Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of Toremifene on cell growth in vitro was tested on the R3230AC rat mammary adenocarcinoma as model. Toremifene differed from Tamoxifen in that it did not induce resistance; some cross-resistance was observed in Tamoxifen tolerant tumour cell lines. Toremifene does not influence P-glycoprotein expression in this model and at the levels studied.
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PMID:Toremifene resistance in a rat mammary tumour model. 135 32

The ability of the anti-oestrogens tamoxifen, toremifene and their 4-hydroxy and N-desmethyl metabolites to modify doxorubicin (dox) toxicity to intrinsically resistant and multidrug resistant cell lines was compared, using human breast and lung cancer, and Chinese hamster ovary cell lines. The anti-oestrogens significantly enhanced dox toxicity to multidrug resistant, P-glycoprotein-positive cell lines, but did not affect toxicity to intrinsically resistant, P-glycoprotein-negative cells. Modification was observed at clinically achievable anti-oestrogen concentrations. Toremifene and tamoxifen would therefore appear to be good candidates for in vivo studies as MDR modulating agents in selected patients with P-glycoprotein-positive tumours.
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PMID:Differential modulation of doxorubicin toxicity to multidrug and intrinsically drug resistant cell lines by anti-oestrogens and their major metabolites. 768 15

Toremifene exerts multiple and varied effects on the gene expression of human peripheral mononuclear cells. After short-term, in vitro exposure to therapeutical levels, distinct changes in P-glycoprotein, steroid receptors, p53 and Bcl-2 expression take place. In view of the increasing use of antiestrogens in cancer therapy and prevention, there is obvious merit in long-term in vivo studies to be conducted.
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PMID:The effect of Toremifene on the expression of some genes in human mononuclear cells. 856 86

Toremifene, apart from its partial estrogen antagonism, exerts multiple and varied effects on a variety of genes involved in the control of signalling and apoptosis. After three weeks of exposure of R3230AC hosting rats to therapeutical oral doses of toremifene distinct changes in steroid receptors, P-glycoprotein, p53 and Bc1-2 expression and protein S100 levels occurred, which may contribute to our understanding of the mechanisms of action of this antiestrogen.
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PMID:The effect of toremifene on the expression of genes in a rat mammary adenocarcinoma. 889 31

Toremifene (TOR) is a new antiestrogenic agent, a triphenylethylene derivative that was developed as an alternative to tamoxifene (TAM). TOR has been observed to be more effective than TAM with milder toxicity at high doses. We examined the in vitro combination-effect of TOR with cyclophosphamide, adriamycin, 5-fluorouracil and three drug mixture (CAF) on the growth of various human mammary carcinomas. The combination shows a semi-additive or additive growth inhibitory effect on all estrogen positive cells used here except one cell line. In particular, the additive or synergic combination-effect was observed on TAM resistant cells. Furthermore, TOR exhibits a chemosensitizing activity in ADR-resistant cells by expressing P-glycoprotein coded by MDR-1 (multidrug resistance gene). The chemosensitizing activity is dose-dependent of TOR. As described above, the combination of TOR with CAF shows more than a semi-additive effect in this experiment. In conclusion, the addition of high-dose TOR to CAF therapy might be useful for advanced/recurrent breast cancer.
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PMID:[The in vitro combination-effect of toremifene with CAF (cyclophosphamide, adriamycin, 5-fluorouracil) on growth of various human mammary carcinomas]. 972 52

The effect of toremifene on P-glycoprotein-mediated multidrug resistance (MDR) in breast and head and neck cancer cell lines was measured in vitro and in vivo. Pgp expression was low and high, respectively, in drug-sensitive (MCF7-S, KB) and drug-resistant (MCF7-R, MCF7-R1, KBV1) cell lines. Toremifene (7.5 microM) significantly enhanced cytoplasmic and nuclear accumulation of doxorubicin in drug-resistant cells. Toremifene (10 microM) increased the in vitro cytotoxicity of doxorubicin in drug-resistant breast cancer cells (13-fold and 21-fold for MCF7-R and MCF7-R1, respectively) without affecting the sensitivity of MCF7-S cells. Similarly, toremifene (10 microM) caused a 12-fold increase in the sensitivity of KBV1 cells to vinblastine. In contrast, toremifene (5 microM) reduced the net uptake of the radiolabelled Pgp substrate, Tc-99m-sestamibi, in the Pgp-overexpressing cell lines by factors of 0.32 and 0.42 for MCF7-R1 and KBV1 cells, respectively (p < 0.01), and, to a lesser extent, by corresponding factors of 0.89 and 0.86 in the drug-sensitive cell lines (p < 0.05 and p > 0.05, respectively). In nude mice bearing both KB and KBV1 xenograft tumours, significantly higher tumour levels of Tc-99m-sestamibi were recorded in KB tumours compared with KBV1 tumours. After 3 days of treatment with intraperitoneal toremifene (25 mg/kg), tumour levels of Tc-99m-sestamibi were reduced in KB and KBV1 tumours but only statistically significantly for KB tumours. Toremifene is a potent MDR modulating agent with respect to chemotherapeutic agents but has the opposite effect with respect to Tc-99m-sestamibi. This finding is of importance in view of the widespread use of Tc-99m-sestamibi as an imaging surrogate for a chemotherapeutic agent.
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PMID:Differential effects of toremifene on doxorubicin, vinblastine and Tc-99m-sestamibi in P-glycoprotein-expressing breast and head and neck cancer cell lines. 1536 48

Recent developments with chemotherapy for breast cancer have improved patient survival. However, there continue to be nonresponders to conventional anticancer agents. Multidrug resistance (MDR) is caused by the expression of P-glycoprotein (P-gp) on the cell membrane. The expression of P-gp is encoded by MDR1 mRNA in tumors and is associated with clinical drug resistance. Since P-gp appears to be involved in both acquired and congenital MDR in human cancers, P-gp could be an important target for improving the efficacy of chemotherapy. Recently, we have focused on a therapeutic approach to reduce drug resistance in chemotherapy for breast cancer. Dofequidar fumarate (Dof) is a novel, orally active quinoline derivative that reverses multidrug resistance. In preclinical studies, the inhibition of doxorubicin-resistant cancer cell lines was observed in the presence of Dof + doxorubicin. We conducted clinical trials including Dof + cyclophosphamide (C), doxorubicin (A), and fluorouracil therapy (F) for patients with advanced or recurrent breast cancer. We compared the efficacy and tolerability of Dof + CAF with CAF alone. In this randomized, placebo-controlled trial, all patients were treated with six cycles of CAF therapy. Patients received Dof (900 mg p.o.) 30 min before doxorubicin. The primary endpoint was overall response rate (partial or complete response). In total, 221 patients were evaluable. The overall response rate was 42.6% for CAF alone versus 53.1% for Dof + CAF. Although the response rate improved by more than 10% with the combination of Dof + CAF, it was not statistically significant. Initially, we were expecting more than 20% improvement in the overall response rate. However, Dof significantly improved progression-free survival in patients who were premenopausal (P=0.046), who had received no prior therapy (P<0.01), or patients with advanced (stage IV) primary tumors (P=0.017). In addition, treatment with Dof did not affect the plasma concentration of doxorubicin in patients. These clinical studies indicate that Dof was well tolerated and displayed promising efficacy in patients who had not received prior therapy. The antiestrogens, tamoxifen, and toremifene, may moderate P-gp-related drug resistance in vitro. Toremifene demonstrated a synergistic effect in combination with paclitaxel on various human breast cancer cell lines. Furthermore, a synergistic effect was observed on a multidrug-resistant cell line. This synergistic effect was more potent when paclitaxel was combined with toremifene than with tamoxifen. Clinical benefits in some patients with recurrent breast cancer were reported.
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PMID:Drug resistance in chemotherapy for breast cancer. 1627 61