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Background: The treatment landscape for HR(+)HER2(-) metastatic breast cancer (MBC) is evolving for patients with ESR1 mutations (mut) and PI3K/AKT pathway genomic alterations (GA). We sought to inform clinical utility for comprehensive genomic profiling (CGP) using tissue (TBx) and liquid biopsies (LBx) in HR(+)HER2(-) MBC., Methods: Records from a de-identified breast cancer clinicogenomic database for patients who underwent TBx/LBx testing at Foundation Medicine during routine clinical care at ~ 280 US cancer clinics between 01/2011 and 09/2023 were assessed. GA prevalence [ESR1mut, PIK3CAmut, AKT1mut, PTENmut, and PTEN homozygous copy loss (PTENloss)] were calculated in TBx and LBx [stratified by ctDNA tumor fraction (TF)] during the first three lines of therapy. Real-world progression-free survival (rwPFS) and overall survival (rwOS) were compared between groups by Cox models adjusted for prognostic factors., Results:  ~ 60% of cases harbored 1 + GA in 1st-line TBx (1266/2154) or LBx TF ≥ 1% (80/126) and 26.5% (43/162) in LBx TF < 1%. ESR1mut was found in 8.1% TBx, 17.5% LBx TF ≥ 1%, and 4.9% LBx TF < 1% in 1st line, increasing to 59% in 3rd line (LBx TF ≥ 1%). PTENloss was detected at higher rates in TBx (4.3%) than LBx (1% in TF ≥ 1%). Patients receiving 1st-line aromatase inhibitor + CDK4/6 inhibitor (n = 573) with ESR1mut had less favorable rwPFS and rwOS versus ESR1 wild-type; no differences were observed for fulvestrant + CDK4/6 inhibitor (n = 348)., Conclusion: Our study suggests obtaining TBx for CGP at time of de novo/recurrent diagnosis, followed by LBx for detecting acquired GA in 2nd + lines. Reflex TBx should be considered when ctDNA TF < 1%., (© 2024. The Author(s).)

Purpose: Hotspot estrogen receptor alpha (ER/ESR1) mutations are recognized as the driver for both endocrine resistance and metastasis in advanced ER-positive (ER+) breast cancer, but their contributions to metastatic organ tropism remain insufficiently understood. In this study, we aim to comprehensively profile the organotropic metastatic pattern for ESR1 mutant breast cancer., Methods: The organ-specific metastatic pattern of ESR1 mutant breast cancer was delineated using multi-omics data from multiple publicly available cohorts of ER+ metastatic breast cancer patients. Gene mutation/copy number variation (CNV) and differential gene expression analyses were performed to identify the genomic and transcriptomic alterations uniquely associated with ESR1 mutant liver metastasis. Upstream regulator, downstream pathway, and immune infiltration analysis were conducted for subsequent mechanistic investigations., Results: ESR1 mutation-driven liver tropism was revealed by significant differences, encompassing a higher prevalence of liver metastasis in patients with ESR1 mutant breast cancer and an enrichment of mutations in liver metastatic samples. The significant enrichment of AGO2 copy number amplifications (CNAs) and multiple gene expression changes were revealed uniquely in ESR1 mutant liver metastasis. We also unveiled alterations in downstream signaling pathways and immune infiltration, particularly an enrichment of neutrophils, suggesting potential therapeutic vulnerabilities., Conclusion: Our data provide a comprehensive characterization of the behaviors and mechanisms of ESR1 mutant liver metastasis, paving the way for the development of personalized therapy to target liver metastasis for patients with ESR1 mutant breast cancer., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Breast cancer (BC) accounts for roughly 30% of new cancers diagnosed in women each year; thus, this cancer type represents a substantial burden for people and health care systems. Despite the existence of effective therapies to treat BC, drug resistance remains a problem and is a major cause of treatment failure. Therefore, new drugs and treatment regimens are urgently required to overcome resistance. Recent research indicates that inhibition of the endosomal recycling pathway, an intracellular membrane trafficking pathway that returns endocytosed proteins back to the plasma membrane, may be a promising strategy to downregulate clinically relevant cell surface proteins such as HER2 and HER3, and to overcome drug resistance., Methods: To investigate the molecular mechanism of action of an endosomal recycling inhibitor (ERI) called primaquine, we performed a reverse-phase protein array (RPPA) assay using a HER2-positive breast cancer cell line. The RPPA findings were confirmed by Western blot and RT-qPCR in several BC cell lines. Novel drug combinations were tested by MTT cell viability and clonogenic assays., Results: Among the signalling molecules downregulated by ERIs were estrogen receptor-alpha (ER-α) and androgen receptor. We confirmed this finding in other breast cancer cell lines and show that downregulation occurs at the transcriptional level. We also found that ERIs synergise with tamoxifen, a standard-of-care therapy for breast cancer., Discussion: Our data suggest that combining ERIs with hormone receptor antagonists may enhance their efficacy and reduce the emergence of drug resistance., (© 2024. The Author(s).)

Purpose: Estrogen Receptor α (ERα) is a well-established therapeutic target for Estrogen Receptor (ER)-positive breast cancers. Both Selective Estrogen Receptor Degraders (SERD) and PROTAC ER degraders are synthetic compounds suppressing the ER activity through the degradation of ER. However, the differences between SERD and PROTAC ER degraders are far from clear., Methods: The effect of PROTAC ER degrader ERD-148 and SERD fulvestrant on protein degradation was evaluated by western blot analysis. The cell proliferation was tested by WST-8 assays and the gene expressions were assessed by gene microarray and real-time RT-PCR analysis after the compound treatment., Results: ERD-148 is a potent and selective PROTAC ERα degrader. It degrades not only unphosphorylated ERα but also the phosphorylated ERα in the cells. In contrast, the SERD fulvestrant showed much-reduced degradation potency on the phosphorylated ERα. The more complete degradation of ERα by ERD-148 translates into a greater maximum cell growth inhibition. However, ERD-148 and fulvestrant share a similar gene regulation profile except for the variation of regulation potency. Further studies indicate that ERD-148 degrades the ERα in fulvestrant-resistant cells., Conclusion: PROTAC ER degrader has a different mechanism of action compared to SERD which may be used in treating fulvestrant-resistant cancers., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: To investigate nuclear estrogen receptor α (ERα) and progesterone receptor (PR) immunohistochemistry (IHC) patterns in the stroma surrounding invasive carcinoma and assess associations with clinicopathologic features., Methods: A retrospective database search (1/2017-12/2020) identified breast core biopsies with invasive carcinoma. ERα/PR IHC expression in invasive carcinoma and stromal cells was categorized visually as positive (> 10%), low positive (1-10%) or negative (< 1%). Tumors were divided into 4 subtypes by IHC: Luminal, Luminal HER2, HER2 enriched, and triple negative. Clinicopathologic features associated (univariate p-value < 0.15) with ERα/PR stromal expression were investigated further using stepwise multivariable logistic regression., Results: Of 1512 biopsies, 1278 had accessible IHC. 55.6% (711/1278) and 10.4% (133/1274) of cases showed cancer-associated stromal fibroblast expression of ERα and PR, respectively. Stromal ER positivity was significantly associated with use of the Ventana (with SP1 clone) versus Leica (with 6F11 clone) platform and in cases with Luminal cancer subtype. PR stromal expression was significantly associated with Luminal subtype, obesity, and younger age., Conclusions: Expression of ERα and PR in breast cancer-associated stroma showed associations that suggest both biologic and analytic influence. Reproducible expression patterns may inform expansion of ERα/PR guidelines for the assessment of internal controls., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Estrogen receptor 1 (ESR1) mutations and fusions typically arise in patients with hormone receptor-positive breast cancer after aromatase inhibitor therapy, whereby ESR1 is constitutively activated in a ligand-independent manner. These variants can impact treatment response. Herein, we characterize ESR1 variants among molecularly profiled advanced breast cancers., Methods: DNA next-generation sequencing (592-gene panel) data from 9860 breast cancer samples were retrospectively reviewed. Gene fusions were detected using the ArcherDx fusion assay or whole transcriptome sequencing (n = 344 and n = 4305, respectively). Statistical analyses included Chi-square and Fisher's exact tests., Results: An ESR1 ligand-binding domain (LBD) mutation was detected in 8.6% of tumors evaluated and a pathogenic ESR1 fusion was detected in 1.6%. Most ESR1 LBD mutations/fusions were from estrogen receptor (ER)-positive samples (20.1% and 4.9%, respectively). The most common ESR1 LBD mutations included D538G (3.3%), Y537S (2.3%), and E380Q (1.1%) mutations. Among biopsy sites, ESR1 LBD mutations were most observed in liver metastases. Pathogenic ESR1 fusions were identified in 76 samples (1.6%) with 40 unique fusion partners. Evaluating co-alterations, ESR1 variant (mutation/fusion) samples more frequently expressed androgen receptor (78.0% vs 58.6, P < 0.0001) and less frequently immune checkpoint proteins than ESR1 wild-type (PD-1 20.0% vs 53.4, P < 0.05; immune cell PD-L1 10.0% vs 30.2, P < 0.0001)., Conclusion: We have described one of the largest series of ESR1 fusions reported. ESR1 LBD mutations were commonly identified in ER-positive disease. Limited data exists regarding the clinical impact of ESR1 fusions, which could be an area for future therapeutic exploration., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Currently, the most commonly applied method for the determination of breast cancer subtypes is to test estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki67 by immunohistochemistry (IHC). However, the IHC method has substantial intraobserver and interobserver variability. ESR1, PGR, ERBB2, and MKi67 mRNA tests by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay may improve the diagnostic objectivity and efficiency. Here, we compared the concordance between RT-qPCR and IHC for assessment of the same biomarkers and evaluated the subtypes., Methods: A total of 265 eligible cases were divided into a training cohort and a validation cohort, and the expressions of ER/ESR1, PR/PGR, HER2/ERBB2, and Ki67/MKI67 were tested by IHC and RT-qPCR. Then, the appropriate cutoff of RT-qPCR was calculated in the training cohort. The concordance between RT-qPCR and IHC was calculated for individual marker. In addition, we investigated the subtypes based on the RT-qPCR results., Results: The Spearman correlation coefficients between ER/ESR1, PR/PGR, HER2/ERBB2, and Ki67/MKI67 by IHC and RT-qPCR were 0.768, 0.699, 0.762, and 0.387, respectively. The cutoff values for the RT-qPCR assay of ESR1 (1%), PGR (1%), ERBB2, and MKi67 (14%) were 35.539, 32.139, 36.398, and 29.176, respectively. The overall percent agreement (OPA) between ER/ESR1, PR/PGR, HER2/ERBB2, and Ki67/MKI67 by IHC and RT-qPCR was 92.48%, 73.68%, 92.80%, and 74.44%, respectively. A total of 224 (84.53%) specimens were concordant for the breast cancer subtypes (IHC-based type) by RT-qPCR., Conclusion: Evaluation of breast cancer biomarker status by RT-qPCR was highly concordant with IHC. RT-qPCR can be used as a supplementary method to detect molecular markers of breast cancer., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Menin, encoded by the MEN1 gene, was recently reported to be involved in breast cancers, though the underlying mechanisms remain elusive. In the current study, we sought to further determine its role in mammary cells., Methods: Menin expression in mammary lesions from mammary-specific Men1 mutant mice was detected using immunofluorescence staining. RT-qPCR and western blot were performed to determine the role of menin in ERα expression in human breast cancer cell lines. ChIP-qPCR and reporter gene assays were carried out to dissect the action of menin on the proximal ESR1 promoter. Menin expression in female patients with breast cancer was analyzed and its correlation with breast cancer subtypes was investigated., Results: Immunofluorescence staining revealed that early mammary neoplasia in Men1 mutant mice displayed weak ERα expression. Furthermore, MEN1 silencing led to both reduced ESR1 mRNA and ERα protein expression in MCF7 and T47D cells. To further dissect the regulation of ESR1 transcription by menin, we examined whether and in which way menin could regulate the proximal ESR1 promoter, which has not been fully explored. Using ChIP analysis and reporter gene assays covering - 2500 bp to + 2000 bp of the TSS position, we showed that the activity of the proximal ESR1 promoter was markedly reduced upon menin downregulation independently of H3K4me3 status. Importantly, by analyzing the expression of menin in 354 human breast cancers, we found that a lower expression was associated with ER-negative breast cancer (P = 0.041). Moreover, among the 294 ER-positive breast cancer samples, reduced menin expression was not only associated with larger tumors (P = 0.01) and higher SBR grades (P = 0.005) but also with the luminal B-like breast cancer subtype (P = 0.006). Consistent with our clinical data, we demonstrated that GATA3 and FOXA1, co-factors in ESR1 regulation, interact physically with menin in MCF7 cells, and MEN1 knockdown led to altered protein expression of GATA3, the latter being a known marker of the luminal A subtype, in MCF7 cells., Conclusion: Taken together, our data provide clues to the important role of menin in ERα regulation and the formation of breast cancer subtypes., (© 2021. The Author(s).)

Purpose: Anterior gradient 3 (AGR3) is associated with breast cancer progression, but its relationship with estrogen and tamoxifen resistance in breast cancer is still unclear. This study was designed to investigate the correlation of ARG3 and estrogen as well as the roles of ARG3 in tamoxifen resistance in breast cancer., Methods: Online database including GEPIA, UALCAN, and TCGA and rVista predictive tool were applied to analyze the expression patterns of AGR3 and its relationship with estrogen receptor 1. AGR3 knockdown and overexpression cell models were constructed. Luciferase reporter assay and ChIP were performed to investigate intermolecular interactions. Western blotting and qPCR were applied to assess targets at mRNA and protein levels, respectively. Cell counting and MTT assay were applied to determine the cell proliferation., Results: An elevation of AGR3 was observed in patients with breast cancer, especially in the patients with estrogen receptor (ER)-positive breast cancer. The TCGA dataset and in vitro data supported that AGR3 was positively correlated to ER. Further results demonstrated that ER protein bound to AGR3 promoter sites. AGR3 expression exhibited a positive correlation to cell viability. Besides, AGR3 promoted tamoxifen resistance in breast cancer., Conclusion: AGR3 is associated with estrogen and promotes tamoxifen resistance in breast cancer., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Endocrine therapy (ET) is the mainstream adjuvant treatment for ER-positive breast cancer (BC). We analysed 9293 ER-positive BC patients diagnosed in nine European countries in 2009-2013 to investigate how comorbidities at diagnosis, age, stage and subtype affected ET use over time, and relapse., Methods: Adjusted odds ratios (ORs) and 95% confidence intervals (95%CIs) of receiving ET were estimated according to Charlson comorbidity, age, stage and subtype using logistic regression. The 2-year cumulative incidence and adjusted sub-hazard ratios (SHRs) of relapse were estimated using competing risk analysis, with all-cause death as the competing event. The z-test was used to assess differences in the proportion of patients receiving ET in 1996-1998 and 2009-2013., Results: Ninety percent of the patients started adjuvant ET, range 96% (Belgium, Estonia, Slovenia, Spain)-75% (Switzerland). ORs of starting ET were lower for women aged > 75 years, with severe comorbidities, or luminal B HER2-positive cancer. The factors independently increasing the risk of relapse were: not receiving ET (SHR 2.26, 95%CI 1.02-5.03); severe comorbidity (SHR 1.94, 95%CI 1.06-3.55); luminal B, either HER2 negative (SHR 3.06, 95%CI 1.61-5.79) or positive (SHR 3.10, 95%CI 1.36-7.07); stage II (SHR 3.20, 95%CI 1.56-6.57) or stage III (SHR 7.41, 95%CI 3.48-15.73). ET use increased significantly but differently across countries from 51-85% in 1996-1998 to 86-96% in 2009-2013., Conclusions: ER-positive BC patients in Europe are increasingly prescribed ET but between-country disparities persist. Older women and women with severe comorbidity less frequently receive ET. ET omission and severe comorbidity independently predict early disease relapse.

Background: Palbociclib is commonly added to an aromatase inhibitor (AI) as first-line therapy in ER + HER2- metastatic breast cancer (MBC). There are no data on the effect of the relative dose intensity (RDI) of palbociclib in first-line setting on clinical outcomes. The objective of this study is to explore the association of RDI and dose reduction of palbociclib in the first-line setting with PFS., Methods: This is a retrospective study of ER + HER2- MBC patients who received palbociclib plus AI in first-line setting. Subjects ≥ 18 years old with MBC, who were started on palbociclib 125 mg daily, had completed ≥ 1 cycle of palbociclib, and did not progress within the first 12 weeks were eligible. Analyses were performed at 12- and 36-week landmarks (LM). RDI was defined as the total amount of palbociclib taken per the total amount planned. RDI-high-12 and RDI-low-12 cohorts were defined as patients receiving palbociclib with RDI ≥ 80% and RDI < 80% during the first 12 weeks, respectively. Reduction-12 and No-reduction-12 cohorts were defined as patients who had any dose reduction and patients who had no reduction during the first 12 weeks, respectively., Results: 56 patients were eligible. Kaplan-Meier analysis from 12-week LM showed a median PFS of 17.1 months in RDI-high-12 versus 6.8 months in RDI-low-12 cohort (p = 0.0006). There was a 7.0-month improvement in median PFS in No-reduction-12 versus Reduction-12 cohort (p = 0.0638). Median PFS at 36-week LM was not reached in RDI-high-36 versus 8.6 months in RDI-low-36 cohort (p = 0.0703)., Conclusions: RDI < 80% of palbociclib during the first 12 weeks, when used in combination with an AI in first-line setting in ER + HER2- MBC, is associated with significantly shorter PFS compared to RDI ≥ 80%. There is a trend towards shorter PFS among patients with RDI < 80% versus RDI ≥ 80% at 36 weeks. A larger study is needed to validate these findings.

Purpose: To evaluate the cost-effectiveness of axillary observation versus sentinel lymph node biopsy (SLNB) after negative axillary ultrasound (AUS). In patients with clinical T1-T2 N0 breast cancer and negative AUS, SLNB is the current standard of care for axillary staging. However, SLNB is costly, invasive, decreasing in importance for medical decision-making, and is not considered therapeutic. Observation alone is currently being evaluated in randomized clinical trials, and is thought to be non-inferior to SLNB for patients with negative AUS., Methods: We performed cost-effectiveness analyses of observation versus SLNB after negative AUS in postmenopausal women with clinical T1-T2 N0, HR + /HER2 - breast cancer. Costs at the 2016 price level were evaluated from a third-party commercial payer perspective using the MarketScan® Database. We compared cost, quality-adjusted life years (QALYs), and net monetary benefit (NMB). Multiple sensitivity analyses varying baseline probabilities, costs, utilities, and willingness-to-pay thresholds were performed., Results: Observation was superior to SLNB for patients with N0 and N1 disease, and for the entire patient population (NMB in US$: $655,659 for observation versus $641,778 for SLNB for the entire patient population). In the N0 and N1 groups, observation incurred lower cost and was associated with greater QALYs. SLNB was superior for patients with > 3 positive lymph nodes, representing approximately 5% of the population. Sensitivity analyses consistently demonstrated that observation is the optimal strategy for AUS-negative patients., Conclusion: Considering both cost and effectiveness, observation is superior to SLNB in postmenopausal women with cT1-T2 N0, HR + /HER2 - breast cancer and negative AUS.

Purpose: Approximately 70% of patients with metastatic breast cancer (MBC) are hormone receptor (HR)-positive. Recent studies have shown that CDK4/6 inhibitors (CDKI) improve survival in combination with ET in HR-positive, HER2-negative MBC. The risk of venous thromboembolism (VTE) is 3-4 times higher in patients with breast cancer (BC) than in patients without cancer. The risk is even higher in BC patients receiving ET and chemotherapy. The aim of the study was to determine the VTE risk of CDKIs plus ET versus ET alone in patients with HR-positive, HER2-negative MBC., Methods: We performed a systematic review and meta-analysis to demonstrate the risk of VTE in patients with HR-positive HER2-negative MBC treated with combined CDKIs and ET versus ET alone., Results: Eight randomized controlled trials (RCT) with a total of 4,557 patients were eligible. The study arms comprised of palbociclib or ribociclib or abemaciclib plus ET while the control arms utilized placebo plus ET. The VTE events were 56 (2%) in the CDKIs plus ET group compared to 10 (0.5%) in the control group. Pooled relative risk (RR) for VTE was 2.62 (95% CI 1.21-5.65; P = 0.01) and the risk difference (RD) was 0.01 (95% CI 0.00-0.03; P = 0.02). Over a median follow-up of up to 36 months, RR was 3.18 (95% CI 1.22-8.24; P = 0.02) and RD was 0.03 (95% CI 0.01-0.06, P = 0.008)., Conclusions: Our meta-analyses demonstrated that the addition of CDKIs to ET in patients with HR-positive HER 2-negative MBC contribute to a higher incidence of VTE. Further trials are required to define the actual relation and definitive incidence of VTE with different CDKIs.

Purpose: Palbociclib is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, approved in combination with endocrine therapy for the treatment of women and men with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer (HR+/HER2- ABC). In the phase 2, open-label, PALOMA-1 trial, palbociclib plus letrozole significantly prolonged progression-free survival (PFS) versus letrozole alone (hazard ratio, 0.488; 95% CI 0.319‒0.748; P = 0.0004; median PFS, 20.2 vs 10.2 months, respectively) in postmenopausal women with estrogen receptor-positive (ER+)/HER2- ABC. Here, we present the final overall survival (OS) and updated safety results., Methods: Postmenopausal women with ER+/HER2- ABC were randomized 1:1 to receive either palbociclib (125 mg/day, 3/1 schedule) plus letrozole (2.5 mg/day, continuous) or letrozole alone (2.5 mg/day, continuous). The primary endpoint was investigator-assessed PFS; secondary endpoints included OS and safety., Results: A total of 165 patients were randomized. At the data cutoff date of December 30, 2016 (median duration of follow-up, 64.7 months), the stratified hazard ratio for OS was 0.897 (95% CI 0.623-1.294; P = 0.281); median OS in the palbociclib plus letrozole and letrozole alone arms was 37.5 and 34.5 months, respectively. The median time from randomization to first subsequent chemotherapy use was longer with palbociclib plus letrozole than letrozole alone (26.7 and 17.7 months, respectively). The most frequently reported adverse event in the palbociclib plus letrozole arm was neutropenia (any grade, 75%; grade 3 or 4, 59%)., Conclusions: Palbociclib plus letrozole treatment led to a numerical but not statistically significant improvement in median OS. Pfizer Inc (NCT00721409).

Purpose: The last fifteen years has seen a rising proportion of women who are eligible for breast conserving therapy (BCT) choosing mastectomy despite equivalent survival in early-stage breast cancer. We aim to explore potential racial differences in the association of surgical choice with subsequent patient-reported satisfaction outcomes., Methods: Women who were within one year of diagnosis with hormone receptor (HR)-positive breast cancer were asked the Short Version of Patient Satisfaction Questionnaire (PSQ-18), which assesses their overall satisfaction with their medical care. We conducted bivariate analyses, including paired t-tests, to clarify differences in these patient-reported factors by surgical choice and race. Multivariable linear regression models were used to adjust for clinical and demographic control variables., Results: For the sample of 279 women who underwent definitive surgery, women who received a mastectomy had lower levels of overall satisfaction, 71 vs. 75 (out of 90) (p = .001). In stratifying this relationship by race, the difference in total satisfaction score was largest among Black women (69 among mastectomy patients vs. 75 among BCT patients; p = 0.016). On multivariable linear regression, Black race and mastectomy status (together) exhibited a significantly large negative association with total satisfaction score, with negative associations across all domains of the PSQ-18., Conclusion: Despite the high prevalence of mastectomy among Black women with early-stage, HR-positive breast cancer, this population is more likely to report lower levels of patient satisfaction compared to patients receiving BCT. These findings suggest there may be potential racial differences in the psychosocial consequences of surgical choice.

Purpose: The prognostic role of tumor-infiltrating lymphocytes (TILs) in ER+/HER2- breast cancer (BC) is debated. We evaluated the association of TILs and clinico-pathological features with distant disease-free survival (DDFS) in patients with ER+/HER2- BC treated at a single institution., Patients and Methods: A mono-institutional case-cohort series of 987 patients with early ER+/HER2- BC was retrospectively analyzed. TILs were considered both as continuous variable, and dichotomized in low (< 5%) vs high (≥ 5%). The main outcome was DDFS. Median follow-up was 7.5 years (0.1-10). Univariate and multivariable Cox proportional hazards regression with inverse sub-cohort sampling probability weighting were used to evaluate the risk across groups., Results: Median TIL count was 2% (Q1-Q3 1-4%). Higher TILs were positively associated with number of lymph nodes involved (p = 0.003), tumor grade (p < 0.0001), peritumoral vascular invasion (p = 0.003), higher Ki-67 (p = 0.0001), luminal B subtype (p < 0.0001), and chemotherapy use (p < 0.00019). In multivariable regression analysis, only higher Ki-67 expression retained significant association with TILs. At univariate Cox regression analysis, TIL expression (≥ 5% vs. < 5%) was not associated with DDFS (HR 1.08, 95% CI 0.80-1.46, p = 0.62). In patients treated with adjuvant chemotherapy, high TILs were associated with better DDFS (HR 0.52, 95%CI 0.33-0.83, p = 0.006), particularly in the group with Ki-67 ≥ 20% (HR 0.50, 95%CI 0.29-0.86, p = 0.01)., Conclusion: High TILs in ER+/HER2- BC are significantly associated with clinico-pathological features of dismal outcome. TIL prognostic value seems different in patients treated with or without chemotherapy. Our findings suggest that the high-risk subgroup might be more immunogenic, thus deserving the exploration of immunotherapy approaches.

Purpose: Studies have identified several estrogen receptor α (ERα) ligand-binding domain (LBD) somatic mutations in endocrine therapy resistant, metastatic ER-positive breast cancers. The most common mutations, Tyr537Ser (Y537S) and Asp538Gly (D538G), are detected in ~ 30% of endocrine resistant metastatic breast cancer patients. These ESR1 mutations induce the agonist conformation of ERα, confer an estrogen-independent phenotype, and promote drug resistance to antiestrogens., Methods: ER-positive, estrogen-dependent MCF-7 cells were engineered to express either the Y537S or D538G mutants using CRISPR knock-in (cY537S and cD538G). These cells were used to screen several estrogen receptor degrader (ERD) compounds synthesized using the Proteolysis Targeting Chimeras (PROTAC) method to induce degradation of ERα via the ubiquitin-proteasome pathway., Results: Wild-type MCF-7 and ERα LBD mutant cells were treated with ERD-148 (10 pM-1 µM) and assayed for cellular proliferation using the PrestoBlue cell viability assay. ERD-148 attenuated ER-dependent growth with IC 50 values of 0.8, 10.5, and 6.1 nM in MCF-7, cY537S, and cD538G cells, respectively. Western blot analysis showed that MCF-7 cells treated with 1 nM ERD-148 for 24 h exhibited reduced ERα protein expression as compared to the mutants. The ER-regulated gene, GREB1, demonstrated significant downregulation in parental and mutant cells after 24 h of ERD-148 treatment at 10 nM. Growth of the ER-negative, estrogen-independent MDA-MB-231 breast cancer cells was not inhibited by ERD-148 at the ~ IC 90 observed in the ER-positive cells., Conclusion: ERD-148 inhibits the growth of ER-positive breast cancer cells via downregulating ERα with comparable potency to Fulvestrant with marginal non-specific toxicity.

Objective: To comprehensively describe the tumor and clinical characteristics of breast cancer in a cohort of male patients and to assess the factors that affect survival., Background: Much of the standard care of male breast cancer is based on the diagnosis and treatment strategies of female breast cancer. However, important clinical differences between the two have been elucidated, which suggests the need for unique attention to male breast cancer., Methods: We evaluated the records of male patients who were diagnosed with breast cancer between 2004 and 2015 using the National Cancer Database (NCDB). Data obtained were demographic characteristics, clinical and tumor data, type of therapy, as well as survival data. We used descriptive statistics to characterize our study population. We then performed a survival and Cox proportional hazards analysis., Results: We identified 16,498 patients (median age: 63 years). Several treatment modalities were used, of which surgery was the most common (14,882 [90.4%]). The total follow-up time was 13 years (156 months). Five-year survival was 77.7% (95% CI 76.9-78.4) and 10-year survival was 60.7%. In a Cox proportional hazards model, mastectomy was associated with the greatest survival (hazard ratio [HR] 0.49; p < 0.001)., Conclusion: We report what is to our knowledge the largest national population-based cohort of male breast cancer patients. Importantly, our data suggests that similar to female patients, several treatment modalities are significantly associated with improved survival in male patients, particularly surgery. Increasing age, black race, government insurance, more comorbidities, and higher tumor stages are associated with decreased survival.

Purpose: The effect of human epidermal growth factor receptor 2 (HER2) status on mucinous carcinoma (MC) of the breast is unknown due to the rarity of HER2-positive cases. We evaluated the prognostic value of HER2 status and the efficacy of anti-HER2 therapy in patients with hormone receptor (HR)-positive MC., Methods: From the data of 154,661 patients recorded in the Korean Breast Cancer Registry between January 1990 and August 2016, 3076 (2.0%) were diagnosed with MC. Overall survival (OS) according to HER2 status and anti-HER2 therapy was analyzed using Kaplan-Meier estimates. Multivariate analysis was performed using the Cox proportional hazards model to estimate the adjusted hazards ratio (HR) for clinicopathologic factors., Results: A total of 2716 HR-positive MC patients were enrolled and followed up for a median 100.1 months. Of these, 2094 (77.1%) were HER2-negative and 228 (8.4%) were HER2-positive. HR-positive, HER2-positive MC patients had more advanced pathologic tumor stages (T3 or T4) (p = 0.001), more axillary lymph node involvement (p < 0.001), higher nuclear grade (p < 0.001), and more lymphovascular invasion (p = 0.012) than HER2-negative patients. Subgroup analysis of HR-positive, node-positive MC showed that HER2-positive MC was an independent prognostic factor for OS (HR = 2.657; 95% CI, 1.665-4.241; p < 0.001). HR-positive, node-positive, and HER2-negative MC had significantly longer OS than HER2-positive MBC (p = 0.017). The node-positive subgroup that received anti-HER2 therapy had increased OS, although not significantly (p = 0.224)., Conclusion: Our nationwide database study revealed that HER2-positive status was associated with worse prognosis in HR-positive and node-positive MC. Anti-HER2 therapy might be beneficial in HR-positive, node-positive, and HER2-positive MC.

Purpose: Studies of Black-White differences in breast cancer subtype often emphasize potential ancestry-associated genetic or lifestyle risk factors without fully considering how the social or economic implications of race in the U.S. may influence risk. We assess whether neighborhood racial composition and/or socioeconomic status are associated with odds of triple-negative breast cancer (TNBC) diagnosis relative to the less-aggressive hormone receptor-positive/HER2-negative subtype (HR+ /HER-), and whether the observed relationships vary across women's race and age groups., Methods: We use multilevel generalized estimating equation models to evaluate odds of TNBC vs. HR+ /HER2- subtypes in a population-based cohort of 7291 Black and 74,208 White women diagnosed with breast cancer from 2006 to 2014. Final models include both neighborhood-level variables, adjusting for individual demographics and tumor characteristics., Results: Relative to the HR+ /HER- subtype, we found modestly lower odds of TNBC subtype among White women with higher neighborhood median household income (statistically significant within the 45-64 age group, OR = 0.981 per $10,000 increase). Among Black women, both higher neighborhood income and higher percentages of Black neighborhood residents were associated with lower odds of TNBC relative to HR+ /HER2-. The largest reduction was observed among Black women diagnosed at age ≥ 65 (OR = 0.938 per $10,000 increase; OR = 0.942 per 10% increase in Black residents)., Conclusion: The relationships between neighborhood composition, neighborhood socioeconomic status, and odds of TNBC differ by race and age. Racially patterned social factors warrant further exploration in breast cancer subtype disparities research.

Purpose: The serine-threonine kinases Aurora A (AURKA) and p21-activated kinase 1 (PAK1) are frequently overexpressed in breast tumors, with overexpression promoting aggressive breast cancer phenotypes and poor clinical outcomes. Besides the well-defined roles of these proteins in control of cell division, proliferation, and invasion, both kinases support MAPK kinase pathway activation and can contribute to endocrine resistance by phosphorylating estrogen receptor alpha (ERα). PAK1 directly phosphorylates AURKA and its functional partners, suggesting potential value of inhibiting both kinases activity in tumors overexpressing PAK1 and/or AURKA. Here, for the first time, we evaluated the effect of combining the AURKA inhibitor alisertib and the PAK inhibitor FRAX1036 in preclinical models of breast cancer., Methods: Combination of alisertib and FRAX1036 was evaluated in a panel of 13 human breast tumor cell lines and BT474 xenograft model, with assessment of the cell cycle by FACS, and signaling changes by immunohistochemistry and Western blot. Additionally, we performed in silico analysis to identify markers of response to alisertib and FRAX1036., Results: Pharmacological inhibition of AURKA and PAK1 synergistically decreased survival of multiple tumor cell lines, showing particular effectiveness in luminal and HER2-enriched models, and inhibited growth and ERα-driven signaling in a BT474 xenograft model. In silico analysis suggested cell lines with dependence on AURKA are most likely to be sensitive to PAK1 inhibition., Conclusion: Dual targeting of AURKA and PAK1 may be a promising therapeutic strategy for treatment of breast cancer, with a particular effectiveness in luminal and HER2-enriched tumor subtypes.

Purpose: In early stage, ERα-positive breast cancer, concurrent use of endocrine therapy and chemotherapy has not been shown to be superior to sequential use. We hypothesized that genetic biomarkers can aid in selecting patients who would benefit from chemo-endocrine therapy. Our previous studies revealed that ZNF423 is a transcription factor for BRCA1 and an intronic single nucleotide polymorphism (SNP) in ZNF423, rs9940645, determines tamoxifen response. Here, we identified mitosis-related genes that are regulated by ZNF423 which led us to investigate taxane response in a rs9940645 SNP- and tamoxifen-dependent fashion., Methods: The Cancer Genome Atlas (TCGA) breast cancer dataset was used to identify genes correlated with ZNF423. Quantitative reverse transcription PCR, chromatin immunoprecipitation, and luciferase reporter assays were used to validate the gene regulation. We used CRISPR/Cas9 to engineer paired ZR-75-1 cells which differ only in ZNF423 rs9940645 SNP genotype to test SNP-dependent phenotypes including cell cycle and cell viability. We validated our findings in an additional two breast cancer cell lines, Hs578T-ERα and HCC1500., Results: Mitosis-related genes VRK1 and PBK, which encode histone H3 kinases, were experimentally validated to be regulated by ZNF423. ZNF423 knockdown decreased VRK1 and PBK expression and activity. Additionally, ZNF423 knockdown enhanced docetaxel-induced G2/M arrest and cytotoxicity through VRK1 or PBK regulation. Lastly, cells carrying the rs9940645 variant genotype had increased G2/M arrest and decreased cell viability when treated with docetaxel in combination with estradiol and 4-OH-TAM., Conclusions: We identified ZNF423 regulated genes involved in the G2/M phase of the cell cycle. 4-OH-TAM sensitized ERα-positive breast cancer cells to docetaxel in a ZNF423 SNP-dependent manner. Our findings suggest that patients with rs9940645 variant genotype may benefit from concurrent tamoxifen and docetaxel. This would impact a substantial proportion of patients because this SNP has a minor allele frequency of 0.47.

Purpose: Estrogen receptor-alpha (ER) is a therapeutic target of ER-positive (ER+) breast cancers. Although ER signaling is complex, many mediators of this pathway have been identified. Specifically, phosphorylation of ER at serine 118 affects responses to estrogen and therapeutic ligands and has been correlated with clinical outcomes in ER+ breast cancer patients. We hypothesized that a newly described germline variant (S118P) at this residue would drive cellular changes consistent with breast cancer development and/or hormone resistance., Methods: Isogenic human breast epithelial cell line models harboring ER S118P were developed via genome editing and characterized to determine the functional effects of this variant. We also examined the frequency of ER S118P in a case-control study (N = 536) of women with and without breast cancer with a familial risk., Results: In heterozygous knock-in models, the S118P variant demonstrated no significant change in proliferation, migration, MAP Kinase pathway signaling, or response to the endocrine therapies tamoxifen and fulvestrant. Further, there was no difference in the prevalence of S118P between women with and without cancer relative to population registry databases., Conclusions: This study suggests that the ER S118P variant does not affect risk for breast cancer or hormone therapy resistance. Germline screening and modification of treatments for patients harboring this variant are likely not warranted.

Purpose: Deregulated PI3K/mTOR signals can promote the growth of breast cancer and contribute to endocrine treatment resistance. This report aims to investigate raptor and its intracellular localization to further understand its role in ER-positive breast cancer., Methods: Raptor protein expression was evaluated by immunohistochemistry in 756 primary breast tumors from postmenopausal patients randomized to tamoxifen or no tamoxifen. In vitro, the MCF7 breast cancer cell line and tamoxifen-resistant MCF7 cells were studied to track the raptor signaling changes upon resistance, and raptor localization in ERα-positive cell lines was compared with that in ERα-negative cell lines., Results: Raptor protein expression in the nucleus was high in ER/PgR-positive and HER2-negative tumors with low grade, features associated with the luminal A subtype. Presence of raptor in the nucleus was connected with ERα signaling, here shown by a coupled increase of ERα phosphorylation at S167 and S305 with accumulation of nuclear raptor. In addition, the expression of ERα-activated gene products correlated with nuclear raptor. Similarly, in vitro we observed raptor in the nucleus of ERα-positive, but not of ER-negative cells. Interestingly, raptor localized to the nucleus could still be seen in tamoxifen-resistant MCF7 cells. The clinical benefit from tamoxifen was inversely associated with an increase of nuclear raptor. High cytoplasmic raptor expression indicated worse prognosis on long-term follow-up., Conclusion: We present a connection between raptor localization to the nucleus and ERα-positive breast cancer, suggesting raptor as a player in stimulating the growth of the luminal A subtype and a possible target along with endocrine treatment.

Purpose: Breast cancers have a poorer prognosis if estrogen receptor expression was lost during recurrence. It is unclear whether this conversion is cell autonomous or whether it can be promoted by the microenvironment during cancer dormancy. We explored the ability of marrow-derived stromal cell lines to arrest co-cultured breast cancer cells and suppress estrogen receptor alpha (ER) expression during arrest, facilitating the emergence of estrogen-independent breast cancer clones., Methods: Cancer cell growth, ER protein, microRNA, and mRNA levels were measured in breast cancer cell lines exposed to conditioned medium from marrow stromal lines in the presence and absence of estrogen and of signaling pathway modulators., Results: We demonstrate that paracrine signaling from the stromal cell line HS5 downregulated ER in T47D and MCF7 breast cancer cells. This occurred at the mRNA level and also through decreased ER protein stability. Additionally, conditioned medium (CM) from HS5 arrested the breast cancer cells in G0/G1 in part through interleukin-1 (IL1) and inhibited cancer cell growth despite the activation of proliferative pathways (Erk and AKT) by the CM. Similar findings were observed for CM from the hFOB 1.19 osteoblastic cell line but not from two other fibroblastic marrow lines, HS27A and KM101. HS5-CM inhibition of MCF7 proliferation could not be restored by exogenous ER, but was restored by the IL1-antagonist IL1RA. In the presence of IL1RA, HS5-CM activation of AKT and Erk enabled the outgrowth of breast cancer cells with suppressed ER that were fulvestrant-resistant and estrogen-independent., Conclusions: We conclude that marrow-derived stromal cells can destabilize estrogen receptor protein to convert the ER status of growth-arrested ER+ breast cancer cell lines. The balance between stromal pro- and anti-proliferative signals controlled the switch from a dormant phenotype to estrogen-independent cancer cell growth.

Gametogenetin-binding protein 2 (GGNBP2) is encoded in human chromosome 17q12-q23, a region known as a breast and ovarian cancer susceptibility locus. GGNBP2, also referred to ZFP403, has a single C2H2 zinc finger and a consensus LxxLL nuclear receptor-binding motif. Here, we demonstrate that GGNBP2 expression is reduced in primary human breast tumors and in breast cancer cell lines, including T47D, MCF-7, LCC9, LY2, and MDA-MB-231 compared with normal, immortalized estrogen receptor α (ERα) negative MCF-10A and MCF10F breast epithelial cells. Overexpression of GGNBP2 inhibits the proliferation of T47D and MCF-7 ERα positive breast cancer cells without affecting MCF-10A and MCF10F. Stable GGNBP2 overexpression in T47D cells inhibits 17β-estradiol (E2)-stimulated proliferation as well as migration, invasion, anchorage-independent growth in vitro, and xenograft tumor growth in mice. We further demonstrate that GGNBP2 protein physically interacts with ERα, inhibits E2-induced activation of estrogen response element-driven reporter activity, and attenuates ER target gene expression in T47D cells. In summary, our in vitro and in vivo findings suggest that GGNBP2 is a novel breast cancer tumor suppressor functioning as a nuclear receptor corepressor to inhibit ERα activity and tumorigenesis.

The biological subtype of breast cancer influences the selection of systemic therapy. Distinction between luminal A and B cancers depends on consistent assessment of Ki-67, but substantial intra-observer and inter-observer variability exists when immunohistochemistry (IHC) is used. We compared RT-qPCR with IHC in the assessment of Ki-67 and other standard factors used in breast cancer subtyping. RNA was extracted from archival breast tumour tissue of 769 women randomly assigned to the FinHer trial. Cancer ESR1, PGR, ERBB2 and MKI67 mRNA content was quantitated with an RT-qPCR assay. Local pathologists assessed ER, PgR and Ki-67 expression using IHC. HER2 amplification was identified with chromogenic in situ hybridization (CISH) centrally. The results were correlated with distant disease-free survival (DDFS) and overall survival (OS). qPCR-based and IHC-based assessments of ER and PgR showed good concordance. Both low tumour MKI67 mRNA (RT-qPCR) and Ki-67 protein (IHC) levels were prognostic for favourable DDFS [hazard ratio (HR) 0.42, 95 % CI 0.25-0.71, P = 0.001; and HR 0.56, 0.37-0.84, P = 0.005, respectively] and OS. In multivariable analyses, cancer MKI67 mRNA content had independent influence on DDFS (adjusted HR 0.51, 95 % CI 0.29-0.89, P = 0.019) while Ki-67 protein expression had not any influence (P = 0.266) whereas both assessments influenced independently OS. Luminal B patients treated with docetaxel-FEC had more favourable DDFS and OS than those treated with vinorelbine-FEC when the subtype was defined by RT-qPCR (for DDFS, HR 0.52, 95 % CI 0.29-0.94, P = 0.031), but not when defined using IHC. Breast cancer subtypes approximated with RT-qPCR and IHC show good concordance, but cancer MKI67 mRNA content correlated slightly better with DDFS than Ki-67 expression. The findings based on MKI67 mRNA content suggest that patients with luminal B cancer benefit more from docetaxel-FEC than from vinorelbine-FEC.

Tamoxifen (Tam) resistance represents a significant clinical problem in estrogen receptor (ER) α-positive breast cancer. We previously showed that decreased expression of Rho guanine nucleotide dissociation inhibitor (Rho GDI) α, a negative regulator of the Rho GTPase pathway, is associated with Tam resistance. We now discover that androgen receptor (AR) is overexpressed in cells with decreased Rho GDIα and seek to determine AR's contribution to resistance. We engineered ERα-positive cell lines with stable knockdown (KD) of Rho GDIα (KD cells). Resistance mechanisms were examined using microarray profiling, protein-interaction studies, growth and reporter gene assays, and Western blot analysis combined with a specific AR antagonist and other signaling inhibitors. Tam-resistant tumors and cell lines with low Rho GDIα levels exhibited upregulated AR expression. Microarray of Rho GDIα KD cells indicated that activation of EGFR and ERα was associated with Tam treatment. When AR levels were elevated, interaction between AR and EGFR was detected. Constitutive and Tam-induced phosphorylation of EGFR and ERK1/2 was blocked by the AR antagonist Enzalutamide, suggesting that AR-mediated EGFR activation was a mechanism of resistance in these cells. Constitutive ERα phosphorylation and transcriptional activity was inhibited by Enzalutamide and the EGFR inhibitor gefitinib, demonstrating that AR-mediated EGFR signaling activated ERα. Tam exhibited agonist activity in AR overexpressing cells, stimulating ERα transcriptional activity and proliferation, which was blocked by Enzalutamide and gefitinib. We describe a novel model of AR-mediated Tam resistance through activation of EGFR signaling leading to ER activation in ERα-positive cells with low expression of Rho GDIα.

Recurrence and death in a significant number of patients with ERα-positive breast cancer occurs 10-20 years after diagnosis. Prognostic markers for late events have been more elusive. TFAP2C (AP2γ) regulates the expression of ERα, the ERα pioneer factors FOXA1 and GATA3, and controls ERα-dependent transcription. The purpose of this investigation is to determine the long-term prognostic value of TFAP2C. A tissue microarray (TMA) consisting of breast tumors from 451 patients with median follow-up time of 10.3 years was created and tested for the expression of TFAP2C by immunohistochemistry. Wilcoxon Rank-Sum and Kruskal-Wallis tests were used to determine if TFAP2C H-scores correlate with other tumor markers. Cox proportional hazards regression models were used to determine whether TFAP2C H-scores and other tumor markers were related to overall and disease-free survival in univariate and multivariable models. TFPAC2 overexpression did not impact overall survival during the first 10 years after diagnosis, but was associated with a shorter survival after 10 years (HR 3.40, 95 % CI 1.58, 7.30; p value = 0.002). This late divergence persisted in ER-positive (HR 2.86, 95 % CI 1.29, 6.36; p value = 0.01) and endocrine therapy-positive subgroups (HR 4.19, 95 % CI 1.72, 10.23; p value = 0.002). For the ER+ and endocrine therapy subgroup, the HR was 3.82 (95 % CI 1.53, 9.50; p value = 0.004). TFAP2C H-scores were not correlated with other tumor markers or related to disease-free survival. In this hypothesis-generating study, we show that higher TFAP2C scores correlate with poor overall survival after 10 years of diagnosis in ERα-positive and endocrine therapy-treated subgroups.

Breast cancer is a heterogeneous entity composed of distinct molecular subgroups with different molecular and clinical features. We analyzed the association between molecular breast cancer subgroups, age at diagnosis, and prognosis in a compilation of publicly available gene expression datasets. Affymetrix gene expression data (U133A or U133Plus2.0 arrays) of 4467 breast cancers from 40 datasets were compiled and homogenized. Breast cancer subgroups were defined based on expression of ESR1, PR, HER2, and Ki67. Event-free survival was calculated as recurrence-free survival or distant metastasis-free survival if recurrence-free survival was not available. Young age at diagnosis is associated with higher frequency of triple negative and HER2 subtypes and lower frequency of luminal A breast cancers. The 5-year event-free survival rates of patients aged less than 40, between 40 and 50, and >50 years were 54.3 ± 3.5, 68.5 ± 1.9, and 70.4 ± 1.3 %, respectively. When controlling for breast cancer subtype, we found that age <40 years remained significantly associated with poor prognosis in triple negative breast cancer. The effect was modest in luminal tumors and not found in HER2 subtype. Both subtypes and age retained their significances in multivariate analysis. Association of age at diagnosis with molecular breast cancer subtype contributes to its important role as prognostic factor among patients with breast cancer. Still, within the group of triple negative breast cancer, young age <40 years has a significant prognostic value which was retained in multivariate analysis.

Mastopathy is a common disease of the breast likely associated with elevated estrogen levels and a putative risk factor for breast cancer. The role of estrogen receptor alpha (ESR1) in mastopathy has not been investigated previously. Here, we investigated the prevalence of ESR1 gene amplification in mastopathy and its prediction for breast cancer. Paraffin-embedded tissues from 58 women with invasive breast cancer were analyzed. For all women, tissues with mastopathy taken at least 1.5 years before first diagnosis of breast cancer were available. Tissue from 46 women with mastopathy without a diagnosis of breast carcinoma in the observed time frame (12-18 years) was used as control. Fluorescence in situ hybridization analysis revealed that ESR1 was amplified in nine of 58 (15.5 %) breast cancers. All ESR1-amplified breast cancers were strongly positive for estrogen receptor with ER immunohistochemistry. Interestingly, in women with ESR1 amplification in breast cancer, the amplification was detectable in mastopathic tissues prior to the first diagnosis of breast cancer but was absent in tissues from women with mastopathy who did not develop breast cancer. Our study suggests that ESR1 gene amplification is an early event in breast pathology and might be a helpful predictive marker to identify patients at high risk of developing breast cancer.

ER and HER2 are critical drivers of breast cancer biology and can interact when co-expressed, but less data describe the impact of ER/HER2 co-expression on clinical disease characteristics. We studied the impact of ER and HER2 (co)-expression in a cohort of 1,187 patients with invasive breast cancer and compared disease characteristics among different groups according to ER and HER2 status. Age, tumor size, grade, nodal status, TNM stage, and metastatic sites were compared and significance determined using the appropriate t tests. All p values were two-tailed. Compared to ER-negative/HER2-negative disease as the control group, ER expression was associated with older age, smaller tumors, lower grade, earlier TNM stage, and increased bone involvement in de novo metastasis, while HER2 had no significant impact on these characteristics. ER and HER2 co-expression was associated with lower grade and higher bone involvement in de novo metastasis, reflecting a retained impact for ER. HER2 impact on ER-positive disease was reflected by younger age, higher grade and TNM stage, and increased frequency of visceral involvement in de novo metastasis. Within the ER-positive/HER2-positive group, triple positive breast cancer (ER+/PgR+/HER2+) was associated with younger age compared to ER+/PgR-/HER2+ disease (mean age of 50.8 vs. 56 years, p = 0.0226). PgR was also associated with younger age in ER+/HER2- disease with a mean age of 57.6 years in ER+/PgR+/HER2- disease vs. 63.4 years in ER+/PgR-/HER2- disease (p < 0.0001). In conclusion, ER has a profound impact on breast cancer characteristics, including a retained impact when co-expressed with HER2. Similarly, HER2 dramatically modulates ER-positive breast cancer making it more aggressive. PgR association with young age may be related to hormonal levels of the premenopausal state, with HER2 providing an earlier growth advantage in triple positive disease, suggesting a specific dependence for this subset on high estrogen levels.

Breast cancers are categorized into three subtypes based on protein expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2/ERBB2). Patients enroll onto experimental clinical trials based on ER, PR, and HER2 status and, as receptor status is prognostic and defines treatment regimens, central receptor confirmation is critical for interpreting results from these trials. Patients enrolling onto experimental clinical trials in the metastatic setting often have limited available archival tissue that might better be used for comprehensive molecular profiling rather than slide-intensive reconfirmation of receptor status. We developed a Random Forests-based algorithm using a training set of 158 samples with centrally confirmed IHC status, and subsequently validated this algorithm on multiple test sets with known, locally determined IHC status. We observed a strong correlation between target mRNA expression and IHC assays for HER2 and ER, achieving an overall accuracy of 97 and 96%, respectively. For determining PR status, which had the highest discordance between central and local IHC, incorporation of expression of co-regulated genes in a multivariate approach added predictive value, outperforming the single, target gene approach by a 10% margin in overall accuracy. Our results suggest that multiplexed qRT-PCR profiling of ESR1, PGR, and ERBB2 mRNA, along with several other subtype associated genes, can effectively confirm breast cancer subtype, thereby conserving tumor sections and enabling additional biomarker data to be obtained from patients enrolled onto experimental clinical trials.

Androgen receptor (AR) is an attractive target in breast cancer because of its frequent expression in all the molecular subtypes, especially in estrogen receptor (ER)-positive luminal breast cancers. We have previously shown a role for AR overexpression in tamoxifen resistance. We engineered ER-positive MCF-7 cells to overexpress aromatase and AR (MCF-7 AR Arom cells) to explore the role of AR in aromatase inhibitor (AI) resistance. Androstendione (AD) was used as a substrate for aromatization to estrogen. The nonsteroidal AI anastrazole (Ana) inhibited AD-stimulated growth and ER transcriptional activity in MCF-7 Arom cells, but not in MCF-7 AR Arom cells. Enhanced activation of pIGF-1R and pAKT was found in AR-overexpressing cells, and their inhibitors restored sensitivity to Ana, suggesting that these pathways represent escape survival mechanisms. Sensitivity to Ana was restored with AR antagonists, or the antiestrogen fulvestrant. These results suggest that both AR and ERα must be blocked to restore sensitivity to hormonal therapies in AR-overexpressing ERα-positive breast cancers. AR contributed to ERα transcriptional activity in MCF-7 AR Arom cells, and AR and ERα co-localized in AD + Ana-treated cells, suggesting cooperation between the two receptors. AR-mediated resistance was associated with a failure to block ER transcriptional activity and enhanced up-regulation of AR and ER-responsive gene expression. Clinically, it may be necessary to block both AR and ERα in patients whose tumors express elevated levels of AR. In addition, inhibitors to the AKT/IGF-1R signaling pathways may provide alternative approaches to block escape pathways and restore hormone sensitivity in resistant breast tumors.

Repressive histone tail modifications have been associated with molecular breast cancer subtypes. We investigated whether histone 3 lysine 9 trimethylation (H3K9me3) and histone 3 lysine 27 trimethylation (H3K27me3) were associated with tumor features and subtypes while adjusting for prospectively collected reproductive and lifestyle breast cancer risk factors. We have tissue microarray data with immunohistochemical marker information on 804 incident cases of invasive breast cancer diagnosed from 1976-2000 in the Nurses' Health Study. Tissue microarray sections were stained for global H3K9me3 and H3K27me3, and scored into four categories. Multivariate odds ratios (OR) and 95 % confidence intervals (CI) were calculated using logistic regression models for tumor features and subtypes, adjusting for breast cancer risk factors. While there were no significant associations between H3K9me3 and tumor features, H3K27me3 was significantly associated with lower grade tumors compared to high grade tumors in the multivariate model (OR = 1.95, 95 % CI 1.35-2.81, p = 0.0004). H3K27me3 was suggestively associated with estrogen receptor-positive (ER+) tumors (OR = 1.47, 95 % CI 0.97-2.23, p = 0.07). In subtype analyses, H3K27me3 was positively associated with the luminal A subtype compared to all other subtypes (OR = 1.42, 95 % CI 1.14-1.77, p = 0.002), and was inversely associated with HER2-type (OR = 0.58, 95 % CI 0.37-0.91, p = 0.02) and basal-like breast cancer (OR = 0.52, 95 % CI 0.36-0.76, p = 0.0006). In the largest immunohistochemical examination of H3K9me3 and H3K27me3 in breast cancer, we found that H3K27me3 positivity, but not H3K9me3, was associated with lower grade tumors and the luminal A subtype after adjusting for reproductive and lifestyle breast cancer risk factors.

In most human breast cancers, tumor cell proliferation is estrogen dependent. Although hormone-responsive tumors initially respond to anti-estrogen therapies, most of them eventually develop resistance. Our goal was to identify alternative targets that might be regulated to control breast cancer progression. Sulforhodamine B assay was used to measure the viability of cultured human breast cancer cell lines exposed to various inhibitors. Protein expression in whole-cell extracts was determined by Western blotting. BT-474 tumor xenografts in nude mice were used for in vivo studies of tumor progression. RO 48-8071 ([4'-[6-(Allylmethylamino)hexyloxy]-4-bromo-2'-fluorobenzophenone fumarate]; RO), a small-molecule inhibitor of oxidosqualene cyclase (OSC, a key enzyme in cholesterol biosynthesis), potently reduced breast cancer cell viability. In vitro exposure of estrogen receptor (ER)-positive human breast cancer cells to pharmacological levels of RO or a dose close to the IC50 for OSC (nM) reduced cell viability. Administration of RO to mice with BT-474 tumor xenografts prevented tumor growth, with no apparent toxicity. RO degraded ERα while concomitantly inducing the anti-proliferative protein ERβ. Two other cholesterol-lowering drugs, Fluvastatin and Simvastatin, were less effective in reducing breast cancer cell viability and were found not to induce ERβ. ERβ inhibition or knockdown prevented RO-dependent loss of cell viability. Importantly, RO had no effect on the viability of normal human mammary cells. RO is a potent inhibitor of hormone-dependent human breast cancer cell proliferation. The anti-tumor properties of RO appear to be in part due to an off-target effect that increases the ratio of ERβ/ERα in breast cancer cells.

Organosulfur compounds from garlic effectively inhibit growth of transplanted as well as spontaneous cancers in preclinical animal models without any adverse side effects. However, the mechanisms underlying anticancer effect of this class of compounds are not fully understood. This study reports, for the first time, that garlic organosulfide diallyl trisulfide (DATS) inhibits estrogen receptor-α (ER-α) activity in human breast cancer cells. Exposure of MCF-7 and T47D cells to DATS resulted in downregulation of ER-α protein, which peaked between 12- and 24-h post-treatment. DATS was relatively more effective in suppressing ER-α protein expression compared with its mono and disulfide analogs. The 17β-estradiol (E2)-induced expression of pS2 and cyclin D1, ER-α target gene products, was also decreased in the presence of DATS. Downregulation of ER-α protein expression resulting from DATS treatment was accompanied by a decrease in nuclear levels of ER-α protein, ER-α mRNA suppression, and inhibition of ERE2e1b-luciferase reporter activity. DATS-mediated inhibition of cell viability and apoptosis induction were not affected in the presence of E2. In agreement with these results, ectopic expression of ER-α in MDA-MB-231 cell line failed to confer any protection against cell proliferation inhibition or apoptosis induction resulting from DATS exposure. DATS treatment caused a decrease in protein levels of peptidyl-prolyl cis-trans isomerase (Pin1), and overexpression of Pin1 partially attenuated ER-α downregulation by DATS. DATS-induced apoptosis was modestly but significantly augmented by overexpression of Pin1. In conclusion, this study identifies ER-α as a novel target of DATS in mammary cancer cells.

The objective of this study was to determine the conversion rate of human epidermal growth factor receptor 2 (HER2), estrogen receptor (ER) and progesterone receptor (PR) between primary tumors and metastatic lesions in advanced breast cancer. Patients with suspected diagnosis of locally recurrent or metastatic breast cancer, either at first relapse or after successive disease progressions, who had an appropriately preserved sample from a primary tumor and were scheduled for a biopsy of the recurrent lesion, were included. Blinded determinations of receptor status on paired samples were performed by immunohistochemistry and fluorescence in situ hybridization at a central laboratory and compared with those performed locally. Overall, 196 patients were included and 184 patients were considered evaluable. Reasons for non-evaluability included the inability to perform biopsy (n = 4) or biopsy results showing normal tissue (n = 3), benign disease (n = 3) or a second neoplasia (n = 2). Conversion rates determined at local level were higher than those determined centrally (HER2: 16 vs. 3 %, ER: 21 vs. 13 %, PR: 35 vs. 28 %, respectively). There was substantial agreement regarding the expression of HER2 in primary tumors and metastases, and ER at metastases, between local and central laboratories. PR at any site and ER at primary site showed moderate agreement. Oncologists altered their treatment plans in 31 % of patients whose tumor subtype had changed. These results reinforce the recommendation for performing confirmatory biopsies of metastases, not only to avoid misdiagnosis of breast cancer relapse, but also to optimize treatment (clinicaltrials.gov identifier: NCT01377363).

Choice of therapy for breast cancer relies on human epidermal growth factor receptor-2 (HER2) and estrogen receptor α (ER) status. Before randomization in the phase III Adjuvant Lapatinib and/or Trastuzumab Treatment Optimisation (ALTTO) trial for HER2-positive disease, HER2 and ER were centrally reviewed by Mayo Clinic (Rochester, MN, and Scottsdale, AZ) for North America and by the European Institute of Oncology (IEO; Milan, Italy) for the rest of world (except China). Discordance rates (local vs. central review) differed between Mayo and IEO. Among locally HER2-positive cases, 5.8 % (Mayo) and 14.5 % (IEO) were centrally HER2 negative. Among locally ER-positive cases, 16.2 % (Mayo) and 4.2 % (IEO) were centrally ER-negative. Among locally ER-negative cases, 3.4 % (Mayo) and 21.4 % (IEO) were centrally ER-positive. We, therefore, performed a ring study to identify features contributing to these differing discordance rates. Mayo and IEO exchanged slides for 25 HER2 and 35 ER locally/centrally discordant cases. Both laboratories performed IHC and FISH for HER2 using the HercepTest(®) and PathVysion HER2 DNA probe kit/HER2/centromere 17 probe mixture. IHC for ER was tested centrally using the monoclonal ER 1D5 antibody (Mayo) or the DAKO cocktail of ER 1D5 and 2.123 antibodies (IEO). Mayo and IEO confirmed the central HER2-negative result in 100 % of 25 cases. Mayo and IEO confirmed the central ER result in 29 (85 %) of 34 evaluable cases. The five Mayo-negative/IEO-positive cases were ER-positive when retested at Mayo using the DAKO ER cocktail. In this ring study, ALTTO ineligibility did not change when HER2 testing was performed by either IEO or Mayo central laboratories. However, a dual antibody ER assay had fewer false-negative test results than an assay with a single antibody, and there was more discordance between the two ER reagents than has been previously reported. Using even slightly different assay methods yielded different results, even between experienced central laboratories.

Endocrine therapy resistance in estrogen receptor alpha positive (ERα+) breast cancers remains a major obstacle for maintaining efficacy of targeted therapies. We investigated the significance and the mechanisms involved in cMYC over-expression in a MCF7 derived panel of ERα+ breast cancer cells which can proliferate in the absence of estrogen with different sensitivities to anti-hormone therapies. We show that all the resistant cell lines tested over-express cMYC as compared to parental MCF7 cells and its inhibition lead to the differential blocking of estrogen-independent proliferation in resistant cells. Further investigation of the resistant cell line, MCF7:5C, suggested transcriptional de-regulation of cMYC gene was responsible for its over-expression. Chromatin immuno-precipitation assay revealed markedly higher recruitment of phosphorylated serine-2 carboxy-terminal domain (CTD) of RNA polymerase-II at the proximal promoter of cMYC gene, which is responsible for transcriptional elongation of the cMYC RNA. The level of CDK9, a factor responsible for the phosphorylation of serine-2 of RNA polymerase II CTD, was found to be elevated in all the resistant cell lines. Pharmacological inhibition of CDK9 not only reduced the transcripts and the protein levels of cMYC in MCF7:5C cells but also selectively inhibited the estrogen-independent growth of all the resistant cell lines. This study describes the up-stream molecular events involved in the transcriptional over-expression of cMYC gene in breast cancer cells proliferating estrogen-independently and identifies CDK9 as a potential novel drug target for therapeutic intervention in endocrine-resistant breast cancers.

It is well established that only estrogen receptor (ER)-positive tumors benefit from hormonal therapies. We hypothesized that a subgroup of breast cancer patients expresses estrogen receptor α (ERα), but fails to respond to hormonal therapy due to the expression of a non-functional receptor. We analyzed a series of 2,658 ERα-positive HER2-negative breast tumors for ERα and progesterone receptor (PR) status as determined by mRNA expression and for their molecular subtypes (Luminal type vs Basal type, assessed by BluePrint™ molecular subtyping assay). In addition, we assessed the recurrence risk (low vs high) using the 70-gene MammaPrint™ signature. We found that 55 out of 2,658 (2.1 %) tumors that are ERα positive by mRNA analysis also demonstrate a Basal molecular subtype, indicating that they lack expression of estrogen-responsive genes. These ERα-positive Basal-type tumors express significantly lower levels of both ERα and PR mRNA as compared to Luminal-type tumors (P < 0.0001) and almost invariably (94.5 %) have a high-risk MammaPrint™ profile. Twelve of the MammaPrint™ genes are directly ERα responsive, indicating that MammaPrint™ assesses ERα function in breast cancer without considering ERα mRNA levels. We find a relatively high expression of the dominant negative ERα splice variant ERΔ7 in ERα-positive Basal-type tumors as compared to ERα-positive Luminal-type tumors (P < 0.0001). Expression of the dominant negative ERα variant ERΔ7 provides a rationale as to why tumors are of the Basal molecular subtype while staining ERα positive by immunohistochemistry. These tumors may lack a functional response to estrogen and consequently may not respond to hormonal therapy. Our data indicate that such patients are of MammaPrint™ high recurrence risk and might benefit from adjuvant chemotherapy.

Estrogen catabolism is a major function of CYP2C19. The effect of CYP2C19 polymorphisms on tamoxifen sensitivity may therefore not only be mediated by a variation in tamoxifen metabolite levels but also by an effect on breast cancer risk and molecular subtype due to variation in lifelong exposure to estrogens. We determined the association between these polymorphisms and tamoxifen sensitivity in the context of a randomized trial, which allows for the discernment of prognosis from prediction. We isolated primary tumor DNA from 535 estrogen receptor-positive, stages I-III, postmenopausal breast cancer patients who had been randomized to tamoxifen (1-3 years) or no adjuvant therapy. Recurrence-free interval improvement with tamoxifen versus control was assessed according to the presence or absence of CYP2C19 2 and CYP2C19 17. Hazard ratios and interaction terms were calculated using multivariate Cox proportional hazard models, stratified for nodal status. Tamoxifen benefit was not significantly affected by CYP2C19 17. Patients with at least one CYP2C19 2 allele derived significantly more benefit from tamoxifen (HR 0.26; p = 0.001) than patients without a CYP2C19 2 allele (HR 0.68; p = 0.18) (p for interaction 0.04). In control patients, CYP2C19 2 was an adverse prognostic factor. In conclusion, breast cancer patients carrying at least one CYP2C19 2 allele have an adverse prognosis in the absence of adjuvant systemic treatment, which can be substantially improved by adjuvant tamoxifen treatment.

Resistance to tamoxifen is a major clinical challenge in the treatment of breast cancer; however, it is still unclear which signaling pathways are the major drivers of tamoxifen-resistant growth. To characterize resistance mechanisms, we have generated different tamoxifen-resistant breast cancer cell lines from MCF-7. In this model, we investigated whether signaling from human epidermal growth factor receptors (HERs), their downstream kinases, or from the estrogen receptor α (ERα) was driving tamoxifen-resistant cell growth. Increased expression of EGFR and increased phosphorylation of HER3 were observed upon acquisition of tamoxifen resistance, and the extracellular activated kinase (ERK) signaling pathway was highly activated in the resistant cells. The EGFR inhibitor gefitinib and the ERK pathway inhibitor U0126 resulted in partial and preferential growth inhibition of tamoxifen-resistant cells. All the tamoxifen-resistant cell lines retained ERα expression but at a lower level compared to that in MCF-7. Importantly, we showed via ERα knockdown that the tamoxifen-resistant cells were dependent on functional ERα for growth and we observed a clear growth stimulation of resistant cell lines with clinically relevant concentrations of tamoxifen and 4-OH-tamoxifen, indicating that tamoxifen-resistant cells utilize agonistic ERα stimulation by tamoxifen for growth. The tamoxifen-resistant cells displayed high phosphorylation of ERα at Ser118 in the presence of tamoxifen; however, treatment with U0126 neither affected the level of Ser118 phosphorylation nor expression of the ERα target Bcl-2, suggesting that ERK contributes to cell growth independently of ERα in our cell model. In support of this, combined treatment against ERα and ERK signaling in resistant cells was superior to single-agent treatment and as effective as fulvestrant treatment of MCF-7 cells. Together, these findings demonstrate that ERα is a major driver of growth in tamoxifen-resistant cells supported by HER/ERK growth signaling, implying that combined targeting of these pathways may have a clinical potential for overcoming tamoxifen resistance.

Psoriasin (S100A7) is a calcium-binding protein that has shown to be highly expressed in high-grade ductal carcinoma in situ (DCIS) and a subset of invasive breast cancers. However, its role in invasion and metastasis is not very well known. In this study, we have shown that S100A7 differentially regulates epidermal growth factor (EGF)-induced cell migration and invasion in ERα(-) MDA-MB-231 cells and ERα(+) MCF-7 and T47D breast cancer cells. Further signaling studies revealed that S100A7 enhances EGF-induced EGFR phosphorylation and actin remodeling that seems to favor lamellipodia formation in ERα(-) cells. In addition, S100A7 overexpression enhanced NF-κB-mediated matrix metalloproteinase-9 (MMP-9) secretion in MDA-MB-231 cells indicating its role in enhanced invasiveness. However, S100A7 overexpression inhibited migration and invasion of MCF-7 cells by inactivating Rac-1 pathway and MMP-9 secretion. Moreover, S100A7 overexpressing MDA-MB-231 cells showed enhanced metastasis compared to vector control in in vivo nude mice as detected by bioluminescence imaging. Our tissue microarray data also revealed predominant expression of S100A7 in ERα(-) metastatic carcinoma, especially in lymph node regions. Overall these studies suggest that S100A7 may enhance metastasis in ERα(-) breast cancer cells by a novel mechanism through regulation of actin cytoskeleton and MMP-9 secretion.

The molecular classification of breast cancer mainly focuses on ER, PR, and HER2 status detected by immunohistochemistry (IHC) analysis. To explore the clinical value of breast cancer classification based on gene-based diagnosis of the triple markers, we measured ESR1, PGR, and ERBB2 mRNA levels in 294 breast cancer patients by reverse transcription quantitative polymerase chain reaction (RT-QPCR), and examined their correlation with ER, PR, and HER2 status detected by IHC. We observed a significant positive correlation between the mRNA levels of the triple markers and their protein status (ESR1 vs. ER, Spearman's ρ = 0.527, P = 2.3 × 10(-22); PGR vs. PR, Spearman's ρ = 0.631, P = 5.1 × 10(-34); ERBB2 vs. HER2, Spearman's ρ = 0.439, P = 3.0 × 10(-15)). Furthermore, the subtypes determined by mRNA levels of the triple markers were significantly correlated to the subtypes determined based on their protein status (Spearman's ρ = 0.342, P = 2.0 × 10(-8)). Kaplan-Meier analysis showed that the subtypes determined by mRNA levels of the triple-marker could predict the disease-free survival (DFS) in breast cancer patients. Multivariate analysis showed that the predictive value of DFS could be confirmed for the subtypes determined by mRNA levels of the triple markers (HR = 2.285, P = 0.008) but not for those determined by their protein status. Taken together, our results suggest that the detection of ESR1/PGR/ERBB2 mRNA levels by RT-QPCR is a better approach for subtyping breast cancer and predicting the prognosis.

Endocrine therapy is an important therapeutic approach for the treatment of oestrogen receptor (ER)-positive breast cancer. However, a number of these endocrine therapies can fail when the tumour loses its ER expression during treatment. To date, few studies have explored the potential clinical significance of traditional Chinese medicine in inducing the reversal of resistance to endocrine therapy in breast cancers. We used the ERα-negative MCF7 breast cancer cell line to create a tamoxifen (TAM)-resistant cell line, MCF7/TAM cells. After treating MCF7/TAM cells with ELE to induce the re-expression of ERα, we investigated the role and molecular mechanisms by which elemene (ELE) promotes the reversal of resistance to endocrine therapy. We discovered that treatment with 10 μg/ml ELE restored the sensitivity of MCF7/TAM cells to TAM. RT-PCR analysis revealed that ELE treatment upregulated ERα mRNA levels in MCF7/TAM cells, and immunohistochemistry confirmed the upregulation of ERα expression. Western blot analysis revealed that ELE treatment decreased the protein expression levels of Ras, MEK1/2 and p-ERK1/2 in MCF7/TAM cells. The loss of ERα expression was the primary reason for TAM resistance in MCF7 cells. The ELE-induced reversal of TAM resistance was mediated by the upregulation of ERα mRNA and the re-expression of ERα through the MAPK pathway.

Our previous studies demonstrated that specific polyamine analogues, oligoamines, down-regulated the activity of a key polyamine biosynthesis enzyme, ornithine decarboxylase (ODC), and suppressed expression of estrogen receptor alpha (ERα) in human breast cancer cells. However, the mechanism underlying the potential regulation of ERα expression by polyamine metabolism has not been explored. Here, we demonstrated that RNAi-mediated knockdown of ODC (ODC KD) down-regulated the polyamine pool, and hindered growth in ERα-positive MCF7 and T47D and ERα-negative MDA-MB-231 breast cancer cells. ODC KD significantly induced the expression and activity of the key polyamine catabolism enzymes, spermine oxidase (SMO) and spermidine/spermine N (1)-acetyltransferase (SSAT). However, ODC KD-induced growth inhibition could not be reversed by exogenous spermidine or overexpression of antizyme inhibitor (AZI), suggesting that regulation of ODC on cell proliferation may involve the signaling pathways independent of polyamine metabolism. In MCF7 and T47D cells, ODC KD, but not DFMO treatment, diminished the mRNA and protein expression of ERα. Overexpression of antizyme (AZ), an ODC inhibitory protein, suppressed ERα expression, suggesting that ODC plays an important role in regulation of ERα expression. Decrease of ERα expression by ODC siRNA altered the mRNA expression of a subset of ERα response genes. Our previous analysis showed that oligoamines disrupt the binding of Sp1 family members to an ERα minimal promoter element containing GC/CA-rich boxes. By using DNA affinity precipitation and mass spectrometry analysis, we identified ZBTB7A, MeCP2, PARP-1, AP2, and MAZ as co-factors of Sp1 family members that are associated with the ERα minimal promoter element. Taken together, these data provide insight into a novel antiestrogenic mechanism for polyamine biosynthesis enzymes in breast cancer.

ERα function is crucial for the development of normal mammary gland as well as in the process of progression of breast cancer cells. Signals that target receptor levels contribute to regulate estrogens effects in the cells. An intricate cross-regulation has been documented between ERα and TGF-β down-stream molecules: SMAD2, SMAD3, and SMAD4, that can bind ERα and regulate their signaling. Thus, identification of natural anticancer drugs able to influence the latter molecule might provide alternative choices for breast cancer treatment. Taking into account our previous published data we wanted to study the effect of 5-Methoxypsoralen (bergapten) on ERα and on TGF-β pathway. We reported that bergapten, a coumarin containing compound, effectively depletes ERα in MCF-7 breast cancer sensitive cells and in tamoxifen-resistant clone. The decrease of ERα protein after bergapten treatment results from the ubiquitine-proteasome pathway as demonstrated by the use of MG-132. IP experiments with ER antibody, demonstrated that the protein has physical interaction with SMAD4 and poly-ubiquitine and the amount of ubiquitinated receptor, linked to SMAD4, is greater under bergapten. The crucial role played by SMAD4, in this process, emerges from the observation that in breast cancer cells, silencing of SMAD4, resulted in increased expression of endogenous ERα in both control and bergapten-treated cells, compared to wild- type cells. The same results were confirmed in siRNA TGF-β RII cells. The results suggest a novel negative regulation of ERα by TGF-β/SMAD4 in breast cancer cells and indicate that the SMAD4 protein is involved in the degradation of ERα induced by bergapten. We propose that bergapten may efficiently act as a natural antitumoral agent, able to deplete ERα from breast cancer tamoxifen-sensitive and resistant cells, thereby retraining the effect of membrane signals targeting ERα and in such way its mitogenic potentiality.

Silencing mediator of retinoic acid and thyroid hormone receptor (SMRT), also known as nuclear corepressor 2 (NCOR2) is a transcriptional corepressor for multiple members of the nuclear receptor superfamily of transcription factors, including estrogen receptor-α (ERα). In the classical model of corepressor action, SMRT binds to antiestrogen-bound ERα at target promoters and represses ERα transcriptional activity and gene expression. Herein SMRT mRNA and protein expression was examined in a panel of 30 breast cancer cell lines. Expression of both parameters was found to vary considerably amongst lines and the correlation between protein and mRNA expression was very poor (R (2) = 0.0775). Therefore, SMRT protein levels were examined by immunohistochemical staining of a tissue microarray of 866 patients with stage I-II breast cancer. Nuclear and cytoplasmic SMRT were scored separately according to the Allred score. The majority of tumors (67 %) were negative for cytoplasmic SMRT, which when detected was found at very low levels. In contrast, nuclear SMRT was broadly detected. There was no significant difference in time to recurrence (TTR) according to SMRT expression levels in the ERα-positive tamoxifen-treated patients (P = 0.297) but the difference was significant in the untreated patients (P = 0.01). In multivariate analysis, ERα-positive tamoxifen-untreated patients with high nuclear SMRT expression (SMRT 5-8, i.e., 2nd to 4th quartile) had a shorter TTR (HR = 1.94, 95 % CI, 1.24-3.04; P = 0.004) while there was no association with SMRT expression for ERα-positive tamoxifen-treated patients. There was no association between SMRT expression and overall survival for patients, regardless of whether they received tamoxifen. Thus while SMRT protein expression was not predictive of outcome after antiestrogen therapy, it may have value in predicting tumor recurrence in patients not receiving adjuvant tamoxifen therapy.