Tamoxifen In Breast Cancer Research Articles

The ERα-miR-575-p27 feedback loop regulates tamoxifen sensitivity in ER-positive Breast Cancer.

Background: Breast cancer is the most common malignancy, and approximately 70% of breast cancers are estrogen receptor-α (ERα) positive. The anti-estrogen tamoxifen is a highly effective and commonly used treatment for patients with ER+ breast cancer. However, 30% of breast cancer patients fail adjuvant tamoxifen therapy and most of metastatic breast cancer patients develop tamoxifen resistance. Although increasing evidence suggests that microRNA (miRNA) dysregulation influences tamoxifen sensitivity, the mechanism of the cross-talk between miRNA and ERα signaling remains unclear. miR-575 has been reported to be involved in carcinogenesis and progression, however, the role of miR-575 in breast cancer remains limited. The aim of this study was to understand the mechanism of miR-575 in breast cancer tamoxifen resistance.Method: RT-qPCR was employed to assess miR-575 expression in breast cancer tissues and cell lines. The association of miR-575 expression with overall survival in patients with breast cancer was evaluated with KM plotter. Additionally, the effects of miR-575 on breast cancer proliferation and tamoxifen sensitivity were investigated both in vitro and in vivo. Bioinformatic analyses and luciferase reporter assays were performed to validate CDKN1B and BRCA1 as direct targets of miR-31-5p. The ERα binding sites in the miR-575 promoter region was validated with ChIP and luciferase assays. ERα interactions with CDKN1B, cyclin D1 or BRCA1 were determined by IP analysis, and protein expression levels and localization were analyzed by western blotting and immunofluorescence, respectively.Results: miR-575 levels were higher in ER+ breast cancer than in ER- breast cancer and patients with high miR-575 expression had a significantly poorer outcome than those with low miR-575 expression. ERα bound the miR-575 promoter to activate its transcription, and tamoxifen treatment downregulated miR-575 expression in ER+ breast cancer. Overexpression of miR-575 decreased tamoxifen sensitivity by targeting CDKN1B and BRCA1. CDKN1B and BRCA1 were both able to antagonize ERα activity by inhibiting ERα nuclear translocation and interaction with cyclin D1. Furthermore, miR-575 expression was found to be upregulated in ER+ breast cancer cell with acquired tamoxifen resistance, whereas depletion of miR-575 partially re-sensitized these cells to tamoxifen by regulation of CDKN1B.Conclusions: Our data reveal the ERα-miR-575-CDKN1B feedback loop in ER+ breast cancer, suggesting that miR-575 can be used as a prognostic biomarker in patients with ER+ breast cancer, as well as a predictor or a promising target for tamoxifen sensitivity.

Hormonal status affects plasma exposure of tamoxifen and its main metabolites in tamoxifen-treated breast cancer patients

BackgroundTamoxifen 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.MethodsTAM-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.ResultsPostmenopausal 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 [β-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).ConclusionThe 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 registrationRBR-7tqc7k.

Tamoxifen and antidepressant’s co-prescription: general practitioners and pharmacist’s alert

Abstract Issue Well known drug-drug interaction with some antidepressants, especially selective serotonin reuptake inhibitors which reduce tamoxifen’s effectiveness and associated with an increased risk of death from breast cancer. Description of the problem To identify and characterize the exposure to antidepressants in women with breast cancer treated with tamofixen in a west french area. Retrospective population based cohort study; claims from the French Health insurance database. Women living in Pays de la Loire area, aged 20 years or older treated with tamoxifen for breast cancer in 2018 who had concomitant treatment with antidepressants. Call phone to general practitioner’s and meeting with pharmacist when a high or moderate level drug-drug interaction’s was identified. Results Of 4138 women treated with tamoxifen, 497 (12%) received an antidepressant treatment in 2018, corresponding to 571 co-prescriptions. Of them, 74 (13%) was moderate level drug-drug interaction, 66 (11.6%) high level and 307 (53.8%) weak level.70% of high level drug-drug interaction were due to paroxetine and 43% of moderate level due to duloxetine. For these co-prescriptions, concomitant patient’s exposure was for more than four months in 22% cases. 127 different general practitioners and 152 pharmacists (339 different dispensation’s date) were concerned by these drug-drug interactions. Lessons French health insurance medical department has contacted general practitioners or pharmacists concerned by these drug-drug interactions. We informed general practitioners to be aware about women treated with tamoxifen when co-prescription with an antidepressant is necessary, preference should be given to one of them that show little or no inhibition of cytochrome P450 2D6. Key messages Mediation medication and detection of drug-drug interaction by pharmacist. Preferential choice of antidepressant by general practitioner or women treat with co-prescription (tamoxifen and antidepressant).

Can the levonorgestrel intrauterine system improve outcomes in women taking adjuvant tamoxifen for breast cancer?

Can the levonorgestrel intrauterine system improve outcomes in women taking adjuvant tamoxifen for breast cancer?

Factors associated with endometrial pathology during tamoxifen therapy in women with breast cancer: a retrospective analysis of 821 biopsies

This study evaluated the factors associated with endometrial pathologies during tamoxifen use in women with breast cancer. This study analyzed 821 endometrial biopsies from women who received tamoxifen for breast cancer. Clinical characteristics were compared according to the presence of endometrial pathology (atypical hyperplasia and cancer). In addition, patients with endometrial polyps were compared with women with normal histology. Among 821 biopsies, atypical endometrial hyperplasia and cancer were diagnosed in 7 women each. Endometrial polyps were found in 173 women, and 634 women presented normal histology. In comparing women with endometrial pathology (atypical hyperplasia and cancer, n = 14) and those without pathology, parity was significantly lower (P = 0.014) and endometrial thickness was significantly higher (P < 0.001) in women with pathology. In addition, abnormal uterine bleeding was more common in the pathology group (P < 0.001). However, age, body mass index, menopausal status, intrauterine device use, history of diabetes mellitus, and duration of tamoxifen use did not differ according to the presence of pathology. In comparing women with endometrial polyps and those with normal endometrium, significant differences were found in parity (P < 0.001), duration of tamoxifen use (P = 0.003), and endometrial thickness (P < 0.001), but not in the presence of abnormal vaginal bleeding. Parity, endometrial thickness, and the presence of abnormal vaginal bleeding, but not age, body mass index, and menopausal status, may be associated with endometrial pathology during tamoxifen use in women with breast cancer. This finding might provide useful information for gynecological surveillance and counseling during tamoxifen treatment.

Baihe Zhimu formula attenuates the efficacy of tamoxifen against breast cancer in mice through modulation of CYP450 enzymes

BackgroundMajor depression is an important complication in patients with breast cancer, but is an underrecognized and undertreated condition in this population. The Baihe Zhimu Tang (BZ formula) is a traditional Chinese formula consisting of Lilium brownii var. viridulum Baker (L. brownii) and Anemarrhena asphodeloides (A. asphodeloides) Bunge that is used for the treatment of depression. However, the interaction between tamoxifen and BZ formula is frequently overlooked by traditional and alternative medical doctors. In the present study, the influence of BZ formula on the effectiveness of tamoxifen in breast cancer in mice and the effects of tamoxifen on the antidepressant effect of BZ formula and its major components mangiferin and timosaponin BII in mice were investigated.MethodsIdentification of the major components of BZ formula was performed using fast HPLC-tandem mass spectrometry (HPLC-MS/MS). The main flavonoids and saponins in A. asphodeloides were determined by HPLC-UV and HPLC-ELSD, separately. The antidepressant efficacy of BZ formula was evaluated using a mouse tail-suspension test. The effects of BZ formula on the antineoplastic activity of tamoxifen were performed in a mouse xenograft model of human breast cancer MCF-7 cells. P450 activity was determined using microsomal incubations by HPLC-MS/MS. Measurement of serum concentrations of tamoxifen and its metabolites was used by HPLC-MS/MS.ResultsBZ formula attenuated the effectiveness of tamoxifen treatment of breast cancer and reduced the concentrations of endoxifen and 4-OH-tamoxifen in tumor-bearing mice. Of two of the major components of BZ formula, the antidepressant effect of mangiferin, but not timosaponin BII, was significantly inhibited by tamoxifen in mice. BZ formula and its component mangiferin also significantly inhibited CYP450 enzyme activity in rat liver microsomes.ConclusionBZ formula attenuated the effectiveness of tamoxifen in treatment of breast cancer in mice by influencing CYP450 enzymes. The present study laid a foundation for the treatment of patients with breast cancer and depression by BZ formula or other Chinese herbal formulas containing A. asphodeloides.

Younger tamoxifen-treated breast cancer patients also had higher risk of endometrial cancer and the risk could be reduced by sequenced aromatase inhibitor use: A population-based study in Taiwan.

Objective:Previous Western studies reported that older (≥50 years) breast cancer survivors with tamoxifen treatment had higher risk of endometrial cancer. This study aims to disclose whether younger (<50 years) tamoxifen-treated breast cancer patients also had higher risk of endometrial cancer and to examine whether sequenced aromatase inhibitor (AI) use could reduce the risk.Materials and Methods:A population-based cohort of 39,216 newly diagnosed breast cancer patients was identified from Taiwan National Health Insurance Database from 1999 to 2012. The risk of endometrial cancer in nonusers (n = 14,588), tamoxifen-only (n = 19,302), and sequenced AI (n = 5326) users was compared with Cox regression analysis and was adjusted with age, diabetes, hypertension, and chemotherapy.Results:During the 14-year study period, 133 patients were diagnosed with subsequent endometrial cancers. Compared with nonusers, tamoxifen-only users had higher risk of endometrial cancer (14-year incidence 1.7% vs. 0.3%; adjusted hazard ratio [HR] 3.90; 95% confidence interval [CI], 2.37–6.42). This was observed in both older (≥50 years) and younger (40–50 years) age groups. Adjusted HR (95% CI) for the latter was 3.74 (1.65–8.48). This risk persisted after cessation of tamoxifen use. The risk of endometrial cancer was lower in sequenced AI when compared with tamoxifen-only users (adjusted HR 0.43; 95% CI, 0.25–0.72).Conclusions:Not only patients ≥50 years but also younger (40–49 years) patients with tamoxifen treatment had higher risk of subsequent endometrial cancer in this nation-wide cohort. We suggest regular gynecologic monitoring not only during active use but also during follow-up phase. Sequenced AI use may reduce the risk of endometrial cancer in tamoxifen-treated breast cancer patients.

Exploring the Molecular Mechanism of the Drug-Treated Breast Cancer Based on Gene Expression Microarray.

Breast cancer (BRCA) remains the leading cause of cancer morbidity and mortality worldwide. In the present study, we identified novel biomarkers expressed during estradiol and tamoxifen treatment of BRCA. The microarray dataset of E-MTAB-4975 from Array Express database was downloaded, and the differential expressed genes (DEGs) between estradiol-treated BRCA sample and tamoxifen-treated BRCA sample were identified by limma package. The pathway and gene ontology (GO) enrichment analysis, construction of protein-protein interaction (PPI) network, module analysis, construction of target genes—miRNA interaction network and target genes-transcription factor (TF) interaction network were performed using bioinformatics tools. The expression, prognostic values, and mutation of hub genes were validated by SurvExpress database, cBioPortal, and human protein atlas (HPA) database. A total of 856 genes (421 up-regulated genes and 435 down-regulated genes) were identified in T47D (overexpressing Split Ends (SPEN) + estradiol) samples compared to T47D (overexpressing Split Ends (SPEN) + tamoxifen) samples. Pathway and GO enrichment analysis revealed that the DEGs were mainly enriched in response to lysine degradation II (pipecolate pathway), cholesterol biosynthesis pathway, cell cycle pathway, and response to cytokine pathway. DEGs (MCM2, TCF4, OLR1, HSPA5, MAP1LC3B, SQSTM1, NEU1, HIST1H1B, RAD51, RFC3, MCM10, ISG15, TNFRSF10B, GBP2, IGFBP5, SOD2, DHF and MT1H), which were significantly up- and down-regulated in estradiol and tamoxifen-treated BRCA samples, were selected as hub genes according to the results of protein-protein interaction (PPI) network, module analysis, target genes—miRNA interaction network and target genes-TF interaction network analysis. The SurvExpress database, cBioPortal, and Human Protein Atlas (HPA) database further confirmed that patients with higher expression levels of these hub genes experienced a shorter overall survival. A comprehensive bioinformatics analysis was performed, and potential therapeutic applications of estradiol and tamoxifen were predicted in BRCA samples. The data may unravel the future molecular mechanisms of BRCA.

Abstract 2121: Overcoming tamoxifen resistance and inhibiting metastatic recurrence in estrogen receptor-positive breast cancer

Abstract Estrogen receptor (ER)-positive breast cancer accounts for almost 75% of all breast cancers. Tamoxifen has been used for over 40 years to treat early, locally advanced and metastatic ER-positive breast cancer; however, patients develop resistance over time. Furthermore, metastatic recurrence, the major cause of death, is common in ER-positive breast cancer patients whose cancer progressed on tamoxifen and other hormone therapies. In this line, we and others reported epithelial-mesenchymal (EMT)-like changes upon acquisition of tamoxifen resistance hinting towards the co-occurrence of resistance and metastatic abilities of the cells. However, little is known about common molecular mediators of drug resistance and metastatic recurrence. Therefore, we addresses the question of how we concurrently overcome tamoxifen resistance and prevent lethal metastatic recurrence whereby eliminating the mortality associated with metastatic breast cancer. Combining whole-transcriptome sequencing and downstream pathway analysis, we identified cyclic AMP (cAMP) signaling to be the most significantly altered pathway in acquired tamoxifen resistant breast cancer cells. We found that PDE4D (Phosphodiesterase 4D), which hydrolyzes cAMP, was significantly overexpressed in both MCF-7 and T47D tamoxifen-resistant (TamR) cells. We demonstrated that PDE4D inhibition overcomes tamoxifen resistance in cell lines and tumor xenografts via cAMP induced endoplasmic reticulum stress and cell death. Importantly, our TamR cells have partial EMT and enrichment of TGF-beta signaling, and PDE4D inhibition in combination with tamoxifen inhibited cell migration in vitro and blocked TGF-beta induced EMT. RNA-Seq experiment also identified one of the highly oncogenic long non-coding RNAs (lncRNA) to be upregulated in TamR cells, and its targeting inhibits PDE4D and leads to tamoxifen sensitization. We showed that higher expressions of both PDE4D and the candidate lncRNA predict worse survival in tamoxifen-treated breast cancer patients. Currently, we are testing the tamoxifen sensitizer and metastasis blocker functions of PDE4D and our candidate lncRNA using patient-derived xenograft (PDX) models of metastatic ER-positive breast cancer. Overall, our results suggest that targeting PDE4D, or its upstream regulatory lncRNA, can simultaneously overcome tamoxifen resistance and prevent metastatic recurrence in ER-positive breast cancer. This is then expected to dramatically reduce mortality rates among ER-positive breast cancer patients in future. Citation Format: Pelin Gulizar Ersan, Ozge Saatci, Oguzhan Tarman, Rasmi Mishra, Nevin Belder, Unal Metin Tokat, Yasser Riazalhosseini, Ozgur Sahin. Overcoming tamoxifen resistance and inhibiting metastatic recurrence in estrogen receptor-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2121.

Hepatoprotective effect of celecoxib against tamoxifen-induced liver injury via inhibiting ASK-1/JNK pathway in female rats

Hepatotoxicity is a common side effect encountered with tamoxifen (TAM) administration. Due to the great value of TAM in breast cancer treatment, hepato-protection is seriously recommended. AimsThe present study investigated the hepato-protective effect of celecoxib (CX) against TAM-induced hepatotoxicity in rats. Main methodsFemale rats were injected with TAM (45 mg/kg, i.p.) for 7 days and given CX (15 mg/kg, orally) 7 days before TAM injection, then continued for the following 7 days. Key findingsAdministration of CX for 14 days conferred significant hepatoprotection against TAM-induced hepatotoxicity indexed by decreased liver/body weight ratio, boosted cytoprotection and substantial reduction in serum LDH activity besides functional hepatic improvement; marked decrease in ALT, AST and ALP with significant elevation in serum albumin. Oxidant/antioxidants hemostasis was improved upon CX treatment with profound decrease in hepatic MDA content and elevation of GSH and SOD levels. Furthermore, hepatic content of NO decreased along with significant decrease in ASK-1, JNK and Bax levels as well as TNFα and caspase3 expression. Finally, CX administration resulted in obvious diminution of TAM-induced necrotic and apoptotic alterations. SignificanceCelecoxib might be used in combination with TAM in treatment protocol of breast to prevent liver injury induced by TAM and further clinical studies might be needed to approve this notion.

The levonorgestrel-releasing intrauterine device induces endometrial decidualisation in women on tamoxifen

There is conflicting literature on whether the levonorgestrel-releasing intrauterine system (LNG-IUS; Mirena®) induces decidualisation in the tamoxifen-treated endometrium. The expression of the decidualisation marker IGFBP-1 was measured using immunohistochemistry in endometrial biopsies and in serum (using ELISA) of 20 postmenopausal women at the start of tamoxifen-treatment for breast cancer. Ten women were then fitted with LNG-IUS and the other ten received tamoxifen-treatment only and acted as controls. Samples were taken at baseline and after 12 months. At baseline, all endometrial samples were negative for IGFBP-1 and at 12 months, IGFBP-1 was only expressed in the endometria of women fitted with the LNG-IUS, confirming the observed histological features of decidualisation. By contrast, serum IGFBP-1 concentrations were increased by tamoxifen, but not in the group receiving LNG-IUS. In conclusion, tamoxifen induces a rise in serum IGFBP-1 suggesting a systemic, possibly hepatic effect, whilst LNG abrogates this in both the liver and endometrium.Impact statementWhat is already known on this subject? Previous reports of the use of LNG-IUS in women on tamoxifen have provided conflicting evidence as to whether the endometrium exhibited decidualisation or not. These reports were however based solely on histological examination and lacked supporting biochemical data.What do the results of this study add? After 12 months of treatment with LNG-IUS, the endometria of women on tamoxifen show histological features of decidualisation and the presence of the decidualisation marker IGFBP-1, suggesting that levonorgestrel protects the tamoxifen-treated uterus from additional pathology by causing decidualisation. Serum levels of IGFBP-1 were expected to be a reflection of uterine production, but contrary to expectations, higher levels were identified in women on tamoxifen alone. These data suggest that an inhibition of tamoxifen-induced serum IGFBP-1 production (possibly from a hepatic source) by LNG-IUS occurred and indicates independent systemic effects of both drugs in post menopausal breast cancer patients.What are the implications of these findings for clinical practice and/or further research? This research demonstrated a mechanism for endometrial protection in women on tamoxifen. It also alerts clinicians to the fact that both tamoxifen and LNG-IUS exert systemic effects in this patient group.

Oestrogen Non-Genomic Signalling is Activated in Tamoxifen-Resistant Breast Cancer.

Endocrine therapies targeting oestrogen signalling have significantly improved breast cancer management. However, their efficacy is limited by intrinsic and acquired resistance to treatment, which remains a major challenge for oestrogen receptor α (ERα)-positive tumours. Though many studies using in vitro models of endocrine resistance have identified putative actors of resistance, no consensus has been reached. We demonstrated previously that oestrogen non-genomic signalling, characterized by the formation of the ERα/Src/PI3K complex, is activated in aggressive breast cancers (BC). We wondered herein whether the activation of this pathway is also involved in resistance to endocrine therapies. We studied the interactions between ERα and Src or PI3K by proximity ligation assay (PLA) in in-vitro and in-vivo endocrine therapy-resistant breast cancer models. We reveal an increase in ERα/Src and ERα/PI3K interactions in patient-derived xenografts (PDXs) with acquired resistance to tamoxifen, as well as in tamoxifen-resistant MCF-7 cells compared to parental counterparts. Moreover, no interactions were observed in breast cancer cells resistant to other endocrine therapies. Finally, the use of a peptide inhibiting the ERα–Src interaction partially restored tamoxifen sensitivity in resistant cells, suggesting that such components could constitute promising targets to circumvent resistance to tamoxifen in BC.

NAMPT regulates PKM2 nuclear location through 14-3-3ζ: Conferring resistance to tamoxifen in breast cancer.

The resistance against tamoxifen therapy has become one of the major obstacles in the clinical treatment of breast cancer. Nicotinamide phosphoribosyltransferase (NAMPT) is an essential enzyme catalyzing nicotinamide adenine dinucleotide biosynthesis and is important for tumor metabolism. The study here sought to explore the effect of NAMPT on breast cancer survival with tamoxifen conditioning. We found that NAMPT was highly expressed in breast cancer cells compared with normal mammary epithelial cells. Inhibition of NAMPT by FK866 inhibited cell viability and aggravated apoptosis in cancer cells treated with 4-hydroxytamoxifen. NAMPT overexpression upregulated 14-3-3ζ expression. Knockdown of 14-3-3ζ reduced cell survival and promoted apoptosis. Activation of Akt signaling, rather than ERK1/2 pathway, is responsible for 14-3-3ζ regulation by NAMPT overexpression. Furthermore, NAMPT overexpression led to PKM2 accumulation in the cell nucleus and could be dampened by 14-3-3ζ inhibition. In addition, NAMPT overexpression promoted xenografted tumor growth and apoptosis in nude mice, while 14-3-3ζ inhibition attenuated its effect. Collectively, our data demonstrate that NAMPT contributes to tamoxifen resistance through regulation of 14-3-3ζ expression and PKM2 translocation.

Oncotype recurrence score (RS) and discordance in patients with secondary invasive breast events (SIBE).

e12016 Background: Oncotype RS is a 21-gene assay used to predict the likelihood of distant recurrence and benefit of chemotherapy in patients with node-negative, tamoxifen treated breast cancer (BC). We developed a database to determine rates of SIBE and identify cases of discordance between Oncotype RS and tumor grade (TG). Our goal was to recognize patients with discordant tumors who had SIBE, with implications for patient management. Methods: We identified 618 patients (645 samples) with early-stage, hormone positive BC treated between 2006-2018, with tumor characteristics available for analysis. Among these patients, there were 24 SIBE (n = 24) from 23 patients (3.7%). When stratified by RS using traditional cutoffs (Paik, 2004), rates of SIBE were 2.8%, 5.0% and 4.5% in low, intermediate and high-risk groups respectively. Discordance was defined as 1 or 2-step difference between RS (low, intermediate, high risk) and TG (well (WD), moderately (MD) and poorly (PD) differentiated). Prior studies demonstrated 7-19% “2-step discordance” between TG and RS (i.e. PD tumors with low-risk RS or WD tumors with high-risk RS). N(%) or median were used to describe patients’ characteristics between groups and compared by Mann-Whitney U test at the confidence level of 5%. Results: Of the 24 SIBE, 42% had low RS ( &lt; 18), 46% had intermediate RS (18-30) 12% had high RS ( &gt; 31). Median RS was 22 and median age at secondary event was 61 (67% post-menopausal). At time of SIBE, 54% were metastatic, 25% locally recurrent and 21% contralateral. Within this dataset, 63% were 1-step and 4% were 2-step discordant. Significantly fewer patients were treated with systemic chemotherapy in the discordant group (p &lt; 0.01), though 94% displayed MD or PD TG. Discordant tumors tended to have lower RS (median 14 vs. 24) and be larger. There were no significant differences in menopausal status or Oncotype ER/PR score. Conclusions: Although the sample size of patients with SIBE is small, our data suggests that patients with discordant tumors of low-risk RS but higher TG may be receiving inadequate treatment (i.e. no chemotherapy). In addition to RS, other factors such as discordance, TG and size should perhaps be considered when determining treatment plans.

Opportunities of the pharmacogenetic approach to personalized tamoxifen breast cancer therapy: case reports

Tamoxifen is the selective modulator of estrogen receptors. Nowadays, it is widely used for treatment of premenopausal women with ER(+) breast cancer likewise for postmenopausal women with treatment contraindications to aromatase inhibitors. Tamoxifen is a prodrug which is metabolized by cytochrome P450 (CYP): CYP2D6, CYP3A4, CYP3A5, CYP2C9, CYP2C19 to active metabolites. There is high variability in the CYP genes therefore differences in tamoxifen metabolism, tamoxifen individual response and efficacy are observed among patients. This article presents two clinical case reports. Both patients have breast cancer luminal A subtype, similar prognosis and are administered tamoxifen but they have diverse clinical effects. Patients responded to the survey questionnaire, then samples of buccal epithelium were taken for genetic analysis of CYP2D6*4, CYP3A5*3, CYP3A4*17, CYP2C9*2,3, CYP2C19*2,3, ABCB1 gene mutations by use of real time PCR. In patient A samples were detected significant mutations in CYP2D6 (*1/*4), CYP3A5 (*3/*3) и CYP2С9 (*2/*3), but there were no mutations detected in patient B. It is interesting that patient B has had prominent tamoxifen adverse effects, such as flushes, ostealgia, faintness, after 1 month of tamoxifen therapy. Patient A has taken tamoxifen for 19 months without any adverse effects. Also there is a review in this article about clinical value of different CYP2D6, CYP3A5, CYP2C9 polymorphisms. Additionally, we make a suggestion about the role of polymorphisms in tamoxifen adverse effects and the way of solution for problems of tamoxifen resistance. We suppose that routine genetic study before tamoxifen administration would help to predict individual intolerance and increase the efficacy of treatment.

Dynamic Effects of CYP2D6 Genetic Variants in a Set of Poor Metaboliser Patients with Infiltrating Ductal Cancer Under Treatment with Tamoxifen

Breast cancer is a group of multigenic diseases. It is the most common cancer diagnosed among women worldwide and is often treated with tamoxifen. Tamoxifen is catalysed by cytochrome P450 2D6 (CYP2D6), and inter-individual variations in the enzyme due to single nucleotide polymorphisms (SNPs) could alter enzyme activity. We evaluated SNPs in patients from Colombia in South America who were receiving tamoxifen treatment for breast cancer. Allelic diversity in the CYP2D6 gene was found in the studied population, with two patients displaying the poor-metaboliser phenotype. Molecular dynamics and trajectory analyses were performed for CYP2D6 from these two patients, comparing it with the common allelic form (CYP2D6*1). Although we found no significant structural change in the protein, its dynamics differ significantly from those of CYP2D6*1, the effect of such differential dynamics resulting in an inefficient enzyme with serious implications for tamoxifen-treated patients, increasing the risk of disease relapse and ineffective treatment.

Abstract P2-06-14: The role of SLC7A5 (LAT1) in endocrine therapy-resistant breast cancer

Abstract Endocrine therapies are commonly used to treat estrogen receptor-positive (ER+) breast cancers, which comprise 70% of all new breast cancer cases. Unfortunately, emergence of resistance to these therapies presents a major clinical challenge. Cancer cells can adapt to the dysregulation of cellular metabolism induced by endocrine therapy in order to evade cell death.Central to this adaptation is the scavenging of free-formed amino acids from the tumor microenvironment. For example, we found 109 solute carrier (SLC) mRNAs to be differentially expressed between endocrine-sensitive and resistant cells. We began our mechanistic studies of these genes with SLC family 7 member 5 (SLC7A5 or LAT1). SLC7A5 is a key component of a transmembrane transporter, which can complex with CD98 and increase the uptake of large, neutral amino acids (such as leucine or tyrosine). We used a panel of endocrine therapy-resistant (LCC9) and sensitive (MCF7; LCC1) breast cancer cells. SLC7A5 expression was upregulated by estrogen in MCF7 and LCC1 cells; this induction was blocked by fulvestrant treatment. Basal expression of the SLC7A5 protein in the absence of estrogen was 2.75-fold higher in LCC9 cells compared with MCF7 cells; SLC7A5 mRNA expression was 71-fold higher. Fulvestrant treatment did not significantly alter SLC7A5 mRNA or protein expression in LCC9 cells. Inhibiting SLC7A5 function using either a pharmacological inhibitor (JPH203), or depleting expression using siRNA, led to significant suppression of LCC9 cell growth. Cell cycle analysis revealed that SLC7A5 depletion caused cells to accumulate in the G1-phase, with a concurrent reduction of cells in S-phase. In four publicly available datasets of ER+, tamoxifen treated breast cancer patients, high expression of SLC7A5 was significantly associated with poor relapse-free survival. This study uncovers a novel adaptive mechanism in endocrine therapy-resistant breast cancer cells that is facilitated by increased expression of SLC7A5, which enables them to supplement their increased metabolic needs and promoting cell growth. Blocking the functions of SLC7A5, perhaps in conjunction with inhibition of autophagy, may therefore offer a new avenue of potential therapeutic intervention against endocrine therapy-resistant breast cancers. Citation Format: Sevigny CM, Sengupta S, Luo Z, Jin L, Pearce D, Clarke R. The role of SLC7A5 (LAT1) in endocrine therapy-resistant breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-14.

TARBP2-Enhanced Resistance during Tamoxifen Treatment in Breast Cancer.

Tamoxifen is the most widely used hormone therapy in estrogen receptor-positive (ER+) breast cancer, which accounts for approximately 70% of all breast cancers. Although patients who receive tamoxifen therapy benefit with respect to an improved overall prognosis, resistance and cancer recurrence still occur and remain important clinical challenges. A recent study identified TAR (HIV-1) RNA binding protein 2 (TARBP2) as an oncogene that promotes breast cancer metastasis. In this study, we showed that TARBP2 is overexpressed in hormone therapy-resistant cells and breast cancer tissues, where it enhances tamoxifen resistance. Tamoxifen-induced TARBP2 expression results in the desensitization of ER+ breast cancer cells. Mechanistically, tamoxifen post-transcriptionally stabilizes TARBP2 protein through the downregulation of Merlin, a TARBP2-interacting protein known to enhance its proteasomal degradation. Tamoxifen-induced TARBP2 further stabilizes SOX2 protein to enhance desensitization of breast cancer cells to tamoxifen, while similar to TARBP2, its induction in cancer cells was also observed in metastatic tumor cells. Our results indicate that the TARBP2-SOX2 pathway is upregulated by tamoxifen-mediated Merlin downregulation, which subsequently induces tamoxifen resistance in ER+ breast cancer.

Tamoxifen treatment for male breast cancer and risk of thromboembolism: prospective cohort analysis

PurposeThromboembolism is a common adverse event in women treated with tamoxifen (TAM) for breast cancer. The risk in male breast cancer patients is poorly investigated. We aimed to examine the risk of thrombotic events after TAM in male breast cancer patients.Patients and methodsIn this prospective cohort study, 448 patients treated between May 2009 and July 2017 for male breast cancer (BC) were assessed for eligibility. Patients with follow-up shorter than 6 months were excluded. The cumulative risk of thromboembolism was evaluated.ResultsThe median follow-up was 47 months (range 6–101 months) with a median age of 69.4 years (range 27–89 years). Oestrogen receptor and progesterone receptor expression levels were observed in 98.3 and 94.9% of cases, respectively. During the follow-up period, thrombotic events were documented in 21 (11.9%) of 177 patients receiving TAM and in 1 (2.5%) of 41 patients who did not receive tamoxifen. The estimated incidence was 51.9 per 1000 person-years and 21.5 per 1000 person-years, respectively. Notably, the highest risk was identified in the first 18 months, where 81% of the observed thrombotic events occurred. Patients aged older than 71 years had a significantly increased risk of thrombotic event under TAM treatment than their younger counterparts (p = 0.033). History of thrombotic event, cardiovascular and liver disease, as well as additional adjuvant treatment were not associated with increased thrombotic risk.ConclusionThe risk of thrombotic event in men treated with TAM for breast cancer is markedly increased in the first 18 months of treatment, and should be considered during treatment decisions.

A Sox2\u2013Sox9 signalling axis maintains human breast luminal progenitor and breast cancer stem cells

Increased cancer stem cell content during development of resistance to tamoxifen in breast cancer is driven by multiple signals, including Sox2-dependent activation of Wnt signalling. Here, we show that Sox2 increases and estrogen reduces the expression of the transcription factor Sox9. Gain and loss of function assays indicate that Sox9 is implicated in the maintenance of human breast luminal progenitor cells. CRISPR/Cas knockout of Sox9 reduces growth of tamoxifen-resistant breast tumours in vivo. Mechanistically, Sox9 acts downstream of Sox2 to control luminal progenitor cell content and is required for expression of the cancer stem cell marker ALDH1A3 and Wnt signalling activity. Sox9 is elevated in breast cancer patients after endocrine therapy failure. This new regulatory axis highlights the relevance of SOX family transcription factors as potential therapeutic targets in breast cancer.