STUDIES ON THE CYTOSTATIC AND CYTOTOXIC EFFECTS AND MODE OF ACTION OF8-NITRO-7-HYDROXYCOUMARIN

A derivative of coumarin, 8-nitro-7-hydroxycoumarin (8-NO2-7-OHC), was synthesised, purified and characterised. The cytostatic and cytotoxic nature of this compound was determined using both human and animal ce ll lines grown in vitro for 96 h in the presence of drug (0-500 mu M, equivalent to 0-104 mu g/ml). 8-NO2-7-OHC was shown to be cytotoxic to three cell lines, but cytostatic to all cell lines tested. With K562 and HL-60 cells, cell death was found to occur by apoptosis. This cyto toxic effect was found to be irreversible, with cell death continuing to occur following a 96 h recovery period. The cytostatic effects were found to be irreversible in four of the five cell lines tested. 8-NO2 -7-OHC demonstrated its cytostatic effects within 24 or 48 h, while it s cytotoxic effects appeared more gradually. The IC50 of 8-NO2-7-OHC w as 475-880 mu M, depending on the cell line tested. It was shown to ex ert its cytostatic effect through an alteration of cell cycle. It also inhibited DNA synthesis. The toxicity of 8-NO2-7-OHC does not appear to be mediated through the multi-drug resistance (MDR) protein since i t caused significant cytostatic and cytotoxic effects to CHrC5 cells, which have an increased expression of this protein. This compound was shown to be non-mutagenic in a standard Ames test, both with or withou t a mammalian enzyme activation system. The applications and mode of a ctions of coumarins are discussed. (C) 1997 Elsevier Science Ireland L td.