Tamoxifen enhances the Hsp90 molecular chaperone ATPase activity.
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PROVIDER: S-EPMC2848575 | BioStudies |
REPOSITORIES: biostudies
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Project description:OBJECTIVE:Platelets, which are mainly known for their role in hemostasis, are now known to play a crucial role in metastasis. Tamoxifen is a selective estrogen receptor modulator that is widely used for the treatment of breast cancer. Tamoxifen and its metabolites have been shown to directly impact platelet function, suggesting that this drug has additional mechanisms of action. The purpose of this study was to determine whether tamoxifen exerts antitumor effects through direct platelet inhibition. APPROACH AND RESULTS:This study found that pretreatment with tamoxifen leads to a significant inhibition of platelet activation. Platelets exposed to tamoxifen released significantly lower amounts of proangiogenic regulator vascular endothelial growth factor. In vitro angiogenesis assays confirmed that tamoxifen pretreatment led to diminished capillary tube formation and decreased endothelial migration. Tamoxifen and its metabolite, 4-hydroxytamoxifen, also significantly inhibited the ability of platelets to promote metastasis in vitro. Using a membrane-based array, we identified several proteins associated with angiogenesis metastasis that were lower in activated releasate from tamoxifen-treated platelets, including angiogenin, chemokine (C-X-C motif) ligand 1, chemokine (C-C motif) ligand 5, epidermal growth factor, chemokine (C-X-C motif) ligand 5, platelet-derived growth factor dimeric isoform BB, whereas antiangiogenic angiopoietin-1 was elevated. Platelets isolated from patients on tamoxifen maintenance therapy were also found to have decreased activation responses, diminished vascular endothelial growth factor release, and lower angiogenic and metastatic potential. CONCLUSIONS:We demonstrate that tamoxifen and its metabolite 4-hydroxytamoxifen directly alter platelet function leading to decreased angiogenic and metastatic potential. Furthermore, this study supports the idea of utilizing targeted platelet therapies to inhibit the platelet's role in angiogenesis and malignancy.
| S-EPMC5364056 | BioStudies
Project description:Tamoxifen, a standard therapy for breast cancer, is metabolized to compounds with anti-estrogenic as well as estrogen-like action at the estrogen receptor. Little is known about the formation of estrogen-like metabolites and their biological impact. Thus, we characterized the estrogen-like metabolites tamoxifen bisphenol and metabolite E for their metabolic pathway and their influence on cytochrome P450 activity and ADME gene expression. The formation of tamoxifen bisphenol and metabolite E was studied in human liver microsomes and Supersomes™. Cellular metabolism and impact on CYP enzymes was analyzed in upcyte® hepatocytes. The influence of 5 µM of tamoxifen, anti-estrogenic and estrogen-like metabolites on CYP activity was measured by HPLC MS/MS and on ADME gene expression using RT-PCR analyses. Metabolite E was formed from tamoxifen by CYP2C19, 3A and 1A2 and from desmethyltamoxifen by CYP2D6, 1A2 and 3A. Tamoxifen bisphenol was mainly formed from (E)- and (Z)-metabolite E by CYP2B6 and CYP2C19, respectively. Regarding phase II metabolism, UGT2B7, 1A8 and 1A3 showed highest activity in glucuronidation of tamoxifen bisphenol and metabolite E. Anti-estrogenic metabolites (Z)-4-hydroxytamoxifen, (Z)-endoxifen and (Z)-norendoxifen inhibited the activity of CYP2C enzymes while tamoxifen bisphenol consistently induced CYPs similar to rifampicin and phenobarbital. On the transcript level, highest induction up to 5.6-fold was observed for CYP3A4 by tamoxifen, (Z)-4-hydroxytamoxifen, tamoxifen bisphenol and (E)-metabolite E. Estrogen-like tamoxifen metabolites are formed in CYP-dependent reactions and are further metabolized by glucuronidation. The induction of CYP activity by tamoxifen bisphenol and the inhibition of CYP2C enzymes by anti-estrogenic metabolites may lead to drug-drug-interactions.
2018-01-01 | S-EPMC5866846 | BioStudies
Project description:Heat shock protein 90 (Hsp90) is a critical molecular chaperone protein that regulates the folding, maturation, and stability of a wide variety of proteins. In recent years, the development of Hsp90-directed inhibitors has grown rapidly, and many of these inhibitors have entered clinical trials. In parallel, the functional dissection of the Hsp90 chaperone machinery has highlighted the activity disruption of Hsp90 co-chaperone as a potential target. With the roles of Hsp90 co-chaperones being elucidated, cell division cycle 37 (Cdc37), a ubiquitous co-chaperone of Hsp90 that directs the selective client proteins into the Hsp90 chaperone cycle, shows great promise. Moreover, the Hsp90-Cdc37-client interaction contributes to the regulation of cellular response and cellular growth and is more essential to tumor tissues than normal tissues. Herein, we discuss the current understanding of the clients of Hsp90-Cdc37, the interaction of Hsp90-Cdc37-client protein, and the therapeutic possibilities of targeting Hsp90-Cdc37-client protein interaction as a strategy to inhibit Hsp90 chaperone machinery to present new insights on alternative ways of inhibiting Hsp90 chaperone machinery.
| S-EPMC5921262 | BioStudies
Project description:Oral tamoxifen used in the prevention and treatment of ductal carcinoma in situ (DCIS) (estrogen-positive) patients has limited acceptance, due to its adverse side effects. The efficacy of tamoxifen is related to its major metabolite, 4-hydroxytamoxifen. Local transdermal therapy of 4-hydroxytamoxifen to the breast might avert the toxicity of oral tamoxifen, while maintaining efficacy. We aim to study the skin irritancy, as well as to evaluate the efficacy of the developed transfersome formulations, with/without emu oil, using a syngeneic mouse model of breast cancer. We also quantified tamoxifen/4-hydroxytamoxifen concentrations in blood plasma and performed histopathology. The skin irritancy test showed that the pure emu oil and transfersome formulations with or without the emu oil did not cause skin irritancy in the animals studied. A sensitive and specific LC-MS/MS method for the quantification of tamoxifen and 4-hydroxytamoxifen was developed and validated. Studies on tumor volume and necrosis (histopathology) using the breast cancer mouse model showed that the 4-OHT transfersomal formulations, with and without emu oil, showed comparable efficacy with that of orally administered tamoxifen. However, the transfersomal formulations, with and without emu oil, resulted in significantly lower (10.24 ± 0.07 and 32.45 ± 0.48 ng/mL, respectively) plasma concentrations of 4-hydroxytamoxifen, compared to the oral tamoxifen (TAMX) group (634.42 ± 7.54 ng/mL). This study demonstrated the potential use of emu oil in a local transdermal formulation for the treatment of breast cancer and its reduced adverse effects.
| S-EPMC7558379 | BioStudies
Project description:Tamoxifen remains the first line therapy for estrogen receptor positive (ER+) breast cancer. However, polymorphisms of the gene encoding P450 2D6 could result in no protein expression or no CYP2D6 enzymatic activity and may significantly reduce the benefit of the hormone therapy. To address this issue, we designed and synthesized three 4-hydroxytamoxifen bioisosteres utilizing a boron-aryl carbon bond that can be oxidized under physiological conditions to yield 4-hydroxytamoxifen. We show that the bioisosteres inhibit the growth of two ER+ breast cancer cell lines, MCF-7 and T47D, with potencies comparable to or greater than that of 4-hydroxytamoxifen. We further demonstrate that after incubation with breast cancer cells, the majority of the bioisosteres has been converted to 4-hydroxytamoxifen. Our study suggests that boron-based 4-hydroxytamoxifen bioisosteres may be an effective therapeutic remedy for intrinsic tamoxifen resistance in breast cancer patients deficient in CYP2D6 metabolism.
| S-EPMC3711775 | BioStudies
Project description:Hsp90 is a molecular chaperone with important roles in regulating the function of several proteins with potential pathogenic activity. Because many of these proteins are involved in cancer and neurodegenerative promoting pathways, Hsp90 has emerged as an attractive therapeutic target in these diseases. Molecules that bind to the N-terminal nucleotide pocket of Hsp90 inhibit its activity, and consequently, disrupt client protein function. A number of these inhibitors from several chemical classes are now known, and some are already in clinical trials. This review focuses on the purine class of Hsp90 inhibitors, their discovery through rational design, and on efforts aimed towards their optimization and development into clinically viable drugs for the treatment of cancer. Their potential towards neurodegenerative diseases will also be touched upon.
| S-EPMC4699796 | BioStudies
Project description:BACKGROUND:Tamoxifen is considered a prodrug of its active metabolite endoxifen, which is dependent on the CYP2D6 and CYP3A enzymes. Tamoxifen pharmacokinetic variability influences endoxifen exposure and, consequently, its clinical outcome. This study investigated the impact of hormonal status on the pharmacokinetics of tamoxifen and its metabolites in TAM-treated breast cancer patients. METHODS:TAM-treated breast cancer patients (n?=?40) previously believed to have CYP3A activity within the normal range based on oral midazolam and phenotyped as CYP2D6 normal metabolizers using oral metoprolol were divided into two groups according to premenopausal (n?=?20; aged 35-50?years) or postmenopausal (n?=?20; aged 60-79?years) status. All patients were treated with 20?mg/day tamoxifen for at least three months. Serial plasma samples were collected within the 24?h dose interval for analysis of unchanged tamoxifen, endoxifen, 4-hydroxytamoxifen and N-desmethyltamoxifen quantified by LC-MS/MS. CYP activities were assessed using midazolam apparent clearance (CYP3A) and the metoprolol/alfa-hydroxymetoprolol plasma metabolic ratio (CYP2D6). CYP3A4, CYP3A5 and CYP2D6 SNPs and copy number variation were investigated using TaqMan assays. RESULTS:Postmenopausal status increased steady-state plasma concentrations (Css) of tamoxifen (116.95 vs 201.23?ng/mL), endoxifen (8.01 vs 18.87?ng/mL), N-desmethyltamoxifen (485.16 vs 843.88?ng/mL) and 4-hydroxytamoxifen (2.67 vs 4.11?ng/mL). The final regression models included hormonal status as the only predictor for Css of tamoxifen [?-coef ± SE, p-value (75.03?±?17.71, p?=?0.0001)] and 4-hydroxytamoxifen (1.7822?±?0.4385, p?=?0.0002), while endoxifen Css included hormonal status (8.578?±?3.402, p?=?0.02) and race (11.945?±?2.836, p?=?0.007). For N-desmethyltamoxifen Css, the final model was correlated with hormonal status (286.259?±?76.766, p?=?0.0007) and weight (-?8.585?±?3.060, p?=?0.008). CONCLUSION:The premenopausal status was associated with decreased endoxifen plasma concentrations by 135% compared to postmenopausal status. Thus, the endoxifen plasma concentrations should be monitored mainly in the premenopausal period to maintain plasma levels above the efficacy threshold value. TRIAL REGISTRATION:RBR-7tqc7k.
| S-EPMC6921430 | BioStudies
Project description:The tamoxifen-inducible Cre-loxP system is widely used to overcome gene targeting pre-adult lethality, to modify a specific cell population at desired time-points, and to visualize and trace cells in fate-mapping studies. In this study we focused on tamoxifen degradation kinetics, because for all genetic fate-mapping studies, the period during which tamoxifen or its metabolites remain active in the CNS, is essential. Additionally, we aimed to define the tamoxifen administration scheme, enabling the maximal recombination rate together with minimal animal mortality. The time window between tamoxifen injection and the beginning of experiments should be large enough to allow complete degradation of tamoxifen and its metabolites. Otherwise, these substances could promote an undesired recombination, leading to data misinterpretation. We defined the optimal time window, allowing the complete degradation of tamoxifen and its metabolites, such as 4-hydroxytamoxifen, <i>N</i>-desmethyltamoxifen, endoxifen and norendoxifen, in the mouse brain after intraperitoneal tamoxifen injection. We determined the biological activity of these substances <i>in vitro</i>, as well as a minimal effective concentration of the most potent metabolite 4-hydroxytamoxifen causing recombination <i>in vivo.</i> For this purpose, we analyzed the recombination rate in double transgenic Cspg4-cre/Esr1/ROSA26Sortm14(CAG-tdTomato) mice, in which tamoxifen administration triggers the expression of red fluorescent protein in NG2-expressing cells, and employed a liquid chromatography, coupled with mass spectrometry, to determine the concentration of studied substances in the brain. We determined the degradation kinetics of these substances, and revealed that this process is influenced by mouse strains, age of animals, and dosage. Our results revealed that tamoxifen and its metabolites were completely degraded within 8 days in young adult C57BL/6J mice, while the age-matched FVB/NJ male mice displayed more effective degradation. Moreover, aged C57BL/6J mice were unable to metabolize all substances within 8 days. The lowering of initial tamoxifen dose leads to a significantly faster degradation of all studied substances. A disruption of the blood-brain barrier caused no concentration changes of any tamoxifen metabolites in the ipsilateral hemisphere. Taken together, we showed that tamoxifen metabolism in mouse brains is age-, strain- and dose-dependent, and these factors should be taken into account in the experimental design.
| S-EPMC5071318 | BioStudies
Project description:Tamoxifen and 4-hydroxytamoxifen protect isolated human low-density lipoproteins (LDLs) against copper-ion-dependent lipid peroxidation: 4-hydroxytamoxifen is more protective than tamoxifen or 17 beta-oestradiol. 4-Hydroxytamoxifen and 17 beta-oestradiol also prevent the increase in the electrophoretic mobility of LDL caused by exposure to copper ions, presumably by protection of the apoprotein B of LDL against oxidative modification. Our observations may help to account for the cardioprotective benefits reported to be associated with tamoxifen therapy and prophylaxis in breast cancer.
1993-01-01 | S-EPMC1134159 | BioStudies
Project description:Hsp90 (heat-shock protein 90) alone can act to prevent protein aggregation and promote refolding in vitro, but in vivo it operates as a part of a multichaperone complex, which includes Hsp70 and cohort proteins. Since the physiological function of Hsp90 is not yet fully understood, the development of specific antagonists might open new lines of investigation on the role of Hsp90. In an effort to discover Hsp90 antagonists, we screened many drugs and found that the anti-allergic drugs DSCG (disodium cromoglycate) and amlexanox target Hsp90. Both drugs were found to bind directly wild-type Hsp90 via the N- and C-terminal domains. Both drugs strongly suppressed the in vitro chaperone activity of native Hsp90 towards citrate synthase at 1.5-3.0 microM. Amlexanox suppressed C-terminal chaperone activity in vitro, but not N-terminal chaperone activity, and inhibited the association of cohort proteins, such as cyclophilin 40 and Hsp-organizing protein, to the C-terminal domain of Hsp90. These data suggest that amlexanox might disrupt the multichaperone complex, including Hsp70 and cohort proteins, both in vitro and in vivo. Although DSCG inhibited the in vitro chaperone activity of the N-terminal domain, the drug had no effect either on the C-terminal chaperone activity or on the association of the cohort proteins with the C-terminus of Hsp90. The physiological significance of these interactions in vivo remains to be investigated further, but undoubtedly must be taken into account when considering the pharmacology of anti-allergic drugs. DSCG and amlexanox may serve as useful tools for evaluating the physiological significance of Hsp90.
2003-01-01 | S-EPMC1223614 | BioStudies