Assessment of apoptosis by Yo-Pro-1 and propidium iodide in DLBCL lines. (A) Ly1 DLBCL line was incubated with decitabine alone (5μM), panobinostat alone (5nM), or their combination for 48 hours. Compared with the untreated control, panobinostat alone induced apoptosis in a minimal amount of cells. Decitabine alone induced apoptosis in 39.5% of cells and the combination of drugs at the same concentrations induced apoptosis in 61.4% of lymphoma cells. After normalization to the untreated control, RRR value is 0.6. (B) Histogram depiction of the experiment shown under panel A. (C) Panobinostat (2.5nM) and decitabine (2.5μM) in combination induce apoptosis in primary DLBCL lines. (D) RRR values across the spectrum of DLBCL lines for 4 explored HDACIs in combination with decitabine in flow cytometric measurement of apoptosis. Also shown are the RRR values for the combination of panobinostat and decitabine in primary DLBCL lines.