CHARACTERISTICS OF CANCER CELL-DEATH AFTER EXPOSURE TO CYTOTOXIC DRUGS IN-VITRO

The characteristics of cell death were investigated after exposure of CCRF-CEM.f2 cells to five drugs over a broad concentration range; thes e were the glucocorticoid dexamethasone (DXM), the mitotic inhibitor v incristine (VIN) and three antimetabolites, methotrexate (MTX), 5'-flu oro-2'-deoxyuridine (FUdR) and 5'-fluorouracil (5-FU). Drug-treated ce lls were monitored for cell death mechanisms at different times by exa mining the pattern of DNA degradation, cell morphology and how cytomet ric profile, together with effects on cell growth over 72 h. At growth -inhibitory drug concentrations, the first changes were cell cycle per turbations detectable after 4-6 h of drug exposure. The appearance of features characteristic of apoptotic cell death was noted after all dr ug treatments in the CCRF-CEM.f2 cell line, but the pattern and kineti cs varied considerably. VIN induced apoptotic changes by 12 h, while D XM treatment caused apoptosis only after 48 h. Both MTX and FUdR induc ed morphological changes characteristic of apoptosis at least 24 h bef ore internucleosomal DNA cleavage, which was detectable only after 48 h. In contrast, 5-FU did not cause internucleosomal DNA cleavage by 48 h at any concentration, despite the presence of morphologically apopt otic cells 24 h earlier. These data suggest that disruption of the cel l cycle caused by drug treatment may be the common trigger initiating the drug-specific apoptotic sequence of dying cells.