Predictability of in vivo chemosensitivity by in vitro MTT assay with reference to the clonogenic assay

The MTT assay reported by Mosmann is a rapid and convenient colorimetric assay for cellular growth and survival in vitro. In this paper, the MTT assay was modified as a chemosensitivity test, and its potential was investigated. Using 10 human tumor xenografts in athymic nude mice, the predictability of in vitro antitumor effects of drugs using the MTT assay was compared with that using the clonogenic assay. The MTT assay showed excellent reproducibility, and the predictable rate in this assay was 86.7%, with 100% true-positive and 77.8% true-negative rates, almost equivalent to the 90.0% predictable rate of the clonogenic assay. This method also has several advantages with respect to rapidity, quantitation, management of many samples, and cell number required for the assay. Application of this assay to chemosensitivity testing seems to be valuable and useful.