title: Tipifarnib sensitizes cells to proteasome inhibition by blocking degradation of bortezomib-induced aggresomes.
abstract: In this report, we investigated the mechanism responsible for synergistic induction of myeloma cell apoptosis induced by the combination of tipifarnib and bortezomib. Immunofluorescence studies revealed that bortezomib alone resulted in an accumulation of puncta of ubiquitinated proteins that was further enhanced by the addition of tipifarnib. These data suggest inhibition of the degradation of bortezomib-induced aggresomes; and consistent with this possibility, we also observed an increase in p62SQSTM1 in cells treated with the combination. However, autophagy in these cells appears to be normal as LC3BII is present, and autophagic flux appears to be unaffected as demonstrated by the addition of bafilomycin A₁. Together, these data demonstrate that tipifarnib synergizes with bortezomib by inducing protein accumulation as a result of the uncoupling of the aggresome and autophagy pathways.
authors.affiliation: Winship Cancer Institute of Emory University, Department of Hematology and Medical Oncology, School of Medicine, Atlanta, GA, USA.
authors.forename: Ebenezer
authors.initials: E
authors.lastname: David
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Kaufman
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Flowers
authors.forename: Katherine
authors.initials: K
authors.lastname: Schafer-Hales
authors.forename: Claire
authors.initials: C
authors.lastname: Torre
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Adam I
authors.initials: AI
authors.lastname: Marcus
authors.forename: Shi-Yong
authors.initials: SY
authors.lastname: Sun
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Boise
authors.forename: Sagar
authors.initials: S
authors.lastname: Lonial
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000473:pathology; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D015363:Quinolones; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D001897:Boronic Acids; D061988:Proteasome Inhibitors; D011719:Pyrazines; D015363:Quinolones; D000069286:Bortezomib; C402769:tipifarnib