Gamma secretase inhibitor blocks Notch activation and induces apoptosis in Kaposi's sarcoma tumor cells

Oncogene. 2005 Sep 22;24(42):6333-44. doi: 10.1038/sj.onc.1208783.


Kaposi's sarcoma (KS) is a common neoplasm in HIV-1-infected individuals causing significant morbidity and mortality. Despite recent advances, the pathogenesis of this potentially life-threatening neoplasm remains unclear, and there is currently no cure for KS. Notch proteins are known to play a fundamental role in cell fate decisions including proliferation, differentiation, and apoptosis. It is, therefore, not surprising that Notch proteins have been implicated in tumorigenesis and appear to function as either oncogenes or tumor suppressor proteins depending on cellular context. In this report, we demonstrate elevated levels of activated Notch-1, -2, and -4 in KS tumor cells in vivo and in vitro compared to endothelial cells, the precursor of the KS cell. Notch activation was confirmed through luciferase reporter assays and localization of Hes (Hairy/Enhancer of Split)-1 and Hey (Hairy/Enhancer of Split related with YRPW)1 (primary targets of the Notch pathway) in KS cell nuclei. Studies using gamma-secretase inhibitors (GSI and LY-411,575), which block Notch activation, resulted in apoptosis in primary and immortalized KS cells. Similar studies injecting GSI into established KS cell tumors on mice demonstrated growth inhibition or tumor regression that was characterized by apoptosis in treated, but not control tumors. The results indicate that KS cells overexpress activated Notch and interruption of Notch signaling inhibits KS cell growth. Thus, targeting Notch signaling may be of therapeutic value in KS patients.

Publication types

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

MeSH terms

  • Amyloid Precursor Protein Secretases
  • Apoptosis / drug effects*
  • Aspartic Acid Endopeptidases / antagonists & inhibitors*
  • Blotting, Western
  • Endopeptidases
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Membrane Proteins / metabolism*
  • Plasmids
  • Receptors, Notch
  • Sarcoma, Kaposi / metabolism*
  • Sarcoma, Kaposi / pathology


  • Enzyme Inhibitors
  • Membrane Proteins
  • Receptors, Notch
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Aspartic Acid Endopeptidases
  • BACE1 protein, human