title: Mutations in the SDHB gene are associated with extra-adrenal and/or malignant phaeochromocytomas.
abstract: Germ-line mutations in the genes encoding succinate dehydrogenase complex subunits B (SDHB) and D (SDHD) have been reported in familial paragangliomas and apparently sporadic phaeochromocytomas (ASP), but the genotype-phenotype relationships of these mutations are unknown. Eighty-four patients (all but 2 followed up for 8.8 +/- 5.7 years) with ASP (57 with adrenal tumors, 27 with extra-adrenal, multiple, malignant, or recurrent tumors) were screened for the major susceptibility genes for phaeochromocytoma (RET, VHL, SDHD, and SDHB). Thirty-three tumors were available for molecular analysis, enzyme assays, and immunohistochemistry. No (0%) RET and 2 (2.4%) VHL mutations were detected. Only two coding single nucleotide polymorphisms in the SDHD gene (G12S and H50R) were found in 6 patients (7%). Conversely, six deleterious mutations in the SDHB gene were identified in 8 patients (9.5%). Ectopic site and recurrence or malignancy were strongly associated with SDHB mutations (7 of 8, 87%, versus 20 of 76, 26%; P = 0.001). Somatic DNA analysis indicated a loss of heterozygosity at chromosome 1p36 (SDHB locus) in 16 of 33 cases (48%). A loss of heterozygosity at the SDHB locus was found in all tumors with SDHB mutation, and assays of respiratory chain enzymes showed a complete loss of complex II catalytic activity. The vascular architecture of tumors with SDHB mutations displayed features typical of malignancy. These data strongly suggest that SDHB gene is a tumor suppressor gene and that the identification of germ-line mutations in SDHB gene in patients with ASPs should be considered as a high-risk factor for malignancy or recurrence.
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000098:blood supply / Q000201:enzymology / Q000235:genetics*; D000328:Adult; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D018095:Germ-Line Mutation; D006801:Humans; D007506:Iron-Sulfur Proteins; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D010673:Pheochromocytoma / Q000098:blood supply / Q000201:enzymology / Q000235:genetics*; D021122:Protein Subunits / Q000235:genetics*; D013385:Succinate Dehydrogenase / Q000235:genetics*; D001749:Urinary Bladder Neoplasms / Q000098:blood supply / Q000201:enzymology / Q000235:genetics
chemical_list: D004273:DNA, Neoplasm; D007506:Iron-Sulfur Proteins; D021122:Protein Subunits; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase