High-throughput drug screen identifies chelerythrine as a selective inducer of death in a TSC2-null setting

Mol Cancer Res. 2015 Jan;13(1):50-62. doi: 10.1158/1541-7786.MCR-14-0440. Epub 2014 Sep 3.

Abstract

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome associated with tumors of the brain, heart, kidney, and lung. The TSC protein complex inhibits the mammalian or mechanistic target of rapamycin complex 1 (mTORC1). Inhibitors of mTORC1, including rapamycin, induce a cytostatic response in TSC tumors, resulting in temporary disease stabilization and prompt regrowth when treatment is stopped. The lack of TSC-specific cytotoxic therapies represents an important unmet clinical need. Using a high-throughput chemical screen in TSC2-deficient, patient-derived cells, we identified a series of molecules antagonized by rapamycin and therefore selective for cells with mTORC1 hyperactivity. In particular, the cell-permeable alkaloid chelerythrine induced reactive oxygen species (ROS) and depleted glutathione (GSH) selectively in TSC2-null cells based on metabolic profiling. N-acetylcysteine or GSH cotreatment protected TSC2-null cells from chelerythrine's effects, indicating that chelerythrine-induced cell death is ROS dependent. Induction of heme-oxygenase-1 (HMOX1/HO-1) with hemin also blocked chelerythrine-induced cell death. In vivo, chelerythrine inhibited the growth of TSC2-null xenograft tumors with no evidence of systemic toxicity with daily treatment over an extended period of time. This study reports the results of a bioactive compound screen and the identification of a potential lead candidate that acts via a novel oxidative stress-dependent mechanism to selectively induce necroptosis in TSC2-deficient tumors.

Implications: This study demonstrates that TSC2-deficient tumor cells are hypersensitive to oxidative stress-dependent cell death, and provide critical proof of concept that TSC2-deficient cells can be therapeutically targeted without the use of a rapalog to induce a cell death response.

Publication types

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

MeSH terms

  • Benzophenanthridines / administration & dosage*
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Drug Screening Assays, Antitumor*
  • Glutathione / genetics
  • Heme Oxygenase-1 / genetics
  • Humans
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Oxidative Stress / drug effects
  • Reactive Oxygen Species / metabolism
  • Sirolimus / administration & dosage
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism
  • Tuberous Sclerosis / complications
  • Tuberous Sclerosis / drug therapy*
  • Tuberous Sclerosis / pathology
  • Tuberous Sclerosis Complex 2 Protein
  • Tumor Suppressor Proteins / antagonists & inhibitors
  • Tumor Suppressor Proteins / biosynthesis
  • Tumor Suppressor Proteins / genetics*

Substances

  • Benzophenanthridines
  • Multiprotein Complexes
  • Reactive Oxygen Species
  • TSC2 protein, human
  • Tuberous Sclerosis Complex 2 Protein
  • Tumor Suppressor Proteins
  • chelerythrine
  • Heme Oxygenase-1
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Glutathione
  • Sirolimus