Dataset Information

The active tamoxifen metabolite endoxifen (4OHNDtam) strongly down-regulates cytokeratin 6 (CK6) in MCF-7 breast cancer cells.

ABSTRACT: INTRODUCTION:Tamoxifen is an anti-estrogen drug used in treatment of Estrogen Receptor (ER) positive breast cancer. Effects and side effects of tamoxifen is the sum of tamoxifen and all its metabolites. 4-Hydroxytamoxifen (4OHtam) and 4-hydroxy-N-demethyltamoxifen (4OHNDtam, endoxifen) both have ER affinity exceeding that of the parent drug tamoxifen. 4OHNDtam is considered the main active metabolite of tamoxifen. Ndesmethyltamoxifen (NDtam) is the major tamoxifen metabolite. It has low affinity to the ER and is not believed to influence tumor growth. However, NDtam might mediate adverse effects of tamoxifen treatment. In this study we investigated the gene regulatory effects of the three metabolites of tamoxifen in MCF-7 breast cancer cells. MATERIAL AND METHODS:Using concentrations that mimic the clinical situation we examined effects of 4OHtam, 4OHNDtam and NDtam on global gene expression in 17?-estradiol (E2) treated MCF-7 cells. Transcriptomic responses were assessed by correspondence analysis, differential expression, gene ontology analysis and quantitative real time PCR (Q-rt-PCR). E2 deprivation and knockdown of Steroid Receptor Coactivator-3 (SRC-3)/Amplified in Breast Cancer 1 (AIB1) mRNA in MCF-7 cells were performed to further characterize specific effects on gene expression. RESULTS:4OHNDtam and 4OHtam caused major changes in gene expression compared to treatment with E2 alone, with a stronger effect of 4OHNDtam. NDtam had nearly no effect on the global gene expression profile. Treatment of MCF-7 cells with 4OHNDtam led to a strong down-regulation of the CytoKeratin 6 isoforms (KRT6A, KRT6B and KRT6C). The CytoKeratin 6 mRNAs were also down-regulated in MCF-7 cells after E2 deprivation and after SRC-3/AIB1 knockdown. CONCLUSION:Using concentrations that mimic the clinical situation we report global gene expression changes that were most pronounced with 4OHNDtam and minimal with NDtam. Genes encoding CytoKeratin 6, were highly down-regulated by 4OHNDtam, as well as after E2 deprivation and knockdown of SRC-3/AIB1, indicating an estrogen receptor-dependent regulation.

SUBMITTER: Helland T

PROVIDER: S-EPMC4395096 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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The active tamoxifen metabolite endoxifen (4OHNDtam) strongly down-regulates cytokeratin 6 (CK6) in MCF-7 breast cancer cells.

Helland Thomas T Gjerde Jennifer J Dankel Simon S Fenne Ingvild S IS Skartveit Linn L Drangevåg Andreas A Bozickovic Olivera O Flågeng Marianne Hauglid MH Søiland Håvard H Mellgren Gunnar G Lien Ernst A EA

PloS one 20150413 4

<h4>Introduction</h4>Tamoxifen is an anti-estrogen drug used in treatment of Estrogen Receptor (ER) positive breast cancer. Effects and side effects of tamoxifen is the sum of tamoxifen and all its metabolites. 4-Hydroxytamoxifen (4OHtam) and 4-hydroxy-N-demethyltamoxifen (4OHNDtam, endoxifen) both have ER affinity exceeding that of the parent drug tamoxifen. 4OHNDtam is considered the main active metabolite of tamoxifen. Ndesmethyltamoxifen (NDtam) is the major tamoxifen metabolite. It has low ...[more]

PMID: 25867603

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Project description:Purpose Endoxifen is a tamoxifen metabolite with potent antiestrogenic activity. Patients and Methods We performed a phase I study of oral Z-endoxifen to determine its toxicities, maximum tolerated dose (MTD), pharmacokinetics, and clinical activity. Eligibility included endocrine-refractory, estrogen receptor-positive metastatic breast cancer. An accelerated titration schedule was applied until moderate or dose-limiting toxicity occurred, followed by a 3+3 design and expansion at 40, 80, and 100 mg per day. Tumor DNA from serum (circulating cell free [cf); all patients] and biopsies [160 mg/day and expansion]) was sequenced. Results Of 41 enrolled patients, 38 were evaluable for MTD determination. Prior endocrine regimens during which progression occurred included aromatase inhibitor (n = 36), fulvestrant (n = 21), and tamoxifen (n = 15). Patients received endoxifen once daily at seven dose levels (20 to 160 mg). Dose escalation ceased at 160 mg per day given lack of MTD and endoxifen concentrations > 1,900 ng/mL. Endoxifen clearance was unaffected by CYP2D6 genotype. One patient (60 mg) had cycle 1 dose-limiting toxicity (pulmonary embolus). Overall clinical benefit rate (stable > 6 months [n = 7] or partial response by RECIST criteria [n = 3]) was 26.3% (95% CI, 13.4% to 43.1%) including prior tamoxifen progression (n = 3). cfDNA mutations were observed in 13 patients ( PIK3CA [n = 8], ESR1 [n = 5], TP53 [n = 4], and AKT [n = 1]) with shorter progression-free survival ( v those without cfDNA mutations; median, 61 v 132 days; log-rank P = .046). Clinical benefit was observed in those with ESR1 amplification (tumor; 80 mg/day) and ESR1 mutation (cfDNA; 160 mg/day). Comparing tumor biopsies and cfDNA, some mutations ( PIK3CA, TP53, and AKT) were undetected by cfDNA, whereas cfDNA mutations ( ESR1, TP53, and AKT) were undetected by biopsy. Conclusion In endocrine-refractory metastatic breast cancer, Z-endoxifen provides substantial drug exposure unaffected by CYP2D6 metabolism, acceptable toxicity, and promising antitumor activity.

Dataset Information

The active tamoxifen metabolite endoxifen (4OHNDtam) strongly down-regulates cytokeratin 6 (CK6) in MCF-7 breast cancer cells.

Publications

The active tamoxifen metabolite endoxifen (4OHNDtam) strongly down-regulates cytokeratin 6 (CK6) in MCF-7 breast cancer cells.

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