Calcineurin complex isolated from T-cell acute lymphoblastic leukemia (T-ALL) cells identifies new signaling pathways including mTOR/AKT/S6K whose inhibition synergize with calcineurin inhibition to promote T-ALL cell death

Oncotarget. 2016 Jul 19;7(29):45715-45729. doi: 10.18632/oncotarget.9933.


Calcineurin (Cn) is a calcium activated protein phosphatase involved in many aspects of normal T cell physiology, however the role of Cn and/or its downstream targets in leukemogenesis are still ill-defined. In order to identify putative downstream targets/effectors involved in the pro-oncogenic activity of Cn in T-cell acute lymphoblastic leukemia (T-ALL) we used tandem affinity chromatography, followed by mass spectrometry to purify novel Cn-interacting partners. We found the Cn-interacting proteins to be part of numerous cellular signaling pathways including eIF2 signaling and mTOR signaling. Coherently, modulation of Cn activity in T-ALL cells determined alterations in the phosphorylation status of key molecules implicated in protein translation such as eIF-2α and ribosomal protein S6. Joint targeting of PI3K-mTOR, eIF-2α and 14-3-3 signaling pathways with Cn unveiled novel synergistic pro-apoptotic drug combinations. Further analysis disclosed that the synergistic interaction between PI3K-mTOR and Cn inhibitors was prevalently due to AKT inhibition. Finally, we showed that the synergistic pro-apoptotic response determined by jointly targeting AKT and Cn pathways was linked to down-modulation of key anti-apoptotic proteins including Mcl-1, Claspin and XIAP. In conclusion, we identify AKT inhibition as a novel promising drug combination to potentiate the pro-apoptotic effects of Cn inhibitors.

Keywords: T-cell acute lymphoblastic leukemia; apoptosis; calcineurin; mTOR signaling; protein complex.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Calcineurin / metabolism*
  • Calcineurin Inhibitors / pharmacology
  • Cell Line, Tumor
  • Cyclosporine / pharmacology
  • Heterocyclic Compounds, 3-Ring / pharmacology
  • Humans
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • NFATC Transcription Factors / metabolism*
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / metabolism
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / pathology*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ribosomal Protein S6 Kinases / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • TOR Serine-Threonine Kinases / metabolism
  • Xenograft Model Antitumor Assays


  • Antineoplastic Agents
  • Calcineurin Inhibitors
  • Heterocyclic Compounds, 3-Ring
  • MK 2206
  • NFATC Transcription Factors
  • Cyclosporine
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases
  • Calcineurin
  • PPP3CA protein, human