Application of the MTT assay to human prostate cancer cell lines in vitro: establishment of test conditions and assessment of hormone-stimulated growth and drug-induced cytostatic and cytotoxic effects.

In this study the usefulness of the MTT assay for the quantitation of growth modulating effects on cultured prostate cancer lines (PC-3, PC-93, and LNCaP) was investigated. The MTT test is based on the enzymatic reduction of the tetrazolium salt MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide++ +] in living, metabolically active cells but not in dead cells. The reaction is carried out in situ in multiwell plates, and the reaction product, a purple-colored formazan soluble in dimethylsulfoxide, is measured colorimetrically, using a multiwell plate reader. Optimal test conditions were established for each of the cell lines used. With the hormone-sensitive cell line LNCaP, and stimulatory effect of the synthetic androgen R1881 was demonstrable by the MTT test. A sharp optimum occurred at a concentration of 10(-10) M R1881. Treatment of cells of either cell line with antineoplastic agents resulted in a dose-dependent reduction of MTT converting activity, reflecting the impaired survival of the drug-treated cells. Good correlations of the results obtained with the MTT-test, as compared with a thymidine incorporation assay or with direct DNA measurements, were observed. As the MTT test offers a high degree of precision and is easy to do, it is suitable for the purpose of (large-scale) chemosensitivity testing. Moreover, serial measurements might easily be performed in order to provide additional information on the mode of action of the drugs tested, i.e., to discriminate between cytostatic and cytotoxic drug effects.