Mechanistic aspects of the cytotoxic activity of glufosfamide, a new tumour therapeutic agent

beta-n-Glucosyl-ifosfamide mustard (D 19575, glc-IPM, INN = glufosfamide) i s a new agent for cancer chemotherapy. Its mode of action, which is only pa rtly understood, was investigated at the DNA level. In the breast carcinoma cell line MCF7 glufosfamide inhibited both the synthesis of DNA and protei n in a dose-dependent manner, as shown by the decreased incorporation of [H -3-methyl]-thymidine into DNA and [C-14]-methionine into protein of these c ells. Treatment of MCF7 cells with 50 mu M glufosfamide was sufficient to t rigger poly(ADP-ribose) polymerase (PARP) activation, as revealed by immuno fluorescence analysis. Both CHO-9 cells, which are O-6-methylguanine-DNA me thyltransferase (MGMT)-deficient, and an isogenic derivative, which has a h igh level of MGMT showed the same cytotoxic response to beta-D-glc-IPM, ind icating that the O-6 position of guanine is not the critical target for cyt otoxicity. By contrast, a sharp decrease in survival of crosslink repair de ficient CL-V5 B cells was observed already at concentrations of 0.1 mM beta -D-glc-IPM, whereas the wild-type V79 cells showed a 90% reduction in survi val only after treatment with 0.5 mM of this compound. The therapeutically inactive beta-L-enantiomer of glufosfamide also showed genotoxic effects in the same assays but at much higher doses. This was probably due to small a mounts of ifosfamide mustard formed under the conditions of incubation. The results indicate that the DNA crosslinks are the most critical cytotoxic l esions induced by beta-D-glc-IPM. (C) 2000 Cancer Research Campaign.