Correlative studies on samples obtained from patients treated with panobinostat. (A) Immunohistochemistry for CD20 and percentage BM involvement in pre- and posttreatment samples. (B) ELISA for acetylated histone 3 (H3) in PBMCs of samples before therapy in 10 patients with the clinical responses that were obtained in these patients. (C) ELISA for acetylated H3 in PBMCs of samples before and after therapy in 3 patients. Although the levels before and after therapy were not statistically different, there was a trend of increases in the level of acetylated H3 after therapy that is consistent with the activity of HDAC inhibitors.