HDAC9 and diffuse large B-cell lymphoma: While each of the HDAC inhibitors showed little activity when used as a single agent, they markedly sensitized resistant/moderately sensitive DLBCL cell lines to AD-O51.4 (CI<0.54 and CI<0.52 for SAHA + AD-O51.4 combinations in Toledo and U2932, respectively; CI<0.44 and CI<0.77 for panobinostat + AD-O51.4 combinations in Toledo and U2932, respectively; Figure 7).