To select for compounds that synthetically kill p53-deficient tumor cells, we developed a robust and sensitive image-based screen using newly generated stable cell lines of HCT116 p53+/+ and p53−/− expressing histone 2B (H2B)-GFP and histone 2B (H2B)-RFP fusion proteins, respectively (Fig. 1a)30. Here, H2BC21 is linked to neoplasm.