Published OnlineFirst August 25, 2011; DOI: 10.1158/0008-5472.CAN-11-0362
Cancer Integrated Systems and Technologies Research
Activation of the Glucocorticoid Receptor Is Associated with Poor Prognosis in Estrogen Receptor-Negative Breast Cancer
Deng Pan1, Masha Kocherginsky2, and Suzanne D. Conzen1,3
Abstract Estrogen receptor–negative (ER ) breast cancers have limited treatment options and are associated with earlier relapses. Because glucocorticoid receptor (GR) signaling initiates antiapoptotic pathways in ER breast cancer cells, we hypothesized that activation of these pathways might be associated with poor prognosis in ER disease. Here we report findings from a genome-wide study of GR transcriptional targets in a premalignant ER cell line model of early breast cancer (MCF10A-Myc) and in primary early-stage ER human tumors. Chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq) coupled to time-course expression profiling led us to identify epithelial-to-mesenchymal transition (EMT) pathways as an important aspect associated with GR activation. We validated these findings by carrying out a meta-analysis of primary breast tumor gene expression from 1,378 early-stage breast cancer patients with long-term clinical follow-up, confirming that high levels of GR expression significantly correlated with shorter relapse-free survival in ER patients who were þ treated or untreated with adjuvant chemotherapy. Notably, in ER breast cancer patients, high levels of GR expression in tumors were significantly associated with better outcome relative to low levels of GR expression. Gene expression analysis revealed that ER tumors expressing high GR levels exhibited differential activation of EMT, cell adhesion, and inflammation pathways. Our findings suggest a direct transcriptional role for GR in determining the outcome of poor-prognosis ER breast cancers. Cancer Res; 71(20); 6360–70. 2011 AACR.
þ Introduction than ER tumors; second, underlying signaling pathways driving ER breast cancer have been difficult to identify in þ Breast cancer, the most frequent cancer in women, is part because of ER tumor heterogeneity. Compared with ER þ generally classified into estrogen receptor–positive (ER ) tumors, relatively few prevention and treatment strategies are and estrogen receptor–negative (ER ) subtypes because of available for ER breast cancer patients (5, 6). Until recently, the strong prognostic and predictive importance of ER-alpha the only clinically effective treatment for ER breast cancer þ (1, 2). ER-alpha expression (henceforth, ER ) is associated was cytotoxic chemotherapy. More recently, antiangiogenic with a significantly lower 5-year recurrence rate in part and PARP inhibitors have been explored as treatments for ER because of the effectiveness of ER-targeted treatments (3) breast cancer (7), although their ultimate effectiveness in the and in part because of a generally more indolent and well- ER breast cancer subgroup is not yet clear. Despite the fact differentiated phenotype when compared with ER tumors that many "triple-negative" [i.e., ER , progesterone receptor– (2, 4). As a consequence, identifying ER-positivity (usually negative (PR ), and HER2 ] breast cancers are highly sensitive through immunohistochemistry or IHC) has become routine to chemotherapy, a significant proportion show resistance to clinical practice. Unfortunately, the progress made in treating chemotherapy and progress rapidly (8). ER breast cancer has been less successful. First, ER tumors Recently, the stress hormone (glucocorticoid) receptor (GR) are often intrinsically more aggressive and of higher grade was shown to play an important role in breast epithelial and breast cancer cell biology, particularly in ER premalignant þ and breast cancer cell lines (9–11). Using ER /GR breast Authors' Affiliations: 1Department of Medicine, 2Department of Health epithelial and cancer cell lines (e.g., MCF10A-Myc and MDA- Studies, and 3Ben May Cancer Research, The University of Chicago, MB-231) and global gene expression studies, our laboratory Chicago, Illinois identified several GR-regulated target genes whose protein Note: Supplementary data for this article are available at Cancer Research products mediate cell survival, including serine/threonine- Online (http://cancerres.aacrjournals.org/). protein kinase 1 (SGK1; ref. 12) and the dual specificity protein Corresponding Author: Suzanne D. Conzen, Department of Medicine, DUSP1/MKP1 The University of Chicago, 900 East 57th Street, KCBD 8102, Chicago, IL phosphatase 1 ( ; ref. 13). In addition, using a 60637. Phone: 773-834-2604; Fax: 773-702-9268; E-mail: mouse xenograft model of MDA-MB-231 breast cancer cell [email protected] tumor growth, we found that tumor cell apoptosis induced by doi: 10.1158/0008-5472.CAN-11-0362 paclitaxel is inhibited by pretreatment with systemic dexa- 2011 American Association for Cancer Research. methasone (dex, a synthetic glucocorticoid; ref. 14). We also
6360 Cancer Res; 71(20) October 15, 2011
Downloaded from cancerres.aacrjournals.org on October 2, 2021. © 2011 American Association for Cancer Research. Published OnlineFirst August 25, 2011; DOI: 10.1158/0008-5472.CAN-11-0362
GR in ER-Negative Breast Cancer
discovered that increased endogenous glucocorticoid An anti-GR Western blot analysis was carried out on a small exposure is associated with greater ER mammary tumor percentage of the input lysate and the anti-GR immunopre- growth in the C3(1) SV40 Tag transgenic mouse model of cipitate to assess enrichment of GR by the immunoprecipi- þ ER /PR /GR invasive breast cancer (15). These observations tation process (Supplementary Fig. S1). Cell lysates or suggest that GR signaling may be an important pathway immunoprecipitated complexes were resuspended in 2 influencing ER breast cancer biology. Laemmli lysis buffer. The proteins were resolved by SDS- To further understand the role of GR signaling in ER breast PAGE, transferred to nitrocellulose membrane, blocked with cancer, we carried out genome-wide GR chromatin immuno- 5% skim milk in TBS-T (0.1% Tween-20 in TBS), and probed precipitation-sequencing (ChIP-seq) and time-course gene with a 1:1,000 dilution anti-GR antibody (sc-1003; Santa Cruz). þ expression analysis, using the ER /GR premalignant breast Goat anti-rabbit horseradish peroxidase (HRP; Santa Cruz; epithelial cell line MCF10A-Myc. We found that GR target 1:5,000) was used as the secondary antibody. Proteins were genes were enriched in many cancer-related pathways, in- visualized by enhanced chemiluminescence (Amersham cluding epithelial-to-mesenchymal transition (EMT), cell ad- Pharmacia Biotech). After confirming efficient GR immuno- hesion, and cell survival. In addition, to examine whether GR- precipitation (Supplementary Fig. S1A and B), we reversed the mediated gene expression associates with worse outcome in cross-links of the immunoprecipitated protein–chromatin ER breast cancer patients, we compiled and analyzed a meta- complexes according to the manufacturer's instructions. ChIP dataset of early-stage breast cancer patients with associated DNA was then purified by Qiagen's PCR Purification KIT. tumor gene expression and long-term clinical outcome data. In this retrospective analysis of primary tumor gene expres- Quantitative real-time PCR sion data in 1,378 patients, we found that high GR gene To ensure the quality of the anti-GR antibody ChIP'd DNA, (NR3C1) expression was associated with a significantly shorter we carried out quantitative real-time PCR (qRT-PCR) as relapse-free survival (RFS) in both adjuvant chemotherapy– previously described (13) on the promoter regions of SGK1 treated and untreated early-stage ER patients. Unexpectedly, and TSC22D3/GILZ genes containing established GR binding þ we also found that in ER breast cancer, higher GR expression regions (GBR; refs. 17, 18). The primers for SGK1's promoter was associated with longer RFS. Thus, both the cell line and regions were 50-CCCCTCCCTTCGCTTGTT-30 (sense) and 50- primary human tumor data analyses suggest that the GR GGAAGAAGTACAATCTGCATTTCACT-30 (antisense; ref. 19); directly mediates gene expression pathways associated with the primers for TSC22D3/GILZ's promoter regions were aggressive behavior and early relapse in the ER breast cancer 50-GATACCAGTTAAGCTCCTGA-30 (sense) and 50-AGGTGG- subtype. GAGACAATAATGAT-30 (antisense; ref. 20). Dex- and ethanol-treated ChIP DNA and input samples were analyzed Materials and Methods in triplicate.
Cell culture Deep sequencing and data analysis for ChIP-sequencing Early passage MCF10A-Myc cells were derived from After the quality control experiments described earlier MCF10A cells (ATCC), transduced with the viral oncogene proved to be successful, the GR ChIP DNA was deep- c-Myc as previously described (9), and checked for Myc sequenced by using Illumina's Solexa sequencer [National expression. Cells were cultured in a 1:1 mixture of Dulbecco's Center for Genome Resources (NCGR)]. We used the Maq modified Eagle's medium and Ham's F12 (BioWhittaker) program (version 0.71; ref. 21) to align the resulting sequenced supplemented with hydrocortisone (0.5 mg/mL), human re- 36-bp tags to the Human Genome (NCBI/b36). Tags that were combinant epidermal growth factor (10 ng/mL), insulin (5 ng/ mapped to more than one location in the human genome were mL), 5% FBS, 100 units/mL penicillin, and 100 mg/mL strep- removed. The GBRs were identified using the Model-based tomycin. Identical conditions were used for gene expression analysis of ChIP-Seq (MAC) program (version 1.3.7.1; ref. 22). profiling after dex treatment (16). Input DNA tags were used to call GBRs. A P value cutoff of 10 3 or less was initially used to call the GR ChIP assay GBRs in both dex- and ethanol-treated samples. We then MCF10A-Myc cells (1 107) were serum starved for developed more stringent criteria for accurately detecting 3 days and then treated with either dex or ethanol for 1 significant peak signals based on known GR promoter occu- hour as previously described (9). Cellular DNA and protein pancy regions for the 2 GR target genes, SGK1 (19) and were then cross-linked for 20 minutes with formaldehyde TSC22D3/GILZ (20). In the initial P 10 3 GBR dataset, we N (1% final concentration) followed by addition of glycine to a found the number of tags per binding region ( tag) in all the final concentration of 125 mmol/L for 5 minutes. We also SGK1 and TSC22D3/GILZ–associated GBRs in ethanol-treated took 1% of each lysate to evaluate as input protein and samples was always 6 or less, whereas Ntag in dex-treated DNA. ChIP experiments were conducted according to a samples was always 5 or more (see Supplementary Table S1 for standard protocol (Upstate Biotechnology, Millipore). the summary of SGK1 and TSC22D3/GILZ GBR data). Because ChIP-grade rabbit polyclonal anti-GR (sc-1003x; Santa ethanol-treated samples should not show significant GR Cruz) antibodies were used for immunoprecipitation. We occupancy for these 2 previously described dex-dependent N > also used normal rabbit IgG (sc-2027; Santa Cruz) as a GBRs, an tag 6 was determined as the cutoff for removing negative control. non-dex-dependent GBRs associated with ethanol treatment.
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Pan et al.