Tamoxifen

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Tamoxifen
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Executive Summary Information

Compound Tamoxifen
Toxicities Steatosis, cholestasis, epigenetics
Mechanisms Tamoxifen is typically assessed at concentrations in the range 10-30 uM in vitro, where it is a promiscuous ligand with multiple toxicity-related activities. However, the mechanism underlying its major clinical hepatotoxicity, steatosis, remains unclear, since in vitro assays do not identify a mechanism that is consistent with the sub-micromolar Cmax and distinguishes steatosis from cytotoxicity. No essential role for active metabolites in toxicity has been identified, and at the concentrations typically used in cultured hepatocytes, the many activites observed are hallmarks of a promiscuous activity deriving from nonspecific hydrophobic interactions.
Comments This compound was accepted as a standard based on its extensively characterized omics and epigenetics effects. The relation between in vitro results and steatosis or other in vivo hepatotoxicities, however, should be interpreted with caution.
Feedback Contact Gold Compound Working Group (GCWG)
Tamoxifen
Tamoxifen.png
Identifiers
Leadscope Id LS-393
CAS 10540-29-1
DrugBank APRD00123
ChemSpider 2015313
UNII 094ZI81Y45
Pathway DBs
KEGG D08559
Assay DBs
PubChem CID 2733526
ChEMBL 83
Omics DBs
Open TG-Gate 00054
Properties
pKa 8.52
ToxCast Accepted yes
Toxic Effect Steatosis
ToxBank Accepted yes
Target estrogen receptor
Toxicities Cholestasis,Epigenetics,Steatosis


In Vivo Data ? Compound Assessment
Adverse Events ? Recognized adverse effects of tamoxifen therapy on the liver are relatively rare. Hepatic adverse effects: AST increased (5%), serum bilirubin increased (2%), Cholestasis (<1%)

References:

-Harrison's PRINCIPLES OF INTERNAL MEDICINE 17th Edition 2008

However, assymptomatic hepatic steatosis is observed in 36-44% of women receiving typically 20 mg (~1 umol/kg) of tamoxifen daily for as little as 3 months when measured by computerized tomography.

References:

-Nguyen MC, Stewart RB, Banerji MA, Gordon DH, Kral JG. Relationships between tamoxifen use, liver fat and body distribution in women with breast cancer. Int J Obes Relat Metab Disord 2001;25:296-8.
-Yasuhiro Ogawa ,"Tamoxifen-induced fatty liver in patients with breast cancer", Lancet 1998; 351: 725  K.A.Oien et al. "Cirrhosis with steatohepatitis after adjuvant tamoxifen" The Lancet, Volume 353, Issue 9146, Pages 36-37, 2 January 1999
-Mizuki Nishino et al. "Effects of Tamoxifen on Hepatic Fat Content and the Development of Hepatic Steatosis in Patients with Breast Cancer: High Frequency of Involvement and Rapid Reversal After Completion of Tamoxifen Therapy" Am. J. Roentgenol. 180 (1): 129 (2003)
-Coskun U. et al. "Tamoxifen therapy and hepatic steatosis". Neoplasma. 2002;49(1):61-4.

Non-alcoholic steatohepatitis is observed at lower frequency (0.6-2%) and is associated with obesity, younger age, and concomitant features of metabolic syndrome.

References:

-T. Saphner et al. "The Association of Nonalcoholic Steatohepatitis and Tamoxifen in Patients With Breast Cancer", Cancer 2009;115:3189–95.
-Savino Bruno et al. "Incidence and risk factors for non-alcoholic steatohepatitis: prospective study of 5408 women enrolled in Italian tamoxifen chemoprevention trial" BMJ 2005;330:932

Tamoxifen is associated with acute drug-induced cholestasis without hepatitis. The incidence is low (0.1% of reported adverse events). The fact that both steatosis and cholestasis are not commonly associated with hepatitis implies that the mechanisms underlying these effects can be distinguished from mechanisms of cytotoxicity.

References:

-Manmeet S. Padda, Mayra Sanchez, Abbasi J. Akhtar, and James L. Boyer, “Drug-Induced Cholestasis”, Hepatology 2011;53: 1377-1387.
-A M Blackburn, S A Amiel, Mb, Mrcp, R R Millis, R D Rubens, “Tamoxifen and liver damage”, British Medical Journal, 289: 288 (1989).
-“Tamoxifen citrate side effect: Intrahepatic cholestasis”
Toxicity Mechanisms ? Multiple mechanisms of toxicity have been postulated based on studies at high doses or concentrations. Additional IC50 values are provided in a separate section below:

Attempts to elucidate mechanisms of steatosis in vitro and in animal models consistently indicate that tamoxifen does not inhibit fatty acid oxidation directly, and paradoxically, it down-regulates fatty acid synthase levels. The precise mechanism causing lipid accumulation is unclear but has associated with increased synthesis of triglycerides. One driving force for this effect is proposed to be accumulation of intermediates (malonyl-CoA) in the fatty acid synthesis pathway that shunt fatty acids away from degradation.

References:

-O.A. Gudbrandsen etal., "Causes and prevention of tamoxifen-induced accumulation of triacylglycerol in rat liver" The Journal of Lipid Research, 47, 2223-2232. (2006)
-Christopher J. Lelliott et al. "Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steatosis" FASEB J. 19, 1108–1119 (2005)

Consistent with decreased fatty acid synthesis, lipid accumulation in vitro in human hepatocytes is enhanced approximately 10-fold by exogenous fatty acids, consistent with the correlation of steatohepatitis with obesity in the clinic.

References:

-Marta Moya, M. José Gómez-Lechón, José V. Castell, Ramiro Jover. “Enhanced steatosis by nuclear receptor ligands: A study in cultured human hepatocytes and hepatoma cells with a characterized nuclear receptor expression profile”, Chemico-Biological Interactions 184 (2010) 376–387.
-M. Teresa Donatoa, Alicia Martínez-Romero, Nuria Jiménez, Alejandro Negro, Guadalupe Herrera, José V. Castell, José-Enrique O’Connor, M. José Gómez-Lechón, “Cytometric analysis for drug-induced steatosis in HepG2 cells”, Chemico-Biological Interactions 181 (2009) 417–423.

Analysis of serum from patients taking tamoxifen revealed increased leptin levels, which could in turn modulate fatty acid metabolism in the liver. This result raises a cautionary flag that the actual driving force for steatosis may be extra-hepatic. Other paracrine activities of tamoxifen are described in the section on “Therapeutic Target” that follows.

References:

-Nazan Günel e al., "Serum Leptin Levels Are Associated With Tamoxifen-Induced Hepatic Steatosis", Curr Med Res Opin. 2003;19(1):47-50.
-MedScape

Phospholipidosis was observed when tamoxifen was administered to rats for 6 to 14 weeks (100–130 mg/kg). Tissues including liver, lung, lymph node, adrenal gland, pituitary gland, retina, and autonomic ganglia were examined by light and electron microscopy; and prominent lipidosis-like alterations were seen in all tissues inspected. Phospholipidosis was confirmed for HepG2 cells treated with 16 uM tamoxifen in vitro, but its prevalence is species specific in vivo and has not been identified as a major symptom in humans.

References:

-Lullmann, H., and Lullmann-Rauch, R. (1981). “Tamoxifen-induced generalized lipidosis in rats subchronically treated with high doses. Toxicol. Appl. Pharmacol. 61, 138–146.
-Paul Nioi, Brad K. Perry, Er-Jia Wang, Yi-Zhong Gu, and Ronald D. Snyder, “In Vitro Detection of Drug-Induced Phospholipidosis Using Gene Expression and Fluorescent Phospholipid–Based Methodologies”,Toxicological Sciences 99(1), 162–173 (2007).
-US Food and Drug Administration, “The Regulatory Challenges of Drug-induced Phospholipidosis”, ACPS meeting, April 14, 2010.

Tamoxifen affects mitochondrial function, acting as an uncoupling agent and an inhibitor of mitochondrial electron transport chain. Enzymatic assays and spectroscopic studies indicate that tamoxifen inhibits electron transfer in the respiratory chain at the levels of complex III (ubiquinol cytochrome-c reductase) and, to a lesser extent, of complex IV (cytochrome-c oxidase). Other in vitro assays on isolated mitochondria confirm that tamoxifen inhibits electron transport complexes II+III and IV and in addition inhibits complex V. The inhibition of multiple complexes indicates that this inhibition is non-specific. These effects together may contribute to the more rare observation of hepatitis.

References:

-C. Tuquet et al., "Effects of tamoxifen on the electron transport chain of isolated rat liver mitochondria", Cell Biology and Toxicology. 2000; 16: 207-219.
-Sashi Nadanaciva, Autumn Bernal, Robert Aggeler, Roderick Capaldi, Yvonne Will, “Target identification of drug induced mitochondrial toxicity using immunocapture based OXPHOS activity assays”, Toxicol In Vitro. (2007); 21(5):902-11
-Suhel Parvez et al., "Taurine Prevents Tamoxifen-Induced Mitochondrial Oxidative Damage in Mice" Basic & Clinical Pharmacology & Toxicology, 2008,102, 382–387
-I. Larosche et al. "Tamoxifen Inhibits Topoisomerases, Depletes Mitochondrial DNA, and Triggers Steatosis in Mouse Liver" J. Pharmacol. Exp. Ther. (2007) 321, 526–535.
-L. K. Cole et al., "Tamoxifen induces triacylglycerol accumulation in the mouse liver by activation of fatty acid synthesis", Hepatology Vol 52, Issue 4, pages 1258–1265, October 2010
Therapeutic Target ? Tamoxifen is a selective estrogen receptor modulator with tissue-specific activities. A nonsteroidal triphenylethylene derivative that competitively binds to estrogen receptors on tumors and other tissue targets, producing a nuclear complex that decreases DNA synthesis and inhibits estrogen effects; potent antiestrogenic properties which compete with estrogen for binding sites in breast and other tissues; cells accumulate in the G0 and G1 phases; therefore, tamoxifen is cytostatic rather than cytocidal. One suggested mechanism for its antiproliferative action is the induction of the synthesis of the cytokine transforming growth factor-β (TGF-β), which acts as a negative autocrine regulatory molecule.

Immunohistochemical studies have shown that tamoxifen induces the synthesis of TGF-β in the stromal (mesenchymal) compartment of breast cancers, suggesting a paracrine as well as autocrine mechanism of action, independent of an interaction with the estrogen receptor. Some studies show that tamoxifen can lower the circulating levels of insulin-like growth factor I (IGF-I, a potent mitogen for breast cancer cells) in breast cancer patients. Tamoxifen interacts with tissue factors and binds with different estrogen receptors, ER-alpha or ER-beta, producing both antiestrogenic and estrogenic effects. Its estrogenic effects are on cholesterol metabolism, bone density, and endometric cell proliferation.

References:

-Drugbank: http://www.drugbank.ca/drugs/DB00675
-Holland-Frei Cancer Medicine. 6th edition. Kufe DW, Pollock RE, Weichselbaum RR, et al., editors. Hamilton (ON): BC Decker; 2003
-Harrison's PRINCIPLES OF INTERNAL MEDICINE 17th Edition 2008

Human Adverse Events

The following data table has been mined from the Adverse Events Reporting System (AERS) of the US FDA. Significant human liver events. The first column ("# Reports") is the number of reports found for the corresponding adverse event reported in the third column ("Adverse Event"). The second column ("Report:Baseline Ratio") is ratio calculated from the number of reports ("# Reports") divided by a calculated expected statistical baseline number of reports.

# Reports Report:Baseline Ratio Adverse Event
2 17.2791 hepatic cancer metastatic
2 4.277 hepatitis a
3 19.5612 porphyria non-acute

FDA and Label Information

The following link will display all of the currently approved FDA drug products on the market. The web page will contain a table listing all current products by their respective Tradenames and primary active ingredients. The list is navigable by simply clicking on the product of interest, which will in turn list all of the NDA's and ANDA's associated with that product. From here users can click on a specific NDA or ANDA and see documents that have been submitted for the product that the FDA has made available via their website. The types of documents include approval history, letters, reviews and labels.
FDA Approved Products

This next url will perform a search in the FDA's system for all labels for products that contain "Tamoxifen" as an active ingredient.
FDA Label Search

PubMed references

The following resource link will perform a PubMed query for the terms "Tamoxifen" and "liver toxicity".
Tamoxifen Search


The table listed below contains a summarized listing of toxic effect information leveraged from the 6th European Framework Programme project LIINTOP. For a complete listing of the Gold Compound evaluation criteria please see the Gold Compound Evaluation and Comments immediately following the summary table below.

SMILES CCC(=C(C1=CC=CC=C1)C2=CC=C(C=C2)OCCN(C)C)C3=CC=CC=C3
InChI

InChI=1S/C26H29NO/c1-4-25(21-11-7-5-8-12-21)26(22-13-9-6-10-14-22)23-15-17-24(18-16-23)28-20-19-27(2)3/h5-18H,4,19-20H2,1-3H3/b26-25-

InChI-Key

NKANXQFJJICGDU-QPLCGJKRSA-N

Summary Hepatotoxic Effects from the LIINTOP FP6 Program
Hepatocellular necrosis.gif Apoptosis.gif Transporter inhibition.gif Cholestatic.gif Steatotic.gif Phospholipidosis.gif Hepatocyte function.gif Mithochondria impairment.gif Oxidative stress.gif DNA synthesis genotoxicity.gif Covalent binding.gif Idiosyncrasia metabolic.gif Idiosyncrasia immune.gif Bioactivation required.gif LIINTOP severity.gif References
+ + + + 2

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30]

References

  1. ↑ Kasahara, T., Tomita, K., Murano, H., Harada, T., Tsubakimoto, K., Ogihara, T., Ohnishi, S., Kakinuma, C., 2006. Establishment of an in vitro high-throughput screening assay for detecting phospholipidosis-inducing potential. Toxicol. Sci. 90, 133–141.
  2. ↑ Nioi, P., Perry, B.K., Wang, E.J., Gu, Y.Z., Snyder, R.D., 2007. In vitro detection of druginduced phospholipidosis using gene expression and fluorescent phospholipid based methodologies. Toxicol. Sci. 99, 162–173.
  3. ↑ Sawada, H., Takami, K., Asahi, S., 2005. A toxicogenomic approach to drug-induced phospholipidosis: analysis of its induction mechanism and establishment of a novel in vitro screening system. Toxicol. Sci. 83, 282–292.
  4. ↑ Chatman, L.A., Morton, D., Johnson, T.O., Anway, S.D., 2009. A strategy for risk management of drug-induced phospholipidosis. Toxicol. Pathol. 37, 997–1005.
  5. ↑ Halliwell, W.H., 1997. Cationic amphiphilic drug-induced phospholipidosis. Toxicol. Pathol. 25, 53–60.
  6. ↑ Kasahara, T., Tomita, K., Murano, H., Harada, T., Tsubakimoto, K., Ogihara, T., Ohnishi, S., Kakinuma, C., 2006. Establishment of an in vitro high-throughput screening assay for detecting phospholipidosis-inducing potential. Toxicol. Sci. 90, 133–141.
  7. ↑ Nioi, P., Perry, B.K., Wang, E.J., Gu, Y.Z., Snyder, R.D., 2007. In vitro detection of druginduced phospholipidosis using gene expression and fluorescent phospholipid based methodologies. Toxicol. Sci. 99, 162–173.
  8. ↑ Nonoyama, T., Fukuda, R., 2008. Drug-induced phospholipidosis – pathological aspects and its prediction. J. Toxicol. Pathol. 21, 9–34.
  9. ↑ Pappu, A., Hostetler, K.Y., 1984. Effect of cationic amphiphilic drugs on the hydrolysis of acidic and neutral phospholipids by liver lysosomal phospholipase A. Biochem. Pharmacol. 33, 1639–1644.
  10. ↑ Reasor, M.J., Hastings, K.L., Ulrich, R.G., 2006. Drug-induced phospholipidosis: issues and future directions. Expert Opin. Drug Saf. 5, 567–583.
  11. ↑ Reasor, M.J., Kacew, S., 2001. Drug-induced phospholipidosis: are there functional consequences? Exp. Biol. Med. (Maywood) 226, 825–830.
  12. ↑ Sawada, H., Takami, K., Asahi, S., 2005. A toxicogenomic approach to drug-induced phospholipidosis: analysis of its induction mechanism and establishment of a novel in vitro screening system. Toxicol. Sci. 83, 282–292.
  13. ↑ Hynes, J., Marroquin, L.D., Ogurtsov, V.I., Christiansen, K.N., Stevens, G.J., Papkovsky, D.B., Will, Y., 2006. Investigation of drug-induced mitochondrial toxicity using fluorescence-based oxygen-sensitive probes. Toxicol. Sci. 92, 186–200.
  14. ↑ Johannsen, D.L., Ravussin, E., 2009. The role of mitochondria in health and disease. Curr. Opin. Pharmacol. 9, 780–786.
  15. ↑ Jones, D.P., Lemasters, J.J., Han, D., Boelsterli, U.A., Kaplowitz, N., 2010. Mechanisms of pathogenesis in drug hepatotoxicity putting the stress on mitochondria. Mol. Interv. 10, 98–111.
  16. ↑ Labbe, G., Pessayre, D., Fromenty, B., 2008. Drug-induced liver injury through mitochondrial dysfunction: mechanisms and detection during preclinical safety studies. Fundam. Clin. Pharmacol. 22, 335–353.
  17. ↑ Masubuchi, Y., 2006. Metabolic and non-metabolic factors determining troglitazone hepatotoxicity: a review. Drug Metab. Pharmacokinet. 21, 347–356.
  18. ↑ Bradbury, M.W., Berk, P.D., 2004. Lipid metabolism in hepatic steatosis. Clin. Liver Dis. 8, 639–671 (xi).
  19. ↑ Chariot, P., Drogou, I., de Lacroix-Szmania, I., Eliezer-Vanerot, M.C., Chazaud, B., Lombes, A., Schaeffer, A., Zafrani, E.S., 1999. Zidovudine-induced mitochondrial disorder with massive liver steatosis, myopathy, lactic acidosis, and mitochondrial DNA depletion. J. Hepatol. 30, 156–160.
  20. ↑ Donato, M.T., Martinez-Romero, A., Jimenez, N., Negro, A., Herrera, G., Castell, J.V., O’Connor, J.E., Gomez-Lechon, M.J., 2009. Cytometric analysis for drug-induced steatosis in HepG2 cells. Chem. Biol. Interact. 181, 417–423.
  21. ↑ Fromenty, B., Pessayre, D., 1995. Inhibition of mitochondrial beta-oxidation as a mechanism of hepatotoxicity. Pharmacol. Ther. 67, 101–154.
  22. ↑ Fromenty, B., Pessayre, D., 1997. Impaired mitochondrial function in microvesicular steatosis. Effects of drugs, ethanol, hormones and cytokines. J. Hepatol. 26 (Suppl. 2), 43–53.
  23. ↑ Letteron, P., Sutton, A., Mansouri, A., Fromenty, B., Pessayre, D., 2003. Inhibition of microsomal triglyceride transfer protein: another mechanism for drug-induced steatosis in mice. Hepatology 38, 133–140.
  24. ↑ Shokolenko, I., Venediktova, N., Bochkareva, A., Wilson, G.L., Alexeyev, M.F., 2009. Oxidative stress induces degradation of mitochondrial DNA. Nucleic Acids Res. 37, 2539–2548.
  25. ↑ Criddle, D.N., Gillies, S., Baumgartner-Wilson, H.K., Jaffar, M., Chinje, E.C., Passmore, S., Chvanov, M., Barrow, S., Gerasimenko, O.V., Tepikin, A.V., Sutton, R., Petersen, O.H., 2006. Menadione-induced reactive oxygen species generation via redox cycling promotes apoptosis of murine pancreatic acinar cells. J. Biol. Chem. 281, 40485–40492.
  26. ↑ Hanley, P.J., Ray, J., Brandt, U., Daut, J., 2002. Halothane, isoflurane and sevoflurane inhibit NADH:ubiquinone oxidoreductase (complex I) of cardiac mitochondria. J. Physiol. 544, 687–693.
  27. ↑ Moridani, M.Y., Cheon, S.S., Khan, S., O’Brien, P.J., 2003. Metabolic activation of 3- hydroxyanisole by isolated rat hepatocytes. Chem. Biol. Interact. 142, 317–333.
  28. ↑ Pereira, C.V., Moreira, A.C., Pereira, S.P., Machado, N.G., Carvalho, F.S., Sardao, V.A., Oliveira, P.J., 2009. Investigating drug-induced mitochondrial toxicity: a biosensor to increase drug safety? Curr. Drug Saf. 4, 34–54.
  29. ↑ Sanz, A., Caro, P., Gomez, J., Barja, G., 2006. Testing the vicious cycle theory of mitochondrial ROS production: effects of H2O2 and cumene hydroperoxide treatment on heart mitochondria. J. Bioenerg. Biomembr. 38, 121–127.
  30. ↑ Yuan, L., Kaplowitz, N., 2009. Glutathione in liver diseases and hepatotoxicity. Mol. Aspects Med. 30, 29–41.

PK-ADME ? Compound Assessment
PK parameters ?
  • Dosage: 20 - 40 mg daily
  • C max: 40 ng/mL (range 35 to 45 ng/mL)
  • Distribution t1/2: 7 - 14 hours
  • Elimination t1/2: 5 - 7 days
  • Elimination t1/2 of N-desmethyl-tamoxifen: 9-14days.
  • Peak Plasma Time: 3-6 hr
  • Peak Plasma Concentration: 40 ng/mL steady state is achieved in about 4 wk.
  • Tamoxifen is more than 99% protein-bound in serum, predominantly to albumin
  • The volume of distribution is 50-60 l/kg

References:

-Drugbank
-MedScape
-IPCS INCHEM
Therapeutic window ? Therapeutic range: plasma level 77-274 ng/ml for 10-30mg/day dosage, 95-520 ng/ml for 40mg/day dosage.

References:

-Wills SM et al. "Tamoxifen malabsorption after Roux-en-Y gastric bypass surgery: case series and review of the literature" Pharmacotherapy. 2010 Feb; 30(2):217.

Therapeutic window = 100-1000x based on in vitro cell death vs. inhibition of breast cancer cell proliferation. (see in vitro data below)

Tamoxifen causes steatosis and depletion of mitochondrial DNA in mice at 500 umol/kg after 2-4 weeks (note much higher rate of metabolism in mice).

References:

-Isabelle Larosche, Philippe Lette´ ron, Bernard Fromenty, Nathalie Vadrot, Adje´ Abbey-Toby, Ge´ rard Feldmann, Dominique Pessayre, and Abdellah Mansouri, “Tamoxifen Inhibits Topoisomerases, Depletes Mitochondrial DNA, and Triggers Steatosis in Mouse Liver”, JPET 321:526–535, 2007.

Nephrotoxicity is observed in mice at doses of 50 mg/kg (130 umol/kg) (note much higher rate of metabolism in mice)

References:

-Heena Tabassum, Suhel Parvez, Hasibur Rehman, Basu Dev Banerjee, Detlef Siemen and Sheikh Raisuddin, “Nephrotoxicity and its prevention by taurine in tamoxifen induced oxidative stress in mice”,Human & Experimental Toxicology (2007) 26: 509–518.
Metabolically activated ? Tamoxifen itself is a prodrug, having relatively little affinity for its target protein, the estrogen receptor. It is metabolized extensively by hepatic P450 enzymes (CYP2C9, CYP2D6, CYP3A4/5) to several primary and secondary metabolites.

N-desmethyltamoxifen via CYP3A4/5 is quantitatively the major primary metabolite found in plasma and its activity is similar to tamoxifen
4-hydroxytamoxifen via CYP2D6 is 30 – 100- fold more potent than tamoxifen as an estrogen antagonist in vitro. Each is then further metabolized into 4-hydroxy-N-desmethyltamoxifen (endoxifen) which exhibits the same potency and efficacy as 4-hydroxytamoxifen, but is present at notably higher concentrations.

References:

-Desta Z et al. (2004). "Comprehensive evaluation of tamoxifen sequential biotransformation by the human cytochrome P450 system in vitro: prominent roles for CYP3A and CYP2D6". J Pharmacol Exp Ther 310 (3): 1062–75.
-DrugBank
-Medscape
-IPCS INCHEM
-Harrison's PRINCIPLES OF INTERNAL MEDICINE 17th Edition 2008
-Yan Jin et al."CYP2D6 Genotype, Antidepressant Use, and Tamoxifen Metabolism during Adjuvant Breast Cancer Treatment" J Natl Cancer Inst (2005) 97 (1): 30-39.

Omics and IC50 Data ? Compound Assessment
Gene expression profiles known. ?

References:

-Lee MH et al. "Gene expression profiling of murine hepatic steatosis induced by tamoxifen". Toxicol Lett. 2010 Dec 15; 199(3):416-24. PubMed
-Sawada, H., Takami, K., Asahi, S., 2005. A toxicogenomic approach to drug-induced phospholipidosis: analysis of its induction mechanism and establishment of a novel in vitro screening system. Toxicol. Sci. 83, 282–292.
-Nioi, P., Perry, B.K., Wang, E.J., Gu, Y.Z., Snyder, R.D., 2007. In vitro detection of drug-induced phospholipidosis using gene expression and fluorescent phospholipid based methodologies. Toxicol. Sci. 99, 162–173.
-Marta Moya, M. José Gómez-Lechón, José V. Castell, Ramiro Jover. “Enhanced steatosis by nuclear receptor ligands: A study in cultured human hepatocytes and hepatoma cells with a characterized nuclear receptor expression profile”, Chemico-Biological Interactions 184 (2010) 376–387.
-Christopher J. Lelliott, Miguel Lo´pez, R. Keira Curtis, Nadeene Parker, Matthias Laudes, Giles Yeo, Mercedes Jimenez-Lin˜an, Johannes Grosse, Asish K. Saha, David Wiggins, David Hauton, Martin D. Brand, Stephen O’Rahilly, Julian L. Griffin, Geoffrey F. Gibbons, and Antonio Vidal-Puig, “Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steat”, FASEB J. 19, 1108–1119 (2005).
-Oddrun Anita Gudbrandsen, Therese Halvorsen Rost, and Rolf Kristian Berge, “Causes and prevention of tamoxifen-induced accumulation of triacylglycerol in rat liver”, J. Lipid Res. 2006. 47: 2223–2232.
Proteomics profiles known. ?
Metabonomics profiles known. ? Christopher J. Lelliott et al. "Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steatosis" FASEB J. 19, 1108–1119 (2005)
Fluxomics profiles known. ?
Epigenomics profiles known. ? V.P. Tryndyak et al., "Epigenetic reprogramming of liver cells in tamoxifen-induced rat hepatocarcinogenesis", Molecular Carcinogenesis, Vol 46, Issue 3, 187–197, 2007

V. P.Tryndyak et al. "Effect of long-term tamoxifen exposure on genotoxic and epigenetic changes in rat liver: implications for tamoxifen-induced hepatocarcinogenesis", Carcinogenesis vol.27 no.8 pp.1713–1720, 2006

Observed IC50 for in vitro cellular efficacy. ? MCF7 breast cancer cells.
Tamoxifen4-Hydroxytamoxifen
Proliferation EC50 at 7 days100 nM10 nM
Estrogen receptor5 nM0.15 nM

References:

-Ericque Coezy, Jean-Louis Borgna, and Henri Rochefort, “Tamoxifen and Metabolites in MCF7 Cells: Correlation between Binding to Estrogen Receptor and Inhibition of Cell Growth1”, CANCER RESEARCH 42. 317-323. January 1982.
Observed IC50 for in vitro cellular toxicity studies. ? Note that the concentrations implicated for steatotic, cholestatic, and cytotoxic activities in vitro are comparable, in contrast to the clear distinction of steatotic and cholestatic effects from cytotoxicity in patients. Note also the in vitro minimum inhibitory concentrations (MEC’s) below are generally 10- to 100-fold higher than the normal 0.13 uM Cmax.

Excess lipid accumulation in human hepatocytes was detected with MEC = 2.5-10 uM tamoxifen after incubation for 24 h with I mM exogenous fatty acid.

References:

-Marta Moya, M. José Gómez-Lechón, José V. Castell, Ramiro Jover. “Enhanced steatosis by nuclear receptor ligands: A study in cultured human hepatocytes and hepatoma cells with a characterized nuclear receptor expression profile”, Chemico-Biological Interactions 184 (2010) 376–387.

HepG2 cells:

Cytotoxicity35 uM MEC, 57 uM IC50
Lipid accumulation30 uM MEC
Mitochondrial potential7.5 uM MEC
ROSnot detected

References:

-M. Teresa Donatoa, Alicia Martínez-Romero, Nuria Jiménez, Alejandro Negro, Guadalupe Herrera, José V. Castell, José-Enrique O’Connor, M. José Gómez-Lechón, “Cytometric analysis for drug-induced steatosis in HepG2 cells”, Chemico-Biological Interactions 181 (2009) 417–423.

Tamoxifen has been reported to inhibit BSEP with IC%) = 20 uM IC50 (Wang et al., 2003) in non-metabolizing transfected insect cells.

References:

-Er-jia Wang, Christopher N. Casciano, Robert P. Clement, and William W. Johnson, “Fluorescent Substrates of Sister-P-Glycoprotein (BSEP) Evaluated as Markers of Active Transport and Inhibition: Evidence for Contingent Unequal Binding Sites”, Pharmaceutical Research, Vol. 20, No. 4, April 2003.

Phospholipidosis at 8-16 uM in HepG2 cells with gene expression markers:

References:

-Sawada, H., Takami, K., Asahi, S., 2005. A toxicogenomic approach to drug-induced phospholipidosis: analysis of its induction mechanism and establishment of a novel in vitro screening system. Toxicol. Sci. 83, 282–292.
-Nioi, P., Perry, B.K., Wang, E.J., Gu, Y.Z., Snyder, R.D., 2007. In vitro detection of drug induced phospholipidosis using gene expression and fluorescent phospholipid based methodologies. Toxicol. Sci. 99, 162–173.

Tamoxifen cytotoxicity in HepG2 cells (μM):

Table 1. Summary of IC50 Values Determined from the Data in Figs. 1-5
Assay1h2h4h6h24h
ATP quantitation48463934.516.5
MTS reduction6456.544.53719
Resazurin reduction6756.546.541.523.5
LDH release50.547.545.53817.5
Caspase-3/7 activity47.544.537.531.518.5

References:

-T.L. Riss et al. "Use of multiple assay endpoints to investigate the effects of incubation time, dose of toxin and plating density in cell-based cytotoxicity assays" ASSAY and Drug Development Technologies. February 2004, 2(1): 51-62
AssayIC50 (μM) values for Tamoxifen cytotoxicity in HepG2 cells
CyQUANT® Direct40.7
alamarBlue®44.6
CellTiter-Glo®39.6
CellTiter 96® AQueous41.9

References:

-Cytotoxicity and cell proliferation studies BioProbes 59 | June 2009 Invitrogen

Reactive oxygen species detected with apoptosis of HepG2 cells at 30 uM <p>References:

-YS Lee, YS Kang, SH Lee and JA Kim, “Role of NAD(P)H oxidase in the tamoxifen-induced generation of reactive oxygen species and apoptosis in HepG2 human hepatoblastoma cells”, Cell Death and Differentiation (2000) 7, 925 - 932.

Topoisomerase was inhibited by 100 uM tamoxifen in vitro.

References:

-Isabelle Larosche, Philippe Lette´ ron, Bernard Fromenty, Nathalie Vadrot, Adje´ Abbey-Toby, Ge´ rard Feldmann, Dominique Pessayre, and Abdellah Mansouri, “Tamoxifen Inhibits Topoisomerases, Depletes Mitochondrial DNA, and Triggers Steatosis in Mouse Liver”, JPET 321:526–535, 2007.

Electron transport chain IC50 (isolated bovine heart mitochondria components in vitro). Lower IC50s in this assay compared to cell assays is consistent with higher tamoxifen-binding protein levels in culture media. Complex I >50 uM Complex II/III 15 uM Complex IV 27 uM Complex V 8 uM 4-Hydroxytamoxifen is approximately 3-fold less active vs. oxidative phosphorylation.

References:

-Sashi Nadanaciva, Autumn Bernal, Robert Aggeler, Roderick Capaldi, Yvonne Will, “Target identification of drug induced mitochondrial toxicity using immunocapture based OXPHOS activity assays”, Toxicol In Vitro. 2007;21(5):902-11.
-Carla M.P. Cardoso, Anto´nio J.M. Moreno, Leonor M. Almeida, Jose´ B.A. Custo´dio, “4-Hydroxytamoxifen induces slight uncoupling of mitochondrial oxidative phosphorylation system in relation to the deleterious effects of tamoxifen”,Toxicology 179 (2002)

This report that tamoxifen does not cause loss of cell viability in HepG2 cells is inconsistent with other reports:

  • Alamar Blue (NADH) MEC > 30 uM
  • Hoechst 33342 (DNA) MEC > 30 uM

References:

-Willem G.E.J. Schoonen, Jeroen A.D.M. de Roos, Walter M.A. Westerink, Eric De´biton, “Cytotoxic effects of 110 reference compounds on HepG2 cells and for 60 compounds on HeLa, ECC-1 and CHO cells. II Mechanistic assays on NAD(P)H, ATP and DNA contents”,Toxicology in Vitro 19 (2005) 491–503.

Physical Properties ? Compound Assessment
Accepted and listed within the ToxCast/Tox21 program. ? Yes - Included in ToxCast Phase I and II Chemicals List.
Substance stability. ? Tamoxifen should be stable for at least two years when stored desiccated at 2-8E C in the dark. Solutions are sensitive to UV light. Photolysis products (reported for Tamoxifen Citrate, TC) are the E isomer and the phenanthrenes formed by cyclization of both isomers. It is possible that solutions in DMSO may be stable when stored at -20E C in the dark (as with TC) Sigma Aldrich T5648 Product Information Sheet
Soluble in buffer solution at 30 times the in vitro IC50 for toxicity. ? Solubility in water <0.01% (20°C) Sigma Aldrich T5648 Product Information Sheet


estimated intrinsic solubility : 1.3329E-3 mg/ml
estimated solubility in pure water at pH 8.62: 2.9055E-3mg/ml
estimated solubility in water at pH 7.4: 2.70E-2 mg/ml
(Calculations performed using ACD/PhysChem v 9.14) Solubility as a function of pH and other parameters available on the wiki

Solubility in DMSO 100 times buffer solubility. ? Soluble Sigma Aldrich T5648 Product Information Sheet
Vessel binding properties. ?
Vapor pressure. (Non-volatile) ? estimated vapor pressure: 3.46E-08 mmHg (Calculation performed using EPI Suite v4.10)

Calculated/Predicted Properties

Water Solubility Results
pH Sol,mg/ml 27+ 0 Graph
2 1.68 100 - Tamoxifen solubility.png
5.5 0.93 99.9 -
6.5 0.19 99.4 0.6
7.4 2.70E-2 95.1 4.9
10 1.40E-3 4.7 95.3
Summary Solubility Data
Intrinsic Solubility,mg/ml 1.3329E-3
Intrinsic Solubility,log(S,mol/l) -5.4452
Solubility in Pure Water at pH = 8.62,mg/ml 2.9055E-3
Calculations performed using ACD/PhysChem v 9.14
LogD Results
pH LogD Graph
2 4.78 Tamoxifen logd.png
5.5 5.04
6.5 5.74
7.4 6.58
10 7.86
Calculations performed using ACD/PhysChem v 9.14
Single-valued Properties
Property Value Units Error
LogP 7.88 0.75
MW 371.51 -
PSA 12.47 -
FRB 8 -
HDonors 0 -
HAcceptors 2 -
Rule Of 5 1 -
Molar Refractivity 118.89 cm3 0.3
Molar Volume 356.24 cm3 3
Parachor 898.16 cm3 4
Index of Refraction 1.58 0.02
Surface Tension 40.41 dyne/cm 3
Density 1.04 g/cm3 0.06
Polarizability 47.13 10E-24 cm3 0.5
Calculations performed using ACD/PhysChem v 9.14
Property Name Value Units Source
pKa 8.52 SPARC v4.5
Estimated VP 3.46E-08 mm Hg EPI Suite v4.10
Estimated VP 4.61E-06 Pa EPI Suite v4.10
Estimated Water Solubility 0.1936 mg/L EPI Suite v4.10
WATERNT Frag Water Solubility Estimate 0.024594 mg/L EPI Suite v4.10
pKa Results
Acidic/Basic Acidic/Basic Aparrent pKa Value Error
27 MB 8.69 0.28
A = Acidic
B = Basic
MA = Most Acidic
MB = Most Basic
Calculations performed using ACD/PhysChem v 9.14

Authors of this ToxBank wiki page

David Bower, Egon Willighagen, Matthew Clark
Retrieved from "http://wiki.toxbank.net/wiki/Tamoxifen"
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