Abstract 5449: Histone deacetylase inhibitor treatment in B-cell non-Hodgkin's lymphoma - effect of ex vivo treatment on primary patient samples

Abstract

Abstract The use of histone deacetylase inhibitors (HDACis) is approved in cutaneous T-cell lymphoma, but the efficacy in other lymphomas, particularly B-cell Non-Hodgkin's lymphoma (B-NHL), remains to be established. To investigate the hypothesis that HDACis have anti-neoplastic effects in B-NHL, we have tested a series of primary B-NHL patient samples for response to the two HDACis Vorinostat (SAHA) and Panobinostat (LBH589). Lymph node biopsies from patients with B-NHL were obtained with patient consent. A single-cell suspension was prepared and mononuclear cells isolated by Ficoll gradient separation. Lymphocytes were treated with clinically achievable doses of SAHA (2.5 μM, 5 μM and 7 μM) and LBH589 (10 nM, 25 nM and 50 nM) ex vivo for 48 hours. Treatment effect was evaluated by assays of cell viability (trypan blue staining and Cell TiterGlo luminescence assay) and cell death (propidium iodide staining analyzed by flow cytometric quantification of the sub-G0 cell population). Expression of acetylated histone H4, Bcl-2 and BCL6 was evaluated by western blot. To date, 16 patient samples, covering a wide variety of B-NHL, have been analyzed. Diagnoses include: follicular lymphoma (n=7), diffuse large B-cell lymphoma (n=5), mantle cell lymphoma (n=1), nodal marginal zone lymphoma (n=1), hairy cell leukemia (n=1) and small lymphocytic lymphoma/chronic lymphocytic leukemia (n=1). Fifteen out of 16 patient samples analyzed showed moderate to high sensitivity to one or both HDACis tested at the given concentrations. Overall, the effects of SAHA and LBH589 were comparable. Western blots of lymphocytes treated with both types of HDACi showed increased acetylation of histone H4 compared to untreated cells. No change in Bcl-2 expression was seen (n=2) and no expression of BCL6 was detected in the samples tested for this (n=2). Based on the data outlined herein, B-NHL is sensitive to the growth inhibitory effects of HDACis at clinically achievable doses. Building upon this pilot study, we are developing cell line models of B-NHL in order to characterize the mechanism of action of HDACis in B-NHL, including combination therapy with currently used agents such as Rituximab. A phase 2 clinical trial of LBH589 in diffuse large B-cell lymphoma, including an arm evaluating combination therapy with Rituximab, is also planned. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5449.