"Graded early warning system" of RET germline mutation carriers in MEN2A/MEN2B families and total thyroidectomy (report of 7 cases) / 中华耳鼻咽喉头颈外科杂志

Objective: To explore the reasonable time of prophylactic thyroidectomy for RET gene carriers in multiple endocrine neoplasia(MEN) 2A/2B families. Methods: From May 2015 to August 2021, RET gene carriers in MEN2A/MEN2B families were dynamically followed up at the Department of Thyroid Head and Neck Surgery, Beijing Tongren Hospital of Capital Medical University. The high-risk patients were encouraged to undergo prophylacitc total thyroidectomy according to the principle of "graded early warning system", namely the evaluation of gene detection, calcitonin value and ultrasound examination successively. Seven cases underwent the surgery, including 3 males and 4 females, aged from 7 to 29 years. According to the risk stratification listed in the guidelines of the American Thyroid Association in 2015, there were 2 cases of the highest risk, 2 cases of the high risk and 3 cases of the modest risk. Calcitonin index remained within the normal range in 3 cases and elevated in 4 cases before operation. All 7 patients underwent thyroidectomy with lymph node dissection of the level Ⅵ performed in 4 patients. Results: The time from suggestion to operation was 2 to 37 months, with an average of 15.1 months. The 6 patients were medullary thyroid carcinoma and 1 case with C-cell hyperplasia. The follow-up time was 2 to 82 months, with an average of 38.4 months. Postoperative serum calcitonin levels of all cases decreased to normal level, with biochemical cure. There was no sign of recurrence on ultrasound examination. All 7 patients had no serious complications, no obvious thyroid dysfunction. Their height, weight and other indicators of pediatric patients were similar to those of their peers, with normal growth and development. Conclusion: For healthy people with MEN2A/MEN2B family history, prophylactic thyroidectomy can be carried out selectively based on the comprehensive evaluation of "graded early warning system" with strict screening and close monitoring.

Progress and challenges in RET-targeted cancer therapy / 医学前沿

The rearranged during transfection (RET) is a receptor protein tyrosine kinase. Oncogenic RET fusions or mutations are found most often in non-small cell lung cancer (NSCLC) and in thyroid cancer, but also increasingly in various types of cancers at low rates. In the last few years, two potent and selective RET protein tyrosine kinase inhibitors (TKIs), pralsetinib (BLU-667) and selpercatinib (LOXO-292, LY3527723) were developed and received regulatory approval. Although pralsetinib and selpercatinib gave high overall response rates (ORRs), < 10% of patients achieved a complete response (CR). The RET TKI-tolerated residual tumors inevitably develop resistance by secondary target mutations, acquired alternative oncogenes, or MET amplification. RET G810 mutations located at the kinase solvent front site were identified as the major on-target mechanism of acquired resistance to both selpercatinib and pralsetinib. Several next-generation of RET TKIs capable of inhibiting the selpercatinib/pralsetinib-resistant RET mutants have progressed to clinical trials. However, it is likely that new TKI-adapted RET mutations will emerge to cause resistance to these next-generation of RET TKIs. Solving the problem requires a better understanding of the multiple mechanisms that support the RET TKI-tolerated persisters to identify a converging point of vulnerability to devise an effective co-treatment to eliminate the residual tumors.

Advances in the Treatment of RET Fusion-positive Advanced Non-small Cell Lung Cancer / 中国肺癌杂志

Rearranged during transfection (RET) fusions are found in 0.7% to 2% of non-small cell lung cancer (NSCLC). Fusions between RET gene and other domains represent the distinct biological and clinicopathological subtypes of NSCLC. Recent years have witnessed the remarkable advancement of RET fusion-positive advanced NSCLC therapy. Conventional chemotherapy produced moderate clinical benefits. Prior to the introduction of targeted therapy or in the context of unavailability, platinum-based systemic regimens are initial therapy options. Immunotherapy predicted minimal response in the presence of RET fusions while currently available data have been scarce, and the single-agent immunotherapy or in combination with chemotherapy regimens are not recommended as initial systemic therapy in this population. The repurpose of multi-target kinase inhibitors in patients with RET fusion-positive NSCLC showed encouraging therapeutic activity, with only cabozantinib and vandetanib being recommended as initial or subsequent options under certain circumstances. However, there are still unmet clinical needs. Pralsetinib and selpercatinib have been developed as tyrosine kinase inhibitors (TKI) selectively targeting RET variation of fusions or mutations, and both agents significantly improved the prognosis of patients with RET fusion-positive NSCLC. Pralsetinib and selpercatinib have been established as preferred first-line therapy or subsequent therapy options. As observed with other TKIs treatment, resistance has also been associated with RET targeted inhibition, and the acquired resistance eventually affect the long-term therapeutic effectiveness, leading to limited subsequent treatment options. Therefore, it is essential to identify resistance mechanisms to TKI in RET fusion-positive advanced NSCLC to help reveal and establish new strategies to overcome resistance. Here, we review the advances in the treatment of RET fusion-positive advanced NSCLC.
.

Multiple endocrine neoplasia-IIb with RET gene mutation p.M918T： A case report / 中南大学学报(医学版)

Multiple endocrine neoplasia-IIb (MEN-IIb) is a rare hereditary autosomal dominant syndrome caused by mutations in the RET proto-oncogene. It's characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO), mucosal neuromas, and Marfanoid habitus. Because of the rarity of MEN-IIb and finiteness of clinical cognition, the majority of the patients suffer a delayed diagnosis. A MEN-IIb patient with the lingual mucosal neuromas since childhood was admitted in the Third Xiangya Hospital of Central South University in November, 2018. He had surgical history of mitral valve prolapse and spinal deformity. He was diagnosed with MTC and PHEO at the age of 22 and 28, respectively, and received surgical treatments. Sequencing of RET gene revealed a de novo heterozygous p.M918T mutation in the patient. Being aware of the unique clinical phenotype and screening of RET gene mutation may lead to the early diagnosis and better long-term outcome for MEN-IIb.

Association of rs2435357 and rs1800858 polymorphisms in ret proto-oncogene with hirschsprung disease: systematic review and meta-analysis / Associação dos polimorfismos rs2435357 e rs1800858 no proto-oncogene ret com doença de hirschsprung: revisão sistemática e metanálise

ABSTRACT Introduction: Many published studies have estimated the association of rs2435357 and rs1800858 polymorphisms in the proto-oncogene rearranged during transfection (RET) gene with Hirschsprung disease (HSCR) risk. However, the results remain inconsistent and controversial. Aim: To perform a meta-analysis get a more accurate estimation of the association of rs2435357 and rs1800858 polymorphisms in the RET proto-oncogene with HSCR risk. Methods: The eligible literatures were searched by PubMed, Google Scholar, EMBASE, and Chinese National Knowledge Infrastructure (CNKI) up to June 30, 2018. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the susceptibility to HSCR. Results: A total of 20 studies, including ten (1,136 cases 2,420 controls) for rs2435357 and ten (917 cases 1,159 controls) for rs1800858 were included. The overall results indicated that the rs2435357 (allele model: OR=0.230, 95% CI 0.178-0.298, p=0.001; homozygote model: OR=0.079, 95% CI 0.048-0.130, p=0.001; heterozygote model: OR=0.149, 95% CI 0.048-0.130, p=0.001; dominant model: OR=0.132, 95% CI 0.098-0.179, p=0.001; and recessive model: OR=0.239, 95% CI 0.161-0.353, p=0.001) and rs1800858 (allele model: OR=5.594, 95% CI 3.653-8.877, p=0.001; homozygote model: OR=8.453, 95% CI 3.783-18.890, p=0.001; dominant model: OR=3.469, 95% CI 1.881-6.396, p=0.001; and recessive model: OR=6.120, 95% CI 3.608-10.381, p=0.001) polymorphisms were associated with the increased risk of HSCR in overall. Conclusions: The results suggest that the rs2435357 and rs1800858 polymorphisms in the RET proto-oncogene might be associated with HSCR risk.

RESUMO Introdução: Muitos estudos publicados estimaram a associação dos polimorfismos rs2435357 e rs1800858 do proto-oncogene rearranjado durante a transfecção (RET) com o risco de doença por Hirschsprung (HSCR). No entanto, os resultados permanecem inconsistentes e controversos. Objetivo: Realizar metanálise para obter estimativa mais precisa da associação dos polimorfismos rs2435357 e rs1800858 no proto-oncogene RET com risco de HSCR. Método: A literatura elegível foi pesquisada pelo PubMed, Google Scholar, EMBASE e CNKI até 30 de junho de 2018. Resultados: Um total de 20 estudos, incluindo dez (1.136 casos 2.420 controles) para rs2435357 e dez (917 casos 1.159 controles) para rs1800858 foram incluídos. Os resultados globais indicaram que o rs2435357 (modelo alelo: OR=0,230, IC 95% 0,178-0,298, p=0,001; modelo homozigoto: OR=0,079, IC 95% 0,048-0,130, p=0,001; modelo heterozigoto: OR=0,149 , IC 95% 0,048-0,130, p=0,001, modelo dominante: OR=0,132, IC 95% 0,098-0,179, p=0,001 e modelo recessivo: OR=0,239, IC 95% 0,161-0,353, p=0,001) e rs1800858 (modelo alelo: OR=5,594, IC 95% 3,653-8,877, p=0,001; modelo homozigoto: OR=8,453, IC 95% 3,783-18,890, p=0,001; modelo dominante: OR=3,469, IC 95% 1,881- 6,396, p=0,001 e modelo recessivo: OR=6,120, 95% CI 3,608-10,381, p=0,001) polimorfismos foram associados com o aumento do risco de HSCR em geral. Conclusões: Os resultados sugerem que os polimorfismos rs2435357 e rs1800858 no proto-oncogene RET podem estar associados ao HSCR.

A pioneering RET genetic screening study in the State of Ceará, Brazil, evaluating patients with medullary thyroid cancer and at-risk relatives: experience with 247 individuals

ABSTRACT Objective: Initial diagnosis of medullary thyroid carcinoma (MTC) is frequently associated with advanced stages and a poor prognosis. Thus, the need for earlier diagnoses and detection in relatives at risk for the disease has led to increased use of RET genetic screening. Subjects and methods: We performed RET screening in 247 subjects who were referred to the Brazilian Research Consortium for Multiple Endocrine Neoplasia (BRASMEN) Center in the State of Ceará. Direct genetic sequencing was used to analyze exons 8, 10, 11, and 13-16 in MTC index cases and specific exons in at risk relatives. Afterward, clinical follow-up was offered to all the patients with MTC and their affected relatives. Results: RET screening was performed in 60 MTC index patients and 187 at-risk family members. At the initial clinical assessment of the index patients, 54 (90%) were diagnosed with apparently sporadic disease and 6 (10%) diagnosed with hereditary disease. After RET screening, we found that 31 (52%) index patients had sporadic disease, and 29 (48%) had hereditary disease. Regarding at-risk relatives, 73/187 were mutation carriers. Mutations in RET codon 804 and the rare p.M918V mutation were the most prevalent. Conclusions: Performing RET screening in Ceará allowed us to identify a different mutation profile in this region compared with other areas. RET screening also enabled the diagnosis of a significant number of hereditary MTC patients who were initially classified as sporadic disease patients and benefited their relatives, who were unaware of the risks and the consequences of bearing a RET mutation.

Germline gene testing of the RET, VHL, SDHD and SDHB genes in patients with pheochromocytoma/paraganglioma / 北京大学学报(医学版)

OBJECTIVE@#To analyze the germline variations of genes RET, VHL, SDHD and SDHB in patients with pheochromocytoma and/or paraganglioma and to evaluate variations of these genes in Chinese patients.@*METHODS@#Patients who were treated in Peking University First Hospital from September 2012 to March 2014 and diagnosed with pheochromocytoma and/or paraganglioma by pathologists were included in this study. Twelve patients were included in total, of whom 11 had pheochromocytoma, and 1 had paraganglioma. Deoxyribonucleic acid (DNA) was extracted from the leukocytes of peripheral blood of the patients. The exons 10, 11, 13-16 of the RET gene, and all exons of VHL, SDHB and SDHD genes and their nearby introns (±20 bp) were amplified with polymerase chain reactions, and the products were sent to a biotechnology company for sequencing. The sequencing results were compared with wildtype sequences of these genes to identify variations. One of the patients was diagnosed with multiple endocrine neoplasia type 2A. A family analysis was performed in his kindred, and his family members received genetic tests for the related variations.@*RESULTS@#Three patients were found to have germline gene variations. A c.136C>T (p.R46X) variation of the SDHB gene was found in a patient with malignant pheochromocytoma. A c.1901G>A (C634Y) variation, as well as c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene were found in a patient with multiple endocrine neoplasia type 2A. After a family analysis, five family members of this patient were found to have the same variations. c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene were also found in a clinical sporadic patient without evidence of malignancy. A patient with congenital single ventricle malformation and pheochromocytoma was included in this study, and no variation with clinical significance was found in the four genes of this patient.@*CONCLUSION@#25% (3/12) patients with pheochromocytoma or paraganglioma were found to have missense or nonsense germline gene variations in this study, including the c.136C>T (p.R46X) variation of the SDHB gene, the c.1901G>A (C634Y) variation of the RET gene, and c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene. The former two variations have already been confirmed to be pathogenic. The existence of these variations in Chinese patients with pheochromocytoma and/or paraganglioma was validated in this study, which supports the conclusion that genetic testing is necessary to be generally performed in patients with pheochromocytoma and/or paraganglioma.

Diagnóstico, tratamento e seguimento do carcinoma medular de tireoide: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia / Diagnosis, treatment, and follow-up of medullary thyroid carcinoma: recommendations by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism

Introdução O carcinoma medular de tireoide (CMT) origina-se das células parafoliculares da tireoide e corresponde a 3-4% das neoplasias malignas da glândula. Aproximadamente 25% dos casos de CMT são hereditários e decorrentes de mutações ativadoras no proto-oncogene RET (REarranged during Transfection). O CMT é uma neoplasia de curso indolente, com taxas de sobrevida dependentes do estádio tumoral ao diagnóstico. Este artigo descreve diretrizes baseadas em evidências clínicas para o diagnóstico, tratamento e seguimento do CMT. Objetivo O presente consenso, elaborado por especialistas brasileiros e patrocinado pelo Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia, visa abordar o diagnóstico, tratamento e seguimento dos pacientes com CMT, de acordo com as evidências mais recentes da literatura. Materiais e métodos: Após estruturação das questões clínicas, foi realizada busca das evidências disponíveis na literatura, inicialmente na base de dados do MedLine-PubMed e posteriormente nas bases Embase e SciELO – Lilacs. A força das evidências, avaliada pelo sistema de classificação de Oxford, foi estabelecida a partir do desenho de estudo utilizado, considerando-se a melhor evidência disponível para cada questão. Resultados Foram definidas 11 questões sobre o diagnóstico, 8 sobre o tratamento cirúrgico e 13 questões abordando o seguimento do CMT, totalizando 32 recomendações. Como um todo, o artigo aborda o diagnóstico clínico e molecular, o tratamento cirúrgico inicial, o manejo pós-operatório e as opções terapêuticas para a doença metastática. Conclusões O diagnóstico de CMT deve ser suspeitado na presença de nódulo tireoidiano e história ...

Introduction Medullary thyroid carcinoma (MTC) originates in the thyroid parafollicular cells and represents 3-4% of the malignant neoplasms that affect this gland. Approximately 25% of these cases are hereditary due to activating mutations in the REarranged during Transfection (RET) proto-oncogene. The course of MTC is indolent, and survival rates depend on the tumor stage at diagnosis. The present article describes clinical evidence-based guidelines for the diagnosis, treatment, and follow-up of MTC. Objective The aim of the consensus described herein, which was elaborated by Brazilian experts and sponsored by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism, was to discuss the diagnosis, treatment, and follow-up of individuals with MTC in accordance with the latest evidence reported in the literature. Materials and methods: After clinical questions were elaborated, the available literature was initially surveyed for evidence in the MedLine-PubMed database, followed by the Embase and Scientific Electronic Library Online/Latin American and Caribbean Health Science Literature (SciELO/Lilacs) databases. The strength of evidence was assessed according to the Oxford classification of evidence levels, which is based on study design, and the best evidence available for each question was selected. Results Eleven questions corresponded to MTC diagnosis, 8 corresponded to its surgical treatment, and 13 corresponded to follow-up, for a total of 32 recommendations. The present article discusses the clinical and molecular diagnosis, initial surgical treatment, and postoperative management of MTC, as well as the therapeutic options for metastatic disease. Conclusions 7 .

Genetic analysis of a Chinese Han family with multiple endocrine neoplasia type 2A.

Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant disorder that can be distinguished as three different syndromes: multiple endocrine neoplasia type 2A (MEN2A), MEN2B and familial medullary thyroid carcinoma (FMTC). This disorder is usually caused by the mutations of the rearranged during transfection protooncogene gene (RET) or the neurotrophic tyrosine kinase receptor type 1 gene (NTRK1). To investigate the genetic cause in a Chinese Han family with MEN2A and the genotype-phenotype correlations, nine members belonging to 3 generations of MEN2A family with 5 affected subjects underwent genetic analysis. Standard GTG-banded karyotype analysis and sequencing of the RET and NTRK1 genes were performed to identify the genetic cause of this family. A heterozygous mutation p.Cys634Arg in the RET gene was identified in 5 patients with MEN2A and one asymptomatic family member. The phenotype of patients was that of classic MEN2A, characterized by medullary thyroid carcinoma and phaeochromocytoma. The clinical features of all cases with RET mutations varied greatly, including onset age of clinical manifestations, severity and comorbidities. Thus, this study not only identified the hereditary nature of the MEN2A in the cases, but also discovered a family member harboring the same p.Cys634Arg mutation, who was unaware of his condition. These finding may provide new insights into the cause and diagnosis of MEN2A and have implications for genetic counseling.

RET Fusion Genes in Korean Non-Small Cell Lung Cancer

Recently, rearranged during transfection (RET) fusions have been identified in approximately 1% of non-small cell lung cancer (NSCLC). To know the prevalence of RET fusion genes in Korean NSCLCs, we examined the RET fusion genes in 156 surgically resected NSCLCs using a reverse transcriptase polymerase chain reaction. Two KIF5B-RET fusions and one CCDC6-RET fusion were identified. All three patients were females and never smokers with adenocarcinomas. RET fusion genes were mutually exclusive from EGFR, KRAS mutations and EML4-ALK fusion. RET fusion genes occur 1.9% (3 of 156) of surgically treated NSCLC patients in Koreans.

A Case of Medullary Thyroid Carcinoma with de novo V804M RET Germline Mutation

Many cases of RET proto-oncogene mutations of hereditary medullary thyroid carcinoma (MTC) have been reported in Korea. However, MTC with V804M RET proto-oncogene germline mutations have not been reported in Korea. A 33-yr-old man was diagnosed with a 0.7-cm sized thyroid nodule. Laboratory testing revealed serum calcitonin was elevated. The patient underwent total thyroidectomy with central compartment neck dissection for the thyroid tumor. RET gene analysis was performed in both the index patient and his family. There were no V804M RET mutation and abnormal laboratory findings within his family except the index patient. Therefore, this patient was a de novo V804M RET germline mutation.

The rare intracellular RET mutation p.Ser891Ala in an apparently sporadic medullary thyroid carcinoma: a case report and review of the literature / Rara mutação intracelular p.Ser891Ala do RET em carcinoma medular de tireoide aparentemente esporádico: relato de caso e revisão da literatura

Medullary thyroid carcinoma (MTC) is a malignant tumor originating from parafollicular C-cells and accounts for 4-10% of all thyroid carcinomas. MTC develops in either sporadic (75%) or hereditary form (25%). Mutations in the RET proto-oncogene are responsible for hereditary MTC and the rate of heritable disease among apparently sporadic MTC (sMTC) cases varies from 6 to 15%. RET genetic testing is now considered fundamental in MTC management but the extent of the molecular analysis required to exclude inherited disease is still controversial. While the screening of all known mutation loci is recommended by some authors, the high costs associated with a full analysis should be also taken into consideration. Here, we illustrate and discuss this controversial issue by reporting a patient who present all characteristic features of sMTC, and in whom a standard genetic analysis by restriction enzyme restriction excluded hereditary disease. Nevertheless, an extensive molecular analysis that included all codons was prompted by the diagnosis of thyroid neoplasm in a patient's sister, and identified the rare intracellular RET p.Ser891Ala mutation. Arq Bras Endocrinol Metab. 2012;56(8):586-91.

O carcinoma medular de tireoide (CMT) é um tumor maligno originado das células C parafoliculares e corresponde a 4-10% de todos os carcinomas de tireoide. O CMT se desenvolve ou de forma esporádica (75%) ou hereditária (25%). As mutações no proto-oncogene RET são responsáveis pelo CMT hereditário, e a ocorrência de doença hereditária entre casos aparentemente esporádicos de CMT varia de 6 a 15%. A avaliação genética do RET é considerada fundamental no manejo do CMT, mas a extensão de análise molecular necessária para se excluir a doença hereditária ainda é controversa. Embora a avaliação de todos os loci de mutação conhecidos seja recomendada por alguns autores, os altos custos associados com a análise completa devem ser considerados. Neste relato, ilustramos e discutimos esse assunto controverso por meio do caso de um paciente que apresentou todas as características clássicas de CMT esporádico e no qual a análise genética por restrição enzimática excluiu a doença hereditária. No entanto, devido ao diagnóstico de uma neoplasia de tireoide em uma irmã do paciente, foi indicada uma análise molecular mais extensa que identificou a rara mutação intracelular p.Ser891Ala no proto-oncogene RET. Arq Bras Endocrinol Metab. 2012;56(8):586-91.

RET codon 609 mutations: a contribution for better clinical managing

Medullary thyroid carcinoma currently accounts for 5-8% of all thyroid cancers. The clinical course of this disease varies from extremely indolent tumors that can go unchanged for years to an extremely aggressive variant that is associated with a high mortality rate. As many as 75% of all medullary thyroid carcinomas are sporadic, with an average age at presentation reported as 60 years, and the remaining 25% are hereditary with an earlier age of presentation, ranging from 20 to 40 years. Germline RET proto-oncogene mutations are the genetic causes of multiple endocrine neoplasia type 2 and a strong genotype-phenotype correlation exists, particularly between a specific RET codon mutation and the (a) age-related onset and (b) thyroid tumor progression, from C-cell hyperplasia to medullary thyroid carcinoma and, ultimately, to nodal metastases. RET mutations predispose an individual to the development of medullary thyroid carcinomas and can also influence the individual response to RET protein receptor-targeted therapies. RET codon 609point mutations are rare genetic events belonging to the intermediate risk category for the onset of medullary thyroid carcinoma. A large genealogy resulting in a less aggressive form of medullary thyroid carcinoma is associated with the high penetrance of pheochromocytoma and has been reported in the literature. In this short review article, we comment on our previous report of a large multiple endocrine neoplasia type 2A kindred with the same Cys609Ser germline RET mutation in which, conversely, the syndrome was characterized by a slightly aggressive, highly penetrant form of medullary thyroid carcinoma that was associated with low penetrance of pheochromocytoma and primary hyperparathyroidism.

RET haplotype, not linked to the C620R activating mutation, associated with Hirschsprung disease in a novel MEN2 family

Hirschsprung disease is a congenital form of aganglionic megacolon that results from cristopathy. Hirschsprung disease usually occurs as a sporadic disease, although it may be associated with several inherited conditions, such as multiple endocrine neoplasia type 2. The rearranged during transfection (RET) proto-oncogene is the major susceptibility gene for Hirschsprung disease, and germline mutations in RET have been reported in up to 50% of the inherited forms of Hirschsprung disease and in 15-20% of sporadic cases of Hirschsprung disease. The prevalence of Hirschsprung disease in multiple endocrine neoplasia type 2 cases was recently determined to be 7.5% and the cooccurrence of Hirschsprung disease and multiple endocrine neoplasia type 2 has been reported in at least 22 families so far. It was initially thought that Hirschsprung disease could be due to disturbances in apoptosis or due to a tendency of the mutated RET receptor to be retained in the Golgi apparatus. Presently, there is strong evidence favoring the hypothesis that specific inactivating haplotypes play a key role in the fetal development of congenital megacolon/Hirschsprung disease. In the present study, we report the genetic findings in a novel family with multiple endocrine neoplasia type 2: a specific RET haplotype was documented in patients with Hirschsprung disease associated with medullary thyroid carcinoma, but it was absent in patients with only medullary thyroid carcinoma. Despite the limited number of cases, the present data favor the hypothesis that specific haplotypes not linked to RET germline mutations are the genetic causes of Hirschsprung disease.

The Hirschsprung's-multiple endocrine neoplasia connection

The risk of patients with Hirschsprung's disease later developing multiple endocrine neoplasia remains a matter of concern. The multiple endocrine neoplasia 2-Hirschsprung's disease association has been shown to cosegregate in Hirschsprung's disease patients with both short- and long-segment aganglionosis, although patients with long-segment aganglionosis a to carry the greatest risk. The Hirschsprung's disease-medullary thyroid carcinoma relationship also appears to be bi-directional, and activation or suppression of the rearranged during transfection gene appeared to vary over succeeding generations within the same family. Rearranged during transfection gene variations are associated with both conditions. The cosegregation of Hirschsprung's disease and multiple endocrine neoplasia 2 is particularly interesting as it involves both "switch off" and "switch on" of the rearranged during transfection proto-oncogene in the same patient. This cosegregation mostly relates to the cysteine-rich area on RET620 (the "Janus gene"). The mechanism whereby rearranged during transfection influences gene activation in multiple endocrine neoplasia 2 is complex, but genetic variations impair the rearranged during transfection tyrosine kinase response to tyrosine kinase activation, thus appearing to dictate downstream signaling cascade responses. Better understanding of the RET-620 relationship allows for a more cost-effective method of identifying those at risk by focusing rearranged during transfection gene testing to this specific area as a "hot spot". The clinical awareness of possible medullary thyroid carcinoma has led to timely intervention and early treatment of this chemo- and radioresistant tumor with poor prognosis. Establishment of "risk" by genetic testing has become a classic model of molecular medicine being integrated into patient care and offering rearranged during transfection directed prophylactic surgical management. In addition, novel approaches to treatment based on this genetic knowledge have already shown early promise in randomized clinical trials.

Genotype-phenotype correlation in multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 is an autosomal-dominant hereditary cancer syndrome caused by missense gain-of-function mutations of the rearranged during transfection proto-oncogene, which encodes the receptor tyrosine kinase, on chromosome 10. It has a strong penetrance of medullary thyroid carcinomas and can be associated with bilateral pheochromocytoma and primary hyperparathyroidism. Multiple endocrine neoplasia type 2 is divided into three varieties depending on its clinical features: multiple endocrine neoplasia type 2A, multiple endocrine neoplasia type 2B, and familial medullary thyroid carcinoma. The specific rearranged during transfection mutation may suggest a predilection toward a particular phenotype and clinical course of medullary thyroid carcinoma, with strong genotype-phenotype correlations. Offering rearranged during transfection testing is the best practice for the clinical management of patients at risk of developing multiple endocrine neoplasia type 2, and multiple endocrine neoplasia type 2 has become a classic model for the integration of molecular medicine into patient care. Recommendations on the timing of prophylactic thyroidectomy and extent of surgery are based on the classification of rearranged during transfection mutations into risk levels according to genotype-phenotype correlations. Earlier identification of patients with hereditary medullary thyroid carcinoma can change the presentation from clinical tumor to preclinical disease, resulting in a high cure rate of affected patients and a much better prognoses.

Molecular mechanisms of RET receptor-mediated oncogenesis in multiple endocrine neoplasia 2

Multiple endocrine neoplasia type 2 is an inherited cancer syndrome characterized by tumors of thyroid and adrenal tissues. Germline mutations of the REarranged during Transfection (RET) proto-oncogene, leading to its unregulated activation, are the underlying cause of this disease. Multiple endocrine neoplasia type 2 has been a model in clinical cancer genetics, demonstrating how knowledge of the genetic basis can shape the diagnosis and treatment of the disease. Here, we discuss the nature and effects of the most common recurrent mutations of RET found in multiple endocrine neoplasia type 2. Current understanding of the molecular mechanisms of RET mutations and how they alter the structure and function of the RET protein leading to its aberrant activation, and the effects on RET localization and signaling are described.

Over-representation of the G12S polymorphism of the SDHD gene in patients with MEN2A syndrome

OBJECTIVE: To evaluate whether germline variants of the succinate dehydrogenase genes might be phenotypic modifiers in patients with multiple endocrine neoplasia type 2. Mutations of genes encoding subunits of the succinate dehydrogenase are associated with hereditary paraganglioma/pheochromocytoma syndrome. Pheochromocytoma is one of the main manifestations of multiple endocrine neoplasia type 2 caused by germline mutation of the rearranged during transfection proto-oncogene. METHODS: Polymorphisms of the succinate dehydrogenase genes were analyzed in 77 rearranged during transfection mutation carriers, 47 patients with sporadic medullary thyroid cancer, 48 patients with sporadic Pheo, and 100 healthy individuals. Exons 10-16 of the rearranged during transfection proto-oncogene were analyzed by direct DNA sequencing, and all exons of the von Hippel-Lindau, succinate dehydrogenase B, and succinate dehydrogenase subunit D genes were tested by direct DNA sequencing and multiple ligation probe analysis. The G12S polymorphism of the succinate dehydrogenase subunit D gene was determined by restriction fragment length polymorphism. RESULTS: Of the 77 rearranged during transfection mutation carriers, 55 from 16 families had multiple endocrine neoplasia type 2A, three from three families had multiple endocrine neoplasia type 2B, and 19 from two families had familial medullary thyroid carcinoma. Eight of 55 (14.5%) patients with multiple endocrine neoplasia type 2A had this variant whereas it was absent in multiple endocrine neoplasia type 2B, familial medullary thyroid carcinoma, sporadic medullary thyroid carcinoma, and sporadic pheochromocytoma groups, and its prevalence in controls was 1% (p<0.002 multiple endocrine neoplasia type 2A versus controls). No associations between G12S and age of manifestation, incidence of pheochromocytoma or hyperparathyroidism, or level of serum calcitonin were observed. CONCLUSION: The high prevalence of the G12S variant in patients with multiple endocrine neoplasia type 2A raises questions about its role as a genetic modifier, but this proposal remains to be established.

Multiple endocrine neoplasia type 2: achievements and current challenges

Incremental advances in medical technology, such as the development of sensitive hormonal assays for routine clinical care, are the drivers of medical progress. This principle is exemplified by the creation of the concept of multiple endocrine neoplasia type 2, encompassing medullary thyroid cancer, pheochromocytoma, and primary hyperparathyroidism, which did not emerge before the early 1960s. This review sets out to highlight key achievements, such as joint biochemical and DNA-based screening of individuals at risk of developing multiple endocrine neoplasia type 2, before casting a spotlight on current challenges which include: (i) ill-defined upper limits of calcitonin assays for infants and young children, rendering it difficult to implement the biochemical part of the integrated DNA-based/biochemical concept; (ii) our increasingly mobile society in which different service providers are caring for one individual at various stages in the disease process. With familial relationships disintegrating as a result of geographic dispersion, information about the history of the origin family may become sketchy or just unavailable. This is when DNA-based gene tests come into play, confirming or excluding an individual's genetic predisposition to multiple endocrine neoplasia type 2 even before there is any biochemical or clinical evidence of the disease. However, the unrivaled molecular genetic progress in multiple endocrine neoplasia type 2 does not come without a price. Screening may uncover unknown gene sequence variants representing either harmless polymorphisms or pathogenic mutations. In this setting, functional characterization of mutant cells in vitro may generate helpful ancillary evidence with regard to the pathogenicity of gene variants in comparison with established mutations.

Surgical approach to medullary thyroid carcinoma associated with multiple endocrine neoplasia type 2

We briefly review the surgical approaches to medullary thyroid carcinoma associated with multiple endocrine neoplasia type 2 (medullary thyroid carcinoma/multiple endocrine neoplasia type 2). The recommended surgical approaches are usually based on the age of the affected carrier/patient, tumor staging and the specific rearranged during transfection codon mutation. We have focused mainly on young children with no apparent disease who are carrying a germline rearranged during transfection mutation. Successful management of medullary thyroid carcinoma in these cases depends on early diagnosis and treatment. Total thyroidectomy should be performed before 6 months of age in infants carrying the rearranged during transfection 918 codon mutation, by the age of 3 years in rearranged during transfection 634 mutation carriers, at 5 years of age in carriers with level 3 risk rearranged during transfection mutations, and by the age of 10 years in level 4 risk rearranged during transfection mutations. Patients with thyroid tumor >5 mm detected by ultrasound, and basal calcitonin levels >40 pg/ml, frequently have cervical and upper mediastinal lymph node metastasis. In the latter patients, total thyroidectomy should be complemented by extensive lymph node dissection. Also, we briefly review our data from a large familial medullary thyroid carcinoma genealogy harboring a germline rearranged during transfection Cys620Arg mutation. All 14 screened carriers of the rearranged during transfection Cys620Arg mutation who underwent total thyroidectomy before the age of 12 years presented persistently undetectable serum levels of calcitonin (<2 pg/ml) during the follow-up period of 2-6 years. Although it is recommended that preventive total thyroidectomy in rearranged during transfection codon 620 mutation carriers is performed before the age of 5 years, in this particular family the surgical intervention performed before the age of 12 years led to an apparent biochemical cure.