Inhibition of repair of bleomycin-induced DNA strand breaks by 2'-deoxycoformycin and its effect on antitumor activity in L5178Y lymphoblasts.

We have observed previously that treatment of plateau-phase L5178Y murine lymphoblasts in vitro with 2'-deoxycoformycin plus deoxyadenosine (dCF/dAdo) can inhibit the repair of X-irradiation-induced DNA single-strand breaks (SSB) in these cells and that this effect is associated with synergistic cell kill. In this study we examined the effect of a combination treatment of plateau-phase L5178Y cells with bleomycin (BLM) plus dCF/dAdo. Incubation of BLM-treated cells with dCF/dAdo resulted in significant inhibition of the repair of BLM-induced DNA SSB. However, an additive, but not a synergistic, increase in cell kill was observed when cells were treated with a combination of BLM plus dCF/dAdo.