Huang C N, Wu S L, Chang T C, Huang S H, Chang T J
Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
J Formos Med Assoc. 1998 Aug;97(8):541-6.
We examined RET protooncogene mutations in sporadic medullary thyroid carcinoma (MTC), using polymerase chain reaction (PCR)-based sequencing. DNA was extracted from tumor tissue and peripheral blood leukocytes of seven unrelated individuals with apparently sporadic MTC. Oligonucleotide primers were selected to amplify exons 10, 11, 13, 15, and 16 of the RET protooncogene, to examine the sequences of codons 609, 611, 618, and 620 of exon 10, codon 634 of exon 11, codon 768 of exon 13, codon 883 of exon 15, and codon 918 of exon 16. Direct DNA sequencing from PCR products was then performed. The results showed that one patient had a somatic mutation at codon 918 (ATG-->ACG), causing a Met-->Thr substitution. One patient had a de novo germline mutation at codon 634 (TGC-->CGC), causing a Cys-->Arg substitution. Another patient had a germline mutation at codon 634 (TGC-->TTC), causing a Cys-->Phe substitution. In the remaining four cases, no RET mutations were found. Unexpectedly, two offspring of the patient (a female) with a germline mutation at codon 634 (TGC-->TTC) harbored homozygous alleles for the mutation; because the father did not carry this mutation, the other affected allele was suspected to have resulted from a de novo germline mutation of paternal origin. One of these offspring was subsequently diagnosed as having MTC. Our findings suggest that all patients with apparently sporadic MTC should be screened for the RET protooncogene by molecular analysis to detect occult or de novo multiple endocrine neoplasia 2 (MEN 2) or familial MTC. This would allow early treatment of affected family members.
我们采用基于聚合酶链反应（PCR）的测序方法，检测散发性甲状腺髓样癌（MTC）中的RET原癌基因突变情况。从7名明显为散发性MTC的无关个体的肿瘤组织和外周血白细胞中提取DNA。选择寡核苷酸引物扩增RET原癌基因的第10、11、13、15和16外显子，以检测第10外显子密码子609、611、618和620、第11外显子密码子634、第13外显子密码子768、第15外显子密码子883以及第16外显子密码子918的序列。然后对PCR产物进行直接DNA测序。结果显示，1例患者在密码子918处发生体细胞突变（ATG→ACG），导致甲硫氨酸（Met）替换为苏氨酸（Thr）。1例患者在密码子634处发生新生胚系突变（TGC→CGC），导致半胱氨酸（Cys）替换为精氨酸（Arg）。另1例患者在密码子634处发生胚系突变（TGC→TTC），导致半胱氨酸（Cys）替换为苯丙氨酸（Phe）。在其余4例中，未发现RET突变。出乎意料的是，密码子634（TGC→TTC）发生胚系突变的患者（一名女性）的2名后代携带该突变的纯合等位基因；由于父亲未携带此突变，怀疑另一个受影响的等位基因来自父源新生胚系突变。其中1名后代随后被诊断为患有MTC。我们的研究结果表明，所有明显为散发性MTC的患者都应通过分子分析筛查RET原癌基因，以检测隐匿性或新生的多发性内分泌肿瘤2型（MEN 2）或家族性MTC。这将有助于对受影响的家庭成员进行早期治疗。
