title: 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.affiliation: University Children's Hospital, Ulm University, Eythstrasse 24, Ulm, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Enzenmüller
authors.forename: Patrick
authors.initials: P
authors.lastname: Gonzalez
authors.forename: Georg
authors.initials: G
authors.lastname: Karpel-Massler
authors.forename: Klaus-Michael
authors.initials: KM
authors.lastname: Debatin
authors.forename: Simone
authors.initials: S
authors.lastname: Fulda
mesh_terms: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D016543:Central Nervous System Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D005909:Glioblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007191:Indazoles / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D020782:Matrix Metalloproteinases; D053978:Pentacyclic Triterpenes; D010539:Permeability; D013449:Sulfonamides / Q000494:pharmacology*; D014315:Triterpenes / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D000094062:Betulinic Acid
chemical_list: C532162:2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine; C494826:BAX protein, human; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D007191:Indazoles; D053978:Pentacyclic Triterpenes; D013449:Sulfonamides; C064972:TFEB protein, human; D014315:Triterpenes; D051028:bcl-2-Associated X Protein; D053148:Caspase 3; D020782:Matrix Metalloproteinases; D000094062:Betulinic Acid