Temozolomide reverses doxorubicin resistance by inhibiting P-glycoprotein in malignant glioma cells

Rong Zhang, Ryuta Saito, Ichiyo Shibahara, Shinichiro Sugiyama, Masayuki Kanamori, Yukihiko Sonoda, Teiji Tominaga

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Temozolomide is a standard chemotherapy agent for malignant gliomas, but the efficacy is still not satisfactory. Therefore, combination chemotherapy using temozolomide with other anti-tumor compounds is now under investigation. Here we studied the mechanism of the synergistic anti-tumor effect achieved by temozolomide and doxorubicin, and elucidated the inhibitory effect of temozolomide on P-glycoprotein (P-gp). Temozolomide significantly enhanced sensitivity to P-gp substrate in glioma cells, particularly in P-gp-overexpressed cells. Synergetic effects, as determined by isobologram analysis, were observed by combining temozolomide and doxorubicin. Subsequently, flow cytometry was utilized to assess the intracellular retention of doxorubicin in cells treated with doxorubicin with or without temozolomide. Temozolomide significantly increased the accumulation of doxorubicin in these cells. The P-gp adenosine triphosphatase (ATPase) assay showed that temozolomide inhibited the ATPase activity of P-gp. In addition, temozolomide combined with doxorubicin significantly prolonged the survival of 9L intracranial allografted glioma-bearing rats compared to single agent treatment. Collectively, our findings suggest that temozolomide can reverse doxorubicin resistance by directly affecting P-gp transport activity. Combination chemotherapy using temozolomide with other agents may be effective against gliomas in clinical applications.

Original languageEnglish
Pages (from-to)235-242
Number of pages8
JournalJournal of Neuro-Oncology
Issue number2
Publication statusPublished - 2016 Jan


  • Brain tumor
  • Chemotherapy
  • Doxorubicin
  • P-glycoprotein
  • Temozolomide

ASJC Scopus subject areas

  • Oncology
  • Neurology
  • Clinical Neurology
  • Cancer Research


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