Evaluation of Cytotoxic and Cytostatic Effects in Saccharomyces cerevisiae by Poissoner Quantitative Drop Test

Biological models have long been used to establish the cytotoxicity and cytostaticity of natural and/or synthetic chemical compounds. Current assay techniques, however, typically require the use of expensive technological equipment or chemical reagents, or they lack adequate testing sensitivity. The poissoner quantitative drop test (PQDT) assay is a sensitive, inexpensive and accurate method for evaluation of cytotoxicity and/or cytostatic effects of multiple chemical compounds in a single experiment. In this study, the sensitivity of the PQDT assay was evaluated in a wild-type Saccharomyces cerevisiae strain using 4-nitroquinoline-N-oxide (4-NQO) and methyl methanesulfonate (MMS), both cytotoxic and genotoxic standard compounds, and cytostatic 5-fluorouracil, an antitumoral drug. Yeast cell colony growth was measured in culture media containing increasing concentrations of the three chemical agents. The results showed that the PQDT assay was able to clearly differentiate the cytotoxic effect of 4-NQO and MMS from the cytostatic effect of 5-fluorouracil. Interestingly, the cytostatic effect of 5-fluorouracil followed an exponential decay curve with increasing concentrations, a phenomenon not previously described for this drug. The PQDT assay, in this sense, can be applied not only for cytotoxic/cytostatic assays, but also for pharmacodynamic studies using Saccharomyces cerevisiae as a model.