Temozolomide competes for P-glycoprotein and contributes to chemoresistance in glioblastoma cells

Jessian L. Munoz, Nykia D. Walker, Kathleen W. Scotto, Pranela Rameshwar

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


Chemotherapeutic resistance can occur by P-glycoprotein (P-gp), a 12-transmembrane ATP-dependent drug efflux pump. Glioblastoma (GBM) has poor survival rate and uniformly acquired chemoresistance to its frontline agent, Temozolomide (TMZ). Despite much effort, overcoming TMZ resistance remains a challenge. We reported on autonomous induction of TMZ resistance by increased transcription MDR1, the gene for P-gp. This study investigated how P-gp and TMZ interact to gain resistance. Using an experimental model of Adriamycin-resistant DC3F cells (DC3F/Adx), we showed that increased P-gp caused TMZ resistance. Increasing concentrations of TMZ competed with Calcein for P-gp, resulting in reduced efflux in the DC3F/Adx cells. Three different inhibitors of P-gp reversed the resistance to TMZ in two different GBM cell lines, by increasing active Caspase 3. Molecular modeling predicted the binding sites to be the intracellular region of P-gp and also identified specific amino acids and kinetics of energy for the efflux of TMZ. Taken together, we confirmed P-gp targeting of TMZ, a crucial regulator of TMZ resistance in GBM. This study provides insights on the effectiveness by which TMZ competes with other P-gp substrates, thereby opening the door for combined targeted therapies.

Original languageEnglish (US)
Pages (from-to)69-75
Number of pages7
JournalCancer Letters
Issue number1
StatePublished - Oct 10 2015
Externally publishedYes


  • Chemoresistance
  • Glioblastoma
  • MDR1
  • P-gp
  • Temozolomide

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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