DNA topoisomerase IIalpha and Her-2/neu gene dosages in pediatric malignant gliomas.
Pediatric malignant non-brainstem glioma (PMNBG) is a rare tumor that accounts for only about five percent of childhood intracranial neoplasms. DNA topoisomerase IIalpha (TIIalpha) is a novel marker of cell-cycle turnover and a target of high-risk chemotherapy in PMNBG. We have shown that TIIalpha protein expression strongly correlates with event-free and overall survival in these malignancies. The molecular mechanism causing the varying TIIalpha protein expression in PMNBG remains unknown. Utilizing a combined approach of immunocytochemistry-based morphology guidance, laser-assisted microdissection and quantitative real-time PCR, we report a low-level co-amplification of the neighboring TIIalpha and Her-2/neu gene loci on chromosome 17q11-q22 in one of seventeen examined PMNBGs. Analysis of both genes by real-time PCR in the crude tumor samples without prior tissue heterogeneity reduction via laser microdissection, resulted in loss of detection of amplification of the syngeneic Her-2/neu locus. Gene dosage assessment in a microscopically distant tumor area revealed no amplification of either gene. Our results suggest that low-level amplification of the TIIalpha gene locus may be a sporadic mechanism of increased TIIalpha protein expression in PMNBG, which can coincide with low-level amplification of Her-2/neu. The observed intratumor genetic heterogeneity for TIIalpha in PMNBGs may have an impact on the relevance of TIIalpha as a biological constituent of outcome in these neoplasms.
Bredel
Claudia
C
Department of General Neurosurgery, Neurocenter, University of Freiburg, D-79106 Freiburg, Germany. mbredel@stanford.edu
Lassmann
Silke
S
Pollack
Ian F
IF
Knoth
Rolf
R
Hamilton
Ronald L
RL
Volk
Benedikt
B
Werner
Martin
M
Bredel
Markus
M
D000951:Antigens, Neoplasm / Q000235:genetics*; D001932:Brain Neoplasms / Q000235:genetics*; D002648:Child; D002886:Chromosomes, Human, Pair 17; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005784:Gene Amplification; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D016133:Polymerase Chain Reaction; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*
D000951:Antigens, Neoplasm; D004250:DNA Topoisomerases, Type II; D004268:DNA-Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases