title: High frequency of mitochondrial DNA mutations in glioblastoma multiforme identified by direct sequence comparison to blood samples.
abstract: In an earlier study, we showed that heteroplasmy in the mitochondrial genome of gliomas sometimes occurs in a D-loop polycytosine tract. We extended this study by pairwise comparisons between glioma samples and adjacent brain tissue of 55 patients (50 glioblastomas, 1 astrocytoma WHO grade III, 4 astrocytomas WHO grade II). We used a combination of laser microdissection and PCR to detect and quantify variations in the polycytosine tract. New length variants undetectable in the adjacent brain tissue were observed in 5 glioblastomas (9%). In 2 of these cases, samples from a lower tumor stage (WHO grade II) could be analyzed and revealed the early occurrence of these mutations in both cases. Since the mitochondrial D-loop contains additional repeats and highly polymorphic non-coding sequences, we compared 17 glioblastomas with the corresponding blood samples of the same patients by direct sequencing of the complete D-loop. In 6 of these tumors (35%), instability was detected in 1 or 2 of 3 repeat regions; in 1 of these repeats, the instability was linked to a germline T-to-C transition. Furthermore, of 2 tumors (12%) 1 carried 1 and the other 9 additional transitions. In the latter patient, 6.7 kb of the protein coding mtDNA sequence were analyzed. Six silent transitions and 2 missense mutations (transitions) were found. All base substitutions appeared to be homoplasmic upon sequencing, and 89% occurred at known polymorphic sites in humans. Our data suggest that the same mechanisms that generate inherited mtDNA polymorphisms are strongly enhanced in gliomas and produce somatic mutations.
authors.affiliation: Department of Neuropathology, University of Magdeburg, Magdeburg, Germany. elmar.kirches@medizin.uni-magdeburg.de
authors.forename: E
authors.initials: E
authors.lastname: Kirches
authors.forename: G
authors.initials: G
authors.lastname: Krause
authors.forename: M
authors.initials: M
authors.lastname: Warich-Kirches
authors.forename: S
authors.initials: S
authors.lastname: Weis
authors.forename: T
authors.initials: T
authors.lastname: Schneider
authors.forename: B
authors.initials: B
authors.lastname: Meyer-Puttlitz
authors.forename: C
authors.initials: C
authors.lastname: Mawrin
authors.forename: K
authors.initials: K
authors.lastname: Dietzmann
mesh_terms: D000328:Adult; D000368:Aged; D001483:Base Sequence; D001932:Brain Neoplasms / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000097:blood / Q000235:genetics*; D005260:Female; D005909:Glioblastoma / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D020125:Mutation, Missense; D009690:Nucleic Acid Conformation; D016612:Paraffin Embedding; D011066:Poly C / Q000235:genetics
chemical_list: D004272:DNA, Mitochondrial; D011066:Poly C