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Decreased cyclin B1 expression contributes to G2 delay in human brain tumor cells after treatment with camptothecin

A J Janss1, A Maity, C B Tang

  • 1Division of Neurology, Children's Hospital of Philadelphia, PA 19104-9786, USA.

Neuro-Oncology
|April 18, 2001
PubMed

Insights

DNA damage causes a G2/M delay in brain tumor cells, sensitizing them to chemotherapy. This delay is linked to reduced cyclin B1 expression, a key regulator of cell division.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Cycle Regulation

Background:

  • DNA damage induces G2/M delay in proliferating cells, impacting chemotherapy sensitivity.
  • Cyclin-dependent kinase CDC2 activation regulates G2/M transition, but its regulation varies across tumor types.
  • Persistent kinase hyperphosphorylation and reduced cyclin expression are implicated in treatment-induced G2 delay.

Purpose of the Study:

  • To investigate the regulation of G2/M transition in human brain tumors.
  • To evaluate CDC2 kinase and cyclin A/B1 expression and activity in response to camptothecin (CPT) in glioma and medulloblastoma cells.

Main Methods:

  • Synchronized U-251 MG (glioma) and DAOY (medulloblastoma) cells were treated with CPT during S phase.
  • Cell cycle kinetics, kinase activity, mRNA, and protein expression were assessed at predetermined intervals.
  • CDC2 kinase activity, cyclin A and B1 expression, and their association were analyzed.

Main Results:

  • CPT treatment induced G2 delay, characterized by decreased CDC2 kinase activity and cyclin B1 expression.
  • CDC2 kinase activity was primarily associated with cyclin B1, not cyclin A, in both cell lines.
  • Cyclin A mRNA and protein expression showed transient reductions, with varying degrees in glioma and medulloblastoma cells.

Conclusions:

  • G2 delay is a common response of brain tumor cells to topoisomerase I inhibitors like CPT.
  • Reduced cyclin B1 expression is a potential mechanism underlying CPT-induced G2 delay in these cells.
  • Understanding these mechanisms can inform strategies to enhance chemotherapy efficacy in brain tumors.

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