title: A very early induction of major vault protein accompanied by increased drug resistance in U-937 cells.
abstract: U-937 human leukemia cells were selected for resistance to doxorubicin in the presence or absence of a specific drug modulator that inhibits the activity of P-glycoprotein (Pgp), encoded by the multidrug-resistance gene (MDR1). Parental cells expressed low basal levels of the multidrug-resistance-associated gene (MRP1) and major vault protein (MVP) mRNAs and no MDR1 mRNA. Two doxorubicin-resistant cell lines were selected. Both drug-resistant cell lines upregulated the MVP mRNA level 1.5-fold within 1 cell passage. The MVP mRNA level continued to increase over time as the doxorubicin selection pressure was increased. MVP protein levels generally paralleled the mRNA levels. The 2 high molecular weight vault protein mRNAs were always expressed at constitutive levels. Fully formed vault particles consisting of the MVP, the 2 high molecular weight proteins and the vault RNA assembled and accumulated to increased levels in drug-selected cells. MVP induction is therefore the rate-limiting step for vault particle formation in U-937 cells. By passage 25 and thereafter, the selected cells were resistant to doxorubicin, etoposide, mitoxantrone and 5-fluorouracil by a pathway that was independent of MDR1, MRP1, MRP2 and breast cancer resistance protein. In summary, U-937 doxorubicin-selected cells are programmed to rapidly upregulate MVP mRNA levels, to accumulate vault particles and to become multidrug resistant.
authors.affiliation: Eli Lilly and Company, Department of Cancer Research, Lilly Corporate Center, drop code 0424, Indianapolis, IN 46285, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hu
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Stephen
authors.forename: Jin
authors.initials: J
authors.lastname: Cao
authors.forename: Lee R
authors.initials: LR
authors.lastname: Tanzer
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Slapak
authors.forename: Steadman D
authors.initials: SD
authors.lastname: Harrison
authors.forename: Viswanath
authors.initials: V
authors.lastname: Devanarayan
authors.forename: Anne H
authors.initials: AH
authors.lastname: Dantzig
authors.forename: James J
authors.initials: JJ
authors.lastname: Starling
authors.forename: Leonard H
authors.initials: LH
authors.lastname: Rome
authors.forename: Robert E
authors.initials: RE
authors.lastname: Moore
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002451:Cell Compartmentation; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D018869:Heat-Shock Response; D006358:Hot Temperature; D006801:Humans; D024101:Mitochondrial Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000378:metabolism; D012334:RNA, Neoplasm / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D020298:U937 Cells / Q000187:drug effects* / Q000378:metabolism; D015854:Up-Regulation; D020394:Vault Ribonucleoprotein Particles / Q000096:biosynthesis* / Q000235:genetics; D000099187:Major Vault Protein
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D004317:Doxorubicin; D024101:Mitochondrial Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein; C116614:ABCG2 protein, human; C093947:MRP2 protein, S cerevisiae; C421109:multidrug resistance-associated protein 1