In vitro study on the schedule-dependency of the interaction between pemetrexed, gemcitabine and irradiation in non-small cell lung cancer and head and neck cancer cells

BMC Cancer. 2010 Aug 19;10:441. doi: 10.1186/1471-2407-10-441.


Background: Based on their different mechanisms of action, non-overlapping side effects and radiosensitising potential, combining the antimetabolites pemetrexed (multitargeted antifolate, MTA) and gemcitabine (2',2'-difluorodeoxycytidine, dFdC) with irradiation (RT) seems promising. This in vitro study, for the first time, presents the triple combination of MTA, dFdC and irradiation using various treatment schedules.

Methods: The cytotoxicity, radiosensitising potential and cell cycle effect of MTA were investigated in A549 (NSCLC) and CAL-27 (SCCHN) cells. Using simultaneous or sequential exposure schedules, the cytotoxicity and radiosensitising effect of 24 h MTA combined with 1 h or 24 h dFdC were analysed.

Results: Including a time interval between MTA exposure and irradiation seemed favourable to MTA immediately preceding or following radiotherapy. MTA induced a significant S phase accumulation that persisted for more than 8 h after drug removal. Among different MTA/dFdC combinations tested, the highest synergistic interaction was produced by 24 h MTA followed by 1 h dFdC. Combined with irradiation, this schedule showed a clear radiosensitising effect.

Conclusions: Results from our in vitro model suggest that the sequence 24 h MTA --> 1 h dFdC --> RT is the most rational design and would, after confirmation in an in vivo setting, possibly provide the greatest benefit in the clinic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Carcinoma, Non-Small-Cell Lung / therapy*
  • Carcinoma, Squamous Cell / pathology
  • Carcinoma, Squamous Cell / therapy*
  • Cell Cycle / drug effects
  • Cell Cycle / radiation effects
  • Cell Proliferation / drug effects
  • Cell Proliferation / radiation effects
  • Combined Modality Therapy
  • Deoxycytidine / administration & dosage
  • Deoxycytidine / analogs & derivatives
  • Drug Interactions*
  • Drug Synergism
  • Flow Cytometry
  • Glutamates / administration & dosage
  • Guanine / administration & dosage
  • Guanine / analogs & derivatives
  • Head and Neck Neoplasms / pathology
  • Head and Neck Neoplasms / therapy*
  • Humans
  • In Vitro Techniques
  • Lung Neoplasms / pathology
  • Lung Neoplasms / therapy*
  • Pemetrexed
  • Radiotherapy Dosage
  • Tumor Cells, Cultured


  • Glutamates
  • Pemetrexed
  • Deoxycytidine
  • Guanine
  • gemcitabine