2-Methoxyestradiol-induced apoptosis in human leukemia cells proceeds through a reactive oxygen species and Akt-dependent process

Oncogene. 2005 May 26;24(23):3797-809. doi: 10.1038/sj.onc.1208530.

Abstract

The effects of 2-Methoxyestradiol (2ME)-induced apoptosis was examined in human leukemia cells (U937 and Jurkat) in relation to mitochondrial injury, oxidative damage, and perturbations in signaling pathways. 2ME induced apoptosis in these cells in a dose-dependent manner associated with release of mitochondrial proteins (cytochrome c, AIF), generation of reactive oxygen species (ROS), downregulation of Mcl-1 and XIAP, and inactivation (dephosphorylation) of Akt accompanied by activation of JNK. In these cells, enforced activation of Akt by a constitutively active myristolated Akt construct prevented 2ME-mediated mitochondrial injury, XIAP and Mcl-1 downregulation, JNK activation, and apoptosis, but not ROS generation. Conversely, 2ME lethality was potentiated by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. Furthermore, in U937 cells, the hydrogen peroxide scavenger catalase and a superoxide dismutase (SOD) mimetic, TBAP, blocked these events, as well as Akt inactivation. Interruption of the JNK pathway by pharmacologic or genetic (e.g. siRNA) means attenuated 2ME-induced mitochondrial injury, XIAP and Mcl-1 downregulation, and apoptosis. Collectively, these findings suggest a hierarchical model of 2ME-related apoptosis induction in human leukemia cells in which 2ME-induced oxidative injury represents a primary event resulting in Akt inactivation, leading, in turn, to JNK activation, and culminating in XIAP and Mcl-1 downregulation, mitochondrial injury, and apoptosis. They also suggest that in human leukemia cells, the Akt pathway plays a critical role in mediating the response to oxidative stress induced by 2ME.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 2-Methoxyestradiol
  • Anthracenes / pharmacology
  • Apoptosis / drug effects*
  • Chromones / pharmacology
  • Dose-Response Relationship, Drug
  • Estradiol / analogs & derivatives*
  • Estradiol / pharmacology*
  • Humans
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Jurkat Cells
  • Morpholines / pharmacology
  • Phosphatidylinositol 3-Kinases
  • Protein-Serine-Threonine Kinases / physiology*
  • Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-akt
  • Reactive Oxygen Species / metabolism*
  • U937 Cells
  • X-Linked Inhibitor of Apoptosis Protein

Substances

  • Anthracenes
  • Chromones
  • Morpholines
  • Proteins
  • Proto-Oncogene Proteins
  • Reactive Oxygen Species
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • pyrazolanthrone
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Estradiol
  • 2-Methoxyestradiol
  • Phosphatidylinositol 3-Kinases
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • JNK Mitogen-Activated Protein Kinases