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The advent of HER2-directed therapies has significantly improved the outlook for patients with HER2-positive early stage breast cancer. However, a significant proportion of these patients still relapse and die of breast cancer. Trials to define, refine and optimize the use of the two approved HER2-targeted agents (trastuzumab and lapatinib) in patients with HER2-positive early stage breast cancer are ongoing. In addition, promising new approaches are being developed including monoclonal antibodies and small-molecule tyrosine kinase inhibitors targeting HER2 or other HER family members, antibodies linked to cytotoxic moieties or modified to improve their immunological function, immunostimulatory peptides, and targeting the PI3K and IGF-1R pathways. Improved understanding of the HER2 signaling pathway, its relationship with other signaling pathways and mechanisms of resistance has also led to the development of rational combination therapies and to a greater insight into treatment response in patients with HER2-positive breast cancer. Based on promising results with new agents in HER2-positive advanced-stage disease, a series of large trials in the adjuvant and neoadjuvant settings are planned or ongoing. This Review focuses on current treatment for patients with HER2-positive breast cancer and aims to update practicing clinicians on likely future developments in the treatment for this disease according to ongoing clinical trials and translational research.

Endocrine therapy represents the first and most efficacious targeted treatment for women with estrogen receptor-positive (ER+) breast cancer. In the last four decades several hormonal agents have been successfully introduced in clinical practice as both palliative therapy for advanced disease and adjuvant treatment for prevention of tumor relapse. Nevertheless, the intrinsic and acquired resistance occurs in a significant proportion of patients, limiting the efficacy of endocrine treatments. Several molecular mechanisms have been proposed to be responsible for endocrine resistance. Loss of ER expression, altered activity of ER coregulators, deregulation of apoptosis and cell cycle signaling, and hyperactive receptor tyrosine kinase (RTK) and stress/cell kinase pathways can collectively orchestrate the development and sustenance of pharmacologic resistance to endocrine therapy. Preclinical and clinical evidence documents the plasticity in ER expression levels and signaling. As such, ER can either drive gene transcription and tumor progression directly or crosstalk with alternate RTK and cellular kinase signaling pathways, resulting in modulation of its own expression levels and transcriptional program. For this reason a therapeutic approach based on the combination of agents targeting both ER and RTK signaling represents a promising strategy to be tested. Among many RTKs, EGFR, HER2, and PI3K have been found to be viable targets for the combination therapy strategy, at least in the preclinical setting. However, early results from clinical trials testing combination strategies have been discordant, suggesting the need for better approaches to simultaneously inhibit multiple escape pathways and to select the patients who may benefit the most from these strategies., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The recent incremental advances made in the treatment of metastatic breast cancer have elicited potential for survival extension in this treatable, yet incurable, population of breast cancer patients. Clinicians have focused on targeted therapies, which aim at signaling receptors such as the human epidermal receptor superfamily, the estrogen receptor, VEGF, the insulin-like growth factor receptor, the hepatocyte growth factor receptor (cMET), phosphoinositide 3-kinase, mTOR, and many others., (©2011 AACR.)

Introduction: The overexpression of human epidermal growth factor receptor (HER)-2 in 20% of human breast cancers and its association with aggressive growth has led to widespread use of HER2-targeted therapies, such as trastuzumab (T) and lapatinib (L). Despite the success of these drugs, their efficacy is limited in patients whose tumors demonstrate de novo or acquired resistance to treatment. The β1 integrin resides on the membrane of the breast cancer cell, activating several elements of breast tumor progression including proliferation and survival., Methods: We developed a panel of HER2-overexpressing cell lines resistant to L, T, and the potent LT combination through long-term exposure and validated these models in 3D culture. Parental and L/T/LT-resistant cells were subject to HER2 and β1 integrin inhibitors in 3D and monitored for 12 days, followed by quantification of colony number. Parallel experiments were conducted where cells were either stained for Ki-67 and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) or harvested for protein and analyzed by immunoblot. Results were subjected to statistical testing using analysis of variance and linear contrasts, followed by adjustment with the Sidak method., Results: Using multiple cell lines including BT474 and HCC1954, we reveal that in L and LT resistance, where phosphorylation of EGFR/HER1, HER2, and HER3 are strongly inhibited, kinases downstream of β1 integrin--including focal adhesion kinase (FAK) and Src--are up-regulated. Blockade of β1 by the antibody AIIB2 abrogates this up-regulation and functionally achieves significant growth inhibition of L and LT resistant cells in 3D, without dramatically affecting the parental cells. SiRNA against β1 as well as pharmacologic inhibition of FAK achieve the same growth inhibitory effect. In contrast, trastuzumab-resistant cells, which retain high levels of phosphorylated EGFR/HER1, HER2, and HER3, are only modestly growth-inhibited by AIIB2., Conclusions: Our data suggest that HER2 activity, which is suppressed in resistance involving L but not T alone, dictates whether β1 mediates an alternative pathway driving resistance. Our findings justify clinical studies investigating the inhibition of β1 or its downstream signaling moieties as strategies to overcome acquired L and LT resistance.

Purpose: We have shown that incomplete blockade of the human epidermal growth factor (HER) pathway is a mechanism of resistance to treatment with trastuzumab (T) in HER2-overexpressing tumor xenografts. We now investigate whether the addition of lapatinib (L), a dual HER1/2 kinase inhibitor, to T results in more potent inhibition of the pathway and therefore inhibition of tumor growth, and whether reduced dose and intermittent treatment with the combination is equally effective., Experimental Design: Nude mice bearing HER2-overexpressing MCF7/HER2-18 or BT-474 xenograft tumors were treated with L and T, alone or in various combinations with other HER inhibitors. L + T for short duration (14 and 42 days), intermittent administration (14 days on/off), and reduced dosing (half dose) was also investigated. Inhibition of tumor growth, downstream signaling, proliferation, and induction of apoptosis were assessed. All statistical tests were two-sided., Results: L + T was the most effective regimen in both MCF7/HER2-18 and BT-474 xenografts with complete regression (CR) of tumor observed in all mice. Intermittent and reduced dose treatment (½ dose) resulted in high rates of CR and low rates of tumor recurrence that were comparable to full dose continuous treatment. L + T resulted in significantly reduced downstream signaling and proliferation, and increased apoptosis., Conclusions: L + T is a potent and effective combination even when given in reduced dose or intermittent schedule potentially resulting in lower toxicity and reduced cost if translated to patients. These findings warrant timely clinical testing., (©2011 AACR.)

Among breast cancers, triple-negative breast cancer (TNBC) is the most poorly understood and is refractory to current targeted therapies. Using a genetic screen, we identify the PTPN12 tyrosine phosphatase as a tumor suppressor in TNBC. PTPN12 potently suppresses mammary epithelial cell proliferation and transformation. PTPN12 is frequently compromised in human TNBCs, and we identify an upstream tumor-suppressor network that posttranscriptionally controls PTPN12. PTPN12 suppresses transformation by interacting with and inhibiting multiple oncogenic tyrosine kinases, including HER2 and EGFR. The tumorigenic and metastatic potential of PTPN12-deficient TNBC cells is severely impaired upon restoration of PTPN12 function or combined inhibition of PTPN12-regulated tyrosine kinases, suggesting that TNBCs are dependent on the proto-oncogenic tyrosine kinases constrained by PTPN12. Collectively, these data identify PTPN12 as a commonly inactivated tumor suppressor and provide a rationale for combinatorially targeting proto-oncogenic tyrosine kinases in TNBC and other cancers based on their profile of tyrosine-phosphatase activity., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Purpose: Increased growth factor signaling may contribute to tamoxifen resistance. This randomized phase II trial assessed tamoxifen plus placebo or the epidermal growth factor receptor inhibitor gefitinib in estrogen receptor (ER)-positive metastatic breast cancer., Experimental Design: Patients with newly metastatic disease or recurred after adjuvant tamoxifen (stratum 1), or recurred during/after adjuvant aromatase inhibitor (AI) or after failed first-line AI (stratum 2), were eligible. Primary variables were progression-free survival (PFS; stratum 1) and clinical benefit rate (CBR; stratum 2). A 5% or more improvement in response variables with gefitinib was considered to warrant further investigation. Outcome was correlated with biomarkers measured on the primary tumor., Results: In stratum 1 (n = 206), the PFS HR (gefitinib:placebo) was 0.84 (95% CI, 0.59-1.18; median PFS 10.9 versus 8.8 months). In the stratum 1 endocrine therapy-naïve subset (n = 158) the HR was 0.78 (95% CI, 0.52-1.15), and the prior endocrine-treated subgroup (n = 48) 1.47 (95% CI, 0.63-3.45). In stratum 1, CBRs were 50.5% with gefitinib and 45.5% with placebo. In stratum 2 (n = 84), CBRs were 29.2% with gefitinib and 31.4% with placebo. Biomarker analysis suggested that in stratum 1 there was greater benefit with gefitinib in patients who were ER-negative or had lower levels of ER protein., Conclusions: In stratum 1, the improved PFS with gefitinib plus tamoxifen met the protocol criteria to warrant further investigation of this strategy. In stratum 2, there was a numerical disadvantage for gefitinib; additional investigation after AI therapy is not warranted. Studies of predictive biomarkers are needed to subset appropriate patients., (©2011 AACR.)

Purpose: Phosphatase and tensin homolog (PTEN) loss or activating mutations of phosphoinositol-3 (PI3) kinase (PIK3CA) may be associated with trastuzumab resistance. Trastuzumab, the humanized human epidermal growth factor receptor 2 (HER2) monoclonal antibody, and lapatinib, an epidermal growth factor receptor/HER2 tyrosine kinase inhibitor, are both established treatments for HER2-overexpressing breast cancers. Understanding of the cellular response to HER2-targeted therapies is needed to tailor treatments and to identify patients less likely to benefit., Methods: We evaluated the effect of trastuzumab or lapatinib in three HER2-overexpressing cell lines. We confirmed the in vitro observations in two neoadjuvant clinical trials in patients with HER2 overexpression; 35 patients received trastuzumab as a single agent for the first 3 weeks, then docetaxel every 3 weeks for 12 weeks (trastuzumab regimen), whereas 49 patients received lapatinib as a single agent for 6 weeks, followed by trastuzumab/docetaxel for 12 weeks before primary surgery (lapatinib regimen). Apoptosis, Ki67, p-MAPK, p-AKT, and PTEN were assessed by immunohistochemistry. Genomic DNA was sequenced for PIK3CA mutations., Results: Under low PTEN conditions, in vitro data indicate that lapatinib alone and in combination with trastuzumab was effective in decreasing p-MAPK and p-AKT levels, whereas trastuzumab was ineffective. In the clinical trials, we confirmed that low PTEN or activating mutation in PIK3CA conferred resistance to the trastuzumab regimen (P = .015), whereas low PTEN tumors were associated with a high pathologic complete response rate (P = .007)., Conclusion: Activation of PI3 kinase pathway is associated with trastuzumab resistance, whereas low PTEN predicted for response to lapatinib. These observations support clinical trials with the combination of both agents.

The estrogen receptor (ER) pathway plays a pivotal role in breast cancer development and progression. Endocrine therapy to block the ER pathway is highly effective, but its usefulness is limited by common intrinsic and acquired resistance. Multiple mechanisms responsible for endocrine resistance have been proposed and include deregulation of various components of the ER pathway itself, alterations in cell cycle and cell survival signaling molecules, and the activation of escape pathways that can provide tumors with alternative proliferative and survival stimuli. Among these, increased expression or signaling of growth factor receptor pathways, especially the EGFR/HER2 pathway, has been associated with both experimental and clinical endocrine therapy resistance. New treatment combinations targeting both ER and growth factor receptor signaling to block the crosstalk between these pathways and eliminate escape routes have been proven highly effective in preclinical models. Results of recent clinical studies, while partly supporting this approach, also highlight the need to better identify a priori the patients whose tumors are most likely to benefit from these specific cotargeting strategies.

Purpose: There are no established genetic markers for prediction of outcomes after cyclophosphamide (CP)-containing adjuvant therapy for breast cancer. In an ancillary study to a SWOG (Southwest Oncology Group) trial (S8897), we investigated functional polymorphisms in 4 genes in CP pharmacokinetic pathways in relation to hematologic toxicity and disease-free survival (DFS)., Experimental Design: Germline DNA was available from 458 women who were at high risk of relapse and was randomized to CAF (CP, intravenous doxorubicin, and 5-fluorouracil) versus CMF (CP, intravenous methotrexate, and 5-fluorouracil) ± tamoxifen, and from 874 women who had a presumed favorable prognosis and did not receive adjuvant therapy. Odds ratios for grade 3 and 4 hematologic toxicity in the treated group and hazard ratios for DFS associated with selected functional polymorphisms in CYP2B6CYP3A4GSTA1 and GSTP1 were estimated by logistic regression and Cox proportional hazard regression., Results: Compared with women with AA genotypes, those with at least 1 GSTP1 variant G allele had reduced risk of grade 3 and 4 neutropenia [odds ratios (OR) = 0.63, 95% CI = 0.41-0.97] and leucopenia (OR = 0.59, 95% CI = 0.39-0.89). No other associations between single nucleotide polymorphisms and toxicity or survival were found in the treated or untreated group., Conclusion: Known genetic variants in genes involved in CP pharmacokinetics may not have major effects on DFS in breast cancer patients. The lower risk of developing high-grade hematologic toxicity among women with variant GSTP1 alleles suggests that genetic markers in combination with clinical factors may be useful in defining a subgroup of women who are less susceptible to adverse hematologic toxicities with CP-containing therapies., (©2010 AACR)

Background: Currently available selective estrogen receptor modulators reduce the risk of breast cancer, but they are not widely used. In the Postmenopausal Evaluation and Risk-Reduction with Lasofoxifene (PEARL) trial, lasofoxifene was shown to reduce the risk of estrogen receptor-positive (ER+) breast cancer, nonvertebral and vertebral fractures, coronary artery disease, and stroke, but the effects on total breast cancer (invasive and ductal carcinoma in situ, ER+ and estrogen receptor-negative [ER-]) and ER+ invasive breast cancer are unknown., Methods: Postmenopausal women (n = 8556) aged 59-80 years with low bone density and normal mammograms were randomly assigned to two doses of lasofoxifene (0.25 and 0.5 mg) or placebo. The primary endpoints of the PEARL trial were incidence of ER+ breast cancer and nonvertebral fractures at 5 years. A nested case-control study of 49 incident breast cancer case patients and 156 unaffected control subjects from the PEARL trial was performed to evaluate treatment effects on risk of total and ER+ invasive breast cancer by baseline serum estradiol and sex hormone-binding globulin levels using logistic regression models. Cox proportional hazards models were used to evaluate risk of total breast cancer and ER+ invasive breast cancer using intention-to-treat analysis. All statistical tests were two-sided., Results: Breast cancer was confirmed in 49 women. Compared with placebo, 0.5 mg of lasofoxifene statistically significantly reduced the risk of total breast cancer by 79% (hazard ratio = 0.21; 95% confidence interval [CI] = 0.08 to 0.55) and ER+ invasive breast cancer by 83% (hazard ratio = 0.17; 95% CI = 0.05 to 0.57). The effects of 0.5 mg of lasofoxifene on total breast cancer were similar regardless of Gail score, whereas the effects were markedly stronger for women with baseline estradiol levels greater than the median (odds ratio = 0.11; 95% CI = 0.02 to 0.51) vs those with levels less than the median (odds ratio = 0.78; 95% CI = 0.16 to 3.79; P(interaction) = .04)., Conclusion: A 0.5-mg dose of lasofoxifene appears to reduce the risks of both total and ER+ invasive breast cancer in postmenopausal women with osteoporosis.

To date, the few studies of associations between a functional polymorphism in the oxidative stress-related gene manganese superoxide dismutase (SOD2) and breast cancer survival have been inconsistent. In a homogeneous patient population from a large cooperative group trial Southwest Oncology Group (SWOG) 8897, we evaluated this polymorphism in relation to both treatment-related toxicity and disease-free survival (DFS). Among 458 women who received cyclophosphamide-containing adjuvant chemotherapy, those with variant C alleles, related to higher antioxidant activity, experienced less grade 3-4 neutropenia (OR = 0.52, 95% CI = 0.29-0.92) but had worse DFS (HR = 1.59, 95% CI = 0.99-2.55) than women with TT genotypes. No associations were observed among 874 women who were followed without adjuvant therapy. Our results are consistent with the hypothesis that women with higher SOD2 antioxidant activity may experience less treatment-related toxicity but shorter time to disease recurrence or death after breast cancer adjuvant chemotherapy, supporting the modifying effects of oxidative stress-related enzymes on cancer treatment toxicity and efficacy.

Insulin receptor substrate-1 (IRS-1) is a cytoplasmic scaffolding protein that is phosphorylated by insulin-like growth factor-I receptor and recruits downstream effectors. Recent evidence suggests that IRS-1 has a nuclear localization and function. Here we investigated whether nuclear and cytoplasmic IRS-1 levels are associated with clinico-pathological characteristics and clinical outcome in breast cancer patients. Tissue microarrays from 1,097 patients with stage I-II breast cancer were stained by immunohistochemistry for IRS-1. Nuclear and cytoplasmic IRS-1 were scored separately according to the Allred score. Nuclear IRS-1 showed a positive association with estrogen receptor (ER) (r = 0.09, P = 0.003) and progesterone receptor (PR) (r = 0.08, P = 0.008) status and a negative correlation with lymph node involvement (r = -0.10, P = 0.001). Cytoplasmic IRS-1 did not correlate with ER or PR but showed a positive correlation with tumor size (r = 0.10, P = 0.001) and S-phase fraction (r = 0.16, P < 0.001). In univariate analysis, tamoxifen-treated patients with tumors showing positive nuclear IRS-1 had a better recurrence-free survival (RFS) (P = 0.009) and overall survival (OS) (P = 0.0007), while no association was shown between cytoplasmic IRS-1 and RFS or OS in the same group of patients. In multivariate analysis of patients receiving tamoxifen, negative nuclear IRS-1 showed a significantly reduced RFS (P = 0.046) and OS (P = 0.018). Combining both PR and nuclear IRS-1, tamoxifen-treated patients with PR+/IRS-1+ tumors had a better RFS (P = 0.0003) and OS (P < 0.0001) when compared with patients with PR-/IRS-1- tumors. In conclusion, nuclear IRS-1 may be a useful marker to predict tamoxifen response in patients with early breast cancer, particularly when assessed in combination with PR.

We hypothesized that a subset of sporadic triple negative (TN) breast cancer patients whose tumors have defective DNA repair similar to BRCA1-associated tumors are more likely to exhibit up-regulation of DNA repair-related genes, anthracycline-sensitivity, and taxane-resistance. We derived a defective DNA repair gene expression signature of 334 genes by applying a previously published BRCA1-associated expression pattern to three datasets of sporadic TN breast cancers. We confirmed a subset of 69 of the most differentially expressed genes by quantitative RT-PCR, using a low density custom array (LDA). Next, we tested the association of this DNA repair microarray signature expression with pathologic response in neoadjuvant anthracycline trials of FEC (n = 50) and AC (n = 16), or taxane-based TET chemotherapy (n = 39). Finally, we collected paraffin-fixed, formalin-embedded biopsies from TN patients who had received neoadjuvant AC (n = 28), and tested the utility of the LDA to discriminate response. Correlation between RNA expression measured by the microarrays and 69-gene LDA was ascertained. This defective DNA repair microarray gene expression pattern was significantly associated with anthracycline response and taxane resistance, with the area under the ordinary receiver operating characteristic curve (AUC) of 0.61 (95% CI = 0.45-0.77), and 0.65 (95% CI = 0.46-0.85), respectively. From the FFPE samples, the 69-gene LDA could discriminate AC responders, with AUC of 0.79 (95% CI = 0.59-0.98). In conclusion, a promising defective DNA repair gene expression signature appears to differentiate TN breast cancers that are sensitive to anthracyclines and resistant to taxane-based chemotherapy, and should be tested in clinical trials with other DNA-damaging agents and PARP-1 inhibitors.

Purpose: To develop a guideline to improve the accuracy of immunohistochemical (IHC) estrogen receptor (ER) and progesterone receptor (PgR) testing in breast cancer and the utility of these receptors as predictive markers., Methods: The American Society of Clinical Oncology and the College of American Pathologists convened an international Expert Panel that conducted a systematic review and evaluation of the literature in partnership with Cancer Care Ontario and developed recommendations for optimal IHC ER/PgR testing performance., Results: Up to 20% of current IHC determinations of ER and PgR testing worldwide may be inaccurate (false negative or false positive). Most of the issues with testing have occurred because of variation in preanalytic variables, thresholds for positivity, and interpretation criteria., Recommendations: The Panel recommends that ER and PgR status be determined on all invasive breast cancers and breast cancer recurrences. A testing algorithm that relies on accurate, reproducible assay performance is proposed. Elements to reliably reduce assay variation are specified. It is recommended that ER and PgR assays be considered positive if there are at least 1% positive tumor nuclei in the sample on testing in the presence of expected reactivity of internal (normal epithelial elements) and external controls. The absence of benefit from endocrine therapy for women with ER-negative invasive breast cancers has been confirmed in large overviews of randomized clinical trials.

The scaffold attachment factors SAFB1 and SAFB2 have been shown to function as estrogen receptor (ERalpha) co-repressors in breast cancer cells, and to affect many cellular processes such as stress response, RNA processing, and apoptosis. SAFB1 and SAFB2 have also been implicated in breast tumorigenesis: Their shared chromosomal locus at 19p13 is frequently lost in breast cancer, mutations have been identified, and overexpression results in growth inhibition. The purpose of this study was to determine SAFB1/SAFB2 protein expression in human breast tumors, to correlate their expression with either natural progression ("prognostic factor") or with response to Tamoxifen ("predictive factor"), and to analyze potential correlations with tumor characteristics. SAFB1/SAFB2 protein were measured by immunoblotting using a pan-SAFB antibody in tumor extracts from patients with long-term clinical follow-up (n = 289), a subset of whom had received no adjuvant systemic therapy after breast cancer surgery (n = 117) and another subset of whom were treated with adjuvant Tamoxifen (n = 172). SAFB levels were correlated with clinico-pathological variables and patient outcome. SAFB levels varied widely, with 25 tumors not expressing detectable levels of SAFB. SAFB expression was significantly correlated with ERalpha, HER-2, bcl-2 and with expression of other ERalpha coregulators such as SRC-3. There was no association between SAFB expression and disease free survival, however, low SAFB expression was significantly associated with worse overall survival in patients who did not receive adjuvant therapy. This study shows that low SAFB protein levels predict poor prognosis of breast cancer patients, suggesting critical functions of SAFB1 and SAFB2 in breast cancer cells.

Background: Epidermal growth factor receptor (EGFR) expression is associated with aggressive phenotypes in preclinical breast cancer models, but in clinical studies, EGFR has been inconsistently linked to poor outcome. We hypothesized that EGFR expression in human breast tumors, when centrally and uniformly assessed, is associated with an aggressive phenotype and resistance to systemic therapy., Methods: In a database of 47,286 patients with breast cancer, EGFR status was known on 2567 tumors. EGFR levels were measured centrally by ligand binding assay, and tumors with > or =10 fmol/mg were prospectively deemed positive. Clinical and biological features of EGFR-positive and EGFR-negative tumors were compared. Clinical outcomes were assessed by systemic therapy status., Results: Of 2567 tumors, 475 (18%) were EGFR positive. EGFR-positive tumors were more common in younger and in black women, were larger, had a higher S-phase fraction, and were more likely to be aneuploid. EGFR-positive tumors were more likely to be HER2-positive (26% vs 16%, P < .0001), but less likely to be estrogen receptor-positive (60% vs 88%, P < .0001) or progesterone receptor-positive (26% vs 65%, P < .0001). In multivariate analyses, EGFR expression independently correlated with worse disease-free survival (hazard ratio [HR] = 1.66; 95% confidence interval [CI], 1.4-2.41, P = .007) and overall survival (HR = 1.98, 95% CI, 1.36-2.88, P = .0004) in treated patients, but not in untreated patients., Conclusions: EGFR expression is more common in breast tumors in younger and black women. It is associated with lower hormone receptor levels, higher proliferation, genomic instability, and HER2 overexpression. It is correlated with higher risk of relapse in patients receiving adjuvant treatment. Blocking EGFR may improve outcome in selected patients.

Introduction: Accumulating evidence suggests that both levels and activity of the estrogen receptor (ER) and the progesterone receptor (PR) are dramatically influenced by growth-factor receptor (GFR) signaling pathways, and that this crosstalk is a major determinant of both breast cancer progression and response to therapy. The phosphatidylinositol 3-kinase (PI3K) pathway, a key mediator of GFR signaling, is one of the most altered pathways in breast cancer. We thus examined whether deregulated PI3K signaling in luminal ER+ breast tumors is associated with ER level and activity and intrinsic molecular subtype., Methods: We defined two independent molecular signatures of the PI3K pathway: a proteomic (reverse-phase proteomic array) PI3K signature, based on protein measurement for PI3K signaling intermediates, and a PI3K transcriptional (mRNA) signature based on the set of genes either induced or repressed by PI3K inhibitors. By using these signatures, we scored each ER+ breast tumor represented in multiple independent expression-profiling datasets (four mRNA, n = 915; one protein, n = 429) for activation of the PI3K pathway. Effects of PI3K inhibitor BEZ-235 on ER expression and activity levels and cell growth were tested by quantitative real-time PCR and cell proliferation assays., Results: Within ER+ tumors, ER levels were negatively correlated with the PI3K activation scores, both at the proteomic and transcriptional levels, in all datasets examined. PI3K signature scores were also higher in ER+ tumors and cell lines of the more aggressive luminal B molecular subtype versus those of the less aggressive luminal A subtype. Notably, BEZ-235 treatment in four different ER+ cell lines increased expression of ER and ER target genes including PR, and treatment with IGF-I (which signals via PI3K) decreased expression of ER and target genes, thus further establishing an inverse functional relation between ER and PI3K. BEZ-235 had an additional effect on tamoxifen in inhibiting the growth of a number of ER+ cell lines., Conclusions: Our data suggest that luminal B tumors have hyperactive GFR/PI3K signaling associated with lower ER levels, which has been correlated with resistance to endocrine therapy. Targeting PI3K in these tumors might reverse loss of ER expression and signaling and restore hormonal sensitivity.

Background: The 21-gene recurrence score assay is prognostic for women with node-negative, oestrogen-receptor-positive breast cancer treated with tamoxifen. A low recurrence score predicts little benefit of chemotherapy. For node-positive breast cancer, we investigated whether the recurrence score was prognostic in women treated with tamoxifen alone and whether it identified those who might not benefit from anthracycline-based chemotherapy, despite higher risks of recurrence., Methods: The phase 3 trial SWOG-8814 for postmenopausal women with node-positive, oestrogen-receptor-positive breast cancer showed that chemotherapy with cyclophosphamide, doxorubicin, and fluorouracil (CAF) before tamoxifen (CAF-T) added survival benefit to treatment with tamoxifen alone. Optional tumour banking yielded specimens for determination of recurrence score by RT-PCR. In this retrospective analysis, we assessed the effect of recurrence score on disease-free survival by treatment group (tamoxifen vs CAF-T) using Cox regression, adjusting for number of positive nodes., Findings: There were 367 specimens (40% of the 927 patients in the tamoxifen and CAF-T groups) with sufficient RNA for analysis (tamoxifen, n=148; CAF-T, n=219). The recurrence score was prognostic in the tamoxifen-alone group (p=0.006; hazard ratio [HR] 2.64, 95% CI 1.33-5.27, for a 50-point difference in recurrence score). There was no benefit of CAF in patients with a low recurrence score (score <18; log-rank p=0.97; HR 1.02, 0.54-1.93), but an improvement in disease-free survival for those with a high recurrence score (score > or =31; log-rank p=0.033; HR 0.59, 0.35-1.01), after adjustment for number of positive nodes. The recurrence score by treatment interaction was significant in the first 5 years (p=0.029), with no additional prediction beyond 5 years (p=0.58), although the cumulative benefit remained at 10 years. Results were similar for overall survival and breast-cancer-specific survival., Interpretation: The recurrence score is prognostic for tamoxifen-treated patients with positive nodes and predicts significant benefit of CAF in tumours with a high recurrence score. A low recurrence score identifies women who might not benefit from anthracycline-based chemotherapy, despite positive nodes., Funding: National Cancer Institute and Genomic Health., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

Background: Tamoxifen is standard adjuvant treatment for postmenopausal women with hormone-receptor-positive breast cancer. We assessed the benefit of adding chemotherapy to adjuvant tamoxifen and whether tamoxifen should be given concurrently or after chemotherapy., Methods: We undertook a phase 3, parallel, randomised trial (SWOG-8814, INT-0100) in postmenopausal women with hormone-receptor-positive, node-positive breast cancer to test two major objectives: whether the primary outcome, disease-free survival, was longer with cyclophosphamide, doxorubicin, and fluorouracil (CAF) given every 4 weeks for six cycles plus 5 years of daily tamoxifen than with tamoxifen alone; and whether disease-free survival was longer with CAF followed by tamoxifen (CAF-T) than with CAF plus concurrent tamoxifen (CAFT). Overall survival and toxicity were predefined, important secondary outcomes for each objective. Patients in this open-label trial were randomly assigned by a computer algorithm in a 2:3:3 ratio (tamoxifen:CAF-T:CAFT) and analysis was by intention to treat of eligible patients. Groups were compared by stratified log-rank tests, followed by Cox regression analyses adjusted for significant prognostic factors. This trial is registered with ClinicalTrials.gov, number NCT00929591., Findings: Of 1558 randomised women, 1477 (95%) were eligible for inclusion in the analysis. After a maximum of 13 years of follow-up (median 8.94 years), 637 women had a disease-free survival event (tamoxifen, 179 events in 361 patients; CAF-T, 216 events in 566 patients; CAFT, 242 events in 550 patients). For the first objective, therapy with the CAF plus tamoxifen groups combined (CAFT or CAF-T) was superior to tamoxifen alone for the primary endpoint of disease-free survival (adjusted Cox regression hazard ratio [HR] 0.76, 95% CI 0.64-0.91; p=0.002) but only marginally for the secondary endpoint of overall survival (HR 0.83, 0.68-1.01; p=0.057). For the second objective, the adjusted HRs favoured CAF-T over CAFT but did not reach significance for disease-free survival (HR 0.84, 0.70-1.01; p=0.061) or overall survival (HR 0.90, 0.73-1.10; p=0.30). Neutropenia, stomatitis, thromboembolism, congestive heart failure, and leukaemia were more frequent in the combined CAF plus tamoxifen groups than in the tamoxifen-alone group., Interpretation: Chemotherapy with CAF plus tamoxifen given sequentially is more effective adjuvant therapy for postmenopausal patients with endocrine-responsive, node-positive breast cancer than is tamoxifen alone. However, it might be possible to identify some subgroups that do not benefit from anthracycline-based chemotherapy despite positive nodes., Funding: National Cancer Institute (US National Institutes of Health)., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Purpose: Myeloperoxidase (MPO) generates reactive oxygen species and also activates xenobiotics. In a rigorous clinical trial (Southwest Oncology Group SWOG-8897), we examined relationships between genotypes and disease-free survival (DFS) among women treated for breast cancer, as well as those who did not receive adjuvant chemotherapy., Patients and Methods: Patients were assigned to risk groups according to standard prognostic features; the low-risk group (n = 753 genotyped) received follow-up only, and the high-risk group (n = 401 genotyped) was randomly assigned to adjuvant cyclophosphamide, methotrexate, and fluorouracil (CMF) or cyclophosphamide, doxorubicin, and fluorouracil (CAF), with or without tamoxifen. DNA from archived normal lymph node tissue was genotyped, and Cox proportional hazard models were used to calculate DFS associated with MPO genotypes., Results: Among women in the treatment arm, those with MPO G alleles had more than a two-fold reduction in hazard of recurrence (adjusted hazard ratio [HR] for GA genotypes, 0.51; 95% CI, 0.21 to 0.99; HR for GG genotypes, 0.41; 95% CI, 0.21 to 0.77). Effects were greatest among women who were further randomly assigned to tamoxifen (HR for GA genotypes, 0.28; 95% CI, 0.12 to 0.69; HR for GG genotypes, 0.19; 95% CI, 0.08 to 0.45). There were no significant associations between genotypes and DFS among women in the untreated arm, and relationships between genotypes and DFS did not differ by CAF or CMF., Conclusion: These results, observed in two independent study populations, indicate that high-activity MPO genotypes are associated with better survival among women receiving cyclophosphamide-containing therapy, particularly when followed by tamoxifen therapy. MPO can be inhibited and/or upregulated by commonly used drugs; thus, our findings merit further investigation for optimization of therapeutics for breast cancer.

Purpose: Numerous chemotherapeutic agents are cytotoxic through generation of reactive species, and variability in genes related to oxidative stress may influence disease-free survival (DFS). We examined relationships between DFS and variants in NOS3, as well as NQO1, NQO2, and CBR3, among treated and untreated breast cancer patients in a Southwest Oncology Group clinical trial (S8897)., Experimental Design: In the parent trial, women were assigned according to prognostic features; the high-risk group was randomized to cyclophosphamide, i.v. methotrexate, and 5-fluorouracil or to cyclophosphamide, i.v. doxorubicin, and 5-fluorouracil +/- tamoxifen, and the low-risk group did not receive adjuvant therapy. We extracted DNA from normal lymph node tissue and examined functional polymorphisms in NOS3, NQO1, NQO2, and CBR3, in relation to DFS, using Cox proportional hazard model., Results: There were significant interactions between DFS, adjuvant therapy, and NOS3 Glu298Asp and -786 polymorphisms, alone and in combination (P for interaction = 0.008). When NOS3 genotypes were combined, women with genotypes encoding for lower nitric oxide who received chemotherapy had a >2-fold increase in hazard of progression (hazard ratio, 2.32; 95% confidence interval, 1.26-4.25), whereas there was reduced risk for those who did not receive adjuvant therapy (hazard ratio, 0.42; 95% confidence interval, 0.19-0.95). There were no associations between the other genotypes and DFS in either group., Conclusion: Variants encoding lower activity of NOS3 may affect outcomes in breast cancer patients, with the direction of risk differing depending on chemotherapy status. These results may mirror the known dual functions of nitric oxide and nitric oxide synthase, depending on oxidative environment.

Lapatinib, a selective orally available inhibitor of epidermal growth factor receptor (EGFR) and ErbB2 receptor tyrosine kinases, is a promising agent for the treatment of breast cancer. We examined the effect of lapatinib on the development of mammary tumors in MMTV-erbB2 transgenic mice, which express wild-type ErbB2 under the control of the mouse mammary tumor virus promoter and spontaneously develop estrogen receptor (ER)-negative and ErbB2-positive mammary tumors by 14 months of age. Mice were treated from age 3 months to age 15 months with vehicle (n = 17) or lapatinib (30 or 75 mg/kg body weight; n = 16 mice per group) by oral gavage twice daily (6 d/wk). All statistical tests were two-sided. By 328 days after the start of treatment, all 17 (100%) of the vehicle-treated mice vs five (31%) of the 16 mice treated with high-dose lapatinib developed mammary tumors (P < .001). Among MMTV-erbB2 mice treated for 5 months (n = 20 mice per group), those treated with lapatinib had fewer premalignant lesions and noninvasive cancers in their mammary glands than those treated with vehicle (P = .02). Lapatinib also effectively blocked epidermal growth factor-induced signaling through the EGFR and ErbB2 receptors, suppressed cyclin D1 and epiregulin mRNA expression, and stimulated p27 mRNA expression in human mammary epithelial cells and in mammary epithelial cells from mice treated for 5 months with high-dose lapatinib. Thus, cyclin D1, epiregulin, and p27 may represent useful biomarkers of lapatinib response in patients. These data suggest that lapatinib is a promising agent for the prevention of ER-negative breast cancer.

The effectiveness of therapies targeting specific pathways in breast cancer, such as the estrogen receptor or HER2, is limited because many tumors manifest resistance, either de novo or acquired, during the course of treatment. To investigate molecular mechanisms of resistance, we used two xenograft models of estrogen receptor-positive (ER+) breast cancer, one with and one without HER2 overexpression (MCF7/HER2-18 and MCF7 wt, respectively). Mice with established tumors were assigned to the following treatment groups: estrogen supplementation (E2), estrogen deprivation (ED), ED plus tamoxifen (Tam), all with or without the epidermal growth factor receptor tyrosine kinase inhibitor gefitinib (G). Another group received ED plus the antiestrogen fulvestrant (MCF7 wt only). Tumors with acquired or de novo resistance to these endocrine therapies were profiled for gene expression and compared with tumors in the E2 control group. One class of genes underexpressed in endocrine-resistant tumors (relative to E2-treated tumors) were estrogen inducible in vitro and associated with ER+ human breast cancers (luminal subtype). Another class of genes overexpressed in tumors with acquired resistance in both models represented transcriptional targets of HER2 signaling and was associated with ER-/HER2+ human cancers (ERBB2+ subtype). A third class of genes overexpressed in MCF7/HER2-18 tumors exhibiting de novo resistance to tamoxifen was associated with ER+ human cancers but not with estrogen-regulated genes. Thus, in response to various endocrine therapy regimens, these xenograft breast tumors shut down classic estrogen signaling and activate alternative pathways such as HER2 that contribute to treatment resistance. Over time, the molecular phenotype of breast cancer can change.

Background: Tumorigenic breast cancer cells that express high levels of CD44 and low or undetectable levels of CD24 (CD44(>)/CD24(>/low)) may be resistant to chemotherapy and therefore responsible for cancer relapse. These tumorigenic cancer cells can be isolated from breast cancer biopsies and propagated as mammospheres in vitro. In this study, we aimed to test directly in human breast cancers the effect of conventional chemotherapy or lapatinib (an epidermal growth factor receptor [EGFR]/HER2 pathway inhibitor) on this tumorigenic CD44(>) and CD24(>/low) cell population., Methods: Paired breast cancer core biopsies were obtained from patients with primary breast cancer before and after 12 weeks of treatment with neoadjuvant chemotherapy (n = 31) or, for patients with HER2-positive tumors, before and after 6 weeks of treatment with the EGFR/HER2 inhibitor lapatinib (n = 21). Single-cell suspensions established from these biopsies were stained with antibodies against CD24, CD44, and lineage markers and analyzed by flow cytometry. The potential of cells from biopsy samples taken before and after treatment to form mammospheres in culture was compared. All statistical tests were two-sided., Results: Chemotherapy treatment increased the percentage of CD44(>)/CD24(>/low) cells (mean at baseline vs 12 weeks, 4.7%, 95% confidence interval [CI] = 3.5% to 5.9%, vs 13.6%, 95% CI = 10.9% to 16.3%; P < .001) and increased mammosphere formation efficiency (MSFE) (mean at baseline vs 12 weeks, 13.3%, 95% CI = 6.0% to 20.6%, vs 53.2%, 95% CI = 42.4% to 64.0%; P < .001). Conversely, lapatinib treatment of patients with HER2-positive tumors led to a non-statistically significant decrease in the percentage of CD44(>)/CD24(>/low) cells (mean at baseline vs 6 weeks, 10.0%, 95% CI = 7.2% to 12.8%, vs 7.5%, 95% CI = 4.1% to 10.9%) and a statistically non-significant decrease in MSFE (mean at baseline vs 6 weeks, 16.1%, 95% CI = 8.7% to 23.5%, vs 10.8%, 95% CI = 4.0% to 17.6%)., Conclusion: These studies provide clinical evidence for a subpopulation of chemotherapy-resistant breast cancer-initiating cells. Lapatinib did not lead to an increase in these tumorigenic cells, and, in combination with conventional therapy, specific pathway inhibitors may provide a therapeutic strategy for eliminating these cells to decrease recurrence and improve long-term survival.

Breast cancer evolution and tumor progression are governed by the complex interactions between steroid receptor [estrogen receptor (ER) and progesterone receptor] and growth factor receptor signaling. In recent years, the field of cancer therapy has witnessed the emergence of multiple strategies targeting these specific cancer pathways and key molecules (ER and growth factor receptors) to arrest tumor growth and achieve tumor eradication; treatment success, however, has varied and both de novo (up front) and acquired resistance have proven a challenge. Recent studies of ER biology have revealed new insights into ER action in breast cancer and have highlighted the role of an intimate crosstalk between the ER and HER family signaling pathways as a fundamental contributor to the development of resistance to endocrine therapies against the ER pathway. The aim of this review article is to summarize the current knowledge on mechanisms of resistance of breast cancer cells to endocrine therapies due to the crosstalk between the ER and the HER growth factor receptor signaling pathways and to explore new available therapeutic strategies that could prolong duration of response and circumvent endocrine resistant tumor growth.

Previously, we had identified gene expression patterns that predicted response to neoadjuvant docetaxel. Other studies have validated that a high Recurrence Score (RS) by the 21-gene RT-PCR assay is predictive of worse prognosis but better response to chemotherapy. We investigated whether tumor expression of these 21 genes and other candidate genes can predict response to docetaxel. Core biopsies from 97 patients were obtained before treatment with neoadjuvant docetaxel (4 cycles, 100 mg/m2 q3 weeks). Three 10-microm FFPE sections were submitted for quantitative RT-PCR assays of 192 genes that were selected from our previous work and the literature. Of the 97 patients, 81 (84%) had sufficient invasive cancer, 80 (82%) had sufficient RNA for QRTPCR assay, and 72 (74%) had clinical response data. Mean age was 48.5 years, and the median tumor size was 6 cm. Clinical complete responses (CR) were observed in 12 (17%), partial responses in 41 (57%), stable disease in 17 (24%), and progressive disease in 2 patients (3%). A significant relationship (P<0.05) between gene expression and CR was observed for 14 genes, including CYBA. CR was associated with lower expression of the ER gene group and higher expression of the proliferation gene group from the 21 gene assay. Of note, CR was more likely with a high RS (P=0.008). We have established molecular profiles of sensitivity to docetaxel. RT-PCR technology provides a potential platform for a predictive test of docetaxel chemosensitivity using small amounts of routinely processed material.

Not all breast cancers respond to tamoxifen, and many develop resistance despite initial benefit. We used an in vivo model of estrogen receptor (ER)-positive breast cancer (MCF-7 xenografts) to investigate mechanisms of this resistance and develop strategies to circumvent it. Epidermal growth factor receptor (EGFR) and HER2, which were barely detected in control estrogen-treated tumors, increased slightly with tamoxifen and were markedly increased when tumors became resistant. Gefitinib, which inhibits EGFR/HER2, improved the antitumor effect of tamoxifen and delayed acquired resistance, but had no effect on estrogen-stimulated growth. Phosphorylated levels of p42/44 and p38 mitogen-activated protein kinases (both downstream of EGFR/HER2) were increased in the tamoxifen-resistant tumors and were suppressed by gefitinib. There was no apparent increase in phosphorylated AKT (also downstream of EGFR/HER2) in resistant tumors, but it was nonetheless suppressed by gefitinib. Phosphorylated insulin-like growth factor-IR (IGF-IR), which can interact with both EGFR and membrane ER, was elevated in the tamoxifen-resistant tumors compared with the sensitive group. However, ER-regulated gene products, including total IGF-IR itself and progesterone receptor, remained suppressed even at the time of acquired resistance. Tamoxifen's antagonism of classic ER genomic function was retained in these resistant tumors and even in tumors that overexpress HER2 (MCF-7 HER2/18) and are de novo tamoxifen-resistant. In conclusion, EGFR/HER2 may mediate tamoxifen resistance in ER-positive breast cancer despite continued suppression of ER genomic function by tamoxifen. IGF-IR expression remains dependent on ER but is activated in the tamoxifen-resistant tumors. This study provides a rationale to combine HER inhibitors with tamoxifen in clinical studies, even in tumors that do not initially overexpress EGFR/HER2.

The purpose of this study was to examine relationships among self-blame for developing breast cancer, a self-forgiving attitude, mood, and quality of life among women with breast cancer. In this cross-sectional study, 123 women with Stages 0-III breast cancer completed questionnaires measuring demographic and medical characteristics, self-blame, self-forgiveness, mood, and quality of life. Women who blamed themselves reported more mood disturbance (p

Background: Human epidermal growth factor receptor 2 (HER2) is a member of the HER signaling pathway. HER inhibitors partially block HER signaling and tumor growth in preclinical breast cancer models. We investigated whether blockade of all HER homo- and heterodimer pairs by combined treatment with several inhibitors could more effectively inhibit tumor growth in such models., Methods: Mice carrying xenograft tumors of HER2-overexpressing MCF7/HER2-18 (HER2-transfected) or BT474 (HER2-amplified) cells were treated with estrogen supplementation or estrogen withdrawal, alone or combined with tamoxifen. One to three HER inhibitors (pertuzumab, trastuzumab, or gefitinib) could also be added (n > or = 8 mice per group). Tumor volumes, HER signaling, and tumor cell proliferation and apoptosis were assessed. Results were analyzed with the t test or Wilcoxon rank sum test and survival analysis methods. All statistical tests were two-sided., Results: Median time to tumor progression was 21 days for mice receiving estrogen and 28 days for mice receiving estrogen and pertuzumab (difference = 7 days; P = .001; hazard ratio [HR] of progression in mice receiving estrogen and pertuzumab versus mice receiving estrogen = 0.27, 95% confidence interval [CI] = 0.09 to 0.77). Addition of gefitinib and trastuzumab to estrogen and pertuzumab increased this time to 49 days (difference = 21 days; P = .004; HR of progression = 0.28, 95% CI = 0.10 to 0.76). MCF7/HER2-18 tumors disappeared completely and did not progress (for > or = 189 days) after combination treatment with pertuzumab, trastuzumab, and gefitinib plus tamoxifen (19 of 20 mice) or plus estrogen withdrawal (14 of 15 mice). Both combination treatments induced apoptosis and blocked HER signaling and proliferation in tumor cells better than any single agent or dual combination. All BT474 tumors treated with pertuzumab, trastuzumab, and gefitinib disappeared rapidly, regardless of endocrine therapy, and no tumor progression was observed for 232 days., Conclusion: Combined treatment with gefitinib, trastuzumab, and pertuzumab to block signals from all HER homo- and heterodimers inhibited growth of HER2-overexpressing xenografts statistically significantly better than single agents and dual combinations.

Objective: The objective of this multicenter phase III trial was to study the impact on time to treatment failure (TTF) and survival of cyclophosphamide, Adriamycin, and 5-fluorouracil (CAF) versus CAF/thiotepa, Adriamycin, vinblastine, and Halotestin (TsAVbH), a partially noncross-resistant regimen used in a rotating schedule in the treatment of hormone insensitive metastatic breast cancer in accordance with the Goldie and Coldman hypothesis., Methods: Three hundred forty-three patients received 6 cycles of induction treatment with one of 2 regimens. Patients with estrogen receptor-negative tumors or those with estrogen receptor-positive or estrogen receptor-unknown tumors with demonstrated unresponsiveness to hormone treatment were eligible. Complete responders were randomized to either observation or maintenance therapy with cyclophosphamide, methotrexate, 5-fluorouracil, prednisone, tamoxifen, and Halotestin (CMF[P]TH). Patients with partial response or stable disease on completion of induction therapy were maintained on CMF plus Halotestin., Results: There were no differences in the primary end point of TTF (median 7.3 and 7.4 months, respectively). There was a significant difference in TTF and survival by duration of disease-free interval: a median of 8.8 and 21.2 months for those with a disease-free interval of > or =2 years versus 6 to 8 and 13.3 months for those with a disease-free interval <2 years (P = 0.016 and <0.001), respectively. Toxicity of the 2 treatment regimens was similar., Conclusion: There were no differences observed in TTF, survival, and toxicities between the 2 treatment arms, both of which contained doxorubicin (Adriamycin) as the most active agent. The results of observation versus maintenance in complete responders were reported separately.

Purpose: We conducted a phase III randomized study of two adjuvant treatment schedules of doxorubicin (A) and cyclophosphamide (C) in early-stage breast cancer to determine if administration of sequential single agents (A --> C) results in superior disease-free survival (DFS) and overall survival (OS) versus the same total dose given in combination (AC)., Patients and Methods: High-risk node-negative or low-risk node-positive breast cancer patients received AC given: (arm I) concurrently (AC) doxorubicin 54 mg/m2 and cyclophosphamide 1.2 g/m2 intravenously (IV) every 3 weeks for six cycles; or (arm II) in sequence (A C) doxorubicin 40.5 mg/m2 IV days 1 and 2 every 3 weeks for four cycles followed by cyclophosphamide 2.4 gm/m2 IV every 2 weeks for three cycles. Total dose and duration were identical, but the intensity of each drug was increased on A C. Both arms included granulocyte colony-stimulating factor support and prophylactic antibiotics. All but premenopausal women with receptor negative tumors received tamoxifen after chemotherapy., Results: Between 1994 and 1997, 3,176 patients were randomly assigned. Arms were well balanced; 48% of eligible patients were node-negative and 48% were estrogen receptor-positive. No significant differences in OS or DFS were observed; 5-year estimates of OS (95% CI) were 88% (87% to 90%) on AC and 89% (87% to 91%) on A --> C. Grade 4 hematologic toxicity was greater on A --> C, but nonhematological grade 4 was similar., Conclusion: The overall result does not support superiority of dose-intense sequenced single agents. The greater toxicity of higher doses of single agents does not support their sequential use.

A serious obstacle to successful treatment of estrogen receptor (ER)-positive human breast cancer is cell resistance to tamoxifen (TAM) therapy. Here we show that the electrophile disulfide benzamide (DIBA), an ER zinc finger inhibitor, blocks ligand-dependent and -independent cell growth of TAM-resistant breast cancer in vitro and in vivo. Such inhibition depends on targeting disruption of the ER DNA-binding domain and its communication with neighboring functional domains, facilitating ERalpha dissociation from its coactivator AIB1 and concomitant association with its corepressor NCoR bound to chromatin. DIBA does not affect phosphorylation of HER2, MAPK, AKT, and AIB1, suggesting that DIBA-modified ERalpha may induce a switch from agonistic to antagonistic effects of TAM on resistant breast cancer cells.

Purpose: We previously identified three genes, HOXB13, IL17BR and CHDH, and the HOXB13:IL17BR ratio index in particular, that strongly predicted clinical outcome in breast cancer patients receiving tamoxifen monotherapy. Confirmation in larger independent patient cohorts was needed to fully validate their clinical utility., Patients and Methods: Expression of HOXB13, IL17BR, CHDH, estrogen receptor (ER) and progesterone receptor (PR) were quantified by real-time polymerase chain reaction in 852 formalin-fixed, paraffin-embedded primary breast cancers from 566 untreated and 286 tamoxifen-treated breast cancer patients. Gene expression and clinical variables were analyzed for association with relapse-free survival (RFS) by Cox proportional hazards regression models., Results: ER and PR mRNA measurements were in close agreement with immunohistochemistry. In the entire cohort, expression of HOXB13 was associated with shorter RFS (P = .008), and expression of IL17BR and CHDH was associated with longer RFS (P < .0001 for IL17BR and P = .0002 for CHDH). In ER+ patients, the HOXB13:IL17BR index predicted clinical outcome independently of treatment, but more strongly in node-negative patients. In multivariate analysis of the ER+ node-negative subgroup including age, PR status, tumor size, S phase fraction, and tamoxifen treatment, the two-gene index remained a significant predictor of RFS (hazard ratio = 3.9; 95% CI, 1.5 to 10.3; P = .007)., Conclusion: This tumor bank study demonstrated HOXB13:IL17BR index is a strong independent prognostic factor for ER+ node-negative patients irrespective of tamoxifen therapy.

HER-2/neu in breast cancer is associated with tamoxifen resistance, but little data exist on its interaction with estrogen deprivation or fulvestrant. Here, we used an in vivo xenograft model of estrogen receptor (ER)-positive breast cancer with HER-2/neu overexpression (MCF7/HER-2/neu-18) to investigate mechanisms of growth inhibition and treatment resistance. MCF7/HER-2/neu-18 tumors were growth inhibited by estrogen deprivation and with fulvestrant, but resistance developed in 2 to 3 months. Inhibited tumors had reductions in ER, insulin-like growth factor-I receptor (IGF-IR), phosphorylated HER-2/neu (p-HER-2/neu), and phosphorylated p42/44 mitogen-activated protein kinase (p-MAPK). p27 was increased especially in tumors sensitive to estrogen deprivation. Tumors with acquired resistance to these therapies had complete loss of ER, increased p-HER-2/neu, increased p-MAPK, and reduced p27. In contrast, IGF-IR and phosphorylated AKT (p-AKT) levels were markedly reduced in these resistant tumors. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib, which can block EGFR/HER-2/neu signaling, significantly delayed the emergence of resistance to both estrogen deprivation and fulvestrant. Levels of p-MAPK and p-AKT decreased with gefitinib, whereas high ER levels were restored. Eventually, however, tumors progressed in mice treated with gefitinib combined with estrogen deprivation or fulvestrant accompanied again by loss of ER and IGF-IR, increased p-HER-2/neu, high p-MAPK, and now increased p-AKT. Thus, estrogen deprivation and fulvestrant can effectively inhibit HER-2/neu-overexpressing tumors but resistance develops quickly. EGFR/HER-2/neu inhibitors can delay resistance, but reactivation of HER-2/neu and signaling through AKT leads to tumor regrowth. Combining endocrine therapy with EGFR/HER-2/neu inhibitors should be tested in clinical breast cancer, but a more complete blockade of EGFR/HER-2/neu may be optimal.

Mammary gland development is dependent upon the growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis, this same axis has also been implicated in breast cancer progression. In this study we investigated the effect of a GH antagonist, pegvisomant (Somavert, Pfizer), on normal mammary gland development and breast cancer xenograft growth. Intraperitoneal administration of pegvisomant resulted in a 60% suppression of hepatic IGF-I mRNA levels and upto a 70-80% reduction of serum IGF-I levels. Pegvisomant administration to virgin female mice caused a significant delay of mammary ductal outgrowth that was associated with a decrease in the number of terminal end buds and reduced branching and complexity of the gland. This effect of pegvisomant was mediated by a complete inhibition of both GH and IGF-IR-mediated signaling within the gland. In breast cancer xenograft studies, pegvisomant caused shrinkage of MCF-7 xenografts, with an initial 30% reduction in tumor volume, which was associated with a 2-fold reduction in proliferation and a 2-fold induction of apoptosis. Long-term growth inhibition of MCF-7 xenografts was noted. In contrast, pegvisomant had no effect on MDA-231 or MDA-435 xenografts, consistent with primary growth of these xenografts being unresponsive to IGF-I both in vitro and in vivo. In MCF-7 xenografts that regressed, pegvisomant had only minor effects upon GHR and IGF-IR signaling. This data supports previous studies indicating a role for GH/IGF in mammary gland development, and suggests that pegvisomant maybe useful for the prevention and/or treatment of estrogen receptor positive breast cancer.

Purpose: Subset analysis from the Arimidex, Tamoxifen, Alone or in Combination trial, a major adjuvant therapy trial, suggests that progesterone receptor-negative (PR-) cases may derive greater benefit from aromatase inhibitor compared with tamoxifen than PR+ cases. We postulated that estrogen receptor-positive (ER+)/PR+ patients might do as well or better by starting on tamoxifen and later switching to an aromatase inhibitor rather than by starting on an aromatase inhibitor as initial therapy., Experimental Design: We constructed a computer model using retrospective data to approximate exponential failure rates for PR+ and PR- in tamoxifen-treated and tamoxifen-untreated patients, adding the assumptions that about half of patients are cured at surgery and that approximately 20% of postmenopausal ER+ early breast cancer cases are PR-. This model provided a very good approximation to the published overview data and to the clinical trials. We then used the failure rates to generate relapse times for a large number of cases (n = 50,000) for each treatment scenario., Results: In PR- cases, initial therapy with an aromatase inhibitor is superior to tamoxifen and this advantage can never be made up by switching. In PR+ cases, tamoxifen is only modestly inferior to aromatase inhibitor at the outset, and after switching to an aromatase inhibitor at 3 or 5 years the tamoxifen relapse-free survival curve catches up and then begins to surpass the aromatase inhibitor curve at 7.5 or 12 years, respectively., Discussion: Although our in silico trial is based on many assumptions, it closely approximates results of the published trials and, therefore, suggests that an in vivo comparison in ER+/PR+ patients of aromatase inhibitor versus tamoxifen followed by aromatase inhibitor may be worth considering.

Introduction: Doxorubicin and cyclophosphamide (Adriamycin/cytoxan, AC) is a standard chemotherapy regimen for breast cancer, but de novo resistance is frequent. We hypothesized that gene expression profiles predictive of AC response may be different from our previously published patterns with docetaxel., Methods: Core biopsies from 40 patients were obtained before treatment with AC (6 cycles, 60/600 mg/m2q3 weeks), and clinical responses recorded after treatment. Gene expression patterns were analyzed using Affymetrix U133A chips which comprise approximately 22,200 genes., Results: Clinical complete responses (cCR) were observed in 22, partial responses in 7, stable disease in 11 patients. Differential expression between sensitive cCR and resistant tumors with a low false discovery rate (< 5%) was obtained. Of these 253 differentially expressed genes, pathways up-regulated in sensitive tumors included cell cycle (BUB3, CDKN1B), survival (BCL2, BAG1, BIRC1, STK39), stress response (CYP2B6, MAPK14), and estrogen-related pathways (ER, IRS1). Resistant tumors expressed gene promoting transcription (GTF3C1, ILF3), differentiation (ST14, CTNNBIP1), signal transduction (EIF1AX, EIF4EBP1), and amino acid metabolism (SRM, PLOD1, PLOD3). With leave-one-out cross validation, 67% of the samples were correctly classified, with a permutation p-value of 0.4. The previously published 92-gene molecular portrait for docetaxel sensitivity could not discriminate AC sensitivity and resistance., Conclusions: This preliminary study supports that molecular profiles for AC response are likely to exist, with unique expression patterns for individual chemotherapy regimens. Larger validation studies are necessary to define and refine patterns for different agents.

Activity of the estrogen receptor (ER) is regulated through interaction with coactivators and corepressors. These proteins are present in large complexes, suggesting functional interactions among various cofactors. Scaffold attachment factors B1 and B2 (SAFB1/2) and nuclear receptor corepressor (N-CoR) function as ERalpha corepressors--they directly interact with ERalpha, and repress transcription via repression domains. We asked the question whether SAFB1/2 and N-CoR could directly interact with each other, and whether this interaction results in altered repressive activities. Employing coimmunoprecipitation, cofractionation, and colocalization experiments, we have shown that SAFB1/2 interact with the nuclear receptor corepressor N-CoR. This interaction was direct, and was mediated in vitro and in vivo through the C-terminal region of SAFB1 (amino acids 600-915 and the N-terminal region of N-CoR (amino acids 1-373)). Decrease of SAFB1 or N-CoR expression by small interfering RNA resulted in an increase of the estrogen response in reporter assays, confirming prior data that both proteins are attenuating estrogen-mediated induction of genes. Importantly, the effect of SAFB1 on this attenuation was significantly decreased in the presence of N-CoR small interfering RNA. Using chromatin immunoprecipitation assays, we observed that SAFB1/2 and N-CoR were recruited to the pS2 promoter in the absence of estrogen, and this recruitment was enhanced in the presence of Tamoxifen. Detailed kinetic studies showed that the addition of estrogen resulted in the concurrent release of SAFB1/2 and N-CoR from the promoter. Finally, we measured expression of SAFB1/2 and N-CoR in 289 clinical breast cancer specimens, and detected a strong and highly significant correlation between their expression levels. Taken together, our studies demonstrate that SAFB1/2 and N-CoR interact, and that this interaction is, at least in part, necessary for SAFB1's repressive activities. The coexpression of these proteins in breast cancer specimens, and the combined recruitment (and release) of SAFB1/2 and N-CoR furthermore suggests that this interaction has functional relevance.

Nuclear metastasis-associated 1(MTA1) protein is an estrogen receptor co-repressor that regulates transcription via chromatin remodeling, and MTA1 messenger ribonucleic acid (mRNA) levels are elevated in several kinds of locally advanced and metastatic tumors relative to non-metastatic tumors. Previous studies in our laboratory mapped MTA1 into a region showing significantly lower LOH (loss of heterozygosity) in primary breast cancers with metastases compared to node-negative tumors, suggesting that epigenetic alterations of MTA1 affect metastatic potential. The present study examined immunohistochemical expression of the MTA1 protein in treated and untreated primary human breast cancers to study the relationship between MTA1 expression and clinical outcome. Node-negative tumors that overexpress MTA1 protein had recurrence risks similar to node-positive tumors. In multivariate analysis of untreated node-negative tumors, highest expression of MTA1 was associated with increased relapse risk (hazard ratio (HR)=2.72, p=0.0003 for multivariate analysis). Tamoxifen and/or anthracylcene-based chemotherapies eliminated all MTA1 associations with clinical outcome, suggesting MTA1 overexpression predicts early disease relapse, but sensitizes breast tumors to systemic therapies.

The receptor for the female hormone progesterone (PR), like that for estrogen (ER), is an important predictive marker for response to endocrine therapy in patients with breast cancer. PR exists as two isoforms, A and B. PR is important in mammary gland development and excess production of PRB is associated with breast cancer risk. Overabundance of PRA is related to resistance to tamoxifen. Total loss of PR is linked to reduced benefit from tamoxifen in both the adjuvant and metastatic settings. The predictive significance of PR expression was originally explained on the basis that PR is an ER-regulated gene and its presence indicates a functioning ER pathway and, therefore, an endocrine-responsive tumor. More recent data, however, suggest an alternative explanation. While many studies show that loss of PR predicts relative resistance to the antiestrogen tamoxifen, a recent study suggests that PR loss may not indicate resistance to aromatase inhibition. The finding that PR loss may not correlate with resistance to aromatase inhibition may be related to crosstalk between ER and PR and growth factor receptor pathways such as HER2. PR loss in some tumors is due to excessive growth factor receptor signaling (overexpression of HER2), which downregulates expression of the PR gene. Neoadjuvant studies also show that HER2 signaling is associated with tamoxifen resistance, but not resistance to aromatase inhibitors. Therefore, high HER2 signaling could explain both PR loss and resistance to tamoxifen while the response to aromatase inhibitors is maintained. In this way, PR loss in some tumors may be a surrogate marker for increased signaling through the growth factor receptor tyrosine kinase pathway and it may help clinicians decide between initial use of an aromatase inhibitor or tamoxifen in the individual patient.

Prevention trials using incidence or mortality as endpoints require a large number of participants and long follow-up. Trials using biomarkers as endpoints would potentially require fewer participants, less time, and significantly less resources to test promising new agents for breast cancer prevention. To test this idea, a randomized trial of tamoxifen for 1 year versus observation for 1 year was conducted to determine whether tamoxifen can cause regression of hyperplastic breast tissue, whether it changes the biomarker phenotype of premalignant disease or normal breast epithelium, and if biomarkers can be used as early surrogate indicators of response to tamoxifen. Women were identified by having an abnormal mammogram and ductal hyperplasia diagnosed by core needle biopsy. Image-directed needle biopsy was repeated in the same site of the breast after 1 year. Approximately 3000 women were screened, and 265 were eligible. Sixty-three women were randomized and paired biopsies from 45 subjects were available for analysis. There was no evidence of substantial regression of hyperplasia--fewer samples showed hyperplasia at 1 year follow-up, but this was seen in both untreated and tamoxifen-treated women. There were trends for reductions in ER and PgR and trends for increases in bcl-2 in normal and hyperplastic tissue in the tamoxifen-treated arm, though these changes did not reach statistical significance. Proliferation, determined by Ki67 staining, was not significantly changed. Clinical trials of this type are difficult to carry out and modifications in trial design are needed to make this process more efficient.

Purpose: In the adjuvant setting, taxanes modestly improve clinical outcome and survival. The goal of the present study was to define the efficacy of neoadjuvant docetaxel in treatment-naïve large, locally advanced breast cancers and to better understand docetaxel's mechanism of action by evaluating biomarker modulation in response to treatment., Patients and Methods: Fifty-one patients were enrolled. Patients received four cycles of docetaxel (100 mg/m2 q3weeks) followed by surgery and four cycles of doxorubicin and cyclophosphamide (60/600 mg/m2 q3weeks). Radiation and hormonal therapy were given if clinically indicated. Clinical responses were assessed at completion of neoadjuvant docetaxel. Pathological responses were considered complete (pCR) if no tumor cells were identified in the surgical specimen or near complete (npCR) if only occasional scattered tumor cells were seen. Proliferation (Ki-67) and apoptosis (cleaved caspase-3) were measured by IHC in tissue obtained at baseline and at surgery., Results: The median tumor size was 9 cm (range 4-30 cm). Objective response rate was 75% with clinical complete response in 27%, partial response in 48%, and stable disease in 25% of the patients. pCR/npCR was reported in 20% of patients. With a median follow up of 28 months, 98 and 78% of the patients were alive at 12 and 24 months, respectively. Overall survival at 24 months was significantly better in patients who achieved a clinical response, 85 versus 51%, p = 0.008, but pCR/npCR was not a significant predictor of outcome. Apoptosis was induced in clinical responders (p = 0.002), while the proliferation index did not change significantly. In patients who had no clinical response to docetaxel, neither apoptosis nor proliferation changed significantly., Conclusion: Neoadjuvant single agent docetaxel is effective in treating patients with large locally advanced breast cancer and clinical response is associated with improved survival. Docetaxel acts therapeutically by inducing apoptosis and this can be used as a marker of response.

Purpose: We evaluated the efficacy of cyclophosphamide, methotrexate, and fluorouracil (CMF) versus cyclophosphamide, doxorubicin, and fluorouracil (CAF) in node-negative breast cancer patients with and without tamoxifen (TAM), overall and by hormone receptor (HR) status., Patients and Methods: Node-negative patients identified by tumor size (> 2 cm), negative HR, or high S-phase fraction (n = 2,690) were randomly assigned to CMF, CAF, CMF + TAM (CMFT), or CAF + TAM (CAFT). Cox regression evaluated overall survival (OS) and disease-free survival (DFS) for CAF versus CMF and TAM versus no TAM separately. Two-sided CIs and one-sided P values for planned comparisons were calculated., Results: Ten-year estimates indicated that CAF was not significantly better than CMF (P = .13) for the primary outcome of DFS (77% v 75%; HR = 1.09; 95% CI, 0.94 to 1.27). CAF had slightly better OS than CMF (85% v 82%, HR = 1.19 for CMF v CAF; 95% CI, 0.99 to 1.43); values were statistically significant in the planned one-sided test (P = .03). Toxicity was greater with CAF and did not increase with TAM. Overall, TAM had no benefit (DFS, P = .16; OS, P = .37), but the TAM effect differed by HR groups. For HR-positive patients, TAM was beneficial (DFS, HR = 1.32 for no TAM v TAM; 95% CI, 1.09 to 1.61; P = .003; OS, HR = 1.26; 95% CI, 0.99 to 1.61; P = .03), but not for HR-negative patients (DFS, HR = 0.81 for no TAM v TAM; 95% CI, 0.64 to 1.03; OS, HR = 0.79; 95% CI, 0.60 to 1.05)., Conclusion: CAF did not improve DFS compared with CMF; there was a slight effect on OS. Given greater toxicity, we cannot conclude CAF to be superior to CMF. TAM is effective in HR-positive disease, but not in HR-negative disease.

Application of molecular modeling approaches has potential to contribute to rational drug design. These approaches may be especially useful when attempting to elucidate the structural features associated with novel drug targets. In this study, molecular docking and molecular dynamics were applied to studies of inhibition of the human motor protein denoted HsEg5 and other homologues in the BimC subfamily. These proteins are essential for mitosis, so compounds that inhibit their activity may have potential as anticancer therapeutics. The discovery of a small-molecule cell-permeable inhibitor, monastrol, has stimulated research in this area. Interestingly, monastrol is reported to inhibit the human and Xenopus forms of Eg5, but not those from Drosophila and Aspergillus. In this study, homology modeling was used to generate models of the Xenopus, Drosophila, and Aspergillus homologues, using the crystal structure of the human protein in complex with monastrol as a template. A series of known inhibitors was docked into each of the homologues, and the differences in binding energies were consistent with reported experimental data. Molecular dynamics revealed significant changes in the structure of the Aspergillus homologue that may contribute to its relative insensitivity to monastrol and related compounds.

Estrogen receptor (ER), mediating estrogen-signaling stimuli, is a dominant regulator and a key therapeutic target in breast cancer etiology and progression. Endocrine therapy, blocking the ER pathway, is one of the most important systemic therapies in breast cancer management, but de novo and acquired resistance is still a major clinical problem. New research highlights the role of both genomic and nongenomic ER activities and their intimate molecular crosstalk with growth factor receptor and other signaling kinase pathways in endocrine resistance. These signaling pathways, when overexpressed and/or hyperactivated, can modulate both activities of ER, resulting in endocrine resistance. Thus, these signal transduction receptors and signaling molecules may serve as both predictive markers and novel therapeutic targets to circumvent endocrine resistance. Compelling experimental and clinical evidence suggest that the epidermal growth factor/HER2/neu receptor (EGFR/HER2) pathway might play a distinct role in endocrine resistance, and especially in resistance to selective estrogen receptor modulators (SERMs) such as tamoxifen. Results from preclinical studies of treatment combinations with various endocrine therapy drugs together with several potent anti-EGFR/HER2 inhibitors are very promising, and clinical trials to see whether this new strategy is effective in patients are now ongoing.

The response to endocrine therapy in breast cancer correlates with estrogen receptor (ER) and progesterone receptor (PR) status. ER-positive/PR-negative breast cancers respond less well to selective ER modulator (SERM) therapy than ER-positive/PR-positive tumors. The predictive value of PR has long been attributed to the dependence of PR expression on ER activity, with the absence of PR reflecting a nonfunctional ER and resistance to hormonal therapy. However, recent clinical and laboratory evidence suggests that ER-positive/PR-negative breast cancers may be specifically resistant to SERMs, whereas they may be less resistant to estrogen withdrawal therapy with aromatase inhibitors, which is a result inconsistent with the nonfunctional ER theory. Novel alternative molecular mechanisms potentially explaining SERM resistance in ER-positive/PR-negative tumors have been suggested by recent experimental indications that growth factors may downregulate PR levels. Thus, the absence of PR may not simply indicate a lack of ER activity, but rather may reflect hyperactive cross talk between ER and growth factor signaling pathways that downregulate PR even as they activate other ER functions. Therefore, ER-positive/PR-negative breast tumors might best be treated by completely blocking ER action via estrogen withdrawal with aromatase inhibitors, by targeted ER degradation, or by combined therapy targeting both ER and growth factor signaling pathways. In this review, we will discuss the biology and etiology of ER-positive/PR-negative breast cancer, highlighting recent data on molecular cross talk between ER and growth factor signaling pathways and demonstrating how PR might be a useful marker of these activities. Finally, we will consider the clinical implications of these observations.

Purpose: Chemotherapy, tamoxifen, and ovarian ablation/suppression (OA/OS) are effective adjuvant approaches for premenopausal, steroid hormone receptor-positive breast cancer. The value of combined therapy has not been clearly established., Patients and Methods: Premenopausal women with axillary lymph node-positive, steroid hormone receptor-positive breast cancer (1,503 eligible patients) were randomly assigned to six cycles of cyclophosphamide, doxorubicin, and fluorouracil (CAF), CAF followed by 5 years of monthly goserelin (CAF-Z), or CAF followed by 5 years of monthly goserelin and daily tamoxifen (CAF-ZT). The primary end points were time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS) for CAF-Z versus CAF, and CAF-ZT versus CAF-Z., Results: With a median follow-up of 9.6 years, the addition of tamoxifen to CAF-Z improved TTR and DFS but not OS. There was no overall advantage for addition of goserelin to CAF., Conclusion: Addition of tamoxifen to CAF-Z improves outcome for premenopausal node-positive, receptor-positive breast cancer. The role of OA/OS alone or with other endocrine agents should be studied more intensely.

Purpose: To determine whether the hormone receptor status of the primary breast cancer (PBC) is predictive of the hormone receptor status of the subsequent contralateral breast cancer (CBC)., Patients and Methods: We identified patients in our database with known estrogen receptor (ER; n = 193) and/or progesterone receptor (PgR; n = 178) status in their PBC and in their subsequent CBC. One hundred twenty-six of these patients had received no adjuvant therapy, 34 had received adjuvant tamoxifen, and 33 had received adjuvant chemotherapy alone. The median interval between the first diagnosis of PBC and the development of the subsequent CBC was 3 years. ER and PgR assays were assessed biochemically in two central reference laboratories using identical quality-controlled ligand-binding methods., Results: Among systemically untreated patients (n = 126), 88% of patients with ER-positive PBC and 75% of patients with ER-negative PBC developed an ER-positive CBC (P = .11). Among the tamoxifen-treated patients, those with an ER-positive PBC were almost equally likely to develop an ER-positive (47%) or ER-negative (53%) CBC (P = .99). PgR status was similar. In the untreated group (n = 112), 59% of patients with a PgR-positive PBC and 66% with a PgR-negative PBC developed a PgR-positive CBC (P = .48). Among tamoxifen-treated patients (n = 33), 50% of patients with a PgR-positive PBC versus 27% of patients with a PgR-negative PBC developed a PgR-positive CBC (P = .28)., Conclusion: ER and PgR status of the primary tumor does not predict the hormone receptor status of the subsequent CBC in the absence of selective pressure of adjuvant therapy. Thus, other reasons should be considered to clarify the failure of tamoxifen to reduce the incidence of CBC in patients with a receptor-negative PBC.