The radiobiology of human neuroblastoma.

The radiation response of a human neuroblastoma xenograft HX138 has been studied in vitro and in vivo using single cells in suspension, multicellular spheroids, and xenografts in immune-suppressed mice. End-points used were growth delay and clonogenic cell survival. Growth delay experiments with spheroids and xenografts showed a high degree of radioresponsiveness. Cell survival curves obtained from all systems were characterised by the lack of a shoulder. An increase in Do of the cell survival curve was seen after irradiation of intact spheroids and xenografts, perhaps due to the presence of a contact effect. Cellular capacity for split-dose recovery in vitro was modest. Delayed assay experiments using spheroids and xenografts showed some potentially lethal damage (PLD) repair in vitro but not in vivo. The results show this human tumour line to be intrinsically highly radiosensitive, with a limited repair capacity.