Experimental combination chemotherapy of ACNU and 5-FU against cultured glioma model (spheroid) and subcutaneous rat glioma.

The effects of combination chemotherapy of ACNU and 5-FU on cells grown exponentially as monolayers, cells in multi-cell spheroids and in s.c. transplanted tumors of rat glioma clone-6 cells were analyzed by the colony-forming assay. The cytotoxic effect of ACNU on cells in spheroids was enhanced by continuous 5-FU pretreatment for several hours, but further enhancement was obtained only if the 5-FU pretreatment lasted for more than 12 hr. The combined effect was decreased by a drug-free interval due to recovery from potentially lethal 5-FU damage, but ACNU treatment immediately after 5-FU treatment suppressed PLD recovery. Analysis with sequential trypsinization of spheroids indicated that ACNU showed more marked cytotoxicity on cells in the deeper layers in spheroids than on those in the outer layers, whereas the effect of 5-FU decreased towards the deeper cell layers. Enhancement of treatment with ACNU combined with 5-FU was evident for cells in the outer layers, but was more remarkable in the deeper layers. The combined effect of ACNU and 5-FU on s.c. tumors was similar to that in spheroids. The effect of combined treatment of ACNU with 5-FU on increase in body weight was within the additive range of both drugs acting independently, but was more than additive for the growth delay of s.c. tumors.