Effect of amifostine on the cytotoxicity of daunorubicin and daunoxome in tumor and normal cells

Anthracyclines are powerful cytotoxic agents, used as first-line treatment of leukemias and many other tumors, but host-tissue toxicity is their main dose-limiting factor. However, their therapeutic effects depend not only on the toxicity, hence on the dose, but also on drug resistance. Among the mechanisms that can account for cell sensitivity to anthracyclines, there is an overexpression of drug transport proteins, like the transmembrane P-glycoprotein (PGP), the multidrug- resistance-related protein (MRP) and the lung-resistance-related protein (LRP). Attempts to reduce the toxicity of chemotherapeutic agents without affecting their efficacy have been made using liposomal anthracyclines or cytoprotective agents, as Amifostine. The aim of this study was to evaluate and compare the toxic effects of Daunorubicin, in normal or liposomal formulation, used in combination with WR1065, the active metabolite of Amifostine, against normal and tumor cells. In conclusion these data show that the preincubation with WR-1065 does not inhibit the drug toxic effect on blast cells and on tumor cell lines, independently by their multidrug resistance phenotype, but has a cytoprotective effect on stem cells causing a drug cytotoxicity reduction of 10-20%. This advantage is even higher using the liposomal formulation of DNR. Therefore, Amifostine can offer a chance of protecting normal cells from the toxicity of anthracyclines, in normal or liposomal formulation. The combination of liposomal anthracyclines with Amifostine can confer further advantages in management of leukemic patients, especially the elderly where treatment toxicity is a main problem. These patients may be candidates for alternative therapeutic strategies and the combination of DNX and Amifostine is an attractive treatment for these cases where a low nonhematological toxicity is required.