The effect of 2'-2' difluorodeoxycytidine (dFdC, gemcitabine) on radiation-induced cell lethality in two human head and neck squamous carcinoma cell lines differing in intrinsic radiosensitivity

Rosier, Jean-Claude;Beauduin, M.;Bruniaux, M.;De Bast, Marc;Grégoire, Vincent;et.al.
(1999) International Journal of Radiation Biology — Vol. 75, n° 2, p. 245-251 (1999)

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Authors
  • Rosier, Jean-ClaudeUCLouvain
    Author
  • Beauduin, M.
    Author
  • Bruniaux, M.
    Author
  • De Bast, MarcUCLouvain
    Author
  • Scalliet, Pierreorcid-logoUCLouvain
    Author
  • Grégoire, VincentUCLouvain
    Author
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Abstract
PURPOSE: The present study investigated in vitro radio-enhancement by gemcitabine (dFdC) in two head and neck squamous cell carcinomas with different intrinsic cellular radiosensitivity. MATERIALS AND METHODS: Radiosensitive (SCC61, SF2=0.16) and radioresistant (SQD9, SF2=0.49) human head and neck squamous cell carcinomas were used. Confluent cells were incubated with dFdC and irradiated in drug-free medium with a single dose of 250 kV X-rays (0-12Gy). Cell survival curves were corrected for the toxicity of the drug alone. RESULTS: In both cell lines, radio-enhancement was observed with 5 microM dFdC incubated for 3 h prior to irradiation. Dose modification factors (DMF) at a surviving fraction level of 0.5 reached 1.3 (95% CI 1.1-1.6) and 1.5 (95% CI 1.4-1.5) for SQD9 and SCC61 cells, respectively. Radio-enhancement was associated with a modest increase in the alpha term of the linear-quadratic model. In SQD9 cells, radio-enhancement increased with dFdC incubation time. At 24h, DMF reached a value of 1.5 (95% CI 0.9-3.2). In SCC61 cells at 24h, DMF reached a value of 1.1 (95% CI 0.9-1.2). In both cell lines, radio-enhancement increased with dFdC concentration up to 5-10 microM from which values it levelled off up to 100 microM. CONCLUSIONS: The data indicated that dFdC induced a modest radio-enhancement in both cell lines. For a short incubation time, dFdC did not radio-enhance preferentially the more radio-resistant cells, whereas the opposite was observed for a longer time. In both cell lines, radio-enhancement was saturated above a dFdC concentration of 5-10 microM.
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Rosier, J.-C., Beauduin, M., Bruniaux, M., De Bast, M., de Coster, B., Octave-Prignot, M., Scalliet, P., & Grégoire, V. (1999). The effect of 2′-2′ difluorodeoxycytidine (dFdC, gemcitabine) on radiation-induced cell lethality in two human head and neck squamous carcinoma cell lines differing in intrinsic radiosensitivity. International Journal of Radiation Biology, 75(2), 245-251. https://doi.org/10.1080/095530099140708 (Original work published 1999)