Sequence-dependent cytotoxicity of etoposide and paclitaxel in human breast and lung cancer cell lines

Edith A. Perez, Christopher A. Buckwalter

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Purpose: To evaluate the effect of schedule on the interaction of etoposide with paclitaxel in vitro against the A549 human lung cancer cell line and the MDA-231 and MCF-7 human breast cancer cell lines. Methods: Exposure schedules that were 24-h concurrent, 24-h sequential, and sequential 24-h with a 24-h intervening drug-free period were quantitatively evaluated by the use of the median-effect principle and the combination index. The clonogenic assay was used to assess cytotoxicity, and calculations were done with computer software. Results: Concurrent exposures were less than additive in two of the three cell lines tested. Sequential 24-hour and sequential 24-h with an intervening 24-h drug-free period showed synergism at high effect levels in all three cell lines. Similar synergistic interactions were found when either agent was administered first. Conlusions: These results show a schedule-dependent cytotoxic interaction between etoposide and paclitaxel in the human lung and breast cancer cell lines evaluated, with optimal synergism occurring with sequential, but not with concurrent, treatment.

Original languageEnglish (US)
Pages (from-to)448-452
Number of pages5
JournalCancer chemotherapy and pharmacology
Issue number6
StatePublished - Apr 8 1998


  • Breast
  • Cell culture
  • Etoposide
  • Lung
  • Paclitaxel

ASJC Scopus subject areas

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


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