Effects of chromatin function inhibitors on yeast whole cells and spheroplasts

Saccharomyces cerevisiae has long been used as an alternative experimental model in the study of cancer and anticancer drug action. Although this simple eukaryote has provided useful information, its value as an experimental model is often controversial due to the presence of the cell wall -- a cellular structure which is absent in higher eukaryotes. The aim of this study was to investigate the possible involvement of the cell wall in the ineffectiveness of some anticancer drugs in yeast, by enzymatic removal of the cell wall. The effects of exposing whole-cell cultures and spheroplasts to chromatin function inhibitors for 22 hours were investigated. Vinblastine, etoposide and paclitaxel had no cytotoxic effects on whole-cell cultures either with or without the addition of verapamil. The growth profiles of yeast spheroplasts following drug exposure were similar to those observed in whole cells. These data demonstrate that the resistance of the lower eukaryote to these drugs was not overcome by the enzymatic removal of the cell wall.