Breast magnetic resonance imaging (MRI) has been shown to date to be of value in the high-risk population. Challenges in interpretation are present. Maintaining a high volume of examinations in dedicated centers definitely impacts positively on experience in interpretation. MR-guided intervention is a necessity in all diagnostic centers where breast MRI is performed. Guidelines in interpretation should be used in conjunction with optimum technique and by combining kinetic and morphologic information with clinical history and conventional imaging (mammography and ultrasound) findings, a recommendation for management can be made with more assurance.

Breast cancer is a multifactorial disease that is triggered by gene–environment interactions. Epidemiological research has identified alcohol consumption as a significant non-hormonal-related and consistent risk factor, and is thus a preventable cause of breast cancer. The reasons why alcohol drinking increase breast cancer risk are unclear, and several hypotheses exist. The perturbation of estrogen metabolism and response appears to one mechanism underlying the association. Alcohol consumption also increases breast density in postmenopausal women and affects sex steroid levels. Other plausible mechanisms include: (1) mutagenesis by acetaldehyde, which is a metabolite of ethanol; (2) by enhancing the susceptibility of the mammary gland to carcinogenesis by affecting DNA repair, stimulating cell proliferation or altering mammary gland structural development; (3) influencing the disposition and function of essential nutrients or dietary factors considered cancer protective (e.g. affecting folate and one-carbon metabolism pathways); (4) inducing genome instability and DNA damage; and (5) inducing oxidative damage via ethanol or estrogen metabolism. To better understand the etiological nature of the effect of alcohol on breast carcinogenesis, further studies at the cellular and molecular levels on the interaction between ethanol and other risk factors, estrogen, carcinogens are needed.

The role of estradiol and the estrogen receptor (ER-α) in the etiology of breast cancer have long been appreciated. This understanding has been complicated by two discoveries in the 1990s: (1) a second estrogen receptor (ER-β) whose expression pattern and activity overlap with but are distinct from those of ER-α; and (2) a pool of ERs located at the plasma membrane. This plasma membrane-localized ER constitutes a distinct pool of receptors whose protein interactions, signaling mechanisms, and cellular functions are not the same as that of the cytoplasmic- and nuclear-localized ER and are not as well understood. Here, we will consider the structure and function of the membrane-localized ER protein. We will then discuss what is known about the role of the membrane ER in the development and its implications for breast cancer treatment.

Citation of original article 1:

S. J. Isakoff, J. A. Engelman, H. Y. Irie, J. Luo, S. M. Brachmann, R. V. Pearline, L. C. Cantley, J. S. Brugge. Cancer Research 2005; 65: 10 992–11 000.

Abstract of the original article 1:

Activation of the phosphoinositide 3-kinase (PI3K) pathway has been implicated in the pathogenesis of a variety of cancers. Recently, mutations in the gene encoding the p110 catalytic subunit of PI3K (PIK3CA) have been identified in several human cancers. The mutations primarily result in single amino acid substitutions, with >85% of the mutations in either exon 9 or 20. Multiple studies have shown that these mutations are observed in 18% to 40% of breast cancers. However, the phenotypic effects of these PIK3CA mutations have not been examined in breast epithelial cells. Herein, we examine the activity of the two most common variants, E545K and H1047R, in the MCF-10A immortalized breast epithelial cell line. Both variants display higher PI3K activity than wild-type p110 yet remain sensitive to pharmacologic PI3K inhibition. In addition, expression of p110 mutants in mammary epithelial cells induces multiple phenotypic alterations characteristic of breast tumor cells, including anchorage-independent proliferation in soft agar, growth factor-independent proliferation, and protection from anoikis. Expression of these mutant p110 isoforms also confers increased resistance to paclitaxel and induces abnormal mammary acinar morphogenesis in three-dimensional basement membrane cultures. Together, these data support the notion that the cancer-associated mutations in PIK3CA may significantly contribute to breast cancer pathogenesis and represent attractive targets for therapeutic inhibition.

Citation of original article 2:

J. J. Zhao, Z. N. Liu, L. Wang, E. Shin, M. F. Loda, T. M. Roberts. Proceedings of the National Academy of Sciences of the United States of America 2005; 102: 18 443–18 448.

Abstract of the original article 2:

The PIK3CA gene encoding the p110α subunit of Class IA phosphatidylinositol 3-kinases (PI3Ks) is frequently mutated in human tumors. Mutations in the PIK3CB gene encoding p110β, the only other widely expressed Class IA PI3K, have not been reported. We compared the biochemical activity and transforming potential of mutant forms of p110α and p110β in a human mammary epithelial cell system. The two most common tumor-derived alleles of p110α, H1047R and E545K, potently activated PI3K signaling. Human mammary epithelial cells expressing these alleles grew efficiently in soft agar and as orthotopic tumors in nude mice. We also examined a third class of mutations in p110α, those in the p85-binding domain. A representative tumor-derived p85-binding-domain mutant R38H showed modestly reduced p85 binding and weakly activated PI3K/Akt signaling. In contrast, a deletion mutant lacking the entire p85-binding domain efficiently activated PI3K signaling. When we constructed in p110β a mutation homologous to the E545K allele of p110α, the resulting p110β mutant was only weakly activated and allowed minimal soft-agar growth. However, a gene fusion of p110β with the membrane anchor from c-Src was highly active and transforming in both soft-agar and orthotopic nude mouse assays. Thus, although introduction of activating mutations from p110α at the corresponding sites in p110β failed to render the enzyme oncogenic in human cells, the possibility remains that other mutations might activate the β isoform.

Citation of original article:

F. Bertucci, P. Finetti, J. Rougemont, E. Charafe-Jauffret, N. Cervera, C. Tarpin, et al. Gene expression profiling identifies molecular subtypes of inflammatory breast cancer. Cancer Research 2005; 65(6): 2170–8.

Abstract of the original article

Breast cancer is a heterogeneous disease. Comprehensive gene expression profiles obtained using DNA microarrays have revealed previously indistinguishable subtypes of non-inflammatory breast cancer (NIBC) related to different features of mammary epithelial biology and significantly associated with survival. Inflammatory breast cancer (IBC) is a rare, particular, and aggressive form of disease. Here we have investigated whether the five molecular subtypes described for NIBC (luminal A and B, basal, ERBB2 overexpressing, and normal breast-like) were also present in IBC. We monitored the RNA expression of approximately 8,000 genes in 83 breast tissue samples including 37 IBC, 44 NIBC, and 2 normal breast samples. Hierarchical clustering identified the five subtypes of breast cancer in both NIBC and IBC samples. These subtypes were highly similar to those defined in previous studies and associated with similar histoclinical features. The robustness of this classification was confirmed by the use of both alternative gene set and analysis method, and the results were corroborated at the protein level. Furthermore, we show that the differences in gene expression between NIBC and IBC and between IBC with and without pathologic complete response that we have recently reported persist in each subtype. Our results show that the expression signatures defining molecular subtypes of NIBC are also present in IBC. Obtained using different patient series and different microarray platforms, they reinforce confidence in the expression-based molecular taxonomy but also give evidence for its universality in breast cancer, independently of a specific clinical form.

Citation of original article:

A. Rody, U. Holtrich, C. Solbach, K. Kourtis, G. von Minckwitz, K. Engels, S. Kissler, R. Gätje, T. Karn, M. Kaufmann. Methylation of estrogen receptor β promoter correlates with loss of ER-β expression in mammary carcinoma and is an early indication marker in premalignant lesions. Endocrine-Related Cancer 2005; 12: 903–916.

Abstract of the original article

The function of estrogen receptor beta (ER-β) in mammary tissue is not completely understood. While early observations were often conflicting, more recent data suggest an important role as a tumor-suppressor gene. A decrease of ER-β expression has been observed in ductal carcinoma in situ and invasive carcinomas as compared with benign mammary epithelial cells. The loss of ER-β resulted in abnormal growth of mammary epithelial cells. We have previously shown that the mRNA expression of the ER-β gene is almost totally suppressed in breast carcinomas from patients with a poor prognosis. Here we analyzed whether methylation changes in the different promoters of ER-β are responsible for the loss of expression of the gene. A methylation assay with high specificity and sensitivity was developed, and a panel of breast tissue samples (n = 175) was characterized for methylation status. In contrast to benign breast, more than two-thirds of invasive breast cancers showed a high degree of methylation. Importantly, increased methylation was also detectable in numerous premalignant lesions. By analysis of breast tumors, previously characterized by gene-expression profiling, methylation was predominantly detected in a subgroup of patients with an unfavorable prognosis, suggesting a possible prognostic value of the ER-β methylation status. We also investigated the structural characteristics of the two ER-β promoters, which were both found to be closely associated with a second, downstream, localized and opposite-oriented promoter. However, we could not detect endogenous antisense RNA transcribed from these promoters, which may be involved in epigenetic gene silencing. We also failed to induce ER-β promoter methylation by expressing siRNAs in cell lines. Interestingly, by comparing the promoter sequences of ER-β with other genes known to be epigenetically inactivated in breast cancers, we identified a sequence motif possibly involved in promoter methylation.

The treatment of lymph node metastasis in human cancers has been a source of controversy for many years. Several contemporary randomized trials indicate no survival advantage to performing axillary dissection in contrast to merely observing the axilla after invasive breast cancer. This assumption is confirmed since survival advantages cannot be demonstrated when comparing greater or lesser lymph node dissections or dissection vs. observation of regional lymph nodes in melanoma and breast cancer and all other epithelial cancers.

Many recent studies indicate that axillary metastases, when they do occur in this era of mammographic screening and small invasive cancers, demonstrate metastases in the axillary sentinel nodes only in from 20% to almost 100% depending on primary cancer size. For instance, in T1a and T1b cancers, 50–100% of lymph node metastases, infrequently discovered, are contained entirely within the sentinel nodes. In T2 cancers, this proportion is roughly 25–50%, and in T3 cancers it ranges from 20% to 40%. A number of recent articles have demonstrated no difference in survival and very little nodal recurrence when patients with positive sentinel nodes are not followed by axillary dissection although the axillary disease tends to be less advanced in observed compared to treated patients with axillary dissection. Nevertheless, basic principles have been reconfirmed in these reports.

It has also been shown in animal research that clones of particular metastatic site cells demonstrate organ specificity. Transplanted human breast cancers demonstrate specific homing abilities to selective distant metastatic organ sites such as lymph nodes, bone, lung, or even adrenal gland. Genetic profiles of the different clones of cells with high metastatic specificity are each unique. Thus it is assumed that lymph node specific metastatic cells (and other organ-site-specific cells) have no ability to lodge and grow in other metastatic sites; this has been demonstrated clinically in clinical trials previously mentioned.

Therefore, there is no benefit in performing subsequent axillary dissections even when the sentinel node biopsy is positive, because of: (1) very low risk (≤2%) of recurrent clinical nodal metastases, (2) the lack of impact on disease specific or overall survival, (3) most lymph node metastases are limited to the sentinel nodes, and (4) lymph node metastases are only indicators not governors of the distant metastases. The American College of Surgeons Oncology Group (ACOSOG) Z-11 Trial was designed to specifically address this point, but unfortunately was closed early because of poor accrual; nevertheless, 900 patients were enrolled and will be analyzed over time to address this point.

Citation of original article:

K. B. Ewan, H. A. Oketch-Rabah, S. A. Ravani, G. Shyamala, H. L. Moses, M. H. Barcellos-Hoff. Proliferation of estrogen receptor-alpha-positive mammary epithelial cells is restrained by transforming growth factor-beta1 in adult mice. American Journal of Pathology 2005; 167(2): 409–17.

Abstract of the original article:

Transforming growth factor (TGF)-beta1 is a potent inhibitor of mammary epithelial proliferation. In human breast, estrogen receptor (ER)-alpha cells rarely co-localize with markers of proliferation, but their increased frequency correlates with breast cancer risk. To determine whether TGF-beta1 is necessary for the quiescence of ER-alpha-positive populations, we examined mouse mammary epithelial glands at estrus. Approximately, 35% of epithelial cells showed TGF-beta1 activation, which co-localized with nuclear receptor-phosphorylated Smad 2/3, indicating that TGF-beta signaling is autocrine. Nuclear Smad co-localized with nuclear ER-alpha. To test whether TGF-beta inhibits proliferation, we examined genetically engineered mice with different levels of TGF-beta1. ER-alpha co-localization with markers of proliferation (i.e., Ki-67 or bromodeoxyuridine) at estrus was significantly increased in the mammary glands of TGF-beta1 C57/bl/129SV heterozygote mice. This relationship was maintained after pregnancy but was absent at puberty. Conversely, mammary epithelial expression of constitutively active TGF-beta1 via the MMTV promoter suppressed proliferation of ER-alpha-positive cells. Thus, TGF-beta1 activation functionally restrains ER-alpha-positive cells from proliferating in adult mammary gland. Accordingly, we propose that TGF-beta1 dysregulation may promote proliferation of ER-alpha-positive cells associated with breast cancer risk in humans.

Citation of original article:

C. Wang et al. Cancer Research 2005; 65(15): 6557–6567.

Abstract of the original article:

The cyclin D1 gene is frequently overexpressed in human breast cancer and is capable of inducing mammary tumorigenesis when overexpressed in transgenic mice. The BRCA1 breast tumor susceptibility gene product inhibits breast cancer cellular growth and the activity of several transcription factors. Herein, cyclin D1 antagonized BRCA1-mediated repression of estrogen receptor α(ERα)-dependent gene expression. Cyclin D1 repression of BRCA1 function was mediated independently of its cyclin-dependent kinase, retinoblastoma protein, or p160 (SRC-1) functions in human breast and prostate cancer cells. In vitro, cyclin D1 competed with BRCA1 for ERα binding. Cyclin D1 and BRCA1 were both capable of binding ERα in a common region of the ERα hinge domain. A novel domain of cyclin D1, predicted to form a helix-loop-helix structure, was required for binding to ERα and for rescue of BRCA1-mediated ERα transcriptional repression. In chromatin immunoprecipitation assays, 17β-estradiol (E2) enhanced ERα and cyclin D1 recruitment to an estrogen response element (ERE). Cyclin D1 expression enhanced ERα recruitment to an ERE. E2 reduced BRCA1 recruitment and BRCA1 expression inhibited E2-induced ERα recruitment at 12 h. Cyclin D1 expression antagonized BRCA1 inhibition of ERα recruitment to an ERE, providing a mechanism by which cyclin D1 antagonizes BRCA1 function at an ERE. As cyclin D1 abundance is regulated by oncogenic and mitogenic signals, the antagonism of the BRCA1-mediated ERα repression by cyclin D1 may contribute to the selective induction of BRCA1-regulated target genes.

The use of three-dimensional conformal external beam accelerated partial breast irradiation (3D conformal APBI) to deliver hypofractionated adjuvant radiation treatment to the region of the breast at highest risk for developing a local recurrence after lumpectomy is reviewed. Potential advantages of a 3D conformal radiation therapy approach for APBI compared to brachytherapy include improved dose homogeneity within the target volume and a non-invasive method for treatment delivery. Data from several early studies using 3D conformal APBI from New York University, William Beaumont Hospital, RTOG 0319, and Massachusetts General Hospital demonstrate technical feasibility, satisfactory early cosmetic outcome, and acceptable recurrence rates. To determine whether APBI provides equivalent local tumour control in the breast compared to conventional whole breast irradiation in the local management of early stage breast cancer, the first phase III randomized study of conventional whole breast irradiation vs. partial breast irradiation was opened conjointly by the NSABP and RTOG in March 2005. The results of this study will determine future directions in the treatment of early stage breast cancer, and, will help to define the role of APBI in breast conservation therapy.

This section provides current contact details and a summary of recent or ongoing clinical trials being coordinated by Anglo-Celtic Cooperative Oncology Group (ACCOG). Clinical trials include:

1. Intensive chemotherapy for high-risk (>4 axillary lymph nodes) breast cancer. Study Anglo Celtic I

2. A randomised comparative trial of Adriamycin and Taxotere versus Adriamycin and Cyclophosphamide as primary therapy for patients with potentially operable disease >3cm diameter, locally advanced or inflammatory breast cancer. Study Anglo Celtic II

3. Prospective randomized comparison of G-CSF (filgrastim) secondary prophylaxis versus conservative management of chemotherapy-induced neutropenia to maintain dose intensity in chemotherapy for breast cancer. Study Anglo Celtic III

4. A randomized 2-arm, prospective, multi-centre, open label phase III trial comparing the activity and safety of a weekly versus a 3-weekly paclitaxel treatment schedule in patients with advanced or metastatic breast cancer. Study Anglo Celtic IV “Will Weekly Win”, www.taxol-uk.com

5. Ovarian protection trial in oestrogen non-responsive premenopausal breast cancer patients receiving adjuvant or neo-adjuvant chemotherapy. Anglo Celtic V – OPTION

Occult dissemination of tumour cells in patients with operable breast cancer is a crucial step in formation of metastasis, yet conventional tumour staging does not reveal it. To identify individual tumour cells that have successfully escaped from the primary tumour and invaded secondary organs, several research groups established sensitive immunocytochemical and molecular assays. Aside of the well documented prognostic impact of lymph node metastasis and micrometastases, respectively, bone marrow plays a prominent role as a determinant for haematogenous micrometastatic organ involvement. In the past decade, several groups have documented the independent prognostic impact of the presence of bone marrow micrometastases, which, in a recent pooled analysis of individual patient data from over 4000 breast cancer patients with Stage I–III disease, could be confirmed for the entire study population, and, in addition, provided data for challenging hypotheses to be tested in future adjuvant therapy trials of clinically relevant subgroups of breast cancer patients. Although the availability of a simple blood test would be highly desirable, no prognostically relevant data so far exists for early breast cancer patients. Options for the applicability of such approaches to detect disseminated (to bone marrow) and circulating tumour cells (in blood) are ample, both in clinical trial settings and for basic as well as translational research. In this overview we provide a brief summary of the prognostic role and the potential clinical utility of bone marrow micrometastases in breast cancer patients.