Cell proliferation assay. In a tetrazolium salt based assay, the proliferative behavior of cell lines with stable EpCAM expression in comparison to empty vector control and untransfected cells has been measured. EpCAM transfected Hs578T cells show enhanced doubling frequency than non-transfected cells and empty vector controls. This effect appears two days after cell seeding. No similar effect could be detected in the stable transfected MDA-MB-231EpCAM cell line. Absorbance was normalized to the 24 hours values.