[Synergetic radiosensitizing effect of isomers S-8932 and S-8933 in vitro]

The synergetic radiosensitizing effect of isomers S-8932 and S-8933 on HeLa-S3 cell-line was investigated in vitro using cell colony forming assay. The results suggested that the combined use of the two isomers showed a lower cytotoxicity than their single use. The ID50 was 55.3 mM. Their synergetic radiosensitizing effect on HeLa-S3 cells under hypoxic condition was higher than either one used alone. The SER of the combined one at 4mM was 1.98 (D0 ratio) and 1.79 (D9 ratio) indicating a sensitizing effect at both low and high radiation doses. The type of the synergetic radiosensitization of the two compounds indicates that they are radiosensitizers of "alpha-beta" type according to the analysis of their molecular models. If the two isomers are used in combination in fractionation radiotherapy, less number of fraction and larger dose per fraction should be selected in the scheme of treatment.