title: Biological effects of the Pim kinase inhibitor, SGI-1776, in multiple myeloma.
abstract: BACKGROUND
  Pim kinases are constitutively active serine/threonine/tyrosine kinases that are overexpressed in hematological malignancies such as multiple myeloma. Pim kinase substrates are involved in transcription, protein translation, cell proliferation, and apoptosis. SGI-1776 is a potent Pim kinase inhibitor that has proven to be cytotoxic to leukemia and lymphoma cells. Based on this background, we hypothesized that SGI-1776 treatment would result in myeloma cytotoxicity.
  
  
  METHODS
  To test this, myeloma cell lines and primary CD138(+) cells from myeloma patients were treated with SGI-1776 in a dose- and time-dependent manner, and effect on cell death and proliferation, induction of autophagy, and changes in cell cycle profile were measured.
  
  
  RESULTS
  SGI-1776 treatment resulted in limited apoptosis in cell lines (mean 30%) and CD138(+) cells (< 10%) assessed using Annexin-V/propidium iodide. Limited effect was observed in cell cycle profile or growth in cell lines. However, DNA synthesis was decreased by 70% at 3 μM (all time points) in U266 though this was not observed in MM.1S. In accordance, immunoblot analyses revealed no change in transcription (c-Myc and H3), or apoptotic (Bad) proteins that are substrates of Pim kinases. In contrast, autophagy, assessed using acridine orange staining, was induced with SGI-1776 treatment in both cell lines (U266, 25%-70%; MM.1S, 8%-52%) and CD138(+) cells (19%-21%). Immunoblot analyses of the autophagy LC3b marker and translation initiation proteins (phospho-p70S6K and 4E-BP1) corroborated autophagy induction.
  
  
  CONCLUSIONS
  These data indicate that SGI-1776 treatment in myeloma cell lines and CD138(+) myeloma cells elicits its deleterious effects through inhibition of translation and induction of autophagy.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Cervantes-Gomez
authors.forename: Lisa S
authors.initials: LS
authors.lastname: Chen
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Orlowski
authors.forename: Varsha
authors.initials: V
authors.lastname: Gandhi
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D051379:Mice; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051573:Proto-Oncogene Proteins c-pim-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011724:Pyridazines / Q000494:pharmacology*
chemical_list: D007093:Imidazoles; D047428:Protein Kinase Inhibitors; D011724:Pyridazines; C545188:SGI 1776; D051573:Proto-Oncogene Proteins c-pim-1; C406031:proto-oncogene proteins pim
keywords: Autophagy; Cell death; Multiple myeloma; Pim kinase inhibitor; SGI-1776