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

P-glycoprotein (Pgp) is a trans-membraneous protein that is associated with multidrug resistance (MDR) in human cancer, including hepatocellular carcinomas and leukemias. There is no consensus regarding methods of choice for analysis of Pgp expression, and development of reliable analytical methods is now essential. We have studied the the Pgp expression in human hepatoma and leukemia cell lines using flow cytometry. The aim of the study was to compare binding properties of anti-Pgp antibodies reacting with surface (MRK16, UIC2) and cytoplasmic (C219, JSB-1) epitopes to assess which antibody performed best with respect to fluorescence discrimination. By histogram subtraction the fractions of resistant human hepatoma cells positive for Pgp were 99% (MRK16), 97% (UIC2), 77% (JSB-1), and 51% (C219), demonstrating variations in antibody reactivity. The resolution in detecting decreasing levels of Pgp in hepatoma cells was superior for the externally binding antibodies, showing that there is a correlation between antibody reactivity and fluorescence discrimination. Similar results were obtained for parental and resistant KG1a human leukemia cell lines. The Pgp epitopes remained reactive to the anti-Pgp MAbs after methanol fixation and cryopreservation. By dual parameter flow cytometry it was shown that Pgp expression in viable cells may be assessed together with uptake of epirubicin, which was low in cells expressing high levels of Pgp and vice versa. In conclusion, all tested antibodies proved useful for flow cytometric detection of high levels of Pgp, but the externally binding ones were superior in detection of low and variable levels of Pgp.
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PMID:Binding diversity of antibodies against external and internal epitopes of the multidrug resistance gene product P-glycoprotein. 758 8

The expression of multidrug resistance/P-glycoprotein genes mdr1b(mdr1) and mdr1a(mdr3) is elevated during hepatocarcinogenesis. To investigate the regulation of mdr1b gene expression, we used transient transfection expression assays of reporter constructs containing various 5'-mdr1b flanking sequences in hepatoma and non-hepatoma cells. We found that nucleotides -233 to -116 preferentially enhanced the expression of reporter gene in mouse hepatoma cell lines in an orientation- and promoter context-independent manner. DNase I footprinting using nuclear extracts prepared from hepatoma and non-hepatoma cells identified four protein binding sites at nucleotides -205 to -186 (site A), -181 to -164 (site B), -153 to -135 (site C), and -128 to -120 (site D). Further analyses revealed that, while site B alone played a major part for the enhancer function, sites A and B combined conferred full enhancer activity. Site-directed mutagenesis results also supported these results. Gel retardation experiments using oligonucleotide competitors revealed that the site B contains a dominant binding protein. This is the first report demonstrating a cell type-specific enhancer in the mdr locus. The role of this enhancer in the activation of mdr1b gene during hepatocarcinogenesis is discussed.
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PMID:Identification and characterization of a hepatoma cell-specific enhancer in the mouse multidrug resistance mdr1b promoter. 759 15

We compared the influence of exogenous N-ras oncogene and treatment with PKC agonist 12-O-tetradecanoylphorbol-13-acetate (TPA) on P-glycoprotein (Pgp) function in various human, rat and dog cell lines. Two approaches were used: (a) flow cytometry analysis of Rhodamine 123 (Rh123) exclusion; and (b) sensitivity to cytotoxic action of colchicine. We have found that in Rat1 fibroblasts, rat IAR2 epithelial cells and rat McA RH 7777 (hepatoma), ras activates Pgp function, while in MDCK (dog kidney), K562 (human chronic myelogenous leukaemia) and LIM1215 (human colon carcinoma) cells it either has no effect or even acts in opposite direction. TPA-induced Pgp function shows dissimilar pattern of cell specificity. It is assumed that PKC and ras oncogene regulate mdr1 gene expression through at least partially distinct signalling pathways.
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PMID:Cell-specific effects of RAS oncogene and protein kinase C agonist TPA on P-glycoprotein function. 762 41

Human liver carcinoma cells (BEL-7404) and human KB adenocarcinoma cells were selected by stepwise increases in cisplatin. Drug sensitivity assays indicated that the IC50 value for 7404-CP7.5 cells was 49 micrograms ml-1 cisplatin, 111-fold higher than for the parental hepatoma cells. The IC50 value for KB-CP10 cells was 38 micrograms ml-1 cisplatin, which is 1152-fold higher than for the parental KB cells. The 7404-CP7.5 cells were cross-resistant to methotrexate (39 x), 5-fluorouracil (23 x) and 6-mercaptopurine (13 x), but were sensitive to drugs which are known substrates for the multidrug transporter (P-glycoprotein), including colchicine, vinblastine and actinomycin D. Similar cross-resistance patterns were observed for KB-CP10 cells. No evidence of DNA amplification or expression of the MDR1 gene was found. One-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed increases in 52 kDa protein(s) in both the soluble cytosolic and crude membrane fractions in 7404-CP(r) cells and in KB-CP(r) cells. The amount of 52 kDa protein was proportional to the degree of resistance of the 7404-CP(r) cells to cisplatin. Two-dimensional gel analysis demonstrated that two polypeptides of molecular mass 52 and 50 kDa were overexpressed in the membrane fractions in both 7404-CP20 and KB-CP20 cells. Using amino acid microsequencing and Western blotting, major 52 kDa protein was identified as the mitochondrial heat shock protein hsp60. Two-dimensional gels of [35S]methionine-labelled polypeptides showed many other changes, including reduction in soluble proteins of approximately 57 kDa molecular weight in KB-CP20 cells, and of 35 kDa in both 7404-CP20 and KB-CP20 cells. These results suggest that alterations of certain proteins occur commonly in cisplatin-resistant cells, particularly proteins of molecular weight 52 and 50 kDa.
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PMID:Characterisation of high-level cisplatin-resistant cell lines established from a human hepatoma cell line and human KB adenocarcinoma cells: cross-resistance and protein changes. 771 Sep 28

BW502U83, an arylmethylaminopropanediol (AMAP), showed to be partially cross-resistant in a P-glycoprotein-positive and in a P-glycoprotein-negative, doxorubicin-resistant cell line, while no cross-resistance was noticed in a cisplatin-resistant cell line. Interstrand cross-links were not observed, but BW502U83 induced extensive DNA strand breaks. In a feasibility study the effect of intra-arterially BW502U83 was tested. One patient with a hepatocellular carcinoma showed partial remission and signs of a tumor lysis syndrome, another patient with a hepatocellular carcinoma improved clinically. A patient with soft tissue sarcoma had stable disease. Transient increase in SGOT, SGPT and LDH were observed, but no systemic side effects.
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PMID:In vitro and in vivo studies on the action of BW502U83, an arylmethylaminopropanediol. 775 81

Rifampicin, a semi-synthetic antibiotic used in the treatment of tuberculosis and belonging to the chemical class of rifamycins, was examined for its effect on anti-cancer drug accumulation and activity in multidrug resistant cells overexpressing P-glycoprotein (P-gp). Rifampicin was shown to strongly enhance vinblastine accumulation in both rat hepatoma RHC1 and human leukemia K562 R7 multidrug resistant cells, but had no effect in rat SDVI drug-sensitive liver cells. By contrast, two other rifamycins, rifamycins B and SV, had no or only minor effect on vinblastine accumulation in RHC1 cells. Efflux experiments revealed that rifampicin was able, like the well-known chemosensitizer agent verapamil, to decrease export of vinblastine out of resistant cells. Rifampicin, when used at a concentration close to plasma concentrations achievable in humans (25 microM), was able to increase sensitivity of RHC1 cells to both vinblastine and doxorubicin. Rifampicin was also demonstrated to inhibit P-gp radiolabeling by the photoactivable P-gp ligand azidopine, thereby suggesting that the antituberculosis compound can interfere directly with P-gp drug binding sites. These results thus indicate that rifampicin was able to down-modulate P-gp-associated resistance through inhibition of P-gp function.
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PMID:Rifampicin enhances anti-cancer drug accumulation and activity in multidrug-resistant cells. 776 6

The human MDR3 (or MDR2) P-glycoprotein is probably involved in the transport of phospholipids from liver hepatocytes into bile (Smit et al. (1993) Cell 75, 451-462). In accordance with this function, MDR3 is highly expressed in human liver, but lower mRNA levels were also found in adrenal, heart, muscle and cells of the B-cell compartment. We have cloned and analyzed the MDR3 promoter region. It is GC-rich, and contains neither a TATA nor a CAAT box, but it does contain multiple putative SP1 binding sites, features also found in so-called housekeeping genes. RNase protection and primer extension analyses indicate that the MDR3 gene has multiple transcription start sites in a GC-rich region with considerable homology to the putative mouse mdr2 promoter. A 3 kb genomic fragment containing the MDR3 start sites directs transcription of a chloramphenicol acetyltransferase (CAT) reporter gene upon transient transfection in the human hepatoma cell line HepG2. This transcription is orientation dependent, and stimulated by a SV40 enhancer, indicating that the 3 kb insert contains the core promoter elements of the MDR3 gene. The promoter region contains several consensus sequences where known or putative liver-specific (C/EBP, HNF5) or lymphoid specific (Pu.1, ets-1) transcription factors may bind.
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PMID:Characterization of the promoter region of the human MDR3 P-glycoprotein gene. 789 60

P-glycoprotein is a plasma-membrane glycoprotein involved in multidrug resistance. P-glycoprotein overexpression has been demonstrated to occur in tumor cells after cytotoxic drug exposure, but also in some cancers including hepatocellular carcinomas before any chemotherapeutic treatment. In order to better analyze this constitutive type of tumoral drug resistance, we have investigated P-glycoprotein expression and function in rat liver tumors induced experimentally by administration of diethylnitrosamine and in two cell clones derived from one of these tumors designated as RHC1 and RHC2. High levels of P-glycoprotein mRNAs were found in both liver tumor samples and the two hepatoma cell clones as assessed by Northern blotting; both RHC1 and RHC2 cells displayed altered liver functions commonly observed in rat hepatoma cells, particularly the decreased expression of albumin and overexpression of the fetal glutathione S-transferase 7-7. The use of specific multidrug resistance (mdr) probes revealed a major induction of the mdr1 gene in liver tumor samples while RHC1 and RHC2 cells expressed both mdr1 and mdr3 genes without displaying a major alteration in the number of mdr gene copies as assessed by Southern blotting. High amounts of P-glycoprotein were also demonstrated in RHC1 and RHC2 cells by Western blotting. These cells were strongly resistant to doxorubicin and vinblastine, two anticancer drugs transported by P-glycoprotein. Doxorubicin intracellular retention was low in RHC1 and RHC2 cells, but was strongly enhanced in the presence of verapamil, a known modulator agent of P-glycoprotein; low retention appeared to occur via a drug efflux mechanism, indicating that P-glycoprotein was fully active. These results show that rat hepatoma cells can display elevated levels of functional P-glycoprotein without any prior cytotoxic drug selection and suggest that these cells represent a useful model for analyzing P-glycoprotein regulation in intrinsically clinical drug-resistant cancers.
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PMID:Constitutive expression of functional P-glycoprotein in rat hepatoma cells. 790 26

Yoshida rat ascites hepatoma (AH) has several cell lines with a characteristic sensitivity to antitumor drugs. AH66 cells overexpressed 160-170 kDa P-glycoprotein (P-gp) in the membrane and glutathione-S-transferase placental form (GST-P) in the cytosol. AH44 cells did not express P-gp but contained GST-P isozyme, while normal rat liver had GST-(1,2) and-(3,4) classes. AH44 and AH66 cells were more resistant to chlorambucil (CLB) than AH66F cells, which are a variant cell line derived from AH66 cells and lacked both proteins. CLB-resistant AH44 and AH66 cells contained a high amount of glutathione (GSH) and higher GST activity than AH66F cells. Ethacrynic acid, a GST-P inhibitor, and buthionine sulfoximine, a GSH biosynthesis inhibitor, significantly decreased the CBL resistance of AH44 and AH66 cells without influencing the sensitivity of AH66F cells. The CLB resistance of these cell lines were hardly influenced by verapamil, a calcium channel blocker with P-gp antagonistic action, which significantly decreased the vinblastine resistance of AH66 cells. This study indicates that AH66 cells showed multiple drug resistance dependent on P-gp and GST-P isozyme and that the AH44 cell line was CLB resistant through the GSH/GST-P detoxification system. These hepatomas are useful for investigation of the drug resistance of hepatic carcinomas and development of counteracting drugs.
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PMID:Glutathione-S-transferase P-form dependent chlorambucil resistance in Yoshida rat ascites hepatoma cell lines. 791 Jan 11

To study the effect of bile acids on P-glycoprotein-mediated drug transport, we performed experiments using multidrug resistant cells and rat canalicular membrane vesicles. Cellular accumulation and efflux of rhodamine 123 were measured in drug-resistant cells by means of computerized quantitative image analysis and fluorescence microscopy. ATP-dependent [3H]daunomycin transport was studied by means of rapid filtration in canalicular membrane vesicles prepared from normal rats. Doxorubicin-sensitive (PSI-2) and -resistant (PN1A) 3T3 cells and human-derived hepatocellular carcinoma doxorubicin-sensitive and -resistant cells were used. Taurochenodeoxycholate and glycochenodeoxycholate, taurolithocholate and ursodeoxycholate (50 to 200 mumol/L) inhibited rhodamine 123 and [3H]daunomycin transport in multidrug-resistant cells and canalicular membrane vesicles, respectively, whereas taurocholate, taurodeoxycholate and tauroursodeoxycholate did not. Primary and secondary unconjugated bile acids had no effect. These results reveal that taurolithocholate, taurochenodeoxycholate and glycochenodeoxycholate and ursodeoxycholate inhibit P-glycoprotein-mediated drug transport function in multidrug resistant cell lines and in canalicular membrane vesicles. These results suggest possible interaction between P-glycoprotein function and bile acids in cholestasis and after treatment of patients with ursodeoxycholic or chenodeoxycholic acid.
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PMID:Bile acid inhibition of P-glycoprotein-mediated transport in multidrug-resistant cells and rat liver canalicular membrane vesicles. 791 87


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