Evaluation of a Tetrazolium-based Semiautomated Colorimetrie Assay: Assessment of Chemosensitivity Testing1

Drug sensitivity assays were performed using a variation of a colori metrie [3-{4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)1 assay on V79, CHO-AuxBl, CH"C5, NCI-H460, and NCIH249 cell lines following optimization of experimental conditions for each cell line. Results from this assay were compared with data assimi lated simultaneously by clonogenic assay and by dye exclusion assay. Good correlation was observed using the CHO-AuxBl cell line and the pleiotropic drug-resistant mutant CH"C5, with similar degrees of relative resistance observed with both the M l'I and clonogenic assays. Good correlation was observed between the clonogenic and M l'I assays for Ih drug exposures, although the MIT assay was more sensitive to vinblastine. In general, the clonogenic assay was more sensitive when continuous drug exposures were utilized, although this was primarily related to the increased drug exposure time. While the use of the MIT assay in drug sensitivity testing of primary tumor samples is limited, since contaminating normal cells may also reduce the tetrazolium, the M I'I assay can be semiautomated, and therefore it offers a valid, simple method of assessing Chemosensitivity in established cell lines.