Cell Viability and Propidium Iodide Uptake Assays

Cell viability assays were performed using MTT/MTS as previously described^{8 (link)}. For propidium iodide uptake assays in serum-free medium, U937 cells (after centrifugation at 300 g, 5 min) were washed once in serum-free RPMI-1640, pelleted again (as previous centrifugation) and resuspended in serum-free media. 4×10⁴ cells were seeded and incubated with a range of CpoBD13 concentrations (diluted in serum-free medium) for 30 min at 37°C. PI (diluted in ice-cold PBS) was added to a final concentration of 1 µg/mL before analysis by flow cytometry using a BD FACSCanto II with FACSDiva 8.0.1 (BD Biosciences).