Morphological transformation of Syrian hamster embryo cells by mezerein

Mezerein (MEZ) has been described as a weak complete tumor promoter but an effective stage II promoter in the mouse skin initiation-promotion tumor model. In this study MEZ produced a strong transformation response when tested under code in the Syrian hamster embryo (SHE) clonal morphological transformation assay. Using a standard 7-day exposure protocol designed to detect complete carcinogens, MEZ was active at non-toxic concentrations, producing a linear response between 0.3-10 ng/ml in a log-log plot of transformation activity versus concentration. These concentrations were in the same range as those which had been shown to elicit promotion activity in several in vitro cell culture systems. Our data suggest that the SHE assay has the ability to detect some tumor promoters under the same conditions used to test for complete carcinogens. The possibility that MEZ may possess in vivo carcinogenic activity cannot be excluded.