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)

P-Glycoprotein and C-MOAT are important hepatic transport proteins which play a role in handling anticancer drugs. Hepatocellular carcinoma is a common hepatic malignancy that is relatively resistant to chemotherapeutic drugs. We therefore studied the expression of these two transport proteins in liver sections from hepatocellular carcinoma by immunohistochemistry and compared the reactivity to that in other liver conditions, including cirrhosis and dysplasia. We studied 53 sections from 17 liver specimens and found that the majority of samples stained positively for both P-glycoprotein and C-MOAT; however, the degree of staining was less in HCC and hepatic adenoma than in liver adjacent to HCC or in cirrhosis or dysplastic nodules. HCC with a compact pattern had less staining than those with acinar, scirrhous, or trabecular patterns. The location of both P-glycoprotein and C-MOAT staining was a function of the liver lesion present. Thus, most tissues without hepatocellular carcinoma showed foci of globular canalicular staining, whereas a delicate linear pattern of canalicular staining was most common overall. We conclude that expression of P-glycoprotein and C-MOAT, as detected by qualitative immunohistochemical evaluation are little affected by the development of HCC and therefore are probably of little clinical significance for management of malignancy.
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PMID:Expression of P-glycoprotein and C-MOAT in human hepatocellular carcinoma: detection by immunostaining. 1245 78

The present study explores the hypothesis that over-expression of P-glycoprotein (Pgp, product of mdr1) is intimately associated with liver cancer development and therefore inhibitors of Pgp should inhibit the development of liver cancer. Accordingly, we determined the effect of PSC833 (PSC), a potent inhibitor of Pgp, on experimental liver carcinogenesis in rats. To study the effects of PSC on liver cancer development, a daily dose of 30 mg PSC/kg body wt (PSC30) was chosen based on an initial dose-response experiment. Accordingly in experiment 1, PSC30 was fed to rats initiated by 1,2-dimethylhydrazine coupled with two-thirds partial hepatectomy and promoted for 22 weeks with 1% dietary orotic acid. Surprisingly, in contrast to our earlier observations in rats without hepatic nodules, in rats bearing hepatic nodules, PSC30 was found to be toxic. Because of this, PSC30 diet was discontinued after 5 weeks and the rats were transferred to basal diet (BD). The rats were killed 10 and 25 weeks thereafter. Cumulative results indicate that PSC30 exhibited a 40% decrease in the incidence of hepatocellular carcinoma (HCC; 15 of 18 in the BD group compared with eight of 17 in the PSC30 group; P = 0.08) coupled with significant reduction of tumor multiplicity (54%; P < 0.05) and tumor burden (61%; P < 0.005) compared with controls. In experiment 2, 15 mg PSC/kg body wt (PSC15) was fed for 20 weeks to rats similarly initiated and promoted for 35 weeks. PSC15 inhibited the incidence of HCC by 75% (four of four in the BD group compared to one of four in the PSC30 group; P = 0.15) and significantly reduced tumor burden by 55% (P < 0.05). The lack of statistical significance of inhibition on tumor incidence reflects the small sample size. Taken together the results indicate a possible intrinsic role for Pgp in liver cancer development and introduce another promising unexplored therapeutic approach in liver cancer treatment.
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PMID:Effect of PSC 833, an inhibitor of P-glycoprotein, on 1,2-dimethylhydrazine-induced liver carcinogenesis in rats. 1297 66

Primary hepatocellular carcinoma is the third most common fatal cancer worldwide with more than 500,000 annual deaths. Approximately 40% of the patients with HCC showed tumoral overexpression of transmembrane proteins belonging to the ATP-binding cassette protein superfamily (ABC) which pump drugs out of cells. The overexpression of these efflux transporters confers on the cells a multiple drug resistance phenotype, which is considered a crucial cause of treatment refractoriness in patients with cancer. The aim of this study was to investigate the inhibitory effect of different concentrations of pH- and temperature-responsive X-shaped poly(ethylene oxide)-poly(propylene oxide) block copolymers (poloxamines, Tetronic, PEO-PPO) showing a wide range of molecular weights and EO/PO ratios on the functional activity of three different ABC proteins, namely P-glycoprotein (P-gp or MDR1), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein MRP1, in two human hepatocarcinoma cell lines, HepG2 and Huh7. First, the cytotoxicity of the different copolymers (at different concentrations) on both liver carcinoma cell lines was thoroughly evaluated by means of apoptosis analysis using annexin V and propidium iodide (PI). Thus, viable cells (AV-/PI-), early apoptotic cells (AV+/PI-) and late apoptotic cells (V-FITC+/PI+) were identified. Results pointed out copolymers of intermediate to high hydrophobicity and intermediate molecular weight (e.g., T904) as the most cytotoxic. Then, DiOC2, rhodamine 123 and vinblastine were used as differential substrates of these pumps. HeLa, an epithelial cell line of human cervical cancer that does not express P-gp, was used exclusively as a control and enabled the discerning between P-gp and MRP1 inhibition. Moderate to highly hydrophobic poloxamines T304, T904 and T1301 showed inhibitory activity against P-gp and BCRP but not against MRP1 in both hepatic cell lines. A remarkable dependence of this effect on the copolymer concentration and hydrophobicity was found. No inhibitory effect against these ABC pumps was observed with the hydrophilic T1107. These findings further evidence the potential usefulness of these Trojan horses as both drug nanocarriers and ABC inhibitors in hepatic MDR tumors and infections that involve the activity of these efflux transporters.
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PMID:Poloxamines display a multiple inhibitory activity of ATP-binding cassette (ABC) transporters in cancer cell lines. 2159 27

Mitochondria play a crucial role in pathways of stress conditions. They can be transported from one cell to another, bringing their features to the cell where they are transported. It has been shown in cancer cells overexpressing multidrug resistance (MDR) that mitochondria express proteins involved in drug resistance such as P-glycoprotein (P-gp), breast cancer resistant protein and multiple resistance protein-1. The MDR phenotype is associated with the constitutive expression of COX-2 and iNOS, whereas celecoxib, a specific inhibitor of COX-2 activity, reverses drug resistance of MDR cells by releasing cytochrome c from mitochondria. It is possible that COX-2 and iNOS are also expressed in mitochondria of cancer cells overexpressing the MDR phenotype. This study involved experiments using the human HCC PLC/PRF/5 cell line with and without MDR phenotype and melanoma A375 cells that do not express the MDR1 phenotype but they do iNOS. Western blot analysis, confocal immunofluorescence and immune electron microscopy showed that iNOS is localized in mitochondria of MDR1-positive cells, whereas COX-2 is not. Low and moderate concentrations of celecoxib modulate the expression of iNOS and P-gp in mitochondria of MDR cancer cells independently from inhibition of COX-2 activity. However, A375 cells that express iNOS also in mitochondria, were not MDR1 positive. In conclusion, iNOS can be localized in mitochondria of HCC cells overexpressing MDR1 phenotype, however this phenomenon appears independent from the MDR1 phenotype occurrence. The presence of iNOS in mitochondria of human HCC cells phenotype probably concurs to a more aggressive behaviour of cancer cells.
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PMID:Mitochondria of a human multidrug-resistant hepatocellular carcinoma cell line constitutively express inducible nitric oxide synthase in the inner membrane. 2569 Oct 7

We herein examined the immunohistochemical expression of 2 hepatocyte-specific transporters (bile salt export pump [BSEP] and multidrug-resistance protein 3 [MDR3]) in hepatocellular carcinomas (HCCs, n=54), intrahepatic cholangiocarcinomas (n=34), combined hepatocellular and cholangiocarcinomas (n=23), and hepatoid carcinomas originated from extrahepatic organs (n=27) to compare their diagnostic values with those of arginase-1 (ARG1) and hepatocyte paraffin-1 (HepPar-1). BSEP was expressed in 91% of HCCs and MDR3 in 83%. Although their sensitivities were slightly lower than those of ARG1 (96%) and HepPar-1 (93%), the 2 transporters appeared to be more specific for HCCs. ARG1 and HepPar-1 were expressed in intrahepatic cholangiocarcinomas (9% and 6%) and hepatoid carcinomas (22% and 44%, respectively), whereas BSEP and MDR3 were entirely negative in these neoplasms, except for 1 case of BSEP-positive hepatoid carcinoma of the esophagus. The highly specific expression of BSEP and MDR3 in hepatocytes was recapitulated in additional examinations of combined hepatocellular and cholangiocarcinomas, in which the expression of the transporters was restricted to morphologically hepatocellular areas. In contrast, ARG1 and HepPar-1 were also variably positive in areas of biliary or indeterminate differentiation. We also applied BSEP and MDR3 immunohistochemistry to 8 biopsy cases of poorly differentiated primary liver cancer, in which the original diagnosis was not conclusive. The diagnosis of HCC was retrospectively suggested in 2 cases expressing both BSEP and MDR3. In conclusion, given the highly specific expression of BSEP and MDR3 in HCCs, immunohistochemistry for these transporters will be useful not only for determining hepatocellular differentiation in primary liver cancers but also for discriminating HCCs from hepatoid carcinomas.
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PMID:BSEP and MDR3: Useful Immunohistochemical Markers to Discriminate Hepatocellular Carcinomas From Intrahepatic Cholangiocarcinomas and Hepatoid Carcinomas. 2673 60