Oestrogen and Progesterone Receptors as Prognostic Variables in Hormonally Treated Breast Cancer

Role of Coactivators and Corepressors in Steroid and Nuclear Receptor Signaling: Potential Markers of Tumor Growth and Drug Sensitivity

Nuclear receptors regulate target gene expression in response to steroid and thyroid hormones, retinoids, vitamin D and other ligands. These ligand-dependent transcription factors function by contacting various nuclear cooperating proteins, called coactivators and corepressors, which mediate local chromatin remodeling as well as communication with the basal transcriptional apparatus. Nuclear receptors and their coregulatory proteins play a role in cancer and other diseases, one leading example being the estrogen receptor pathway in breast cancer. Coregulators are often present in limiting amounts in cell nuclei and modifications of their level of expression and/or structure lead to alterations in nuclear receptor functioning, which may be as pronounced as a complete inversion of signaling, i.e. from stimulating to repressing certain genes in response to an identical stimulus. In addition, hemizygous knock-out of certain coactivator genes has been demonstrated to produce cancer-prone phenotypes in mice. Thus, assessment of coactivator and corepressor expression and structure in tumors may turn out to be essential to determine the role of nuclear receptors in cancer and to predict prognosis and response to therapy.

Prognostic Significance of Single Progesterone Receptor Positivity: A Comparison Study of Estrogen Receptor Negative/Progesterone Receptor Positive/Her2 Negative Primary Breast Cancer With Triple Negative Breast Cancer

Single progesterone receptor positive (PgR+), especially in form of ER-/PgR+/HER2-, is a nonnegligible phenomenon. Little is known about the characteristics and the role of single PgR positive in this phenotype. Therefore, we explore the significance of single PgR positivity by comparing ER-/PgR+/HER2- breast cancers with triple negative breast cancers (TNBCs).Three thousand nine hundred sixty-six cases of primary invasive breast carcinoma operated consecutively from January 2005 to May 2008 in Cancer Hospital, Chinese Academy of Medical Sciences were examined. Two hundred forty (6%) cases were identified as ER-/PgR+/HER2- breast cancers and 348 (8.8%) cases as TNBCs. Clinicopathological characteristics and survivals were analyzed respectively and then compared between 2 subtypes.Compared with patients with TNBCs, ER-/PgR+/HER2- tumor tended to have lower tumor grade (Grade 3: 45.7% vs. 37.5%, P = 0.051) and smaller tumor size (P = 0.036). However, no differences were found between ER-/PgR+/HER2- and TNBC patients in relapse-free survival (RFS) and OS. The 5-year RFS rates were 80.7% and 77.4%, respectively (P = 0.330) and the 5-year OS rates were 88.0% and 85.2%, respectively (P = 0.290). ER-/PgR+/HER2- patients receiving adjuvant endocrine treatment had better RFS (P = 0.016) and overall survival (OS) (P < 0.0001) than patients receiving no endocrine therapy.This exclusive analysis of patients with ER-/PgR+/HER2- breast cancers showed that this subtype exhibited an aggressive behavior as TNBC, suggesting that it should also be regarded as biologically distinctive group and single PgR positive itself is not a good prognostic factor. However, adjuvant endocrine therapy could still benefit this group of patients. Further investigations should be done to elucidate the underlying mechanism.

Outcomes of adjuvant endocrine therapy and hormone receptor status change following neoadjuvant chemotherapy in breast cancer patients

BACKGROUND

This retrospective study investigated the therapeutic benefit of adjuvant endocrine therapy (ET) in breast cancer patients with hormone receptor (HR) status change from positive to negative after neoadjuvant chemotherapy (NAC).

METHODS

From December 2000 to November 2010, 97 eligible patients with a positive-to-negative switch of HR status after NAC were identified. All patients were categorized into 2 groups on the basis of the administration of ET: 57 ET-administered patients and 40 ET-naïve patients. Survival analyses were performed to examine the prognostic value of ET administration as well as other clinical and pathologic variables.

RESULTS

The administration of ET was significantly associated with improved disease-free survival (p=0.018) in patients with a positive-to-negative switch of HR status. The 5-year disease-free survival rates were 77.0% and 55.5%, respectively, in ET-administered patients and ET-naïve patients. The 5-year overall survival rate for ET-administered patients was also higher than that of ET-naïve patients (81.3% vs. 72.7%, p=0.053), albeit this was statistically insignificant.

CONCLUSIONS

This study revealed that patients with HR altered from positive to negative after NAC still benefit from ET. The HR status should be evaluated not only in specimens obtained during post-NAC surgery but also in specimens biopsied before NAC.

AGR2 predicts tamoxifen resistance in postmenopausal breast cancer patients

Endocrine resistance is a significant problem in breast cancer treatment. Thus identification and validation of novel resistance determinants is important to improve treatment efficacy and patient outcome. In our work, AGR2 expression was determined by qRT-PCR in Tru-Cut needle biopsies from tamoxifen-treated postmenopausal breast cancer patients. Our results showed inversed association of AGR2 mRNA levels with primary treatment response (P = 0.0011) and progression-free survival (P = 0.0366) in 61 ER-positive breast carcinomas. As shown by our experimental and clinical evaluations, elevated AGR2 expression predicts decreased efficacy of tamoxifen treatment. From this perspective, AGR2 is a potential predictive biomarker enabling selection of an optimal algorithm for adjuvant hormonal therapy in postmenopausal ER-positive breast cancer patients.

The pro-metastatic protein anterior gradient-2 predicts poor prognosis in tamoxifen-treated breast cancers

Transcriptomic screens in breast cancer cell lines have identified a protein named anterior gradient-2 (AGR2) as a potentially novel oncogene overexpressed in estrogen receptor (ER) positive tumours. As targeting the ER is responsible for major improvements in cure rates and prevention of breast cancers, we have evaluated the pro-oncogenic function of AGR2 in anti-hormone therapeutic responses. We show that AGR2 expression promotes cancer cell survival in clonogenic assays and increases cell proliferation and viability in a range of cancer cell lines. Chromatin immunoprecipitation and reporter assays indicate that AGR2 is transcriptionally activated by estrogen through ERalpha. However, we also found that AGR2 expression is elevated rather than inhibited in response to tamoxifen, thus identifying a novel mechanism to account for an agonistic effect of the drug on a specific pro-oncogenic pathway. Consistent with these data, clinical analysis indicates that AGR2 expression is related to treatment failure in ERalpha-positive breast cancers treated with tamoxifen. In contrast, AGR2 is one of the most highly suppressed genes in cancers of responding patients treated with the anti-hormonal drug letrozole. These data indicate that the AGR2 pathway represents a novel pro-oncogenic pathway for evaluation as anti-cancer drug developments, especially therapies that by-pass the agonist effects of tamoxifen.

The effects of gefitinib in tamoxifen-resistant and hormone-insensitive breast cancer: a phase II study

Estrogen receptor (ER)-positive acquired tamoxifen-resistant (TAM-R) MCF-7 breast cancer cell lines exhibit epidermal growth factor receptor (EGFR) expression/signaling and are growth-inhibited by gefitinib (IRESSA). We examined the effect of gefitinib on ER-positive TAM-R and ER-negative hormone-insensitive breast cancer in a Phase II study. Fifty-four patients with breast cancer [ER-positive/acquired TAM-R (n = 28); ER-negative (n = 26)] received oral gefitinib 500 mg/day. Tumor biopsies were taken pre- (n = 28) and 8 weeks post-treatment (n = 14 matched samples). Gefitinib was well tolerated and the clinical benefit rate (objective response or stable disease >24 weeks) was 33.3% overall (n = 18/54), and 53.6 and 11.5% in ER-positive/TAM-R and ER-negative patients, respectively. Pretreatment ER and progesterone receptor-positivity were associated with response (p < 0.001 and 0.016, respectively) and longer progression-free survival (PFS; p= 0.001 and 0.013, respectively). All patients expressed EGFR, but high pretreatment levels predicted poorer outcome (p = 0.005) and shorter PFS (p = 0.012) with gefitinib. In patients with clinical benefit, reduced Ki67 staining during treatment (p = 0.024) was commonly observed, and those with >10% decline in EGFR phosphorylation demonstrated parallel decreases in ERK1/2 MAPK phosphorylation. Acquired tamoxifen resistance appears in part mediated through EGFR signaling and can be blocked with gefitinib.

Proproliferative functions of Drosophila small mitochondrial heat shock protein 22 in human cells

Aging is a complex process accompanied by a decreased capacity of cells to cope with random damages induced by reactive oxygen species, the natural by-products of energy metabolism, leading to protein aggregation in various components of the cell. Chaperones are important players in the aging process as they prevent protein misfolding and aggregation. Small chaperones, such as small heat shock proteins, are involved in the refolding and/or disposal of protein aggregates, a feature of many age-associated diseases. In Drosophila melanogaster, mitochondrial Hsp22 (DmHsp22), is localized in the mitochondrial matrix and is preferentially up-regulated during aging. Its overexpression results in an extension of life span (>30%) (Morrow, G., Samson, M., Michaud, S., and Tanguay, R. M. (2004) FASEB J. 18, 598-599 and Morrow, G., Battistini, S., Zhang, P., and Tanguay, R. M. (2004) J. Biol. Chem. 279, 43382-43385). Long lived flies expressing Hsp22 also have an increased resistance to oxidative stress and maintain locomotor activity longer. In the present study, the cross-species effects of Hsp22 expression were tested. DmHsp22 was found to be functionally active in human cells. It extended the life span of normal fibroblasts, slowing the aging process as evidenced by a lower level of the senescence associated beta-galactosidase. DmHsp22 expression in human cancer cells increased their malignant properties including anchorage-independent growth, tumor formation in nude mice, and resistance to a variety of anticancer drugs. We report that the DmHsp22 interacts and inactivates wild type tumor suppressor protein p53, which may be one possible way of its functioning in human cells.

Estrogen Receptor β2 Negatively Regulates the Transactivation of Estrogen Receptor α in Human Breast Cancer Cells

Estrogens, by binding to and activating two estrogen receptors (ERalpha and ERbeta), are critically involved in the development of the mammary gland and breast cancer. An isoform of ERbeta, ERbeta2 (also called ERbetacx), with an altered COOH-terminal region, is coexpressed with ERalpha in many human breast cancers. In this study, we generated a stable cell line from MCF7 breast cancer cells expressing an inducible version of ERbeta2, along with endogenous ERalpha, and examined the effects of ERbeta2 on the ERalpha protein levels and function. We showed that ERbeta2 inhibited ERalpha-mediated transactivation via estrogen response element and activator protein-1 sites of reporter constructs as well as the endogenous genes pS2 and MMP-1. Chromatin immunoprecipitation assays revealed that ERbeta2 expression caused a significant reduction in the recruitment of ERalpha to both the pS2 and MMP-1 promoters. Furthermore, ERbeta2 expression induced proteasome-dependent degradation of ERalpha. The inhibitory effects of ERbeta2 on ERalpha activity were further confirmed in HEK293 cells that lack functional endogenous ERs. We also showed that ERbeta2 can interact with ERalpha both in vitro and in mammalian cells, which is compatible with a model where ERbeta2/ERalpha heterodimers are targeted to the proteasome. Finally, in human breast cancer samples, we observed that expression of ERbeta2 significantly correlated with ERalpha-negative phenotype. Our data suggest that ERbeta2 could influence ERalpha-mediated effects relevant for breast cancer development, including hormone responsiveness.

Biologic basis of sequential and combination therapies for hormone-responsive breast cancer

Although pharmacologic therapies that reduce or block estrogen signaling are effective treatments of estrogen receptor (ER)-positive breast cancer, acquired resistance to individual drugs can develop. Furthermore, this approach is ineffective as initial therapy for a subgroup of receptor-positive patients. The mechanisms of drug resistance are not completely understood, but the presence of alternative signaling pathways for activating ER response appears to play a significant role. Cross-talk between signaling pathways can activate ERs when conventional ER pathways are blocked or inactivated. For example, signaling via epidermal growth factor or HER-2 receptors, mitogen-activated protein kinases, phosphatidylinositol 3' kinase/protein kinase B, and vascular endothelial growth factor receptor can lead to estrogen-independent stimulation of ERs and tumor growth. The discovery that alternative pathways are involved in estrogen signaling has prompted development of newer endocrine therapies, such as aromatase inhibitors and pure estrogen antagonists, with distinct mechanisms for interrupting signal transduction. The existence of multiple pathways may explain the effectiveness of follow-up therapy with a different class of endocrine agents after failure of prior endocrine treatment. Because they do not have the partial agonist activity of tamoxifen that is enhanced by the adaptive hypersensitivity process, these alternative endocrine agents may play an increasingly important role in the treatment of ER-positive breast cancer. Although optimal sequencing of these agents has not been determined and is continuing to evolve, current evidence allows rational recommendations to be made. The multiple pathways involved in activating ERs also provide a rationale for combining endocrine and non-endocrine therapies that block different signaling pathways, which may have synergistic and overlapping interactions.

Proteomics of xenografted human breast cancer indicates novel targets related to tamoxifen resistance

Tamoxifen is the most frequently used drug for hormone therapy of breast cancer patients, even though a high percentage of women are (or become) refractory to this treatment. The proteins involved in tamoxifen resistance of breast tumor cells as well as the mechanisms by which they interact, are still unknown. Some years ago, we established the xenograft breast tumor 3366, sensitive to tamoxifen and the 3366/TAM, resistant to tamoxifen, derived after two years of in vivo passages of the parental 3366 under tamoxifen treatment. Here, we compare the protein expression levels of both xenografts. 2-DE of proteins from total cell extracts showed very high reproducibility among tumors from each group (tamoxifen sensitive and tamoxifen resistant). The heuristic clustering analysis of these gels pooled them correctly in both groups. Twelve proteins were found up-regulated in the tamoxifen-resistant line, while nine were down-regulated. The proteins differentially expressed were identified by MS and sequence database analysis. Biological functions of these proteins are related to cell-cell adhesion and interaction, signal transduction, DNA and protein synthesis machinery, mitochondrial respiratory chain, oxidative stress processes and apoptosis. Three of the identified proteins (ALG-2 interacting protein and two GDP-dissociation inhibitors) could be directly involved in the resistance phenomenon.

Distinct gene expression patterns in a tamoxifen-sensitive human mammary carcinoma xenograft and its tamoxifen-resistant subline MaCa 3366/TAM

The reasons why human mammary tumors become resistant to tamoxifen therapy are mainly unknown. Changes in gene expression may occur as cells acquire resistance to antiestrogens. We therefore undertook a comparative gene expression analysis of tamoxifen-sensitive and tamoxifen-resistant human breast cancer in vivo models using Affymetrix oligonucleotide arrays to analyze differential gene expression. Total RNAs from the tamoxifen-sensitive patient-derived mammary carcinoma xenograft MaCa 3366 and the tamoxifen-resistant model MaCa 3366/TAM were hybridized to Affymetrix HuGeneFL and to Hu95Av2 arrays. Pairwise comparisons and clustering algorithms were applied to identify differentially expressed genes and patterns of gene expression. As revealed by cluster analysis, the tamoxifen-sensitive and the tamoxifen-resistant breast carcinomas differed regarding their gene expression pattern. More than 100 transcripts are changed in abundance in MaCa 3366/TAM as compared with MaCa 3366. Among the genes that are differentially expressed in the tamoxifen-resistant tumors, there are several IFN-inducible and estrogen-responsive genes, and genes known to be involved in breast carcinogenesis. The genes neuronatin (NNAT) and bone marrow stem cell antigen 2 (BST2) were sharply up-regulated in MaCa 3366/TAM. The differential expression of four genes (NNAT, BST2, IGFBP5, and BCAS1) was confirmed by Taqman PCR. Our results provide the starting point for deriving markers for tamoxifen resistance by differential gene expression profiling in a human breast cancer model of acquired tamoxifen resistance. Finally, genes whose expression profiles are distinctly changed between the two xenograft lines will be further evaluated as potential targets for diagnostic or therapeutic approaches of tamoxifen-resistant breast cancer.

Change in expression of ER, bcl-2 and MIB1 on primary tamoxifen and relation to response in ER positive breast cancer

Pre-treatment oestrogen receptor (ER) expression in breast cancer predicts for rate of response to endocrine therapy but not for the quality or duration of response (DofR). ER is known to be down-regulated by anti-oestrogens. This study has tested the hypothesis that the degree of down-regulation of ER and the ER-regulated marker bcl-2 are associated with the quality and duration of tamoxifen response. 80 patients with ER+ve breast cancer (H-score > 10) receiving primary tamoxifen (n = 51 Stage I-II elderly; n = 29 Stage III) underwent sequential tumour biopsies for immunocytochemical assessment of ER, bcl-2 and the proliferation marker MIB1. Median follow-up is 45 months. By 6-months on therapy three patients had attained complete response (CR), 27 partial response (PR); 44 static disease (SD) and six progression (PD) by UICC criteria. Greater decrease in ER and bcl-2 H-score from pre-treatment to 6 weeks (p = 0.035, p = 0.037) and ER and bcl-2 H-score from pre-treatment to 6 months (p = 0.058, p = 0.036) were significantly associated with better quality of response (CR/PR vs SD/PD). Greater 6-week and 6-month reduction in bcl-2 H-score (p = 0.041, p = 0.036) and 6-week reduction in MIB1 (p = 0.013) were significantly correlated with longer DofR. This study demonstrates that greater down-regulation of ER and the ER-regulated protein bcl-2 on primary tamoxifen are significantly associated with a better quality of response and bcl-2 and the proliferation marker MIB1 a longer duration of response in ER+ve breast cancer.

Flow cytometric analysis of estrogen receptor expression in isolated nuclei and cells from mammary cancer tissues

BACKGROUND

Cellular expression of receptors for the hormones estrogen and progesterone in human mammary tumors is of diagnostic and prognostic value. Ligand binding assays have been replaced by immunohistochemical analysis of receptor expression. However, both of these techniques are slow, and in the ligand-binding assay it is difficult to measure heterogeneity of receptor expression in individual cells. Flow cytometry has been used extensively for monitoring the expression of cellular receptors in hematopoietic tumors but has been of limited value in the analysis of mammary tumors, which are difficult to disaggregate into single cells for flow analysis. Hormone receptors have a predominant nuclear localization, and it is relatively easy to isolate nuclei from paraffin-embedded archival tissues for flow cytometric analysis of receptor expression.

METHODS

Thick sections from formalin-fixed paraffin-embedded archival mammary tumors were digested by different enzyme solutions for the isolation of single nuclei. Different fixatives were used to compare the results on subsequent staining of the nuclei for estrogen receptor (ER) expression. Double staining with propidium iodide and fluorescein isothiocyanate labeled secondary antibodies for ER expression was used for multiparametric analysis of ER and DNA content.

RESULTS

Digestion of paraffin sections with low concentration of pepsin and detergents was ideal for isolation of single nuclei. Fixation with paraformaldehyde in the presence of Triton X-100 improved staining of the cells. Isolated nuclei had enhanced immunoreactivity compared with the whole cells, and subpopulations differing in reactivity could be identified in the nuclear fractions. Double staining of nuclei for ER expression and DNA content could allow for multiparametric analysis of these two important parameters.

CONCLUSIONS

The procedures described can be used for processing of archival paraffin-embedded mammary tumors for monitoring of ER expression and aneuploidy. These two parameters have important diagnostic and prognostic significance in mammary tumors. Laser flow cytometry by providing multiparametric analysis can allow for correlation of these cellular markers with other important cellular and clinical parameters.

Onapristone, a progesterone receptor antagonist, as first-line therapy in primary breast cancer

The progesterone receptor antagonist, Onapristone, is an effective endocrine agent in experimental breast cancer models. This study aimed to investigate this agent as first-line endocrine therapy in patients with breast cancer. However, owing to the recognition in this and other clinical studies that some patients on Onapristone developed liver function test abnormalities, the development of this drug and recruitment to the study stopped in 1995. 19 patients either with locally advanced breast cancer (n = 12) or who were elderly, unfit patients with primary breast cancer (n = 7) received Onapristone 100 mg/day. Seventeen of the 19 tumours expressed oestrogen receptors (ER) whilst 12 of the 18 tumours tested expressed progesterone receptors (PgR). Tumour remission was categorised by International Union Against Cancer criteria. One patient was withdrawn after 4.5 months while her disease was static. Of the remaining 18 patients, 10 (56%) showed a partial response and 2 (11%) durable static disease (> or = 6 months), giving an overall tumour remission rate of 67%. The median duration of remission was 70 weeks. Transient liver function test abnormalities developed in a number of patients, mainly during the first 6 weeks of treatment. In conclusion Onapristone can induce tumour responses in human breast cancer.