title: Silencing of cellular prion protein (PrPC) expression by DNA-antisense oligonucleotides induces autophagy-dependent cell death in glioma cells.
abstract: Malignant gliomas are the most common and lethal primary central nervous system neoplasms. Several intriguing lines of evidence have recently emerged indicating that the cellular prion protein (PrPC) may exert neuro- and cyto-protective functions: PrPC overexpression protects cultured neurons and also tumor cell lines exposed to various pro-apoptotic stimuli while, on the contrary, PrPC silencing sensitizes Adriamycin-resistant human breast carcinoma cells to TRAIL-mediated cell death. In order to determine if PrPC is involved in the resistance of glial tumors to cell death, the effects of cellular prion protein downregulation by antisense approach were investigated in different human malignant glioma cell lines. PrPC downregulation induced profound morphological changes and significant cell death. In addition, a significant tumor volume reduction was noted after PrPC silencing in a EGFP-GL261 glioma murine model. Investigations of the molecular effects induced by PrPC silencing were carried out on T98G human glioma cells by analysing autophagic as well as typical apoptotic markers (nuclear morphology, caspase-3/7, p53 and PARP-1). The results indicated that apoptosis was not induced after PrPC downregulation while, on the contrary, electron microscopy analysis, and an accumulation of GFP-LC3-II in autophagosomal membranes of GFP-LC3 transfected cells, indicated a predominant activation of autophagy. PrPC silencing also led to induction of LC3-II, increase in Beclin-1 and a concomitant decrease in p62, Bcl-2 and in the phosphorylation of 4E-BP1, a target of mTOR autophagy signaling. In conclusion, our results show for the first time that interfering with the cellular prion protein expression could modulate autophagy-dependent cell death pathways in glial tumor cells.
authors.affiliation: Dipartimento di Genetica e Microbiologia, Università di Pavia, Pavia, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Barbieri
authors.forename: Silvia
authors.initials: S
authors.lastname: Palumbo
authors.forename: Konrad
authors.initials: K
authors.lastname: Gabrusiewicz
authors.forename: Alberto
authors.initials: A
authors.lastname: Azzalin
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Marchesi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Spedito
authors.forename: Marco
authors.initials: M
authors.lastname: Biggiogera
authors.forename: Elena
authors.initials: E
authors.lastname: Sbalchiero
authors.forename: Giuliano
authors.initials: G
authors.lastname: Mazzini
authors.forename: Clelia
authors.initials: C
authors.lastname: Miracco
authors.forename: Luigi
authors.initials: L
authors.lastname: Pirtoli
authors.forename: Bozena
authors.initials: B
authors.lastname: Kaminska
authors.forename: Sergio
authors.initials: S
authors.lastname: Comincini
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D004247:DNA / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects*; D005910:Glioma / Q000235:genetics / Q000473:pathology* / Q000648:ultrastructure; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D018621:PrPC Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D018621:PrPC Proteins; D012333:RNA, Messenger; D004247:DNA; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes