Cell survival following treatment with antitumor drugs.

Tsukeda et a!. (13) recently published a report detailing experiments where the presumed cytotoxic action of sev eral antitumom agents was measured by a dye exclusion test. Cells were continuously treated with the agents for periods of 4 to 6 days and stained with 0.2% nigrosin every 12 hr. Cell viability was evaluated as a function of dye incorporation. These investigators claimed that their method was adequate and appropriate because: (a) it was simple and rapid; (b) it did not require “additional treatment that may affect the results @ ; and (c) cells were continuously exposed to drugs for 4 days allowing estimation of †̃ †̃cumu lative cell death.' â€T̃hey further maintained that, although the colony formation technique used by many investigators to assess drug-induced cell lethality might be more reliable than the dye exclusion technique, it had the disadvantage of varying plating efficiencies among different cell lines. It is unclear how these arguments can validate the obso lete dye exclusion method for cytotoxic assays. While the disadvantage of varying plating efficiencies among different cell lines can be internally corrected in reference to Un treated control cells, the speed and simplicity of the dye exclusion method cannot amend the inaccuracies of me suIts. It is also incorrect that cells used for dye exclusion do not undergo traumatic manipulation inasmuch as such cells must be harvested, either by scraping or by enzymatic treatment, before counting in a hemocytometem. Further more, continuous incubation with drugs is an artificial