The radiation dose-rate effect in two human neuroblastoma cell lines.

The current use of targeted radiotherapy in the treatment of neuroblastoma has generated a requirement for further information on the radiobiology of these cells. Here we report on studies of the dose-rate effect in two human neuroblastoma cell lines (HX138 and HX142) and the recovery that they demonstrate in split-dose experiments. The sensitivity of the two cell lines to high dose-rate irradiation was confirmed. Surviving fractions at 2 Gy were 0.083 for HX138 and 0.11 for HX142. There was little evidence of a dose-rate effect above 2 cGy min-1 but significant sparing was seen at lower dose rates. Substantial recovery was seen in split-dose experiments on both cell lines, to an extent that was consistent with the linear quadratic equation. The data were used to derive values for the beta parameter of the linear-quadratic equation; the values for the neuroblastomas were higher than for any of the other human tumour cell lines that we have investigated to date. Thus, despite their high sensitivity to ionising radiation HX138 and HX142 do exhibit substantial levels of cellular recovery, suggesting that they may have a significant capacity for repair of radiation-induced lesions.