An estrogen receptor-negative breast cancer subset characterized by a hormonally regulated transcriptional program and response to androgen

Molecular signatures of neoadjuvant endocrine therapy for breast cancer: characteristics of response or intrinsic resistance

Approximately 30% of patients with estrogen receptor (ER) positive breast cancers exhibit de novo or intrinsic resistance to endocrine therapies. The purpose of this study was to define genes that distinguish ER+ resistant from ER+ responsive tumors, prior to the start of hormone therapies. Previously untreated post-menopausal patients with ER+ breast cancers were treated for 4 months in a neoadjuvant setting with the aromatase inhibitor exemestane alone, or in combination with the antiestrogen tamoxifen. Matched pre- and post-treatment tumor samples from the same patient, were analyzed by gene expression profiling and were correlated with response to treatment. Genes associated with tumor shrinkage achieved by estrogen blockade therapy were identified, as were genes associated with resistance to treatment. Prediction Analysis of Microarrays (PAM) identified 50 genes that can predict response or intrinsic resistance to neoadjuvant endocrine therapy of ER+ tumors, 8 of which have been previously implicated as useful biomarkers in breast cancer. In summary, we identify genes associated with response to endocrine therapy that may distinguish ER+, hormone responsive breast cancers, from ER+ tumors that exhibit intrinsic or de novo resistance. We suggest that the estrogen signaling pathway is aberrant in ER+ tumors with intrinsic resistance. Lastly, the studies show upregulation of a "lipogenic pathway" in non-responsive ER+ tumors that may serve as a marker of intrinsic resistance. This pathway may represent an alternative target for therapeutic intervention.

Activated leukocyte cell adhesion molecule: a new paradox in cancer

The activated leukocyte cell adhesion molecule [ALCAM/CD166/melanoma metastasis clone D (MEMD)] is an immunoglobulin superfamily cell adhesion molecule. It is expressed developmentally in cells of all 3 embryonic lineages. The ALCAM expression is limited to subsets of cells in most adult tissues. ALCAM is localized at intercellular junctions in epithelium presumably as part of the adhesive complex that maintains tissue architecture. Over the past decade, alterations in expression of ALCAM have been reported in several human tumors (melanoma, prostate cancer, breast cancer, colorectal carcinoma, bladder cancer, and esophageal squamous cell carcinoma). This review summarizes the current knowledge of the role of ALCAM in malignancies.

Are trefoil factors oncogenic?

Trefoil factors (TFFs), in particular TFF1, are classical estrogen-regulated genes and have served as markers of estrogen gene regulation by various environmental estrogens. TFFs are also regulated by several other factors including growth hormone (hGH), insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF) and various oncogenic stimuli. TFFs are secreted proteins present in serum and possess the potential to act as growth factors promoting cell survival, anchorage-independent growth and motility. Recent compelling evidence has emerged from experimental and clinical studies to indicate a pivotal role of TFFs in oncogenic transformation, growth and metastatic extension of common human solid tumours. This review will summarize the current evidence for the involvement of TFFs in human cancer.

An immune response gene expression module identifies a good prognosis subtype in estrogen receptor negative breast cancer

A feature selection method was used in an analysis of three major microarray expression datasets to identify molecular subclasses and prognostic markers in estrogen receptor-negative breast cancer, showing that it is a heterogeneous disease with at least four main subtypes.

Background

Estrogen receptor (ER)-negative breast cancer specimens are predominantly of high grade, have frequent p53 mutations, and are broadly divided into HER2-positive and basal subtypes. Although ER-negative disease has overall worse prognosis than does ER-positive breast cancer, not all ER-negative breast cancer patients have poor clinical outcome. Reliable identification of ER-negative tumors that have a good prognosis is not yet possible.

Results

We apply a recently proposed feature selection method in an integrative analysis of three major microarray expression datasets to identify molecular subclasses and prognostic markers in ER-negative breast cancer. We find a subclass of basal tumors, characterized by over-expression of immune response genes, which has a better prognosis than the rest of ER-negative breast cancers. Moreover, we show that, in contrast to ER-positive tumours, the majority of prognostic markers in ER-negative breast cancer are over-expressed in the good prognosis group and are associated with activation of complement and immune response pathways. Specifically, we identify an immune response related seven-gene module and show that downregulation of this module confers greater risk for distant metastasis (hazard ratio 2.02, 95% confidence interval 1.2-3.4; P = 0.009), independent of lymph node status and lymphocytic infiltration. Furthermore, we validate the immune response module using two additional independent datasets.

Conclusion

We show that ER-negative basal breast cancer is a heterogeneous disease with at least four main subtypes. Furthermore, we show that the heterogeneity in clinical outcome of ER-negative breast cancer is related to the variability in expression levels of complement and immune response pathway genes, independent of lymphocytic infiltration.

Androgen receptor as a target for the treatment of hormone receptor-negative breast cancer: an unchartered territory

Estrogen receptor-negative (ER-) and progesterone receptor-negative (PR-) breast cancers represent approximately 30% of all breast cancers and, in general, have a more aggressive clinical course. They are unresponsive to antiestrogens, more likely to be poorly differentiated, of higher histological grade and are associated with a higher recurrence rate and decreased overall survival. Androgen receptor (AR) expression has been reported in over 70% of breast cancer and in 45–50% of patients with ER-negative breast cancer. There is emerging evidence that the androgen signaling pathway plays a critical role in breast carcinogenesis, independent of ER. Preclinical data have suggested the inhibitory role of adrenal steroids, such as dehydroepiandosterone (DHEA) and its sulfate on the growth of human ER-negative breast cancer cell lines, when these demonstrate a strong expression of AR. This potentially results in decreased AR gene expression. However, DHEA has been shown to stimulate growth in breast cancer cells when an ER is expressed in ER-positive breast cancer cells. Therefore, the effect of adrenal steroids may differ based on the tumor hormone receptor status and ER-/PR- breast tumors may not be truly hormone ‘insensitive’. Exploration of new androgen-based hormonal therapy is warranted in this patient population. This article reviews the role of the AR in breast cancer and discusses potential avenues for the treatment of ER-/PR-/AR+ tumors with ‘hormonal therapy’.

Integration of progesterone receptor action with rapid signaling events in breast cancer models

Recent discoveries suggest that several protein kinases are rapidly activated in response to ligand binding to cytoplasmic steroid hormone receptors (SRs), including progesterone receptors (PRs). Thus, PRs act as ligand-activated transcription factor "sensors" for growth factor-initiated signaling pathways in hormonally regulated tissues, such as the breast. Induction of rapid signaling upon progestin binding to PR-B provides a means to ensure that receptors and co-regulators are appropriately phosphorylated as part of optimal transcription complexes. Alternatively, PR-B activated kinase cascades provide additional avenues for progestin-regulated gene expression independent of PR nuclear action. Herein, an overview of progesterone/PR and signaling cross-talk in breast cancer models is provided. Kinases are emerging as key mediators of PR action. Cross-talk between SR and membrane-initiated signaling events suggests a mechanism for coordinate regulation of gene subsets by mitogenic stimuli in hormonally responsive normal tissues, and is suspected to contribute to cancer biology.

Defining ETS transcription regulatory networks and their contribution to breast cancer progression

ETS factors are members of one of the largest families of evolutionarily conserved transcription factors, regulating critical functions in normal cell homeostasis, that when perturbed contribute to tumor progression. The well documented alterations in ETS factor expression and function during breast cancer progression result in pleiotropic effects manifested by the downstream effect on their target genes. Multiple ETS factors bind to the same regulatory sites present on target genes, suggesting redundant or competitive functions. Furthermore, additional events contribute to, or may be necessary for, target gene regulation. In order to advance our understanding of the ETS-dependent regulation of breast cancer progression and metastasis, this prospect article puts forward a model for examining the effects of simultaneous expression of multiple transcription factors on the transcriptome of non-metastatic and metastatic breast cancer. Compared to existing RNA profiles defined following expression of individual transcription factors, the anti- and pro-metastatic signatures obtained by examining specific ETS regulatory networks will significantly improve our ability to accurately predict tumor progression and advance our understanding of gene regulation in cancer. Coordination of multiple ETS gene functions also mediates interactions between tumor and stromal cells and thus contributes to the cancer phenotype. As such, these new insights may provide a novel view of the ETS gene family as well as a focal point for studying the complex biological control involved in tumor progression.

Progesterone receptor action: translating studies in breast cancer models to clinical insights

Progesterone receptors (PR) are useful prognostic indicators of breast cancers likely to respond to anti-estrogen receptor (ER) therapies. However, the role of progesterone, therapeutic progestins, or unliganded or liganded PRin breast cancer development or progression remains controversial. PR are ligand-activated transcription factors that act in concert with intracellular signaling pathways as "sensors" of multiple growth factor inputs to hormonally regulated tissues, such as the breast. The recently defined induction of rapid signaling events upon progestin-binding to PR-B provides a means to ensure that receptors and coregulators are appropriately phosphorylated as part of optimal transcription complexes. PR-activated kinase cascades may provide additional avenues for progestin-regulated gene expression independent of PR nuclear action. Herein, we present an overview ofprogesterone/PR and signaling cross-talk in breast cancer models and discuss the potential significance ofprogestin/PR action in breast cancer biology using examples from both in vitro and in vivo models, as well as limited clinical data. Kinases are emerging as key mediators of PR action. Cross-talk between PR and membrane-initiated signaling events suggests a mechanism for coordinated regulation ofgene subsets by mitogenic stimuli in hormonally responsive normal tissues. Dysregulation of this cross-talk mechanism may contribute to breast cancer biology; further studies are needed to address the potential for targeting PR in addition to ER and selected protein kinases as part of more effective breast cancer therapies.

FoxA1 as a lineage-specific oncogene in luminal type breast cancer

The forkhead transcription factor FoxA1 is thought to be involved in mammary tumorigenesis. However, the precise role of FoxA1 in breast cancer development is controversial. We examined expression of FoxA1 in 35 human breast cancer cell lines and compared it with that of ErbB2, a marker of poor prognosis in breast cancer. We found that FoxA1 is expressed at high levels in all ErbB2-positive cell lines and a subset of ErbB2-negative cell lines. Down-regulation of FoxA1 by RNA interference significantly suppressed proliferation of ErbB2-negative and FoxA1-positive breast cancer cell lines. Down-regulation of FoxA1 also enhanced the toxic effect of Herceptin on ErbB2-positive cell lines through induction of apoptosis. Taken together with previous data that FoxA1 is a marker of luminal cells in mammary gland, our present results suggest that FoxA1 plays an important role as a lineage-specific oncogene in proliferation of cancer cells derived from mammary luminal cells.

Stat3 is tyrosine-phosphorylated through the interleukin-6/glycoprotein 130/Janus kinase pathway in breast cancer

Introduction

Signal transducer and activator of transcription 3 (Stat3) is constitutively tyrosine-phosphorylated in approximately 50% of primary breast carcinomas. A number of different mechanisms responsible for Stat3 activation, including abnormal activation of receptor tyrosine kinases, Src, and Janus kinases (Jaks), have been implicated in breast cancer.

Methods

We examined six breast cancer-derived cell lines expressing high or low levels of tyrosine-phosphorylated Stat3 (pStat3) as well as primary breast cancer specimens.

Results

Inhibition of Src or EGFR (epidermal growth factor receptor) tyrosine kinases had no effect on pStat3 levels, whereas pan-Jak inhibitor P6 resulted in complete abrogation of Stat3 phosphorylation and inhibition of growth. Jaks are required for cytokine signaling, and the glycoprotein 130 (gp130) receptor-associated Jaks are known mediators of Stat3 phosphorylation. Blockade of the gp130 receptor or sequestration of the interleukin-6 (IL-6) ligand led to a decrease of pStat3 levels. Conditioned media from those cell lines expressing high levels of pStat3 contained IL-6 and were capable of stimulating Stat3 phosphorylation. We examined IL-6 levels in primary breast tumors and found a positive correlation between pStat3 and IL-6 expression.

Conclusion

In summary, a principal mechanism of Stat3 activation in breast cancer is through the IL-6/gp130/Jak pathway.

Molecular profiling in breast cancer

Molecular profiling has provided biological evidence for the heterogeneity of breast cancer through the identification of intrinsic subtypes like Luminal A, Luminal B, HER2+/ER- and basal-like. It has also led to the development of clinically applicable gene expression-based prognostic panels like the Mammaprint and Oncotype Dx. The increasingly sophisticated understanding allowed by this and similar technology promises future individualized therapy.

FOXA1 expression in breast cancer--correlation with luminal subtype A and survival

PURPOSE

FOXA1, a forkhead family transcription factor, is essential for optimum expression of approximately 50% of estrogen receptor alpha (ERalpha):estrogen responsive genes. FOXA1 is expressed in breast cancer cells. It segregates with genes that characterize the luminal subtypes in DNA microarray analyses. The utility of FOXA1 as a possible independent prognostic factor has not been determined in breast cancers.

MATERIALS AND METHODS

A tissue microarray comprising tumors from 438 patients with 15.4 years median follow-up was analyzed for FOXA1 expression by immunohistochemistry. Interpretable FOXA1 expression obtained in 404 patients was analyzed along with other prognostic factors like tumor grade, size, nodal status, ER, progesterone receptor (PR), and HER2/neu.

RESULTS

FOXA1 expression (score >3) was seen in 300 of 404 breast cancers and it correlated with ER (P = 0.000001), PR (P = 0.00001), and luminal A subtype (P = 0.000001). Loss of expression was noted with worsening tumor grade (P = 0.001). Univariate analysis showed nodal status (P = 0.0000012), tumor size (P = 0.00001), FOXA1 (P = 0.0004), and ER (P = 0.012) to be predictors of breast cancer-specific survival. Multivariate analysis showed only nodal status (P = 0.001) and tumor size (P = 0.039) to be significant prognostic factors, whereas FOXA1 (P = 0.060) and ER (P = 0.131) were not significant. In luminal subtype A patient subgroup, FOXA1 expression was associated with better cancer-specific survival (P = 0.024) and in ER-positive subgroup, it was better predictor of cancer-specific survival (P = 0.009) than PR (P = 0.213).

CONCLUSION

FOXA1 expression correlates with luminal subtype A breast cancer and it is significant predictor of cancer-specific survival in patients with ER-positive tumors. Prognostic ability of FOXA1 in these low-risk breast cancers may prove to be useful in clinical treatment decisions.

Molecular signatures of metaplastic carcinoma of the breast by large-scale transcriptional profiling: identification of genes potentially related to epithelial-mesenchymal transition

Metaplastic carcinoma of the breast (MCB) is a poorly understood subtype of breast cancer. It is generally characterized by the coexistence of ductal carcinomatous and transdifferentiated sarcomatous components, but the underlying molecular alterations, possibly related to epithelial-mesenchymal transition (EMT), remain elusive. We performed transcriptional profiling using half-a-genome oligonucleotide microarrays to elucidate genetic profiles of MCBs and their differences to those of ductal carcinoma of breasts (DCBs) using discarded specimens of four MCBs and 34 DCBs. Unsupervised clustering disclosed distinctive expression profiles between MCBs and DCBs. Supervised analysis identified gene signatures discriminating MCBs from DCBs and between MCB subclasses. Notably, many of the discriminator genes were associated with downregulation of epithelial phenotypes and with synthesis, remodeling and adhesion of extracellular matrix, with some of them have known or inferred roles related to EMT. Importantly, several of the discriminator genes were upregulated in a mutant Snail-transfected MCF7 cell known to exhibit features of EMT, thereby indicating a crucial role for EMT in the pathogenesis of MCBs. Finally, the identification of SPARC and vimentin as poor prognostic factors reinforced the role of EMT in cancer progression. These data advance our understanding of MCB and offer clues to the molecular alterations underlying EMT.

Taking gene-expression profiling to the clinic: when will molecular signatures become relevant to patient care?

The advent of microarray technology has enabled scientists to simultaneously investigate the expression of thousands of genes. Gene-expression profiling studies have provided a molecular classification of breast cancer into clinically relevant subtypes, new tools to predict disease recurrence and response to different treatments, and new insights into various oncogenic pathways and the process of metastatic progression. Here we describe the state of the art of gene-expression studies in breast cancer, and consider both their current limitations and future promises. We also discuss the potential of molecular signatures to have an impact on individual breast cancer patient management, and ultimately to accelerate the transition between empirical and tailored medicine.

A gene transcription signature associated with hormone independence in a subset of both breast and prostate cancers

Background

The development of resistance to hormone therapy in both breast and prostate cancers is attributed to tens of thousands of patient deaths every year.

Results

From analyses of global gene expression profile data, a nonrandom amount of overlap was observed between the set of genes associated with estrogen receptor negative (ER-), hormone independent breast cancer and the set of genes associated with androgen independent (AI) prostate cancer. A set of 81 genes was identified that were differentially expressed between ER- and ER+ clinical breast tumors and breast cancer cell lines and that showed concordant expression in AI versus AS (androgen sensitive) prostate cell lines. This common gene signature of hormone independence was used to identify a subset of clinically localized primary prostate tumors that shared extensive similarities in gene transcription with both ER- breast and AI prostate cell lines and that tended to show concurrent deactivation of the androgen signaling pathway. Both ER- breast and AI prostate cell lines were significantly enriched for transcriptional targets of signaling via epidermal growth factor receptor (EGFR).

Conclusion

This study indicates that the growth- and survival-promoting functions of hormone receptors can be bypassed in a subset of both breast and prostate cancers by the same growth factor signaling pathways, which holds implications for the use of targeted therapy regimens.

FOXA1 as a therapeutic target for breast cancer

Gene expression profiling studies have classified breast cancer into five intrinsic subtypes with distinct prognostic significance: luminal type A, luminal type B, normal-like, HER-2-positive and basal type. These studies have also uncovered novel diagnostic markers and molecular targets. FOXA1, a winged-helix transcription factor belonging to the forkhead family, is one among them as it is expressed predominantly in luminal type A breast cancer, which is characterized by the presence of estrogen receptor-alpha (ERalpha) with favorable prognosis. FOXA1 is a 'pioneer' factor that binds to chromatinized DNA, opens the chromatin and enhances binding of ERalpha to its target genes. It is essential for the expression of approximately 50% of ERalpha:estrogen-regulated genes. Thus, a network comprising FOXA1, ERalpha and estrogen constitutes a major proliferation and survival signal for luminal type A breast cancer. However, by controlling differentiation and by regulating the expression of cell cycle inhibitor p27kip1 and the cell adhesion molecule E-cadherin, FOXA1 may prevent metastatic progression of luminal type A breast cancer. This article reviews possible roles of FOXA family transcription factors in breast cancer initiation, hormone dependency and speculates on the potential of FOXA1 as a therapeutic target.

TheREToncogene is a critical component of transcriptional programs associated with retinoic acid–induced differentiation in neuroblastoma

Differentiation is a key feature in pathologic classification and prognosis of neuroblastic tumors, although the underlying molecular mechanisms are not well defined. To identify key differentiation-related molecules and pathways, we evaluated gene expression during retinoic acid (RA)-induced differentiation of seven neuroblastic tumor cell lines. Transcriptional response to RA was highly variable among cell lines despite the fact that six of seven showed similar morphologic changes. RA consistently altered expression of a small set of genes, some of which are known to play a role in neurogenesis and differentiation. Expression of genes that were regulated by RA was associated with important clinical subgroups of neuroblastic tumors and were differentially expressed by stroma-rich and stroma-poor subtypes. RET, a receptor tyrosine kinase involved with differentiation, was consistently up-regulated throughout the time course of RA treatment in the majority of neuroblastic tumor cell lines. Interference with RET activation abrogated RA-induced transcriptional programs and differentiation, suggesting a key role of RET in this process. The core set of RA-regulated genes includes critical molecular components of pathways necessary for neuroblastic tumor differentiation and have potential as therapeutic targets and molecular markers of response to differentiating agents.

Integration of Rapid Signaling Events with Steroid Hormone Receptor Action in Breast and Prostate Cancer

Steroid hormone receptors (SRs) are ligand-activated transcription factors and sensors for growth factor-initiated signaling pathways in hormonally regulated tissues, such as the breast or prostate. Recent discoveries suggest that several protein kinases are rapidly activated in response to steroid hormone binding to cytoplasmic SRs. Induction of rapid signaling upon SR ligand binding ensures that receptors and coregulators are appropriately phosphorylated as part of optimal transcription complexes. Alternatively, SR-activated kinase cascades provide additional avenues for SR-regulated gene expression independent of SR nuclear action. We provide an overview of SR and signaling cross talk in breast and prostate cancers, using the human progesterone receptor (PR) and androgen receptor (AR) as models. Kinases are emerging as key mediators of SR action. Cross talk between SR and membrane-initiated signaling events suggests a mechanism for coordinate regulation of gene subsets by mitogenic stimuli in hormonally responsive normal tissues; such cross talk is suspected to contribute to cancer biology.

Prepubertal gynecomastia linked to lavender and tea tree oils

Most cases of male prepubertal gynecomastia are classified as idiopathic. We investigated possible causes of gynecomastia in three prepubertal boys who were otherwise healthy and had normal serum concentrations of endogenous steroids. In all three boys, gynecomastia coincided with the topical application of products that contained lavender and tea tree oils. Gynecomastia resolved in each patient shortly after the use of products containing these oils was discontinued. Furthermore, studies in human cell lines indicated that the two oils had estrogenic and antiandrogenic activities. We conclude that repeated topical exposure to lavender and tea tree oils probably caused prepubertal gynecomastia in these boys.

FOXA1: Growth inhibitor and a favorable prognostic factor in human breast cancer

The transcription factor Forkhead-box A1 (Foxa1), a member of the FOX class of transcription factors, has been implicated in the pathogenesis of lung, esophageal and prostate cancers. We have recently identified transcriptional activation of p27 by FOXA1. In this study, we analyzed the activities and expression pattern of FOXA1 in breast cancer. Forced expression of FOXA1 inhibited clonal growth of breast cancer cell lines, and FOXA1 levels inversely correlated with growth stimuli. In the estrogen receptor (ER)-positive MCF-7 cells, FOXA1 increased p27 promoter activity and inhibited the ER pathway activity. Analysis of FOXA1 expression in breast tissue arrays revealed significantly higher expression in pure ductal carcinomas in situ compared to invasive ductal carcinomas (IDC); and in IDC, high expression of FOXA1 was associated with favorable prognostic factors. Yet, FOXA1 expression was noted in a subset of the ER-negative tumors. Taken together, our findings suggest a growth inhibitory role for FOXA1, and identify it as a novel, potential prognostic factor in breast cancer.