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![Tamoxifen and metabolite concentrations in serum over a 10-day sampling period after a single oral dose of 90.23 mg [ 14 C] tamoxifen. HPLC analysis was performed after deconjugation with beta-glucuronidase.](profile/Ernst-Lien/publication/7435753/figure/fig3/AS:601642277806082@1520454105144/Tamoxifen-and-metabolite-concentrations-in-serum-over-a-10-day-sampling-period-after-a.png)
Tamoxifen and metabolite concentrations in serum over a 10-day sampling period after a single oral dose of 90.23 mg [ 14 C] tamoxifen. HPLC analysis was performed after deconjugation with beta-glucuronidase.
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The selective oestrogen-receptor modulator tamoxifen is the most commonly used drug against breast cancer. It has potent metabolites, such as 4-hydroxytamoxifen. Recently, the metabolite 4-hydroxy-N-desmethyltamoxifen has received increased attention as it may be a major contributor to the overall effects of tamoxifen. The excretion of tamoxifen an...
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Context 1
... tamoxifen and N-desmethyltamoxifen (NDtam) levels were observed in the serum (Figure 3). The occurrence of a peak concentration of tamoxifen in the serum within 1 hour of administration suggests a good and fast absorption of the drug. After an initial rapid increase, NDtam increased slowly during the observation period. Based on the serum concentrations measured, the absorption half-life of tamoxifen was calculated as 5 hours. In serum, the hydroxylated metabolites 4OHtam and 4OHNDtam were below the detection limit of 1 ng/ml of the HPLC assay during the study period (Figure 3), suggesting that once formed, these metabolites are rapidly conjugated and eliminated in the bile and urine, resulting in undetectable serum levels ...
Context 2
... tamoxifen and N-desmethyltamoxifen (NDtam) levels were observed in the serum (Figure 3). The occurrence of a peak concentration of tamoxifen in the serum within 1 hour of administration suggests a good and fast absorption of the drug. After an initial rapid increase, NDtam increased slowly during the observation period. Based on the serum concentrations measured, the absorption half-life of tamoxifen was calculated as 5 hours. In serum, the hydroxylated metabolites 4OHtam and 4OHNDtam were below the detection limit of 1 ng/ml of the HPLC assay during the study period (Figure 3), suggesting that once formed, these metabolites are rapidly conjugated and eliminated in the bile and urine, resulting in undetectable serum levels ...
Citations
... The primary urinary metabolites for identifying stanozolol administration are 3-OH-stanozolol and 16β-OH-stanozolol (Delcourt et al. 2021;Schänzer et al. 1990). Tamoxifen is biotransformed to a large extent into 4-OH-tamoxifen and 4-OH-N-desmethyltamoxifen (Kisanga et al. 2005;Mihailescu et al. 2000), clomifene is converted to 4-OHclomifene (Euler et al. 2022), and GW1516 is metabolised to GW1516-sulfoxide and GW1516-sulfone (Thevis et al. 2010). ...
Hair analysis is a crucial method in forensic toxicology with potential applications in revealing doping histories in sports. Despite its widespread use, knowledge about detectable substances in hair is limited. This study systematically assessed the detectability of prohibited substances in sports using a multifaceted approach. Initially, an animal model received a subset of 17 model drugs to compare dose dependencies and detection windows across different matrices. Subsequently, hair incorporation data from the animal experiment were extrapolated to all substances on the World Anti-Doping Agency’s List through in-silico prediction. The detectability of substances in hair was further validated in a proof-of-concept human study involving the consumption of diuretics and masking agents. Semi-quantitative analysis of substances in specimens was performed using ultra-performance liquid chromatography–tandem mass spectrometry. Results showed plasma had optimal dose dependencies with limited detection windows, while urine, faeces, and hair exhibited a reasonable relationship with the administered dose. Notably, hair displayed the highest detection probability (14 out of 17) for compounds, including anabolic agents, hormones, and diuretics, with beta-2 agonists undetected. Diuretics such as furosemide, canrenone, and hydrochlorothiazide showed the highest hair incorporation. Authentic human hair confirmed diuretic detectability, and their use duration was determined via segmental analysis. Noteworthy is the first-time reporting of canrenone in human hair. Anabolic agents were expected in hair, whereas undetectable compounds, such as peptide hormones and beta-2 agonists, were likely due to large molecular mass or high polarity. This study enhances understanding of hair analysis in doping investigations, providing insights into substance detectability.
... For example, metabolites of energy-generating metabolic pathways, such as glycolysis, TCA cycle, and beta-oxidation are present at higher levels in non-hormone-dependent breast cancer and triple-negative breast cancer than in hormone-dependent breast cancer, which correlates with breast cancer aggressiveness [13]. Metabolites of secondary bile acid metabolism, amino acid degradation, short-chain fatty acid production, and deconjugated hormones have also been shown to predict cancer aggressiveness [14][15][16]. ...
Purpose:
Identification of metabolomic biomarkers of high SBR grade in non-metastatic breast cancer.
Methods:
This retrospective bicentric metabolomic analysis included a training set (n = 51) and a validation set (n = 49) of breast cancer tumors, all classified as high-grade (grade III) or low-grade (grade I-II). Metabolomes of tissue samples were studied by liquid chromatography coupled with mass spectrometry.
Results:
A molecular signature of the top 12 metabolites was identified from a database of 602 frequently predicted metabolites. Partial least squares discriminant analyses showed that accuracies were 0.81 and 0.82, the R2 scores were 0.57 and 0.55, and the Q2 scores were 0.44431 and 0.40147 for the training set and validation set, respectively; areas under the curve for the Receiver Operating Characteristic Curve were 0.882 and 0.886. The most relevant metabolite was diacetylspermine. Metabolite set enrichment analyses and metabolic pathway analyses highlighted the tryptophan metabolism pathway, but the concentration of individual metabolites varied between tumor samples.
Conclusions:
This study indicates that high-grade invasive tumors are related to diacetylspermine and tryptophan metabolism, both involved in the inhibition of the immune response. Targeting these pathways could restore anti-tumor immunity and have a synergistic effect with immunotherapy. Recent studies could not demonstrate the effectiveness of this strategy, but the use of theragnostic metabolomic signatures should allow better selection of patients.
... Hence, metabolomics study is important in categorizing breast cancer into different types and stages, as it uses accurate methods and requires less time for analysis. Metabolites from secondary bile acid metabolism, amino acid degradation, short-chain fatty acid production, and deconjugated hormones can be measured to predict tamoxifen resistance, hormone-induced apoptosis, cancer aggressiveness, and histone deacetylase (HDAC) inhibition [55][56][57]. ...
Breast cancer is the most commonly diagnosed cancer in women worldwide. Major advances have been made towards breast cancer prevention and treatment. Unfortunately, the incidence of breast cancer is still increasing globally. Metabolomics is the field of science which studies all the metabolites in a cell, tissue, system, or organism. Metabolomics can provide information on dynamic changes occurring during cancer development and progression. The metabolites identified using cutting-edge metabolomics techniques will result in the identification of biomarkers for the early detection, diagnosis, and treatment of cancers. This review briefly introduces the metabolic changes in cancer with particular focus on breast cancer.
... TAM requires hepatic activation by polymorphic cytochrome CYP2D6 and CY3A4 to form the 4-hydroxytamoxifen and 4-hydroxy-N-desmethyltamoxifen (endoxifen). These products have a higher affinity to ER than TAM and thus, a higher ability to inhibit cell proliferation in ER-positive cells [4][5][6][7]. On the other hand, 5%-10% of ER-negative breast cancers displayed anti-tumor activity, suggesting another signaling pathway independent of ER [8]. However, TAM exhibits several dose-dependent drawbacks during clinical administration that lead to blood clotting disorders, vision impairment (retinopathy) and corneal opacities [9]. ...
Tamoxifen (TAM) is a hormonal drug and is mainly used as an anti-estrogen in breast cancer patients. TAM binds to estrogen receptors (ERs), resulting in inhibition of estrogen signaling pathways and thus, a downregulation of cell proliferation. Cancer cells with negative or low ER expression will not uptake TAM and will show low response. Poly (methyl methacrylate) (PMMA) nanoparticles were prepared using surfactant-free emulsion polymerization, then were loaded with Nile red (NR), which resulted in PMMA-NR. To enhance TAM delivery to cervical cancer cells (HELA), which is considered ER-negative, we loaded TAM and polymethyl methacrylate nanoparticles-Nile-red into silica (PMMA-NR-Si-TAM). The uptake and intracellular distribution were visualized by confocal laser scanning microscopy, and the in vitro cytotoxic activity was evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay using HELA and non-tumorigenic cell line HFF-1. The sensitivity of HELA (LC50: 207.31 µg/mL) and HFF-1 (LC50: 234.08 µg/mL) to free TAM was very low. However, after the encapsulation of TAM with PMMA-NR, the sensitivity significantly increased HELA (LC50: 71.83 µg/mL) and HFF-1 (LC50: 37.36 µg/mL). This indicates that TAM can be used for the treatment of ER-negative cervical cancer once conjugated to PMMA-NR nanoparticles. In addition, the PMMA-NR formulation appears to be highly suitable for cancer imaging and drug delivery.
... Despite the fact endoxifen is an effective treatment for breast cancer, it presents possible consequences on the environment (Environment Canada, 2015). Endoxifen is not completely metabolized in human body and is actively excreted (Kisanga et al., 2005). As a result, endoxifen is potentially released to the water environment via wastewater treatment plants (WWTPs) (Negreira et al., 2014). ...
Endoxifen is an effective metabolite of a common chemotherapy agent, tamoxifen. Endoxifen, which is toxic to aquatic animals, has been detected in wastewater treatment plant (WWTP) effluent. This research investigates ultraviolet (UV) radiation (253.7 nm) application to degrade (E)- and (Z)-endoxifen in water and wastewater and phototransformation by-products (PBPs) and their toxicity. The effects of light intensity, pH and initial concentrations of (E)- and (Z)-endoxifen on the photodegradation rate were examined. Endoxifen in water was eliminated ≥99.1% after 35 s of irradiation (light dose of 598.5 mJ cm-2). Light intensity and initial concentrations of (E)- and (Z)-endoxifen exhibited positive trends with the photodegradation rates while pH had no effect. Photodegradation of (E)- and (Z)-endoxifen in water resulted in three PBPs. Toxicity assessments through modeling of the identified PBPs suggest higher toxicity than the parent compounds. Photodegradation of (E)- and (Z)-endoxifen in wastewater at light doses used for disinfection in WWTPs (16, 30 and 97 mJ cm-2) resulted in reductions of (E)- and (Z)-endoxifen from 30 to 71%. Two of the three PBPs observed in the experiments with water were detected in the wastewater experiments. Therefore, toxic compounds are potentially generated at WWTPs by UV disinfection if (E)- and (Z)-endoxifen are present in treated wastewater.
... Its antitumor ability derives from the antagonism towards the proliferative action of estrogen through competitive binding to ERs (Goldstein et al., 2000). As a prodrug, TAM requires a complex metabolic activation to elicit its designed pharmacological activity (Kisanga et al., 2005). The 4-hydroxytamoxifen and 4-hydroxy-N-desmethyltamoxifen (endoxifen) are the main products of hepatic oxidation, elicited by CYP2D6 and CY3A4, with high anti-estrogen potential in humans (Murdter et al., 2012;Johnson et al., 2008) (Fig. 1). ...
Tamoxifen (TAM) is a first generation-SERM administered for hormone receptor-positive (HER+) breast cancer in both pre-and post-menopausal patients and may undergo metabolic activation in organisms that share similar receptors and thus face comparable mechanisms of response. The present study aimed to assess whether environmental trace concentrations of TAM are bioavailable to the filter feeder M. galloprovincialis (100 ng L −1) and to the deposit feeder N. diversicolor (0.5, 10, 25 and 100 ng L −1) after 14 days of exposure. Behavioural impairment (burrowing kinetic), neurotoxicity (AChE activity), endocrine disruption by alkali-labile phosphate (ALP) content, oxidative stress (SOD, CAT, GPXs activities), biotransformation (GST activity), oxidative damage (LPO) and genotoxicity (DNA damage) were assessed. Moreover, this study also pertained to compare TAM cytotoxicity effects to mussels and targeted human (i.e. immortalized retinal pigment epithelium-RPE; and human transformed endothelial cells-HeLa) cell lines, in a range of concentrations from 0.5 ng L −1 to 50 μg L −1. In polychaetes N. diversicolor, TAM exerted remarkable oxidative stress and damage at the lowest concentration (0.5 ng L −1), whereas significant genotoxicity was reported at the highest exposure level (100 ng L −1). In mussels M. galloprovincialis, 100 ng L −1 TAM caused endocrine disruption in males, neuro-toxicity, and an induction in GST activity and LPO byproducts in gills, corroborating in genotoxicity over the exposure days. Although cytotoxicity assays conducted with mussel haemocytes following in vivo exposure was not effective, in vitro exposure showed to be a feasible alternative, with comparable sensitivity to human cell line (HeLa).
... In the liver, estrogens are conjugated through glucuronidation or sulfation before being excreted back into the intestine 18 . In the intestine, conjugated estrogens are deconjugated by the gut microbiome and are partially reabsorbed 19,20 . The deconjugation process, owing at least partially to the microbial β-glucuronidase (GUS) enzymatic activity, influences the half-life and efficacy of ERT drugs 21 . ...
Conjugated estrogens (CE) and Bazedoxifene (BZA) combination is used to alleviate menopause-associated symptoms in women. CE+BZA undergo first-pass-metabolism in the liver and deconjugation by gut microbiome via β-glucuronidase (GUS) enzyme inside the distal gut. To date, the impact of long-term exposure to CE+BZA on the gut microbiome or GUS activity has not been examined. Our study using an ovariectomized mouse model showed that CE+BZA administration did not affect the overall cecal or fecal microbiome community except that it decreased the abundance of Akkermansia, which was identified as a fecal biomarker correlated with weight gain. The fecal GUS activity was reduced significantly and was positively correlated with the abundance of Lactobacillaceae in the fecal microbiome. We further confirmed in Escherichia coli K12 and Lactobacillus gasseri ADH that Tamoxifen-, 4-hydroxy-Tamoxifen- and Estradiol-Glucuronides competed for GUS activity. Our study for the first time demonstrated that long-term estrogen supplementation directly modulated gut microbial GUS activity. Our findings implicate that long-term estrogen supplementation impacts composition of gut microbiota and microbial activity, which affects estrogen metabolism in the gut. Thus, it is possible to manipulate such activity to improve the efficacy and safety of long-term administered estrogens for postmenopausal women or breast cancer patients.
... Experimental group allocation was randomized per cage while ensuring that in each cage there was a mix of all groups to minimise possible inter-cage interactions, with the exception of vehicle-dosed vegfr2 fl/fl Tie2CreER T2 mice: tamoxifen used for Tie2CreER T2 induction (see below) and its active metabolites are present in urine (Kisanga et al., 2005). This excretion could lead to crosscontamination between vehicle-and tamoxifen-dosed animals in the same cage so these mice were housed separately. ...
Chronic pain can develop in response to conditions such as inflammatory arthritis. The central mechanisms underlying the development and maintenance of chronic pain in humans are not well elucidated although there is evidence for a role of microglia and astrocytes. However in pre-clinical models of pain, including models of inflammatory arthritis, there is a wealth of evidence indicating roles for pathological glial reactivity within the CNS. In the spinal dorsal horn of rats with painful inflammatory arthritis we found both a significant increase in CD11b+ microglia-like cells and GFAP+ astrocytes associated with blood vessels, and the number of activated blood vessels expressing the adhesion molecule ICAM-1, indicating potential glio-vascular activation. Using pharmacological interventions targeting VEGFR2 in arthritic rats, to inhibit endothelial cell activation, the number of dorsal horn ICAM-1+ blood vessels, CD11b+ microglia and the development of secondary mechanical allodynia, an indicator of central sensitization, were all prevented. Targeting endothelial VEGFR2 by inducible Tie2-specific VEGFR2 knock-out also prevented secondary allodynia in mice and glio-vascular activation in the dorsal horn in response to inflammatory arthritis. Inhibition of VEGFR2 in vitro significantly blocked ICAM-1-dependent monocyte adhesion to brain microvascular endothelial cells, when stimulated with inflammatory mediators TNF-α and VEGF-A165a. Taken together our findings suggest that a novel VEGFR2-mediated spinal cord glio-vascular mechanism may promote peripheral CD11b+ circulating cell transmigration into the CNS parenchyma and contribute to the development of chronic pain in inflammatory arthritis. We hypothesise that preventing this glio-vascular activation and circulating cell translocation into the spinal cord could be a new therapeutic strategy for pain caused by rheumatoid arthritis.
... Experimental group allocation was randomized per cage while ensuring that in each cage there was a mix of all groups to minimise possible inter-cage interactions, with the exception of vehicle-dosed vegfr2 fl/fl Tie2CreER T2 mice: tamoxifen used for Tie2CreER T2 induction (see below) and its active metabolites are present in urine (Kisanga et al., 2005). This excretion could lead to crosscontamination between vehicle-and tamoxifen-dosed animals in the same cage so these mice were housed separately. ...
Chronic pain can develop in response to conditions such as inflammatory arthritis. The central mechanisms underlying the development and maintenance of chronic pain in humans are not well elucidated although there is evidence for a role of microglia and astrocytes. However in pre-clinical models of pain, including models of inflammatory arthritis, there is a wealth of evidence indicating roles for pathological glial reactivity within the CNS. In the spinal dorsal horn of rats with painful inflammatory arthritis we found both a significant increase in CD11b+microglia-like cells and GFAP+astrocytes associated with blood vessels, and the number of activated blood vessels expressing the adhesion molecule ICAM-1, indicating potential glio-vascular activation. Using pharmacological interventions targeting VEGFR2 in arthritic rats, to inhibit endothelial cell activation, the number of dorsal horn ICAM-1+blood vessels, CD11b+microglia and the development of secondary mechanical allodynia, an indicator of central sensitization, were all prevented. Targeting endothelial VEGFR2 by inducible Tie2-specific VEGFR2 knock-out also prevented secondary allodynia in mice and glio-vascular activation in the dorsal horn in response to inflammatory arthritis. Inhibition of VEGFR2 in vitro significantly blocked ICAM-1-dependent monocyte adhesion to brain microvascular endothelial cells, when stimulated with inflammatory mediators TNF-α and VEGF-A165a. Taken together our findings suggest that a novel VEGFR2-mediated spinal cord glio-vascular mechanism may promote peripheral CD11b+circulating cell transmigration into the CNS parenchyma and contribute to the development of chronic pain in inflammatory arthritis. We hypothesise that preventing this glio-vascular activation and circulating cell translocation into the spinal cord could be a new therapeutic strategy for pain caused by rheumatoid arthritis.
... This suggests that the routes of elimination for NDT and endoxifen may be different, and is in agreement with data from the hPXR/hCAR/h3A4/3A7/2D6 model (Chang et al., 2016). Indeed, 4-OH metabolites of tamoxifen, including endoxifen, are known to be glucuronidated and sulphated (Poon et al., 1993;Kisanga et al., 2005). It would therefore be informative to determine, in future experiments, whether the profiles of these and other circulating and excreted conjugates are altered with paroxetine co-administration. ...
Tamoxifen is an oestrogen-receptor (ER) antagonist used in the treatment of breast cancer. It is a pro-drug, converted by several P450 enzymes to a primary metabolite, N-desmethyltamoxifen (NDT), which is then further modified by CYP2D6 to a pharmacologically potent secondary metabolite, 4-hydroxy-N-desmethyltamoxifen (endoxifen). Anti-depressants (ADs), which are often co-prescribed to patients receiving tamoxifen, are also metabolised by CYP2D6 and evidence suggests that a drug-drug interaction (DDI) between these agents adversely affects the outcome of tamoxifen therapy by inhibiting endoxifen formation. Here, we have evaluated this potentially important DDI in vivo, in mice humanised for CYP2D6 (hCYP2D6). The rate of conversion of NDT to endoxifen by hCYP2D6 mouse liver microsomes (MLM) in vitro was similar to that of the most active members of a panel of 13 individual human liver microsomes (HLM). Co-incubation with the CYP2D6 inhibitor, quinidine, ablated endoxifen generation by hCYP2D6 MLM. The NDT-hydroxylation activity of wild-type MLM was 7.4 times higher than that of hCYP2D6, while MLM from Cyp2d knockout animals were inactive. Hydroxylation of NDT correlated with that of bufuralol, a CYP2D6 probe substrate, in the HLM panel. In vitro, ADs of the selective serotonin reuptake inhibitor (SSRI) class were, by an order of magnitude, more potent inhibitors of NDT hydroxylation by hCYP2D6 MLM than were compounds of the tricyclic class. At a clinically-relevant dose, paroxetine pre-treatment inhibited the generation of endoxifen from NDT in hCYP2D6 mice in vivo. These data demonstrate the potential of ADs to affect endoxifen generation and, thereby, the outcome of tamoxifen therapy.
