The perfluorochemical
emulsion,
Fluosol-DAR, in combination with breathing a 95%
oxygen atmosphere, has been shown to enhance the response of several solid
tumors to
radiation treatment. In this study, the number of macrophages present in two murine
tumors was assessed in the absence of
Fluosol-DA treatment and at various times post-
Fluosol-DA treatment using a rosetting assay. The number of macrophages in the
Lewis lung carcinoma and the FSaII
fibrosarcoma, after an initial decrease, increased nearly 2-fold (at 14 days) after a single
Fluosol-DA injection.
Tumor response was assessed by
tumor growth delay and excisional
tumor cell survival assays in two
tumor systems. Greater dose modifying effects were consistently observed when
tumors remained in situ. Some animals were treated with
carrageenan, a macrophage
poison, prior to implantation of Lewis lung
tumor. Animals treated with
carrageenan,
Fluosol-DA and
carbogen prior to and during X-ray treatment exhibited a dose modifying factor (DMF) of 1.74 +/- 0.08. Animals treated similarly but without
carrageenan pretreatment demonstrated a DMF of 2.61 +/- 0.22.
Fluosol-DA administered 24 hours prior to
carbogen breathing and X-rays resulted in a greater
tumor growth delay than when the perflorochemical was injected immediately prior to radiation/
carbogen treatment. The relatively nonimmunogenic FSaII
tumor/C3H/Sed host system gave similar results but instead of dose modification, parallel displacements in the dose response curves were seen. Again,
Fluosol-DA administrated 24 hours prior to radiation was more effective in sensitizing the
tumor than immediate administration. These results suggest that
Fluosol-DA in addition to functioning as an
oxygen-carrier produces a nonspecific activation of the immune system.