Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of the MDR1 gene, which encodes P-glycoprotein, is increased under some stress conditions. We have reported that quercetin, a bioflavonoid, inhibits the expression of heat-shock proteins. We have identified the effects of quercetin on the MDR1 gene expression in the human hepatocarcinoma cells line, HepG2. The increase of P-glycoprotein synthesis and MDR1 mRNA accumulation caused by exposure to arsenite were inhibited by quercetin. The CAT assay suggested that quercetin suppressed the transcriptional activation of the MDR1 gene after exposure to arsenite. Although many drugs that prevent the P-glycoprotein function have been reported, this is the first report to describe the inhibition of MDR1 expression by a reagent.
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PMID:Quercetin, a bioflavonoid, inhibits the increase of human multidrug resistance gene (MDR1) expression caused by arsenite. 134 37

ML-9, an inhibitor for myosin light chain kinase, and W-7, a calmodulin inhibitor, suppressed the efflux of vinblastine and increased the intracellular accumulation of vinblastine, but W-5, an inactive compound for calmodulin, did not so in rat ascites hepatoma AH66 cells, which have a multidrug-resistant phenotype. In sensitive counterpart AH66F cells, W-7 and ML-9 were less effective. W-7 and ML-9 did not interfere with [3H]azidopine photolabeling of P-glycoprotein in the plasma membrane from AH66 cells. While P-glycoprotein is reported to be superphosphorylated by protein kinases, W-7 did not influence the phosphorylation of the P-glycoprotein in AH66 cells. There may be an unknown Ca(2+)-calmodulin-dependent mechanism in the extrusion of vinblastine from AH66 cells.
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PMID:Increase of vinblastine accumulation by inhibitors of calmodulin-dependent cell functions in rat ascites hepatoma AH66 cells. 136 14

Rat ascites hepatoma AH66 cells have lower sensitivity to Vinca alkaloids and anthracycline antibiotics than AH66F cells, a subline of AH66 cells. AH66 cells expressed P-glycoprotein, while the protein was not detectable in AH66F cells. There are two affinity sites for [3H]vinblastine binding in the AH66 cell membrane, while AH66F cells have only one affinity site. The high affinity [3H]vinblastine binding in AH66 cells was inhibited by Adriamycin, verapamil, nicardipine, and reserpine. The high affinity site of the binding may be the multidrug transporter, P-glycoprotein. [3H]Vinblastine binding was not influenced by adenosine 3'-5'-monophosphate (AMP), adenosine triphosphate (ATP), or guanosine triphosphate (GTP). The multidrug resistance in AH66 cells may depend on P-glycoprotein which is not modulated by nucleotide.
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PMID:Sensitivity to antitumor drugs and vinblastine binding to membrane in rat ascites hepatoma AH66 cells. 142 78

Rat ascites hepatoma (AH) cell lines that were induced by dimethylaminoazobenzene and established as transplantable tumors had different sensitivities to vinblastine (VBL). The most VBL-resistant cells, AH66, showed more cross-resistance to vincristine and anthracyclines than AH66F cells. The resistance of AH66 cells was significantly decreased by verapamil. VBL-resistance of AH66 cells was inhibited by other drugs reported as overcoming acquired multidrug resistance, while the sensitivity of AH66F cells was hardly influenced by these drugs. The lowered uptake and enhanced extrusion of the antitumor drug in AH66 cells were suppressed by verapamil. M(r) 160,000 protein in the plasma membrane from AH66 was labeled with a photoactive VBL analog and was immunopositive to a monoclonal antibody against P-glycoprotein, C219. The sensitive cells had barely detectable levels of the surface membrane components. Specific photo-labeling with a VBL analog of P-glycoprotein of AH66 cell membrane was inhibited by reserpine and verapamil which restored the VBL resistance. These results indicate that AH66 cells are a naturally acquired multidrug-resistant cell line overexpressing a P-glycoprotein, and AH cell lines are useful to study multidrug resistance of hepatic carcinomas and development of counteracting drugs.
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PMID:Multidrug resistance in Yoshida rat ascites hepatoma cell lines. 162 21

Multidrug resistance of human cancer cells may result from expression of P-glycoprotein, the product of the MRD1 gene, acting as an energy-dependent drug efflux pump. However, direct evidence that expression of the MDR1 gene contributes to the multidrug resistance of human liver carcinomas has not been established. In this study, we tested five cell lines derived from human hepatocellular carcinomas for sensitivity to a variety of drugs used widely as anticancer agents; these included vinblastine, doxorubicin, actinomycin D, mitomycin C, 5-fluorouracil, 6-mercaptopurine, melphalan, methotrexate, cis-platinum and etoposide (VP-16). All five hepatoma cell lines were resistant at different levels to these chemicals compared to human KB cells. Although it has been demonstrated that resistance to vinblastine, colchicine, doxorubicin and actinomycin D in human multidrug-resistant cells is associated with overexpression of P-glycoprotein, very little expression of P-glycoprotein was found in these human hepatoma cells. Neither verapamil nor quinidine, inhibitors of the drug efflux pump, were able to overcome multidrug resistance in hepatoma cells. These results indicate that the multidrug resistance phenotype in human hepatocellular carcinoma cells cannot be attributed to expression of the MDR1 gene, but that novel mechanisms may account for the resistance of these cancer cells.
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PMID:Human hepatocellular carcinoma cell lines exhibit multidrug resistance unrelated to MRD1 gene expression. 167 33

Dipyridamole (DPM) at 10 microM enhanced the cytotoxicity of anti-tumor drugs, which were associated with multidrug resistance, more in multidrug-resistant human hepatoma PLC/PRF/5 cells (PLC/COL) than in its parental cells (PLC/S). DPM increased, dose-dependently, the intracellular accumulation of [3H]vinblastine in PLC/COL. However, the effect was immediately diminished by its removal from the medium, indicating that DPM needed to be present together with the anti-tumor drugs to enhance the intracellular accumulation of the drugs. DPM inhibited the efflux of [3H]vinblastine from the PLC/COL cells, the binding of [3H]vinblastine to membrane vesicles of PLC/COL, and the binding of [3H]azidopine to P-glycoprotein in the plasma membrane of PLC/COL. Apparently DPM binds to P-glycoprotein and inhibits active efflux. [14C]labeled DPM was quickly incorporated into the cells and the cellular level of [14C]DPM reached a plateau after 5 min. It was slightly higher in PLC/S than in PLC/COL. The cellular [14C]DPM quickly disappeared after its removal from the medium. These results indicate that DPM binds quickly but reversibly to various kinds of cellular proteins including P-glycoprotein and inhibits active efflux of some anti-tumor drugs in multi-drug-resistant tumor cells, resulting in the enhancement of the activities of these drugs.
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PMID:Enhancement of activities of anti-tumor drugs by dipyridamole against multidrug-resistant human hepatoma PLC/PRF/5 cells. 167 5

We have previously shown that the multidrug-resistance/P-glycoprotein gene, mdr3/mdr1a, is activated in mouse hepatocellular carcinomas (HCC). In this study, we show that in a number of HCC-derived cell lines (Hepa1c1c, Hepa1c1c-BprC1, and Hepa1-6) mdr3 is expressed at high levels. To investigate transcriptional regulation of mdr3 in these cells, we have isolated a DNA fragment containing the 5' portion of the mouse mdr3 gene and performed a functional analysis of its promoter. Transient transfection assays using various lengths of the promoter sequence to direct expression of the chloramphenicol acetyltransferase (CAT) reporter gene revealed that the sequence located -94 nucleotides upstream from mouse mdr3 transcription start site functions as a negative element in mouse hepatoma cells. A canonical AP-1 binding sequence TGA-GTCA located at -117 is at least in part responsible for the negative effect from the following observations: (i) Alteration of this AP-1 sequence by site-directed mutagenesis enhanced CAT expression. (ii) Expression of CAT reporter gene was elevated when double-stranded DNA containing the AP-1 sequence, but not mutated sequences, was used as a competitor in cotransfection experiment. (iii) Enhancement of the CAT expression was also seen in cotransfection experiments using recombinant plasmid DNA expressing the c-jun/c-fos proteins, which interact with AP-1 sequences. Interestingly, the proximal region of the hamster pgp1 promoter shares striking sequence similarity with that of the mouse mdr3 gene, including the AP-1 site, but the AP-1 site in the hamster promoter serves as a positive regulator. Although previous studies have demonstrated that positive and negative transcription factors can modulate gene expression through interactions with c-jun/c-fos, this is the first study to show that an AP-1 site functions as a negative cis-element in the regulation of gene expression.
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PMID:Structural and functional analyses of the promoter of the murine multidrug resistance gene mdr3/mdr1a reveal a negative element containing the AP-1 binding site. 168 3

Intrinsic and acquired multidrug resistance is an important problem in cancer therapy. Multidrug resistance results from overexpression of the MDR 1 gene, which encodes a drug-efflux pump called P-glycoprotein. We have isolated a 1-kilobase genomic fragment containing the major transcription initiation sites for the human MDR 1 gene. Ribonuclease protection experiments using this fragment indicate that normal human adrenal, colon, and liver cells, the human hepatoma cell line HepG2, and vinblastine-selected human KB multidrug-resistant cells initiate transcription of the MDR 1 gene at the same site within this fragment. The 0.43-kilobase region upstream from the major transcription initiation site linked to the chloramphenicol acetyltransferase gene showed promoter activity in CV-1 monkey kidney cells and in human KB cells. The putative promoter region has a consensus CAAT box and two GC box-like sequences, but no TATA sequence. This identification and isolation of promoter sequences for the MDR 1 gene will permit studies on how expression of this gene is regulated in normal human tissues and cancers.
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PMID:Isolation and sequence of the promoter region of the human multidrug-resistance (P-glycoprotein) gene. 289 92

Adenomatous hyperplasia in the human liver with cirrhosis is similar to the hyperplastic nodule in rat hepato-carcinogenesis in that the mdr gene or its product P-glycoprotein is overexpressed. We immunohistochemically stained archival formalin-fixed, paraffin-embedded sections of 15 adenomatous hyperplasias with or without hepatocellular carcinoma in livers with cirrhosis, using the avidin-biotin-complex method and the JSB-1 monoclonal antibody which specifically binds the cytoplasmic epitope of P-glycoprotein. Of 15 cases with adenomatous hyperplasia, four were found solely in livers with cirrhosis. In six cases, adenomatous hyperplasia and hepatocellular carcinoma were found in the same liver separately. Hepatocellular carcinoma was discovered within adenomatous hyperplasia in five cases. All 15 livers with cirrhosis and those with adenomatous hyperplasia were positively stained for P-glycoprotein. When the grade of staining was compared between adenomatous hyperplasia and the surrounding liver, P-glycoprotein was overexpressed in 12 of 15 cases with adenomatous hyperplasia. P-glycoprotein was also stained more strongly in well-differentiated hepatocellular carcinoma than in the liver, but the staining grade of hepatocellular carcinoma was weaker than that of adenomatous hyperplasia. Moreover, the glycoprotein expression was less when the tumor was less differentiated.
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PMID:Overexpression of P-glycoprotein in adenomatous hyperplasia of human liver with cirrhosis. 754 Jun 36

P-glycoprotein (P-gly), which is responsible for the phenotypic expression of multidrug resistance in cancerous tissue was stained immunohistochemically in previously untreated alpha-fetoprotein (AFP)-producing (n = 20) and nonproducing gastric cancers (n = 20). P-gly, AFP, and carcinoembryonic antigen(CEA) were stained in formalin-fixed paraffin-embedded tissue sections immunohistochemically using the monoclonal antibody JSB-1, anti-AFP, and anti-CEA, respectively. DNA ploidy pattern was determined by Fluorescence Activated Cell Sorter (FACS) analyzer. P-gly was significantly overexpressed in AFP producing gastric cancers (60%) than in AFP nonproducing ones (20%) (P < 0.01). When the result of P-gly staining was analyzed among the AFP-positive cases, P-gly positivity did not emerge either as a significant prognostic factor or as a predictor of the metastatic potentiality of the tumor. The intrinsic overexpression of P-gly in AFP producing gastric cancers proves its biological and morphological similarities to hepatocellular carcinoma. The significantly (P < 0.05) higher incidence of P-gly in diploid tumors indicate that expression of this phenotype might be related to the differentiation of the tumor. P-gly was overexpressed in AFP producing gastric carcinoma and the existing drug resistance, frequent recurrence, and poor prognosis might be explained by presence of P-gly in this carcinoma.
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PMID:Overexpression of P-glycoprotein in untreated AFP-producing gastric carcinoma. 754 56


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