Topoisomerase I inhibitors, shikonin and topotecan, inhibit growth and induce apoptosis of glioma cells and glioma stem cells

PLoS One. 2013 Nov 26;8(11):e81815. doi: 10.1371/journal.pone.0081815. eCollection 2013.


Gliomas, the most malignant form of brain tumors, contain a small subpopulation of glioma stem cells (GSCs) that are implicated in therapeutic resistance and tumor recurrence. Topoisomerase I inhibitors, shikonin and topotecan, play a crucial role in anti-cancer therapies. After isolated and identified the GSCs from glioma cells successfully, U251, U87, GSCs-U251 and GSCs-U87 cells were administrated with various concentrations of shikonin or topotecan at different time points to seek for the optimal administration concentration and time point. The cell viability, cell cycle and apoptosis were detected using cell counting kit-8 and flow cytometer to observe the inhibitory effects on glioma cells and GSCs. We demonstrated that shikonin and topotecan obviously inhibited proliferation of not only human glioma cells but also GSCs in a dose- and time-dependent manner. According to the IC50 values at 24 h, 2 μmol/L of shikonin and 3 μmol/L of topotecan were selected as the optimal administration concentration. In addition, shikonin and topotecan induced cell cycle arrest in G0/G1 and S phases and promoted apoptosis. The down-regulation of Bcl-2 expression with the activation of caspase 9/3-dependent pathway was involved in the apoptosis process. Therefore, the above results showed that topoisomerase I inhibitors, shikonin and topotecan, inhibited growth and induced apoptosis of GSCs as well as glioma cells, which suggested that they might be the potential anticancer agents targeting gliomas to provide a novel therapeutic strategy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Brain Neoplasms / metabolism*
  • Caspase 3 / metabolism
  • Caspase 9 / metabolism
  • Cell Cycle Checkpoints / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Dose-Response Relationship, Drug
  • Glioma / metabolism*
  • Humans
  • Naphthoquinones / pharmacology*
  • Neoplastic Stem Cells / drug effects*
  • Neoplastic Stem Cells / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Topoisomerase I Inhibitors / pharmacology*
  • Topotecan / pharmacology*


  • Naphthoquinones
  • Proto-Oncogene Proteins c-bcl-2
  • Topoisomerase I Inhibitors
  • shikonin
  • Topotecan
  • Caspase 3
  • Caspase 9

Grant support

This work is supported by grants from the Natural Science Foundation of China (81172197, 81072056, 81171131, 81272564, 81272795), the special fund for Scientific Research of Doctor-degree Subjects in Colleges and Universities (20102104110009), the Natural Science Foundation of Liaoning Province in China (No. 201102300), Liaoning Science and Technology Plan Projects (No. 2011225020), and Shenyang Science and Technology Plan Projects (nos. F11-264-1-15 and F12-277-1-05). The funders of YXX and YHL played a role in study design, data collection and analysis, decision to publish and preparation of the manuscript.