The novel histone deacetylase inhibitor, LBH589, induces expression of DNA damage response genes and apoptosis in Ph− acute lymphoblastic leukemia cells

Abstract

We investigated the mechanism of action of LBH589, a novel broad-spectrum HDAC inhibitor belonging to the hydroxamate class, in Philadelphia chromosome-negative (Ph ؊ ) acute lymphoblastic leukemia (ALL) . IntroductionHistone deacetylases (HDACs) are responsible for deacetylating histones and nonhistone proteins, thus regulating gene transcription, protein function, and stability. 1,2 Aberrant recruitment of HDACs has been shown to have an important role in leukemogenesis, and alterations in the expression and/or activity of HDACs have been also observed in solid tumors. [3][4][5] HDAC inhibitors have been widely studied, clinical trials with several of these have started, and HDAC inhibitor-responsive tumors have been observed. [6][7][8][9] Clinical benefits of HDAC inhibitors may result from re-expressing and/or reactivating tumor suppressor genes and/or proteins, thereby inducing apoptosis, cell-cycle arrest, and differentiation. [6][7][8][9] In most cases of acute lymphoblastic leukemia (ALL), chromosomal abnormalities are found such as the gain or loss of whole chromosomes, but more often, translocations, deletions, or inversions occur. [10][11][12] Epigenetic alterations, including aberrant DNA methylation of promoter-associated CpG islands resulting in gene silencing, have been frequently observed in ALL both at presentation and at relapse. 13,14 There is a need for new agents with efficacy in Ph Ϫ ALL, especially for patients who relapse where the treatment options are limited. [15][16][17][18] Treatment of ALL cells with an HDAC inhibitor offers an appealing strategy, potentially promoting, in the resistant lymphoblasts, reactivation of genes responding to genomic instability and therefore elimination of the affected cells.In this study, we evaluated the antitumor efficacy and mechanism of action of LBH589, an HDAC inhibitor belonging to the hydroxamate class, in Philadelphia chromosome-negative (Ph Ϫ ) ALL cells. Two Ph Ϫ ALL cell lines (T-cell MOLT-4 and pre-B-cell Reh) were treated with LBH589. Our results show that LBH589, at clinically safe concentrations (approximately 10-50 nM), induces potent cell growth inhibition, cell-cycle arrest, and apoptosis in a time-and dose-dependent manner in both cell lines. We further show that the antitumor activities of LBH589 correlate with induction of histone (H3K9 and H4K8) hyperacetylation, activation of p21 and p27, and suppression of c-Myc in the 2 cell lines treated. Using polymerase chain reaction (PCR) arrays, we determined the effects of LBH589 on the expression of DNA damage and apoptosis genes. LBH589 treatment induced significant increases in mRNA levels of a number of genes with proapoptosis, growth arrest, and DNA repair functions. Some of these genes have been previously reported to be epigenetically down-regulated in human malignancies such as GADD45G. 19 Furthermore, we demonstrate that LBH589 response correlates with induction of histone H2A.X phosphorylation. Importantly, LBH589 also induces apoptosis and elevated GADD45G expression in culture...

Interconnecting molecular pathways in the pathogenesis and drug sensitivity of T-cell acute lymphoblastic leukemia

“…Our finding that the NF-B pathway is up-regulated with Notch1 in polyclonal DP cells in the mouse model (supplemental Figure 3) supports this interpretation. With respect to HDAC inhibitors, several reports including our own have demonstrated that these drugs can inhibit the growth of T-ALL cells, 23,42 but our current study is the first to show synergism between the vorinostat HDAC inhibitor and GSI in T-ALL cells. Notably, the CDKN2D gene is highly up-regulated by the treatment with vorinostat in the leukemia and cancer cell lines included in the CMAP database (data not shown); indeed, treatment with vorinostat induced CDKN2D expression in each of the T-ALL cell lines (supplemental Figure 8).…”

The HDAC inhibitor LBH589 (panobinostat) is an inhibitory modulator of aromatase gene expression

“…Thus, selective inhibitors of HDAC6 are thought to be useful for cancer therapy (22). The HDAC6 inhibitor LBH589 induces expression of DNA damage response genes and apoptosis in Ph − acute lymphoblastic leukemia cells (23). This inhibitor is well tolerated and induces clinical responses in cutaneous T cell lymphoma patients (24).…”

Preclinical activity of LBH589 alone or in combination with chemotherapy in a xenogeneic mouse model of human acute lymphoblastic leukemia

“…This is in agreement with recent studies, which demonstrate a synergistic effect of HDACi with tyrosine kinase inhibitors such as imatinib or dasatinib. 39 Although mechanisms related to acetylation of other proteins may be involved in the effect of LBH589, 40 the time-and dose-dependent studies performed suggest that activation of acetylation of H3 and H4 are early events in ALL (2 h after in vitro treatment). Interestingly, an increase in acetylation of H3 and H4 in leukemic cells was not only found in vitro but also in leukemic cells obtained from the spleen of treated mice.…”