title: Inhibition of KSP by ARRY-520 induces cell cycle block and cell death via the mitochondrial pathway in AML cells.
abstract: Kinesin spindle protein (KSP), a microtubule-associated motor protein essential for cell cycle progression, is overexpressed in many cancers and is a potential anti-tumor target. We found that inhibition of KSP by a selective inhibitor, ARRY-520, blocked cell cycle progression, leading to apoptosis in acute myeloid leukemia cell lines that express high levels of KSP. Knockdown of p53, overexpression of XIAP and mutation in caspase-8 did not significantly affect sensitivity to ARRY-520, suggesting that the response is independent of p53, XIAP and the extrinsic apoptotic pathway. Although ARRY-520 induced mitotic arrest in both HL-60 and Bcl-2-overexpressing HL-60Bcl-2 cells, cell death was blunted in HL-60Bcl-2 cells, suggesting that the apoptotic program is executed through the mitochondrial pathway. Accordingly, inhibition of Bcl-2 by ABT-737 was synergistic with ARRY-520 in HL-60Bcl-2 cells. Furthermore, ARRY-520 increased Bim protein levels prior to caspase activation in HL-60 cells. ARRY-520 significantly inhibited tumor growth of xenografts in SCID mice and inhibited AML blast but not normal colony formation, supporting a critical role for KSP in proliferation of leukemic progenitor cells. These results demonstrate that ARRY-520 potently induces cell cycle block and subsequent death in leukemic cells via the mitochondrial pathway and has the potential to eradicate AML progenitor cells.
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: B Z
authors.initials: BZ
authors.lastname: Carter
authors.forename: D H
authors.initials: DH
authors.lastname: Mak
authors.forename: R
authors.initials: R
authors.lastname: Woessner
authors.forename: S
authors.initials: S
authors.lastname: Gross
authors.forename: W D
authors.initials: WD
authors.lastname: Schober
authors.forename: Z
authors.initials: Z
authors.lastname: Estrov
authors.forename: H
authors.initials: H
authors.lastname: Kantarjian
authors.forename: M
authors.initials: M
authors.lastname: Andreeff
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D003114:Colony-Forming Units Assay; D005260:Female; D006801:Humans; D016547:Kinesins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013830:Thiadiazoles / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C470243:KIF11 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D013830:Thiadiazoles; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; C544550:filanesib; D053181:Caspase 8; D016547:Kinesins