Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0376358 (prostate cancer)
 59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microtubules, which are composed of polymerized tubulin dimers, play an important role in various cell functions. For example, they maintain cell shape, form mitotic spindles in M phase of cell cycle, and carry an axonal transport in nerve cells. Microtubules have also been an important target of cancer chemotherapy. Vinca alkaloids depolymerize microtubules, the mechanisms of which action have extensively been investigated recently. Clinical trials of vinorelbine (navelbine), a new semisynthetic vinca alkaloid, are ongoing in Japan. One of advantages of the drug is reduced risk of neurotoxicity. Estramustine may act on microtubule-associated proteins (MAPs) as well as tubulin. It shows additive or synergistic cytotoxicity preclinically when used in combination with vinblastine. This combination was active against hormone-refractory prostate cancer. Another novel drug rhizoxin, which has a similar mechanism of action to that of vinca alkaloids, is also a promising cytotoxic agent and is examined clinically in Europe. Taxanes, which include paclitaxel (Taxol) and taxotere, are interesting drugs because they promote polymerization of tubulin and stabilize microtubules. They show promising antitumor activity against breast, ovarian and lung cancers. Phase I and II trials are ongoing in Japan. Paclitaxel may also potentiate cytotoxicity of radiation. There are several mechanisms of resistance to microtubule-acting drugs. One is multidrug resistance mediated by P-glycoprotein. Other mechanisms include mutation of tubulin.
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PMID:[Microtubules and antineoplastic drugs]. 790 90

The treatment of advanced metastatic prostate cancer by hormone manipulation or orchiectomy is frequently followed by the appearance of hormone-insensitive and highly chemoresistant tumor cells. In this study we have investigated the contribution of the P-glycoprotein-mediated drug efflux (multidrug-resistance; MDR) to the cellular resistance of prostate carcinoma-derived cell lines to diverse cytotoxic drugs by detection of P-glycoprotein (P-gp) measurement of P-gp-mediated drug transport and reversal of MDR by chemosensitizers. The in vitro chemosensitivity of three prostate cancer cell lines (PC-3, DU-145 and LNCaP) to doxorubicin was measured in a thymidine incorporation proliferation assay. Growth of the partially hormone-sensitive cell line LNCaP is inhibited by low doses of doxorubicin (IC50:27 ng./ml.), but PC-3 and DU-145 are highly resistant to the drug, with IC50 values of 10 micrograms./ml. and 7.5 micrograms./ml., respectively. The chemosensitivity of the PC-3 and DU-145 cells is increased in response to 1 microM. verapamil, 1 micrograms./ml. cyclosporine A and 2 microM. tamoxifen, which are known to partially reverse the MDR phenotype in other resistant tumors. A verapamil-sensitive drug efflux has been demonstrated for the PC-3 and Du-145, but not for the LNCaP, cell lines, using flow cytometric measurements of the P-gp substrate rhodamine 123 efflux from preloaded cells. In agreement with the functional measurements, the expression of the P-glycoprotein was detected in the PC-3 and Du-145 cell lines in Western blots using the monoclonal C 219 antibody. In conclusion, the chemoresistant and hormone-insensitive PC-3 and Du-145 cell lines express P-gp and exhibit verapamil-sensitive drug efflux, indicative of MDR. However, the low MDR-reversal rates observed in these cell lines in response to chemosensitizers in clinically achievable concentrations (approximately 2- to 3-fold reversal), point to non-MDR-associated cellular mechanisms as dominant factors of chemoresistance in prostate cancer.
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PMID:Role of the MDR-1-encoded multiple drug resistance phenotype in prostate cancer cell lines. 810 10

The effects of combining estramustine (EM) with vinblastine (VLB) or doxorubicin (DOX) on cellular uptake, cellular retention and cell survival were investigated in Dunning hormone-insensitive rat prostate AT-1 tumor cells and DU-145 human prostatic tumor cells. Accumulation of VLB and DOX by AT-1 cells was less than one-half of that in DU-145 cells. Inclusion of EM or estromustine considerably increased uptake of both VLB and DOX in AT-1 cells but not in DU-145 cells. Verapamil and tamoxifen also potentiated VLB uptake in AT-1 cells. A combination of VLB and EM resulted in a considerable synergistic effect on both cytotoxicity and cellular retention of VLB. The presence of P-glycoprotein (Pgp) in AT-1 cells could be demonstrated by both Western blots and immunocytochemical detection. Photoaffinity labeling of Pgp by [3H]-azidopine was clearly inhibited by VLB, verapamil and EM. Our data strongly support the argument for a combination of EM with not only VLB but also DOX to improve the therapeutic index in patients with prostate cancer.
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PMID:Potentiation by estramustine of the cytotoxic effect of vinblastine and doxorubicin in prostatic tumor cells. 893 48

Estramustine phosphate (EMP) is thought to form a chemical link between estradiol and non-nitrogen mustard. An estramustine-binding protein has been isolated in prostate, breast, and brain cancers as well as in malignant melanoma cells. Estramustine phosphate's ability to bind to microtubular-associated proteins and to interfere with mdr-mediated drug efflux are thought to result in its enhancement of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) activity in cell lines and in its ability to affect hormone-resistant prostate cancer. This phase I study administered combined paclitaxel and EMP to 25 women with ovarian, breast, and other tumors and assessed efficacy and toxicity. Estramustine phosphate was administered at two dose levels, 900 or 1,200 mg/m2 daily on days 1, 2, and 3 in 3-week cycles. On day 3, paclitaxel (150, 180, 210, or 225 mg/m2) was given concomitantly by 3-hour infusion. Therapeutic effects were noted in all patients. Partial responses were noted in three of eight patients with breast cancer who had failed to improve on paclitaxel alone. Three other patients experienced prolonged stable disease. Only moderate toxicities were noted until EMP levels of 1,200 mg/m2 were reached. At these dose levels, gastrointestinal toxicities became more prominent. The addition of EMP to paclitaxel allowed patients to receive paclitaxel for longer periods, and may have enhanced the therapeutic effects of paclitaxel. If so, the mechanisms of such enhancement warrant investigation. The two drugs may work on different aspects of microtubular function, for example, or may reduce efflux of paclitaxel in P-glycoprotein overexpressed tumors.
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PMID:Response to estramustine phosphate and paclitaxel in patients with advanced breast cancer: a phase I study. 907 37

Prostate cancer progresses from a localized disease to a widely disseminated malignancy. Each step along this progression pathway involves multiple genetic alterations that impart a survival advantage to the tumor cell over its normal counterparts and may confer resistance to therapy. Because metastatic prostate cancer is one of the most therapy-resistant human neoplasms, we studied the expression of certain molecular determinants of drug resistance in the context of tumor progression. Paraffin-embedded formalin-fixed resected prostates were chosen based on Gleason grade and surgical stage. Immunohistochemistry was used to detect the expression of multidrug resistance protein (MRP), topoisomerase II alpha, p53, glutathione S-transferase pi, Bcl-2, and P-glycoprotein in these specimens. We found that all of the proteins were expressed in resected prostate except for P-glycoprotein. The expression of MRP, topoisomerase II alpha, p53, and Bcl-2 increased with the Gleason grade. In addition, the expression of MRP, topoisomerase II alpha, and p53 increased with the surgical stage. In contrast, the glutathione S-transferase pi and Bcl-2 expression decreased with the increasing surgical stage. Stage was the strongest indicator of protein expression. These results suggest that drug resistance gene products are expressed in prostate cancer at the time of surgical resection. Thus, although the emergence of the "pan-resistance" phenotype in prostate cancer may partly be a function of the selection pressure exerted by therapeutic interventions, certain determinants of chemoresistance may be caused by genetic changes accompanying tumorigenesis.
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PMID:The expression of drug resistance gene products during the progression of human prostate cancer. 962 55

The sensitivity of human tumor and rat prostate tumor cells to a series of naphthoquinones, including tricyclic compounds of the beta-lapachone and dunnione families as well as 4-alkoxy-1,2-naphthoquinones, was evaluated. To better understand the mechanism of cytotoxicity of 1,2-naphthoquinones, the roles of various resistance mechanisms including P-glycoprotein, multidrug resistant associated protein, glutathione (GSH) and related enzymes, altered topoisomerase activity, and overexpression of genes that control apoptosis (bcl-2 and bc-xL) were studied. MCF7 cells were most sensitive to the naphthoquinones with IC50 values ranging from 1.1 to 10.8 microM, as compared to 2.5 to >32 microM for HT29 human colon, A549 human lung, CEM leukemia and AT3.1 rat prostate cancer cells. MCF7 ADR cells, selected for resistance to adriamycin (ADR), displayed cross-resistance to the tricyclic 1,2-naphthoquinones. Drug efflux via a P-glycoprotein mechanism was ruled out as a mechanism of resistance to 1,2-naphthoquinones, since KB-V1 cells expressing high levels of P-glycoprotein and the KB-3.1 parent line were equally sensitive to these compounds. Any resistance of the tricyclic naphthoquinones noted in ADR-resistant cells appeared to relate to the GSH redox cycle and could be circumvented by exposure to buthionine sulfoximine or by changing the structure from a tricyclic derivative to a 4-alkoxy-1,2-naphthoquinone. The 1,2-naphthoquinones were found to be cytotoxic against CEM/VM-1 and CEM/M70-B1 cells that were selected for resistance to teniposide or merbarone, respectively. In addition, cells overexpressing bcl-2 or bcl-xL proteins were as sensitive to 1,2-naphthoquinones as were control cells. Because of their effectiveness in drug-resistant cells, these agents appear to hold promise as effective chemotherapeutic agents.
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PMID:Effects of 1,2-naphthoquinones on human tumor cell growth and lack of cross-resistance with other anticancer agents. 966 May 42

We have examined the effects that dexamethasone (DEX), alone or in combination with doxorubicin (DOX), cisplatin (CDDP), or etoposide (VP-16), exerts on the growth of the androgen-independent prostate cancer PC-3 cells. DEX exhibited only a limited cytotoxicity (growth inhibition of about 28% or 20% after 24 or 72 h of exposure, respectively, in the range of DEX 10-100 nM) and did not induce apoptosis in the cells. This cytotoxicity of DEX was mimicked by an active peptide (peptide Ac2-26) drawn from the human lipocortin 1 N-terminus region and abrogated by an antibody to human lipocortin 1. Two inhibitors of arachidonic acid metabolism, tenidap and indomethacin, also caused cytotoxicity. The cytotoxic effects of DEX in combination with DOX, CDDP, or VP-16 were antagonistic when the steroid was administered 3 h before or simultaneously with the drugs. Other schedule-dependency experiments further clarified that, at least in the case of the combination with DOX, it is the steroid that desensitizes the cells to the drug. When peptide Ac2-26, tenidap, or indomethacin were tested in combination with DOX, antagonism was also observed. DEX treatment neither modified the ability of the cells to accumulate DOX nor changed their weak expression of P-glycoprotein. PC-3 cells also produce IL-6, which autocrinally stimulates their growth, and whose gene expression may be reduced by glucocorticoids. In the present experiments DEX only slightly decreased the production and secretion of IL-6 by the cells. The present findings suggest that the slight cytotoxic activity and the drug resistance effects of DEX on PC-3 cells are mediated by induction of lipocortin 1 and inhibition of arachidonic acid metabolism, with no relationship to downregulation of IL-6 levels. These findings indicate also that the combination of DEX with conventional chemotherapeutic agents may result in antagonistic antitumor effects.
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PMID:Dexamethasone-induced cytotoxic activity and drug resistance effects in androgen-independent prostate tumor PC-3 cells are mediated by lipocortin 1. 980 59

Phenylbutyrate (PB), a novel lead compound for prostate cancer therapy, has molecular activities distinct from its metabolite, phenylacetate (PA). Both PB and PA promote differentiation in human prostate cancer cell lines, yet little data exist comparing the cytotoxic effects of each drug. We found that PB is more potent than PA in vitro; PB is 1.5-2.5 times more active at inhibiting growth and inducing programmed cell death than PA at clinically achievable doses against each human prostate cancer line studied. PB is equipotent to sodium butyrate, which induces apoptosis and differentiation through multiple mechanisms. Exposure of prostate cancer cell lines to PB reduces their DNA synthesis, leads to fragmentation of genomic DNA, and causes 50-60% of cells to undergo apoptosis. These PB-induced effects are 2-10 times greater than those of the control or PA. The stereotypical changes of apoptosis can be seen with sodium butyrate at similar concentrations, but not with PA. Prostate cancer cell lines overexpressing P-glycoprotein or possessing heterogeneous molecular alterations, including p53 mutations, are also sensitive to the effects of PB. In vivo, Copenhagen rats treated with oral PB had delayed growth of the androgen refractory Dunning R-3327 MAT-LyLu prostate cancer subline by 30-45% in a dose-dependent manner. These results demonstrate that PB induces cytotoxicity via apoptosis in human prostate cancer, in addition to its differentiating properties.
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PMID:Phenylbutyrate induces apoptosis in human prostate cancer and is more potent than phenylacetate. 981 81

The aim of this study was to obtain insight into the role of the multidrug resistance (MDR) phenomenon in hormone-independent progressive prostate cancer. Using immunocytochemistry and Western blotting we determined the expression of P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP), glutathione-S-transferase-pi (GST-pi), Bcl-2, Bax, topoisomerase (Topo) I, II alpha and II beta in the human prostate cancer cell lines PC3, TSU-Pr1, DU145 and LNCaP derivatives LNCaP-R, LNCaP-LNO and LNCaP-FGC. Proliferative activity was assessed by immunocytochemistry. MTT assays were used to determine the sensitivity to etoposide, doxorubicin and vinblastin. Pgp was not expressed in any of the cell lines. MRP was variably expressed. GST-pi was expressed in TSU-Pr1, PC3 and DU145. The expression of Bcl-2 was restricted to TSU-Pr1, whereas Bax was found in all cell lines. Topo II alpha was expressed at the highest level in the rapidly proliferating cell lines TSU-Pr1 and DU145. Topo I and II beta were equally expressed. Resistance profiles varied among the cell lines, with TSU-Pr1 being the most sensitive and LNCaP-LNO relatively resistant. Multiple MDR proteins were expressed in prostate cancer cell lines and may well influence response to chemotherapy. Future functional studies, using chemo-selected MDR models, may further help to determine the mechanism or combination of mechanisms underlying the resistance of prostate cancer to chemotherapy.
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PMID:Chemosensitivity of prostate cancer cell lines and expression of multidrug resistance-related proteins. 1049 44

Cooked-food mutagens formed when frying meat have been suggested to contribute to the etiology of colon, breast and prostate cancer. The most prevalent of these mutagens is 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which after absorption is bioactivated by both phase I and phase II enzymes. Although available data suggest absorption of PhIP in humans, the extent and mechanism of absorption are unknown. In the present study we examined the transport of [(3)H]PhIP through the human Caco-2 intestinal epithelial cell monolayer, a well-accepted model of human intestinal absorption. The influx, or absorption, was extensive and linear for 2 h and up to a PhIP concentration of 5 microM. Still, the basolateral to apical efflux [apparent permeability coefficient (P(app)) 54.2 +/- 0.7x10(-6) cm/s, mean +/- SEM, n = 24] was 3.6 times greater than the apical to basolateral influx (P(app) 15.1 +/- 0.6x10(-6) cm/s, n = 21, P < 0.0001). Equilibrium exchange experiments demonstrated the efflux to be a true active process. Preincubations with verapamil, an inhibitor of P-glycoprotein-mediated transport, or MK-571, an inhibitor of multidrug resistance-associated protein-mediated transport, stimulated influx and reduced efflux of PhIP, suggesting that PhIP is a substrate for both of these transporters. These findings should be considered when determining exposure to the cooked food mutagens.
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PMID:Transport of the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) across the human intestinal Caco-2 cell monolayer: role of efflux pumps. 1054 19


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