PT - JOURNAL ARTICLE AU - THITITIP TIPPAYAMONTRI AU - RAMI KOTB AU - BENOIT PAQUETTE AU - LÉON SANCHE TI - Synergism in Concomitant Chemoradiotherapy of Cisplatin and Oxaliplatin and their Liposomal Formulation in the Human Colorectal Cancer HCT116 Model DP - 2012 Oct 01 TA - Anticancer Research PG - 4395--4404 VI - 32 IP - 10 4099 - http://ar.iiarjournals.org/content/32/10/4395.short 4100 - http://ar.iiarjournals.org/content/32/10/4395.full SO - Anticancer Res2012 Oct 01; 32 AB - Background: We choose to test the effect of associating chemo-radiotherapy at 8 h (the highest level of DNA-platinum) and 48 h (the lower level of DNA-platinum) to clarify if irradiation at the maximum DNA-platinum concentration could improve the synergism. Materials and Methods: Growth inhibition of the human colorectal cancer cell line HCT116 treated with cisplatin, oxaliplatin, Lipoplatin™ and Lipoxal™ plus gamma-radiation was determined by a colony formation assay. The synergism was evaluated using the combination index method. Results: For 8 h and 48 h exposure to cisplatin or Lipoplatin™, followed by irradiation, drug concentrations higher than IC50 were found to be synergistic, while a lower than IC50 concentration was antagonistic. For oxaliplatin, exposure to a concentration above IC50 for 8 h was synergistic, while the exposure to oxaliplatin (at any concentrations) for 48 h was antagonistic. Lipoxal™ significantly improved synergism compared to its parent drugs. All tested platinum drugs sensitize radiation-treated HCT116 cells by inducing G2 phase. Conclusion: The difference of drug concentrations and the time interval between drug administration and radiotherapy could give different results in chemoradiation therapy.