Raptinal bypasses BAX, BAK, and BOK for mitochondrial outer membrane permeabilization and intrinsic apoptosis

Cell Death Dis. 2019 Jul 19;10(8):556. doi: 10.1038/s41419-019-1790-z.

Abstract

Most antineoplastic chemotherapies eliminate cancer cells through activation of the mitochondria-controlled intrinsic apoptotic pathway. Therein, BAX, BAK, and/or BOK function as the essential pore-forming executioners of mitochondrial outer membrane permeabilization (MOMP). The activation threshold of BAX and BAK also correlates inversely with the required strength of an apoptotic stimulus to induce MOMP and thereby effectively determines a cell's readiness to undergo apoptosis. Consequently, the 'gatekeepers' BAX and BAK emerged as therapeutic targets, but functional or genetic loss renders BAX/BAK-targeting strategies prone to fail. Here, we show that the small molecule Raptinal overcomes this limitation by triggering cytochrome c release in a BAX/BAK/BOK-independent manner. Raptinal exerts a dual cytotoxic effect on cancer cells by rapid activation of the intrinsic apoptotic pathway and simultaneous shutdown of mitochondrial function. Together with its efficacy to eliminate cancer cells in vivo, Raptinal could be useful in difficult-to-treat cancer entities harboring defects in the intrinsic apoptosis pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Cyclopentanes / pharmacology*
  • Cyclopentanes / therapeutic use
  • Cytochromes c / metabolism
  • Fluorenes / pharmacology*
  • Fluorenes / therapeutic use
  • HCT116 Cells
  • Humans
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Mitochondrial Membranes / metabolism*
  • Neoplasms / drug therapy
  • Neoplasms / metabolism*
  • Neoplasms / pathology
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Signal Transduction / drug effects
  • bcl-2 Homologous Antagonist-Killer Protein / genetics
  • bcl-2 Homologous Antagonist-Killer Protein / metabolism*
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism*

Substances

  • BAK1 protein, human
  • BAX protein, human
  • BOK protein, human
  • Cyclopentanes
  • Fluorenes
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • raptinal
  • Cytochromes c