Abstract A129: Novel histone deacetylase inhibitors ITF-A and ITF-B exhibit efficacy in preclinical models of mature B-cell lymphomas.

Abstract

Abstract Lymphomas are among the most common cancers. Despite significant progress made in their treatment, many patients still succumb to disease progression or relapse, or are refractory to current treatment regimens. Recently, the important role of epigenetic pathways in the pathogenesis of lymphomas has been highlighted, with several genes encoding epigenetic modifiers being shown to be selectively and prominently targeted by mutations and genomic aberrations. Histone deacetylase inhibitors (HDACi) are a class of molecules that have shown clinical efficacy in hematological malignancies, including T-cell lymphomas. Here, we have assessed the activity of two novel, class I, IIb, and IV HDACi, ITF-A and ITF-B, from Italfarmaco, in a panel of 29 non-Hodgkin lymphoma cell lines, comprising 21 diffuse large B-cell lymphoma (DLBCL) cell lines, 5 mantle cell lymphoma (MCL) cell lines, and 3 splenic marginal zone lymphoma (SMZL) cell lines. Cells were exposed to increasing concentrations of each HDACi and the MTT assay was performed after 72 hours to determine their cytotoxic and cytostatic effects estimating the IC50 (50%-inhibitory concentration), GI50 (50%-growth inhibition), LC50 (50%-lethal concentration), and TGI (total growth inhibition) values. Both ITF-A and ITF-B showed potent activities in most of the cell lines tested, irrespective of histological type, with the majority of IC50 values being below 100 nM. The median IC50 values were 13 nM (2-103 nM) and 33 nM (5-305 nM), for ITF-B and ITF-A, respectively. Median GI50 was 10 nM (1-63) for ITF-B, and 28 nM (2-217 nM) for ITF-A. The median LC50 values were 117 nM (10-2057 nM) and 42 nM (3-2388 nM) for ITF-A and ITF-B, respectively. The range of TGI values was 5-649 nM with a median of 59 nM for ITF-A, and 2-388 nM, with a median of 20n M for ITF-B. Both ITF-A and ITF-B induced apoptosis in the DLBCL and MCL tested as assessed by Annexin-V/7-AAD staining. Two DLBCL cell lines showing sensitivity to both HDACi, were chosen for further functional studies: DOHH2, a GCB-DLBCL cell line, and TMD8, a non-GCB DLBCL cell line. ITF-A and ITF-B presented both nuclear and cytoplasmic activity, as demonstrated by Western blotting analysis showing increased levels of both acetylated histone H3 and acetyl-α-tubulin following treatment with the two HDACi. Quantitative real-time PCR following 24 hours treatment of both cell lines with the two HDACi showed changes in the expression levels of STAT3, CDKN1A (p21) and MYC, suggesting roles for these genes in mediating the anti-proliferative effects of the two molecules. In conclusion, ITF-A and ITF-B showed promising activity in preclinical models of mature lymphomas and represent two new HDACi worthy of further pre-clinical evaluation as single agents and in combination with other agents. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A129. Citation Format: Afua A. Mensah, Eugenio Gaudio, Ivo Kwee, Andrea Rinaldi, Gianluca Fossati, Anastasios Stathis, Emanuele Zucca, Gianluca Caprini, Francesco Bertoni. Novel histone deacetylase inhibitors ITF-A and ITF-B exhibit efficacy in preclinical models of mature B-cell lymphomas. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A129.