Direct and inverted DNA repeats associated with P-glycoprotein gene amplification in drug resistant Leishmania.

Multiple drug resistance (MDR), consisting of acquired cross resistance to anthracyclines, vinca alkyloids, and other antineoplastic antibiotics, has been described in a variety of cell lines. This MDR phenotype is associated with overexpression and sometimes amplification of a gene coding for a 170 kDa glycoprotein, termed P-glycoprotein. To understand the role of this mechanism in clinical breast cancer, 248 breast cancer specimens representing both untreated primary and refractory relapsing disease were probed for evidence of P-glycoprotein gene amplification or overexpression using Southern, Northern, or Western blot techniques. In no case was an increase in P-glycoprotein gene copy number or expression detected. Though these findings do not necessarily rule out a role for P-glycoprotein in mediating drug resistance in breast cancer, electrophoretic analysis of clinical specimens is unlikely to provide useful predictive information. More sensitive assays must be developed to overcome the difficulties inherent in analyzing heterogenous tissue samples.

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Chromosome breakage at a major fragile site associated with P-glycoprotein gene amplification in multidrug-resistant CHO cells

Molecular and Cellular Biology ◽

10.1128/mcb.14.8.5202-5211.1994 ◽

1994 ◽

Vol 14 (8) ◽

pp. 5202-5211

Author(s):

M T Kuo ◽

R C Vyas ◽

L X Jiang ◽

W N Hittelman

Keyword(s):

Gene Amplification ◽

Cho Cells ◽

Mammalian Cells ◽

Fragile Site ◽

Dna Amplification ◽

Chromosome Breakage ◽

Multidrug Resistant ◽

Cytotoxic Agents ◽

Drug Resistant ◽

P Glycoprotein

Recent studies of several drug-resistant Chinese hamster cell lines suggested that a breakage-fusion-bridge mechanism is frequently involved in the amplification of drug resistance genes. These observations underscore the importance of chromosome breakage in the initiation of DNA amplification in mammalian cells. However, the mechanism of this breakage is unknown. Here, we propose that the site of chromosome breakage consistent with the initial event of P-glycoprotein (P-gp) gene amplification via the breakage-fusion-bridge cycle in three independently established multidrug-resistant CHO cells was located at 1q31. This site is a major chromosome fragile site that can be induced by methotrexate and aphidicolin treatments. Pretreatments of CHO cells with methotrexate or aphidicolin enhanced the frequencies of resistance to vinca alkaloid and amplification of the P-gp gene. These observations suggest that chromosome fragile sites play a pivotal role in DNA amplification in mammalian cells. Our data are also consistent with the hypothesis that gene amplification can be initiated by stress-induced chromosome breakage that is independent of modes of action of cytotoxic agents. Drug-resistant variants may arise by their growth advantage due to overproduction of cellular target molecules via gene amplification.

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Chromosome breakage at a major fragile site associated with P-glycoprotein gene amplification in multidrug-resistant CHO cells.

Molecular and Cellular Biology ◽

10.1128/mcb.14.8.5202 ◽

1994 ◽

Vol 14 (8) ◽

pp. 5202-5211 ◽

Cited By ~ 50

Author(s):

M T Kuo ◽

R C Vyas ◽

L X Jiang ◽

W N Hittelman

Keyword(s):

Gene Amplification ◽

Cho Cells ◽

Mammalian Cells ◽

Fragile Site ◽

Dna Amplification ◽

Chromosome Breakage ◽

Multidrug Resistant ◽

Cytotoxic Agents ◽

Drug Resistant ◽

P Glycoprotein

Recent studies of several drug-resistant Chinese hamster cell lines suggested that a breakage-fusion-bridge mechanism is frequently involved in the amplification of drug resistance genes. These observations underscore the importance of chromosome breakage in the initiation of DNA amplification in mammalian cells. However, the mechanism of this breakage is unknown. Here, we propose that the site of chromosome breakage consistent with the initial event of P-glycoprotein (P-gp) gene amplification via the breakage-fusion-bridge cycle in three independently established multidrug-resistant CHO cells was located at 1q31. This site is a major chromosome fragile site that can be induced by methotrexate and aphidicolin treatments. Pretreatments of CHO cells with methotrexate or aphidicolin enhanced the frequencies of resistance to vinca alkaloid and amplification of the P-gp gene. These observations suggest that chromosome fragile sites play a pivotal role in DNA amplification in mammalian cells. Our data are also consistent with the hypothesis that gene amplification can be initiated by stress-induced chromosome breakage that is independent of modes of action of cytotoxic agents. Drug-resistant variants may arise by their growth advantage due to overproduction of cellular target molecules via gene amplification.

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P-glycoprotein gene amplification and expression in multidrug-resistant murine P388 and B16 cell lines

British Journal of Cancer ◽

10.1038/bjc.1989.141 ◽

1989 ◽

Vol 59 (5) ◽

pp. 682-685 ◽

Cited By ~ 11

Author(s):

G Capranico ◽

P De Isabella ◽

C Castelli ◽

R Supino ◽

G Parmiani ◽

...

Keyword(s):

Cell Lines ◽

Gene Amplification ◽

Multidrug Resistant ◽

Glycoprotein Gene ◽

P Glycoprotein

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Increased Frequency of P-Glycoprotein Gene Amplification in Colchicine-Resistant Rat-1 Clones Transformed by v-src

Cancer Genetics and Cytogenetics ◽

10.1016/s0165-4608(96)00324-x ◽

1997 ◽

Vol 96 (2) ◽

pp. 157-165 ◽

Cited By ~ 2

Author(s):

Ti Lin ◽

Jeffrey M Trent ◽

Dina Milliken ◽

David S Shimm ◽

Robert Donaldson ◽

...

Keyword(s):

Gene Amplification ◽

Glycoprotein Gene ◽

P Glycoprotein

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Identification of members of the P-glycoprotein multigene family.

Molecular and Cellular Biology ◽

10.1128/mcb.9.3.1224 ◽

1989 ◽

Vol 9 (3) ◽

pp. 1224-1232 ◽

Cited By ~ 146

Author(s):

W F Ng ◽

F Sarangi ◽

R L Zastawny ◽

L Veinot-Drebot ◽

V Ling

Keyword(s):

Multidrug Resistance ◽

Gene Duplication ◽

Gene Family ◽

Multigene Family ◽

Rhesus Monkeys ◽

Genomic Library ◽

Duplication Event ◽

Glycoprotein Gene ◽

P Glycoprotein ◽

Exon Probe

Overproduction of P-glycoprotein is intimately associated with multidrug resistance. This protein appears to be encoded by a multigene family. Thus, differential expression of different members of this family may contribute to the complexity of the multidrug resistance phenotype. Three lambda genomic clones isolated from a hamster genomic library represent different members of the hamster P-glycoprotein gene family. Using a highly conserved exon probe, we found that the hamster P-glycoprotein gene family consists of three genes. We also found that the P-glycoprotein gene family consists of three genes in mice but has only two genes in humans and rhesus monkeys. The hamster P-glycoprotein genes have similar exon-intron organizations within the 3' region encoding the cytoplasmic domains. We propose that the hamster P-glycoprotein gene family arose from gene duplication. The hamster pgp1 and pgp2 genes appear to be more closely related to each other than either gene is to the pgp3 gene. We speculate that the hamster pgp1 and pgp2 genes arose from a recent gene duplication event and that primates did not undergo this duplication and therefore contain only two P-glycoprotein genes.

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