Protection from adriamycin cytotoxicity in L1210 cells by brefeldin A

We present studies which suggest that the cytotoxic action of Adriamycin (ADR) may involve intracellular pathways of vesicular transport. The movement of proteins or lipids from the endoplasmic reticulum to the plasma membrane via the Golgi organelle and associated compartments exhibits several temperature-sensitive steps between 15 degrees C and 20 degrees C. In this same temperature range, ADR loses its cytotoxic capacity. Using the inhibitor brefeldin A (BFA), we have investigated the possible role of intravesicular trafficking in the loss of ADR activity and the induction of protection from cytotoxicity at low temperature in L1210 cells. We show here that cells pretreated at 37 degrees C for 2 h with BFA could be protected from a subsequent exposure to ADR. The concentration causing 50% inhibition, determined by cloning in soft agar, was increased approximately 3.5 fold. L1210 cells could also be protected from the topoisomerase II inhibitors etoposide and amsacrine, but to a lesser extent; the concentration causing 50% inhibition for the latter inhibitors were increased 2-fold. Spectrofluorometric analysis of intracellular ADR accumulation revealed that there was no significant difference in the level of ADR in cells with or without BFA pretreatment. In addition, examination of ADR-induced cleavable complex formation by alkaline elution showed no significant difference in the level of DNA strand breaks in cells which had been pretreated with BFA even though there was a large difference in survival. Further examination of the persistence of DNA damage after a period of up to 6 h of repair revealed that cells which were pretreated with BFA removed DNA strand breaks at rates equivalent to those of cells which had received ADR directly. These results suggest that the protective effect induced by brefeldin A does not involve uptake, DNA damage, or repair but instead implicates protein or lipid interactions which may be independent of DNA damage and which may influence critical events that take place after the topoisomerase II-DNA complex has been formed.