Dual inhibition of akt/mammalian target of rapamycin pathway by nanoparticle albumin-bound-rapamycin and perifosine induces antitumor activity in multiple myeloma

Mol Cancer Ther. 2010 Apr;9(4):963-75. doi: 10.1158/1535-7163.MCT-09-0763. Epub 2010 Apr 6.

Abstract

The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway mediates multiple myeloma (MM) cell proliferation, survival, and development of drug resistance, underscoring the role of mTOR inhibitors, such as rapamycin, with potential anti-MM activity. However, recent data show a positive feedback loop from mTOR/S6K1 to Akt, whereby Akt activation confers resistance to mTOR inhibitors. We confirmed that suppression of mTOR signaling in MM cells by rapamycin was associated with upregulation of Akt phosphorylation. We hypothesized that inhibiting this positive feedback by a potent Akt inhibitor perifosine would augment rapamycin-induced cytotoxicity in MM cells. Perifosine inhibited rapamycin-induced phosphorylated Akt, resulting in enhanced cytotoxicity in MM.1S cells even in the presence of interleukin-6, insulin-like growth factor-I, or bone marrow stromal cells. Moreover, rapamycin-induced autophagy in MM.1S MM cells, as evidenced by electron microscopy and immunocytochemistry, was augmented by perifosine. Combination therapy increased apoptosis detected by Annexin V/propidium iodide analysis and caspase/poly(ADP-ribose) polymerase cleavage. Importantly, in vivo antitumor activity and prolongation of survival in a MM mouse xenograft model after treatment was enhanced with combination of nanoparticle albumin-bound-rapamycin and perifosine. Utilizing the in silico predictive analysis, we confirmed our experimental findings of this drug combination on PI3K, Akt, mTOR kinases, and the caspases. Our data suggest that mutual suppression of the PI3K/Akt/mTOR pathway by rapamycin and perifosine combination induces synergistic MM cell cytotoxicity, providing the rationale for clinical trials in patients with relapsed/refractory MM. Mol Cancer Ther; 9(4); 963-75. (c)2010 AACR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Albumins / pharmacology
  • Animals
  • Apoptosis / drug effects
  • Autophagy / drug effects
  • Bone Marrow Cells / drug effects
  • Bone Marrow Cells / pathology
  • Caspases / metabolism
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Down-Regulation / drug effects
  • Drug Screening Assays, Antitumor
  • Drug Synergism
  • Enzyme Activation / drug effects
  • Humans
  • Insulin-Like Growth Factor I / pharmacology
  • Interleukin-6 / pharmacology
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors*
  • Mice
  • Multiple Myeloma / enzymology*
  • Multiple Myeloma / pathology*
  • Multiple Myeloma / ultrastructure
  • Nanoparticles
  • Phosphorylation / drug effects
  • Phosphorylcholine / analogs & derivatives*
  • Phosphorylcholine / pharmacology
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors*
  • Signal Transduction / drug effects*
  • Sirolimus / pharmacology*
  • TOR Serine-Threonine Kinases
  • Xenograft Model Antitumor Assays

Substances

  • Albumins
  • Interleukin-6
  • Intracellular Signaling Peptides and Proteins
  • Phosphorylcholine
  • perifosine
  • Insulin-Like Growth Factor I
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Caspases
  • Sirolimus