Beta-D-glucosyl-ifosfamide mustard (
D 19575, glc-IPM, INN =
glufosfamide) is a new agent for
cancer chemotherapy. Its mode of action, which is only partly understood, was investigated at the
DNA level. In the
breast carcinoma cell line MCF7
glufosfamide inhibited both the synthesis of
DNA and
protein in a dose-dependent manner, as shown by the decreased incorporation of [3H-methyl]-
thymidine into
DNA and [14C]-
methionine into
protein of these cells. Treatment of MCF7 cells with 50 microM
glufosfamide was sufficient to trigger
poly(ADP-ribose) polymerase (PARP) activation, as revealed by immunofluorescence analysis. Both CHO-9 cells, which are O6-methylguanine-DNA
methyltransferase (MGMT)-deficient, and an isogenic derivative, which has a high level of MGMT, showed the same cytotoxic response to
beta-D-glc-IPM, indicating that the O6 position of
guanine is not the critical target for cytotoxicity. By contrast, a sharp decrease in survival of cross-link repair deficient 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 survival 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 amounts of
ifosfamide mustard formed under the conditions of incubation. The results indicate that the
DNA crosslinks are the most critical cytotoxic lesions induced by
beta-D-glc-IPM.