title: Silencing of prion protein sensitizes breast adriamycin-resistant carcinoma cells to TRAIL-mediated cell death.
abstract: We investigated the relationship between the resistance to the proapoptotic action of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and cellular prion protein (PrPc) function, using the TRAIL-sensitive MCF-7 human breast adenocarcinoma cell line and two TRAIL-resistant sublines: 2101 and MCF-7/ADR. All of the cell lines tested expressed TRAIL-R1 and TRAIL-R2. TRAIL decoy receptors were not detected, suggesting that the resistance of 2101 and MCF-7/ADR cells, strongly expressing PrPc, to TRAIL-mediated cell death was independent from the expression of TRAIL receptors and death-inducing signaling complex formation. Down-regulation of PrPc by small interfering RNA increased the sensitivity of Adriamycin- and TRAIL-resistant cells to TRAIL, but not to epirubicin/Adriamycin. TRAIL-mediated apoptosis in PrPc knocked-down cells was associated with caspase processing, Bid cleavage, and Mcl-1 degradation. In addition, an increased sensitivity of apoptosis-resistant cells to TRAIL after PrPc silencing was not associated with the increased recruitment of receptors and intracellular signaling molecule to the death-inducing signaling complex. Bcl-2 expression was substantially decreased after PrPc knock-down but the levels of Bcl-X(L) and Mcl-1 were not affected. The down-regulation of Bcl-2 was concomitant with Bax delocalization. Our findings support the notion that silencing of PrPc facilitates the activation of proapoptotic Bax by down-regulation of Bcl-2 expression, thereby abolishing the resistance of breast cancer cells to TRAIL-induced apoptosis.
authors.affiliation: INSERM U753, Laboratoire d'Immunologie des Tumeurs Humaines, Interaction Effecteurs Cytotoxiques-Système Tumoral, Institut Gustave Roussy PR1 and IFR 54, Villejuif, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Meslin
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hamaï
authors.forename: Ping
authors.initials: P
authors.lastname: Gao
authors.forename: Abdelali
authors.initials: A
authors.lastname: Jalil
authors.forename: Nathalie
authors.initials: N
authors.lastname: Cahuzac
authors.forename: Salem
authors.initials: S
authors.lastname: Chouaib
authors.forename: Maryam
authors.initials: M
authors.lastname: Mehrpour
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D002277:Carcinoma / Q000188:drug therapy* / Q000473:pathology*; D016923:Cell Death; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D020868:Gene Silencing; D006801:Humans; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D011328:Prions / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D011328:Prions; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; D051020:bcl-X Protein; D004317:Doxorubicin