One method to make hypoxic, radioresistant cells more radiation sensitive has been to increase the
oxygen carrying capacity of normal blood using liquid perfluorochemical
emulsions combined with breathing high pO2
gases. We investigated the ability of
dodecafluoropentane (DDFP) to sensitize the moderately radiation-resistant Morris 7777
hepatoma based on our previous inability to modify the radiation response of this
tumor. DDFP is used in very small quantities compared with perfluorchemicals reported previously. Rats under
isoflurane anesthesia were administered EF5 3 h before irradiation to monitor the pretreatment level of tissue
hypoxia. At -40 min, DDFP was administered i.v. at 3.5 ml/kg over 30 min.
At -10 min, the rats were either continued with air (for controls) or switched to
carbogen. The
tumors were then irradiated and processed for evaluation of radiation response.
Tumor-cell survival for DDFP treatment with air-breathing animals was not significantly different from controls treated without DDFP.
Carbogen alone provided minimal sensitization. DDFP plus
carbogen caused dramatic radiosensitization, and the radiation response of cells from these
tumors was the same as a completely aerobic radiation response. DDFP plus
carbogen appears to completely reverse the hypoxic cell radioresistance in this
tumor model.