Mutations in the RET protooncogene in sporadic pheochromocytomas

Abstract

Mutations in the RET proto-oncogene have recently been demonstrated in kindreds with Multiple Endocrine Neoplasia (MEN) types 2A and 2B. Both of these autosomal dominant disorders are characterized by the development of neoplasia in cell lines of neural crest origin, such as medullary throid carcinomas and pheochromocytomas. Individuals with MEN 2B have, in addition, ganglioneuromas of the lips, tongue and colon, a marfanoid habitus, and corneal nerve thickening. Approximately 90% of patients with MEN 2A have a germline mutation in exons 10 or 11, while 95% of patients with MEN 2B have a T{yields}C transition in codon 918 of exon 16. In this study, pheochromocytomas from 29 individuals who had no clinical evidence of MEN 2A or 2B (sporadic) were examined for the presence of either germline or somatic mutations in exons 10, 11, and 16 of the RET proto-oncogene. Of the 29 tumors examined, 3 (10%) were found to have a mutation in one of the three exons. One tumor had a G{yields}A transition in codon 609 (exon 10), another had a 6 bp deletion encompassing codons 632 & 633 (exon 11), and the final tumor had a T{yields}C transition in codon 918 (exon 16). These mutations were notmore » found in the corresponding normal DNA from these individuals, indicating that the mutation were somatic in origin. Although we cannot exclude the possibility of mutations in other regions of the RET proto-oncogene, our data suggests that: (1) individuals presenting with apparently sporadic pheochromocytomas are not likely to have undiagnosed MEN 2A or 2B; and (2) somatic mutations in the RET proto-oncogene contribute to the process of tumorigenesis in a small percentage of sporadic pheochromocytomas.« less