Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.44 (P-glycoprotein)
13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have been studying the resistance mechanisms of various antitumor drugs and screening substances from natural and synthetic products which overcome resistance. In this paper, we described compounds mainly obtained from our screening systems. I. Circumvention of multidrug resistance (MDR). Lactoquinomycin was discovered from the culture broth of a strain of Streptomyces sp. and it showed preferential growth inhibition against multidrug-resistant L5178 Y cells. The mechanism of action of lactoquinomycin was studied. Another novel antibiotic, resorthiomycin, exhibited not only preferential inhibition against MDR tumor cells but also augmentation of cytotoxicity of several antitumor drugs. As synthetic potentiators, dipyridamole, cepharanthine, AHC-52 and analogs of dihydropyridines were described; all of them were thought to interact with a P-glycoprotein and inhibit active efflux of drugs from tumor cells. SDB-ethylenediamine was unique because it overcame MDR and also potentiates a wide range of antitumor drugs including 5-FU and bleomycin. II. E-64 was found to inhibit the activity of a bleomycin-inactivating enzyme. It potentiated the activity of peplomycin in vitro and in vivo. III. Cadeguomycin was discovered from the culture filtrate of a Streptomyces sp. and it potentiated Ara-C by inhibition of the activity of dCMP deaminase, an Ara-C-inactivating enzyme.
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PMID:[Antitumor drugs and potentiators aiming circumvention of drug resistance]. 168 86

Drug sensitivities of 76 human tumor lines/nude mice to 9 anti-cancer drugs were tested. Human tumor lines include pancreas cancers, brain tumors, neuroblastomas and etc. Tested anti-cancer drugs include MMC, 5-FU, and etc. When clinically equivalent dose of anti-cancer drugs were administered, drug sensitivities of these carcinomas were well correlated with clinical one, although blood brain barrier must be considered when brain tumors were tested. Our drug sensitivity panel revealed that cancers originated from the same organ showed the same tendency of drug sensitivity. Therefore, our drug sensitivity panel is thought to be useful to know the anti-cancer spectrum of newly developed anti-cancer drugs. Our panel is also useful to study the chemotherapy of rare cancers, because clinical studies of rare cancers are difficult. Expression of P-glycoprotein is correlated with drug resistance when treated with CED, but is not correlated with those when treated with MTD (maximum tolerate dose). That is human tumor lines with P-glycoprotein detected by C219 monoclonal antibody showed resistance to ADR, VCR and VLB when treated by CED, but the relationship was not observed when treated with MTD.
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PMID:[Drug sensitivity panel of human cancers transplanted in nude mice]. 185 16

A multidrug-resistant cell line (A2780/ADM) of human ovarian carcinoma which can resist 0.8 microgram.ml-1 of adriamycin (ADM) was obtained by step-wise selection exposure to increasing doses of ADM. A2780/ADM cells showed 17-fold higher resistance to ADM than A2780 cells. The doubling times were 43.8 h in A2780/ADM and 26.3 h in A2780 cells. Colony formation rates were 15%-20% in A2780/ADM and 65%-75% in A2780 cells. A2780/ADM cell line was also shown to significantly cross-resistant to vincristine (VCR) and VP-16, but no cross-resistance was found to 5-Fu, PDD or Mel. A further investigation showed that intracellular accumulation of ADM in A2780/ADM was significantly decreased. Expressions of P-glycoprotein and GST-pi were increased in A2780/ADM by means of immunohistochemical method. Verapamil (Ver) combined with ADM was found to increase the sensitivity and reverse the resistance to ADM in A2780/ADM. This study indicates that A2780 ADM has the peculiarity of multidrug resistance and there may be other mechanism of drug-resistance besides MDR related to P-170.
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PMID:[Establishment of adriamycin-resistant human ovarian carcinoma cell line and its mechanism of multidrug resistance]. 766 Jul 93

The outcome of cancer metastasis depends on the interaction of metastatic cells with various host factors. The implantation of human cancer cells into anatomically correct (orthotopic) sites in nude mice can be used to ascertain their metastatic potential. While it is clear that vascularity and local immunity can retard or facilitate tumor growth, we have found that the organ environment also influences tumor cell functions such as production of degradative enzymes. The organ microenvironment can also influence the response of metastases to chemotherapy. It is not uncommon to observe the regression of cancer metastases in one organ and their continued growth in other sites after systemic chemotherapy. We demonstrated this effect in a series of experiments using a murine fibrosarcoma, a murine colon carcinoma, and a human colon carcinoma. The tumor cells were implanted subcutaneously or into different visceral organs. Subcutaneous tumors were sensitive to doxorubicin (DXR), whereas lung or liver metastases were not. In contrast, sensitivity to 5-FU did not differ between these sites of growth. The differences in response to DXR between s.c. tumors (sensitive) and lung or liver tumors (resistant) were not due to variations in DXR potency or DXR distribution. The expression of the multidrug resistance-associated P-glycoprotein as determined by flow cytometric analysis of tumor cells harvested from lesions in different organs correlated inversely with their sensitivity to DXR: increased P-glycoprotein was associated with overexpression of mdr1 mRNA. However, the organ-specific mechanism for upregulating mdr1 and P-glycoprotein has yet to be elucidated.
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PMID:Modulation of tumor cell response to chemotherapy by the organ environment. 792 51

The effects of 4-demethoxydaunorubicin (idarubicin, IDA) and MX2, a new morpholino-anthracycline, on up-regulation of the MDR1 gene in the low-level multidrug resistant (MDR) cell line CEM/A7R were compared at similar concentrations (IC10, IC50 and IC90) over a short time exposure (4 and 24 h). The chemosensitivity of each drug was determined by a 3-day cell growth inhibition assay. Compared with epirubicin (EPI), IDA and MX2 were 17- and eightfold more effective in the CEM/A7R line respectively. No cross-resistance to 5-FU was seen in the CEM/A7R line. Verapamil (5 microM) and PSC 833 (1 microM), which dramatically reversed resistance to EPI in the CEM/A7R line, had no sensitizing effect on the resistance of this line to MX2, but slightly decreased resistance to IDA. The sensitivity to 5-FU was unchanged by these modulators. The induction of MDR1 mRNA expression by IDA, MX2 and 5-FU was analysed by Northern blotting and semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of MDR1 expression was expressed as a ratio of MDR1 mRNA to the internal RNA control glyceraldehyde-3-phosphate dehydrogenase (GAPDH). IDA, MX2 and 5-FU differentially up-regulated MDR1 mRNA in the CEM/A7R line in a dose-dependent manner. Both IDA and MX2 induced MDR1 expression within 4 h. 5-FU up-regulated MDR1 expression only when drug exposure was prolonged to 24 h. Based on MRK 16 binding, flow cytometric analysis of P-glycoprotein (Pgp) expression paralleled the increase in MDR1 mRNA levels. For the three anthracyclines, the increase in MDR1 expression was stable in cells grown in the absence of drug for more than 3 weeks after drug treatment. The induction of MDR1 expression by 5-FU was transient, associated with a rapid decrease in the increased Pgp levels which returned to baseline 72 h after the removal of 5-FU. This study demonstrates that MDR1 expression can be induced by analogues of anthracyclines not pumped by Pgp, and that this induction appears to be stable despite a 3-week drug-free period.
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PMID:Induction of MDR1 gene expression by anthracycline analogues in a human drug resistant leukaemia cell line. 1007 Aug 77

A 68 year-old female underwent right hemicolectomy for an advanced cecum cancer and had been well without any evidence of recurrence for a year after surgery. Despite post-operative treatment with oral Tegafur (400 mg/m2/day), CEA level increased gradually beginning 15 months after surgery. Sequential chemotherapy with methotrexate (MTX) and 5-Fluorouracil (5-FU), followed by leucovorin rescue (MFL) was started on an outpatient basis, and has been continued every 4 weeks since then. It consisted of MTX (100 mg/m2) and 5-FU (600 mg/m2) started 24 hours after MTX, followed by oral leucovorin (15 mg/body) started 30 hours after MTX 6 times at intervals of 6 hours. CEA level declined initially, but increased slowly for 3 years on MFL, although no evidence of recurrence was detected by imaging studies with computed tomography, ultrasound, and scintigram. Four years after surgery, a tumor recurrence developed in the abdominal wall. The patient underwent resection of the tumor, resulting in a decline of the CEA level. She has been alive and well for 5 years on MFL after the primary surgery. Both the original tumor and recurrent tumor showed immunoreactivity for P-glycoprotein. The present case demonstrates the feasibility of using MFL on an outpatient basis, and its potential to suppress the colon cancer growth with P-glycoprotein expression.
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PMID:A case of colon cancer recurrence with P-glycoprotein treated by methotrexate, fluorouracil, and leucovorin. 1043 Mar 34

Breast cancer is a chemosensitive tumour and anthracyclines are one of the most active cytotoxic agents in chemotherapy treatment. Failure after anthracycline-containing chemotherapy is a poor prognostic factor because of low response rate to salvage chemotherapy. Several factors like P-glycoprotein mediated drug resistance (MDR-1 or MRP), glutathione or amplification of topoisomerase II have been found to be involved in anthracycline resistance. No clear benefit for patients treated with 'resistance-modifier' agents like verapamil, dexverapamil or quinidine has yet been demonstrated. Most clinical studies with non-cross resistant cytotoxic agents are lacking a strict definition of anthracycline resistance. A strict definition of anthracycline resistance implies progressive disease during anthracycline chemotherapy. Among the cytotoxic drugs only 5-Fluorouracil (given as 24 h continuous infusion with folinic acid) and the taxanes produce more than 20% objective remission (RR) in case of anthracycline resistance, whereas the highest response rate was reported for docetaxel (32-57%). Only few randomized studies were performed: docetaxel showed higher anti-tumor activity than methotrexat/5-FU (RR: 42% vs 19%, P<0.001) or mitomycin/vinblastine (RR: 30% vs 12%;P<0.001) and treatment with paclitaxel (175 mg/m(2)) was in favour to mitomycin (RR 17% vs 6%). In combination chemotherapy most activity have been reported for paclitaxel plus high-dose 5-fluorouracil (given as 24 h continuous infusion with folinic acid) (RR: 58%) or for docetaxel plus cisplatinum (RR: 46%). High-dose regimens with growth factor or stem cell support seems to be active in anthracycline-resistant disease but the toxicity is considerable. In conclusion, the taxanes, especially docetaxel as single agent or paclitaxel plus high-dose 5-FU, are the most promising therapeutic options in treatment of anthracycline resistant disease. Further clinical phase II/III studies in breast cancer should include exact definition of anthracycline pretreatment and resistance.
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PMID:Current options in treatment of anthracycline-resistant breast cancer. 1054 72

Overexpression of ErbB2 has been found in approximately 25-30% of human breast cancers and has been shown to render the cancer cells more resistant to chemotherapy. However, it is not clear whether ErbB2 overexpression renders the cells more resistant to specific anti-cancer drugs or renders the cells more resistant to a broad range of anti-cancer drugs. It is not clear how the function of ErbB2 in drug resistance is related to expression and activation of the other ErbB receptors. In this communication, we showed that several breast cancer cell lines including BT20, BT474, MCF-7, MDA-MB-453, and SKBR-3 cells had a similar pattern of resistance to a broad range of anti-cancer drugs including 5-Fluorouracil, Cytoxan, Doxorubincin, Taxol, and Vinorelbin, suggesting a mechanism of multidrug resistance. High expression of P-glycoprotein and the ErbB receptors contribute to drug resistance of these breast cancer cells; however, overexpression of ErbB2 alone is not a major factor in determining drug resistance. To further determine the role of the ErbB receptors in drug resistance, we selected various NIH 3T3 cell lines that specifically expressed EGF receptor (EGFR), ErbB2, ErbB3, EGFR/ErbB2, EGFR/ErbB3, or ErbB2/ErbB3. A cytotoxicity assay showed that expression of ErbB2 alone did not significantly enhance drug resistance, whereas coexpression of either EGFR or ErbB3 with ErbB2 significantly enhanced drug resistance. Moreover, ErbB2 was highly phosphorylated in NIH 3T3 cells that coexpress ErbB2 with either EGFR or ErbB3, but not in NIH 3T3 cells that express ErbB2 alone. Together, our results suggest that coexpression of EGFR or ErbB3 with ErbB2 induces high phosphorylation of ErbB2 and renders the cells more resistant to various anti-cancer drugs.
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PMID:Enhanced drug resistance in cells coexpressing ErbB2 with EGF receptor or ErbB3. 1106 25

Ceramide glycosylation, through glucosylceramide synthase (GCS), allows cellular escape from ceramide-induced programmed cell death. This glycosylation event confers cancer cell resistance to cytotoxic anticancer agents [Liu, Y. Y., Han, T. Y., Giuliano, A. E., and M. C. Cabot. (1999) J. Biol. Chem. 274, 1140-1146]. We previously found that glucosylceramide, the glycosylated form of ceramide, accumulates in adriamycin-resistant breast carcinoma cells, in vinblastine-resistant epithelioid carcinoma cells, and in tumor specimens from patients showing poor response to chemotherapy. Here we show that multidrug resistance can be increased over baseline and then totally reversed in human breast cancer cells by GCS gene targeting. In adriamycin-resistant MCF-7-AdrR cells, transfection of GCS upgraded multidrug resistance, whereas transfection of GCS antisense markedly restored cellular sensitivity to anthracyclines, Vinca alkaloids, taxanes, and other anticancer drugs. Sensitivity to the various drugs by GCS antisense transfection increased 7- to 240-fold and was consistent with the resumption of ceramide-caspase-apoptotic signaling. GCS targeting had little influence on cellular sensitivity to either 5-FU or cisplatin, nor did it modify P-glycoprotein expression or rhodamine-123 efflux. GCS antisense transfection did enhance rhodamine-123 uptake compared with parent MCF-7-AdrR cells. This study reveals that GCS is a novel mechanism of multidrug resistance and positions GCS antisense as an innovative force to overcome multidrug resistance in cancer chemotherapy.
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PMID:Ceramide glycosylation potentiates cellular multidrug resistance. 1125 90

To assess the therapeutic efficacy in the combination of mitomycin C (MMC), 5'-deoxy-5-fluorouridine (5'-DFUR), etoposide (VP-16) and medroxyprogesterone acetate (MPA) (McVD-MPA) to anthracycline-resistant tumor as a salvage chemotherapy, a phase II trial was conducted in patients with relapsed breast cancer. Fifty-five patients were enrolled in this trial and 54 were assessable, who had all previously been treated with an anthracycline regimen. The treatment schedule was designed with the intravenous administration of MMC (6 mg/m2) on day 1 followed by peroral administration of VP-16 (75 mg/m2) on day 2, 4, 6 and the peroral administration of 5'-DFUR (600 mg/m2) and MPA (400 mg/m2) on day 1 through 21 in one cycle. The overall tumor response rate was 40.7% (22/54) including 16.6% (9 cases) in complete response and 24.0% (13 cases) in partial response, and the long no change (NC) was observed in 18.5% (10/54) out of 44.4% (24/54) in NC. Of the patients with primary resistance to anthracycline 30.0% responded to McVD-MPA therapy. Bone and liver metastases responded in 50.0% and 50.0%, whereas soft tissue and lung metastases responded in 36.8% and 35.2%, respectively. The mean time to response and response duration were 2.7 and 15.6 months, respectively. The overall survival of the patient treated with the McVD-MPA was superior to the non-treatment of second line therapy, and the median survival between McVD-MPA and non-treatment was 86 days and 50 days, respectively. The major adverse effect was observed in hematological toxicity (31.7%) such as leukopenia and thrombocytopenia and non-hematological toxicity of gastrointestinal events (31.7%), the toxicity was less than grade 2, and was tolerable during the treatment. In the experiment of MDA-MB-231 breast cancer cell line that was overexpressed with P-glycoprotein (P-gp) and multidrug resistance associated protein (MRP), the mechanism(s) by which McVD-MPA induces the antitumor effect to anthracycline-resistant tumor may be explained at least in part as follows: i) The treatment of MMC suppressed the expression of P-gp and MRP in a dose-and time-dependent manner, connecting the increase of the intracellular concentration of VP-16; ii) The treatment of MMC enhanced the expression of thymidine phosphorylase to increase the production of 5-FU from 5'-DFUR in the antiangiogenic effect of MPA. These results indicate that the combination chemotherapy of the McVD-MPA may be an effective regimen to anthracycline-resistant tumor as a salvage chemotherapy to prolong the survival in the patient with relapsed breast cancer.
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PMID:A phase II trial of mitomycin C, 5'-deoxy-5-fluorouridine, etoposide and medroxyprogesterone acetate (McVD-MPA) as a salvage chemotherapy to anthracycline-resistant tumor in relapsed breast cancer and its mechanism(s) of antitumor action. 1129 87


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