Improved detection of drug cytotoxicity in the soft agar colony formation assay through use of a metabolizable tetrazolium salt.

Use of a metabolizable tetrazolium salt was observed to facilitate assessments of tumor cell drug sensitivity in the soft-agar colony formation assay. Enzyme-mediated staining permits discrimination between viable and non-viable groups of cells so that drug-induced cytotoxicity is clearly identifiable by visual inspection as well as by computerized image analysis. The technique appears to be especially useful in the evaluation of primary tumor cell cultures which often contain substantial numbers of non-viable cellular aggregates.