title: Proteasome inhibitor PS-341 induces apoptosis in cisplatin-resistant squamous cell carcinoma cells by induction of Noxa.
abstract: Cisplatin is one of the most common DNA-damaging agents used for treating patients with solid tumors such as squamous cell carcinoma (SCC). Unfortunately, significant levels of resistance in SCC cells emerge rapidly following cisplatin treatment. Here we report that the proteasome inhibitor PS-341, the representative of a new class of chemotherapeutic drugs, was capable of inducing apoptosis in cisplatin-resistant SCC cells via the endoplasmic reticulum stress. PS-341 stimulated the phosphorylation of PERK and the unfolded protein response, resulting in the induction of the transcription factor ATF-4. Importantly, the Bcl-2 homology domain 3-only (BH3-only) protein Noxa was found to be strongly induced in cisplatin-resistant SCC cells by PS-341 but not by cisplatin. The knock-down of Noxa using small interference RNA significantly abolished PS-341-mediated apoptosis in SCC cells. Using eIF2alpha mutant mouse embryonic fibroblasts, we found that functional eIF2alpha played an essential role in PS-341-induced Noxa expression. Taken together, our novel findings reveal a direct link between PS-341-induced endoplasmic reticulum stress and the mitochondria-dependent apoptotic pathway and suggest that PS-341 may be utilized for overcoming cisplatin-resistance in human SCC.
authors.affiliation: Laboratory of Molecular Signaling and Apoptosis, Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, MI 48109-1078, USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Fribley
authors.forename: Benjamin
authors.initials: B
authors.lastname: Evenchik
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zeng
authors.forename: Bae Keun
authors.initials: BK
authors.lastname: Park
authors.forename: Jean Y
authors.initials: JY
authors.lastname: Guan
authors.forename: Honglai
authors.initials: H
authors.lastname: Zhang
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Hale
authors.forename: Maria S
authors.initials: MS
authors.lastname: Soengas
authors.forename: Randal J
authors.initials: RJ
authors.lastname: Kaufman
authors.forename: Cun-Yu
authors.initials: CY
authors.lastname: Wang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D015852:Eukaryotic Initiation Factor-2; C408009:Pmaip1 protein, mouse; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; D000069286:Bortezomib; D002945:Cisplatin