An altered pattern of cross-resistance in multidrug-resistant human cells results from spontaneous mutations in the mdr1 (P-glycoprotein) gene

Choi, Kwanghoon; Chen, Chang jie; Kriegler, Michael; Roninson, Igor B.

doi:10.1016/0092-8674(88)90568-5

Cited by 421 publications

(237 citation statements)

References 45 publications

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“…None of these sublines showed the preferential colchicine resistance of the KB-Cl cell line ( Table 1) that results from a specific amino acid change in the MDR1 protein (Choi et al, 1988). Therefore, during the initial colchicine selection, the mutations probably arose spontaneously on one of the extrachromosomal elements during the colchicine selection steps subsequent to the cloning of KB-ChR-8-5-11 but before the cloning of KB-ChR-8-5-11-24 (KB-Cl) (Figure 1, Selection 1).…”

Section: Discussionmentioning

confidence: 99%

Double minute chromosomes carrying the human multidrug resistance 1 and 2 genes are generated from the dimerization of submicroscopic circular DNAs in colchicine-selected KB carcinoma cells.

Schoenlein

Shen

Barrett

et al. 1992

MBoC

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This study characterizes amplified structures carrying the human multidrug resistance (MDR) genes in colchicine-selected multidrug resistant KB cell lines and strongly supports a model of gene amplification in which small circular extrachromosomal DNA elements generated from contiguous chromosomal DNA regions multimerize to form cytologically detectable double minute chromosomes (DMs). The human MDR1 gene encodes the 170-kDa Pglycoprotein, which is a plasma membrane pump for many structurally unrelated chemotherapeutic drugs. MDR1 and its homolog, MDR2, undergo amplification when KB cells are subjected to stepwise selection in increasing concentrations of colchicine. The structure of the amplification unit at each step of drug selection was characterized using both highvoltage gel electrophoresis and pulsed-field gel electrophoresis (PFGE) techniques. An 890-kb submicroscopic extrachromosomal circular DNA element carrying the MDR1 and MDR2 genes was detected in cell line KB-ChR-8-5-1 1, the earliest step in drug selection in which conventional Southern/hybridization analyses detected MDR gene amplification. When KB-ChR-8-5-11 was subjected to stepwise increases in colchicine, this circular DNA element dimerized as detected by PFGE with and without digestion with Not 1, which linearizes the 890-kb amplicon. This dimerization process, which also occurred at the next step of colchicine selection, resulted in the formation of cytologically detectable DMs revealed by analysis of Giemsa-stained metaphase spreads.

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Section: Discussionmentioning

confidence: 99%

Double minute chromosomes carrying the human multidrug resistance 1 and 2 genes are generated from the dimerization of submicroscopic circular DNAs in colchicine-selected KB carcinoma cells.

Schoenlein

Shen

Barrett

et al. 1992

MBoC

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“…They have been located in transmembrane domain (TM) 4 [3], TM6 [4][5][6], TM10 [3], TM11 [7][8][9], TM12 [5], and the first [10][11][12], second, and fourth cytoplasmic loops [12]. The residues located in these transmembrane domains have been considered to be involved in the binding and transporting mechanisms of P-glycoprotein.…”

Section: Introductionmentioning

confidence: 99%

Amino acid substitutions in the first transmembrane domain (TM1) of P‐glycoprotein that alter substrate specificity

et al. 1997

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“…KB-GRC1 cells theoretically differ from KB-3-1 cells only by expression of PGP following transfection of mdrl (Choi et al, 1988), and are 67, 9.4, 4.5 and 1.5-fold cross-resistant to VBL, doxorubicin, colchicine and etoposide, respectively (ibid., Shalinsky et al, 1990a analysis according to the method of Thimmaiah and Sethi (1985). [3H]-VBL was stable for at least 2 months when stored at -80°C.…”

mentioning

confidence: 99%

Regulation of initial vinblastine influx by P-glycoprotein

Shalinsky

Jekunen²,

Alcaraz³

et al. 1993

Br J Cancer

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Summary P-glycoprotein (PGP) is an energy-dependent efflux pump that serves to protect cells against the cytotoxicity of many natural product drugs including vinblastine (VBL). In this study we investigated the role of PGP in regulating initial VBL influx. The apparent influx of VBL, measured over the first 20 s, was 2-fold lower in KB-GRCI cells expressing a transfected mdrl gene at high level than in non-expressing parental KB-3-1 cells. Inhibition of PGP efflux function with dipyridamole increased the influx rate constant by 4.0-fold in the KB-GRC1 cells but only 2.1-fold in the KB-3-1 cells. Verapamil, another inhibitor of PGP-mediated efflux, increased the initial influx rate constant by 2.7-fold in the KB-GRCI cells but only 1.4-fold in the KB-3-1 cells. Inhibition of PGP function by depletion of ATP increased influx by 6.8-fold and 2.2-fold in the two cell types, respectively. Mutation of PGP at both ATP binding sites abolished its ability to limit initial influx. Thus, VBL is serving as an efficient substrate for the efflux pump even within the first few seconds of drug exposure, consistent with the hypothesis that PGP may directly efflux drug from the cell membrane.

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An altered pattern of cross-resistance in multidrug-resistant human cells results from spontaneous mutations in the mdr1 (P-glycoprotein) gene

Cited by 421 publications

References 45 publications

Double minute chromosomes carrying the human multidrug resistance 1 and 2 genes are generated from the dimerization of submicroscopic circular DNAs in colchicine-selected KB carcinoma cells.

Double minute chromosomes carrying the human multidrug resistance 1 and 2 genes are generated from the dimerization of submicroscopic circular DNAs in colchicine-selected KB carcinoma cells.

Amino acid substitutions in the first transmembrane domain (TM1) of P‐glycoprotein that alter substrate specificity

Regulation of initial vinblastine influx by P-glycoprotein

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