Correlation between crystal violet dissolution assay and manual colony counting on the in vitro effects of Hsp90-inhibitors.

Radiobiological experiments routinely require the estimation of cellular survival. Several cytotoxicity assays have been proposed, which have inherent advantages and disadvantages. The performance of one of them, the crystal violet dissolution assay, was examined under a broad range of conditions. PC-3M prostate carcinoma cells were exposed to ionizing radiation in the presence or absence of heat shock protein 90-inhibiting drugs. Colony formation as assessed by traditional manual counting was compared with the results from the crystal violet dissolution assay. The overall bivariate correlation of the data was determined (r = 0.743, p < 0.01). The variabilities of the data distributions from two different observers were quantitated and found to agree fairly. Ionizing radiation has a scattering-reducing effect that if plotted as Pearson-coeffcient versus radiation energy dose yields a sigmoidal distribution of data points. The crystal violet dissolution assay is a convenient tool for the rapid and reproducible determination of cellular survival and under appropriate conditions exerts a reasonable correlation to colony number.