Anticancer agents are potent neurotoxins in vitro and in vivo

Neurotoxicity of anticancer agents complicates treatment of children with cancer. We investigated neurotoxic effects of common cytotoxic drugs in neuronal cultures and in the developing rat brain. When neurons were exposed to cisplatin (5-100 microM), cyclophosphamide (5-100 microM), methotrexate (5-100 microM), vinblastin (0.1-1 microM), or thiotepa (5-100 microM), a concentration-dependent neurotoxic effect was observed. Neurotoxicity was potentiated by nontoxic glutamate concentrations. The N-methyl-D-aspartate receptor antagonist MK 801 (10 microM), the AMPA receptor antagonists GYKI 52466 (10 microM) and NBQX (10 microM), and the pancaspase inhibitor Ac-DEVD-CHO (1 nM) ameliorated neurotoxicity of cytotoxic drugs. To investigate neurotoxicity in vivo, we administered to 7-day-old rats the following: cisplatin (5-15 mg/kg i.p.), cyclophosphamide (200-600 mg/kg i.p.), thiotepa (15-45 mg/kg), or ifosfamide (100-500 mg/kg) and their brains were analyzed at 4 to 24 hours. Cytotoxic drugs produced widespread lesions within cortex, thalamus, hippocampal dentate gyrus, and caudate nucleus in a dose-dependent fashion. Early histological analysis demonstrated dendritic swelling and relative preservation of axonal terminals, which are morphological features indicating excitotoxicity. After longer survival periods, degenerating neurons displayed morphological features consistent with active cell death. These results demonstrate that anticancer drugs are potent neurotoxins in vitro and in vivo; they activate excitotoxic mechanisms but also trigger active neuronal death.