Cytotoxicity of treosulfan and busulfan on pediatric tumor cell lines.

High-dose chemotherapy of solid tumors aims at eliminating residual or metastatic tumor cells, which remained after conventional treatment. Thus, anticancer drugs used for high-dose chemotherapy should display significant cytotoxicity against the respective tumors. As little data are available about the in-vitro toxicity of busulfan and treosulfan especially on pediatric tumor cell lines, we compared the cytotoxicity of treosulfan and busulfan on four Ewing tumor, four neuroblastoma, two osteosarcoma and two leukemia cell lines in vitro. Growth inhibition of tumor cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide test after 24, 48, 72 and 96 h. Treosulfan and busulfan reduced the growth of all tumor cell lines in a time-dependent and dose-dependent manner. In vitro treosulfan was consistently more cytotoxic than busulfan. Fifty percent growth inhibitions of 608-0.73 micromol/l were determined for treosulfan and of above 5,000-2.81 micromol/l for busulfan. Both drugs exhibited similar cytotoxicity profiles. Busulfan-sensitive/resistant cell lines were also sensitive/resistant to treosulfan. Overall, the leukemia cell lines were most sensitive to busulfan and treosulfan. The Ewing tumor cell lines were the second most sensitive followed by the neuroblastoma cell lines. The osteosarcoma cell lines were the most resistant cell lines. Although the in-vitro stability of both drugs makes direct comparison of their in-vitro toxicity difficult and does not allow any estimation of dosages needed clinically, the in-vitro results indicate substantial cytotoxicity of both drugs on leukemias, Ewing tumors and neuroblastomas. These data suggest further evaluation of treosulfan for high-dose chemotherapy of advanced Ewing tumors, neuroblastomas and high-risk leukemias.