A comparative assessment of the in vitro effects of drugs on cells by means of colony assays or flow microfluorimetry.

The effects of a range of anticancer drugs on murine neuroblastoma cells, used as a readily reproducible model system, have been compared by means of colony-forming assays and analyses by flow microfluorimetry (FMF). FMF provides the most rapid means of assessing the kinetic effects of drugs on cells. However, interpretation of these data is not clear-cut, since drug effects are highly dose-dependent and no distinction can be made easily between progression arrest and cell kill. Thus whilst FMF allows some qualitative assessment of the perturbing effects of cytotoxic drugs quantitative evaluation of cytotoxicity is still dependent on data from the more time-consuming cloning assays. However, when cells are treated with certain drugs, e.g., methotrexate, vincristine, or VM26, for only 1 h, negligible kill occurred as measured by colony formation. Therefore it appears necessary to prolong in vitro exposure time when testing these drugs or evaluating cytotoxicity of potential antitumour agents in vitro.