Positive interaction between interferon and bleomycin in vitro and in animal experimental models.

Effect of combined bleomycin and interferon on cell growth was evaluated in vitro, on 2 leukemia cell lines, and on mice bearing a murine leukemia. Human alpha-A interferon or murine alpha-beta interferon were used. Synergism was observed in both models and the sequence of administration was decisive in this respect. The in vivo results were not completely comparable with those observed in vitro. This finding suggests that the in vitro results reflect the direct effects of the drugs on tumor cells, meanwhile the interaction between drugs in vivo are affected by pharmacokinetic characteristics and by host defense systems.