GERM-LINE MUTATIONS OF THE RET PROTOONCOGENE IN JAPANESE PATIENTS WITH MULTIPLE ENDOCRINE NEOPLASIA TYPE 2A AND TYPE 2B

We investigated mutations of the ret proto-oncogene in Japanese patien ts with multiple endocrine neoplasia (MEN) type 2A and type 2B. DNAs f rom pheochromocytomas and/or medullary thyroid carcinomas (MTCs) of fi ve MEN 2A and three MEN 2B patients were amplified by a polymerase cha in reaction (PCR) and analyzed. Tumors of four MEN 2A patients had mis sense mutations in Cys 634 in the extracellular domain of the ret prot o-oncogene. The same mutations were detected in normal tissues of the patients, indicating that the mutations had arisen in the germ line. U sing a reverse transcriptase(RT)-PCR, both normal and mutant transcrip ts of the ret proto-oncogene were detected in a tumor of one patient w ith MEN 2A mutation. In addition, three MEN 2B patients examined had t he same point mutation (ATG-->ACG) at codon 918 in the tyrosine kinase domain of the ret proto-oncogene. Since all mutations identified in t his study generated new restriction enzyme sites or eliminated a restr iction site, the mutant alleles of affected family members could be re adily detected without sequencing.