Lack of radiosensitization after paclitaxel treatment of three human carcinoma cell lines

Cancer. 1995 May 1;75(9):2262-8. doi: 10.1002/1097-0142(19950501)75:9<2262::aid-cncr2820750912>;2-5.


Background: Several recent studies have suggested radiosensitizing effects of paclitaxel, a microtubular inhibitor. To test the universality of this finding, the interaction between paclitaxel and radiation treatment of cell lines derived from three common human carcinomas MCF-7 (breast cancer); DUT-145 (prostate cancer); and HT-29 (colon cancer) was evaluated. The study focused on the ability of paclitaxel to block cells at the G2-M phase of the cell cycle and potentially enhance the radiation sensitivity of the cells.

Methods: All cell lines were exposed to three different clinically achievable paclitaxel concentrations ranging from 2 nM to 25 nM. Paclitaxel pretreatment for 12 and 24 hours before radiation was tested in all three cell lines. The radiation dose ranged from 0 to 8 Gy delivered in a single fraction. Cellular survival after treatment with paclitaxel and/or radiation was determined by clonogenic assay. Cell cycle distribution as determined by flow cytometry was performed after various dose-time combinations of paclitaxel.

Results: Cytotoxicity studies with paclitaxel alone demonstrated a time-dependent and dose-dependent survival relationship for all three cell lines. Resultant surviving fractions were in the range of 5 to 90% after 24-hour exposure to paclitaxel alone. The interaction between paclitaxel and radiation was primarily additive in each of the three cell lines for all paclitaxel dose-time combinations studied. Flow cytometric analysis failed to reveal a prominent G2-M block in all three cell lines after paclitaxel treatment for 24 hours.

Conclusions: Paclitaxel lacked a radiosensitizing effect on MCF-7, DUT-145, and HT-29 cells in this study. These results should be considered when designing clinical trials that use paclitaxel as a potential radiosensitizer of certain human carcinomas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / radiotherapy
  • Carcinoma / drug therapy
  • Carcinoma / radiotherapy*
  • Cell Cycle / drug effects
  • Cell Cycle / radiation effects
  • Cell Survival / drug effects
  • Cell Survival / radiation effects
  • Colonic Neoplasms / radiotherapy
  • Dose-Response Relationship, Drug
  • Female
  • Flow Cytometry
  • G2 Phase / drug effects
  • Humans
  • Male
  • Mitosis / drug effects
  • Paclitaxel / administration & dosage
  • Paclitaxel / therapeutic use*
  • Prostatic Neoplasms / radiotherapy
  • Radiation Tolerance / drug effects
  • Radiation-Sensitizing Agents / administration & dosage
  • Radiation-Sensitizing Agents / pharmacology*
  • Radiotherapy Dosage
  • Tumor Cells, Cultured


  • Radiation-Sensitizing Agents
  • Paclitaxel