Effect of cell isolation methods and drug concentration on the use of the Differential Staining Cytotoxicity (DiSC) assay with solid tumours.

The Differential Staining Cytotoxicity (DiSC) in vitro drug sensitivity assay has been tested in solid tumours obtained from surgery. Various enzyme cocktails have been used for disaggregating cells for times ranging from 1-72 h. Collagenase (0.5%) plus DNase (0.002%) was chosen as producing the best results when incubated for 3 h at 37°C. This cocktail was also used for 24, 48 and 72 h incubations. Cell suspensions so produced were sometimes cleaned up by centrifugation on a Nycodenz gradient. Breast tumours were more often successfully cultured (67%) compared to gastrointestinal (43%) or other tumours (34%). Results with 6 drugs tested in 10 or more tumours suggested that in general, higher drug concentrations should be used when testing solid tumours as opposed to leukaemias in the DiSC assay.