title: N-benzoylstaurosporine (PKC412) inhibits Akt kinase inducing apoptosis in multiple myeloma cells.
abstract: Multiple myeloma is a clonal malignancy of plasma cells that invariably progresses to a chemoresistant state. The PI3K/Akt pathway mediates signals downstream of several growth factors involved in myeloma pathogenesis, and constitutive activation of Akt was observed in myeloma cells. We now report that a staurosporine derivative, N-benzoylated staurosporine or PKC412, induces cell death in myeloma cell lines (RPMI8226S, U266, MM1S and MM1R) with loss of mitochondrial membrane potential Delta psi m, caspase 3 and PARP cleavage. ZVAD.fmk, but not interleukin-6, rescued these cells from PKC412 effects. Upstream of the mitochondria, PKC412 inhibited Bad phosphorylation and attenuated Akt kinase activity by suppressing its phosphorylation on serine residue in its activation loop. Reduced phosphorylation of downstream Akt substrates GSK3 alpha/beta and FKHR was also noted. Stable transfection of 8226S cells with constitutively active Akt (8226S-myAkt) partially protected against PKC412 cytotoxicity. Primary myeloma cells isolated from refractory myeloma patients (n=4), were equally sensitive to PKC412 treatment. More importantly, PKC412 did not affect CFU-GM or BFU-E colony formation. In summary, our results demonstrate that PKC412 suppresses Akt kinase activation and induces apoptosis in myeloma cell lines, as well as primary resistant cells. PKC412 is an appropriate candidate for novel treatment protocols for multiple myeloma.
authors: University of Calgary, Department of Medicine, Division of Hematology and Hematological Malignancies, Calgary, Alberta, Canada.
authors: Nizar J
authors: NJ
authors: Bahlis
authors: Yanling
authors: Y
authors: Miao
authors: Omer N
authors: ON
authors: Koc
authors: Kelvin
authors: K
authors: Lee
authors: Lawrence H
authors: LH
authors: Boise
authors: Stanton L
authors: SL
authors: Gerson
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D019311:Staurosporine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D004791:Enzyme Inhibitors; D015850:Interleukin-6; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D019311:Staurosporine; C059539:midostaurin