A mutation in the RET proto-oncogene associated with multiple endocrine neoplasia type 2B and sporadic medullary thyroid carcinoma

PPemd26, an anthraquinone derivative, suppresses angiogenesis via inhibiting VEGFR2 signalling

BACKGROUND AND PURPOSE

Angiogenesis contributes to coronary heart disease, immune disorders and numerous malignancies. VEGF-A and its receptors (VEGFRs) play a pivotal role in regulating angiogenesis. In an effort to discover more effective inhibitors of tumour angiogenesis, we have analysed the actions of a novel anthraquinone derivative, PPemd26, and explored its anti-angiogenic mechanisms.

EXPERIMENTAL APPROACH

The effects of PPemd26 were evaluated in vitro using HUVEC cultures to assess proliferation, migration, invasion and tube formation. Immunoblotting was used to analyse phosphorylation of signalling kinases. Effects in vivo were assayed using Matrigel plug and xenograft mouse models.

KEY RESULTS

PPemd26 significantly inhibited VEGF-A-induced proliferation, migration, invasion and tube formation of HUVECs. PPemd26 also attenuated VEGF-A-induced microvessel sprouting from rat aortic rings ex vivo and suppressed formation of new blood vessels in implanted Matrigel plugs in models of angiogenesis in vivo. In addition, PPemd26 inhibited VEGF-A-induced phosphorylation of VEGFR2 and its downstream protein kinases including Akt, focal adhesion kinase, ERK and Src. Furthermore, systemic administration of PPemd26 suppressed the growth of s.c. xenografts of human colon carcinoma in vivo. Histochemical analysis of the xenografts revealed a marked reduction in stainingfor the vascular marker CD31 and proliferation marker Ki-67.

CONCLUSIONS AND IMPLICATIONS

This study provides evidence that PPemd26 suppressed tumour angiogenesis through inhibiting VEGFR2 signalling pathways, suggesting that PPemd26 is a potential drug candidate for developing anti-angiogenic agents for the treatment of cancer and angiogenesis-related diseases.

Multiple Endocrine Neoplasia: Genetics and Clinical Management

Early diagnosis of multiple endocrine neoplasia (MEN) syndromes is critical for optimal clinical outcomes; before the MEN syndromes can be diagnosed, they must be suspected. Genetic testing for germline alterations in both the MEN type 1 (MEN1) gene and RET proto-oncogene is crucial to identifying those at risk in affected kindreds and directing timely surveillance and surgical therapy to those at greatest risk of potentially life-threatening neoplasia. Pancreatic, thymic, and bronchial neuroendocrine tumors are the leading cause of death in patients with MEN1 and should be aggressively considered by at least biannual computed tomography imaging.

Endocrine tumours: progressive metastatic medullary thyroid carcinoma: first- and second-line strategies

The treatment for metastasised medullary thyroid cancer is still a topic of discussion. One of the main challenges remains to find effective adjuvant and palliative options for patients with metastatic disease. The diagnostic and treatment strategies for this tumour are discussed and possible new developments commented. Approaches that target rearranged during transfection (RET) are preferable to those that target RET downstream proteins as, theoretically, blocking RET downstream targets will block only one of the many pathways activated by RET. Combining several agents would seem to be more promising, in particular agents that target RET with those that independently target RET signalling pathways or the more general mechanism of tumour progression.

Molecular pathology of hereditary and sporadic medullary thyroid carcinomas

OBJECTIVES

Medullary thyroid carcinoma (MTC) is a relatively uncommon type of thyroid malignancy, with unique histologic features and molecular pathology. It is important to recognize, because its management, which is in part driven by the genetic basis of this disease, is different from follicular-derived thyroid tumors. The aim of this article is to briefly review the histopathologic features of MTC and then explore its molecular pathology, including the role of molecular diagnostic testing and the use of targeted therapy for advanced disease.

METHODS

A review of published literature was performed.

RESULTS

A subset of MTC cases is hereditary and due to germline mutations in the RET tyrosine kinase receptor gene. Somatic mutations in either RET or RAS are also present in most sporadic tumors.

CONCLUSIONS

Molecular genetic testing is routinely performed to identify hereditary cases. In addition, understanding the molecular basis of both hereditary and sporadic MTC has led to the development of targeted therapy with tyrosine kinase inhibitors. Although additional data are needed, tumor mutation status may affect response to targeted therapy. Therefore, it is possible that genetic testing of tumor tissue to predict treatment response, as is currently done for other cancer types, may come into practice in the future.

Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma

INTRODUCTION

The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association.

METHODS

The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document.

RESULTS

The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC.

CONCLUSIONS

The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice.

Carcinoembryonic antigen-related cell adhesion molecule 4 (CEACAM4) is specifically expressed in medullary thyroid carcinoma cells

Carcinoembryonic antigen (CEA), an oncofetal cell surface glycoprotein, has been widely used as a human tumor marker due to its high expression in tumors and secretion to serum. It belongs to the immunoglobulin superfamily named CEA-related cell adhesion molecule (CEACAM) family. Members of this family are detected in various cancers and have been shown to be involved in cancer growth and invasion. In this study, we examined the mRNA expression profiles of CEACAM family members including CEACAM1, CEACAM3, CEACAM4, CEACAM5 (CEA), CEACAM6, CEACAM7, and CEACAM8 in various tumor cell lines. Our screening data indicated that the mRNA expression patterns of CEACAMs in TT cells, which are derived from medullary thyroid carcinoma (MTC), were distinct from other tumor cell lines. Additionally, CEACAM4 was only expressed in TT cells, in which two novel splice variants of CEACAM4 were expressed. These findings suggested that production of CEA and CEA-related molecules in MTC may be distinct from other tumor-based production of those molecules and that the specific expression of CEACAM4 would make possible to differentiate between MTC and other CEA-producing tumors.

Histopathology of C Cells and Medullary Thyroid Carcinoma

The human thyroid gland contains less than 0.01-0.1% calcitonin producing and secreting C cells, which in men are almost exclusively situated in an intrafollicular location; the vast majority of C cells are embryologically derived of remnants of the ultimobranchial body and ultimately of the neural crest, a small subset, however, is presumed to originate from endodermal stem cells. Thyroid tumours with C cell differentiation have been named medullary thyroid carcinoma (MTC); calcitonin is also produced and secreted by MTC which makes this peptide hormone a very useful serum marker both for early detection and clinical follow-up of patients with MTC. About 70-80% of MTC are sporadic tumours, whereas 20-30% are familial MTC which are autosomal-dominant inherited and caused by germline mutations of the RET proto-oncogene located on chromosome 10. This article summarizes the histological, immunhistochemical and molecular genetic features of C cells, C-cell hyperplasia (CCH) and MTC, emphasizing the role of diagnostic pathology.

Thyroid C-Cell Biology and Oncogenic Transformation

The thyroid parafollicular cell, or commonly named "C-cell," functions in serum calcium homeostasis. Elevations in serum calcium trigger release of calcitonin from the C-cell, which in turn functions to inhibit absorption of calcium by the intestine, resorption of bone by the osteoclast, and reabsorption of calcium by renal tubular cells. Oncogenic transformation of the thyroid C-cell is thought to progress through a hyperplastic process prior to malignancy with increasing levels of serum calcitonin serving as a biomarker for tumor burden. The discovery that multiple endocrine neoplasia type 2 is caused by activating mutations of the RET gene serves to highlight the RET-RAS-MAPK signaling pathway in both initiation and progression of medullary thyroid carcinoma (MTC). Thyroid C-cells are known to express RET at high levels relative to most cell types; therefore, aberrant activation of this receptor is targeted primarily to the C-cell, providing one possible cause of tissue-specific oncogenesis. The role of RET signaling in normal C-cell function is unknown though calcitonin gene transcription appears to be sensitive to RET activation. Beyond RET, the modeling of oncogenesis in animals and screening of human tumors for candidate gene mutations have uncovered mutation of RAS family members and inactivation of Rb1 regulatory pathway as potential mediators of C-cell transformation. A growing understanding of how RET interacts with these pathways, both in normal C-cell function and during oncogenic transformation, will help in the development of novel molecular-targeted therapies.

Identification of two novel RET kinase inhibitors through MCR-based drug discovery: design, synthesis and evaluation

From an MCR fragment library, two novel chemical series have been developed as inhibitors of RET, which is a kinase involved in the pathology of medullary thyroid cancer (MTC). Structure activity relationship studies (SAR) identified two sub-micromolar tractable leads, 6g and 13g. 6g was confirmed to be a Type-II RET inhibitor. 13g and 6g inhibited RET in cells transformed by RET/C634. A RET DFG-out homology model was established and utilized to predict Type-II inhibitor binding modes.

Role of preoperative basal calcitonin levels in the timing of prophylactic thyroidectomy in patients with germline RET mutations

BACKGROUND

The American Thyroid Association (ATA) published recommendations for the timing of prophylactic surgery for medullary thyroid carcinoma based on the specific mutation, patient age, family history, and serum calcitonin levels. The aim of this study was to assess the role of preoperative basal calcitonin (prebCt) levels in predicting the presence of medullary carcinoma of the thyroid in patients with RET mutations.

METHODS

We conducted a retrospective study in two endocrine surgery departments. Between 1986 and 2012, a total of 32 patients with RET mutations underwent prophylactic thyroidectomy. The patients were stratified into four ATA risk levels: A, B, C, and D.

RESULTS

All of the patients were biologically cured. Microcarcinoma was observed in the final pathology report for four of the 20 patients with normal prebCt (25 %) and for nine of the 12 patients with elevated prebCt (75 %). In the level A group, four patients with normal prebCt and one patient with elevated prebCt presented with microcarcinoma. In the level C group, one patient with normal prebCt and six of the seven patients with elevated prebCt (86 %) presented with microcarcinoma.

CONCLUSIONS

PrebCt can predict the presence of microcarcinoma according to surgical pathological analysis. Patients with microcarcinoma can be biochemically and clinically cured using prophylactic thyroidectomy.

Upregulation of the PI3K/Akt pathway in the tumorigenesis of canine thyroid carcinoma

BACKGROUND

Information on the genetic events leading to thyroid cancer in dogs is lacking.

HYPOTHESIS/OBJECTIVES

Upregulation of the PI3K/Akt pathway has an important role in the tumorigenesis of thyroid carcinoma in dogs.

ANIMALS

Fifty-nine dogs with thyroid carcinoma and 10 healthy controls.

METHODS

Quantitative RT-PCR was performed for VEGFR-1, VEGFR-2, EGFR, PIK3CA, PIK3CB, PDPK1, PTEN, AKT1, AKT2, COX-2, and CALCA. Mutation analysis was performed for known hotspots of RAS (N, K, H), PIK3CA, BRAF, RET, and for the entire coding region of PTEN.

RESULTS

Forty-three dogs (73%) had follicular cell thyroid carcinoma (FTC) and 16 dogs (27%) had medullary thyroid carcinoma (MTC). The relative mRNA expressions of VEGFR-1 (P < .001), VEGFR-2 (P = .002), PDPK1 (P < .001), AKT1 (P = .009), and AKT2 (P < .001) were increased in FTC, and those of EGFR (P < .001), VEGFR-1 (P = .036), and PIK3CA (P = .019) were increased in MTC when compared to normal thyroid glands. Mutation analysis of K-RAS identified 2 activating missense mutations, which also have been described in thyroid cancer of humans. A G12R substitution was present in 1 FTC and an E63K substitution was present in 1 MTC. No functional mutations were found in the sequenced regions of H-RAS, N-RAS, PIK3CA, BRAF, RET, and PTEN.

CONCLUSIONS AND CLINICAL IMPORTANCE

The increased expression of several genes associated with PI3K/Akt signaling suggests the involvement of this pathway in the pathogenesis of thyroid carcinoma in dogs, warranting further research on pathway activation and gene amplification. The mutations most frequently associated with thyroid cancer in humans are rare in dogs.

Overview and management of dermatologic events associated with targeted therapies for medullary thyroid cancer

BACKGROUND

Treatment options for patients with advanced or metastatic medullary thyroid cancer (MTC) have, in recent years, expanded with the approval of two tyrosine kinase inhibitors (TKIs): vandetanib and cabozantinib. Other agents, including TKIs, are under clinical investigation for MTC. Although patients treated with TKIs are at risk of developing dermatologic adverse events (AE), these untoward events may be mitigated through AE-driven algorithms.

SUMMARY

AE-driven algorithms combine effective nonpharmaceutical and pharmaceutical treatment modalities implemented by a multidisciplinary effort that incorporates nursing interventions, patient education, and referrals to pain-management specialists, podiatrists, and dermatologists, as appropriate. Effective AE prevention and management reduce the need for dose interruptions and modifications, allowing patients the opportunity to derive the maximal benefit from TKI therapy, while maintaining quality of life.

CONCLUSIONS

Optimal use of targeted therapies in the treatment of MTC depends on careful patient selection, interdisciplinary communication, and patient education and encouragement to enhance compliance and safety, optimize consistent dosing, and maximize the use of effective therapies.

A phase I study of imatinib, dacarbazine, and capecitabine in advanced endocrine cancers

Background

Patients with advanced endocrine cancers, such as adrenocortical carcinoma and medullary thyroid carcinoma, have few well-validated therapeutic options. Pre-clinical studies have suggested potential activity of imatinib in these tumors. We therefore sought to establish a safe, novel treatment regimen combining imatinib with cytotoxic chemotherapy for future study in endocrine cancers.

Methods

A standard 3 + 3 dose-escalation design was used with a 21-day cycle, including imatinib on days 1–21, dacarbazine on days 1–3, and capecitabine on days 1–14.

Results

Twenty patients were treated. The most frequent toxicities were edema and fatigue, with dose-limiting fatigue and dyspnea. The recommended phase II regimen is dacarbazine 250 mg/m2 daily on day 1–3, capecitabine 500 mg/m2 twice daily on days 1–14, and imatinib 300 mg daily on days 1–21 of a 21-day cycle. Interestingly, responses were seen in patients with adrenocortical carcinoma, with 1 of 6 patients experiencing a partial response and a second experiencing a minor response, with progression-free survival of 8.8 and 6.4 months, respectively.

Conclusions

The regimen of imatinib, dacarbazine, and capecitabine is well-tolerated. It may have some activity in adrenocortical carcinoma, and further study of this combination or its components may be beneficial for this disease with limited treatment options.

Trial registration

ClinicalTrials.gov identifier NCT00354523, registered July 18, 2006.

VEGF, VEGFR3, and PDGFRB protein expression is influenced by RAS mutations in medullary thyroid carcinoma

BACKGROUND

Tyrosine kinase inhibitors (TKIs) have achieved remarkable clinical results in medullary thyroid carcinoma (MTC) patients. However, the considerable variability in patient response to treatment with TKIs remains largely unexplained. There is evidence that it could be due, at least in part, to alterations in genes associated with the disease via their effect on the expression of TKI targets. The objective of this study was to evaluate the influence of RAS mutations on the expression levels in MTC tumors of eight key TKI target proteins.

METHODS

We assessed by immunohistochemistry the expression of EGFR, KIT, MET, PDGFRB, VEGF, VEGFR1, VEGFR2, and VEGFR3 in a series of 84 primary MTC tumors that had previously been molecularly characterized, including 14 RAS-positive, 18 RET(M918T)-positive, and 24 RET(C634)-positive tumors, as well as 15 wild-type tumors with no mutations in the RET or RAS genes.

RESULTS

In contrast to RET-positive tumors, RAS-positive tumors expressed neither PDGFRB nor MET (p=0.0060 and 0.047, respectively). Similarly, fewer RAS-positive than RET-related tumors expressed VEGFR3 (p=0.00062). Finally, wild-type tumors expressed VEGF more often than both RAS- and RET-positive tumors (p=0.0082 and 0.011, respectively).

CONCLUSIONS

This is the first study identifying that the expression of TKI targets differs according to the presence of RAS mutations in MTC. This information could potentially be used to select the most beneficial TKI treatment for these patients.

An update on clinical trials of targeted therapies in thyroid cancer

PURPOSE OF REVIEW

Several new targeted therapies with multikinase inhibitors targeting vascular endothelial growth factor (VEGF), rearranged during transfection and v-raf murine sarcoma viral oncogene homolog B1 pathways have been tested in clinical trials for radioiodine-refractory differentiated thyroid cancer (DTC) and medullary thyroid cancer (MTC) in the past 10 years.

RECENT FINDINGS

Results of the first phase III trial of VEGF-targeted therapy (sorafenib) in DTC were presented in June 2013, and two phase III trials with VEGF and rearranged during transfection-targeted therapies (vandetanib and cabozantinib) in MTC have led to approval by US Food and Drug Administration in the past 2 years. Whereas such therapies increase median progression-free survival compared to placebo, there is no therapy proven to improve overall survival yet. Significant potential adverse event risks associated with such therapies need to be recognized. Dissemination of knowledge about targeted therapies is critical for various medical specialists as patient care for thyroid cancers is best delivered in a multidisciplinary setting.

SUMMARY

Successful development of targeted systemic therapies in DTC and MTC in the past 5 years is incredibly exciting in the field and patients with advanced DTC/MTC now have new standard-of-care therapy options.

Prevalence by age and predictors of medullary thyroid cancer in patients with lower risk germline RET proto-oncogene mutations

BACKGROUND

Age-related risk of medullary thyroid carcinoma (MTC) development in presymptomatic carriers of lower risk germline RET mutations is uncertain; such data may aid counseling patients regarding timing of thyroidectomy.

METHODS

From an institutional database and an exhaustive literature review, we identified 679 patients with American Thyroid Association (ATA) level A or B mutations who were identified because of family screening (index cases of MTC were excluded to minimize selection bias). We evaluated age at thyroidectomy or last evaluation if no thyroidectomy, preoperative calcitonin level (elevated or not), the mutated codon, and outcome (MTC vs. no MTC after thyroidectomy or no clinical evidence of MTC if thyroid intact). Data were used to estimate the cumulative prevalence of MTC and/or assess likelihood of MTC stratified by codon. After exclusion of cases with missing data or small representation, 503 patients with mutations in codons 533, 609, 611, 618, 620, 791, and 804 were analyzed.

RESULTS

236 patients had MTC. Cumulative prevalence and median time to MTC varied by codon and within ATA risk levels (p<0.0001). Patients with a codon 620 mutation were 2.8-6.9 times more likely to have MTC than other level B mutation carriers, and 5.1-21.7 times more likely than level A mutation carriers included in our focus population. The youngest median time to MTC was 19 years for codon 620 and the oldest was 56 years for codon 611. Cumulative prevalence of MTC by age 20 was 10% or lower for codons 533, 609, 611, 791, and 804. By age 50, it ranged from 18% for codon 791 to 95% for codon 620. An elevated preoperative calcitonin level strongly predicted MTC on final pathology, though false-negative rates varied by codon (p<0.0001). Positive predictive values ranged from 76% to 100% by codon with an overall positive predictive value of 87% across codons.

CONCLUSIONS

This study offers a better understanding of the age-related development of MTC in lower risk RET mutation carriers, provides evidence of further distinctions between lower risk mutations within ATA subgroups, and clarifies the clinical significance of codon 791 mutations. The data support individualized "codon-based" management approaches coupled with clinical data such as calcitonin levels.

Medical management of metastatic medullary thyroid cancer

Medullary thyroid cancer (MTC) is an aggressive form of thyroid cancer that occurs in both heritable and sporadic forms. Discovery that mutations in the rearranged during transfection (RET) proto-oncogene predispose to familial cases of this disease has allowed for presymptomatic identification of gene carriers and prophylactic surgery to improve the prognosis of these patients. A significant number of patients with the sporadic type of MTC and even those with familial disease still present with lymph node or distant metastases, making surgical cure difficult. Over the past several decades, many different types of therapy for metastatic disease have been attempted with limited success. Improved understanding of the molecular defects and pathways involved in both familial and sporadic MTC has resulted in new hope for these patients with the development of drugs targeting the specific alterations responsible. This new era of targeted therapy with kinase inhibitors represents a significant step forward from previous trials of chemotherapy, radiotherapy, and hormone therapy. Although much progress has been made, additional agents and strategies are needed to achieve durable, long-term responses in patients with metastatic MTC. This article reviews the history and results of medical management for metastatic MTC from the early 1970s up until the present day.

An extended family with familial medullary thyroid carcinoma and Hirschsprung's disease

Familial medullary thyroid carcinoma (FMTC) is an autosomal dominant inherited disease that has highly characteristic clinical features, including medullary thyroid carcinoma (MTC). Mutation of the RET proto-oncogene is known to be responsible for development of FMTC and for multiple endocrine neoplasia types 2A and 2B. Hirschsprung's disease is the most common form of structural intestinal obstructive disease in human newborns. Hirschsprung's disease is defined by the absence of neural crest-derived enteric ganglia along a variable length of the bowel that invariably involves the rectoanal junction. Co-segregation of FMTC and Hirschsprung's disease is uncommon; nevertheless, in 3 generations of 1 family, we observed 5 patients with FMTC, 2 patients with Hirschsprung's disease, and 1 patient with characteristics of both FMTC and Hirschsprung's disease. Moreover, a Cys620Ser mutation in RET was identified in 4 of the 8 patients. This mutation had both activating and inactivating effects on the RET (REarranged during Transfection) protein. There were individual differences in the penetrance of Hirschsprung's disease due to the RET mutation, but the penetrance of MTC was uniform and high. Genetic testing is important for making decisions about treatment and follow-up in families of this kind.

Molecular pathways and therapeutic targets in lung cancer

Lung cancer is still the leading cause of cancer death worldwide. Both histologically and molecularly lung cancer is heterogeneous. This review summarizes the current knowledge of the pathways involved in the various types of lung cancer with an emphasis on the clinical implications of the increasing number of actionable molecular targets. It describes the major pathways and molecular alterations implicated in the development and progression of non-small cell lung cancer (adenocarcinoma and squamous cancer), and of small cell carcinoma, emphasizing the molecular alterations comprising the specific blueprints in each group. The approved and investigational targeted therapies as well as the immune therapies, and clinical trials exploring the variety of targeted approaches to treatment of lung cancer are the main focus of this review.

RET revisited: expanding the oncogenic portfolio

The RET receptor tyrosine kinase is crucial for normal development but also contributes to pathologies that reflect both the loss and the gain of RET function. Activation of RET occurs via oncogenic mutations in familial and sporadic cancers - most notably, those of the thyroid and the lung. RET has also recently been implicated in the progression of breast and pancreatic tumours, among others, which makes it an attractive target for small-molecule kinase inhibitors as therapeutics. However, the complex roles of RET in homeostasis and survival of neural lineages and in tumour-associated inflammation might also suggest potential long-term pitfalls of broadly targeting RET.

Treating medullary thyroid cancer in the age of targeted therapy

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor deriving from the thyroid parafollicular cell. Thyroidectomy continues to serve as the primary initial treatment for this cancer. Because standard cytotoxic chemotherapy has proven ineffective, reoperation and external beam radiation therapy had been the only tools to treat recurrences or distant disease. The discovery that aberrant activation of RET, a receptor tyrosine kinase, is a primary driver of MTC tumorigenesis led to clinical trials using RET-targeting tyrosine kinase inhibitors. The successes of those trials led to the approval of vandetanib and cabozantinib for treating patients with progressive or symptomatic MTC. The availability of these drugs, along with additional targeted therapies in development, requires a thoughtful reconsideration of the approach to treating patients with unresectable locally advanced and/or metastatic progressive MTC.

A MEN2A family with two asymptomatic carriers affected by unilateral renal agenesis

Accumulating evidences suggest RET gene's involvement in development of the kidney in mice and humans. Although it is well known that RET mutation causes multiple endocrine neoplasia type 2A (MEN2A), thus far only 3 individuals have been reported to have MEN2A and renal agenesis/dysgenesis. We report a MEN2A family with RET mutation in which two asymptomatic carriers presented with unilateral renal agenesis. A 48-year-old woman underwent total thyroidectomy with regional lymph node dissection in our department for medullary thyroid carcinoma. She had earlier surgical treatment for a left adrenal pheochromocytoma at the age of 45. In the screening for MEN type 2 for her three sons, a CT scan for adrenal pheochromocytoma incidentally found unilateral renal agenesis in two of the sons, one of whom had suffered from Hirschsprung's disease (HSCR). They had contralateral kidneys exhibiting compensatory hypertrophy and normal renal function. Genetic analysis detected C618R RET mutation in the proband and her 3 sons, and no other mutations were found in RET as well as glial cell line-derived neurotrophic factor (GDNF). Our data lend support to the hypothesis that constitutive active RET mutation in MEN type 2 might partially impair RET function and thereby cause loss of function phenotype such as renal agenesis or HSCR.

The value of genetic screening in medullary thyroid cancer

Medullary thyroid cancer (MTC) accounts for ~10% of thyroid carcinomas and occurs in sporadic and hereditary forms. Early diagnosis significantly impacts the clinical course, management and outcome of the disease. The identification of germline-activating mutations of the rearranged during transfection oncogene in patients with hereditary MTC led to significant progress in the diagnostic and therapeutic approach, thus improving the quality of care provided, and consequently, disease prognosis. In the present review, various aspects of genetic screening (GS) in MTC will be covered, which elucidate the value of GS in guiding clinical decision making, therapy selection and appropriate genetic counseling of the affected families. GS should be offered to every MTC patient, based on the personal and family medical history, to allow optimal clinical management and follow-up.

In silico profiling and structural insights of missense mutations in RET protein kinase domain by molecular dynamics and docking approach

A major challenge remaining in drug design efforts towards protein kinase is due to the development of drug resistance initiated by the missense mutations in the kinase catalytic domain. Gain or loss of function mutations in the REarranged during Transfection (RET) tyrosine kinase gene have been associated with the development of a wide range of human associated cancers and Hirschsprung's disease. However, to what extent these mutations might affect bio-molecular functions remains unclear. In this article, the functionally significant mutations in RET were screened with the aid of various sequence and structure based in silico prediction methods. We mapped the deleterious mutants, modelled mutant proteins and deciphered the impact of mutations on drug binding mechanisms in the RET crystal structure of PDB ID: with the potential inhibitor vandetanib by docking analysis. Furthermore, molecular dynamics simulations were undertaken to understand the mechanistic action of cancer associated mutations in altering the protein kinase structure, dynamics, and stability. According to our results, the overall effect of V804M, M918T and S922Y were destabilizing and mostly alter the electrostatic component of the binding energy. Specifically, the mutation of gatekeeper residue valine 804 present in the ATP binding pocket affects the protein stability and confers resistance to the drug vandetanib, which was consistent with previously published experimental results. Overall, our findings may provide useful structural insights for in-depth understanding of the molecular mechanism underlying RET mutation and developing effective drugs.

A miRNA signature associated with human metastatic medullary thyroid carcinoma

MicroRNAs (miRNAs) represent a class of small, non-coding RNAs that control gene expression by targeting mRNA and triggering either translational repression or RNA degradation. The objective of our study was to evaluate the involvement of miRNAs in human medullary thyroid carcinoma (MTC) and to identify the markers of metastatic cells and aggressive tumour behaviour. Using matched primary and metastatic tumour samples, we identified a subset of miRNAs aberrantly regulated in metastatic MTC. Deregulated miRNAs were confirmed by quantitative real-time PCR and validated by in situ hybridisation on a large independent set of primary and metastatic MTC samples. Our results uncovered ten miRNAs that were significantly expressed and deregulated in metastatic tumours: miR-10a, miR-200b/-200c, miR-7 and miR-29c were down-regulated and miR-130a, miR-138, miR-193a-3p, miR-373 and miR-498 were up-regulated. Bioinformatic approaches revealed potential miRNA targets and signals involved in metastatic MTC pathways. Migration, proliferation and invasion assays were performed in cell lines treated with miR-200 antagomirs to ascertain a direct role for this miRNA in MTC tumourigenesis. We show that the members of miR-200 family regulate the expression of E-cadherin by directly targeting ZEB1 and ZEB2 mRNA and through the enhanced expression of tumour growth factor β (TGFβ)-2 and TGFβ-1. Overall, the treated cells shifted to a mesenchymal phenotype, thereby acquiring an aggressive phenotype with increased motility and invasion. Our data identify a robust miRNA signature associated with metastatic MTC and distinct biological processes, e.g., TGFβ signalling pathway, providing new potential insights into the mechanisms of MTC metastasis.

Fine needle aspiration and medullary thyroid carcinoma: the risk of inadequate preoperative evaluation and initial surgery when relying upon FNAB cytology alone

OBJECTIVES

To evaluate the diagnostic accuracy of fine-needle aspiration biopsy (FNAB) to preoperatively diagnose medullary thyroid cancer (MTC) among multiple international centers and evaluate how the cytological diagnosis alone could impact patient management.

METHODS

We performed a retrospective chart review of sporadic MTC (sMTC) patients from 12 institutions over the last 29 years. FNAB cytology results were compared to final pathologic diagnoses to calculate FNAB sensitivity. To evaluate the impact of cytology sensitivity for MTC according to current practice and to avoid confounding results by local treatment protocols, changes in treatment patterns over time, and the influence of ancillary findings (e.g., serum calcitonin), therapeutic interventions based on FNAB cytology alone were projected into 1 of 4 treatment categories: total thyroidectomy (TT) and central neck dissection (CND), TT without CND, diagnostic hemithyroidectomy, or observation.

RESULTS

A total of 313 patients from 4 continents and 7 countries were included, 245 of whom underwent FNAB. FNAB cytology revealed MTC in 43.7% and possible MTC in an additional 2.4%. A total of 113 (46.1%) patients with surgical pathology revealing sMTC had FNAB findings that supported TT with CND, while 37 (15.1%) supported TT alone. In the remaining cases, diagnostic hemithyroidectomy and observation were projected in 32.7% and 6.1%, respectively.

CONCLUSION

FNAB is an important diagnostic tool in the evaluation of thyroid nodules, but the low sensitivity of cytological evaluation alone in sMTC limits its ability to command an optimal preoperative evaluation and initial surgery in over half of affected patients.

Yamada S, Miyamoto S, Yamada S, Son JH, Nishido H, Ide F, Nagashima H, Sugaya M, Hirohata T, Mizutani A, Okinaga H, Ishii Y, Tahara S, Teramoto A, Osamura RY, Yamazaki K, Ishida Y. Clinicopathological and molecular histochemical review of skull base metastasis from differentiated thyroid carcinoma

Skull base metastasis from differentiated thyroid carcinoma including follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) is a rare clinical entity. Eighteen FTC cases and 10 PTC cases showing skull base metastasis have been reported. The most common symptom of skull base metastasis from FTC and PTC is cranial nerve dysfunction. Bone destruction and local invasion to the surrounding soft tissues are common on radiological imaging. Skull base metastases can be the initial clinical presentation of FTC and PTC in the presence of silent primary sites. The possibility of skull base metastasis from FTC and PTC should be considered in patients with the clinical symptoms of cranial nerve dysfunction and radiological findings of bone destruction. A variety of genetic alterations in thyroid tumors have been identified to have a fundamental role in their tumorigenesis. Molecular histochemical studies are useful for elucidating the histopathological features of thyroid carcinoma. Recent molecular findings may provide novel molecular-based treatment strategies for thyroid carcinoma.

Current understanding and management of medullary thyroid cancer

Medullary thyroid cancer (MTC) typically accounts for 3%-4% of all thyroid cancers. Although the majority of MTCs are sporadic, 20% of cases are hereditary. Hereditary MTC can be found in multiple endocrine neoplasia 2A or 2B or as part of familial MTC based on a specific germline mutation in the RET proto-oncogene. This article discusses the current approaches available for the diagnosis, evaluation, and management of patients and their family members with suspected MTC. The disease is predominantly managed surgically and typically requires a total thyroidectomy and lymph node dissection. A review of recent guidelines on the extent and timing of surgical excision is discussed. There are not very many effective systemic treatment options for MTC, but several emerging therapeutic targets have promise.

Hypoxia-inducible factor signaling in pheochromocytoma: turning the rudder in the right direction

Many solid tumors, including pheochromocytoma (PHEO) and paraganglioma (PGL), are characterized by a (pseudo)hypoxic signature. (Pseudo)hypoxia has been shown to promote both tumor progression and resistance to therapy. The major mediators of the transcriptional hypoxic response are hypoxia-inducible factors (HIFs). High levels of HIFs lead to transcription of hypoxia-responsive genes, which are involved in tumorigenesis. PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. In recent years, substantial progress has been made in understanding the metabolic disturbances present in PHEO and PGL, especially because of the identification of some disease-susceptibility genes. To date, fifteen PHEO and PGL susceptibility genes have been identified. Based on the main transcription signatures of the mutated genes, PHEOs and PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Although these two clusters seem to show distinct signaling pathways, recent data suggest that both clusters are interconnected by HIF signaling as the important driver in their tumorigenesis, and mutations in most PHEO and PGL susceptibility genes seem to affect HIF-α regulation and its downstream signaling pathways. HIF signaling appears to play an important role in the development and growth of PHEOs and PGLs, which could suggest new therapeutic approaches for the treatment of these tumors.

Thyroid cancer and co-occurring RET mutations in Hirschsprung disease

The objective of this study was to assess the occurrence of thyroid cancer and co-occurring RET mutations in a population-based cohort of adult Hirschsprung disease (HD) patients. All 156 patients operated for HD in a tertiary center during 1950-1986 were followed for thyroid malignancies up to 2010 through the nationwide Finnish Cancer Registry. Ninety-one individuals participated in clinical and genetic screening, which included serum calcitonin and thyroid ultrasound (US) with cytology. Exons 10, 11, 13, and 16 were sequenced in all, and all exons of RET in 43 of the subjects, including those with thyroid cancer, RET mutations, suspicious clinical findings, and familial or long-segment disease. Through the cancer registry, two cases (aged 35 and 37 years) of medullary thyroid cancer (MTC) were observed; the incidence for MTC was 340-fold (95% CI 52-1600) compared with average population. These individuals had C611R and C620R mutations in exon 10. One papillary thyroid cancer without RET mutations was detected by clinical screening. Four subjects (aged 31-50 years) with co-occurring RET mutations in exons 10 (C609R; n=1) and 13 (Y791F, n=3) had sporadic short-segment HD with normal thyroid US and serum calcitonin. Three novel mutations and five single-nucleotide polymorphisms were found outside exons 10 and 13 without associated signs of thyroid cancer. MTC-associated RET mutations were restricted to exons 10 and 13 affecting ∼5% of unselected adults with HD. Clinical thyroid assessment did not improve accuracy of genetic screening, which should not be limited to patients with familial or long-segment disease.

Multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma: an update

CONTEXT

Over the last decade, our knowledge of the multiple endocrine neoplasia (MEN) type 2 syndromes MEN2A and MEN2B and familial medullary thyroid carcinoma (FMTC) has expanded greatly. In this manuscript, we summarize how recent discoveries have enhanced our understanding of the molecular basis of these diseases and led to improvements in the diagnosis and management of affected patients.

EVIDENCE ACQUISITION

We reviewed the English literature through PubMed from 2000 to the present, using the search terms medullary thyroid carcinoma, multiple endocrine neoplasia type 2, familial medullary thyroid carcinoma, RET proto-oncogene, and calcitonin.

EVIDENCE SYNTHESIS

Over 70 RET mutations are known to cause MEN2A, MEN2B, or FMTC, and recent findings from studies of large kindreds with these syndromes have clouded the relationship between genotype and phenotype, primarily because of the varied clinical presentation of different families with the same RET mutation. This clinical variability has also confounded decisions about the timing of prophylactic thyroidectomy for MTC, the dominant endocrinopathy associated with these syndromes. A distinct advance has been the demonstration through phase II and phase III clinical trials that molecular targeted therapeutics are effective in the treatment of patients with locally advanced or metastatic MTC.

CONCLUSIONS

The effective management of patients with MEN2A, MEN2A, and FMTC depends on an understanding of the variable behavior of disease expression in patients with a specific RET mutation. Information gained from molecular testing, biochemical analysis, and clinical evaluation is important in providing effective management of patients with either early or advanced-stage MTC.

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.

Succinate dehydrogenase deficiency in pediatric and adult gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) in adults are generally driven by somatic gain-of-function mutations in KIT or PDGFRA, and biological therapies targeted to these receptor tyrosine kinases comprise part of the treatment regimen for metastatic and inoperable GISTs. A minority (10-15%) of GISTs in adults, along with ∼85% of pediatric GISTs, lacks oncogenic mutations in KIT and PDGFRA. Not surprisingly these wild type (WT) GISTs respond poorly to kinase inhibitor therapy. A subset of WT GISTs shares a set of distinguishing clinical and pathological features, and a flurry of recent reports has convincingly demonstrated shared molecular characteristics. These GISTs have a distinct transcriptional profile including over-expression of the insulin-like growth factor-1 receptor, and exhibit deficiency in the succinate dehydrogenase (SDH) enzyme complex. The latter is often but not always linked to bi-allelic inactivation of SDH subunit genes, particularly SDHA. This review will summarize the molecular, pathological, and clinical connections that link this group of SDH-deficient neoplasms, and offer a view toward understanding the underlying biology of the disease and the therapeutic challenges implicit to this biology.

Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo

Rearrangements of the proto-oncogene RET are newly identified potential driver mutations in lung adenocarcinoma (LAD). However, the absence of cell lines harboring RET fusion genes has hampered the investigation of the biological relevance of RET and the development of RET-targeted therapy. Thus, we aimed to identify a RET fusion positive LAD cell line. Eleven LAD cell lines were screened for RET fusion transcripts by reverse transcription-polymerase chain reaction. The biological relevance of the CCDC6-RET gene products was assessed by cell growth, survival and phosphorylation of ERK1/2 and AKT with or without the suppression of RET expression using RNA interference. The efficacy of RET inhibitors was evaluated in vitro using a culture system and in an in vivo xenograft model. Expression of the CCDC6-RET fusion gene in LC-2/ad cells was demonstrated by the mRNA and protein levels, and the genomic break-point was confirmed by genomic DNA sequencing. Mutations in KRAS and EGFR were not observed in the LC-2/ad cells. CCDC6-RET was constitutively active, and the introduction of a siRNA targeting the RET 3' region decreased cell proliferation by downregulating RET and ERK1/2 phosphorylation. Moreover, treatment with RET-inhibitors, including vandetanib, reduced cell viability, which was accompanied by the downregulation of the AKT and ERK1/2 signaling pathways. Vandetanib exhibited anti-tumor effects in the xenograft model. Endogenously expressing CCDC6-RET contributed to cell growth. The inhibition of kinase activity could be an effective treatment strategy for LAD. LC-2/ad is a useful model for developing fusion RET-targeted therapy.

The genetics of neuroendocrine tumors

Neuroendocrine tumors (NETs) present a wide spectrum of malignant diseases from rather benign to very malignant variants. The majority of these tumors are sporadic, but there are several familial (inherited) syndromes to consider, such as multiple endocrine neoplasia type 1 and type 2 (MEN-1 and MEN-2), von Hippel-Lindau syndrome (VHL), tuberosclerosis, and neurofibromatosis syndromes. The MEN-1 gene is mutated not only in MEN-1 families, but a recent study shows that more than 40% of sporadic pancreatic NETs (PNETs) harbor MEN-1 gene mutations. The same study reported that ATRX/DAXX genes are mutated in a significant number of tumors, as are genes encoding components of the mammalian target of rapamycin (mTOR) signal transduction pathway. These findings have implications for the new therapies that have been approved for the treatment of PNETs, such as the tyrosine kinase inhibitor sunitinib, as well the mTOR inhibitor everolimus. Small intestinal NETs show a less varied mutational pattern in that the majority of genetic alterations are found on chromosome 18. There seem to be no differences between the sporadic and the familiar type of small intestinal NETs (carcinoids). A wide range of genetic alterations have been described for the different subtypes of NETs, but the mechanisms underlying tumor development are essentially unknown except for MEN-2, in which an activating mutation of the RET proto-oncogene drives tumor progression and affords a direct genotype/phenotype correlation. Genome-wide screening of different types of NETs can now be performed for a reasonable price and is likely to generate new insights into the tumor biology and carcinogenesis in various subtypes of NETs.

Targeted agents in non-small cell lung cancer therapy: What is there on the horizon?

Lung cancer is a heterogeneous group of diseases. There has been much research in lung cancer over the past decade which has advanced our ability to treat these patients with a more personalized approach. The scope of this paper is to review the literature and give a broad understanding of the current molecular targets for which we currently have therapies as well as other targets for which we may soon have therapies. Additionally, we will cover some of the issues of resistance with these targeted therapies. The molecular targets we intend to discuss are epidermal growth factor receptor (EGFR), Vascular endothelial growth factor (VEGF), anaplastic large-cell lymphoma kinase (ALK), KRAS, C-MET/RON, PIK3CA. ROS-1, RET Fibroblast growth factor receptor (FGFR). Ephrins and their receptors, BRAF, and immunotherapies/vaccines. This manuscript only summarizes the work which has been done to date and in no way is meant to be comprehensive.

Molecular diagnosis of primary hyperparathyroidism in familial cancer syndromes

In the last few years, causative genes have been identified for most of the familial hyperparathyroidism conditions. Germline mutations in the tumour suppressors multiple endocrine neoplasia type 1 (MEN1) and hyperparathyroidism 2 (HRPT2) provide a molecular diagnosis of multiple endocrine neoplasia type 1 and hyperparathyroidism jaw tumour syndrome, respectively. Germline mutations in the proto-oncogene RET (rearranged during transfection) provide a molecular diagnosis of multiple endocrine neoplasia type 2. Germline mutations of both MEN1 and, less frequently HRPT2, have been found in familial isolated hyperparathyroidism. A molecular diagnosis can now be incorporated into the management of patients with these conditions, however, the ease of diagnostics and value of genetic information in the context of clinical screening and early surgical intervention varies between these disorders. This review focuses on familial hyperparathyroidism and its known causative genes in the setting of neoplastic syndromes, with particular discussion of recent developments in the molecular diagnosis of parathyroid carcinoma.

Novel tandem germline RET proto-oncogene mutations in a patient with multiple endocrine neoplasia type 2B: report of a case and a literature review of tandem RET mutations with in silico analysis

BACKGROUND

Multiple endocrine neoplasia type 2B (MEN2B) is the rarest and most aggressive form of MEN2. MEN2B cases usually carry either an M918T or A883T mutation of the RET, but to date, there are 3 atypical MEN2B caused by tandem mutations.

METHODS AND RESULTS

A 32-year-old woman with no family history of medullary thyroid carcinoma (MTC) presented with a neck tumor and multiple mucosal nodules. She was diagnosed with MEN2B. Genetic analyses of RET revealed that she had 2 mutations, Q781R and V804M. Subclone and genetic analyses revealed that Q781R was on the paternal allele and V804M was a de novo. In silico analysis of the tandem mutations showed a high prediction score.

CONCLUSIONS

We describe a novel combination of tandem RET mutations (Q781R/V804M) in a MEN2B-like patient. In silico analysis showed a high prediction score, which was compatible with the clinical phenotype in the present case.

Molecular pathogenesis and mechanisms of thyroid cancer

Thyroid cancer is a common endocrine malignancy. There has been exciting progress in understanding its molecular pathogenesis in recent years, as best exemplified by the elucidation of the fundamental role of several major signalling pathways and related molecular derangements. Central to these mechanisms are the genetic and epigenetic alterations in these pathways, such as mutation, gene copy-number gain and aberrant gene methylation. Many of these molecular alterations represent novel diagnostic and prognostic molecular markers and therapeutic targets for thyroid cancer, which provide unprecedented opportunities for further research and clinical development of novel treatment strategies for this cancer.

KIF5B-RET fusions in Chinese patients with non-small cell lung cancer

BACKGROUND

It has been established that "ret proto-oncogene" (RET) fusions are oncogenic drivers in non-small cell lung cancer (NSCLC). The prevalence and clinicopathologic characteristics of RET fusions in Chinese patients with NSCLC remain unclear. The objective of the current study was to determine the prevalence and clinicopathologic characteristics of KIF5B-RET fusions (fusions of the RET and kinesin family member 5B [KIF5B] genes) in Chinese patients with NSCLC.

METHODS

The authors screened for KIF5B-RET fusions in 392 patients with NSCLC using multiplex real-time polymerase chain reaction assay and validated all positive samples using direct sequencing. The relations between KIF5B-RET fusions and clinicopathologic characteristics were analyzed.

RESULTS

In total, 6 patients (1.5%) were identified who harbored KIF5B-RET fusions. Of these, 4 had adenocarcinoma, 1 had a malignant neuroendocrine tumor, and 1 had squamous cell carcinoma. All patients who were positive for a KIF5B-RET fusion were never-smokers. There was no statistically significant difference in age, sex, smoking status, pathologic stage, or histologic type between patients with and without KIF5B-RET fusions. Patients without KIF5B-RET fusions had a better prognosis than those with KIF5B-RET fusions (median survival, 52.6 months vs 21.0 months; P = .06), with a hazard ratio of 2.398 (95% confidence interval, 0.982-5.856; P = .055) on multivariate analysis. Disease stage (hazard ratio, 2.879) and younger age (<65 years; hazard ratio, 1.485) were identified as independent prognostic factors for better survival.

CONCLUSIONS

KIF5B-RET fusions were quite rare, with a prevalence of approximately 1.5% in Chinese patients with NSCLC, and they were a little more common in patients with adenocarcinoma than in those with squamous carcinoma (1.73% vs 0.84%). In addition, KIF5B-RET fusions also existed in patients with low-grade malignant neuroendocrine tumors.

Structure and physiology of the RET receptor tyrosine kinase

The identification of the ret oncogene by Masahide Takahashi and Geoffrey Cooper in 1985 was both serendipitous and paradigmatic ( Takahashi et al. 1985). By transfecting total DNA from a human lymphoma into mouse NIH3T3 cells, they obtained one clone, which in secondary transformants yielded more than 100-fold improvement in transformation efficiency. Subsequent investigations revealed that the ret oncogene was not present as such in the primary lymphoma, but was derived by DNA rearrangement during transfection from normal human sequences of the ret locus. At the time, activation by DNA rearrangement had not been previously described for a transforming gene with the NIH3T3 transfection assay. The discovery of ret opened a field of study that has had a profound impact in cancer research, developmental biology, and neuroscience, and that continues to yield surprises and important insights to this day.

Phosphotyrosine signaling proteins that drive oncogenesis tend to be highly interconnected

Mutation and overexpression of receptor tyrosine kinases or the proteins they regulate serve as oncogenic drivers in diverse cancers. To better understand receptor tyrosine kinase signaling and its link to oncogenesis, we used protein microarrays to systematically and quantitatively measure interactions between virtually every SH2 or PTB domain encoded in the human genome and all known sites of tyrosine phosphorylation on 40 receptor tyrosine kinases and on most of the SH2 and PTB domain-containing adaptor proteins. We found that adaptor proteins, like RTKs, have many high affinity bindings sites for other adaptor proteins. In addition, proteins that drive cancer, including both receptors and adaptor proteins, tend to be much more highly interconnected via networks of SH2 and PTB domain-mediated interactions than nononcogenic proteins. Our results suggest that network topological properties such as connectivity can be used to prioritize new drug targets in this well-studied family of signaling proteins.