Combined effects of novel tyrosine kinase inhibitor AMN107 and histone deacetylase inhibitor LBH589 against Bcr-Abl–expressing human leukemia cells

Abstract

AMN107 (Novartis Pharmaceuticals, Basel, Switzerland) has potent in vitro and in vivo activity against the unmutated and most common mutant forms of Bcr-Abl. Treatment with the histone deacetylase inhibitor LBH589 (Novartis) depletes Bcr-Abl levels. We determined the effects of AMN107 and/or LBH589 in Bcr-Abl–expressing human K562 and LAMA-84 cells, as well as in primary chronic myelogenous leukemia (CML) cells. AMN107 was more potent than imatinib mesylate (IM) in inhibiting Bcr-Abl tyrosine kinase (TK) activity and attenuating p-STAT5, p-AKT, Bcl-xL, and c-Myc levels in K562 and LAMA-84 cells. Cotreatment with LBH589 and AMN107 exerted synergistic apoptotic effects with more attenuation of p-STAT5, p-ERK1/2, c-Myc, and Bcl-xL and increases in p27 and Bim levels. LBH589 attenuated Bcr-Abl levels and induced apoptosis of mouse pro-B BaF3 cells containing ectopic expression of Bcr-Abl or the IM-resistant, point-mutant Bcr-AblT315I and Bcr-AblE255K. Treatment with LBH589 also depleted Bcr-Abl levels and induced apoptosis of IM-resistant primary human CML cells, including those with expression of Bcr-AblT315I. As compared with either agent alone, cotreatment with AMN107 and LBH589 induced more loss of cell viability of primary IM-resistant CML cells. Thus, cotreatment with LBH589 and AMN107 is active against cultured or primary IM-resistant CML cells, including those with expression of Bcr-AblT315I.

Histone deacetylase inhibitors deplete enhancer of zeste 2 and associated polycomb repressive complex 2 proteins in human acute leukemia cells

“…In the present studies, we also observed an inhibition of colony growth but not apoptosis of the cultured AML cells following depletion of EZH2 as well as of SUZ12 and EED, by EZH2 siRNA. Treatment with levels of LBH589 and LAQ824 that results in growth arrest, differentiation, and apoptosis was also noted to deplete EZH2, SUZ12, and EED in the CML and AML cells (36,38). However, the precise mechanistic link between the depletion of the PRC2 complex components and LBH589-or LAQ824-induced growth arrest, differentiation, and loss of clonogenic survival was not established.…”

“…Cell pellets were washed with 1Â PBS, gently resuspended in 200 AL lysis buffer [1% Triton X-100, 1 mmol/L phenylmethylsulfonyl fluoride, 10 Ag/mL leupeptin, 1 Ag/mL pepstatin-A, 2 Ag/mL aprotinin, 20 mmol/L p-nitrophenyl phosphate, 0.5 mmol/L sodium orthovanadate, 1 mmol/L 4-(2-aminoethyl) benzenesulfonylfluoride hydrochloride], and incubated on ice for 30 min as described previously (38). Cell lysates were centrifuged at 12,000 rpm in a tabletop centrifuge for 15 min to remove the nuclear and cellular debris.…”

“…Colony growth was measured as a percentage of the control cell colony growth as described previously (38).…”

Seeking the causes and solutions to imatinib-resistance in chronic myeloid leukemia

“…In addition, the utilization of histone deacetylase inhibitors, together with TKIs, showed a synergistic effect on the level of apoptosis in primary cells isolated from CML patients. 92,93 histone deacetylase inhibitors alone have yet to be successfully translated into clinical therapies for imatinib-resistant CP-or AP-CML patients, but are currently being evaluated together with TKIs in an attempt to modulate minimal residual disease. [94][95][96] Epigenetic methylation can modulate the expression of genes associated with tumor suppression and apoptosis.…”

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

“…37 Similarly, the number of studies using LBH589 in ALL is very limited. 13,38 An important finding from our study is that the anti-leukemic effect of LBH589 is observed in every cytogenetic subtype of ALL including both T and B-cell ALL as well as patients with Philadelphia-positive ALL. This is in agreement with recent studies, which demonstrate a synergistic effect of HDACi with tyrosine kinase inhibitors such as imatinib or dasatinib.…”