sepantronium and Leukemia--Myeloid--Acute

Despite aggressive chemotherapy, approximately one-third of children with acute myeloid leukaemia (AML) relapse. More effective treatments are urgently needed. Survivin is an inhibitor-of-apoptosis protein with key roles in regulating cell division, proliferation and apoptosis. Furthermore, high expression of Survivin has been associated with poor clinical outcome in AML. The survivin suppressant YM155 (Sepantronium Bromide) has pre-clinical activity against a range of solid cancers and leukemias, although data in AML is limited. Therefore, we undertook a comprehensive pre-clinical evaluation of YM155 in paediatric AML. YM155 potently inhibited cell viability in a diverse panel of AML cell lines. All paediatric cell lines were particularly sensitive, with a median IC50 of 0.038 μM. Cell cycle analyses demonstrated concentration-dependent increases in a sub-G1 population with YM155 treatment, suggestive of apoptosis that was subsequently confirmed by an increase in annexin-V positivity. YM155-mediated apoptosis was confirmed across a panel of 8 diagnostic bone marrow samples from children with AML. Consistent with the proposed mechanism of action, YM155 treatment was associated with down-regulation of survivin mRNA and protein expression and induction of DNA damage. These data suggest that YM155-mediated inhibition of survivin is a potentially beneficial therapeutic strategy for AML, particularly paediatric disease, and warrants further evaluation.

Topics: Apoptosis; Blotting, Western; Cell Cycle; Cell Proliferation; Child; Flow Cytometry; Humans; Imidazoles; Inhibitor of Apoptosis Proteins; Leukemia, Myeloid, Acute; Naphthoquinones; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Survivin; Tumor Cells, Cultured

HL60 and U937 (acute myeloid leukemia (AML) cell lines) were assessed for sensitivity to YM155, and found to have distinct sensitive and resistant phenotypes, respectively. In HL60 cells, YM155 inhibition of growth proliferation was due to apoptosis which was measured by annexin V/PI staining. YM155 induced apoptosis through activation of intrinsic and extrinsic pathways that also culminated in caspase-3 activity and PARP cleavage. YM155 sensitivity was partially associated with this compound's ability to down-regulate survivin transcription since this was more pronounced in the HL60 cell line. However, marked differences were also observed in XIAP, Bcl-2, and Mcl-1L, and Mcl-1s. Furthermore, YM155 treatment completely inhibited production of total Akt protein in HL60, but not U937 cells. Importantly, Akt activity (pAkt-Ser473) levels were maintained in YM155 treated U937 cells which may help stabilize other anti-apoptotic proteins. Combination treatments with an Akt inhibitor, MK-2206, reduced levels of pAkt-Ser473 in U937 cells and synergistically sensitized them to YM155 cytotoxicity. Collectively our results indicate that Akt signaling may be an important factor mediating YM155 response in AML, and combinatorial therapies with Akt inhibitors could improve treatment efficacy in YM155-resistant cells.

Topics: Antineoplastic Agents; Apoptosis; Cell Cycle; Dose-Response Relationship, Drug; HL-60 Cells; Humans; Imidazoles; Inhibitor of Apoptosis Proteins; Leukemia, Myeloid, Acute; Myeloid Cell Leukemia Sequence 1 Protein; Naphthoquinones; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Survivin; U937 Cells

Overexpression of survivin is observed in various hematological malignancies, including acute myeloid leukemia (AML). Studies show that elevated expression of survivin correlates with a worse clinic outcome in AML patients. It remains unclear whether inhibition of survivin may alter the efficacy of chemotherapy against AML. Here, we evaluate the effects of specific knockdown of survivin on AML cells' sensitivity to chemotherapy, and investigate the therapeutic potential of the transcription inhibitor of survivin YM155 either alone or in combination with chemotherapeutic agents. We found Kasumi-1 and HL-60 cells had relatively higher expression levels of survivin among all AML cell lines tested. Specific knockdown of survivin in Kasumi-1 and HL-60 cells resulted in: inhibition of cell proliferation; cell cycle G2/M arrest; induction of DNA damage response and apoptosis. Downregulation of survivin enhanced etoposide- or doxorubicin-induced anti-proliferative/anti-survival activity in AML cells. The small molecule inhibitor YM155 reduced survivin in a dose- and time-dependent manner and trigged apoptosis in Kasumi-1 and HL-60 cells. The combinatorial effects of YM155 and chemotherapeutics were either synergetic or antagonistic, depending upon the drugs used for combination and the type of AML cells being treated. Collectively, our data demonstrate that survivin plays an important role in the maintenance and proliferation of AML cells. While specific knockdown of survivin enhances chemosensitivity, the combinations of YM155 and chemotherapeutic agents exhibit synergetic or antagonistic effects on AML cells. Our findings provide a rationale for further assessment of survivin-targeted therapy in the treatment of patients with AML.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Doxorubicin; Drug Synergism; Etoposide; HL-60 Cells; Humans; Imidazoles; Inhibitor of Apoptosis Proteins; Leukemia, Myeloid, Acute; Molecular Targeted Therapy; Naphthoquinones; Survivin