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.     

15个多发性内分泌腺瘤2A型家系的临床和RET基因突变研究

目的 研究15例多发性内分泌腺瘤2A型（MEN2A）先证者及其家系成员的临床表型和RET原癌基因突变情况。方法 收集15例MEN2A先证者家系的共119名家系成员,提取其外周血基因组DNA,分别对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 在15个MEN2A家系中,共有49例检出RET原癌基因突变。其中37例有MEN2A临床表型,另12例为基因携带者,前者诊断MEN2A的年龄显著晚于后者[（43．0±13．9）岁比（9．8±7．4）岁,P〈0．01];37例MEN2A患者中甲状腺髓样癌（MTC）、嗜铬细胞瘤（PCC）和甲状旁腺增生或腺瘤（HPT）的发生率分别为91．9％,56．8％和10．8％;在15个MEN2A家系中,共检出5种基因突变类型,均位于RET原癌基因第11外显子634位点,分别为：C634W（13．3％）,C634Y（46．7％）,C634R（26．7％）,C634F（6．7％）,C634S（6．7％）。结论 15个MEN2A家系中,37例有临床表型的MEN2A患者平均确诊年龄高于国外相关报道;MEN2A患者MTC和PCC的发病率和国外文献报道的基本一致,而HPT则较低;所有MEN2A患者的RET原癌基因突变均位于634位点,较国外文献报道的单一。     

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。     

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。     

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。     

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。     

多发性内分泌腺瘤病

多发性内分泌腺瘤病分为1型(MEN1)和2型(MEN2),其中MEN2又可分为MEN2A和MEN2B。MEN1主要临床表现为甲状旁腺腺瘤、胃肠胰肿瘤(以胃泌素瘤和胰岛素瘤常见)和垂体前叶瘤(以泌乳素瘤常见)。MEN2A主要表现为甲状腺髓样癌、嗜铬细胞瘤和甲状旁腺增生,MEN2B为甲状腺髓样癌、黏膜神经纤维瘤和嗜铬细胞瘤。1997年,美国国立卫生研究院(NIH)和欧洲MEN1研究联合体(ECMEN1)成功地克隆到MEN1的致病基因men1[1-2]。之后,在绝大部分MEN1家系病人中都发现了该基因的突变,从而确定了men1基因与MEN1之间的因果关系。MEN2由原癌基因ret突…     

多发性内分泌腺瘤病

多发性内分泌腺瘤病分为1型（MEN1）和2型（MEN2），其中MEN2又可分为MEN2A和MEN2B。MEN1主要临床表现为甲状旁腺腺瘤、胃肠胰肿瘤（以胃泌素瘤和胰岛素瘤常见）和垂体前叶瘤（以泌乳素瘤常见）。MEN2A主要表现为甲状腺髓样癌、嗜铬细胞瘤和甲状旁腺增生，MEN2B为甲状腺髓样癌、黏膜神经纤维瘤和嗜铬细胞瘤。1997年，美国国立卫生研究院（NIH）和欧洲MEN1研究联合体（ECMEN1）成功地克隆到MEN1的致病基因men1。之后，在绝大部分MEN1家系病人中都发现了该基因的突变，从而确定了men1基因与MEN1之间的因果关系。MEN2由原癌基因ret突变所致，大量的病例显示，临床表型与ret基因突变类型之间有很好的相关性。     

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。     

一个Ⅱa型多内分泌腺瘤病家系的RET原癌基因突变研究

目的 检测一个Ⅱa型多内分泌腺瘤（MEN-Ⅱa)病家系中RET原癌基因的突变情况。方法 提取9名家系成员外周血基因组DNA，对RET原癌基因第10和第11外显子进行聚合酶链反应（PCR），PCR产物进行直接DNA测序。结果 家系中2例经病理确诊的患者存在RET原癌基因第11外显子Cys(TGC)634Gly(GGC)错义突变，另筛查出4名成员为该突变基因携带者，其中2例经B超检查发现甲状腺有新生物，1例双侧甲状腺及双侧肾上腺有新生物。1例15岁的突变基因携带者无临床表现。结论 对MEN-Ⅱa家系的基因分析证实RET原癌基因第11外显子在密码子634存在TGC→GGC突变，对MEN-Ⅱa能在基因水平作出诊断，对MEN-Ⅱa家系成员作分子遗传学分析有助于判断患MEN-Ⅱa的危险性和临床上作进一步处理。     

Cancers connected with mutations in RET proto-oncogene

Germline mutations of RET proto-oncogene are connected with inherited cancer syndrome multiple endocrine neoplasia type 2. The syndrome is characterized by incidence of medullary thyroid carcinoma frequently associated with pheochromocytoma and hyperparathyroidism. Genetic testing of family members at risk significantly contributed to diagnosis and management of MEN 2. Early genetic screening for RET mutations allow to detect people who have inherited the MEN2 specific RET mutation with subsequent possibility to of prophylactic thyroidectomy. On the other hand those family members at risk of MEN 2 who had not inherited the mutation do not require further testing. The involvement of RET proto-oncogene in tumorigenesis is reviewed.     

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.     

The RET proto-oncogene and cancer

Abstract. The RET proto-oncogene, a receptor tyrosine kinase, has been evaluated as a candidate gene for multiple endocrine neoplasia type 2A and type 2B (MEN 2A and MEN 2B), for familial medullary thyroid carcinoma (FMTC), and for sporadic cases of medullary thyroid carcinoma (MTC) and pheochromocytomas. We determined the genomic structure of RET and used single-strand conformational polymorphism (SSCP) analysis to identify sequence variants in genomic DNA from families segregating MEN 2 and FMTC. In addition, we examined paired tumour and lymphocyte genomic DNAs from individuals with sporadic cases of MTC and pheochromocytoma. Altogether, we and others found 21 missense mutations in five cysteines clustered in the extra cellular domain of RET (exons 10 and 11) associated with 111 MEN 2 A and FMTC families. In contrast, a single point mutation that results in the substitution of threonine for methionine within the catalytic core of the tyrosine kinase domain (codon 918, exon 16) is responsible for all 66 reported cases of MEN 2B. Two missense mutations and a six base-pair deletion were identified in MTC tumour DNA, but no mutations were identified from pheochromocytoma tumour DNAs. A predictive DNA test for MEN 2A-associated mutations in RET has been developed that is based on detection of missense mutations by polymerase chain reaction (PCR) amplification and restriction endonuclease cleavage. A dominant oncogene model for the action of the RET gene product is proposed as a mechanism of action in MEN 2A, MEN 2B, FMTC and for at least some cases of sporadic MTC.     

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.     

Clinical characteristics and genetic screening of an extended family with MEN2A

MEN-2A is characterized by medullary thyroid carcinoma (MTC) with pheochromocytoma and sometimes parathyroid adenoma. In affected members of the family, the risk of MTC is about 100%. Biochemical screening allows tumors to be detected early but even at this stage treatment is not always curative. Missense mutations in exon 10 and 11 of the RET proto-oncogene are associated with MEN-2A. Early detection of this mutation by DNA analysis allows the identification of the carriers of the gene. We performed genetic screening in 88 members of an extended family with MEN-2A and found 18 members positive for RET mutation (Cys634Gly). Only three of these 18 RET positive cases had a previous diagnosis of medullary cancer and/or pheochromocytoma. Up to now, 12 of the RET positive cases have undergone thyroidectomy. There was extended disease with cervical lymph node metastasis in 6 of them, bilateral medullary microcancer in 3 and c-cell hyperplasia in the remaining 3. Three of the 18 RET positive patients had also pheochromocytoma. Primary hyperparathyroidism was present in only one patient. The mean age of diagnosis of medullary cancer was between 25-50 yr and mean age of death was between 35-95 yr in affected members of the family. The family had many other affected members in other cities in Turkey and in other countries throughout the world from Australia to the Netherlands. So this family is perhaps one of the most extended families with MEN-2A.     

A novel Val648Ile substitution in RET protooncogene observed in a Cys634Arg multiple endocrine neoplasia type 2A kindred presenting with an adrenocorticotropin-producing pheochromocytoma

Multiple endocrine neoplasia type 2 (MEN 2) comprises a heterogeneous group of neoplasic disorders that most commonly have a single missense substitution of the RET protooncogene (RET) involving exons 10 and 11. It was previously reported a MEN 2A kindred in which the father presented with a rare phenotype consisting of bilateral ACTH-producing pheochromocytoma and medullary thyroid carcinoma. We recently performed mutational analysis of the father and his 4 children using a denaturing gradient gel electrophoresis approach and PCR-amplified genomic DNA, followed by direct sequencing or restriction fragment length polymorphism testing. All 4 children showed a RET sequence variation. The common exon 11 Cys(634)Arg RET mutation was present in 2 of the 4 children who had undergone thyroidectomy for C cell disease. The remaining 2 children, who did not harbor the Cys(634)Arg mutation and are negative for C cell and adrenal disease, carry a previously unreported Val(648)Ile missense change in RET exon 11. This novel substitution was not found in the unaffected mother or in 200 control alleles. Both RET variants were present in the father affected with MEN 2A and the unusual ACTH-producing pheochromocytoma. We speculate that the double RET mutation may have modified and contributed to the rare MEN 2A phenotype in the father.     

Pheochromocytoma and medullary thyroid carcinoma: a new genotype-phenotype correlation of the RET protooncogene 891 germline mutation

Prior experience in kindreds with a codon 891 RET protooncogene mutation indicates that carriers of this mutation develop only hereditary medullary thyroid carcinoma without evidence of other manifestations of multiple endocrine neoplasia type 2. In this paper, we report the first documented case in which medullary thyroid carcinoma and pheochromocytoma were clinically expressed in members of a family affected by the codon 891 RET mutation. Genetic analysis of the RET protooncogene in this family revealed an exon 15 missense mutation at codon 891 that resulted in a serine to alanine amino acid substitution. These findings indicate that patients with this mutation should be screened for pheochromocytoma.