BCL-2 family inhibitors enhance histone deacetylase inhibitor and sorafenib lethality via autophagy and overcome blockade of the extrinsic pathway to facilitate killing

Mol Pharmacol. 2009 Aug;76(2):327-41. doi: 10.1124/mol.109.056309. Epub 2009 May 29.

Abstract

We examined whether the multikinase inhibitor sorafenib and histone deacetylase inhibitors (HDACI) interact to kill pancreatic carcinoma cells and determined the impact of inhibiting BCL-2 family function on sorafenib and HDACI lethality. The lethality of sorafenib was enhanced in pancreatic tumor cells in a synergistic fashion by pharmacologically achievable concentrations of the HDACIs vorinostat or sodium valproate. Overexpression of cellular FLICE-like inhibitory protein (c-FLIP-s) or knockdown of CD95 suppressed the lethality of the sorafenib/HDACI combination (sorafenib + HDACI). In immunohistochemical analyses or using expression of fluorescence-tagged proteins, treatment with sorafenib and vorinostat together (sorafenib + vorinostat) promoted colocalization of CD95 with caspase 8 and CD95 association with the endoplasmic reticulum markers calnexin, ATG5, and Grp78/BiP. In cells lacking CD95 expression or in cells expressing c-FLIP-s, the lethality of sorafenib + HDACI exposure was abolished and was restored when cells were coexposed to BCL-2 family inhibitors [ethyl [2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)]-4H-chromene-3-carboxylate (HA14-1), obatoclax (GX15-070)]. Knockdown of BCL-2, BCL-XL, and MCL-1 recapitulated the effects of GX15-070 treatment. Knockdown of BAX and BAK modestly reduced sorafenib + HDACI lethality but abolished the effects of GX15-070 treatment. Sorafenib + HDACI exposure generated a CD95- and Beclin1-dependent protective form of autophagy, whereas GX15-070 treatment generated a Beclin1-dependent toxic form of autophagy. The potentiation of sorafenib + HDACI killing by GX15-070 was suppressed by knockdown of Beclin1 or of BAX + BAK. Our data demonstrate that pancreatic tumor cells are susceptible to sorafenib + HDACI lethality and that in tumor cells unable to signal death from CD95, use of a BCL-2 family antagonist facilitates sorafenib + HDACI killing via autophagy and the intrinsic pathway.

Publication types

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

MeSH terms

  • Adenoviridae / genetics
  • Antineoplastic Agents / pharmacology*
  • Autophagy / drug effects*
  • Benzenesulfonates / pharmacology*
  • CASP8 and FADD-Like Apoptosis Regulating Protein / metabolism
  • Cell Line, Transformed
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Drug Synergism
  • Endoplasmic Reticulum Chaperone BiP
  • Enzyme Inhibitors / metabolism*
  • Histone Deacetylase Inhibitors*
  • Humans
  • Immunohistochemistry
  • Niacinamide / analogs & derivatives
  • Phenylurea Compounds
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors*
  • Pyridines / pharmacology*
  • RNA, Small Interfering / metabolism
  • Sorafenib
  • Transfection
  • fas Receptor / metabolism

Substances

  • Antineoplastic Agents
  • Benzenesulfonates
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Endoplasmic Reticulum Chaperone BiP
  • Enzyme Inhibitors
  • HSPA5 protein, human
  • Histone Deacetylase Inhibitors
  • Phenylurea Compounds
  • Proto-Oncogene Proteins c-bcl-2
  • Pyridines
  • RNA, Small Interfering
  • fas Receptor
  • Niacinamide
  • Sorafenib