The Novel Deacetylase Inhibitor AR-42 Demonstrates Pre-Clinical Activity in B-Cell Malignancies In Vitro and In Vivo

Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA.
PLoS ONE (Impact Factor: 3.23). 06/2010; 5(6):e10941. DOI: 10.1371/journal.pone.0010941
Source: PubMed


While deacetylase (DAC) inhibitors show promise for the treatment of B-cell malignancies, those introduced to date are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have shown suboptimal activity or unacceptable toxicities. We therefore investigated the novel DAC inhibitor AR-42 to determine its efficacy in B-cell malignancies.
In mantle cell lymphoma (JeKo-1), Burkitt's lymphoma (Raji), and acute lymphoblastic leukemia (697) cell lines, the 48-hr IC(50) (50% growth inhibitory concentration) of AR-42 is 0.61 microM or less. In chronic lymphocytic leukemia (CLL) patient cells, the 48-hr LC(50) (concentration lethal to 50%) of AR-42 is 0.76 microM. AR-42 produces dose- and time-dependent acetylation both of histones and tubulin, and induces caspase-dependent apoptosis that is not reduced in the presence of stromal cells. AR-42 also sensitizes CLL cells to TNF-Related Apoptosis Inducing Ligand (TRAIL), potentially through reduction of c-FLIP. AR-42 significantly reduced leukocyte counts and/or prolonged survival in three separate mouse models of B-cell malignancy without evidence of toxicity.
Together, these data demonstrate that AR-42 has in vitro and in vivo efficacy at tolerable doses. These results strongly support upcoming phase I testing of AR-42 in B-cell malignancies.

Download full-text


Available from: Michael A Freitas,
  • Source
    • "Studies in vivo have been reported in Tcl1 transgenic mice that develop a disease similar to CLL patients with elevated B cells, splenomegaly and infiltration of B cells in various organs [52]. The activity of HDACi AR-42 was tested in a Tcl1 transplant model and treated mice showed reduction in peripheral leukocyte counts and survived longer [53]. There are also encouraging results of clinical trial data in CLL patients with different HDACi [54]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The tumor suppressor gene E-cadherin gene is frequently silenced in chronic lymphocytic leukemia (CLL) cells and results in wnt-pathway activation. We analyzed the role of histone epigenetic modifications in E-cadherin gene silencing. CLL specimens were treated with histone deacetylase inhibitor (HDACi) MS-275 and analyzed for E-cadherin expression with western blot and RT-PCR analysis. The downstream effects of HDACi treated leukemic cells were studied by analyzing the effect on wnt-pathway signaling. HDACi induced alterations in E-cadherin splicing were investigated by transcript specific real time PCR analysis. Treatment of CLL specimens with histone deacetylase inhibitors (HDACi) treatment resulted in an increase of the E-cadherin RNA transcript (5 to 119 fold increase, n=10) in eight out of ten CLL specimens indicating that this gene is down regulated by histone hypoacetylation in a majority of CLL specimens. The E-cadherin re-expression in CLL specimens was noted by western blot analysis as well. Besides epigenetic silencing another mechanism of E-cadherin inactivation is aberrant exon 11 splicing resulting in an alternatively spliced transcript that lacks exon 11 and is degraded by the non-sense mediated decay (NMD) pathway. Our chromatin immunoprecipitation experiments show that HDACi increased the acetylation of histones H3 and H4 in the E-cadherin promoter region. This also affected the E-cadherin exon 11 splicing pattern as HDACi treated CLL specimens preferentially expressed the correctly spliced transcript and not the exon 11 skipped aberrant transcript. The re-expressed E- cadherin binds to β-catenin with inhibition of the active wnt-beta-catenin pathway in these cells. This resulted in a down regulation of two wnt target genes, LEF and cyclinD1 and the wnt pathway reporter. The E-cadherin gene is epigenetically modified and hypoacetylated in CLL leukemic cells. Treatment of CLL specimens with HDACi MS-275 activates transcription from this silent gene with expression of more correctly spliced E-cadherin transcripts as compared to the aberrant exon11 skipped transcripts that in turn inhibits the wnt signaling pathway. The data highlights the role of epigenetic modifications in altering gene splicing patterns.
    BMC Cancer 02/2013; 13(1):88. DOI:10.1186/1471-2407-13-88 · 3.36 Impact Factor
  • Source
    • "Benzamide MGCD0103 Class I, II Phase II clinical trials [63] Cyclic peptide FK228 Class I, II FDA approved for CTCL [64] Hydroxamates SAHA Class I, II FDA approved for CTCL [63] LBH589 Class I, II Phase II and III clinical trials [23] Trichostatin A Class I, II Experimental use [65] [66] Others AR-42 Class I, II Started clinical trials [67] CUDC101 Class I, II Started clinical trials [68] Note: Valproic acid has been in use as an anticonvulsant and mood stabilizing drug in the treatment of epilepsy and bipolar disorder. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Histone deacetylase inhibitors (HDACIs) have been actively explored as a new generation of chemotherapeutics for cancers, generally known as epigenetic therapeutics. Recent findings indicate that several types of HDACIs repress angiogenesis, a process essential for tumor metabolism and progression. Accumulating evidence supports that this repression is mediated by disrupting the function of hypoxia-inducible factors (HIF-1, HIF-2, and collectively, HIF), which are the master regulators of angiogenesis and cellular adaptation to hypoxia. Since HIF also regulate glucose metabolism, cell survival, microenvironment remodeling, and other alterations commonly required for tumor progression, they are considered as novel targets for cancer chemotherapy. Though the precise biochemical mechanism underlying the HDACI-triggered repression of HIF function remains unclear, potential cellular factors that may link the inhibition of deacetylase activity to the repression of HIF function have been proposed. Here we review published data that inhibitors of type I/II HDACs repress HIF function by either reducing functional HIF-1α levels, or repressing HIF-α transactivation activity. In addition, underlying mechanisms and potential proteins involved in the repression will be discussed. A thorough understanding of HDACI-induced repression of HIF function may facilitate the development of future therapies to either repress or promote angiogenesis for cancer or chronic ischemic disorders, respectively.
    BioMed Research International 01/2011; 2011(1110-7243):197946. DOI:10.1155/2011/197946 · 2.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The histone deacetylase inhibitors (HDACi) have demonstrated anticancer efficacy across a range of malignancies, most impressively in the hematological cancers. It is uncertain whether this clinical efficacy is attributable predominantly to their ability to induce apoptosis and differentiation in the cancer cell, or to their ability to prime the cell to other pro-death stimuli such as those from the immune system. HDACi-induced apoptosis occurs through altered expression of genes encoding proteins in both intrinsic and extrinsic apoptotic pathways; through effects on the proteasome/aggresome systems; through the production of reactive oxygen species, possibly by directly inducing DNA damage; and through alterations in the tumor microenvironment. In addition HDACi increase the immunogenicity of tumor cells and modulate cytokine signaling and potentially T-cell polarization in ways that may contribute the anti-cancer effect in vivo. Here, we provide an overview of current thinking on the mechanisms of HDACi activity, with attention given to the hematological malignancies as well as scientific observations arising from the clinical trials. We also focus on the immune effects of these agents.
    Investigational New Drugs 12/2010; 28 Suppl 1(S1):S3-20. DOI:10.1007/s10637-010-9596-y · 2.92 Impact Factor
Show more