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)

To improve cytotoxicity of 10-deoxy-10-C-morpholinoethyl docetaxel analogues against various tumor cell lines including resistant cells expressing P-glycoprotein (P-gp), we modified the 7-hydroxyl group to hydrophobic groups (methoxy, deoxy, 6,7-olefin, alpha-F, 7-beta-8-beta-methano, fluoromethoxy). Among these analogues, the 7-methoxy analogue showed the strongest cytotoxicity. This analogue showed potent activity against B16 melanoma BL6 in vivo by oral administration.
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PMID:Orally active docetaxel analogue: synthesis of 10-deoxy-10-C-morpholinoethyl docetaxel analogues. 1121 22

Cytochrome P450 enzymes metabolize various endogenous and exogenous small molecular weight compounds. Transport-associated proteins, such as P-glycoprotein, multidrug resistance-associated protein and lung resistance protein are overexpressed in drug-resistant cell lines, as well as in human tumors from various histologic origins, including malignant melanoma. Little is known about the expression and function of cytochrome enzymes and multidrug resistance-associated transport proteins in human skin; therefore, the aim of this study was to analyze the expression pattern of cytochrome enzymes and multidrug resistance-associated transport proteins in proliferating human epidermal keratinocytes under constitutive conditions and after induction with various inducers. Reverse transcription-polymerase chain reaction revealed constitutive expression of cytochromes 1A1, 1B1, 2B6, 2E1, and 3A5 in keratinocytes and showed expression of cytochrome 3A4 after incubation with dexamethasone. The expression of cytochrome 1A1 was enhanced on the mRNA level after induction with benzanthracene. Reverse transcription-polymerase chain reaction analysis of the multidrug resistance-associated transport proteins revealed constitutive expression of multidrug resistance-associated proteins 1 and 3-6, and lung resistance protein in human epithelial keratinocytes and was negative for multidrug resistance 1 and 2. Expression of 1 was seen after induction with dexamethasone. Reverse transcription-polymerase chain reaction results were confirmed by immunoblots which showed expression of cytochromes 1A1, 2B6, 2E1, and 3A, multidrug resistance-associated proteins 1, 3, and 5 as well as multidrug resistance 1 after induction with dexamethasone. Immunohistology showed positive immunofluorescence in skin specimens for cytochromes 1A1, 2B6, 2E1, and 3A and multidrug resistance-associated protein 1 and multidrug resistance 1. Constitutive activity of cytochrome 1A1, 2B, 2E1, and 3A enzymes was measured by catalytic assays. These results show that keratinocytes of the human skin express various transport-associated enzymes and detoxifying metabolic enzymes. Previous studies have revealed that cytochrome enzymes and transport-associated proteins play complementary parts in drug disposition by biotransformation (phase I) and anti-transport (phase III) and act synergistically as a drug bioavailability barrier.
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PMID:Expression of multiple cytochrome p450 enzymes and multidrug resistance-associated transport proteins in human skin keratinocytes. 1128 21

Malignant melanoma is increasing in frequency at a rapid rate in the United States. Metastatic disease is chemoresistant with DTIC considered the most active single agent. CI-980 is a synthetic mitotic inhibitor that blocks the assembly of tubulin and microtubules. It has shown cytotoxic activity against a broad spectrum of murine and human tumor cell tines. CI-980 can cross the blood brain barrier, is effective when given orally or parenterally, and is active against multidrug resistant cell lines overexpressing P-glycoprotein. In this trial, patients with disseminated melanoma with measurable disease, SWOG performance status of 0-1, no prior chemotherapy or immunotherapy for metastatic disease, and adequate hepatic and renal function, were enrolled. Treatment with CI-980 was given by 72 h continuous i.v. infusion at a dose of 4.5 mg/m2/day, days 1-3 every 21 days. Twenty-four patients were registered on this study with no patients ineligible. They ranged in age from 33-78 with performance status of 0 in 15 patients and 1 in 9 patients. Nineteen patients had visceral disease with 12 having liver involvement. There were no confirmed responses. The overall response rate was 0% (95% CI 0%-14%). The median overall survival is eleven months (95% CI 4-14 months). The most common toxicities were hematologic and consisted of leukopenia/granulocytopenia and anemia, with nausea/vomiting and malaise/fatigue/weakness also frequent. CI-980 administered at this dose and schedule has insufficient activity in the treatment of disseminated malignant melanoma to warrant further investigation.
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PMID:Phase II trial of CI-980 in patients with disseminated malignant melanoma and no prior chemotherapy. A Southwest Oncology Group study. 1156 81

The overexpression of the drug-efflux molecular pump P-glycoprotein (P-gp) may confer to tumor cells the multidrug resistant (MDR) phenotype, which is one of the causes of cancer chemotherapy failure. By investigating several in vitro models of human tumor cells, we observed that P-gp, in addition to its localization on the plasma membrane, can also be found intracellularly. In particular, by using immunocytochemical and cytofluorimetric methods, we revealed that in MDR breast cancer cells (MCF-7) a significant level of P-gp was expressed in the Golgi apparatus, which is the major site of accumulation of the antitumoral compound doxorubicin. Moreover, we demonstrated the intracellular location of P-gp in three stabilized human melanoma cell lines which had never undergone cytotoxic drug treatment and did not express the transporter molecule on the plasma membrane. Double immunofluorescence labelling and immunoelectron microscopy revealed, also in this tumor cell type, the location of P-gp in the Golgi apparatus where it seems to play a pivotal role in intracellular drug transport. Finally, we analyzed the expression, localization and function of drug transport proteins in human colon carcinoma lines (LoVo) exhibiting different degrees of intrinsic or drug-induced resistance. We found that only MDR LoVo cells expressed P-gp on the plasma membrane while both low-level drug resistant clonal LoVo cells and MDR LoVo cells appeared to be positive for intracellular P-gp. Our findings suggest a functional role of the intracytoplasmic P-gp in the transport and sequestration of drugs. This represents a complementary protective mechanism of tumor cells against cytotoxic agents.
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PMID:Intracellular P-glycoprotein in multidrug resistant tumor cells. 1172 98

A library with 63 paclitaxel analogues modified at the C10 position of paclitaxel has been prepared using parallel solution phase synthesis. Most of the C10 analogues were slightly less active than paclitaxel in the tubulin assembly assay and had reduced potency in the B16 melanoma and MCF-7 cell line cytotoxicity assays. These modifications at C10, however, did not lead to the total loss of activity, indicating that the C10 moiety of paclitaxel may not be directly involved in the drug-microtubule interactions, but could influence its binding affinity to P-glycoprotein. Approximately 50% of the analogues demonstrated better activity against the drug resistant cell line MCF7-ADR. However, the increase in activity was 10-fold at most. This result demonstrates that the cytotoxicity against this drug resistant cancer cell line is sensitive to structural changes at the C10 position of paclitaxel. It was also found that the presence of a nitrogen atom in the C10 substituent might play a role in the interaction of analogues with microtubules.
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PMID:A systematic SAR study of C10 modified paclitaxel analogues using a combinatorial approach. 1186 Mar 38

A number of studies have reported that increased P-glycoprotein expression in drug-resistant tumour cells may be associated with decreased expression of a family of surface glycoproteins. However, despite its potential biological and clinical relevance, this phenomenon has not been extensively studied. In this study the phenotypic alterations that are associated with the acquisition of the multidrug-resistant phenotype in tumour cells, together with drug transporter overexpression, were investigated in human melanoma cells. The expression of cell adhesion molecules was analysed in a panel of multidrug-resistant melanoma cell lines (M14Dx) showing different degrees of resistance to doxorubicin and different levels of the expression of the drug transporter P-glycoprotein. In particular, expression of intercellular adhesion molecule-1 (ICAM-1), CD44, very late activation antigen (VLA)-5 and VLA-2 was determined by flow cytometry in the different resistant cell lines. A progressive downregulation of all the adhesion molecules examined was revealed in M14Dx cells, in parallel with an increasing level of expression of the drug transporter P-glycoprotein. The results obtained raise the question of the role of P-glycoprotein in the invasive and metastatic behaviour of tumour cells.
Melanoma Res 2002 Apr
PMID:What is the relationship between P-glycoprotein and adhesion molecule expression in melanoma cells? 1193 Jan 6

Different types of cancer are naturally resistant to many anticancer drugs. Additionally, these tumours develop acquired drug resistance, which includes the classical multidrug resistance (MDR) accompanied by the synthesis of P-glycoprotein, a member of the superfamily of ATP-binding cassette (ABC) transporters. Furthermore, atypical MDR is mediated by several different, some unknown, mechanisms. To overcome chemoresistance problems, antineoplastic drugs are often combined with other modes of therapy, e.g. hyperthermia, where good response has been reported in several experimental tumour models and in advanced cancer patients. The success of this combined anticancer treatment may be limited by an increase in chemoresistance and thermoresistance. A model system to study resistance phenomena is the use of chemoresistant and thermoresistant cancer cell lines. We have established chemoresistant cancer cell lines (gastric and pancreatic carcinoma, fibrosarcoma, melanoma) and now thermoresistant cell lines derived from gastric and pancreatic carcinoma cells and their counterparts that were resistant towards daunorubicin (classical MDR) and mitoxantrone (atypical MDR). Using proteomics, in this paper we evaluate the drug resistance of chemoresistant melanoma cells (parental cell line MeWo and sublines exhibiting drug resistance towards etoposide, cisplatin, fotemustine and vindesine) as a paradigm for analysis of drug resistance phenomena. Additionally, we investigate heat resistance and the interaction of chemoresistance and thermoresistance to identify common pathways using the parental and drug resistant stomach cancer cell lines EPG85-257, EPG85-257RNOV, EPG85-257RDB and their thermoresistant counterparts. Possible implications of differential protein expression will be discussed.
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PMID:Study of therapy resistance in cancer cells with functional proteome analysis. 1200 11

In vitro studies on the cellular location of P-glycoprotein (Pgp) are reported with the aim to clarify the relationship between its intracellular expression and the multidrug resistance (MDR) level of tumor cells. Pgp was found abnormally expressed on the plasma membrane of tumor cells with "classical" MDR phenotype. However, Pgp was also often detected on the nuclear envelope and on the membrane of cytoplasmic organelles. The hypothesis that this drug pump maintains a transport function when located in these compartments, is still under debating. Our results, together with those obtained by other researchers, demonstrate that cytoplasmic Pgp regulates the intracellular traffic of drugs so that they are no more able to reach their cellular targets. In particular, we revealed that in MDR breast cancer cells (MCF-7) a significant level of Pgp was expressed in the Golgi apparatus. A similar result was found in human melanoma cell lines, which never undergone cytotoxic drug treatment and did not express the transporter molecule on the plasma membrane. A strict relationship between intracellular Pgp and intrinsic resistance was demonstrated in a human colon carcinoma (LoVo) clone, which did not express the drug transporter on the plasma membrane. Finally, a structural and functional association between Pgp and ERM proteins has been discovered in drug-resistant human T- lymphobastoid cells (CEM-VBL 100). Our findings strongly suggest a pivotal role of the intracytoplasmic Pgp in the transport of drugs into cytoplasmic vesicles, thus actively contributing to their sequestration and transport outwards the cells. Thus, intracellular Pgp seems to represent a complementary protective mechanism of tumor cells against cytotoxic agents.
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PMID:Subcellular detection and localization of the drug transporter P-glycoprotein in cultured tumor cells. 1247 Feb 19

We synthesized novel water-soluble and orally active taxane analogues, 7-deoxy-9beta-dihydro-9,10-O-acetal taxanes. Cytotoxicities of the synthetic compounds were greater than those of paclitaxel and docetaxel, especially against resistant cancer cell lines expressing P-glycoprotein. In addition, some compounds showed potent antitumor effects against B16 melanoma BL6 in vivo by both iv and po administration.
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PMID:New highly active taxoids from 9beta-dihydrobaccatin-9,10-acetals. Part 3. 1248 20

Due to the size, glycosylation, and location in the plasma membrane of the sialomucin complex Muc4, which has been implicated in ErbB2 signaling, in the repression of apoptosis and cell adhesion, and in tumor metastasis, studies were initiated to determine whether its presence could influence cell sensitivity to anticancer drugs. Growth inhibition assays using melanoma cell lines that either express the glycoprotein (Muc4(+)) or do not (Muc4(-)) showed that Muc4 renders cells resistant to taxol, doxorubicin, vinblastine, rhodamine 123, and 2-deoxyglucose. When treated with various concentrations of doxorubicin, Muc4(+) cells were blocked less frequently in G(2) and underwent less DNA fragmentation (apoptosis and/or necrosis) than Muc4(-) cells. All of the drugs tested (except for 2-deoxyglucose) are well recognized by P-glycoprotein-mediated multidrug resistance 1 (MDR1) and to a lesser degree by multidrug resistance related protein 1 (MRP1) transporters. Therefore, transporter gene expression in these cells was assayed. Surprisingly, Muc4(+) cells expressed lower levels of both transporter genes than Muc4(-) cells. Moreover, rhodamine 123 was retained more highly in the Muc4(+) than in the Muc4(-) cells, demonstrating that these transporters are functional. Overall, these results indicate that although Muc4(+) cells express less MDR1 and MRP1, they are more resistant to drugs recognized by these transporters.
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PMID:Multidrug resistance correlates with overexpression of Muc4 but inversely with P-glycoprotein and multidrug resistance related protein in transfected human melanoma cells. 1273 53


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