Breast Cancers With Brain Metastases are More Likely to be Estrogen Receptor Negative, Express the Basal Cytokeratin CK5/6, and Overexpress HER2 or EGFR

Disruption of the blood brain barrier by brain metastases of triple-negative and basal-type breast cancer but not HER2/neu-positive breast cancer

BACKGROUND

Generally, the blood-brain barrier (BBB) of brain metastasis was thought to be disrupted.

METHODS

We retrospectively performed immunohistochemical staining for glucose transporter 1 (GLUT1) and breast cancer resistance protein (BCRP) to evaluate the status of the BBB in resected brain metastases. Associations between expression of GLUT1 and/or BCRP and the immunohistochemical profiles of breast cancers, such as the statuses of hormone receptors, human epidermal growth factor receptor 2 (HER2/neu), and a basal-type marker (cytokeratin 5/6, HER1), were also analyzed.

RESULTS

The study included 29 breast cancer patients with brain metastasis who had undergone brain tumor resections. Among the 29 patients, there was no expression of GLUT1 and BCRP in the intratumor microvessels of 9 (32%) and 11 (38%) patients, respectively. There was no expression of both GLUT1 and BCRP in 8 patients (28%). The expression of GLUT1 was significantly associated with that of BCRP (P < .001). A positive correlation was observed between the expression of GLUT1 and/or BCRP and brain metastases of HER2/neu-positive breast cancer (P = .012), while a negative correlation was observed between the expression of GLUT1 and/or BCRP and brain metastases of triple negative or basal-type breast cancer (P = .014 and P = .003 for triple negative and basal-type, respectively).

CONCLUSIONS

Brain metastases of triple negative or basal-type breast cancers may often disrupt the BBB, whereas brain metastases of HER2/neu-positive breast cancer tend to preserve the BBB.

Lapatinib plus capecitabine resolved human epidermal growth factor receptor 2-positive brain metastases

Brain metastases affect 25%-30% of women with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer and are associated with a high burden of disease and poor prognosis. A 55-year-old woman presented with HER2-positive, hormone receptor-positive, locally advanced infiltrating ductal carcinoma. She received 4 cycles of neoadjuvant docetaxel (75 mg/m) plus trastuzumab (6 mg/kg) on a 21-day cycle, resulting in complete pathologic response at the time of surgery. Trastuzumab (6 mg/kg every 21 days) plus anastrozole (1 mg/d) was continued for 1 year. Two years later, the patient progressed with pulmonary nodules and a large pleural effusion. Computed tomography and positron emission tomography revealed multiple lesions in the liver and thoracic spine but no evidence of brain metastases. The patient received weekly trastuzumab (2 mg/kg), paclitaxel (80 mg/m), and carboplatin (area under the curve 2) for 6 months; her symptoms resolved and her disease stabilized. Seven months later, she developed diplopia and gait difficulties, and magnetic resonance imaging revealed multiple brain lesions. Whole-brain radiotherapy (30 Gy in 10 fractions) was delivered with excellent clinical results. The patient remained progression free without symptoms for approximately 3 months. When she developed central nervous system symptoms, she was treated with lapatinib (1250 mg/d continuously) plus capecitabine (2000 mg/m given on days 1-14 of a 21-day cycle). Four months later, a brain computed tomography performed shortly before her death from progressive systemic disease revealed near complete resolution of brain metastases. Lapatinib plus capecitabine seems to have clinical activity in HER2-positive brain metastases.

Clinical relevance of the triple-negative breast cancer concept: genetic basis and clinical utility of the concept

The beginning of microarray technology in the 1990s and the sequencing of the human genome in 2000 paved the way for the seminal paper of the Stanford group on the molecular portraits of human breast tumours in the same year. They described four distinct breast cancer subtypes, which they called 'luminal', 'basal', 'HER2-positive', and 'normal breast-like', based on unique gene expression patterns. This paper caused a paradigm shift. Breast cancer was no longer hormone receptor-positive or -negative, but rather luminal, basal or HER2-positive. Since then, numerous papers have appeared, trying to further characterise these subtypes on the DNA, RNA and protein level. Other groups have focussed on the epidemiology, prognosis and outcome after therapy of breast cancer patients according to these molecular subtypes. A promising prognostic marker within the subgroup of basal-like breast cancer is an up-regulated immune response, which is associated with favourable outcome. In addition, the majority of basal-like breast cancers harbour traits of a DNA damage repair defect. This feature can be exploited by the use of DNA damaging agents, and first exciting clinical results of the combination of carboplatin, gemcitabine and a poly (ADP-ribose) polymerase 1 (PARP-1) inhibitor have recently been reported. In this review, the molecular characterisation of triple-negative breast cancer, a proxy for basal-like breast cancer, is described and findings have been put into clinical context.

DEGRO Practical Guidelines for palliative radiotherapy of breast cancer patients: brain metastases and leptomeningeal carcinomatosis

PURPOSE

To provide recommendations for palliative treatment of brain metastases (BM) and leptomeningeal carcinomatosis (LC) in breast cancer patients with specific emphasis on radiooncologic aspects.

METHODS

The breast cancer expert panel of the German Society of Radiation Oncology (DEGRO) performed a comprehensive survey of the literature comprising national and international guidelines, lately published randomized trials, and relevant retrospective analyses. The search included publications between 1995-2008 (PubMed and Guidelines International Network [G-I-N]). Recommendations were devised according to the panel's interpretation of the evidence referring to the criteria of EBM.

RESULTS

Aim of any treatment of BM and LC is to alleviate symptoms and improve neurologic deficits. Close interdisciplinary cooperation facilitates rapid diagnosis and onset of therapy, tailored to the individual and clinical situation. Treatment decisions for BM should be based on the allocation to three prognostic groups defined by recursive partitioning analysis (RPA). Karnofsky Performance Score (KPS) is the strongest prognostic parameter. Together with the extent of the disease, KPS determines whether excision or radiosurgery/stereotactic radiotherapy is feasible and if exclusive or additional whole-brain radiotherapy (WBRT) is indicated. With adequate therapy, survival may be up to 3 years. For LC, treatment is mostly indicated for patients with positive cytology or in case of strongly indicative signs and symptoms. Radiotherapy (WBRT and involved-field irradiation of bulky spinal lesions) and chemotherapy (systemically or intrathecally applied methotrexate, thiotepa and cytarabine) are both effective and may prolong survival from several weeks to 4-6 months.

CONCLUSION

Radiotherapy is an effective tool for palliative treatment of BM and LC.

Triple-negative breast cancer: clinicopathological characteristics and relationship with basal-like breast cancer

Triple-negative breast cancer, defined as that with negative expression of estrogen and progesterone receptors and cerbB2, accounted for 11% of invasive breast cancers in our study, drawn from an original cohort of 7048 women diagnosed with breast cancer from the files of the Department of Pathology, Singapore General Hospital, over 14 years. Women with triple-negative breast cancer were generally postmenopausal, with adverse pathological characteristics of high histological grade and frequent nodal metastases. Using a set of 61 invasive breast cancers earlier profiled into molecular subtypes with expression arrays, we defined specificity and sensitivity values for different immunohistochemical panels of basal keratins (CK5/6, CK14, CK17, 34 beta E12), CD117, EGFR, p63 and SMA in defining basal-like breast cancer. Subsequent application of a tri-panel of CK14, EGFR and 34 beta E12 (specificity 100% and sensitivity 78%) to our group of 653 triple-negative breast cancers delineated 84% to be basal-like. Immunohistochemical expression of individual biological markers correlated with unfavorable pathological parameters. We conclude that triple-negative breast cancers in an Asian population harbor adverse pathobiological features, and an immunohistochemical surrogate panel can be reliably used to define basal-like cancers among them.

The effect of early detection of occult brain metastases in HER2-positive breast cancer patients on survival and cause of death

PURPOSE

The aim of the study is to evaluate disease-free survival, survival from the detection of brain metastases, overall survival, and cause of death in patients with occult brain metastases (Group I) vs. patients with symptomatic brain metastases (Group II).

METHODS AND MATERIALS

In 80 HER2-positive breast cancer patients, treated with trastuzumab and cytostatic agents for metastatic disease, magnetic resonance imaging screening of the brain was performed, and in 29 patients (36%) occult brain metastasis was detected (Group I). Whole-brain radiotherapy was delivered to Group I. This first group was compared with 52 patients who had symptomatic brain metastases (Group II) and was treated the same way, at the same clinic, during the same time period.

RESULTS

Median disease-free survival was 17 months in Group I and 19.9 months in Group II (p = 0.58). The median time interval between the dissemination of the disease and the detection of occult or symptomatic brain metastases was 9 and 15 months, respectively (p = 0.11). When the brain metastases were detected, the median survival was 9 and 8.78 months, respectively (p = 0.80). The median overall survival was 53 and 51 months, respectively (p = 0.94). In the group with occult brain metastases (Group I) 16% of patients died because of progression within the brain. In the group with symptomatic brain metastases (Group II) the rate of cerebral death was 48% (p = 0.009).

CONCLUSIONS

Whole-brain radiotherapy of occult brain metastases in HER2-positive breast cancer patients with visceral dissemination produces a three-fold decrease in cerebral deaths but does not prolong survival.

The role of intra-cerebrospinal fluid treatment and prophylaxis in patients with solid tumors

Metastasis to the central nervous system (CNS), including neoplastic meningitis (NM), is a devastating complication of systemic cancer. With the improved survival of cancer patients, the incidence of CNS metastasis is rising, especially among those with breast or lung carcinoma. New therapies that effectively treat these primary tumors outside of the CNS have underscored the significance of CNS metastases; they have become a significant clinical issue and a therapeutic challenge. This review discusses clinical situations in which treatment or chemoprophylaxis of CNS metastases and NM from breast or lung cancer may play an important role. Potential clinical trials to assess these assumptions also will be proposed.

Analyses of resected human brain metastases of breast cancer reveal the association between up-regulation of hexokinase 2 and poor prognosis

Brain metastases of breast cancer seem to be increasingin incidence as systemic therapy improves. Metastatic disease in the brain is associated with high morbidity and mortality. We present the first gene expression analysis of laser-captured epithelial cells from resected human brain metastases of breast cancer compared with unlinked primary breast tumors. The tumors were matched for histology, tumor-node-metastasis stage, and hormone receptor status. Most differentially expressed genes were down-regulated in the brain metastases, which included, surprisingly, many genes associated with metastasis. Quantitative real-time PCR analysis confirmed statistically significant differences or strong trends in the expression of six genes: BMP1, PEDF, LAMgamma3, SIAH, STHMN3, and TSPD2. Hexokinase 2 (HK2) was also of interest because of its increased expression in brain metastases. HK2 is important in glucose metabolism and apoptosis. In agreement with our microarray results, HK2 levels (both mRNA and protein) were elevated in a brain metastatic derivative (231-BR) of the human breast carcinoma cell line MDA-MB-231 relative to the parental cell line (231-P) in vitro. Knockdown of HK2 expression in 231-BR cells using short hairpin RNA reduced cell proliferation when cultures were maintained in glucose-limiting conditions. Finally, HK2 expression was analyzed in a cohort of 123 resected brain metastases of breast cancer. High HK2 expression was significantly associated with poor patient survival after craniotomy (P = 0.028). The data suggest that HK2 overexpression is associated with metastasis to the brain in breast cancer and it may be a therapeutic target.

Triple-negative and HER2-overexpressing breast cancers exhibit an elevated risk and an earlier occurrence of cerebral metastases

PURPOSE

Evaluation of the influence of immunohistochemically defined breast cancer (BC) subtypes and other risk factors on the development of cerebral metastases (CM).

METHODS

Exploratory analysis of a hospital-based prospective tumour registry including all patients with primary BC treated in our EUSOMA breast unit between 1998 and 2006.

RESULTS

The study cohort contained 2441 patients, including 284 patients (11.6%) with triple-negative (oestrogen receptor (ER), progesterone receptor (PR) and HER2-negative) and 245 patients (10.1%) with HER2-overexpressing BC subtypes. Overall, 80 patients (3.3%) developed CM within a median follow-up period of 47 months, 19 (23.8%) of them with triple-negative and 19 (23.8%) with HER2-positive tumours. Therefore, 6.7% of all patients with triple-negative and 7.8% of patients with HER2-positive breast cancer developed CM. Multivariate analysis indicated that the highest risk for CM was triple-negative breast cancer. Further independent risk factors were: HER2-overexpression, early onset BC (age<50 years), and large tumour size (pT3/4). Among those patients developing CM, triple-negative BC showed the shortest interval between primary diagnosis and occurrence of CM with a median of 22 months, compared to 30 and 63.5 months in HER2-positive and ER+/HER2- BC, respectively. Survival after occurrence of CM did not differ among the subtypes.

CONCLUSION

Patients with triple-negative or HER2-positive BC have a higher risk for CM compared with patients bearing the ER+/HER2- phenotype and develop CM earlier in the course of disease. A risk profile for CM might help adjust surveillance in high risk populations and identify patients with a need for new treatment strategies.

Breast cancer brain metastases express the sodium iodide symporter

Breast cancer brain metastases are on the rise and their treatment is hampered by the limited entry and efficacy of anticancer drugs in this sanctuary. The sodium iodide symporter, NIS, actively transports iodide across the plasma membrane and is exploited clinically to deliver radioactive iodide into cells. As in thyroid cancers, NIS is expressed in many breast cancers including primary and metastatic tumors. In this study NIS expression was analyzed for the first time in 28 cases of breast cancer brain metastases using a polyclonal anti-NIS antibody directed against the terminal C-peptide of human NIS gene and immunohistochemical methods. Twenty-five tumors (84%) in this retrospective series were estrogen/progesterone receptor-negative and 15 (53.6%) were HER2+. Overall 21 (75%) cases and 80% of HER2 positive metastases were NIS positive. While the predominant pattern of NIS immunoreactivity is intracellular, plasma membrane immunopositivity was detected at least focally in 23.8% of NIS-positive samples. Altogether, these findings indicate that NIS expression is prevalent in breast cancer brain metastases and could have a therapeutic role via the delivery of radioactive iodide and selective ablation of tumor cells.

Basal-like breast carcinoma: from expression profiling to routine practice

CONTEXT

Advances in the understanding of the molecular and genetic mechanisms of breast cancer have led to realization of the heterogeneity of the disease and the promise of a new era of individualized management for patients with breast cancer. The advent and use of high-throughput molecular methods for the study of breast cancer have brought to the forefront the existence of the so-called basal-like breast cancers, which have been shown to have distinct biologic and clinical characteristics.

OBJECTIVE

To critically assess the clinicopathologic features of basal-like breast cancer, discuss the morphologic and immunophenotypic features of basal-like cancer, and explore the criteria that can be used to identify these tumors in routine practice.

DATA SOURCES

A Medline/PubMed search was conducted using the terms "basal-like," "(basal OR basaloid OR basal-like) AND breast cancer." All articles in English language were retrieved and critically reviewed.

CONCLUSIONS

Basal-like breast cancers constitute a distinct, yet heterogeneous, class of neoplasms associated with specific histologic features and poor prognosis despite high response rates to neoadjuvant chemotherapy. Basal-like breast cancers have features that recapitulate those of tumors arising in BRCA1 mutation carriers, and the majority of patients with BRCA1 germline mutations develop basal-like breast cancers. At the molecular level, basal-like cancers harbor a transcriptome that is distinct from that of hormone-receptor-positive or HER2-amplified tumors, being characterized by the expression of genes usually found in basal/myoepithelial cells of the breast. However, translating the new concepts about basal-like cancer into clinical practice has proven a Herculean task, given the lack of an internationally accepted definition for these tumors and for the method of identification in routine practice.

Morphological characteristics of basal-like subtype of breast carcinoma with special reference to cytopathological features

Expression profiling of invasive breast carcinomas by DNA microarray techniques has identified five distinct subtypes of tumors (luminal A, luminal B, normal breast-like, HER2 overexpression, and basal-like) that are associated with different clinical outcomes and with different chemotherapy. Basal-like carcinoma is associated with younger patient age, high histological grade, aggressive clinical course, development of distant metastasis, poor prognosis, and relatively high mortality rate. Basal-like carcinomas do not express estrogen receptor, progesterone receptor, or HER2 (triple-negative phenotype). Therefore, patients with basal-like carcinomas are not likely to benefit from endocrine therapies or trastuzumab, but are likely to benefit from systemic chemotherapy. Although genetic, morphological, and immunohistochemical features of basal-like carcinomas have been reported, there is no universal definition for those tumors. Furthermore, there are no specific morphological and immunohistochemical features that can identify those tumors in routine diagnostic materials. In the present paper, we present data of histological and cytological features of basal-like breast carcinoma, and discuss about its morphological spectrum.

Triple-negative/basal-like breast cancer: review

Breast cancer comprises a heterogeneous group of diseases that vary in morphology, biology, behaviour and response to therapy. Triple-negative (TN) breast cancer is a subtype of tumours with aggressive clinical behaviour which currently lacks effective targeted therapies. The majority of TN breast cancers possess a basal phenotype and show varying degrees of basal marker expression (basal-like tumours). The importance of recognising these tumours came to light largely as the result of global gene expression profiling studies that categorised breast cancer into distinct molecular classes. These studies showed that basal-like tumours are molecularly different from hormone receptors and HER2 positive tumours. Although both TN and basal-like tumours share many molecular and morphological features, equating both tumour classes may be misleading. A better understanding of the molecular and histopathological features of TN and basal-like cancers is of paramount importance, in particular for unravelling the heterogeneous nature of these tumour subgroups and for the identification of prognostic biomarkers, ideal systemic therapy regimens and novel therapeutic targets for these aggressive tumours. In this review, we discuss the difference between TN and basal-like tumours, pathological and clinical features of basal-like cancer and hence explore the criteria that can be used to identify these tumours in routine practice.

Basal and triple-negative breast cancers: impact on clinical decision-making and novel therapeutic options

Since the first application of gene expression profiling to breast cancer almost a decade ago, the molecular subtyping of breast cancer has advanced rapidly from a novel concept to a clinically valuable prognostic, and possibly predictive, classification. This review summarizes the definition of the basal and related triplenegative subtypes of breast cancer, their clinical associations, and effect on outcome and treatment decision- making. Particular emphasis is placed on the clinical implications of basal breast cancer and potential therapeutic options available to oncologists.

Survival among women with triple receptor-negative breast cancer and brain metastases

BACKGROUND

The purpose of this study was to determine the incidence of and survival following brain metastases among women with triple receptor-negative breast cancer.

PATIENTS AND METHODS

In all, 679 patients with nonmetastatic triple receptor-negative breast cancer diagnosed from 1980 to 2006 were identified. Cumulative incidence of brain metastases was computed. Cox proportional hazards models were fitted to explore factors that predict for development of brain metastases. Survival was computed using the Kaplan-Meier product limit method.

RESULTS

Median follow-up was 26.9 months. In all, 42 (6.2%) patients developed brain metastases with a cumulative incidence at 2 and 5 years of 5.6% [95% confidence interval (CI) 3.8% to 7.9%] and 9.6% (95% CI 6.8% to 13%), respectively. A total of 24 (3.5%) patients developed brain metastases as the first site of recurrence with cumulative incidence at 2 and 5 years of 2.0% (95% CI 2.6% to 6.0%) and 4.9% (95% CI 3.2% to 7.0%), respectively. In the multivariable model, no specific factor was observed to be significantly associated with time to brain metastases. Median survival for all patients who developed brain metastases and those who developed brain metastases as the first site of recurrence was 2.9 months (95% CI 2.0-7.6 months) and 5.8 months (95% CI 1.7-11.0 months), respectively.

CONCLUSION

In this single-institutional study, patients with nonmetastatic triple receptor-negative breast tumors have a high early incidence of brain metastases associated with poor survival and maybe an ideal cohort to target brain metastases preventive strategies.

Immunohistochemical markers associated with brain metastases in patients with nonsmall cell lung carcinoma

BACKGROUND

To the authors' knowledge, there are no reliable markers able to identify patients with nonsmall cell lung cancer (NSCLC) that will develop metastases to the brain. The authors investigated associations between immunohistochemical markers and the development of brain metastases in patients with NSCLC.

METHODS

This was a hospital-based, case-control study of patients who were newly diagnosed with NSCLC between 1989 and 2003, developed brain metastases, and had pathology material available from both the primary NSCLC and the brain metastases. These patients were compared with a control group of patients who had NSCLC and no evidence of brain metastases. NSCLC was examined for expression levels of Ki-67, caspase-3, vascular endothelial growth factor A (VEGF-A), VEGF-C, E-cadherin, and epidermal growth factor receptor (EGFR) in 54 surgical pathology specimens using immunohistochemistry, and associations were evaluated between those markers and the development of brain metastases.

RESULTS

Brain metastases developed after a median of 12.5 months (range, 1.7-89.4 months) after the diagnosis of NSCLC. A significantly increased risk of developing brain metastases was associated with patients with NSCLC who had primary tumors with high Ki-67 levels (adjusted odds ratio [OR] of 12.2; 95% confidence interval [95% CI], 2.4-70.4 [P < .001]), low caspase-3 expression (adjusted OR of 43; 95% CI, 5.3 to >100 [P < .001]), high VEGF-C expression (adjusted OR of 14.6; 95% CI, 2.0 to >100 [P < .001]), and low E-cadherin (adjusted OR of 3.6; 95% CI, 0.9-16.4 [P = .05]). No significant risk was associated with VEGF-A or EGFR expression. High Ki-67 expression also was associated with a shorter overall survival (P = .04).

CONCLUSIONS

The results of the current study indicated that patients with NSCLC who had high Ki-67 expression, low caspase-3 expression, high VEGF-C expression, and low E-cadherin expression in their tumors may benefit from close surveillance because they may have an increased risk of developing brain metastases.

Sites of distant recurrence and clinical outcomes in patients with metastatic triple-negative breast cancer: high incidence of central nervous system metastases

BACKGROUND

The purpose of the current study was to characterize the outcomes of patients with metastatic triple-negative breast cancers, including the risk and clinical consequences of central nervous system (CNS) recurrence.

METHODS

Using pharmacy and pathology records, a study group of 116 patients who were treated for metastatic triple-negative breast cancer at Dana-Farber Cancer Institute between January 2000 and June 2006 was identified.

RESULTS

The median survival from time of metastatic diagnosis was 13.3 months. Sixteen patients (14%) were diagnosed with CNS involvement at the time of initial metastatic diagnosis; overall, 46% of patients were diagnosed with CNS metastases before death. The median survival after a diagnosis of CNS metastasis was 4.9 months. The age-adjusted and race-adjusted rate of death for patients whose first presentation included a CNS metastasis was 3.4 times (95% confidence interval, 1.9-6.1 times) that of patients without a CNS lesion at the time of first metastatic presentation. Of the 53 patients who developed brain metastases, only 3 patients were judged to have stable or responsive systemic disease in the face of progressive CNS disease at the last follow-up before death.

CONCLUSIONS

Triple-negative breast cancer is associated with poor survival after recurrence. CNS recurrence is common, but death as a direct consequence of CNS progression in the setting of controlled systemic disease is uncommon. Thus, it does not appear that the high rate of CNS involvement is because of a sanctuary effect, but rather is due to the lack of effective therapies in general for this aggressive subtype of breast cancer. New treatment strategies are needed.

Development of therapeutic approaches to 'triple negative' phenotype breast cancer

BACKGROUND

Triple negative phenotype (TNP) breast cancers are characterised by the lack of expression of oestrogen and progesterone receptors and of human EGF receptor 2 (HER2) overexpression/amplification. This subgroup of cancers has an aggressive clinical behaviour and is associated with poorer overall survival compared with other subtypes. Given the lack of targets for current tailored therapies in TNP tumours, chemotherapy is the only systemic treatment available; however, overall outcomes remain poor. Therefore, optimal treatment regimens and targeted therapies are urgently needed.

OBJECTIVE

We discuss characteristics of TNP cancers that underpin the rationale of current and novel therapeutic strategies, and an approach for finding and validating new therapeutic targets.

RESULTS/CONCLUSION

The results of large prospective randomised controlled trials are currently awaited. Efforts to unravel the heterogeneity and complexity of TNP cancers using the latest high-throughput molecular techniques and integrating these findings with biology-driven therapeutic strategies in clinical trials will be of paramount importance for the development of treatment approaches for this breast cancer subtype.

New challenges and opportunities in the management of brain metastases in patients with ErbB2-positive metastatic breast cancer

The introduction of trastuzumab for the treatment of tumors that overexpress ErbB2 (also known as HER2) has contributed significantly to recent improvements in systemic therapy for advanced breast cancer. The advances in systemic therapy have highlighted an increasing prevalence of central nervous system involvement in patients with ErbB2-positive breast cancer and a consequent need for new treatment options for brain metastases. Just as ErbB2-targeted systemic therapy has given rise to this challenge, so too could targeted therapy represent an opportunity to meet it. This Review considers the potential for targeted therapy to facilitate effective management of brain metastases in patients with ErbB2-positive breast cancer, and discusses in particular the data currently available in this setting for lapatinib, an orally available small-molecule tyrosine kinase inhibitor of ErbB1 and ErbB2.

Bone metastasis is strongly associated with estrogen receptor-positive/progesterone receptor-negative breast carcinomas

Bone is one of the most common sites of distant metastasis for breast carcinomas. In this study, our objective is to identify molecular markers and molecular subtypes that may predict patients at higher risk of developing bone metastasis. Immunohistochemical analysis with antibodies against estrogen receptor alpha, progesterone receptor, androgen receptor, Her2/neu, epidermal growth factor receptor, CK5/6, CK14, CK17, CK8, and CK18 was performed on representative sections of 21 breast carcinomas with bone metastasis and 94 cases without bone metastasis. The expression rates of receptors, subtype distributions (basal versus nonbasal) of 3 molecular classifications (cytokeratin, triple negative, and cytokeratin/triple negative), and 5 subtypes of cytokeratin/triple negative classification were compared between these 2 groups. We found that (1) the breast cancers with bone metastasis were associated with a significant percentage of estrogen receptor-positive/progesterone receptor-negative tumors compared with tumors without bone metastasis (38% versus 6%, P < .0001). (2) There was significant difference on estrogen receptor expression between high grade and non-high grade in tumors with or without bone metastasis (P = .0084 and 1.0000, respectively). (3) The breast cancers with bone metastasis were more likely to be estrogen receptor positive (85%) and androgen receptor positive (95%) compared with those without bone metastasis (59% and 74%, respectively, both P < .05). (4) There was no significant difference between tumors with or without bone metastasis in subtype distribution (basal versus nonbasal) among all 3 molecular classifications. (5) Luminal B carcinomas of cytokeratin/triple negative classification tended to be associated with bone metastasis but not to a statistically significant extent. In conclusion, bone metastasis is strongly associated with estrogen receptor-positive/progesterone receptor-negative tumors. Significant difference in estrogen receptor expression between high-grade and non-high-grade tumors with bone metastasis suggests that different panels of molecular markers should be used to predict bone metastasis in these 2 groups of tumors.

Effect of lapatinib on the outgrowth of metastatic breast cancer cells to the brain

BACKGROUND

The brain is increasingly being recognized as a sanctuary site for metastatic tumor cells in women with HER2-overexpressing breast cancer who receive trastuzumab therapy. There are no approved or widely accepted treatments for brain metastases other than steroids, cranial radiotherapy, and surgical resection. We examined the efficacy of lapatinib, an inhibitor of the epidermal growth factor receptor (EGFR) and HER2 kinases, for preventing the outgrowth of breast cancer cells in the brain in a mouse xenograft model of brain metastasis.

METHODS

EGFR-overexpressing MDA-MB-231-BR (231-BR) brain-seeking breast cancer cells were transfected with an expression vector that contained or lacked the HER2 cDNA and used to examine the effect of lapatinib on the activation (ie, phosphorylation) of cell signaling proteins by immunoblotting, on cell growth by the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and on cell migration using a Boyden chamber assay. The outgrowth of large (ie, >50 microm(2)) and micrometastases was counted in brain sections from nude mice that had been injected into the left cardiac ventricle with 231-BR cells and, beginning 5 days later, treated by oral gavage with lapatinib or vehicle (n = 22-26 mice per treatment group). All statistical tests were two-sided.

RESULTS

In vitro, lapatinib inhibited the phosphorylation of EGFR, HER2, and downstream signaling proteins; cell proliferation; and migration in 231-BR cells (both with and without HER2). Among mice injected with 231-BR-vector cells, those treated with 100 mg lapatinib/kg body weight had 54% fewer large metastases 24 days after starting treatment than those treated with vehicle (mean number of large metastases per brain section: 1.56 vs 3.36, difference = 1.80, 95% confidence interval [CI] = 0.92 to 2.68, P < .001), whereas treatment with 30 mg lapatinib/kg body weight had no effect. Among mice injected with 231-BR-HER2 cells, those treated with either dose of lapatinib had 50%-53% fewer large metastases than those treated with vehicle (mean number of large metastases per brain section, 30 mg/kg vs vehicle: 3.21 vs 6.83, difference = 3.62, 95% CI = 2.30 to 4.94, P < .001; 100 mg/kg vs vehicle: 3.44 vs 6.83, difference = 3.39, 95% CI = 2.08 to 4.70, P < .001). Immunohistochemical analysis revealed reduced phosphorylation of HER2 in 231-BR-HER2 cell-derived brain metastases from mice treated with the higher dose of lapatinib compared with 231-BR-HER2 cell-derived brain metastases from vehicle-treated mice (P < .001).

CONCLUSIONS

Lapatinib is the first HER2-directed drug to be validated in a preclinical model for activity against brain metastases of breast cancer.

Immunohistochemical profiles of brain metastases from breast cancer

The aim of present study is to explore the immunohistochemical profiles of brain metastases from breast cancer. We retrospectively performed immunohistochemical staining for estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor type 2 (HER2/neu), and cytokeratin (CK) 5/6 in 29 patients with resected tumor specimens of brain metastases. Immunohistochemical staining for ER, PgR and HER2/neu was performed in 24 patients with primary tumors. The positive frequency of immunohistochemical profiles of ER, PgR, HER2/neu, and CK5/6, in the brain metastases were 13.8%, 6.9%, 37.9%, and 24.1%, respectively. The immunohistochemical profiles including ER, PgR, and HER2/neu of the primary tumor and the brain metastasis differed in seven patients (29.2%, N = 7/24). Interestingly, the biological characteristics of brain metastasis sometimes changed which were represented by immunohistochemical staining. Therefore, the changes in the biological features of breast cancer should be taken into account when developing treatment strategies, including new molecular-targeted drugs, for brain metastases.

Characteristics of breast cancer patients with central nervous system metastases: a single-center experience

The aim of this study was to assess the characteristics of breast cancer patients with central nervous system (CNS) metastases and factors associated with survival after development of CNS metastasis. One-hundred-forty-four patients with brain metastases were retrospectively analyzed. Median age at the time of brain metastasis diagnosis was 48.9. Median time between initial diagnosis and development of brain metastasis was 36 months. Fourteen cases had leptomeningeal involvement. Twenty-two patients (15.3%) had single metastasis. Ten percent of the patients had surgery, 94% had radiotherapy and 63% had chemotherapy. Median survival after development of brain metastasis was 7.4 months. Survival of patients with single metastasis was significantly longer than those with multiple metastases (33.5 vs. 6.5 months, p = 0.0006). Survival of patients who received chemotherapy was significantly longer than those who received radiotherapy alone (9.9 vs. 2 months, p < 0.0001). In multivariate Cox regression analyses, presence of single metastasis and application of chemotherapy were the only significant factors associated with better survival (p = 0.047 and p < 0.0001, respectively). Age at initial diagnosis or at the time of brain metastasis, time from initial diagnosis to development of brain metastasis, menopausal status, tumor stage, grade, hormone receptor or HER2 status individually were not associated with survival. In this study, survival after the diagnosis of CNS metastases appeared to be affected by patient characteristics rather than biologic characteristics of the tumor. This is probably secondary to the lack of effective treatment options in these patients and overall poor prognosis.

Basal-like breast cancer: a critical review

Recent gene expression profiling of breast cancer has identified specific subtypes with clinical, biologic, and therapeutic implications. The basal-like group of tumors is characterized by an expression signature similar to that of the basal/myoepithelial cells of the breast and is reported to have transcriptomic characteristics similar to those of tumors arising in BRCA1 germline mutation carriers. They are associated with aggressive behavior and poor prognosis, and typically do not express hormone receptors or HER-2 ("triple-negative" phenotype). Therefore, patients with basal-like cancers are unlikely to benefit from currently available targeted systemic therapy. Although basal-like tumors are characterized by distinctive morphologic, genetic, immunophenotypic, and clinical features, neither an accepted consensus on routine clinical identification and definition of this aggressive subtype of breast cancer nor a way of systematically classifying this complex group of tumors has been described. Different definitions are, therefore, likely to produce variable and contradictory results that may hamper consistent identification and development of treatment strategies for these tumors. In this review, we discuss definition, heterogeneity, morphologic spectrum, relation to BRCA1, and clinical significance of this important class of breast cancer.

Pattern of metastatic spread in triple-negative breast cancer

PURPOSE

The prognosis of women with triple-negative breast cancers (defined as cancers that are estrogen receptor-negative, progesterone receptor-negative and HER2/neu negative) is poor, compared to women with other subtypes of breast cancer. It is proposed that the underlying difference in recurrence rates may be explained in part by different routes of metastatic spread.

EXPERIMENTAL DESIGN

We studied a cohort of 1608 patients diagnosed with breast cancer, diagnosed between January 1987 and December 1997 at Women's College Hospital in Toronto. Triple-negative breast cancers were defined as those that were estrogen receptor-negative, progesterone receptor-negative and HER2/neu-negative. We compared the incidence rates of metastatic spread to bone and to other (non-bone) organs in women with triple-negative and other forms of breast cancer.

RESULTS

Of the 1,608 patients, 180 (11.2%) had triple-negative breast cancer. The 1608 women were followed for a median of 9.0 years (range 0.1-19 years). Compared to other patients, those with triple-negative breast cancer had an increased likelihood of distant recurrence over the study period (adjusted hazard ratio (HR) 1.9; 95% CI: 1.5-2.5, P < 0.0001). The relatively poor prognosis was apparent in the five years after diagnosis (HR 2.9; 95% CI: 2.1-3.9; P = 0.0001) but not thereafter (HR 0.5; 95% CI: 0.2-1.1; P = 0.07). In particular, women with triple-negative breast cancer were four times more likely to experience a visceral metastasis within five years of diagnosis than those with other types of cancer (HR 4.0; 95% CI: 2.7-5.9; P < 0.0001). The rates of bone metastases were comparable for triple-negative and for other forms of cancer in this time period (HR 0.8; 95% CI: 0.4-1.6 P = 0.5).

CONCLUSIONS

The excess risk of distant recurrence in triple-negative breast cancers, versus other forms of cancer, is attributable in large part to an excess of visceral metastases in the first five years following diagnosis.

Clinical and pathologic aspects of basal-like breast cancers

Gene-expression profiling of breast cancers has shown that distinct molecular subclasses are present within tumors that are apparently morphologically similar. The molecular subclasses of cohorts classified by the 'intrinsic' gene set include the luminal A and B, erbB-2+, normal-breast-like, and basal-like tumors. Basal-like breast cancers have been reported to be associated with worse overall and disease-free survival compared with the luminal A subtype. In addition, there is an immunohistochemical surrogate for the basal-like profile, which has considerably facilitated their study in non-specialty laboratories. Basal-like breast carcinomas have markedly reduced expression of genes related to estrogen receptors and erbB-2, and express proteins that are characteristic of the normal myoepithelial cell. This Review appraises the current state of knowledge on the clinical and pathologic features of breast cancers classified as 'basal-like' by gene-expression profiling and/or immunohistochemical criteria. These tumors seem to be relatively heterogeneous according to a multitude of clinicopathologic parameters, which indicates that their most prognostically relevant subsets have yet to be defined. Similarly to tumors of luminal epithelial differentiation, carcinomas of the 'basal' type have a spectrum of morphologic and clinical characteristics.

Breast cancer surface receptors predict risk for developing brain metastasis and subsequent prognosis

Determining the status of breast cancer surface receptors (estrogen receptor, progesterone receptor, HER2/neu) has become routine in the care of patients with this disease and has proven to be helpful in guiding treatment. For this reason, breast cancer has become a model for molecularly guided therapy in solid tumors. Emerging data support that these receptors are associated with risk for developing brain metastases. Additionally, once brain metastases have occurred these receptors may also correlate with prognosis.

Breast cancer subtypes and survival in patients with brain metastases

Introduction

Brain metastases (BM) occur in up to one third of patients with metastatic breast cancer (MBC), whose incidences and prognoses by breast cancer subtypes in BM have not been well delineated.

Methods

Retrospective survival analyses were performed in 126 BM patients from 805 MBC patients treated at the National Cancer Center between August 2001 and April 2006, according to clinical characteristics, breast cancer subtypes, and receipt of trastuzumab. Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth receptor-2 (HER2) statuses were tested by immunohistochemical (IHC) staining, and HER2 FISH analysis conducted for IHC 2+.

Results

The proportion of HER2+/ER- (29% vs 16%) and triple-negative (37% vs 25%) tumors was higher in the 126 BM patients than those without BM. While median survival after recurrence was longer in patients with luminal A disease (median survival of luminal A vs luminal B vs HER2+/ER- vs triple-negative: p = 0.0246; 39.6 vs 27.4 vs 20.9 vs 15.5 months), survival was shorter from BM to death in luminal A and triple negatives (median survival: p = 0.0113; 4.0 vs 9.2 vs 5.0 vs 3.4 months). Receipt of trastuzumab after BM was a significant variable for survival in HER2+ patients. Multivariate analyses identified ER-negative, HER2-negative, or triple-negative, as well as older age, presence of leptomeningeal disease, and three or more extracranial disease sites, as poor prognostic factors for survival after BM.

Conclusion

MBC patients who developed BM had higher proportions of triple-negative and HER2+/ER- tumor status. Triple receptor status is a useful prognostic marker for predicting survival after BM in metastatic breast cancer patients.

Triple negative tumours: a critical review

Breast cancer is a heterogeneous disease that encompasses several distinct entities with remarkably different biological characteristics and clinical behaviour. Currently, breast cancer patients are managed according to algorithms based on a constellation of clinical and histopathological parameters in conjunction with assessment of hormone receptor (oestrogen and progesterone receptor) status and HER2 overexpression/gene amplification. Although effective tailored therapies have been developed for patients with hormone receptor-positive or HER2+ disease, chemotherapy is the only modality of systemic therapy for patients with breast cancers lacking the expression of these markers (triple-negative cancers). Recent microarray expression profiling analyses have demonstrated that breast cancers can be systematically characterized into biologically and clinically meaningful groups. These studies have led to the re-discovery of basal-like breast cancers, which preferentially show a triple-negative phenotype. Both triple-negative and basal-like cancers preferentially affect young and African-American women, are of high histological grade and have more aggressive clinical behaviour. Furthermore, a significant overlap between the biological and clinical characteristics of sporadic triple-negative and basal-like cancers and breast carcinomas arising in BRCA1 mutation carriers has been repeatedly demonstrated. In this review, we critically address the characteristics of basal-like and triple-negative cancers, their similarities and differences, their response to chemotherapy as well as strategies for the development of novel therapeutic targets for these aggressive types of breast cancer. In addition, the possible mechanisms are discussed leading to BRCA1 pathway dysfunction in sporadic triple-negative and basal-like cancers and animal models for these tumour types.

Breast cancer brain metastases

Breast cancer is the most common malignancy in woman in the USA. Metastasis is a major cause of morbidity and mortality in breast cancer patients. Total incidence of brain metastases of breast cancer is about 30%. Because of the improvements in control of systemic disease, for example the successful use of Trastuzumab, and the consequent prolonged life span, the incidence of brain metastases is increasing in breast cancer patients. The progressive neurological disabilities not only impair the quality of life, but also decrease the survival in patients. However, current treatments are of limited effectiveness. This is partially caused by the unique structure of the blood brain barrier. So far very little is known about the mechanisms how breast cancer metastizes to the brain. Some studies showed that ErbB2 overexpression is associated with the brain metastatic phenotype. Other molecules, like vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs) and chemokine receptor CXCR4 are also involved in the metastasis of breast cancer cell to the brain. The current review will briefly overview the clinical features of brain metastasis of breast cancer and discusses the relationship of blood brain barrier and ErbB2 signal pathway to brain metastasis in breast cancer.

Triple negative breast carcinoma and the basal phenotype: from expression profiling to clinical practice

Triple negative breast carcinomas (TNBCs) are a group of primary breast tumors with aggressive clinical behavior. Most TNBCs possess a basal phenotype (BP) and show varying degrees of basal cytokeratin and myoepithelial marker expression. The importance of recognizing these tumors came to light largely as the result of gene expression profiling studies that categorized breast cancer into 3 major groups. Two of these groups are defined by their respective expression of estrogen receptor and HER2. TNBCs represent a third group and are defined by negativity for hormone receptors and HER2. TNBCs currently lack effective targeted therapies and are frequently resistant to standard chemotherapeutic regimens. These tumors tend to occur in premenopausal women and members of specific ethnic groups and a subset are associated with heritable BRCA1 mutations. For patients with sporadic TNBCs and BP tumors, BRCA1 dysfunction seems to play a major role in the development and progression of disease. The pathologist's role in the diagnosis and characterization of TNBCs and BP tumors is currently being defined as we are acquiring knowledge of the biologic and genetic underpinnings that drive this heterogeneous group of diseases. This review will provide a historical prospective on TNBCs and tumors that express basal cytokeratins and myoepithelial makers. Additionally, we will discuss the molecular biologic, genetic and pathologic aspects of these tumors. Guidelines will be provided on how to best approach the diagnosis of these cases and on what input pathologists should provide clinicians to help develop optimal therapeutic and preventative strategies against this aggressive group of breast cancers.

Triple negative breast cancer: molecular profiling and prognostic impact in adjuvant anthracycline-treated patients

BACKGROUND

We analysed the clinical features, distribution of basal markers, prevalence of oncogene amplification, and outcome of triple negative (TN) compared to those of non-TN cancers in a series of adjuvant-anthracycline treated breast cancer patients.

METHODS

We examined the prognostic impact of the TN and BL phenotype in 245 breast cancer patients uniformly treated with adjuvant anthracycline-based chemotherapy following primary surgery, with regards to local relapse-free (LRFS), metastasis free (MFS), and breast cancer specific survival (BCSS). A comparative analysis of the clinicopathological characteristics, expression of basal markers (cytokeratins (Cks) 5/6, 14, 17, EGFR, and caveolin 1 and 2), MIB-1, p53 and topoisomerase II alpha, and prevalence of CCND1, MYC and TOP2A amplification in TN and non-TN breast tumours was performed.

RESULTS

TN cancers were significantly associated with the expression of basal markers (all P < 0.0001). However 19.4% of TN tumours were negative for basal markers, whilst 7.3% of non-TN tumours expressed basal markers. TN phenotype was significantly associated with p53, MIB-1 and topoisomerase II alpha (all, P < 0.01) expression. No TN cancer harboured amplification of CCND1 or TOP2A. In univariate analysis, TN and BL phenotype were significantly associated with shorter MFS (both, P < 0.01) and BCSS (both, P < 0.005) but not LRFS.

CONCLUSIONS

Despite treatment with standard dose anthracycline-based chemotherapy, the clinical outcome of TN and BL cancers remains poor. Alternative chemotherapeutic regimens and/or novel therapeutic approaches are warranted. Although a significant phenotypic overlap exists between TN and basal-like tumours, the TN phenotype is not an ideal surrogate marker for basal-like breast cancers.

The phenotypic spectrum of basal-like breast cancers: a critical appraisal

There are 2 well-recognized cell populations lining the mammary duct system: the epithelial cells lining the lumen and the myoepithelial cells surrounding them. The mammary stem cell, a putative third cell type, has not yet been well characterized. It is not established whether the putative stem cell expresses the full complement, a subset, or none of the markers of normal epithelial and/or myoepithelial cells. However, it is likely that they would have distinctive markers of their own; whether these are retained or lost in their neoplastic progeny is unknown. All 3 cell types may theoretically undergo malignant transformation. Until recently, however, nearly all attention has been focused on carcinomas of epithelial derivation/differentiation. The advent of oligonucleotide and cDNA microarrays has facilitated gene expression profiling of breast cancers, revealing molecular subclasses that may be prognostically relevant. One such subclass, the basal-like breast carcinomas, has been found in numerous independent datasets to be associated with a comparatively worse overall and disease-free survival. These cancers show expression of molecules characteristic of the normal myoepithelial cell, such as basal cytokeratins, and reduced expression of estrogen receptor-related and Erb-B2-related genes and proteins. The classifier genes that formed the basis for the delineation of basal-like carcinomas were derived from datasets that were composed predominantly of ductal type cancers. Therefore, the clinical significance of a basal-like gene expression or immunohistochemical profile in the other breast cancer subtypes is presently unknown. Herein, we evaluate in detail the current state of knowledge on the pathologic features of breast carcinomas classified as basal-like by immunohistochemical and/or gene expression profiling criteria, with an emphasis on their full phenotypic spectrum and also previously underemphasized areas of heterogeneity and ambiguity where present. There seems to be a phenotypic and biologic spectrum of basal-like or myoepithelial-type carcinomas, just as there is a wide range among tumors of luminal epithelial derivation/differentiation. It is critical to promote lucid morphologic definitions of the molecular subtypes, if this information is intended for use in targeted therapies and patient management.

Brain metastases: the HER2 paradigm

Between 100,000 and 170,000 patients with cancer develop central nervous system (CNS) metastases each year in the U.S., of which approximately 20% carry a primary diagnosis of breast cancer. As a consequence of improvements in systemic therapy, which have allowed patients to live longer with advanced cancer, CNS metastases are emerging as an important sanctuary site, and the incidence may be increasing in patients with particular tumor subtypes. Unless there are improvements in the treatment of CNS disease, a growing proportion of patients may be at risk of experiencing both morbidity and mortality as a result of uncontrolled CNS progression, often at a time when their extra-CNS disease is apparently under control. This article reviews changes in the epidemiology and natural history of women with brain metastases from HER2-positive breast cancer over the last decade and presents the therapeutic challenges and opportunities that have arisen in this setting. First, the apparent increase in CNS disease among women with HER2-positive breast cancer, relative to historical controls, is discussed, followed by consideration of potential causes of this observation. Next, the implications of CNS disease, in terms of prognosis and the potential development of preventive strategies are considered. Finally, new developments in systemic approaches to the treatment of CNS disease, including cytotoxic chemotherapy and targeted therapy, are explored.

Basal-like grade III invasive ductal carcinoma of the breast: patterns of metastasis and long-term survival

Introduction

Cytokeratin (CK) 14, one of several markers expressed in normal myoepithelial/basal cells, is also expressed in a proportion of breast carcinomas. Previous studies have suggested that expression of such 'basal' markers predicts different biological behaviour, with more frequent lung and brain metastases and poorer prognosis than other carcinomas.

Methods

We performed CK14 immunohistochemistry on 443 grade III invasive ductal carcinomas with extended clinical follow-up (mean 116 months), and we correlated CK14 immunopositivity (basal-like phenotype) with clinicopathological criteria.

Results

Eighty-eight of 443 (20%) tumours showed CK14 expression. CK14-positive tumours were more likely to be oestrogen receptor-negative (p < 0.0001) and axillary node-negative (p = 0.001) than were CK14-negative cases. CK14-positive cases developed less bone and liver metastases (hazard ratio [HR] 0.49, p = 0.01, and HR 0.53, p = 0.035, respectively) but more frequent brain metastases (HR 1.92, p = 0.051). In patients without metastatic disease, disease-free survival in CK14-positive cases was significantly better than in CK14-negative cases (HR 0.65, p = 0.005). In patients with metastatic disease, however, CK14 positivity was associated with a poorer prognosis (HR 1.84, p = 0.001). The overall survival in CK14-positive and -negative patients was similar at 5 years (60% and 59%, respectively), but the long-term survival was better in CK14-positive patients (HR 0.69, p = 0.02).

Conclusion

These results demonstrate that basal-like tumours differ in their biological behaviour from other tumours, with a distinct pattern of metastatic spread. Compared to other grade III tumours, basal-like tumours appear to have a relatively good long-term survival but survival after metastases is poor.

Her-2 Overexpression Increases the Metastatic Outgrowth of Breast Cancer Cells in the Brain

Retrospective studies of breast cancer patients suggest that primary tumor Her-2 overexpression or trastuzumab therapy is associated with a devastating complication: the development of central nervous system (brain) metastases. Herein, we present Her-2 expression trends from resected human brain metastases and data from an experimental brain metastasis assay, both indicative of a functional contribution of Her-2 to brain metastatic colonization. Of 124 archival resected brain metastases from breast cancer patients, 36.2% overexpressed Her-2, indicating an enrichment in the frequency of tumor Her-2 overexpression at this metastatic site. Using quantitative real-time PCR of laser capture microdissected epithelial cells, Her-2 and epidermal growth factor receptor (EGFR) mRNA levels in a cohort of 12 frozen brain metastases were increased up to 5- and 9-fold, respectively, over those of Her-2-amplified primary tumors. Co-overexpression of Her-2 and EGFR was also observed in a subset of brain metastases. We then tested the hypothesis that overexpression of Her-2 increases the colonization of breast cancer cells in the brain in vivo. A subclone of MDA-MB-231 human breast carcinoma cells that selectively metastasizes to brain (231-BR) overexpressed EGFR; 231-BR cells were transfected with low (4- to 8-fold) or high (22- to 28-fold) levels of Her-2. In vivo, in a model of brain metastasis, low or high Her-2-overexpressing 231-BR clones produced comparable numbers of micrometastases in the brain as control transfectants; however, the Her-2 transfectants yielded 3-fold greater large metastases (>50 microm(2); P < 0.001). Our data indicate that Her-2 overexpression increases the outgrowth of metastatic tumor cells in the brain in this model system.