DNA topoisomerase IIalpha and Her-2/neu gene dosages in pediatric malignant gliomas

Int J Oncol. 2005 May;26(5):1187-92.

Abstract

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.

MeSH terms

  • Antigens, Neoplasm / genetics*
  • Brain Neoplasms / genetics*
  • Child
  • Chromosomes, Human, Pair 17*
  • DNA Topoisomerases, Type II / genetics*
  • DNA-Binding Proteins / genetics*
  • Gene Amplification*
  • Gene Dosage*
  • Gene Expression Regulation, Neoplastic*
  • Glioma / genetics*
  • Humans
  • Immunohistochemistry
  • Polymerase Chain Reaction
  • Receptor, ErbB-2 / genetics*

Substances

  • Antigens, Neoplasm
  • DNA-Binding Proteins
  • Receptor, ErbB-2
  • DNA Topoisomerases, Type II