Interactions between 9-hydroxyellipticine and X rays on mammalian cell survival in vitro

Incubation with 9-hydroxyellipticine (9-OH-E) decreases the survival of X-irradiated CHO cells. The survival decreases in the case of exponentially growing and plateau-phase cells, although cells in exponential phase of growth are more sensitive to the drug alone. Radiosensitivity increases with the drug concentration and whether the cells are incubated with the drug for 1 hr prior to or immediately after irradiation. 9-OH-E inhibits the repair of potentially lethal damage, but recovery from sublethal radiation damage is suppressed only by high drug concentrations. The interaction between 9-OH-E and X-ray damage and repair has been examined. 9-OH-E itself induces DNA single-strand breaks or alkali-labile sites which are repaired by the cells. When drug-incubated cells are X irradiated, a repair-inhibiting action of the drug is observed.