Targeting of X-linked inhibitor of apoptosis protein and PI3-kinase/AKT signaling by embelin suppresses growth of leukemic cells

PLoS One. 2017 Jul 13;12(7):e0180895. doi: 10.1371/journal.pone.0180895. eCollection 2017.

Abstract

The X-linked inhibitor of apoptosis (XIAP) is a viable molecular target for anticancer drugs that overcome apoptosis-resistance of malignant cells. XIAP is an inhibitor of apoptosis, mediating through its association with BIR3 domain of caspase 9. Embelin, a quinone derivative isolated from the Embelia ribes plant, has been shown to exhibit chemopreventive, anti-inflammatory, and apoptotic activities via inhibiting XIAP activity. In this study, we found that embelin causes a dose-dependent suppression of proliferation in leukemic cell lines K562 and U937. Embelin mediated inhibition of proliferation correlates with induction of apoptosis. Furthermore, embelin treatment causes loss of mitochondrial membrane potential and release of cytochrome c, resulting in subsequent activation of caspase-3 followed by polyadenosin-5'-diphosphate-ribose polymerase (PARP) cleavage. In addition, embelin treatment of leukemic cells results in a decrease of constitutive phosphorylations/activation level of AKT and downregulation of XIAP. Gene silencing of XIAP and AKT expression showed a link between XIAP expression and activated AKT in leukemic cells. Interestingly, targeting of XIAP and PI3-kinase/AKT signaling augmented inhibition of proliferation and induction of apoptosis in leukemic cells. Altogether these findings raise the possibility that embelin alone or in combination with inhibitors of PI3-kinase/AKT pathway may have therapeutic usage in leukemia and possibly other malignancies with up-regulated XIAP pathway.

MeSH terms

  • Benzoquinones / pharmacology*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Chromones / pharmacology*
  • Drug Synergism
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • K562 Cells
  • Leukemia / drug therapy
  • Leukemia / metabolism*
  • Membrane Potential, Mitochondrial / drug effects
  • Mitochondria / drug effects
  • Morpholines / pharmacology*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Signal Transduction / drug effects
  • X-Linked Inhibitor of Apoptosis Protein / metabolism*

Substances

  • Benzoquinones
  • Chromones
  • Morpholines
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt
  • embelin

Grants and funding

This study was supported by a grant from the Medical Research Center, Hamad Medical Corporation, Doha, Qatar (Grant # 16102/16).