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  • American Association for Cancer Research (AACR)  (2)
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  • American Association for Cancer Research (AACR)  (2)
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  • 1
    Online Resource
    Online Resource
    A T3587G germ-line mutation of the MDR1 gene encodes a nonfunctional P-glycoprotein
    American Association for Cancer Research (AACR) ; 2006
    In:  Molecular Cancer Therapeutics Vol. 5, No. 4 ( 2006-04-01), p. 877-884
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    In: Molecular Cancer Therapeutics, American Association for Cancer Research (AACR), Vol. 5, No. 4 ( 2006-04-01), p. 877-884
    Abstract: The human multidrug resistance gene 1 (MDR1) encodes a plasma membrane P-glycoprotein (P-gp) that functions as an efflux pump for various structurally unrelated anticancer agents. We have identified two nonsynonymous germ-line mutations of the MDR1 gene, C3583T MDR1 and T3587G MDR1, in peripheral blood cell samples from Japanese cancer patients. Two patients carried the C3583T MDR1 allele that encodes H1195Y P-gp, whereas a further two carried T3587G MDR1 that encodes I1196S P-gp. Murine NIH3T3 cells were transfected with pCAL-MDR-IRES-ZEO constructs carrying either wild-type (WT), C3583T, or T3587G MDR1 cDNA and selected with zeocin. The resulting zeocin-resistant mixed populations of transfected cells were designated as 3T3/WT, 3T3/H1195Y, and 3T3/I1196S, respectively. The cell surface expression of I1196S P-gp in 3T3/I1196S cells could not be detected by fluorescence-activated cell sorting, although low expression of I1196S P-gp was found by Western blotting. H1195Y P-gp expression levels in 3T3/H1195Y cells were slightly lower than the corresponding WT P-gp levels in 3T3/WT cells. By immunoblotting analysis, both WT P-gp and H1195Y P-gp were detectable as a 145-kDa protein, whereas I1196S P-gp was visualized as a 140-kDa protein. 3T3/I1196S cells did not show any drug resistance unlike 3T3/H1195Y cells. Moreover, a vanadate-trap assay showed that the I1196S P-gp species lacks ATP-binding activity. Taken together, we conclude from these data that T3587G MDR1 expresses a nonfunctional P-gp and this is therefore the first description of such a germ-line mutation. We contend that the T3587G MDR1 mutation may affect the pharmacokinetics of MDR1-related anticancer agents in patients carrying this allele. [Mol Cancer Ther 2006;5(4):877–84]
    Type of Medium: Online Resource
    ISSN: 1535-7163 , 1538-8514
    URL: Article
    DOI: 10.1158/1535-7163.MCT-05-0240
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2006
    detail.hit.zdb_id: 2062135-8
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Inhibition of the mitogen-activated protein kinase pathway results in the down-regulation of P-glycoprotein
    American Association for Cancer Research (AACR) ; 2007
    In:  Molecular Cancer Therapeutics Vol. 6, No. 7 ( 2007-07-01), p. 2092-2102
    Details
    In: Molecular Cancer Therapeutics, American Association for Cancer Research (AACR), Vol. 6, No. 7 ( 2007-07-01), p. 2092-2102
    Abstract: The multidrug resistance gene 1 (MDR1) product, P-glycoprotein (P-gp), pumps out a variety of anticancer agents from the cell, including anthracyclines, Vinca alkaloids, and taxanes. The expression of P-gp therefore confers resistance to these anticancer agents. In our present study, we found that FTI-277 (a farnesyltransferase inhibitor), U0126 [an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)], and 17-allylamino-17-demethoxygeldanamycin (an inhibitor of heat shock protein 90) reduced the endogenous expression levels of P-gp in the human colorectal cancer cells, HCT-15 and SW620-14. In contrast, inhibitors of phosphatidylinositol 3-OH kinase, mammalian target of rapamycin, p38 mitogen-activated protein kinase, and c-Jun NH2-terminal kinase did not affect P-gp expression in these cells. We further found that U0126 down-regulated exogenous P-gp expression in the MDR1-transduced human breast cancer cells, MCF-7/MDR and MDA-MB-231/MDR. However, the MDR1 mRNA levels in these cells were unaffected by this treatment. PD98059 (a MEK inhibitor), ERK small interfering RNA, and p90 ribosomal S6 kinase (RSK) small interfering RNA also suppressed P-gp expression. Conversely, epidermal growth factor and basic fibroblast growth factor enhanced P-gp expression, but the MDR1 mRNA levels were unchanged in epidermal growth factor–stimulated cells. Pulse-chase analysis revealed that U0126 promoted P-gp degradation but did not affect the biosynthesis of this gene product. The pretreatment of cells with U0126 enhanced the paclitaxel-induced cleavage of poly(ADP-ribose) polymerase and paclitaxel sensitivity. Furthermore, U0126-treated cells showed high levels of rhodamine123 uptake. Hence, our present data show that inhibition of the MEK-ERK-RSK pathway down-regulates P-gp expression levels and diminishes the cellular multidrug resistance. [Mol Cancer Ther 2007;6(7):2092–2102]
    Type of Medium: Online Resource
    ISSN: 1535-7163 , 1538-8514
    URL: Article
    DOI: 10.1158/1535-7163.MCT-07-0148
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2007
    detail.hit.zdb_id: 2062135-8
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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