GDC-0941 enhances the lysosomal compartment via TFEB and primes glioblastoma cells to lysosomal membrane permeabilization and cell death.

Abstract

Since phosphatidylinositol-3-kinase (PI3K) inhibitors are primarily cytostatic against glioblastoma, we searched for new drug combinations. Here, we discover that the PI3K inhibitor GDC-0941 acts in concert with the natural compound B10, a glycosylated derivative of betulinic acid, to induce cell death in glioblastoma cells. Importantly, parallel experiments in primary glioblastoma cultures similarly show that GDC-0941 and B10 cooperate to trigger cell death, underscoring the clinical relevance of this finding. Molecular studies revealed that treatment with GDC-0941 stimulates the expression and nuclear translocation of Transcription Factor EB (TFEB), a master regulator of lysosomal biogenesis, the lysosomal membrane marker LAMP-1 and the mature form of cathepsin B. Also, GDC-0941 triggers a time-dependent increase of the lysosomal compartment in a TFEB-dependent manner, since knockdown of TFEB significantly reduces this GDC-0941-stimulated lysosomal enhancement. Importantly, GDC-0941 cooperates with B10 to trigger lysosomal membrane permeabilization, leading to increased activation of Bax, loss of mitochondrial membrane potential (MMP), caspase-3 activation and cell death. Addition of the cathepsin B inhibitor CA-074me reduces Bax activation, loss of MMP, caspase-3 activation and cell death upon treatment with GDC-0941/B10. By comparison, knockdown of caspase-3 or the broad-range caspase inhibitor zVAD.fmk inhibits GDC-0941/B10-induced DNA fragmentation, but does not prevent cell death, thus pointing to both caspase-dependent and -independent pathways. By identifying the combination of GDC-0941 and B10 as a new, potent strategy to trigger cell death in glioblastoma cells, our findings have important implications for the development of novel treatment approaches for glioblastoma.

• Authors: Stefanie Enzenmüller, Patrick Gonzalez, Georg Karpel-Massler, Klaus-Michael Debatin, Simone Fulda
• Journal: Cancer letters (Cancer Lett) Vol. 329 Issue 1 Pg. 27-36 (Feb 01 2013) ISSN: 1872-7980 [Electronic] Ireland
• PMID: 23000516 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012. Published by Elsevier Ireland Ltd.

Chemical References

• 2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine
• BAX protein, human
• Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
• Indazoles
• Pentacyclic Triterpenes
• Sulfonamides
• TFEB protein, human
• Triterpenes
• bcl-2-Associated X Protein
• Caspase 3
• Matrix Metalloproteinases
• Betulinic Acid

Topics

• Basic Helix-Loop-Helix Leucine Zipper Transcription Factors (genetics, metabolism)
• Caspase 3 (metabolism)
• Cell Death (drug effects)
• Cell Line, Tumor
• Central Nervous System Neoplasms (drug therapy, metabolism, pathology)
• Glioblastoma (drug therapy, metabolism, pathology)
• Humans
• Indazoles (pharmacology)
• Intracellular Membranes (drug effects)
• Lysosomes (drug effects, metabolism)
• Matrix Metalloproteinases
• Pentacyclic Triterpenes
• Permeability
• Sulfonamides (pharmacology)
• Triterpenes (pharmacology)
• bcl-2-Associated X Protein (metabolism)
• Betulinic Acid