A novel high-through-put assay for screening of pro-apoptotic drugs

Screening for anti-cancer substances is commonly conducted using viability assays. An inherent problem with this approach is that all compounds that are toxic and growth inhibitory, irrespective of mechanism of action, will score positive. It would be beneficial to be able to screen for compounds that specifically induce apoptosis. We here describe an ELISA-assay based on a monoclonal antibody (M30) which recognizes a neo-epitope on cytokeratin 18 exposed after cleavage by caspases during apoptosis. We show that this assay detects apoptosis in epithelial cells and that the sensitivity is sufficient for screening in the 96-well format. We used the M30-ELISA assay to screen 500 low molecular weight compounds from a chemical library from the National Cancer Institute and identified 16 drugs with strong pro-apoptotic activity, suggesting that the assay is a useful tool for discovery of pro-apoptotic drugs.