Inhibition of Gamma-Secretase Induces G2/M Arrest and Triggers Apoptosis in Breast Cancer Cells

Br J Cancer. 2009 Jun 16;100(12):1879-88. doi: 10.1038/sj.bjc.6605034.

Abstract

Gamma-secretase activity is vital for the transmembrane cleavage of Notch receptors and the subsequent migration of their intracellular domains to the nucleus. Notch overexpression has been associated with breast, colon, cervical and prostate cancers. We tested the effect of three different gamma-secretase inhibitors (GSIs) in breast cancer cells. One inhibitor (GSI1) was lethal to breast cancer cell lines at concentrations of 2 muM and above but had a minimal effect on the non-malignant breast lines. GSI1 was also cytotoxic for a wide variety of cancer cell lines in the NCI60 cell screen. GSI1 treatment resulted in a marked decrease in gamma-secretase activity and downregulation of the Notch signalling pathway with no effects on expression of the gamma-secretase components or ligands. Flow cytometric and western blot analyses indicated that GSI1 induces a G2/M arrest leading to apoptosis, through downregulation of Bcl-2, Bax and Bcl-XL. GSI1 also inhibited proteasome activity. Thus, the gamma-secretase inhibitor GSI1 has a complex mode of action to inhibit breast cancer cell survival and may represent a novel therapy in breast cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid Precursor Protein Secretases / antagonists & inhibitors*
  • Amyloid Precursor Protein Secretases / metabolism
  • Apoptosis / drug effects*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology*
  • Cell Division / drug effects*
  • Cell Proliferation / drug effects
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Flow Cytometry
  • G2 Phase / drug effects*
  • Humans
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Notch / genetics
  • Receptors, Notch / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Cells, Cultured
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism

Substances

  • Enzyme Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • Receptors, Notch
  • bcl-2-Associated X Protein
  • Amyloid Precursor Protein Secretases