Vorinostat synergistically potentiates MK-0457 lethality in chronic myelogenous leukemia cells sensitive and resistant to imatinib mesylate

Abstract

Interactions between the dual Bcr/Abl and aurora kinase inhibitor MK-0457 and the histone deacetylase inhibitor vorinostat were examined in Bcr/Abl ؉ leukemia cells, including those resistant to imatinib mesylate (IM), particularly those with the T315I mutation. Coadministration of vorinostat dramatically increased MK-0457 lethality in K562 and LAMA84 cells. Notably, the MK-0457/vorinostat regimen was highly active against primary CD34 ؉ chronic myelogenous leukemia ( IntroductionChronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome (Ph; 22q), which is responsible for the chimeric fusion oncoprotein Bcr/Abl. The Bcr/Abl kinase is constitutively active and signals downstream to multiple survival pathways, 1 providing CML cells with a survival advantage over their normal counterparts and conferring resistance against cytotoxic agents. 2 The treatment of CML has been revolutionized by the introduction of the kinase inhibitor imatinib mesylate (IM; Gleevec, Novartis, Basel, Switzerland), which is highly active in patients with chronic-phase CML 3 but less active in patients with accelerated or blast-phase disease. 4 However, almost all patients who initially respond eventually develop resistance to this agent. Mechanisms of resistance include bcr/abl gene amplification, increased expression of the Bcr/Abl protein, and most commonly, point mutations in various domains of the Bcr/Abl kinase, including the activation loop, the phosphorylation loop, or the gatekeeper region. 5 This phenomenon stimulated the development of secondgeneration Bcr/Abl kinase inhibitors (eg, dasatinib and nilotinib), which are active against proteins bearing most mutations. 6,7 However, these agents are inactive against cells with gatekeeper region mutations, most notably T315I, 8 prompting the search for newer Bcr/Abl kinase inhibitors active against such mutants.The aurora kinases (A, B, and C) represent a family of serine/threonine kinases involved in the control of mitosis. 9 Deregulation of aurora kinase activity leads to disruption of cell-cycle progression, mitotic abnormalities, and genetic instability. 10 Importantly, aurora kinases are overexpressed and/or activated in a variety of tumor cells, suggesting a role for this family in tumorigenesis. 9,10 MK-0457 is a small-molecule, novel pan-aurora kinase inhibitor 9 with demonstrated activity against wild-type (wt) and mutated Bcr/Abl, [11][12][13] including the T315I mutation, as well as FLT3 and JAK2. MK-0457 delays entry into mitosis, leads to aberrant cytokinesis, induces apoptosis in several human tumor types, and is being evaluated in patients with a variety of malignant diseases. 9 MK-0457 potently inhibits aurora kinases (particularly aurora A and B) in tumor cells, manifested by down-regulation of phosphorylated histone H3 at Ser10. 9 This results in multiple events, including aberrant cell-cycle progression and accumulation of polyploid cells with DNA content of 4N or more, which collectively trigger cell death. 14,15 Very recently, it was repor...

BCR-ABL Hits at Mitosis; Implications for Chromosomal Instability, Aneuploidy and Therapeutic Strategy

“…Moreover, this has also been observed in CD34+ cells derived from untreated CML patients and from imatinibresistant patients in the chronic phase or blast crisis, including those harbouring the T315I mutation. Similar effects were obtained by combined treatment of imatinib resistant CML cells with vorinostat together with Aurora kinase inhibitor MK-0457 (Dai et al, 2008). Effectivity of this combined treatment has been shown against primary CD34+ CML cells, murine Ba/F3 cells with various BCR-ABL mutations (T315I, E255K, and M351T), as well as in imatinib-resistant K562 cells with BCR-ABL-independent, Lyn-dependent resistance.…”

Therapeutic Options Against BCR-ABL1 T315I-Positive Chronic Myelogenous Leukemia

“…Ongoing clinical studies of LBH589 in patients with refractory CML in all phases will also address the activity of single-agent LBH589 in patients with CML carrying BCR-ABL1 T315I. Subtoxic concentrations of vorinostat (0.5-2 Amol/L) were synergistic with MK-0457 (5-100 nmol/L) against primary CD34+ CML cells and Ba/F3 cells expressing BCR-ABL1 T315I, while sparing normal bone marrow mononuclear cells (79). Vorinostat strikingly enhanced MK-0457 -induced Aurora kinase inhibition, reflected by markedly diminished phosphorylation of histone H3 at residue Ser 10 .…”

Bim Upregulation by Histone Deacetylase Inhibitors Mediates Interactions with the Bcl-2 Antagonist ABT-737: Evidence for Distinct Roles for Bcl-2, Bcl-xL, and Mcl-1

“…Assessment of apoptosis. The extent of apoptosis was evaluated by flow cytometric analysis utilizing annexin V-fluorescein isothiocyanate (FITC)-propidium iodide or 3,3-dihexyloxacarbocyanine (DiOC 6 )-7-amino actinomycin D (7AAD) staining as described previously (15). Briefly, 1 ϫ 10 6 cells were stained with annexin V-FITC (BD PharMingen) and 5 g/ml propidium iodide (Sigma) in 1ϫ binding buffer for 15 min at room temperature in the dark.…”

“…Peripheral blood samples were obtained with informed consent according to the Declaration of Helsinki from four patients with acute myeloid leukemia (AML; FAB subtype M2) undergoing routine diagnostic aspirations, with approval from the Virginia Commonwealth University Institutional Review Board. Primary leukemic cells were isolated as previously described (15).…”

“…Notably, it has recently been reported that exposure to HDAC inhibitors induces Bim upregulation via an E2F1-dependent mechanism (73). This phenomenon has been postulated to contribute to the lethality of HDAC inhibitors, administered either alone (33,50,73) or in combination with other agents (14,15,24).…”