Sequential topoisomerase targeting and analysis of mechanisms of resistance to topotecan in patients with acute myelogenous leukemia

Biren Saraiya, Murugesan Gounder, Jayeeta Dutta, Ahamed Saleem, Celeste Collazo, Luz Zimmerman, Ahamed Nazar, Mecide Gharibo, Dale Schaar, Yong Lin, Weichung Shin, Joseph Aisner, Roger Strair, Eric H. Rubin

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Resistance to topoisomerase I (TOP1)-targeting drugs such as topotecan often involves upregulation of topoisomerase II (TOP2), with accompanying increased sensitivity to TOP2-targeting drugs such as etoposide. This trial was designed to investigate sequential topoisomerase targeting in the treatment of patients with high-risk acute myelogenous leukemia. An initial cohort of patients received topotecan and cytosine arabinoside daily for 5 days. Serial samples of circulating mononuclear cells were examined to evaluate peak elevations of TOP2-α protein expression. In subsequent cohorts, etoposide was administered daily for 3 days, beginning 6 h after initiation of the topotecan infusion. The etoposide dose was escalated to determine a maximum-tolerated dose. Circulating mononuclear cells were analyzed for TOP1 mutations and ABCG2 protein expression. In addition, systemic and intracellular topotecan concentrations were measured. Thirty-one patients were enrolled. On the basis of TOP1-α protein levels in three patients with peripheral blast counts greater than 50%, etoposide administration began 6 h after initiation of the topotecan/cytosine arabinoside infusion. Using this schedule of administration, the maximum-tolerated dose of etoposide was 90mg/m2. No TOP1 mutations were identified, but increases in ABCG2 expression during the infusion were observed in mononuclear cells from two of four evaluable patients. Administration of etoposide 6 h after initiation of a topotecan/cytosine arabinoside infusion is feasible and is associated with clinical activity. Analysis of TOP2-α protein levels in this small number of patients indicated that peak increases occurred earlier than expected based on earlier publications. Upregulation of ABCG2 was detected in circulating cells and may represent an inducible form of drug resistance that should be investigated further.

Original languageEnglish (US)
Pages (from-to)411-420
Number of pages10
JournalAnti-Cancer Drugs
Issue number4
StatePublished - Apr 2008

All Science Journal Classification (ASJC) codes

  • Oncology
  • Pharmacology
  • Pharmacology (medical)
  • Cancer Research


  • ABCG2
  • Efflux protein
  • Leukemia
  • Phase i clinical trial
  • Topoisomerase
  • Topotecan

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