agent antitumour activity has been detected mainly in tumours that harbour mutations in genes encoding the members of the RAS and RAF protein families, such as certain melanomas. Combinations of MEK1/2 inhibitors and cytotoxic chemotherapy, and/or other targeted agents are being studied to expand the efficacy of this class of agents. Identifying predictive biomarkers, and delineating de novo and acquired resistance mechanisms are essential for the future clinical development of MEK inhibitors. We discuss the clinical experience with MEK inhibitors to date, and consider the novel approaches to MEK-inhibitor therapy that might improve outcomes and lead to the wider use of such treatments.

Apigenin in combination with Akt inhibition significantly enhances thyrotropin-stimulated radioiodide accumulation in thyroid cells

BACKGROUND

Selectively increased radioiodine accumulation in thyroid cells by thyrotropin (TSH) allows targeted treatment of thyroid cancer. However, the extent of TSH-stimulated radioiodine accumulation in some thyroid tumors is not sufficient to confer therapeutic efficacy. Hence, it is of clinical importance to identify novel strategies to selectively further enhance TSH-stimulated thyroidal radioiodine accumulation.

METHODS

PCCl3 rat thyroid cells, PCCl3 cells overexpressing BRAF(V600E), or primary cultured tumor cells from a thyroid cancer mouse model, under TSH stimulation were treated with various reagents for 24 hours. Cells were then subjected to radioactive iodide uptake, kinetics, efflux assays, and protein extraction followed by Western blotting against selected antibodies.

RESULTS

We previously reported that Akt inhibition increased radioiodine accumulation in thyroid cells under chronic TSH stimulation. Here, we identified Apigenin, a plant-derived flavonoid, as a reagent to further enhance the iodide influx rate increased by Akt inhibition in thyroid cells under acute TSH stimulation. Akt inhibition is permissive for Apigenin's action, as Apigenin alone had little effect. This action of Apigenin requires p38 MAPK activity but not PKC-δ. The increase in radioiodide accumulation by Apigenin with Akt inhibition was also observed in thyroid cells expressing BRAF(V600E) and in primary cultured thyroid tumor cells from TRβ(PV/PV) mice.

CONCLUSION

Taken together, Apigenin may serve as a dietary supplement in combination with Akt inhibitors to enhance therapeutic efficacy of radioiodine for thyroid cancer.

Update: the status of clinical trials with kinase inhibitors in thyroid cancer

CONTEXT

Thyroid cancer is usually cured by timely thyroidectomy; however, the treatment of patients with advanced disease is challenging because their tumors are mostly unresponsive to conventional therapies. Recently, the malignancy has attracted much interest for two reasons: the dramatic increase in its incidence over the last three decades, and the discovery of the genetic mutations or chromosomal rearrangements causing most histological types of thyroid cancer.

OBJECTIVE

This update reviews the molecular genetics of thyroid cancer and the clinical trials evaluating kinase inhibitors (KIs) in patients with locally advanced or metastatic disease. The update also reviews studies in other malignancies, which have identified mechanisms of efficacy, and also resistance, to specific KIs. This information has been critical both to the development of effective second-generation drugs and to the design of combinatorial therapeutic regimens. Finally, the update addresses the major challenges facing clinicians who seek to develop more effective therapy for patients with thyroid cancer.

RESULTS

PubMed was searched from January 2000 to November 2013 using the following terms: thyroid cancer, treatment of thyroid cancer, clinical trials in thyroid cancer, small molecule therapeutics, kinase inhibitors, and next generation sequencing.

CONCLUSIONS

A new era in cancer therapy has emerged based on the introduction of KIs for the treatment of patients with liquid and solid organ malignancies. Patients with thyroid cancer have benefited from this advance and will continue to do so with the development of drugs having greater specificity and with the implementation of clinical trials of combined therapeutics to overcome drug resistance.

Sodium iodide symporter (NIS) in extrathyroidal malignancies: focus on breast and urological cancer

Background

Expression and function of sodium iodide symporter (NIS) is requisite for efficient iodide transport in thyrocytes, and its presence in cancer cells allows the use of radioiodine as a diagnostic and therapeutic tool in thyroid neoplasia. Discovery of NIS expression in extrathyroidal tissues, including transformed cells, has opened a novel field of research regarding NIS-expressing extrathyroidal neoplasia. Indeed, expression of NIS may be used as a biomarker for diagnostic, prognostic, and therapeutic purposes. Moreover, stimulation of endogenous NIS expression may permit the radioiodine treatment of extrathyroidal lesions by concentrating this radioisotope.

Results

This review describes recent findings in NIS research in extrathyroidal malignancies, focusing on breast and urological cancer, emphasizing the most relevant developments that may have clinical impact.

Conclusions

Given the recent progress in the study of NIS regulation as molecular basis for new therapeutic approaches in extrathyroidal cancers, particular attention is given to studies regarding the relationship between NIS and clinical-pathological aspects of the tumors and the regulation of NIS expression in the experimental models.

Activating BRAF and PIK3CA mutations cooperate to promote anaplastic thyroid carcinogenesis

Thyroid malignancies are the most common type of endocrine tumors. Of the various histologic subtypes, anaplastic thyroid carcinoma (ATC) represents a subset of all cases but is responsible for a significant proportion of thyroid cancer-related mortality. Indeed, ATC is regarded as one of the more aggressive and hard to treat forms of cancer. To date, there is a paucity of relevant model systems to critically evaluate how the signature genetic abnormalities detected in human ATC contribute to disease pathogenesis. Mutational activation of the BRAF protooncogene is detected in approximately 40% of papillary thyroid carcinoma (PTC) and in 25% of ATC. Moreover, in ATC, mutated BRAF is frequently found in combination with gain-of-function mutations in the p110 catalytic subunit of PI3'-Kinase (PIK3CA) or loss-of-function alterations in either the p53 (TP53) or PTEN tumor suppressors. Using mice with conditional, thyrocyte-specific expression of BRAF(V600E), we previously developed a model of PTC. However, as in humans, BRAF(V600E)-induced mouse PTC is indolent and does not lead to rapid development of end-stage disease. Here, we use mice carrying a conditional allele of PIK3CA to demonstrate that, although mutationally activated PIK3CA(H1047R) is unable to drive transformation on its own, when combined with BRAF(V600E) in thyrocytes, this leads to development of lethal ATC in mice. Combined, these data demonstrate that the BRAF(V600E) cooperates with either PIK3CA(H1074R) or with silencing of the tumor-suppressor PTEN, to promote development of anaplastic thyroid carcinoma.

IMPLICATIONS

This genetically relevant mouse model of ATC will be an invaluable platform for preclinical testing of pathway-targeted therapies for the prevention and treatment of thyroid carcinoma.

Genetics and epigenetics of sporadic thyroid cancer

Thyroid carcinoma is the most common endocrine malignancy, and although the disease generally has an excellent prognosis, therapeutic options are limited for patients not cured by surgery and radioiodine. Thyroid carcinomas commonly contain one of a small number of recurrent genetic mutations. The identification and study of these mutations has led to a deeper understanding of the pathophysiology of this disease and is providing new approaches to diagnosis and therapy. Papillary thyroid carcinomas usually contain an activating mutation in the RAS cascade, most commonly in BRAF and less commonly in RAS itself or through gene fusions that activate RET. A chromosomal translocation that results in production of a PAX8-PPARG fusion protein is found in follicular carcinomas. Anaplastic carcinomas may contain some of the above changes as well as additional mutations. Therapies that are targeted to these mutations are being used in patient care and clinical trials.

Sorafenib in the treatment of radioiodine-refractory differentiated thyroid cancer: a meta-analysis

The advent of biologically targeted agents and increased understanding of thyroid carcinogenesis have generated much interest in the development of biologically targeted therapeutic agents for thyroid cancer. Among them, sorafenib is the most commonly studied drug. The current meta-analysis was carried out to estimate the efficacy and safety of sorafenib administered in radioiodine-refractory differentiated thyroid cancer patients. An electronic search was conducted using PubMed/MEDLINE and EMBASE. Statistical analyses were carried out using either random-effects or fixed-effects models according to heterogeneity. All the statistical analyses were carried out using the Stata version 12.0 software. Seven eligible studies were identified. The final results indicated that 22% of the patients (95% CI: 15-28) achieved a partial response. Hand-foot syndrome, diarrhea, fatigue, rash, weight loss, and hypertension were the most frequently observed adverse effects (AEs) associated with sorafenib use and the incidence of these AEs (all grades) was 80% (95% CI: 68-91), 68% (95% CI: 59-77), 67% (95% CI: 57-78), 66% (95% CI: 50-82), 52%(95% CI: 33-72), and 31% (95% CI: 21-42) respectively. Sixty-two percent (95% CI: 36-89) patients required dose reductions due to toxicity of sorafenib. As far as PR and AEs are concerned, the results of this meta-analysis indicate that sorafenib has a modest effect in patients with radioiodine-refractory differentiated thyroid cancer and the high incidence of AEs associated with this agent may affect the quality of patients' lives. Though the use of sorafenib in the treatment of radioiodine-refractory differentiated thyroid cancer is considered promising by most physicians working in this field, more effective agents with less toxicity and cost are still needed.

Differentiated thyroid cancer: a new perspective with radiolabeled somatostatin analogues for imaging and treatment of patients

BACKGROUND

The expression of somatostatin receptors (SSTR) in thyroid cells may offer the possibility to identify metastatic lesions and to select patients for peptide receptor radionuclide therapy (PRRT). We investigated (68)Ga-DOTATOC positron emission tomography/computed tomography (PET/CT) to select patients with progressive differentiated thyroid cancer (DTC) for PRRT as well as treatment response and toxicity in treated patients.

METHODS

We enrolled 41 patients with progressive radioiodine-negative DTC (24 women and 17 men; mean age=54.3 years, median=59 years, range=19-78 years). In all patients, [(18)F]FDG-PET/CT was performed to determine recurrent disease with enhanced glucose metabolism, and (68)Ga-DOTATOC PET/CT was used to identify SSTR expression. Dosimetric evaluation was performed with (111)In-DOTATOC scintigraphy. Eleven patients were treated with PRRT receiving a fractionated injection of 1.5-3.7 GBq (90)Y-DOTATOC/administration. Serial (68)Ga-DOTATOC PET/CT scans were performed in all treated patients to evaluate treatment response. Parameters provided by (68)Ga-DOTATOC PET/CT were analyzed as potential therapeutic predictors to differentiate responding from nonresponding. In all treated patients, adverse events and toxicity were recorded.

RESULTS

(68)Ga-DOTATOC PET/CT were positive in 24/41 of radioiodine-negative DTC patients. Based on the high expression of SSTR detected by (68)Ga-DOTATOC PET/CT, 13 patients were suitable for PRRT. Two out of 13 patients were not treated due to the lack of fulfillment of other study inclusion criteria. PRRT induced disease control in 7/11 patients (two partial response and five stabilization) with a duration of response of 3.5-11.5 months. Objective response was associated with symptoms relief. Functional volume (FV) over time obtained by PET/CT was the only parameter demonstrating a significant difference between lesions responding and nonresponding to PRRT (p=0.001). Main PRRT adverse events were nausea, asthenia, and transient hematologic toxicity. One patient experienced permanent renal toxicity.

CONCLUSIONS

In our series, SSTR imaging provided positive results in more than half of the cases with radioiodine-negative DTC, and about one third of patients were eligible for PRRT. (68)Ga-DOTATOC PET/CT seems a reliable tool both for patient selection and evaluation of treatment response. In our experience, FV determination over time seems to represent a reliable parameter to determine tumor response to PRRT, although further investigations are needed to better define its role.

BRAFV600E-mutation is invariably present and associated to oncogene-induced senescence in Erdheim-Chester disease

OBJECTIVES

Erdheim-Chester disease (ECD) is a rare form of histiocytosis characterised by uncontrolled chronic inflammation. The oncogenic BRAF(V600E) mutation has been reported in biopsies in 19 out of 37 patients with ECD from the largest published cohort, but never found in the patients' peripheral blood. Also, the role of the mutation in the pathogenesis of the disease has not been elucidated yet. BRAF(V600E) has been associated with oncogene-induced senescence (OIS), a protective mechanism against oncogenic events, characterised by the induction of proinflammatory pathways.

METHODS

We verified the BRAF status in biopsies and peripheral blood from 18 patients with ECD from our cohort and matched controls by means of immunohistochemistry and of an ultrasensitive assay, based on the combination of a locked nucleic acid PCR and pyrosequencing. Droplet digital PCR was used to confirm the findings. We also evaluated the presence of senescence markers in ECD histiocytes.

RESULTS

BRAF(V600E) mutation was present in all the biopsy and peripheral blood samples from patients with ECD and in none of the controls. ECD histiocytes and a fraction of circulating monocytes from patients with ECD showed signs of a constitutive activation of the MAPK pathway. Moreover, BRAF-mutated histiocytes expressed markers of OIS.

CONCLUSIONS

The oncogenic BRAF(V600E) mutation is present in biopsies and in the peripheral blood from all patients with ECD who were evaluated and is associated with OIS. These findings have significant implications for the pathogenesis, diagnosis and treatment of ECD.

Prospects for MEK inhibitors for treating cancer

INTRODUCTION

The MAPK pathway is a signaling network that plays a key role in many normal cellular processes and in a large number of human malignancies. One of its effectors, MEK, is essential for the carcinogenesis of different tumors. In recent years, several drugs able to inhibit MEK have been assessed in clinical trials. Trametinib has recently become the first MEK inhibitor licensed for cancer treatment (advanced melanoma).

AREAS COVERED

We comprehensively review the safety and clinical efficacy of the family of MEK inhibitors, either alone or in combination with other drugs. We discuss data ranging from the Phase III trial of trametinib in melanoma to the most recent drugs with early signs of antitumor activity. In addition, we explain the reasons for the unsuccessful results of the early trials with MEK inhibitors and provide a view of their role in cancer treatment in forthcoming years.

EXPERT OPINION

MEK inhibitors are a potentially safe and active treatment option for the treatment of many human malignancies. The information provided by a large series of studies currently ongoing will be very valuable in order to optimize their use. Adequate selection of patients is crucial for achieving successful results with these compounds.

New therapeutic options for advanced forms of thyroid cancer

INTRODUCTION

While the vast majority of patients with thyroid cancer have an excellent prognosis, those with more aggressive courses experience significant morbidity and mortality. Advanced forms of thyroid cancer are typically refractory to standard therapy. Numerous agents with potential usefulness in the treatment of advanced thyroid cancer have recently come under study.

AREAS COVERED

This article reviews agents identified through a systematic review of the scientific literature as being under investigation for treatment of advanced thyroid cancer. A search of both PubMed and the NCI Clinical Trials website was performed to identify such agents having reached Phase II or III testing. Improved understanding of cancer cell signaling pathways has led to the identification of > 500 kinases as potential therapeutic targets. Additional agents of interest include those that inhibit neoangiogenesis, alter epigenetic factors or stimulate antitumor immune reactions. While presently available agents have shown promise in improving progression-free survival (PFS), complete responses are not seen and significant adverse side effects are encountered.

EXPERT OPINION

The development of numerous new anticancer agents holds the promise of treatment regimens that will extend PFS and ultimately overall survival in patients with advanced thyroid cancer. Anticipated future developments include individualized, multimodal treatment regimens based on specific tumor cell biology and driver mutations.

Sorafenib in metastatic thyroid cancer: a systematic review

BACKGROUND

Sorafenib was recently approved by the U.S. Food and Drug Administration for radioiodine-resistant metastatic differentiated thyroid cancer (DTC). In addition, two drugs (vandetanib and cabozantinib) have received U.S. Food and Drug Administration approval for use in medullary thyroid cancer (MTC). Several published phase II trials have investigated the efficacy of sorafenib in thyroid cancers, but to date, results from those studies have not been compared.

METHODS

A systematic review of the literature was performed to assess response rate, median progression-free survival, and adverse events associated with sorafenib therapy for metastatic thyroid cancers.

RESULTS

This review included seven trials involving 219 patients: 159 with DTC (papillary, follicular, and poorly differentiated), 52 with MTC, and 8 with anaplastic thyroid cancer. No study reported complete responses to treatment. Overall partial response, stable disease, and progressive disease rates were 21%, 60%, and 20%, respectively. The median progression-free survival was 18 months for patients with all subtypes of thyroid cancer. Drug was discontinued in 16% of patients because of toxicities or intolerance, and the dose was reduced in a further 56%. Side effects with an incidence ≥ 50% were hand-foot syndrome (74%), diarrhea (70%), skin rash (67%), fatigue (61%), and weight loss (57%). Deaths not related to progressive disease occurred in nearly 4% of patients.

CONCLUSION

Treatment with sorafenib in patients with progressive DTC and MTC is a promising strategy, but the adverse event rate is high, leading to a high rate of dose reduction or discontinuation. Consequently, sorafenib use in patients with metastatic thyroid cancer requires careful selection of patients and careful management of side effects.

Thyroid cancer in 2013: Advances in our understanding of differentiated thyroid cancer

Studies published in 2013 have addressed the question of whether the rising incidence of differentiated thyroid cancer is actually the result of overdiagnosis. Advances have also been made in the treatment of differentiated thyroid cancer, including improvements in radioiodine therapy.

Genome-wide methylation patterns in papillary thyroid cancer are distinct based on histological subtype and tumor genotype

CONTEXT

Aberrant DNA methylation is known to be a major factor in oncogenesis and cancer progression, but effects of methylation in papillary thyroid cancer (PTC) are not well defined.

OBJECTIVE

The objective of the study was to identify altered methylation patterns, which may be associated with PTC disease behavior.

DESIGN

This study was a genome-wide methylation analysis of PTC.

SETTING

The study was conducted at the National Institutes of Health Clinical Center.

PATIENTS

PTC tissue from 51 patients were analyzed and compared with normal thyroid tissue from seven patients.

INTERVENTIONS

CpG methylation status was assessed using advanced genome-wide methylation bead chips.

OUTCOME MEASURES

Altered methylation patterns in PTC were analyzed by stage, recurrence, histological subtype of tumor, and tumor genotype.

RESULTS

PTC is globally hypomethylated compared with normal thyroid with 2837 differentially methylated CpG sites. The follicular variant of PTC demonstrated less differential methylation with only 569 differentially methylated CpG sites. Tumors with mutations in BRAF, RET/PTC, and RAS demonstrated a 3.6-fold increase in the number of differentially methylated sites compared with wild-type tumors. The differentially methylated genes were associated with oncological pathways including cellular movement, growth, and proliferation.

CONCLUSION

PTC is epigenetically distinct from the follicular variant of PTC and by gene mutation status (BRAF, RET/PTC, and RAS).

Long-term prognosis of differentiated thyroid cancer with lung metastasis in Korea and its prognostic factors

BACKGROUND

Distant metastasis, generally to lung and bone, is rare in differentiated thyroid carcinoma (DTC) and the prognosis is still elusive. We investigated long-term outcomes of lung metastasis in DTC patients and its prognostic factors.

METHODS

A retrospective review was performed of 4572 patients who underwent surgery for DTC from 1962 to 2009 at Seoul National University Hospital. Among them, 164 patients were identified with lung metastasis and 152 patients were enrolled in the final analysis. Poor prognosis was defined as progressive disease or death.

RESULTS

Of these 152 patients, 10- and 20-year survival rates were 85.0% and 71.0%, respectively. No evidence of disease, stable disease, progressive disease, and death was identified in 22.4%, 28.3%, 35.5%, and 13.8%, respectively, after 11 years of median follow-up (range 2-41 years). Older age at diagnosis (≥45 years), primary tumor size ≥2 cm, follicular thyroid cancer, metastasis diagnosed after initial evaluation or (131)I remnant ablation (late metastasis), multiple metastases other than lung, (131)I nonavidity, and the presence of macronodules (≥1 cm) were more frequent in poor prognoses. Cox proportional hazard ratio for progression-free survival showed that (131)I nonavidity was the only independent predictive factor for poor prognosis.

CONCLUSIONS

The prognosis of lung metastasis from DTC in Korea within this study was favorable. (131)I nonavidity, observed more frequently in late metastasis, was the only independent factor predicting poor prognosis.

The Na+/I- symporter (NIS): mechanism and medical impact

The Na(+)/I(-) symporter (NIS) is the plasma membrane glycoprotein that mediates active I(-) transport in the thyroid and other tissues, such as salivary glands, stomach, lactating breast, and small intestine. In the thyroid, NIS-mediated I(-) uptake plays a key role as the first step in the biosynthesis of the thyroid hormones, of which iodine is an essential constituent. These hormones are crucial for the development of the central nervous system and the lungs in the fetus and the newborn and for intermediary metabolism at all ages. Since the cloning of NIS in 1996, NIS research has become a major field of inquiry, with considerable impact on many basic and translational areas. In this article, we review the most recent findings on NIS, I(-) homeostasis, and related topics and place them in historical context. Among many other issues, we discuss the current outlook on iodide deficiency disorders, the present stage of understanding of the structure/function properties of NIS, information gleaned from the characterization of I(-) transport deficiency-causing NIS mutations, insights derived from the newly reported crystal structures of prokaryotic transporters and 3-dimensional homology modeling, and the novel discovery that NIS transports different substrates with different stoichiometries. A review of NIS regulatory mechanisms is provided, including a newly discovered one involving a K(+) channel that is required for NIS function in the thyroid. We also cover current and potential clinical applications of NIS, such as its central role in the treatment of thyroid cancer, its promising use as a reporter gene in imaging and diagnostic procedures, and the latest studies on NIS gene transfer aimed at extending radioiodide treatment to extrathyroidal cancers, including those involving specially engineered NIS molecules.

BRAF genetic heterogeneity in papillary thyroid carcinoma and its metastasis

Intratumoral heterogeneity is widely recognized as an important determinant of a cancer's initial response and its subsequent resistance to targeted therapy. BRAF V600E mutation, common in papillary thyroid carcinoma (PTC), is helpful in fine needle aspiration diagnosis of thyroid nodules and is being evaluated for targeted therapies. This study was designed to assess the presence of BRAF mutation heterogeneity within primary PTCs and between paired primary and metastatic lesions. Genetic heterogeneity was evaluated in 47 PTCs (38 differentiated papillary thyroid carcinomas and 9 poorly differentiated PTCs with anaplastic areas). The differentiated papillary thyroid carcinomas included 16 cases with regional lymph node metastases at thyroidectomy and 9 cases with recurrent metastases to regional lymph nodes more than 5 years post thyroidectomy. Genetic heterogeneity of BRAF was studied by comparing the mutation status in different samples of tumor as follows: (a) 2 separate areas (each >1.5 cm in diameter) within the primary tumor, (b) a more than 1.5 cm area of primary carcinoma and a second 5 mm area simulating a fine needle aspiration sample from a different portion of the primary tumor, (c) primary carcinoma and its lymph node metastasis at thyroidectomy, (d) primary carcinoma and the recurrent metastasis, and (e) differentiated and anaplastic areas in the primary carcinoma. BRAF mutation status was concordant in 95.2% of the 62 paired samples. Discordant BRAF status was detected in only 4.8% of the pairs studied and most frequently involved cases with recurrent metastasis thus suggesting a need for additional testing of these lesions before instituting therapy.

Detectable thyroglobulin with negative imaging in differentiated thyroid cancer patients

In the absence of autoantibodies against thyroglobulin (Tg), Tg measurement nowadays is the cornerstone of clinical management of differentiated thyroid cancer patients. DTC patients presenting with a positive Tg measurement without an anatomical correlate on anatomic imaging provide a management challenge to the attending physician.

Based on the literature we will provide an overview of the most important steps to undertake in such patients and their potential clinical consequences.

[Targeted therapies, prognostic and predictive factors in endocrine oncology]

A better understanding of molecular mechanisms responsible for tumorigenesis has allowed the development of targeted drugs designed to improve the outcome of cancer. In endocrine tumors, several molecules have demonstrated efficacy in terms of progression free survival during phase III trials such as vandetanib and cabozantinib in medullary thyroid carcinoma, sorafenib in differentiated thyroid carcinoma and everolimus or sunitinib for pancreatic neuroendocrine tumors. Rare cancer network has allowed ongoing phase III trials in malignant pheochromocytoma and adrenocortical carcinoma. However, to date no specific predictive biomarker has yet been identified for a personalized cancer medicine. We review recent advances in endocrine oncology concerning molecular targets identification, targeted therapies and predictive or prognostic markers.

Switching from MAPK-dependent to MAPK-independent repression of the sodium-iodide symporter in 2D and 3D cultured normal thyroid cells

Loss of sodium-iodide symporter (NIS) expression in thyroid tumour cells primarily caused by constitutive MAPK pathway activation is often refractory to small molecule MAPK inhibitors. Suggested mechanisms are rebound MAPK signalling and activation of alternative signalling pathways. Here we provide evidence that failure to recover down-regulated NIS by MEK inhibition is not specific to tumour cells. NIS mRNA levels remained repressed in TSH-stimulated primary thyroid cells co-treated with epidermal growth factor (EGF) and pan-MEK inhibitor U0126 in the presence of 5% fetal bovine serum or, independently of serum, in 3D cultured thyroid follicles. This led to inhibited iodide transport and iodination. In contrast, U0126 restituted thyroglobulin synthesis in EGF-treated follicular cells. Serum potentiated TSH-stimulated NIS expression in 2D culture. U0126 blocked down-regulation of NIS only in serum-starved cells with a diminished TSH response. Together, this suggests that morphogenetic signals modify the expression of NIS and recovery response to MEK inhibition.

Abstract CN07-04: Maximizing the effectiveness of radioiodine therapy for metastatic thyroid cancer with selective inhibitors of MAPK signaling

Thyroid cancers are associated with mutually exclusive point mutations of BRAF (57%) and RAS (NRAS >HRAS; 12%), and fusion events activating BRAF, or the RTKs RET, NTRK1 or NTRK3. The molecular taxonomy of the disease is different in more advanced forms of thyroid cancer. Although BRAF mutations also predominate, poorly differentiated (PDTC) and anaplastic thyroid cancers (ATC) are relatively enriched for RAS mutations (23-44%). As predicted from the genetics of the disease, thyroid cancers, like melanomas, are ERK-driven tumors. However, they exhibit lineage-specific properties that offer distinct therapeutic opportunities and challenges. The 10-year survival of patients with metastatic thyroid cancers that retain radioiodine (RAI) avidity is ∼60%, whereas it is only 10% if the metastases are refractory to RAI therapy (1). There are several lines of evidence indicating that constitutive MAPK activity causes decreased radioiodine responsiveness. Conditional expression of oncogenic RET/PTC, RAS or BRAF in thyroid PCCL3 cells downregulates expression of the sodium iodide symporter (NIS) and other key genes required to organify and retain iodide (2, 3), which is restored by treatment with RAF or MEK inhibitors (2, 4). Mice with dox-inducible expression of BRAFV600E in thyroid cells develop invasive papillary thyroid cancers with profoundly impaired expression of genes required for iodine uptake and metabolism and of 124-iodine uptake in vivo, which are reversed when dox is discontinued, but only partially restored by RAF or MEK inhibitors (5). Based on these findings we performed a phase 2 trial of the MEK inhibitor selumetinib (AZD6244) in patients with RAI-refractory thyroid cancer. Selumetinib increased iodide incorporation at metastatic sites in 12/20 patients as determined by 124I PET scanning, and in ∼40% (8/20) the increase in uptake was sufficient to enable treatment with 131I, with remarkable clinical responses (6). Responses were greater in patients whose tumors harbored RAS as compared to BRAF mutations. An international multicenter phase 3 registration study of selumetinib vs placebo to increase remission rates of high risk thyroid cancer patients receiving post-surgical adjuvant radioiodine therapy is now in progress (the ASTRA trial).

There is concern that responses to monotherapy with MEK or RAF inhibitors may not be optimal, particularly in BRAF-mutant disease. We find that BRAF-mutant human thyroid cancer cell lines have decreased responsiveness to RAF and MEK inhibitors because of relief of negative feedback resulting in derepression of HER3 transcription, followed by neuregulin-1- induced HER3/HER2 signaling and reactivation of the MEK-ERK and PI3K-AKT pathways, which is overcome by co-treatment with HER kinase inhibitors (7). This mechanism of adaptive resistance differs in significant ways from the responses seen in BRAF-mutant melanoma and colorectal cell lines.

Our preclinical data predicts that optimal restoration of RAI responsiveness would be best achieved by compounds that inhibit MAPK output in a profound and sustained way. Indeed, recent experiments show that such strategies have excellent potential to further augment the specialized functions of thyroid cells, and lead to even more effective therapies.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):CN07-04.

Citation Format: James A. Fagin. Maximizing the effectiveness of radioiodine therapy for metastatic thyroid cancer with selective inhibitors of MAPK signaling. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr CN07-04.

Development of Magnetic Nanoparticles for Cancer Gene Therapy: A Comprehensive Review

Since they were first proposed as nonviral transfection agents for their gene-carrying capacity, magnetic nanoparticles have been studied thoroughly, both in vitro and in vivo. Great effort has been made to manufacture biocompatible magnetic nanoparticles for use in the theragnosis of cancer and other diseases. Here we survey recent advances in the study of magnetic nanoparticles, as well as the polymers and other coating layers currently available for gene therapy, their synthesis, and bioconjugation processes. In addition, we review several gene therapy models based on magnetic nanoparticles.

The sodium/iodide symporter: state of the art of its molecular characterization

The sodium/iodide symporter (NIS or SLC5A5) is an intrinsic membrane protein implicated in iodide uptake into thyroid follicular cells. It plays a crucial role in iodine metabolism and thyroid regulation and its function is widely exploited in the diagnosis and treatment of benign and malignant thyroid diseases. A great effort is currently being made to develop a NIS-based gene therapy also allowing the radiotreatment of nonthyroidal tumors. NIS is also expressed in other tissues, such as salivary gland, stomach and mammary gland during lactation, where its physiological role remains unclear. The molecular identity of the thyroid iodide transporter was elucidated approximately fifteen years ago. It belongs to the superfamily of sodium/solute symporters, SSS (and to the human transporter family, SLC5), and is composed of 13 transmembrane helices and 643 amino acid residues in humans. Knowledge concerning NIS structure/function relationship has been obtained by taking advantage of the high resolution structure of one member of the SSS family, the Vibrio parahaemolyticus sodium/galactose symporter (vSGLT), and from studies of gene mutations leading to congenital iodine transport defects (ITD). This review will summarize current knowledge regarding the molecular characterization of NIS.

Translational research in endocrine surgery

This article reviews translational research in endocrine surgery, with a focus on disorders of the thyroid, parathyroids, adrenals, and endocrine pancreas. Discovery of genes responsible for heritable endocrine cancer syndromes has increased knowledge of the causes and mechanisms of endocrine cancer and has refined surgical treatment options. Knowledge of mutations in sporadic cancer has led to rapid progress in small-molecule kinase inhibitor strategies. These breakthroughs and their influence on current therapy are discussed to provide surgeons with an overview of the basic science research currently creating new clinical treatments and improving patient care.

Detection and management of cervical lymph nodes in papillary thyroid cancer

Lymph node metastases in papillary thyroid cancer are a common occurrence; however, the management of clinically negative cervical lymph nodes remains controversial. Preoperative neck ultrasound mapping is crucial, and complete dissection of a nodal compartment is recommended for any metastatic lymph nodes. The role of prophylactic central neck dissection remains controversial. The BRAF V600E mutation is a common mutation in papillary thyroid cancer, and has been associated with more aggressive tumor behavior. Evaluating the BRAF status of tumors may have implications for treatment and surveillance. New areas of research continue to focus on risk stratification and identifying which patients benefit from a more aggressive treatment, such as prophylactic central lymphadenectomy and radioiodine ablation and more intense surveillance strategies.

Evolving approaches to patients with advanced differentiated thyroid cancer

Advanced differentiated thyroid cancer (DTC), defined by clinical characteristics including gross extrathyroidal invasion, distant metastases, radioiodine (RAI) resistance, and avidity for 18-fluorodeoxyglucose (positron emission tomography-positive), is found in approximately 10-20% of patients with DTC. Standard therapy (surgery, RAI, TSH suppression with levothyroxine) is ineffective for many of these patients, as is standard chemotherapy. Our understanding of the molecular mechanisms leading to DTC and the transformation to advanced DTC has rapidly evolved over the past 15-20 years. Newer targeted therapy, specifically inhibitors of intracellular kinase signaling pathways, and cooperative multicenter clinical trials have dramatically changed the therapeutic landscape for patients with advanced DTC. In this review focusing on morbidities, molecules, and medicinals, we present a patient with advanced DTC, explore the genetics and molecular biology of advanced DTC, and review evolving therapies for these patients including multikinase inhibitors, selective kinase inhibitors, and combination therapies.

Thyroid nodules and differentiated thyroid cancer: update on the Brazilian consensus

Thyroid nodules are frequent findings, especially when sensitive imaging methods are used. Although thyroid cancer is relatively rare, its incidence is increasing, particularly in terms of small tumors, which have an uncertain clinical relevance. Most patients with differentiated thyroid cancer exhibit satisfactory clinical outcomes when treatment is appropriate, and their mortality rate is similar to that of the overall population. However, relapse occurs in a considerable fraction of these patients, and some patients stop responding to conventional treatment and eventually die from their disease. Therefore, the challenge is how to identify the individuals who require more aggressive disease management while sparing the majority of patients from unnecessary treatments and procedures. We have updated the Brazilian Consensus that was published in 2007, emphasizing the diagnostic and therapeutic advances that the participants, representing several Brazilian university centers, consider most relevant in clinical practice. The formulation of the present guidelines was based on the participants' experience and a review of the relevant literature.

Clinical outcomes and molecular profile of differentiated thyroid cancers with radioiodine-avid distant metastases

BACKGROUND

Radioiodine (RAI) remains the mainstay of therapy for RAI-avid (RAIA) distant metastatic thyroid carcinoma. We previously demonstrated that RAI-refractory distant metastatic thyroid cancers commonly harbor BRAF mutations. However, the molecular profile of RAIA metastatic thyroid cancer is unknown. Here we describe the mutational profile of thyroid tumors from follicular cell-derived cancer (FCDTC) patients presenting with RAIA distant metastases. In addition, we aimed to correlate clinical outcomes of RAI therapy with clinicopathological factors and tumor mutational status.

METHODS

We retrospectively identified 43 patients with FCDTC who had RAI uptake in the lungs and/or bones on their initial ¹³¹I postablation scan. Primary tumors were genotyped for known mutations in thyroid cancer genes. Structural response to RAI was assessed 6-18 months after each administered RAI activity and at the end of follow-up.

RESULTS

RAS, BRAF, RET/PTC, and PIK3CA mutations were found in 42, 23, 10, and 2% of tumors, respectively, and the remaining 23% were wild type. None of these patients achieved cure after repeat RAI therapies, and most patients (54%) experienced disease progression despite repeated RAI administration. There was an increased prevalence of RAS mutations in these RAIA tumors. RAS-mutant cancers were more likely to concentrate iodine on diagnostic whole body scans. Despite this, structural response to RAI was not influenced by tumor genotype.

CONCLUSIONS

RAIA metastatic FCDTC are overrepresented with RAS mutations, whereas RAI refractory metastatic thyroid cancers are enriched with BRAF mutations. Despite a seemingly preserved ability to concentrate iodine, RAI therapy is ineffective in achieving cure in most patients with RAIA metastatic FCDTC, even in RAS-mutant disease. These poor outcomes may be improved based on recent evidence that pretreatment with MAPK kinase 1/2 inhibitors enhances responses to RAI, particularly in patients with RAS-mutant tumors.

MEK and the inhibitors: from bench to bedside

Four distinct MAP kinase signaling pathways involving 7 MEK enzymes have been identified. MEK1 and MEK2 are the prototype members of MEK family proteins. Several MEK inhibitors are in clinical trials. Trametinib is being evaluated by FDA for the treatment of metastatic melanoma with BRAF V600 mutation. Selumetinib has been studied in combination with docetaxel in phase II randomized trial in previously treated patients with advanced lung cancer. Selumetinib group had better response rate and progression-free survival. This review also summarized new MEK inhibitors in clinical development, including pimasertib, refametinib, PD-0325901, TAK733, MEK162 (ARRY 438162), RO5126766, WX-554, RO4987655 (CH4987655), GDC-0973 (XL518), and AZD8330.

Progress in molecular-based management of differentiated thyroid cancer

Substantial developments have occurred in the past 5-10 years in clinical translational research of thyroid cancer. Diagnostic molecular markers, such as RET-PTC, RAS, and BRAF(V600E) mutations; galectin 3; and a new gene expression classifier, are outstanding examples that have improved diagnosis of thyroid nodules. BRAF mutation is a prognostic genetic marker that has improved risk stratification and hence tailored management of patients with thyroid cancer, including those with conventionally low risks. Novel molecular-targeted treatments hold great promise for radioiodine-refractory and surgically inoperable thyroid cancers as shown in clinical trials; such treatments are likely to become a component of the standard treatment regimen for patients with thyroid cancer in the near future. These novel molecular-based management strategies for thyroid nodules and thyroid cancer are the most exciting developments in this unprecedented era of molecular thyroid-cancer medicine.

Current and Future Perspectives in Thyroid Carcinoma Treatment

Thyroid nodules are a common clinical problem and evaluation with neck and thyroid ultrasound and fine-needle aspiration biopsy are the most accurate methods for evaluating and identifying those that require surgical resection. The surgical treatment of differentiated thyroid carcinoma is the most common and recommended approach. Post-operative ¹³¹I remnant ablation is used to eliminate the post-surgical thyroid remnant and may facilitate the early detection of recurrence. The conclusion of two important recent studies is that the use of recombinant human thyrotropin and low ¹³¹I dose, 30 mCi, for post-operative ablation may be sufficient for the management of low-risk thyroid cancer. Recently, multi-targeted kinase inhibitors have emerged as promising treatments for metastatic differentiated thyroid cancers based on mutation detection in samples from thyroid cancer. Motesanib, sorafenib, vandetanib, sunitinib, lenvatinib, imatinib and cabozantinib are multi-kinase inhibitors that have the ability of inhibiting the rearranged during transection (RET) and vascular endothelial growth factor receptor (VEGFR), and other kinases, and have been used in advanced differentiated thyroid carcinoma. By contrast, axitinib and pazopanib seem to act only as anti-angiogenic agents. Anaplastic thyroid carinoma is often advanced and metastatic at diagnosis. Patients with localised disease not amenable to surgical resection can be treated with adjuvant chemoradiotherapy.