2A型多发性内分泌腺瘤家系RET原癌基因突变的分子筛查及五肽胃泌素激发试验的临床意义

目的 检测两个2A型多发性内分泌腺瘤（MEN2A）家系中RET原癌基因突变情况,初步探讨两个家系发病的分子机制及了解五肽胃泌素激发试验在MEN2A诊疗中的意义。方法 提取两个MEN2A家系共6名成员外周血基因组DNA,对RET原癌基因21个外显子进行PCR,PCR产物进行直接测序,对4例患者测定血降钙素并行五肽胃泌素激发试验。结果 两个家系中各有2例患者分别携带RET原癌基因外显子11的C634R突变和C634Y突变。初诊及复发的MEN2A患者血清降钙素明显升高（400．5～13 510．7ng／L,正常值16．6～132．8ng／L）,五肽胃泌素激发后升高更显著（494．1～33 901．9ng／L）。结论 本研究中临床诊断为MEN2A的家系存在RET原癌基因外显子11的C634位点突变。血降钙素水平及五肽胃泌素激发试验有助于临床诊断和疗效随访。     

五个多发性内分泌肿瘤2B家系的临床分析和RET原癌基因突变研究

目的研究5例多发性内分泌肿瘤(MEN)2B患者及其家族成员的临床表型和PET原癌基因突变。方法提取5例有典型临床表型的MEN2B患者及其23名家族成员外周血基因组DNA,对RET原癌基因第8、10、11、13、14、15、16外显子进行PCR产物直接测序。结果MEN2B临床表型和基因突变仅存在于5例先证者中,其家族成员均未发现；5例患者确诊MEN2B时的甲状腺髓样癌(MTC),类马凡体型,唇舌的黏膜神经瘤,眼部异常,肠道异常和嗜铬细胞瘤(PCC)的发生数分别为5、5、5、4、3和3；其MTC和PCC的发病年龄分别为(20．0±8．1)岁和(28．3±2．5)岁；RET基因突变均为第16外显子的M918T。结论本组MTC和PCC的平均发病年龄均晚于国外相关报道,且PCC发病晚于MTC；MEN2B其他相关临床症状的发生率大于国外报道,考虑与MEN2B确诊较晚有关。本组MEN2B先证者发生RET突变的家系比例(100%)要明显高于国外的相关报道(50%),且均为RET原癌基因的M918T单一突变。     

一个多发性内分泌腺瘤病2A型家系新的RET原癌基因突变方式

目的 探讨一个多发性内分泌腺瘤病2A型(MEN2A)家系的临床表现和RET原癌基因突变方式.方法 对一个MEN2A家系成员进行临床调查,提取其中3例具有典型临床表现的患者及15个家庭成员的外周血淋巴细胞DNA,对RET原癌基因的第8、10、11、13～16外显子进行DNA测序分析,并对发现突变的PCR产物进行亚克隆测序.结果 该家系先证者系30岁起先后确诊为嗜铬细胞瘤和甲状腺髓样癌的男性,其一姐患有嗜铬细胞瘤、一弟患有甲状腺髓样癌.在这3例患者及另外2例未发病的家庭成员中,发现了RET原癌基因第11号外显子存在相同的杂合突变,即1893-1895delCGA,系一种新的突变类型.结论 RET原癌基因第11号外显子1893-1895delCGA杂合突变,是一种新突变,可能为该MEN2A家系的致病基因.     

一个多发性内分泌腺瘤病2A型家系的RET原癌基因突变检测

目的 检测一个多发性内分泌腺瘤病(MEN)2A型家系中RET原癌基因的突变情况.方法 观察一个MEN2A家系成员的表型,并对与MEN相关的且点突变率较高的RET原癌基因第10和11外显子进行PCR产物直接DNA测序以了解其杂合性.结果 家系中4名家族成员均存在RET原癌基因第11外显子Cys(TGC)634Arg(CGC)错义突变和Gly(GGT)691Ser(AGT)的单核苷酸多态性,另有1名成员仅存在RET原癌基因Gly(GGT)691Set(AGT)的单核苷酸多态性.经B超检查发现其中2名成员双侧甲状腺及一侧肾上腺和一侧甲状旁腺有实性占位病变,1名成员双侧甲状腺及一侧肾上腺有实性占位病变,1名成员双侧甲状腺、双侧肾上腺和一侧甲状旁腺有实性占位病变,1名成员仅有甲状腺多发性小结节.另外有3名成员B超检查有异常,但无基因突变.结论 对MEN2A家系的基因分析证实RET原癌基因第11外显子634位密码子存在突变和(或)691位密码子存在单核苷酸多态性,对MEN2A能在基因水平作出诊断.     

多发性内分泌腺瘤2A型家系中ret原癌基因突变的分子筛查

目的 探寻2个多发性内分泌腺瘤2A型（MEN2A）家系发病的分子机制。方法 提取1982年和1992年中山大学附属第一医院收集的2个MEN2A家系共9名成员外周血基因组DNA，对ret原癌基因21个外显子进行聚合酶链反应（PCR），PCR产物进行直接测序。结果 家系1中2例患者存在ret原癌基因exonll的C634R突变，exon2的A45A和exon13的L769L 2处多态性；家系2中1例患者存在ret原癌基因C634Y突变，exon2的A45A存在多态性，另外筛查出其子为该基因突变携带者。结论 本研究2个家系存在exonll的C634位点突变，达到MEN2A基因水平上的诊断，对其临床治疗及其后代的早期诊断有重要指导意义。     

MENⅡA综合征家系的RET原癌基因突变及其临床意义

目的筛查1个MEN-ⅡA综合征家系的RET原癌基因突变位点,用于指导临床。方法对1个MEN-ⅡA综合征家系的5个成员外周血提取DNA,采用聚合酶链反应和DNA直接测序方法进行RET基因热点突变的第10、11外显子检测,并讨论MEN—ⅡA家系基因突变早期检测对预防性选择外科治疗的指导意义。结果第11外显子634密码子存在TGC→CGC突变,编码的氨基酸由Cys（半胱氨酸）变为Arg（精氨酸）。结论MEN—ⅡA综合征的早期基因诊断意义较大。     

多发性内分泌腺瘤2A型家系中ret原癌基因突变的分子筛查

目的探寻2个多发性内分泌腺瘤2A型(MEN2A)家系发病的分子机制。方法提取1982年和1992年中山大学附属第一医院收集的2个MEN2A家系共9名成员外周血基因组DNA,对ret原癌基因21个外显子进行聚合酶链反应(PCR),PCR产物进行直接测序。结果家系1中2例患者存在ret原癌基因exon11的C634R突变,exon2的A45A和exon13的L769L2处多态性;家系2中1例患者存在ret原癌基因C634Y突变,exon2的A45A存在多态性,另外筛查出其子为该基因突变携带者。结论本研究2个家系存在exon11的C634位点突变,达到MEN2A基因水平上的诊断,对其临床治疗及其后代的早期诊断有重要指导意义。     

甲状腺髓样癌患者RET原癌基因突变的研究

目的研究甲状腺髓样癌(MTC)的RET原癌基因突变情况。方法从12例病理诊断的MTC患者和2例临床上怀疑MTC患者提取外周血基因组DNA,对RET原癌基因第10、11、16外显子进行PCR产物直接测序。结果发现8例患者存在基因突变。1例是第10外显子618密码子TGC/CGC突变;2例是第11外显子634密码子TGC/TAC突变;3例是634密码子TGC/CGC突变;2例是第16外显子918密码子ATG/ACG突变。结论直接基因测序分析能在基因水平诊断MTC,分子遗传学分析使术前诊断该疾病成为可能。     

多发性内分泌腺瘤2A型

多发性内分泌腺瘤2型（MEN2）又称Sipple综合征，其病理学特征为甲状腺髓样癌（MTC）或甲状腺C细胞增生。根据不同的临床表现可分为MEN2A、MEN2B、家族性甲状腺髓样癌（FMTC）及其他型。文献报告MEN2A占MEN2的60％，以MTC为主要临床表现，约50％伴有嗜铬细胞瘤（PCC），30％-40％伴有甲状旁腺增生或腺瘤（HPT）。MEN2B以黏膜多发性神经瘤、MTC和（或）PCC为特点，可有类马凡体征，少数患者还伴有肠道神经节母细胞瘤，角膜神经粗大，骨骼发育异常及发育延缓等，无甲状旁腺疾病。FMTC则仅有MTC，且患有MTC的家族成员不少于4个。     

RET原癌基因点突变所致多发性内分泌腺瘤病2B型一例家系研究

目的：研究1例中国家系中RET原癌基因点突变与多发性内分泌腺瘤病2B型（MEN－2B）发病的相互关系及其遗传特征。方法：收集1例MEN－2B患者术后甲状腺髓样癌肿瘤组织和外周血DNA标本及其父母外周血DNA标本运用PCR和逆转录PCR技术以及直接基因测序技术对上述标本中RET原癌基因16号外显子区域进行分子检测。结果：在患者肿瘤组织（c)DNA及其外周血DNA中均检测到RET原癌基因16号外显子918密码子处基因点突变,即：918Met(ATG）→Thr(ACG).且由基因测序图示,该突变为杂合子错义突变。而患者父母外周血DNA样本中均未发现上述RET原癌基因突变。结论：与国外报道相似,在中国MEN－2B患者中,也找到了RET原癌基因16号外显子基因点突变918Met(ATG)→Thr(ACG)。虽然其发病具有遗传倾向,但同样存在散发病例。MEN－2B发病的基因检测应成为该病的诊断治疗以及患者一级亲属早期诊断和临床干预的分子基础。     

RET proto-oncogene mutations are restricted to codons 634 and 918 in mainland Chinese families with MEN2A and MEN2B

OBJECTIVE: Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene, which includes multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). In this paper we present the phenotype-genotype correlation of 20 unrelated Chinese families with 15 cases of MEN2A and five cases of MEN2B. DESIGN: Cross-sectional study. PATIENTS: A total of 147 members from the 20 families were included. Among them, 119 family members were from MEN2A pedigrees (including 15 MEN2A probands) and 28 members from MEN2B pedigrees (including five MEN2B probands). MEASUREMENTS: Genomic DNA was isolated from peripheral blood leucocytes and was amplified using polymerase chain reaction (PCR). DNA analysis for RET mutations in exons 8, 10, 11, 13, 14, 15 and 16 was performed with specific primers. RESULTS: Thirty-seven MEN2A and five MEN2B patients were identified as having RET mutations. The incidence of medullary thyroid carcinoma (MTC), pheochromocytoma (PCC) and hyperparathyroidism (HPT) in the 37 MEN2A patients was 91.9, 56.8 and 10.8%, respectively; the onset of MTC in MEN2A patients was earlier than that of PCC and HPT. Five germline mutations, all located at codon 634 of exon11 in the RET proto-oncogene, were detected in all of the 37 MEN2A patients. The highest frequency of the five germline mutations was C634Y (46.7%), followed by C634R (26.7%), C634W (13.3%), C634F (6.7%) and C634S (6.7%). No statistical significance was found between the incidence of PCC and different genotypes of codon 634 in MEN2A patients, whereas the incidence of HPT was closely associated with C634R and C634Y. The gene mutation (M918T) at exon16 of the RET proto-oncogene was present in five MEN2B probands. CONCLUSIONS: RET proto-oncogene mutations were restricted to codon 634 and 918 in Chinese families with MEN2A and MEN2B. In general the genetic characteristics of these patients with MEN2A and MEN2B reflect the general pattern around the world and it remains to be determined with larger studies in China whether Chinese patients have a different genetic pattern of mutations.     

RET proto-oncogene mutations are restricted to codon 634 and 618 in Korean families with multiple endocrine neoplasia 2A.

Identification of the germline mutation in the RET proto-oncogene is important for the diagnosis of hereditary medullary thyroid carcinoma (MTC). Hereditary forms account for approximately 25%-30% of all cases of MTC. The objective of this study was to evaluate the prevalence of the RET mutation and the genotype-phenotype relation in Korean patients with MTC. Genomic DNAs were obtained from 33 patients with MTC (M:F = 10:23, 39.8 +/- 12.0 years) who underwent total thyroidectomy between 1997 and 2003 at the Samsung Medical Center. Exons 10, 11, 13, 14, 15 and 16 of the RET proto-oncogene were amplified with specific primers using polymerase chain reaction (PCR). Sequence analysis was performed on the polymerase chain reaction (PCR) product using an automatic sequence analyzer. Nine of the 33 patients (M:F = 3:6, 33.3 +/- 10.0 years) were identified as having RET mutations. Six patients had multiple endocrine neoplasia (MEN) 2A and one had familial medullary thyroid carcinoma (FMTC). The remaining two patients were thought to have sporadic MTC. Five of the patients with MEN 2A had RET mutations in codon 634 of exon 11 (3 patients, C634Y; 2 patients, C634R) and the other patient with MEN 2A had a RET mutation in codon 618 of exon 10 (C618R). The patient with FMTC had a mutation in codon 634 (C634W). The two patients with sporadic MTC had RET mutations in codon 634 (1 patient, C634Y; 1 patient, C634S). We were not able to identify any genotype-phenotype relations because of the limited number of patients. Twenty-seven percent (9/33) of the patients with MTC in this study had RET mutations. Taking other studies into account, 77% (10/13) of Korean families with MEN 2A, including 7 other families in three reports from Korea, had RET mutations in codon 634 (5 families, C634Y; 4 families, C634R; 1 family, C634W), and 23% (3/13) had RET mutations in codon 618 (2 families, C618R; 1 family, C618S). RET proto-oncogene mutations were restricted to codon 634 and 618 in Korean families with MEN 2A.     

Polymorphisms in the RET proto-oncogene and the phenotypic presentation of familial medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) occurs in a sporadic or as an autosomal dominant hereditary form. Inherited forms of MTC are related to mutations in the RET proto-oncogene. We screened genomic DNA from 11 patients with MTC for mutations in exons 10, 11, 13, 14, 15, and 16 of the RET proto-oncogene. Subsequently, we also evaluated a family of 1 patient with presumed diagnosis of sporadic MTC. Three patients with MEN2A from two unrelated families presented mutations in exon 11 (C634Y and C634R). A heterozygous mutation in exon 14 (V804M) was identified in the patient with the presumed sporadic MTC. We also observed two different polymorphisms: S904S in exon 15 (2 patients) and L769L in exon 13 (4 patients). The L769L polymorphism has been associated with earlier onset of sporadic MTC. On the other hand, mutations in exon 14 are associated with MTC of later onset and lower aggressiveness. Indeed, the carrier of the V804M mutation associated with L769L polymorphism presented MTC at 32 years of age, in contrast to her asymptomatic mother, who had only the V804M mutation and had MTC diagnosed by fine-needle aspiration biopsy at 60 years of age. In conclusion, the present study confirms the need for genetic screening to differentiate sporadic and hereditary forms of MTC. In addition, the genetic study allows the identification of asymptomatic carriers of hereditary forms of MTC. Finally, we speculated that the L769L polymorphism of the RET proto-oncogene may be related to earlier age of onset in the patient with the V804M mutation.     

New multiple somatic mutations in the RET proto-oncogene associated with a sporadic medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) occurs mostly as a sporadic tumor or in connection with inherited cancer syndromes-multiple endocrine neoplasia (MEN) types 2A and 2B and familial MTC. Germline mutations in the RET proto-oncogene are found in most of the familial cases. Somatic mutations in the RET proto-oncogene are detected in 23%-69% of patients with sporadic MTC. The most frequent somatic mutation is Met918Thr in exon 16 and only a small percentage of mutations in other RET exons have been observed. In a very few cases double mutations were found. Genetic screening for somatic mutations in RET exons 10, 11, 13, 14, 15, and 16 in Czech patients with sporadic MTC was carried out by DNA sequencing. This study presents a new triplesomatic mutation Gly911Asp, Met918Thr, and Glu921Lys in exon 16 of the RET proto-oncogene detected in an 18-year-old Czech male patient. In the second case, a new double-somatic mutation Val591Ile in exon 10 with a concomitant somatic mutation Met918Thr in exon 16 was found in a 77-year-old Czech female patient. These both newly described somatic multiple mutations were revealed in a hemizygous status, the loss of heterozygosity in tumor tissues in comparison with germline DNA was confirmed.     

Penetrance and clinical manifestations of non-hotspot germline RET mutation, C630R, in a family with medullary thyroid carcinoma.

Germline mutations in specific hot spot-codons of the RET proto-oncogene are associated with multiple endocrine neoplasia type 2 (MEN 2). Clinical RET gene testing has been routine for the last 10 years in some countries. In Argentina, RET testing excluding MEN 2B was always reported with a mutation at codon 634, with one exception: we described a novel mutation T > C transition at codon 630 (C630R), the family to which we extend the study in the present report. This family comprised 29 members in four generations including 6 individuals affected with medullary thyroid cancer (MTC), positive for the C630R mutation and normal adrenaline/ noradrenaline and ionized calcium/parathyroid hormone levels. Two asymptomatic mutation carriers aged 5 and 11 years underwent total thyroidectomy. The histopathologic examination showed C-cell hyperplasia and microcarcinoma foci, while preoperative basal calcitonins were normal for both. Our report emphasizes the importance of testing for non-hot spot RET mutations in apparently mutation negative MEN 2 families. Furthermore, it would appear that C630R mirrors C634R in penetrance (100% in this family) and in early age of onset of MTC, although paradoxically, no pheochromocytomas and hyperparathyroidism have developed. In addition to recommending RET testing before 5 years of age; we also can postulate that codon 630 may be the key point along the extracellular domain, important in the tissue-specific penetrance.     

Characterization of RET proto-oncogene C634Y mutation in a Moroccan family with multiple endocrine neoplasia type 2A

Medullary thyroid carcinoma (MTC) is a rare cancer which originates from the calcitonin producing "C" cells of thyroid gland. It presents in as isolated form or as part of the multiple endocrine neoplasia type 2 (MEN 2). The familial form of MTC which frequency remains underestimated, account for 25 to 40% of all MTC presentations. All hereditary forms are transmitted in an autosomal dominant manner and are due to proto-oncogene RET germ line mutations. Although MCT is relatively rare, preclinical or prebiological diagnosis can be achieved with genetic screening with high specificity and sensitivity. Early diagnosis is crucial for disease prevention. In this study we identified the first RET mutation underlying NEM 2A in Morocco. The C634Y mutation was present in the heterozygous state in a Moroccan family with MEN 2A. Genetic screening showed that six asymptomatic members of this family were not C364Y carriers. This report should contribute to the development of genetic screening for NEM 2 and F-MTC in Morocco.     

Double germline mutations in the RET Proto-oncogene in MEN 2A and MEN 2B kindreds.

Medullary thyroid carcinoma (MTC) is a rare form of thyroid cancer representing about 10% of all thyroid malignancies. It occurs mostly as a sporadic tumor or in association with autosomal dominant inherited cancer syndromes--multiple endocrine neoplasia (MEN) types 2A and 2B and familial MTC. Germline mutations in exons 8, 10, 11, 13, 14, 15 and 16 of the RET proto-oncogene are found in most of the familial cases. There are only a few published data reporting multiple germline mutations in the RET proto-oncogene. We have detected double germline mutations in 2 different exons on the same RET allele in two MEN 2 families. In the MEN 2A family, double germline mutation in exons 10 (Cys620Phe) and 13 (Tyr791Phe) was detected. In the MEN 2B family, beside the classical germline mutation in exon 16 (Met918Thr) a second germline mutation in exon 13 (Tyr791Phe) was found. This study revealed that MEN 2 syndromes can also be caused by double germline mutations in the RET proto-oncogene and these families can be added to small worldwide cohort of families with multiple germline mutations.