Expression of oestrogen receptor-? in apocrine carcinomas of the breast

Carcinogenesis of Triple-Negative Breast Cancer and Sex Steroid Hormones

Simple Summary

Triple-negative breast cancer (TNBC) lacks all of three treatment targets (estrogen receptor-α, ER-α; progesterone receptor, PgR; and human epidermal growth factor receptor 2, HER2) and is usually associated with a poor clinical outcome; however, several sex steroid receptors, such as androgen receptor (AR), ER-β, and G-protein-coupled estrogen receptor, are frequently expressed and their biological and clinical importance has been suggested. Despite the structural similarity between sex steroid hormones (androgens and estrogens) or receptors (AR and ER-β), similar signaling mechanisms of these hormones, and the coexistence of these hormones and their receptors in TNBC in a clinical setting, most studies or reviews focused on only one of these receptors, and rarely reviewed them in a comprehensive way. In this review, the carcinogenic or pathobiological role of sex steroid hormones in TNBC is considered, focusing on common and differing features of hormone actions.

Abstract

Triple-negative breast cancer (TNBC) lacks an effective treatment target and is usually associated with a poor clinical outcome; however, hormone unresponsiveness, which is the most important biological characteristic of TNBC, only means the lack of nuclear estrogenic signaling through the classical estrogen receptor (ER), ER-α. Several sex steroid receptors other than ER-α: androgen receptor (AR), second ER, ER-β, and non-nuclear receptors represented by G-protein-coupled estrogen receptor (GPER), are frequently expressed in TNBC and their biological and clinical importance has been suggested by a large number of studies. Despite the structural similarity between each sex steroid hormone (androgens and estrogens) or each receptor (AR and ER-β), and similarity in the signaling mechanisms of these hormones, most studies or reviews focused on one of these receptors, and rarely reviewed them in a comprehensive way. Considering the coexistence of these hormones and their receptors in TNBC in a clinical setting, a comprehensive viewpoint would be important to correctly understand the association between the carcinogenic mechanism or pathobiology of TNBC and sex steroid hormones. In this review, the carcinogenic or pathobiological role of sex steroid hormones in TNBC is considered, focusing on the common and divergent features of the action of these hormones.

High level PHGDH expression in breast is predominantly associated with keratin 5-positive cell lineage independently of malignancy

We have previously reported the 2D PAGE-based proteomic profiling of a prospective cohort of 78 triple negative breast cancer (TNBC) patients, and the establishment of a cumulative TNBC protein database. Analysis of this database identified a number of proteins as being specifically overexpressed in TNBC samples. One such protein was D-3-phosphoglycerate dehydrogenase (Phgdh), a candidate oncogene. We analysed expression of Phgdh in normal and TNBC mammary tissue samples by 2D gel-based proteomics and immunohistochemistry (IHC), and show here that high-level expression of Phgdh in mammary epithelial cells is primarily associated with cell lineage, as we found that Phgdh expression was predominant in CK5-positive cells, normal as well as malignant, thus identifying an association of this protein with the basal phenotype. Quantitative IHC analysis of Phgdh expression in normal breast tissue showed high-level expression of Phgdh in normal CK5-positive mammary epithelial cells, indicating that expression of this protein was not associated with malignancy, but rather with cell lineage. However, proteomic profiling of Phgdh showed it to be expressed in two major protein forms, and that the ratio of expression between these variants was associated with malignancy. Overexpression of Phgdh in CK5-positive cell lineages, and differential protein isoform expression, was additionally found in other tissues and cancer types, suggesting that overexpression of Phgdh is generally associated with CK5 cells, and that oncogenic function may be determined by isoform expression.

FABP7 and HMGCS2 are novel protein markers for apocrine differentiation categorizing apocrine carcinoma of the breast

Apocrine carcinoma of the breast is a distinctive malignancy with unique morphological and molecular features, generally characterized by being negative for estrogen and progesterone receptors, and thus not electable for endocrine therapy. Despite the fact that they are morphologically distinct from other breast lesions, no standard molecular criteria are currently available for their diagnosis. Using gel-based proteomics in combination with mass spectrometry and immunohistochemistry we have identified two novel markers, HMGCS2 and FABP7 that categorize the entire breast apocrine differentiation spectrum from benign metaplasia and cysts to invasive stages. Expression of HMGCS2 and FABP7 is strongly associated with apocrine differentiation; their expression is retained by most invasive apocrine carcinomas (IAC) showing positive immunoreactivity in 100% and 78% of apocrine carcinomas, respectively, as compared to non-apocrine tumors (16.7% and 6.8%). The nuclear localization of FABP7 in tumor cells was shown to be associated with more aggressive stages of apocrine carcinomas. In addition, when added to the panel of apocrine biomarkers previously reported by our group: 15-PGDH, HMGCR and ACSM1, together they provide a signature that may represent a golden molecular standard for defining the apocrine phenotype in the breast. Moreover, we show that combining HMGCS2 to the steroidal profile (HMGCS2+/Androgen Receptor (AR)+/Estrogen Receptor(ER)-/Progesteron Receptor (PR)- identifies IACs with a greater sensitivity (79%) as compared with the steroidal profile (AR+/ER-/PR-) alone (54%). We have also presented a detailed immunohistochemical analysis of breast apocrine lesions with a panel of antibodies against proteins which correspond to 10 genes selected from published transcriptomic signatures that currently characterize molecular apocrine subtype and shown that except for melanophilin that is overexpressed in benign apocrine lesions, these proteins were not specific for morphological apocrine differentiation in breast.

Evaluation of ER-α, ER-Β1 and ER-Β2 expression and correlation with clinicopathologic factors in invasive luminal subtype breast cancers

PURPOSE

Luminal subtype breast cancer is defined as oestrogen receptor (ER)- and/or progesterone receptor (PR)- positive breast cancer. We detected the expression of ER-α, ER-Β1 and ER-Β2 in the tissue samples of invasive luminal subtype breast cancer patients, evaluated the correlations between these ER statuses and prognosis, and tried to clarify whether the status of ER-α isoforms provides clinically useful information further to what is already provided by the traditional ER-α/PR assay.

METHODS

The expression of ER-α, ER-Β1 and ER-Β2 in the paraffin-embedded sections of 162 invasive luminal subtype breast cancer patients was detected with an immunohistochemical staining method. With mid-long-term follow-up, the features of ER-α, ER-Β1 and ER-Β2 status and the correlations between clinical characteristics and the prognosis were analysed.

RESULTS

ER-Β1-positive status was correlated with PR (rs=0.217, p<0.01). The median follow-up time was 92 months (range, 4-98 months). Univariate analysis suggested that ER-Β1 status was significantly correlated to diseasefree survival (DFS) time (log rank=3.98, p=0.046), especially in patients with positive lymph nodes (log rank=6.20, p=0.013). In patients with smaller tumour size (=20 mm), negative ER-Β2 status was significantly correlated to overall survival time (log rank=3.87, p=0.049).

CONCLUSIONS

In invasive luminal subtype breast cancers, ER-Β1 is correlated with good prognosis and could be regarded as one of the factors for evaluating DFS time, especially in lymph node-positive patients. There may be some interactions between ER-Β1 and PR. In clinical practice, besides routine detection of ER-α and PR in invasive luminal subtype breast cancers, immunohistochemical staining of ER-Β1 and ER-Β2 should be considered in order to achieve more useful information. Further studies are needed to confirm our findings.

Clinical importance of androgen receptor in breast cancer patients treated with adjuvant tamoxifen monotherapy

BACKGROUND: Despite many studies, the clinicopathological importance of the androgen receptor (AR) in breast cancer is not well established, and its significance as an independent predictor of clinical outcome is controversial. A large and systematic study is needed to address these issues. The aim of the present study was to elucidate whether AR has independent clinical value, examining its importance in a large and well-predefined patient group with a long follow-up period and complete clinicopathological data. METHODS: Archival materials of 403 invasive breast cancers from women treated with adjuvant tamoxifen monotherapy (median follow-up period 11.0 years) were subjected to immunohistochemical study using anti-AR monoclonal antibody. AR expression was compared with established clinicopathological factors, estrogen receptor (ER)-β expression, and clinical outcome. RESULTS: AR positivity was correlated with ER-α positivity, progesterone receptor positivity, ER-β positivity, and a lower nuclear grade. Patients with AR-positive carcinomas exhibited a significantly better clinical outcome than those with AR-negative carcinomas (P = 0.0165 for disease-free survival, P = 0.0344 for overall survival). Multivariate analysis did not yield significant differences in clinical outcome according to the AR status, whereas the ER-β status showed significant differences in multivariate analysis. CONCLUSIONS: Although, and in agreement with previous reports, AR positivity correlated with some established favorable prognostic factors and with ER-β positivity, AR was not an independent predictor of clinical outcome. Controversy regarding the value of AR as an independent predictor of clinical outcome may at least partly reflect the relatively limited power of AR in breast cancer.

Oestrogen receptor-beta1 but not oestrogen receptor-betacx is of prognostic value in apocrine carcinoma of the breast

Apocrine carcinoma of the breast, which frequently expresses oestrogen receptor-beta (ER-beta) in the absence of ER-alpha and only infrequently is treated endocrinologically, gives an opportunity to investigate the clinicopathological role of ER-beta in breast cancer independent of ER-alpha expression or tamoxifen treatment. Several isotypes of ER-beta, ER-beta1-5 etc., have been identified thus far; however, the clinicopathological importance of each ER-beta isotype in breast cancer is still uncertain. Here we aimed to clarify the clinicopathological importance of ER-beta1 and ER-betacx (ER-beta2) in apocrine carcinomas, immunohistochemically examining expressions of ER-beta1 and ER-betacx in 47 apocrine carcinomas. Positivity for ER-beta1 and ER-betacx was observed in 41 (87%) and 18 (38%) of 47 cases, respectively. ER-beta1 positivity was related to smaller tumor size (P=0.0359), lower histological grade (P=0.0322), and higher disease-free survival (P<0.0001), whereas ER-betacx status was related to none of these parameters. ER-beta1 positivity was also associated with favorable clinical outcome in 24 so-called triple-negative (ER-alpha-negative/PR-negative/HER2-negative) apocrine carcinomas. ER-beta1 itself, independent of ER-alpha expression and tamoxifen treatment, seems to have a tumor-suppressive effect, at least in apocrine carcinomas. Further study of ER-beta1 is desired to optimize breast cancer treatment.

Molecular characterization of apocrine carcinoma of the breast: validation of an apocrine protein signature in a well-defined cohort

Invasive apocrine carcinomas (IACs), as defined by morphological features, correspond to 0.3-4% of all invasive ductal carcinomas (IDC), and despite the fact that they are histologically distinct from other breast lesions there are currently no standard molecular criteria available for their diagnosis and no unequivocal information as to their prognosis. In an effort to address these concerns we have been using protein expression profiling technologies in combination with mass spectrometry and immunohistochemistry (IHC) to discover specific biomarkers that could allow us to molecularly characterize these lesions as well as to dissect some of the steps in the processes underlying breast apocrine metaplasia and development of precancerous apocrine lesions. Establishing these apocrine-specific markers as best practice for the routine pathology evaluation of breast cancer, however, will require their validation in large cohorts of patients. Towards this goal we have composed a panel of antibodies against components of an apocrine protein signature that includes probes against the apocrine-specific markers 15-prostaglandin dehydrogenase (15-PGDH), and acyl-CoA synthetase medium-chain family member 1 (ACSM1), in addition to a set of categorizing markers that are consistently expressed (AR, CD24) or not expressed (ERα, PgR, Bcl-2, and GATA-3) by apocrine metaplasia in benign breast lesions and apocrine sweat glands. This panel was used to analyze a well-defined cohort consisting of 14 apocrine ductal carcinoma in situ (ADCIS), and 33 IACs diagnosed at the Cancer Institute Hospital, Tokyo between 1997 and 2001. Samples were originally classified on the basis of cellular morphology with all cases having more than 90% of the tumour cells exhibiting cytological features typical of apocrine cells. Using the expression of 15-PGDH and/or ACSM1 as the main criterion, but taking into account the expression of other markers, we were able to identify unambiguously 13 out of 14 ADCIS (92.9%) and 20 out of 33 (60.6%) IAC samples, respectively, as being of apocrine origin. Our results demonstrate that IACs correspond to a distinct, even if heterogeneous, molecular subgroup of breast carcinomas that can be readily identified in an unbiased way using a combination of markers that recapitulate the phenotype of apocrine sweat glands (15-PGDH(+), ACSM1(+), AR(+), CD24(+), ERα(-), PgR(-), Bcl-2(-), and GATA-3(-)). These results pave the way for addressing issues such as prognosis of IACs, patient stratification for targeted therapeutics, as well as research strategies for identifying novel therapeutic targets for developing new cancer therapies.

Clinical importance of estrogen receptor-beta evaluation in breast cancer patients treated with adjuvant tamoxifen therapy

PURPOSE

The clinicopathologic importance of a second estrogen receptor (ER), ER-beta, in breast cancers has been intensely studied; however, there is still no real consensus regarding the clinical utility of an ER-beta assay, probably because of the lack of standardized methodology, the presence of several ER-beta isotypes (ER-beta1-5, and so on), and, more importantly, the lack of convincing data on whether the ER-beta status provides clinically useful information over what is already provided by the traditional ER-alpha/progesterone receptor (PR) assay. A large and systematic study is needed to address these important issues.

PATIENTS AND METHODS

Archival materials of 442 invasive breast cancers from women treated with adjuvant tamoxifen monotherapy and with a long follow-up period (median, 11.1 years) were subjected to immunohistochemical study using three commercially available anti-ER-beta antibodies that detect ER-beta1-3 (ER-betaN), ER-beta1, and ER-betacx (ER-beta2).

RESULTS

Positive staining for ER-betaN or ER-beta1 was associated with significantly better survival. By contrast, ER-betacx status did not influence survival. In multivariate analysis, ER-beta1 status emerged as an independent predictor of recurrence and mortality. ER-beta1 status was significantly associated with survival in postmenopausal, but not premenopausal, women. Importantly, ER-beta1 positivity was associated with significantly better survival in patients with ER-alpha-negative/PR-negative or ER-alpha-negative/PR-negative/human epidermal growth factor receptor 2-negative (triple-negative) tumors, which are widely believed to be hormone unresponsive, have poor prognosis, and require chemotherapy.

CONCLUSION

Immunohistochemical examination of ER-beta1 in addition to ER-alpha and PR is clinically important in patients with breast cancer treated with tamoxifen monotherapy. Further studies are needed to confirm our findings.