Characterization of the somatic mutational spectrum of the neurofibromatosis type 1 (NF1) gene in neurofibromatosis patients with benign and malignant tumors.
One of the main features of neurofibromatosis type 1 (NF1) is benign neurofibromas, 10-20% of which become transformed into malignant peripheral nerve sheath tumors (MPNSTs). The molecular basis of NF1 tumorigenesis is, however, still unclear. Ninety-one tumors from 31 NF1 patients were screened for gross changes in the NF1 gene using microsatellite/restriction fragment length polymorphism (RFLP) markers; loss of heterozygosity (LOH) was found in 17 out of 91 (19%) tumors (including two out of seven MPNSTs). Denaturing high performance liquid chromatography (DHPLC) was then used to screen 43 LOH-negative and 10 LOH-positive tumors for NF1 microlesions at both RNA and DNA levels. Thirteen germline and 12 somatic mutations were identified, of which three germline (IVS7-2A>G, 3731delT, 6117delG) and eight somatic (1888delG, 4374-4375delCC, R2129S, 2088delG, 2341del18, IVS27b-5C>T, 4083insT, Q519P) were novel. A mosaic mutation (R2429X) was also identified in a neurofibroma by DHPLC analysis and cloning/sequencing. The observed somatic and germline mutational spectra were similar in terms of mutation type, relative frequency of occurrence, and putative underlying mechanisms of mutagenesis. Tumors lacking mutations were screened for NF1 gene promoter hypermethylation but none were found. Microsatellite instability (MSI) analysis revealed MSI in five out of 11 MPNSTs as compared to none out of 70 neurofibromas (p=1.8 x 10(-5)). The screening of seven MPNSTs for subtle mutations in the CDKN2A and TP53 genes proved negative, although the screening of 11 MPNSTs detected LOH involving either the TP53 or the CDKN2A gene in a total of four tumors. These findings are consistent with the view that NF1 tumorigenesis is a complex multistep process involving a variety of different types of genetic defect at multiple loci.
Upadhyaya
Meena
M
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Han
Song
S
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Consoli
Claudia
C
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Majounie
Elisa
E
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Horan
Martin
M
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Thomas
Nick S
NS
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Potts
Christopher
C
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Griffiths
Sian
S
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
Ruggieri
Martino
M
Institute of Bioimaging and Pathology of the Central Nervous System, National Research Council, Catania, Italy.
von Deimling
Andreas
A
Institut für Neuropathologie, Charité, Humboldt-Universität, Berlin, Germany.
Cooper
David N
DN
Institute of Medical Genetics, University of Wales College of Medicine, Cardiff, UK.
D000483:Alleles; D001254:Astrocytoma / Q000235:genetics*; D016543:Central Nervous System Neoplasms / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods; D004273:DNA, Neoplasm / Q000235:genetics; D016514:Genes, Neurofibromatosis 1; D019942:Genes, p16; D016158:Genes, p53 / Q000235:genetics; D015894:Genome, Human; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D019656:Loss of Heterozygosity / Q000235:genetics; D008214:Lymphocytes / Q000737:chemistry; D009154:Mutation / Q000235:genetics*; D018317:Nerve Sheath Neoplasms / Q000235:genetics; D009455:Neurofibroma / Q000235:genetics*; D009456:Neurofibromatosis 1 / Q000235:genetics*; D025542:Neurofibromin 1 / Q000235:genetics; D011230:Precancerous Conditions / Q000235:genetics; D011544:Pseudogenes / Q000235:genetics; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
D004273:DNA, Neoplasm; D025542:Neurofibromin 1