Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The use of anti-cancer chemotherapy often leads to the rise of multidrug-resistant (MDR) tumors. We have previously reported the overexpression of a 40kDa protein (P-40) in several MDR tumor cell lines. In this report we describe the cloning of a 1.4kb cDNA with an open reading frame of 344 amino acids that encodes the P-40 protein. Analysis of the P-40 amino acid sequence showed it is identical to the human annexin I (Anx-I) protein. The identity of the isolated P-40 cDNA as Anx-I was confirmed by the specific binding of IPM96 mAb to a 40kDa protein following the in vitro expression of P-40 full-length cDNA. Northern blot analysis of total RNA from drug-sensitive and -resistant cells revealed an increase in P-40 (or Anx-I) mRNA in drug-resistant cells relative to drug-sensitive cells. Transfection of Anx-I cDNA into drug-sensitive MCF-7 cells was carried out without further drug selection and showed 2- to 5-fold increase in resistance of transfected cells to adriamycin, melphalan, and etoposide. Conversely, transfection of reverse Anx-I cDNA into SKOV-3 cells decreased the expression of Anx-I without affecting the expression of other members of the annexin family and showed a 3- to 8-fold increase in sensitivity to these drugs. Of interest was the correlation between the presence of Anx-I and MDR in MDA-MB-231 cells when compared to MCF-7 cells. MDA-MB-231 cells show 3- to 20-fold increase in resistance to adriamycin, melphalan, and etoposide in the absence of detectable levels of P-glycoprotein (P-gp1), the multidrug resistance protein (MRP1) or the breast cancer resistance protein (BCRP). Taken together, these results provide the first direct evidence for the role of Anx-I in MDR of tumor cells.
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PMID:Annexin-I expression modulates drug resistance in tumor cells. 1473 45

The drug accumulation of a human multidrug resistance 1 (mdr1) gene-transfected mouse lymphoma cell line and a multidrug resistance protein (MRP)-expressing human breast cancer cell line MDA-MB-231 was compared in the presence of sixteen flavonoids and five isoflavonoids. The expression of the 170-kDa P-glycoprotein (P-gp) (MDR1) and 190-kDa multidrug resistance protein (MRP) in both cell lines was confirmed by immunocytochemistry. The rhodamine 123 accumulation of the P-glycoprotein (P-gp)-expressing cells increased up to 46.4, while 2,7'-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein acetoxymethyl ester (BCECF-AM) accumulation of the MRP-expressing cells increased up to 1.6, in fluorescence activity ratio (FAR). Major P-gp-mediated efflux pump modifiers are formononetin, amorphigenin, rotenone and chrysin, while MRP-mediated efflux pump modifiers are formononetin, afrormosin, robinin, kaempferol and epigallocatechin. In antiproliferative assay, afrormosin, amorphigenin, chrysin and rotenone exhibited the strongest antiproliferative effects in L5178 (max. ID50: 19.70) and MDA-MB-231 cell lines (max. ID50: 55.47). In a checkerboard microplate method in vitro, furthermore, the most effective multidrug resistance (MDR) resistance modifiers, amorphigenin, formononetin, rotenone and chrysin, were assayed for their antiproliferative effects in combination with epirubicin. Rotenone and afrormosin showed additive effects. Chrysin and amorphigenin on the mouse lymphoma cell line and formononetin on the MDA-MB-231 cell line synergistically enhanced the effect of epirubicin.
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PMID:In vitro search for synergy between flavonoids and epirubicin on multidrug-resistant cancer cells. 1579 99

Anticoagulant treatment with heparins is frequently used to prevent venous thromboembolism in cancer patients. In the present study, we investigated the ability of unfractionated heparin (UFH) to inhibit P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) on human breast cancer cell line (MDA-MB231) and its doxo-resistant subline. Results were a compared to the classic reversing agent, Verapamil (Ver), used, as reference at 50 microM concentration. We analysed the Pgp function by calcein acetoxymethylester (calcein-AM) uptake, a fluorescent marker substrate, before and after in vitro exposure to UFH at clinically achievable dose of 20 U/ml. The mean percentage of calcein-AM retained into cancer cells after 3 and 12 h were 32 +/- 10.9 and 45 +/- 12.3, respectively, for UFH pretreated cells and 25.3 +/- 8.7 and 29.4 +/- 10.4, respectively, for Ver pretreated cells when compared to control cells, receiving only medium. Pgp activity was studied by measuring intracellular drug accumulation in doxo-resistant subline, treated (2 h) with either UFH or Ver, prior exposure (2 h) at different doxo concentrations (2, 4 and 8 microM). The mean percentage of remaining intracellular doxo were 55.4 +/- 4.5 , 51.4 +/- 3.9 and 50 +/- 1.8 percent, respectively for UFH treated cells, and 44.1 +/- 5.8, 39.3 +/- 4.4 and 19.4 +/- 8.6%, respectively, for Ver treated cells as compared with control cells, receiving only doxo. These results were consistent with the increase of sensitivity to doxo of the same doxo-resistant subline resulting in a 2.2, 2.6 and 2.2-fold increase, respectively, for UFH-doxo combination and 2.2, 2.5 and 2.0-fold respectively, for Ver-doxo combination respect to cells receiving doxo alone, as assessed by MTT test. In conclusion, these findings demonstrate the potentiating effect in vitro of UFH on doxo accumulation and cytotoxicity in the MDA-231 cell line and its doxo-resistant subline and suggest that UFH could to be used, as an potential chemosensitizer, in clinical chemotherapy for increasing in vivo, the efficacy of the anticancer treatment.
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PMID:Inhibition of P-glycoprotein-mediated multidrug resistance by unfractionated heparin: a new potential chemosensitizer for cancer therapy. 1587 59

The resistance of tumors to classic taxanes (paclitaxel and docetaxel) presents problems in chemotherapy. Thus, new taxanes with higher antitumor activity in resistant tumors are synthesized. This study compared cytotoxicity and transport of paclitaxel and docetaxel with novel taxanes SB-T-1103, SB-T-1214, and SB-T-1216 in adriamycin-sensitive (MDA-MB-435) and -resistant (NCI/ADR-RES) human breast cancer cells. The cell lines examined differ in adriamycin transport, suggesting different expression of ABC membrane transporters. Reverse transcription-polymerase chain reaction revealed that NCI/ADR-RES cells expressed high levels of P-glycoprotein mRNA, which was absent in MDA-MB-435 cells, while the opposite was true for MRP2 mRNA. Both cell lines shared or differently expressed eight other ABC transporters and LRP. NCI/ADR-RES cells were 1,000-fold more resistant to paclitaxel and 600-fold more resistant to docetaxel in MTT assay than MDA-MB-435 cells, but almost equally sensitive to SB-T-1103, SB-T-1214, and SB-T-1216. This complied with the fact that NCI/ADR-RES cells absorbed almost 20-fold less [14C]paclitaxel, about 7-fold less docetaxel, and almost equal amounts of SB-T-1103, SB-T-1214, and SB-T-1216 as the MDA-MB-435 cells. Verapamil increased uptake of [14C]paclitaxel by NCI/ADR-RES cells 7-fold and decreased its efflux 2.5-fold; in contrast, it weakly influenced uptake and increased the efflux in MDA-MB-435 cells. SB-T-1103 and SB-T-1216 did not influence transport of paclitaxel, but SB-T-1214 decreased [14C]paclitaxel uptake in both cell lines indicating inhibition of uptake. This suggests that the novel taxanes are not inhibitors of P-glycoprotein. However, novel taxanes exert much higher activity on resistant tumor cells than classic taxanes and seem to be potential drugs for therapy in taxane-resistant tumors.
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PMID:Transport and cytotoxicity of paclitaxel, docetaxel, and novel taxanes in human breast cancer cells. 1605 35

During the course of a mechanism-based screening program aimed at identifying new antimitotic agents, a novel microtubule depolymerizing piperazine derivative, 1-(5-chloro-2-methoxybenzoyl)-4-(3-chlorophenyl) piperazine, was identified. The compound, designated CB694, caused inhibition of proliferation of a wide range of cancer cell lines, with an average IC50 of 85 nM. A multidrug-resistant cell line was sensitive to inhibition by CB694, suggesting that this compound is a poor substrate for transport by P-glycoprotein. CB694 caused formation of abnormal mitotic structures in HeLa cells. Specifically, CB694 caused a concentration-dependent increase in bipolar spindles with lagging chromosomes and, with slightly higher concentrations, formation of multipolar mitotic spindles. These mitotic abnormalities occurred at concentrations that did not cause significant changes in the appearance or quantity of interphase microtubules. Coincident with the formation of abnormal mitotic spindles, CB694 caused G2/M arrest. CB694 inhibited the assembly of purified tubulin with an IC50 of 2.3 microM. Colchicine binding was strongly inhibited by CB694, suggesting that it binds to tubulin at the colchicine site. Bcl-2 phosphorylation and activation of ERK and JNK and caspase 3-dependent cleavage of PARP were observed in MDA-MB-435 cells treated with CB694. CB694 caused phosphorylation of Aurora A within 8 hr of treatment, and increases in Aurora A protein levels were coincident with mitotic accumulation. The efficacy of CB694 against a syngeneic murine transplantable solid tumor, Mammary 16/C, was also evaluated. CB694 was well tolerated and showed antitumor activity.
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PMID:CB694, a novel antimitotic with antitumor activities. 1615 90

We have investigated the effect of 13 flavonoid derivatives on [(14)C]paclitaxel transport in two human breast cancer cell lines, the adriamycin-resistant NCI/ADR-RES and sensitive MDA-MB-435. For this study, we selected representatives of aurones, chalcones, flavones, flavonols, chromones, and isoflavones with known binding affinity toward nucleotide-binding domain (NBD2) of P-glycoprotein and for which no reported work is available regarding paclitaxel transport. Aurones CB-284, CB-285, CB-287, and ML-50 most effectively inhibited P-gp related transport in the resistant line in comparison with chalcones, flavones, flavonols, chromones, and isoflavone derivatives and accordingly increased the accumulation of [(14)C]paclitaxel and decreased its efflux. Those agents efficiently modulated paclitaxel transport in P-gp highly expressing resistant human breast cancer cells and they could increase the efficiency of chemotherapy in paclitaxel-resistant tumors. In contrast, the sensitive cell line responded reversely in that CB-284, CB-285, CB-287, and ML-50 significantly inhibited accumulation of [(14)C]paclitaxel and especially CB-287, which significantly stimulated its efflux. Some, but not all, of the data correlated with the binding of flavonoid derivatives to P-gp, and indicated that even in the P-gp highly expressing NCI/ADR-RES cells, the binding was not the only factor influencing the transport of [(14)C]paclitaxel. Opposite effects of flavonoid derivatives on the P-gp highly expressing and MDA-MB-435 non-expressing cell lines indicate that paclitaxel is not only transported by P-gp and let us assume that Mrp2 or ABCC5 seem to be good transport-candidates in these cells. The inhibition of paclitaxel accumulation and stimulation of its efflux are potentially unfavorable for drug therapy and since they could be due to modulation of drug transporters other than P-gp, their expression in tumors is of great significance for efficient chemotherapy.
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PMID:Modulation of paclitaxel transport by flavonoid derivatives in human breast cancer cells. Is there a correlation between binding affinity to NBD of P-gp and modulation of transport? 1651 78

Lauryl gallate is an antioxidant food additive showing low toxicity to normal cells. Here, its antiproliferative effect has been studied on three human breast cancer cell lines: estrogen-dependent, wild-type p53, MCF7; estrogen-independent, non-functional p53, MDA-MB-231 and MCF7 ADR, which overexpresses P-glycoprotein (P-gp) and displays a multidrug-resistant phenotype. Lauryl gallate inhibited proliferation and induced cell cycle alterations in all three cell lines without altering P-gp functionality in the drug-resistant cells. A stable arrest in G(1) phase was observed in MCF7, while a slow-down of cell cycle progression was induced in the other two cell lines. Lauryl gallate increased p53 expression only in MCF7, and upregulated p21(Cip1) and reduced cyclin D1 levels in all three cell lines. The induction of apoptosis, demonstrated by annexin V-FITC labeling, PARP cleavage and mitochondrial membrane depolarization and morphological alterations, were clearly detected in MCF7 ADR and MDA-MB-231 and to a minor extent in MCF7. Overexpression of Bcl-2 in MCF7 ADR cells demonstrated its protective role against morphological alterations and apoptosis. Lauryl gallate induction of p21(Cip1) and apoptosis observed in all three cell lines was regulated by Erk1/2 activation. These findings suggest a potential use of lauryl gallate against tumors harboring p53 mutations and drug-resistant phenotypes.
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PMID:Inhibition of proliferation and induction of apoptosis in human breast cancer cells by lauryl gallate. 1662 27

The human multidrug resistance gene 1 (MDR1) encodes the plasma membrane P-glycoprotein (P-gp/ABCB1) that functions as an efflux pump for various anticancer agents. We recently reported that estrogens down-regulate the expression of breast cancer resistance protein (BCRP/ABCG2). In our present study we demonstrate that estrogens also down-regulate P-gp expression in the MDR1-transduced, estrogen receptor alpha (ER-alpha)-positive human breast cancer cells, MCF-7/MDR and T-47D/MDR. The P-gp expression levels in MCF-7/MDR cells treated with 100 pM estradiol were found to be 10-20-fold lower than the levels in these same cells that were cultured without estradiol. In contrast, estradiol did not affect the P-gp expression levels in the ER-alpha-negative cancer cells, MDA-MB-231/MDR and NCI/ADR-RES. Estrone and diethylstilbestrol were also found to down-regulate P-gp in MCF-7/MDR cells, but progesterone treatment did not produce this effect. Tamoxifen reversed the estradiol-mediated down-regulation of P-gp in MCF-7/MDR cells, suggesting that ER-alpha activity is necessary for the effects of estradiol upon P-gp. However, estradiol was found not to alter the MDR1 transcript levels in either MCF-7/MDR and T-47D/MDR cells, suggesting that post-transcriptional mechanisms underlie its effects upon P-gp down-regulation. MCF-7/MDR cells also showed eight-fold higher sensitivity to vincristine when treated with 100 pM estradiol, than when treated with 1 pM estradiol. These results may serve to provide a better understanding of the expression control of ABC transporters, and possibly allow for the establishment of new cancer chemotherapy strategies that would control P-gp expression in breast cancer cells and thereby increase their sensitivity to MDR1-related anticancer agents.
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PMID:Estrogen-mediated post transcriptional down-regulation of P-glycoprotein in MDR1-transduced human breast cancer cells. 1692 84

Non-steroidal anti-inflammatory drugs (NSAIDs) and cyclo-oxygenase (COX) inhibitors are anti-inflammatory agents that have also shown to be useful in anticancer therapy. In the present study, we show that the specific COX-2 inhibitor celecoxib enhances the inhibitory effect of doxorubicin (dox) on human MDA-MB231 breast tumour growth in vivo and in vitro. We also found that celecoxib increased the intracellular accumulation and retention of dox in vitro. Since the NSAID indomethacin and the specific COX-2 inhibitor NS398 did not affect the in vitro actions of dox, these effects are likely to be mediated via a COX-independent mechanism. It has been suggested that some COX-inhibitors can enhance the actions of cytostatics by overcoming multidrug resistance through the inhibition of ABC-transporter proteins. However, we found that the three main ATP-binding cassette (ABC)-transporter proteins, implicated in dox transport, were inactive in MDA-MB231 cells. Therefore, the finding that the P-glycoprotein (P-gp) blocker PSC833 also increased cellular accumulation of dox was unexpected. In order to unravel the molecular mechanisms involved in dox accumulation, we examined the involvement of NF-kappaB, as this transcription factor has been implicated in celecoxib action as well as in chemoresistance. We found that celecoxib and PSC833, but not indomethacin or NS398, almost completely inhibited basal- and dox induced NF-kappaB gene-reporter activity and p65 subunit nuclear translocation. Furthermore, the NF-kappaB inhibitor PDTC mimicked the actions of celecoxib and PSC833 on cell growth and on intracellular accumulation of dox, suggesting that NF-kappaB is functionally involved in the actions of these compounds. In conclusion, we show that structurally different compounds, among which are celecoxib and PSC833, increase the intracellular accumulation of dox and enhance dox induced cytotoxicity in MDA-MB231 breast cancer cells most likely via the modulation of NF-kappaB activity.
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PMID:Celecoxib enhances doxorubicin-induced cytotoxicity in MDA-MB231 cells by NF-kappaB-mediated increase of intracellular doxorubicin accumulation. 1709 85

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 NH(2)-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.
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PMID:Inhibition of the mitogen-activated protein kinase pathway results in the down-regulation of P-glycoprotein. 1762 Apr 38


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