Comparison of in vitro drug sensitivity by the differential staining cytotoxicity (DiSC) and colony-forming assays

In this study the authors have tested the ability of the DiSC assay to assess cytotoxicity, and to determine whether the index of early loss of viability correlates with the loss of reproductive potential. A 1 h drug exposure was used to ensure that cytotoxic rather than cytostatic effects were measured. The results obtained indicate that the cytotoxicities of drugs with widely differing mechanisms of action are able to be assessed with the DiSC assay, in contrast to traditional dye-exclusion assays. They have shown the colony-forming assay to be generally more sensitive to the drugs tested that are not strictly phase specific, whilst with cytarabine, the DiSC assay has shown a greater sensitivity. The results of this study suggest that these two assay methodologies are not strictly comparable. Thus the drug concentrations used to predict for patient response with the two assays could be expected to be different by as much as one order of magnitude or more.