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Summary

Triple-negative breast cancer (TNBC) is characterized by the lack of estrogen and progesterone receptors and the lack of HER2 expression or amplification. Much interest has recently been focused on these triple-negative (TN) subtypes because they may be aggressive and are more likely to recur and metastasize than other subtypes of breast cancer. TNBC accounts for approximately 10-24% of all breast cancer cases, and typically it occurs in younger patients and in patients with BRCA1 mutation. There is a substantial heterogeneity of TNBCs both at the morphological and the molecular level, but there are also common features, such as low tumor grade and accelerated tumor proliferation. Morphologically, TNBC may present as invasive ductal, metaplastic, medullary, apocrine, or other types. Molecularly, they are most frequently associated with a basal phenotype, but there is a distinct subgroup of cancers that are not of basal type and belong to the claudin-low or molecular-apocrine type. The basal phenotype is frequently associated with the loss of BRCA1.

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer that is clinically defined as lacking estrogen and progesterone receptors, as well as being ERBB2 (HER-2) negative. Without specific therapeutic targets, TNBC carries a worse prognosis than other types of breast cancer in the absence of therapy. Research has now further differentiated breast cancer into subtypes based on genetic expression patterns. One of these subtypes, basal-like, frequently overlaps with the clinical picture of TNBC. Additionally, both TNBC and basal-like breast cancer link to BRCA mutations. Recent pharmaceutical advances have created a class of drugs, poly(ADP-ribose) polymerase (PARP) inhibitors, which are showing potential to effectively treat these patients. The aim of this paper is to summarize the basis behind PARP inhibitors and update the current status of their development in clinical trials for the treatment of TNBC.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with a high rate of proliferation and metastasis, as well as poor prognosis for advanced-stage disease. Although TNBC was previously classified together with basal-like and BRCA1/2-related breast cancers, genomic profiling now shows that there is incomplete overlap, with important distinctions associated with each subtype. The biology of TNBC is still poorly understood; therefore, to define the relative contributions of major cellular pathways in TNBC, we have studied its molecular signature based on analysis of gene expression. Comparisons were then made with normal breast tissue. Our results suggest the existence of molecular networks in TNBC, characterized by explicit alterations in the cell cycle, DNA repair, nucleotide synthesis, metabolic pathways, NF-κB signaling, inflammatory response, and angiogenesis. Moreover, we also characterized TNBC as a cancer of mixed phenotypes, suggesting that TNBC extends beyond the basal-like molecular signature and may constitute an independent subtype of breast cancer. The data provide a new insight into the biology of TNBC.

Triple-negative breast cancer (TNBC), a subtype distinguished by negative immunohistochemical assays for expression of the estrogen and progesterone receptors (ER/PR) and human epidermal growth factor receptor-2(HER2) represents 15% of all breast cancers. Patients with TNBC generally experience a more aggressive clinical course with increased risk of disease progression and poorer overall survival. Furthermore, this subtype accounts for a disproportionate number of disease-related mortality in part due to its aggressive natural history and our lack of effective targeted agents beyond conventional cytotoxic chemotherapy. In this paper, we will review the epidemiology, risk factors, prognosis, and the molecular and clinicopathologic features that distinguish TNBC from other subtypes of breast cancer. In addition, we will examine the available data for the use of cytotoxic chemotherapy in the treatment of TNBC in both the neoadjuvant and adjuvant setting and explore the ongoing development of newer targeted agents.

Triple negative breast cancer (TNBC) is an aggressive clinical phenotype characterized by lack of expression (or minimal expression) of estrogen receptor (ER) and progesterone receptor (PR) as well as an absence of human epidermal growth factor receptor–2 (HER2) overexpression. It shows substantial overlap with basal-type and BRCA1-related breast cancers, both of which also have aggressive clinical courses. However, this overlap is not complete, and the expression of ER, PR, and HER2 has been noted in basal-like tumors. TNBC also includes the normal-like subtype, and not all patients with TNBC harbor BRCA1 mutations. Because of its expression profile, TNBC is not amenable to treatment with hormone therapy or the anti-HER2 monoclonal antibody trastuzumab, and systemic treatment options are currently limited to cytotoxic chemotherapy. Overall survival, whether in early-stage or advanced disease, is poor compared with that in patients who have other phenotypes. A number of targeted approaches to TNBC are undergoing clinical evaluation, including the use of agents with poly(ADP-ribose) polymerase inhibitory properties such as iniparib (the United States Adopted Name for the investigational agent BSI-201), olaparib (AZD2281), and veliparib (ABT-888), antiangiogenic agents such as bevacizumab and sunitinib, and epidermal growth factor receptor blockers such as cetuximab and erlotinib. Encouraging results with some of these agents have been reported, thereby offering the promise for improved outcomes in patients with TNBC. The clinical characteristics of TNBC and clinical experience to date with novel targeted agents under development for this aggressive phenotype is reviewed.

Triple-negative breast cancer (TNBC) has a poor prognosis compared to other subtypes and lacks common therapeutic targets, including HER 2 and the estrogen and progesterone receptors. The clinicopathological heterogeneity of the disease and limited treatment options make clinical management particularly challenging. Here we present the results of a survey of Canadian clinical oncologists regarding treatment of TNBC, and review recent and ongoing clinical research in this area. Our survey results show that the majority of respondents use a combination of anthracyclines-taxanes as adjuvant therapy for early TNBC. For the first-line treatment of metastatic TNBC, most clinicians recommend taxanes, while single agent capecitabine and platinum-based therapies are more common for subsequent lines of therapy. Despite the ongoing development of novel targeted therapies, chemotherapy remains the mainstay of treatment for TNBC.

Introduction

Current prognostic gene expression profiles for breast cancer mainly reflect proliferation status and are most useful in ER-positive cancers. Triple negative breast cancers (TNBC) are clinically heterogeneous and prognostic markers and biology-based therapies are needed to better treat this disease.

Methods

We assembled Affymetrix gene expression data for 579 TNBC and performed unsupervised analysis to define metagenes that distinguish molecular subsets within TNBC. We used n = 394 cases for discovery and n = 185 cases for validation. Sixteen metagenes emerged that identified basal-like, apocrine and claudin-low molecular subtypes, or reflected various non-neoplastic cell populations, including immune cells, blood, adipocytes, stroma, angiogenesis and inflammation within the cancer. The expressions of these metagenes were correlated with survival and multivariate analysis was performed, including routine clinical and pathological variables.

Results

Seventy-three percent of TNBC displayed basal-like molecular subtype that correlated with high histological grade and younger age. Survival of basal-like TNBC was not different from non basal-like TNBC. High expression of immune cell metagenes was associated with good and high expression of inflammation and angiogenesis-related metagenes were associated with poor prognosis. A ratio of high B-cell and low IL-8 metagenes identified 32% of TNBC with good prognosis (hazard ratio (HR) 0.37, 95% CI 0.22 to 0.61; P < 0.001) and was the only significant predictor in multivariate analysis including routine clinicopathological variables.

Conclusions

We describe a ratio of high B-cell presence and low IL-8 activity as a powerful new prognostic marker for TNBC. Inhibition of the IL-8 pathway also represents an attractive novel therapeutic target for this disease.

Background

Triple-negative breast cancer (TNBC) is a heterogeneous subgroup of breast cancer characterized by the lack of estrogen receptor (ER), progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2) expressions. This subgroup of refractory disease tends to have aggressive clinical behavior, high frequency of metastasis and lack of response to current hormonal or targeted therapies. Despite numerous studies reporting the clinicopathological features of TNBC and its association with the basal-like phenotype in the Western population, only limited data are available in the Asian population. Therefore, the aim of this study was to investigate the clinicopathological characteristics of TNBC and its association with epidermal growth factor receptor (EGFR), cytokeratin 5/6 (CK5/6) and mast/stem cell growth factor receptor (c-KIT or CD117) expression in Malaysian women.

Methods

A total of 340 patients diagnosed with primary breast cancer between 2002 and 2006 in Malaysia were reviewed and analyzed.

Results

The incidence of TNBC was 12.4% (42/340). Bivariate analysis revealed that TNBC was strongly associated with a younger age, higher grade tumor and p53 expression. Further immunohistochemical analysis suggested that TNBC in Malaysian women was strongly associated with EGFR, CK5/6 and c-KIT expression with high a Ki-67 proliferation index.

Conclusion

In conclusion, our study confirms the association of TNBC with basal-like marker expression (EGFR, CK5/6 and c-KIT) in Malaysian women, consistent with studies in other populations.

Motivation:

Triple-negative breast cancer (TNBC) is a heterogeneous breast cancer group, and identification of molecular subtypes is essential for understanding the biological characteristics and clinical behaviors of TNBC as well as for developing personalized treatments. Based on 3,247 gene expression profiles from 21 breast cancer data sets, we discovered six TNBC subtypes from 587 TNBC samples with unique gene expression patterns and ontologies. Cell line models representing each of the TNBC subtypes also displayed different sensitivities to targeted therapeutic agents. Classification of TNBC into subtypes will advance further genomic research and clinical applications.

Result:

We developed a web-based subtyping tool TNBCtype for candidate TNBC samples using our gene expression meta data and classification methods. Given a gene expression data matrix, this tool will display for each candidate sample the predicted subtype, the corresponding correlation coefficient, and the permutation P-value. We offer a user-friendly web interface to predict the subtypes for new TNBC samples that may facilitate diagnostics, biomarker selection, drug discovery, and the more tailored treatment of breast cancer.

Of the estimated 1 million cases of breast cancer diagnosed annually worldwide, it is estimated that over 170,000 will harbor the triple-negative (estrogen receptor/progesterone receptor/HER2–negative) phenotype. Most, though not all, triple-negative breast cancers will be basal-like on gene expression micorarrays. The basal-like molecular subtype exhibits a unique molecular profile and set of risk factors, aggressive and early pattern of metastasis, limited treatment options, and poor prognosis. Large population-based studies have identified a higher proportion of triple-negative breast tumors among premenopausal African American women, and a suggestion that increased parity, younger age at first-term pregnancy, shorter duration of breast feeding, and elevated hip-to-waist ratio might be particular risk factors. When BRCA1 mutation carriers develop breast cancer, it is usually basal-like; given the central role of BRCA1 in DNA repair, this could have profound therapeutic implications. When diagnosed, triple-negative breast cancers illustrate preferential relapse in visceral organs, including the central nervous system. Although initial response to chemotherapy might be more profound, relapse is early and common among triple-negative breast cancers compared with luminal breast cancers. The armamentarium of “targeted therapeutics” for triple-negative breast cancer is evolving and includes strategies to inhibit angiogenesis, epidermal growth factor receptor, and other kinases. Finally, the positive association between triple-negative breast cancer and BRCA mutations makes inhibition of poly(adenosine diphosphate-ribose) polymerase–1 an attractive therapeutic strategy that is in active study.

Triple negative breast cancer (TNBC) is a type of aggressive breast cancer lacking the expression of estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor receptor-2 (HER-2). TNBC patients account for approximately 15% of total breast cancer patients and are more prevalent among young African, African-American and Latino women patients. The currently available ER-targeted and Her-2-based therapies are not effective for treating TNBC. Recent studies have revealed a number of novel features of TNBC. In the present work, we comprehensively addressed these features and discussed potential therapeutic approaches based on these features for TNBC, with particular focus on: 1) the pathological features of TNBC/basal-like breast cancer; 2) E2/ERβ – mediated signaling pathways; 3) G-protein coupling receptor-30/epithelial growth factor receptor (GPCR-30/EGFR) signaling pathway; 4) interactions of ERβ with breast cancer 1/2 (BRCA1/2); 5) chemokine CXCL8 and related chemokines; 6) altered microRNA signatures and suppression of ERα expression/ERα-signaling by micro-RNAs; 7) altered expression of several pro-oncongenic and tumor suppressor proteins; and 8) genotoxic effects caused by oxidative estrogen metabolites. Gaining better insights into these molecular pathways in TNBC may lead to identification of novel biomarkers and targets for development of diagnostic and therapeutic approaches for prevention and treatment of TNBC.

Triple-negative breast cancers (TNBC) have increased rates of pathologic complete response following neoadjuvant chemotherapy, yet have poorer prognosis compared with non-TNBC. Known as the triple-negative paradox, this highlights the need to dissect the biologic and clinical heterogeneity within TNBC. In the present issue, Keam and colleagues suggest two subgroups of TNBC exist based on the proliferation-related marker Ki-67, each with differential response and prognosis following neoadjuvant chemotherapy. To place results into context, we review several definitions available under the TNBC umbrella that may stratify TNBC into clinically relevant subgroups.

Background

Triple-negative breast cancers (TNBC) neither express hormone receptors, nor overexpress HER2. They are associated with poor prognosis, as defined by low five-year survival and high recurrence rates after adjuvant therapy. Overall, TNBC share striking similarities with basal-like breast cancers (BBC), so a number of studies considered them being the same. The purpose of this review is to summarise the latest findings on TNBC concerning its relation and delineation to BBC, discuss the developmental pathways involved and address clinical implications for this complex type of breast cancer.

Methods

The recent literature from PubMed and Medline databases was reviewed.

Results

Not all TNBC are of the intrinsic BBC subtype (nonbasal (NB)-TNBC), nor are all BBC triple-negative (non-triple-negative (NTN)-BBC). There is increasing evidence that a triple-negative, basal-like breast cancer (TNBBC) subtype develops mainly through a BRCA1-related pathway. Somatic mutations that contribute to NTN-BBC and NB-TNBC development are possibly not related to this pathway, but may occur randomly due to increased genomic instability in these tumours. Several therapeutic options exist for TNBBC, which exhibited promising results in recent clinical trials. Cytotoxic therapies, e.g. combined treatment with anthracyclines or taxanes, achieved good tumour regression rates in the neo-adjuvant setting, but also showed considerable recurrence during the first 5 years after therapy. Targeted therapy options involve PARP1 and EGFR inhibition, although both approaches still need further investigation.

Conclusions

TNBC and BBC are not the same disease entity. The TNBBC subtype shows the largest homogeneity in terms of tumour development, prognosis and clinical intervention options.

Triple-negative breast cancer (TNBC) is an aggressive form of breast carcinoma with a poor prognosis. Recent evidence suggests that some patients with TNBC harbour germ-line mutations in DNA repair genes which may render their tumours susceptible to novel therapies such as treatment with PARP inhibitors. In the present study, we have investigated a hospital-based series of 40 German patients with TNBC for the presence of germ-line mutations in BRCA1, BRCA2, PALB2, and BRD7 genes. Microfluidic array PCR and next-generation sequencing was used for BRCA1 and BRCA2 analysis while conventional high-resolution melting and Sanger sequencing was applied to study the coding regions of PALB2 and BRD7, respectively. Truncating mutations in BRCA1 were found in six patients, and truncating mutations in BRCA2 and PALB2 were detected in one patient each, whereas no truncating mutation was identified in BRD7. One patient was a double heterozygote for the PALB2 mutation, c.758insT, and a BRCA1 mutation, c.927delA. Our results confirm in a hospital-based setting that a substantial proportion of German TNBC patients (17.5%) harbour germ-line mutations in genes involved in homology-directed DNA repair, with a preponderance of BRCA1 mutations. Triple-negative breast cancer should be considered as an additional criterion for future genetic counselling and diagnostic sequencing.

Triple negative breast cancer (TNBC) is a heterogeneous disease comprehending different orphan breast cancers simply defined by the absence of ER/PR/HER-2. Approximately 15%–20% of all breast cancers belong to this phenotype that has distinct risk factors, distinct molecular features, and a particular clinical presentation and outcome. All these features will be discussed in this review. The risk of developing TNBC varies with age, race, genetics, breastfeeding patterns, and parity. Some TNBC are very chemo-sensitive and the majority of patients confronted with and treated for TNBC will never relapse. Some (histological) subgroups of TNBC may have good prognosis even in the absence of chemotherapy. Distinct molecular subgroups within TNBC have been defined now as well. In case metastatic relapse occurs, this is usually within 5 years following surgery, and survival following metastatic relapse is shorter compared to other breast cancer subtypes; treatment options are few and responses lack durability. Novel drug targets and new biomarkers are needed to improve breast cancer care for patients presenting with TNBC. Further molecular/biological unraveling of TNBC is needed.

Triple-negative breast cancer (TNBC) occurs in approximately 15% of all breast cancer patients, and the incidence of TNBC is greatly increased in BRCA1 mutation carriers. This study aimed to assess the impact of BRCA1 promoter methylation with respect to breast cancer subtypes in sporadic disease. Tissue microarrays (TMAs) were constructed representing tumors from 303 patients previously screened for BRCA1 germline mutations, of which a subset of 111 sporadic tumors had previously been analyzed with respect to BRCA1 methylation. Additionally, a set of eight tumors from BRCA1 mutation carriers were included on the TMAs. Expression analysis was performed on TMAs by immunohistochemistry (IHC) for BRCA1, pRb, p16, p53, PTEN, ER, PR, HER2, CK5/6, CK8, CK18, EGFR, MUC1, and Ki-67. Data on BRCA1 aberrations and IHC expression was examined with respect to breast cancer-specific survival. The results demonstrate that CpG island hypermethylation of BRCA1 significantly associates with the basal/triple-negative subtype. Low expression of pRb, and high/intense p16, were associated with BRCA1 promoter hypermethylation, and the same effects were seen in BRCA1 mutated tumors. The expression patterns of BRCA1, pRb, p16 and PTEN were highly correlated, and define a subgroup of TNBCs characterized by BRCA1 aberrations, high Ki-67 (≥ 40%) and favorable disease outcome. In conclusion, our findings demonstrate that epigenetic inactivation of the BRCA1 gene associates with RB/p16 dysfunction in promoting TNBCs. The clinical implications relate to the potential use of targeted treatment based on PARP inhibitors in sporadic TNBCs, wherein CpG island hypermethylation of BRCA1 represents a potential marker of therapeutic response.

Background

Triple-negative breast cancer (TNBC) exhibit characteristics quite distinct from other kinds of breast cancer, presenting as an aggressive disease--recurring and metastasizing more often than other kinds of breast cancer, without tumor-specific treatment options and accounts for 15% of all types of breast cancer with higher percentages in premenopausal African-American and Hispanic women. The reason for this aggressive phenotype is currently the focus of intensive research. However, progress is hampered by the lack of suitable TNBC cell model systems.

Methods

To understand the mechanistic basis for the aggressiveness of TNBC, we produced a stable TNBC cell line by sorting for 4T1 cells that do not express the estrogen receptor (ER), progesterone receptor (PgR) or the gene for human epidermal growth factor receptor 2 (HER2). As a control, we produced a stable triple-positive breast cancer (TPBC) cell line by transfecting 4T1 cells with rat HER2, ER and PgR genes and sorted for cells with high expression of ER and PgR by flow cytometry and high expression of the HER2 gene by Western blot analysis.

Results

We isolated tumor-initiating cells (TICs) by sorting for CD24+/CD44high/ALDH1+ cells from TNBC (TNBC-TICs) and TPBC (TPBC-TICs) stable cell lines. Limiting dilution transplantation experiments revealed that CD24+/CD44high/ALDH1+ cells derived from TNBC (TNBC-TICs) and TPBC (TPBC-TICs) were significantly more effective at repopulating the mammary glands of naïve female BALB/c mice than CD24-/CD44-/ALDH1- cells. Implantation of the TNBC-TICs resulted in significantly larger tumors, which metastasized to the lungs to a significantly greater extent than TNBC, TPBC-TICs, TPBC or parental 4T1 cells. We further demonstrated that the increased aggressiveness of TNBC-TICs correlates with the presence of high levels of mouse twenty-five kDa heat shock protein (Hsp25/mouse HspB1) and seventy-two kDa heat shock protein (Hsp72/HspA1A).

Conclusions

Taken together, we have developed a TNBC-TICs model system based on the 4T1 cells which is a very useful metastasis model with the advantage of being able to be transplanted into immune competent recipients. Our data demonstrates that the TNBC-TICs model system could be a useful tool for studies on the pathogenesis and therapeutic treatment for TNBC.

Introduction

Mutations in BRCA1 and BRCA2 confer high risks of breast cancer and ovarian cancer. The risk prediction algorithm BOADICEA (Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm) may be used to compute the probabilities of carrying mutations in BRCA1 and BRCA2 and help to target mutation screening. Tumours from BRCA1 and BRCA2 mutation carriers display distinctive pathological features that could be used to better discriminate between BRCA1 mutation carriers, BRCA2 mutation carriers and noncarriers. In particular, oestrogen receptor (ER)-negative status, triple-negative (TN) status, and expression of basal markers are predictive of BRCA1 mutation carrier status.

Methods

We extended BOADICEA by treating breast cancer subtypes as distinct disease end points. Age-specific expression of phenotypic markers in a series of tumours from 182 BRCA1 mutation carriers, 62 BRCA2 mutation carriers and 109 controls from the Breast Cancer Linkage Consortium, and over 300,000 tumours from the general population obtained from the Surveillance Epidemiology, and End Results database, were used to calculate age-specific and genotype-specific incidences of each disease end point. The probability that an individual carries a BRCA1 or BRCA2 mutation given their family history and tumour marker status of family members was computed in sample pedigrees.

Results

The cumulative risk of ER-negative breast cancer by age 70 for BRCA1 mutation carriers was estimated to be 55% and the risk of ER-positive disease was 18%. The corresponding risks for BRCA2 mutation carriers were 21% and 44% for ER-negative and ER-positive disease, respectively. The predicted BRCA1 carrier probabilities among ER-positive breast cancer cases were less than 1% at all ages. For women diagnosed with breast cancer below age 50 years, these probabilities rose to more than 5% in ER-negative breast cancer, 7% in TN disease and 24% in TN breast cancer expressing both CK5/6 and CK14 cytokeratins. Large differences in mutation probabilities were observed by combining ER status and other informative markers with family history.

Conclusions

This approach combines both full pedigree and tumour subtype data to predict BRCA1/2 carrier probabilities. Prediction of BRCA1/2 carrier status, and hence selection of women for mutation screening, may be substantially improved by combining tumour pathology with family history of cancer.

Triple negative breast cancer (TNBC) constitutes 10–25% of patients with breast cancer. TNBC is an aggressive phenotype affecting younger age groups and has poor prognosis. We retrospectively analysed 50 triple negative breast cancer patients attending our outpatient department among 270 breast cancer patients. The incidence of TNBC was 18.5%, and most of them were premenopausal 56% (28/50) with mean age was 46.66 ± 13.87 (Range 28–72 years). Most of them had Invasive ductal cancer 94% (47/50) and were high grade (Grade 3−96%)(48/50). Five patients presented with metastatic disease (2 patients only Skeletal, 1 patient with Skeletal and Lung, 1 patient with Lung and 1 patient with Liver) and 7 patients developed recurrence (all 7 had chest wall recurrence, 3 had supraclavicular lymph node recurrence, 2 had skeletal metastases and 1 had developed brain metastases) during follow up. The mean disease free survival was 15 months (Range 3–58 months) and overall survival was 20.14 months (Range 5–70 months). Fifty six percent (28/50) of patients were premenopausal and mean age of presentation was 46.66 ± 13.87 years (Range 28–72 years). Ten percent (5/50) presented with metastatic disease and 15% (7/45) developed metastases during follow up. Five patients (10%) died during follow up. Hence, Triple negative breast cancer is aggressive, with rapid progression leading to mortality in younger patients.

Introduction

Women who carry a BRCA1 mutation typically develop "triple-negative" breast cancers (TNBC), defined by the absence of estrogen receptor (ER), progesterone receptor and Her2/neu. In contrast to ER-positive tumors, TNBCs frequently express high levels of epidermal growth factor receptor (EGFR). Previously, we found a disproportionate fraction of progenitor cells in BRCA1 mutation carriers with EGFR overexpression. Here we examine the role of EGFR in mammary epithelial cells (MECs) in the emergence of BRCA1-related tumors and as a potential target for the prevention of TNBC.

Methods

Cultures of MECs were used to examine EGFR protein levels and promoter activity in response to BRCA1 suppression with inhibitory RNA. EGFR was assessed by immunoblot and immunofluorescence analysis, real-time reverse transcriptase-polymerase chain reaction assay (RT-PCR) and flow cytometry. Binding of epidermal growth factor (EGF) to subpopulations of MECs was examined by Scatchard analysis. The responsiveness of MECs to the EGFR inhibitor erlotinib was assessed in vitro in three-dimensional cultures and in vivo. Mouse mammary tumor virus-Cre recombinase (MMTV-Cre) BRCA1flox/flox p53+/- mice were treated daily with erlotinib or vehicle control, and breast cancer-free survival was analyzed using the Kaplan-Meier method.

Results

Inhibition of BRCA1 in MECs led to upregulation of EGFR with an inverse correlation of BRCA1 with cellular EGFR protein levels (r2 = 0.87) and to an increase in cell surface-expressed EGFR. EGFR upregulation in response to BRCA1 suppression was mediated by transcriptional and posttranslational mechanisms. Aldehyde dehydrogenase 1 (ALDH1)-positive MECs expressed higher levels of EGFR than ALDH1-negative MECs and were expanded two- to threefold in the BRCA1-inhibited MEC population. All MECs were exquisitely sensitive to EGFR inhibition with erlotinib in vitro. EGFR inhibition in MMTV-Cre BRCA1flox/flox p53+/- female mice starting at age 3 months increased disease-free survival from 256 days in the controls to 365 days in the erlotinib-treated cohort.

Conclusions

We propose that even partial loss of BRCA1 leads to an overall increase in EGFR expression in MECs and to an expansion of the highly EGFR-expressing, ALDH1-positive fraction. Increased EGFR expression may confer a growth advantage to MECs with loss of BRCA1 at the earliest stages of transformation. Employing EGFR inhibition with erlotinib specifically at this premalignant stage was effective in decreasing the incidence of ER-negative breast tumors in this mouse model.

Introduction

Current studies indicate that triple negative breast cancer (TNBC), an aggressive breast cancer subtype, is associated with poor prognosis and an early pattern of metastasis. Emerging evidence suggests that MUC4 mucin is associated with metastasis of various cancers, including breast cancer. However, the functional role of MUC4 remains unclear in breast cancers, especially in TNBCs.

Method

In the present study, we investigated the functional and mechanistic roles of MUC4 in potentiating pathogenic signals including EGFR family proteins to promote TNBC aggressiveness using in vitro and in vivo studies. Further, we studied the expression of MUC4 in invasive TNBC tissue and normal breast tissue by immunostaining.

Results

MUC4 promotes proliferation, anchorage-dependent and-independent growth of TNBC cells, augments TNBC cell migratory and invasive potential in vitro, and enhances tumorigenicity and metastasis in vivo. In addition, our studies demonstrated that MUC4 up-regulates the EGFR family of proteins, and augments downstream Erk1/2, PKC-γ, and FAK mediated oncogenic signaling. Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition. We also demonstrated in this study, for the first time, that knockdown of MUC4 was associated with reduced expression of EGFR and ErbB3 (EGFR family proteins) in TNBC cells, suggesting that MUC4 uses an alternative to ErbB2 mechanism to promote aggressiveness. We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.

Conclusions

MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo. Overall, our findings suggest that MUC4 mucin promotes invasive activities of TNBC cells by altering the expression of EGFR, ErbB2, and ErbB3 molecules and their downstream signaling.

Introduction. Triple negative breast cancer (TNBC) is biologically aggressive and is associated with a worse prognosis. To understand the impact of race/ethnicity on outcome for patients with TNBC, confounding factors such as socioeconomic status (SES) need to be controlled. We examined the impact of race/ethnicity on a cohort of patients of low SES who have TNBC. Methods. 786 patients with Stage 0–III breast cancer were evaluated. Of these, 202 patients had TNBC (26%). Primary endpoints were cancer recurrence and death. ZIP code-based income tract and institutional financial data were used to assess SES. Data were analyzed using Kaplan-Meier survival analysis, log-rank tests, Cox Proportional hazard regression, chi square test, and t-tests. A P value ≤0.05 was considered statistically significant. Results. Of the 468 African-Americans (60%) in the database, 138 had TNBC; 64 of 318 Caucasians had TNBC. 80% of patients had an annual income of ≤$20,000. The 5-year overall survival was 77% for African-American women versus 72% for Caucasian women (P = 0.95). On multivariate analysis, race/ethnicity had an impact on disease-free survival (P = 0.027) but not on overall survival (P = 0.98). Conclusion. In a predominantly indigent population, race/ethnicity had no impact on overall survival for patients with triple negative breast cancer.

Background

Triple-negative breast cancers (TNBCs) and basal-like breast cancers (BLBCs) are known as poor outcome subtypes with a lack of targeted therapy. Previous studies have shown conflicting results regarding the difference of prognostic significance between TNBCs and BLBCs. In this study, we aimed to characterize the prognostic features of TNBCs, in view of BLBCs and quintuple-negative breast cancers (QNBC/5NPs).

Methods

Using tissue microarray-based immunohistochemical analysis, we categorized 951 primary breast cancers into four or five subtypes according to the expression of ER, PR, HER2, and basal markers (CK5/6, EGFR).

Results

The results of this study showed that both TNBCs and BLBCs were associated with high histological and/or nuclear grades. When the TNBCs are divided into two subtypes by the presence of basal markers, the clinicopathologic characteristics of TNBCs were mainly maintained in the BLBCs. The 5-subgrouping was the better prediction model for both disease free and overall survival in breast cancers than the 4-subgrouping. After multivariate analysis of TNBCs, the BLBCs did not have a worse prognosis than the QNBC/5NPs. Interestingly, the patients with BLBCs showed significant adjuvant chemotherapy benefit. In addition, QNBC/5NPs comprised about 6~8% of breast cancers in publicly available breast cancer datasets

Conclusion

The QNBC/5NP subtype is a worse prognostic subgroup of TNBCs, especially in higher stage and this result may be related to adjuvant chemotherapy benefit of BLBCs, calling for caution in the identification of subgroups of patients for therapeutic classification.

Epithelial to mesenchymal transition (EMT) plays an important role in many biological processes. The latest studies revealed that aggressive breast cancer, especially the triple-negative breast cancer (TNBC) subtype was frequently associated with apparent EMT, but the mechanisms are still unclear. NEDD9/HEF1/Cas-L is a member of the Cas protein family and was identified as a metastasis marker in multiple cancer types. In this study, we wished to discern the role of NEDD9 in breast cancer progression and to investigate the molecular mechanism by which NEDD9 regulates EMT and promotes invasion in triple-negative breast cancer. We showed that expression of NEDD9 was frequently upregulated in TNBC cell lines, and in aggressive breast tumors, especially in TNBC subtype. Knockdown of endogenous NEDD9 reduced the migration, invasion and proliferation of TNBC cells. Moreover, ectopic overexpression of NEDD9 in mammary epithelial cells led to a string of events including the trigger of EMT, activation of ERK signaling, increase of several EMT-inducing transcription factors and promotion of their interactions with the E-cadherin promoter. Data presented in this report contribute to the understanding of the mechanisms by which NEDD9 promotes EMT, and provide useful clues to the evaluation of the potential of NEDD9 as a responsive molecular target for TNBC chemotherapy.

Triple-negative breast cancer is a subtype of breast cancer that is clinically negative for expression of estrogen and progesterone receptors (ER/PR) and HER2 protein. It is characterized by its unique molecular profile, aggressive behavior, distinct patterns of metastasis, and lack of targeted therapies. Although not synonymous, the majority of triple-negative breast cancers carry the “basal-like” molecular profile on gene expression arrays. The majority of BRCA1-associated breast cancers are triple-negative and basal-like; the extent to which the BRCA1 pathway contributes to the behavior of sporadic basal-like breast cancers is an area of active research. Epidemiologic studies illustrate a high prevalence of triple-negative breast cancers among younger women and those of African descent. Increasing evidence suggests that the risk factor profile differs between this subtype and the more common luminal subtypes. Although sensitive to chemotherapy, early relapse is common and a predilection for visceral metastasis, including brain metastasis, is seen. Targeted agents, including epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and poly (ADP-ribose) polymerase (PARP) inhibitors, are currently in clinical trials and hold promise in the treatment of this aggressive disease.