Elimination of Antiestrogenic Effects of Active Tamoxifen Metabolites by Glucuronidation

Yan, Zheng; Sun, Dongxiao; Sharma, Arun; Chen, Gang; Amin, Shantu; Lazarus, Philip

doi:10.1124/dmd.107.016279

Cited by 51 publications

(44 citation statements)

References 32 publications

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“…N-glucuronidation of TAM and 4-OHTAM at the aminoethoxy side chain has been recently reported to be exclusively carried out by UGT1A4, and the resulting N-glucuronides were found to have ER binding affinities similar to those of their parent counterparts, suggesting that these N-glucuronides might contribute to antiestrogenic activity of TAM in vivo (Kaku et al, 2004;Ogura et al, 2006;Sun et al, 2007;Zheng et al, 2007). By contrast, O-glucuronidation of 4-OHTAM and endoxifen at the 4-hydroxy position has been shown to be carried out by multiple UGTs (Nishiyama et al, 2002;Ogura et al, 2006;Sun et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…By contrast, O-glucuronidation of 4-OHTAM and endoxifen at the 4-hydroxy position has been shown to be carried out by multiple UGTs (Nishiyama et al, 2002;Ogura et al, 2006;Sun et al, 2007). This reaction greatly decreases the ER binding affinity of the resultant O-glucuronides and thus represents an inactivation pathway (Ogura et al, 2006;Zheng et al, 2007). Studies using recombinant human UGT isoforms expressed in insect cells have shown O-glucuronidation of both 4-OHTAM isomers by six UGTs (1A1, 1A3, 1A8, 1A9, 2B7, and 2B15), with UGT2B7 and UGT2B15 having the highest activity toward trans-4-OHTAM and cis-4-OHTAM, respectively (Nishiyama et al, 2002;Ogura et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Although evidence exists supporting cis-4-OHTAM as a weak estrogenic compound (Williams et al, 1994), cumulative studies have provided strong evidence that, similar to trans-4-OHTAM, cis-4-OHTAM acts as an estrogen antagonist in normal and cancerous breast cells (Katzenellenbogen et al, 1984(Katzenellenbogen et al, , 1985Malet et al, 2002). A recent study has shown that both trans-and cis-4-OHTAM displayed roughly equipotent antiestrogenic effects on 17b-estradiolinduced progesterone receptor gene expression in MCF7 cells (Zheng et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Tamoxifen (TAM) is orally administered (20 mg daily) and is converted in vivo by cytochrome P450s (primarily CYP2D6 and CYP3A4) into several metabolites, including 4-hydroxytamoxifen (4-OHTAM) and 4-hydroxy-N-desmethyltamoxifen (endoxifen) (Jacolot et al, 1991;Dehal and Kupfer, 1997). Both 4-OHTAM and endoxifen exist as geometrical isomers and have a likely trans-to-cis ratio of 70:30 at physiologic pH (Malet et al, 2002;Zheng et al, 2007). As both trans isomers of 4-OHTAM and endoxifen have similar antiestrogenic activity, which is nearly 100-fold greater than that of TAM, it is believed that TAM elicits its antiestrogenic activity primarily through its active metabolites 4-OHTAM and endoxifen (Jordan et al, 1977;Furr and Jordan, 1984;Katzenellenbogen et al, 1984;Johnson et al, 2004;Lim et al, 2005;Borges et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Induction of UDP-Glucuronosyltransferase 2B15 Gene Expression by the Major Active Metabolites of Tamoxifen, 4-Hydroxytamoxifen and Endoxifen, in Breast Cancer Cells

Chanawong

Meech

et al. 2015

Drug Metab Dispos

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We previously reported upregulation of UGT2B15 by 17b-estradiol in breast cancer MCF7 cells via binding of the estrogen receptor a (ERa) to an estrogen response unit (ERU) in the proximal UGT2B15 promoter. In the present study, we show that this ERa-mediated upregulation was significantly reduced by two ER antagonists (fulvestrant and raloxifene) but was not affected by a third ER antagonist, 4-hydroxytamoxifen (4-OHTAM), a major active tamoxifen (TAM) metabolite. Furthermore, we found that, similar to 17b-estradiol, 4-OHTAM and endoxifen (another major active TAM metabolite) elevated UGT2B15 mRNA levels, and that this stimulation was significantly abrogated by fulvestrant. Further experiments using 4-OHTAM revealed a critical role for ERa in this regulation. Specifically; knockdown of ERa expression by anti-ERa small interfering RNA reduced the 4-OHTAM-mediated induction of UGT2B15 expression; 4-OHTAM activated the wild-type but not the ERU-mutated UGT2B15 promoter; and chromatin immunoprecipitation assays showed increased ERa occupancy at the UGT2B15 ERU in MCF7 cells upon exposure to 4-OHTAM. Together, these data indicate that both 17b-estradiol and the antiestrogen 4-OHTAM upregulate UGT2B15 in MCF7 cells via the same ERa-signaling pathway. This is consistent with previous observations that both 17b-estradiol and TAM upregulate a common set of genes in MCF7 cells via the ER-signaling pathway. As 4-OHTAM is a UGT2B15 substrate, the upregulation of UGT2B15 by 4-OHTAM in target breast cancer cells is likely to enhance local metabolism and inactivation of 4-OHTAM within the tumor. This represents a potential mechanism that may reduce TAM therapeutic efficacy or even contribute to the development of acquired TAM resistance.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Induction of UDP-Glucuronosyltransferase 2B15 Gene Expression by the Major Active Metabolites of Tamoxifen, 4-Hydroxytamoxifen and Endoxifen, in Breast Cancer Cells

Chanawong

Meech

et al. 2015

Drug Metab Dispos

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“…Its five metabolites, 1,[5][6][7][8][9][10] (N-desmethyl tamoxifen (N-DM-T, m/z 358,216), 4-hydroxy tamoxifen (4-OHT), tamoxifen-N-oxide (T-NO) (m/z 388.227), 3,4-dihydroxy tamoxifen (3,4-diOHT), 4-hydroxy tamoxifen N-oxide (4-OHT-NO) (m/z 404.222)) were also detected (Fig. 2).…”

mentioning

confidence: 99%

Direct Drug Metabolism Monitoring in a Live Single Hepatic Cell by Video Mass Spectrometry

Date¹,

Mizuno

Tsuyama

et al. 2012

ANAL. SCI.

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The monitoring of drug metabolism in a hepatic cell, or in a target cell is a very important trace analysis in drug discovery and development. However, these analyses have been mostly performed by liquid chromatography-mass spectrometry (LC-MS), which needs more than thousand cells. Cells were pretreated by sonication or homogeneization by which any information of drug localization within a cell was lost, in most cases.If the drug metabolism and the localization of drug metabolites within a live single cell can be directly observed under a video microscope, the drug discovery and development become speedy and precise. Furthermore, in personalized medicine, 1 a drug can be properly selected by single-cell drug metabolism analysis using only a few cells in biopsied tissues. We developed the live single-cell video mass spectrometry, 2-4 and applied to the analysis of live single-cell drug metabolism using a hepatic model cell, HepG2.HepG2 cells (human hepatocellular carcinoma cells) were cultured in 35 mm dishes at 37 C in 95% air/5% CO2 in Dulbecco's Modified Eagle's Medium with 4500 mg/L glucose, supplemented with 10% fetal bovine serum (FBS). FBS was inactivated by a heating treatment at 56 C for 30 min.Tamoxifen (TAM) was added to cultured HepG2 cells to be 5 mM final concentration, and incubated for 12 h. An organelle (cytoplasm, a vacuole or a nucleus) was sucked into a nanospray tip (HUMANIX) independently, as shown in Fig. 1. Then, 3 mL of a solvent (90% MeOH/8.0% H2O/2.0% formic acid) was added from the back-end of the tip. These samples were directly introduced by nano-electrospray ionization into a LTQ Orbitrap XL (Thermo Fisher Scientific) at a positive ion mode.Each metabolite was identified according to its exact mass m/z value of Δppm <±3.0. Tamoxifen (m/z 372.232) was detected in cytoplasm (Fig. 2).Its five metabolites, 1,[5][6][7][8][9][10] (N-desmethyl tamoxifen (N-DM-T, m/z 358,216), 4-hydroxy tamoxifen (4-OHT), tamoxifen-N-oxide (T-NO) (m/z 388.227), 3,4-dihydroxy tamoxifen (3,4-diOHT), 4-hydroxy tamoxifen N-oxide (4-OHT-NO) (m/z 404.222)) were also detected (Fig. 2). N-DM-T, which is mainly metabolized by CYP3A4, was preferably detected. This result is in accord with the finding that N-DM-T is a major metabolite of TAM, 5 and that CYP3A4 is the most expressed isozyme in P450 subfamilies of the HepG2 cell.11 Weak molecular peaks were also identified by LC-MS/MS with many cells. Besides the peaks of tamoxifen and its metabolites, many peaks were detected at the same time, most of which were found in the control (without tamoxifen). Most of these peaks were hard to identify, however, peak origin was told apart. The peak of m/z 372.186, for example, is solvent peak, and the peak of m/z 372.267 is from cytoplasm.Two metabolites, (4-OHT and T-NO, which have the same mass (m/z 388.227), and two metabolites, 3,4-diOHT and 4-OHT-NO, that have the same mass (m/z 404.222)) were identified using LC-MS/MS methods, however, endoxifen which is known as the most active metabolites, was not detected. Since HepG...

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Principles of Drug Metabolism

Dalvie

Testa

2021

Burger's Medicinal Chemistry and Drug Discovery

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Metabolism is a complex process that involves enzymatic modification of drugs and xenobiotics and is one of the most important determinants of their fate in the body. Although the drug metabolism is considered a process of detoxification, the products of metabolism can play an important role in the pharmacology and toxicology of the parent drug. Studying the metabolism of newly synthesized molecules is a valuable strategy that allows one to identify the underlying problems, such as “soft spots,” or metabolic activation, that affect the systemic exposure of a molecule and safety and efficacy. Early investigative metabolism of new compounds has helped in assessing the bioactivation potential of these candidates and thus, avoid reactive metabolites or put mitigation strategies in place. Metabolism can also lead to pharmacologically active metabolites. These metabolites can have superior pharmacological, pharmacokinetic, and safety profiles compared to their parent drug and can therefore be developed as drugs. This chapter provides an overview of the enzymes involved in the metabolism of xenobiotics and the different metabolic pathways. An attempt has been made to illustrate these principles with pertinent example with a brief review of topics of potential interests to aspiring medicinal chemists namely, the factors that may influence biotransformation or applications to predict the sites of metabolism. While the medicinal chemists are not expected to possess a deep knowledge of the mechanistic aspects, the hope is that the principles outlined in this chapter will assist them in designing a better drug.

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Elimination of Antiestrogenic Effects of Active Tamoxifen Metabolites by Glucuronidation

Cited by 51 publications

References 32 publications

Induction of UDP-Glucuronosyltransferase 2B15 Gene Expression by the Major Active Metabolites of Tamoxifen, 4-Hydroxytamoxifen and Endoxifen, in Breast Cancer Cells

Induction of UDP-Glucuronosyltransferase 2B15 Gene Expression by the Major Active Metabolites of Tamoxifen, 4-Hydroxytamoxifen and Endoxifen, in Breast Cancer Cells

Direct Drug Metabolism Monitoring in a Live Single Hepatic Cell by Video Mass Spectrometry

Principles of Drug Metabolism

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