title: Molecular cloning of cDNAs which are highly overexpressed in mitoxantrone-resistant cells: demonstration of homology to ABC transport genes.
abstract: Reports of multiple distinct mitoxantrone-resistant sublines without overexpression of P-glycoprotein or the multidrug-resistance associated protein have raised the possibility of the existence of another major transporter conferring drug resistance. In the present study, a cDNA library from mitoxantrone-resistant S1-M1-80 human colon carcinoma cells was screened by differential hybridization. Two cDNAs of different lengths were isolated and designated MXR1 and MXR2. Sequencing revealed a high degree of homology for the cDNAs with Expressed Sequence Tag sequences previously identified as belonging to an ATP binding cassette transporter. Homology to the Drosophila white gene and its homologues was found for the predicted amino acid sequence. Using either cDNA as a probe in a Northern analysis demonstrated high levels of expression in the S1-M1-80 cells and in the human breast cancer subline, MCF-7 AdVp3000. Levels were lower in earlier steps of selection, and in partial revertants. The gene is amplified 10-12-fold in the MCF-7 AdVp3000 cells, but not in the S1-M1-80 cells These studies are consistent with the identification of a new ATP binding cassette transporter, which is overexpressed in mitoxantrone-resistant cells.
authors.affiliation: Medicine Branch, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
authors.forename: K
authors.initials: K
authors.lastname: Miyake
authors.forename: L
authors.initials: L
authors.lastname: Mickley
authors.forename: T
authors.initials: T
authors.lastname: Litman
authors.forename: Z
authors.initials: Z
authors.lastname: Zhan
authors.forename: R
authors.initials: R
authors.lastname: Robey
authors.forename: B
authors.initials: B
authors.lastname: Cristensen
authors.forename: M
authors.initials: M
authors.lastname: Brangi
authors.forename: L
authors.initials: L
authors.lastname: Greenberger
authors.forename: M
authors.initials: M
authors.lastname: Dean
authors.forename: T
authors.initials: T
authors.lastname: Fojo
authors.forename: S E
authors.initials: SE
authors.lastname: Bates
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics* / Q000302:isolation & purification; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008942:Mitoxantrone / Q000494:pharmacology*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D014407:Tumor Cells, Cultured
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D018076:DNA, Complementary; D008942:Mitoxantrone