MUTATION OF RET PROTOONCOGENE IN JAPANESE PATIENTS WITH MULTIPLE ENDOCRINE NEOPLASIA TYPE 2B AND SPORADIC MEDULLARY-THYROID CARCINOMA

To determine whether patients with medullary thyroid carcinoma (MTC) d evelop other endocrine neoplasms or their relatives develop MTC, we in vestigated the mutations in the RET protooncogene in patients with mul tiple endocrine neoplasia type 2B (MEN 2B, N=1) and sporadic MTC (N=6) . DNA from MTC tissue and the peripheral blood was screened by polymer ase chain reaction single-strand conformational polymorphism (PCR-SSCP ) analysis of exons 10 and 11. PCR products of exons 13 and 16 were al so analyzed by AluI and FokI restriction enzyme digestion methods, res pectively, and then sequenced. We did not find structural abnormalitie s in exon 10 or 11, or at codon 768 in exon 13, but a mutation at codo n 918, ATG to ACG, was found in the peripheral blood and the MTC tissu e from a patient with MEN 2B. The same mutation was also found in tumo r tissue from 2 of 6 patients with sporadic MTC, but not in their peri pheral blood.