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AR ER protein densitometry and dose response to PI3K/mTORi

Gene changes in MCF7aro. The impact of cyp19 overexpression on SGK3 expression in an independent study. Impact of siRNA-AR/ER on SGK3 mRNA

Supplemental tables 1& 2

Impact of SiSGK3 in ZRaroLetR. MTS following siSGK3 under various hormonal stimuli.

Characterisation of ZR75aro-LetR. Validation of ER AR siRNA

Correlation between CYP19 amplification and SGK3 expression.

AR and ER binding events in the proximal promoters of SGK3, MYBL1, GREB1 and PKIB.

Supplemental methods

Divergent roles for androgen receptor (AR) in breast cancer have been reported. Following aromatase inhibitor (AI) treatment, the conversion of circulating androgens into estrogens can be diminished by >99%. We wished to establish whether the steroid environment can dictate the role of AR and the implications of this for subsequent therapy. This study utilizes models of AI resistance to explore responsiveness to PI3K/mTOR and anti-AR therapy when cells are exposed to unconverted weak androgens. Transcriptomic alterations driven by androstenedione (4AD) were assessed by RNA-sequencing. AR and estrogen receptor (ER) recruitment to target gene promoters was evaluated using ChIP, and relevance to patient profiles was performed using publicly available data sets. Although BEZ235 showed decreased viability across AI-sensitive and -resistant cell lines, anti-AR treatment elicited a decrease in cell viability only in the AI-resistant model. Serum and glucocorticoid-regulated kinase 3 (SGK3) and cAMP-dependent protein kinase inhibitor β (PKIB) were confirmed to be regulated by 4AD and shown to be mediated by AR; crucially, reexposure to estradiol suppressed expression of these genes. Meta-analysis of transcript levels showed high expression of SGK3 and PKIB to be associated with poor response to endocrine therapy (HR = 2.551, P = 0.003). Furthermore, this study found levels of SGK3 to be sustained in patients who do not respond to AI therapy. This study highlights the importance of the tumor steroid environment. SGK3 and PKIB are associated with poor response to endocrine therapy and could have utility in tailoring therapeutic approaches.

Purpose: Disease recurrence is a common problem in breast cancer and yet the mechanisms enabling tumor cells to evade therapy and colonize distant organs remain unclear. We sought to characterize global expression changes occurring with metastatic disease progression in the endocrine-resistant setting.Experimental Design: Here, for the first time, RNAsequencing has been performed on matched primary, nodal, and liver metastatic tumors from tamoxifen-treated patients following disease progression. Expression of genes commonly elevated in the metastases of sequenced patients was subsequently examined in an extended matched patient cohort with metastatic disease from multiple sites. The impact of tamoxifen treatment on endocrine-resistant tumors in vivo was investigated in a xenograft model.Results: The extent of patient heterogeneity at the gene level was striking. Less than 3% of the genes differentially expressed between sequential tumors were common to all patients. Larger divergence was observed between primary and liver tumors than between primary and nodal tumors, reflecting both the latency to disease progression and the genetic impact of intervening therapy. Furthermore, an endocrine-resistant in vivo mouse model demonstrated that tamoxifen treatment has the potential to drive disease progression and establish distant metastatic disease. Common functional pathways altered during metastatic, endocrine-resistant progression included extracellular matrix receptor interactions and focal adhesions.Conclusions: This novel global analysis highlights the influence of primary tumor biology in determining the transcriptomic profile of metastatic tumors, as well as the need for adaptations in cell–cell communications to facilitate successful tumor cell colonization of distant host organs. Clin Cancer Res; 21(23); 5371–9. ©2015 AACR.

Supplementary Figure S1 from Coassociation of Estrogen Receptor and p160 Proteins Predicts Resistance to Endocrine Treatment; SRC-1 is an Independent Predictor of Breast Cancer Recurrence

Supplementary Table S4: Patient information for patients A-L

Supplementary Figures S1-7. Supplementary Figure S1: Gene expression profiles of classic biomarkers in matched tumour samples from 3 patients. Supplementary Figure S2: Network map showing the enriched KEGG pathways from upregulated differentially expressed genes (DEGs). Supplementary Figure S3: Network map showing the enriched KEGG pathways from downregulated differentially expressed genes (DEGs). Supplementary Figure S4: Protein expression in matched primary and metastatic tissue from endocrine treated breast cancer patients. Supplementary Figure S5: Phosphorylated mTOR signaling in endocrine resistant breast cancer tumours. Supplementary Figure S6: Interaction plot showing functional roles for 21 genes commonly upregulated in metastatic liver tumours of all three patients. Supplementary Figure S7: Genes upregulated in liver metastases are also strongly expressed in breast metastases to the brain.

Purpose: This study investigates the role of the p160 coactivators AIB1 and SRC-1 independently, and their interactions with the estrogen receptor, in the development of resistance to endocrine treatments.Experimental Design: The expression of the p160s and the estrogen receptor, and their interactions, was analyzed by immunohistochemistry and quantitative coassociation immunofluorescent microscopy, using cell lines, primary breast tumor cell cultures, and a tissue microarray with breast cancer samples from 560 patients.Results: Coassociation of the p160s and estrogen receptor α was increased in the LY2 endocrine-resistant cell line following treatment with tamoxifen in comparison with endocrine-sensitive MCF-7 cells. In primary cultures, there was an increase in association of the coactivators with estrogen receptor α following estrogen treatment but dissociation was evident with tamoxifen. Immunohistochemical staining of the tissue microarray revealed that SRC-1 was a strong predictor of reduced disease-free survival (DFS), both in patients receiving adjuvant tamoxifen treatment and untreated patients (P < 0.0001 and P = 0.0111, respectively). SRC-1 was assigned a hazard ratio of 2.12 using a Cox proportional hazards model. Endocrine-treated patients who coexpressed AIB1 with human epidermal growth factor receptor 2 had a significantly shorter DFS compared with all other patients (P = 0.03). Quantitative coassociation analysis in the patient tissue microarray revealed significantly stronger colocalization of AIB1 and SRC-1 with estrogen receptor α in patients who have relapsed in comparison with those patients who did not recur (P = 0.026 and P = 0.00001, respectively).Conclusions: SRC-1 is a strong independent predictor of reduced DFS, whereas the interactions of the p160 proteins with estrogen receptor α can predict the response of patients to endocrine treatment.

Supplementary Materials and Methods

PDF file - 93KB, PCR Primers and TaqMan qPCR Probes.

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PDF file - 72KB, Positive controls for transfection assays.

PDF file - 198KB, Mammary tumor growth and metastasis in Tg(TVA)+RCAS-PyMT and Tg(NCOA1)x Tg(TVA)+RCAS-PyMT mice.

PDF file - 368KB, Mammary gland morphogenesis and epithelial proliferation of Tg(NCOA1) mice.

Introduction Brain metastasis (BrM) occurs in 10-30% of patients with advanced breast cancer (BC). BrM is increasing in incidence and confers a poor prognosis. We aimed to investigate the contribution of global epi-transcriptomic alterations in N6-methyladenosine (m6A) RNA-methylation as a therapeutic target in brain metastatic breast cancer. Method In preliminary studies we have demonstrated m6A demethylase – FTO as the main contributor to the progression of ER+ breast cancer. Furthermore an association between FTO and reduced disease-free-survival (n=870, p=0.018) was observed. Here we conducted an epigenetic inhibitor screen using two therapeutic agents, ethyl-ester-meclofenamic acid (MA2) and FB23-2 on matched 2D cell line, 3D organoid cultures and patient-derived xenografts (PDX) explant models of brain metastasis. Result Upon integration of mapped global RNA methylation landscape with matched proteomic analysis, we observed genome-wide RNA hypo-methylation of key pluripotency genes, including SOX2 and KLF4, as key players underlying tumour progression to the brain. Genetic and pharmacological inhibition of FTO in novel ex vivo models of BrM significantly reduced protein expression levels of KLF4 and SOX2. Moreover, pharmacological inhibition of FTO with MA2 and FB23-2, inhibited cell proliferation in endocrine-resistant BC and patient BrM cells. We translate our findings to the clinic by demonstrating the efficacy of anti-FTO therapies in several unique PDX and 3D organoid BrM models. Conclusion Our results reveal epi-transcriptional remodelling events as a key mechanism in BrM. This study establishes an early role for targeting RNA methylation in the management of disease progression and presents FTO as a potential therapeutic target in BrM. Take-home message This study establishes an early role for targeting RNA methylation in the management of disease progression and presents FTO as a potential therapeutic target in brain metastatic breast cancer.

Introduction Therapeutic pressure functionally affects oncogenes and related signalling pathways through dynamic alterations in transcriptional and epigenetic alterations. Altered receptor status occurs throughout tumour progression and may be influenced by adjuvant and neoadjuvant therapies. Recurrent transcriptional remodelling events have been described in the progression of primary breast cancer to metastasis, including increased tyrosine kinase signalling, specifically Her2, and loss of ESR1 gene expression. We hypothesise that in the setting of tyrosine kinase inhibition, an increase in estrogen receptor (ER) signalling is observed. Method A database of patients recruited to ICORG trial 07/09 was queried to identify patients with histologically confirmed, Her2-overexpressing or Her2 amplified, nonmetastatic, invasive breast cancer who received neoadjuvant trastuzumab, alone or in combination with neoadjuvant systemic chemotherapy. Clinicopathological characteristics recorded include age at diagnosis, clinical stage, receptor status and percentage positivity, and pathological complete response. Result A total of 55 patients identified on ICORG trial 09/07 received neoadjuvant trastuzumab. Of these, 27 achieved a complete pathological response (49%; n=27/55). In those with residual disease, a gain in mean ER staining percentage positivity was observed in the residual disease compared to diagnostic biopsy staining (59.22 vs 45.11; p=0.03). A corresponding loss in Her2 percentage staining positivity was also observed (p=0.006). Conclusion An inverse correlation was observed between loss of Her2 positivity and percentage gain in ER staining in patients with residual disease following treatment with neoadjuvant trastuzumab. Further study is needed to elucidate the regulatory mechanism of ER/Her2 crosstalk, which may be epigenetically regulated through DNA methylation. Take-home message ER/Her2 crosstalk can be demonstrated clinically in IHC analysis of patients with residual disease post neoadjuvant trastuzumab. Tyrosine kinase inhibition in the form of neoadjuvant trastuzumab results in loss of Her2 signalling and corresponding gain in ER signalling.

Funder: Breast Cancer Ireland GR 14-0883, Steroid regulated cancer cells use nuclear receptors and associated regulatory proteins to orchestrate transcriptional networks to drive disease progression. In primary breast cancer, the coactivator AIB1 promotes estrogen receptor (ER) transcriptional activity to enhance cell proliferation. The function of the coactivator in ER+ metastasis however is not established. Here we describe AIB1 as a survival factor, regulator of pro-metastatic transcriptional pathways and a promising actionable target. Genomic alterations and functional expression of AIB1 associated with reduced disease-free survival in patients and enhanced metastatic capacity in novel CDX and PDX ex-vivo models of ER+ metastatic disease. Comparative analysis of the AIB1 interactome with complementary RNAseq characterized AIB1 as a transcriptional repressor. Specifically, we report that AIB1 interacts with MTA2 to form a repressive complex, inhibiting CDH1 (encoding E-cadherin) to promote EMT and drive progression. We further report that pharmacological and genetic inhibition of AIB1 demonstrates significant anti-proliferative activity in patient-derived models establishing AIB1 as a viable strategy to target endocrine resistant metastasis. This work defines a novel role for AIB1 in the regulation of EMT through transcriptional repression in advanced cancer cells with a considerable implication for prognosis and therapeutic interventions.

Background Metastatic breast cancer is a major cause of cancer-related deaths in woman. Brain metastasis is a common and devastating site of relapse for several breast cancer molecular subtypes, including oestrogen receptor-positive disease, with life expectancy of less than a year. While efforts have been devoted to developing therapeutics for extra-cranial metastasis, drug penetration of blood–brain barrier (BBB) remains a major clinical challenge. Defining molecular alterations in breast cancer brain metastasis enables the identification of novel actionable targets. Methods Global transcriptomic analysis of matched primary and metastatic patient tumours (n = 35 patients, 70 tumour samples) identified a putative new actionable target for advanced breast cancer which was further validated in vivo and in breast cancer patient tumour tissue (n = 843 patients). A peptide mimetic of the target’s natural ligand was designed in silico and its efficacy assessed in in vitro, ex vivo and in vivo models of breast cancer metastasis. Results Bioinformatic analysis of over-represented pathways in metastatic breast cancer identified ADAM22 as a top ranked member of the ECM-related druggable genome specific to brain metastases. ADAM22 was validated as an actionable target in in vitro, ex vivo and in patient tumour tissue (n = 843 patients). A peptide mimetic of the ADAM22 ligand LGI1, LGI1MIM, was designed in silico. The efficacy of LGI1MIM and its ability to penetrate the BBB were assessed in vitro, ex vivo and in brain metastasis BBB 3D biometric biohybrid models, respectively. Treatment with LGI1MIM in vivo inhibited disease progression, in particular the development of brain metastasis. Conclusion ADAM22 expression in advanced breast cancer supports development of breast cancer brain metastasis. Targeting ADAM22 with a peptide mimetic LGI1MIM represents a new therapeutic option to treat metastatic brain disease.

Steroid receptor coactivator 1 (SRC-1) interacts with nuclear receptors and other transcription factors (TFs) to initiate transcriptional networks and regulate downstream genes which enable the cancer cell to evade therapy and metastasise. Here we took a top–down discovery approach to map out the SRC-1 transcriptional network in endocrine resistant breast cancer. First, rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) was employed to uncover new SRC-1 TF partners. Next, RNA sequencing (RNAseq) was undertaken to investigate SRC-1 TF target genes. Molecular and patient-derived xenograft studies confirmed STAT1 as a new SRC-1 TF partner, important in the regulation of a cadre of four SRC-1 transcription targets, NFIA, SMAD2, E2F7 and ASCL1. Extended network analysis identified a downstream 79 gene network, the clinical relevance of which was investigated in RNAseq studies from matched primary and local-recurrence tumours from endocrine resistant patients. We propose that SRC-1 can partner with STAT1 independently of the estrogen receptor to initiate a transcriptional cascade and control regulation of key endocrine resistant genes.

Purpose: Disease recurrence is a common problem in breast cancer and yet the mechanisms enabling tumor cells to evade therapy and colonize distant organs remain unclear. We sought to characterize global expression changes occurring with metastatic disease progression in the endocrine-resistant setting. Experimental Design: Here, for the first time, RNAsequencing has been performed on matched primary, nodal, and liver metastatic tumors from tamoxifen-treated patients following disease progression. Expression of genes commonly elevated in the metastases of sequenced patients was subsequently examined in an extended matched patient cohort with metastatic disease from multiple sites. The impact of tamoxifen treatment on endocrine-resistant tumors in vivo was investigated in a xenograft model. Results: The extent of patient heterogeneity at the gene level was striking. Less than 3% of the genes differentially expressed between sequential tumors were common to all patients. Larger divergence was observed between primary and liver tumors than between primary and nodal tumors, reflecting both the latency to disease progression and the genetic impact of intervening therapy. Furthermore, an endocrine-resistant in vivo mouse model demonstrated that tamoxifen treatment has the potential to drive disease progression and establish distant metastatic disease. Common functional pathways altered during metastatic, endocrine-resistant progression included extracellular matrix receptor interactions and focal adhesions. Conclusions: This novel global analysis highlights the influence of primary tumor biology in determining the transcriptomic profile of metastatic tumors, as well as the need for adaptations in cell–cell communications to facilitate successful tumor cell colonization of distant host organs. Clin Cancer Res; 21(23); 5371–9. ©2015 AACR.

Disease recurrence is a common problem in breast cancer and yet the mechanisms enabling tumour cells to evade therapy and colonise distant organs remain unclear. Here, for the first time, RNAsequencing has been performed on matched primary, nodal and liver metastatic tumours from three tamoxifen-treated patients following metastatic disease progression. Despite all primary tumours being of a luminal subtype and all cancers metastasising to the liver, the extent of patient heterogeneity at the gene level was striking. Less than 3% of the genes differentially expressed between sequential tumours were common to all patients. Larger divergence was observed between primary and liver tumours than between primary and nodal tumours, reflecting both the latency time to disease progression and the genetic impact of endocrine therapy. Furthermore, a xenograft model demonstrated the ability of tamoxifen to drive disease progression and establish distant metastatic disease in the endocrine resistant setting. Common functional pathways altered during metastatic, endocrine-resistant progression included ECM receptor interactions and focal adhesions. This novel global analysis highlights the influence of primary tumour biology in determining the transcriptomic profile of metastatic tumours, as well as the need for adaptations in cell-cell communications in order for tumour cells to successfully colonise distant host organs. Citation Format: Jean McBryan, Ailis Fagan, Damian McCartan, Jarlath C Bolger, Fiona T Bane, Christopher Byrne, Marie McIlroy, Arnold D Hill, Leonie S Young. Transcriptomic profiling of patient sequential tumours provides cutting edge view of global metastatic expression changes following endocrine therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-05-13.

Breast cancer resistance to endocrine therapies such as tamoxifen and aromatase inhibitors is a significant clinical problem. Steroid receptor coactivator-1 (SRC-1), a coregulatory protein of the oestrogen receptor (ER), has previously been shown to have a significant role in the progression of breast cancer. The chromatin protein high mobility group box 2 (HMGB2) was identified as an SRC-1 interacting protein in the endocrine-resistant setting. We investigated the expression of HMGB2 in a cohort of 1068 breast cancer patients and found an association with increased disease-free survival time in patients treated with endocrine therapy. However, it was also verified that HMGB2 expression could be switched on in endocrine-resistant tumours from breast cancer patients. To explore the function of this poorly characterized protein, we performed HMGB2 ChIPseq and found distinct binding patterns between the two contexts. In the resistant setting, the HMGB2, SRC-1 and ER complex are enriched at promoter regions of target genes, with bioinformatic analysis indicating a switch in binding partners between the sensitive and resistant phenotypes. Integration of binding and gene expression data reveals a concise set of target genes of this complex including the RNA helicase DDX18. Modulation of DDX18 directly affects growth of tamoxifen-resistant cells, suggesting that it may be a critical downstream effector of the HMGB2:ER complex. This study defines HMGB2 interactions with the ER complex at specific target genes in the tamoxifen-resistant setting.

Breast cancer has the highest incidence and second highest mortality rate among all cancers in women worldwide (1). The gold standard treatment for post-menopausal breast cancer is aromatase inhibitor (AI) therapy. Unfortunately, resistance is inevitable in about 30-60% of these patients (2). Research from our lab has previously identified a transcription factor, HOXC11, to be associated with breast cancer resistance and metastases (3). Prosaposin (PSAP) was then identified as a putative HOXC11 target gene in the AI resistant setting. PSAP is a secreted protein that also plays a role in metastatic prostate cancer in both a ligand dependent and independent fashion (4,5). We have previously shown PSAP to be an androgen responsive gene that can upregulate androgen receptor (AR) expression in a ligand dependent manner in AI resistance. An AR antagonist was effective at slowing down cell proliferation in AI resistant cells in vitro . However, since PSAP can also potentially act in a ligand independent fashion, this current study is focused on evaluating the role of PSAP in PI3K pathway activation in the development of AI resistance. Treatment of cells with recombinant PSAP protein (rhPSAP) resulted in increasing expression of p-AKT in a dose-dependent manner. To target this pathway of resistance, we used a pan-class PI3K/mTOR inhibitor BEZ235 on our AI resistant cells. Functional studies with BEZ235 treatment showed significant reduction in both cell motility as well as cell proliferation. Treatment of AI resistant cells with BEZ235 resulted in decreased expression of p-AKT, with little or no effect on AR expression. These findings suggest that to prevent resistance to AI therapy, combination treatment regimens including AR antagonists plus a PI3K inhibitor may ensure sustained response to therapy. References: 1. Servick K. Breast Cancer: a World of Differences. Science Magazine. Special Issue. March 2014 2. Kazi AA et al. Breast Nonhypoxic regulation and role of hypoxia-inducible factor 1 in aromatase inhibitor resistant breast cancer. Cancer Research. 2014; 16:R15 3. McIlroy M et al. Cancer Res.2010;70(4);1585-94 4. Koochekpour Set al. Prosaposin is an AR-target gene and its neurotrophic domain upregulates AR expression and activity in prostate stromal cells. J Cell Biochem. 2008; 104: 2272–2285. 5. Koochekpour S et al. Prosaposin is a novel androgen-regulated gene in prostate cancer cell line LNCaP. J Cell Biochem. 2007; 10: 631–641. Citation Format: Leonie S Young, Azlena Ali, Laura Creevey, Fiona Bane, Wan Afif Marzuki, Arnold DK Hill, Marie McIlroy. PI3K pathway as a novel target in androgen-driven aromatase inhibitor resistant breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-05-22.

Treatment with tyrosine kinase inhibitors (TKIs) including trastuzumab has revolutionized the management of HER2-positive breast cancer. Recent evaluation of clinical trial data suggests that a subset of HER2/ER double-positive cancers may not receive significant benefit from the TKI therapy. Here we investigate the cross talk between HER2 and ER in breast cancer and monitor the effect of trastuzumab on the tyrosine kinase effector transcription factor Myc. In HER2-positive breast cancer patients treated with neoadjuvant trastuzumab, steroid receptor-negative status (ER and PR negative) of pre-treatment biopsies predicted pathological complete response (pCR) (n=31 patients, P=0.0486), whereas elevated Myc protein inversely associated with pCR (P=0.0446). Liquid chromatography mass spectrometry identified the corepressor SMRT as a novel Myc-interacting protein. Trastuzumab treatment enhanced Myc-SMRT interactions in HER2-overexpressing breast cancer cells (LCC1) and inhibited expression of the Myc target gene survivin. In HER2-low, ER-positive steroid-dominant cells (MCF7), trastuzumab therapy repressed Myc-SMRT interactions and upregulated survivin expression. Trastuzumab treatment induced ER-CBP interactions, enhanced ER transcriptional activity and upregulated expression of the ER target gene pS2. The absence of pS2 expression in pre-treatment biopsies predicted pCR to neoadjuvant trastuzumab in breast cancer patients (n=25, P=0.0089) and pS2 expression associated with residual cancer burden (P=0.0196). Furthermore, metastatic tissues from patients who had failed trastuzumab therapy were pS2 positive. In HER2-overexpressing cells, trastuzumab treatment can repress Myc transcriptional activity and clinical response is favorable. However, with co-expression of the steroid pathway, this inhibition is lost and response to treatment is often poor.

Associations between p160 coactivator proteins and endocrine resistance have been described. Though thought to primarily interact with steroid receptors, the p160 proteins can also interact with non-nuclear receptor transcription factors including the MAP kinase effector proteins Ets. Here, we observed that in breast cancer cells resistant and insensitive to endocrine treatment, the growth factor EGF induced Ets-2 but not Ets-1 transcriptional regulation of the oncogene myc. Ets-2 regulation of myc was found to be reliant on the p160 proteins SRC-1 and SRC-3. In support of these molecular observations, strong associations were observed between the transcription factor, Ets-2 and its coactivator SRC-1 (P

Aromatase Inhibitors have proven to be most effective in the treatment of post-menopausal breast cancer. Their mode of action is to inhibit the synthesis of estrogen (estrone) by the aromatase enzyme Cyp 19 thereby blocking ligand-dependent activation of the estrogen receptor. What has not been addressed to date is how cells that are deprived of estrogen, may potentially, adapt to the more androgenic environment resulting from long-term treatment with AI therapy. Research from our lab has identified the homeobox protein, HOXC11, to be an indicator of poor response to endocrine therapy and development of metastasis. To further our understanding of HOXC11 and its role in the development of endocrine-resistance and metastatic spread we undertook an RNA-seq experiment to identify its target genes in resistant breast cancer. This analysis identified PSAP, IFIT1 and HSP90AA1. Both PSAP (an androgen agonist) and HSP90AA1 (AR chaperone) are closely associated with AR which led to further investigation into the role of HOXC11 in the development of steroidal adaptability in Letrozole-resistant breast cancer. We hypothesize that HOXC11 regulated expression of PSAP results in oncogenic activation of AR in an AI resistant setting. Our findings have shown that AI-resistant cell lines in vitro have significantly elevated levels of AR and that loss of HOXC11 results in concommitant decrease in AR mRNA. In AI resistance expression of HOXC11 results in upregulation/stabilization of AR by PSAP thus enabling the tumour to adapt to use androgenic steroids for cell proliferation. The anti-androgen, Bicalutamide, reduces cell proliferation and cell motility in AI resistant cell lines. Survival analysis of AR in a TMA (n = 488) indicates that AR confers a survival benefit in the tamoxifen treated population. This protective effect is diminished in patients receiving AI therapy and is reflected in the altered Hazard Ratio of AR from the total population (HR: 0.485) to the AI treated cohort (HR: 1.197). Secreted PSAP was readily detectable in breast cancer patient serum and associates significantly with expression of HOXC11 in matched patient tissue (∼20). PSAP is associated with poor response to endocrine therapy and metastatic spread of prostate cancer and as it is secreted it could potentially be used to monitor patients on AI who might benefit from dual targeted therapy treatment. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD3-5.

In estrogen receptor positive breast cancer, endocrine therapy is the standard line of treatment and even though it results in reduced recurrence and mortality, a significant number of patients will eventually relapse. Early detection of metastatic disease would significantly enhance management of endocrine resistant breast cancer. Here we investigate the potential of the calcium-binding protein S100β as a predictive biomarker and monitoring tool in endocrine treated patients. Furthermore, the efficacy of S100β inhibition as therapy in patients that fail first line endocrine therapy was examined. Primary tumor tissue expression of S100β protein was assessed in a retrospective cohort of endocrine treated breast cancer patients. Expression of S100β indicated a significant reduction in time to disease recurrence (n=509, Wilcoxon p S100β protein is also detectable in serum of breast cancer patients and elevated levels of serum S100β prior to removal of primary tumor is associated with poor disease free survival in endocrine treated patients (n=190, Wilcoxon p=0.0367, hazard ratio 2.68, 95% C.I. is 1.12 to 6.41, p=0.026, Cox proportional hazard model). Serum levels of S100β are significantly reduced after primary tumor resection (n=19, p=0.0003). In serial samples taken during the treatment period, elevated levels of S100β significantly associated with disease progression and with the emergence of metastatic disease (p=0.0031). In an in-vivo model of endocrine resistant breast cancer, raised levels of S100β marked the emergence of disease progression. The oncogene steroid receptor co-activator 1 (SRC1) and its interaction with homeobox protein (HOXC11) regulates S100β production in a src-kinase dependent manner. Here, src-kinase inhibition reduced tumor burden with a concomitant reduction in serum S100β. We also observed a marked reduction in expression of proliferative marker Ki67 and S100β protein following the treatment of endocrine resistant patient tumor explants with src-kinase inhibitor. Associations between elevated levels of serum S100β and subsequent disease progression in endocrine treated patients, suggests S100β as a monitoring tool for early detection of disease progression. Additionally high level of S100β can be used as a potential companion diagnostic tool for stratifying patients on endocrine therapy suitable for treatment with small molecule src-kinase inhibitor. Citation Format: Charmsaz S, Hughes É, Byrne C, Bane F, Tibbitts P, McIlroy M, Hill AD, Young LS. S100β as a predictive biomarker and monitoring tool in endocrine resistant breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-03.

In breast cancer, overexpression of the nuclear coactivator NCOA1 (SRC-1) is associated with disease recurrence and resistance to endocrine therapy. To examine the impact of NCOA1 overexpression on morphogenesis and carcinogenesis in the mammary gland (MG), we generated MMTV-hNCOA1 transgenic [Tg(NCOA1)] mice. In the context of two distinct transgenic models of breast cancer, NCOA1 overexpression did not affect the morphology or tumor-forming capability of MG epithelial cells. However, NCOA1 overexpression increased the number of circulating breast cancer cells and the efficiency of lung metastasis. Mechanistic investigations showed that NCOA1 and c-Fos were recruited to a functional AP-1 site in the macrophage attractant CSF1 promoter, directly upregulating colony-simulating factor 1 (CSF1) expression to enhance macrophage recruitment and metastasis. Conversely, silencing NCOA1 reduced CSF1 expression and decreased macrophage recruitment and breast cancer cell metastasis. In a cohort of 453 human breast tumors, NCOA1 and CSF1 levels correlated positively with disease recurrence, higher tumor grade, and poor prognosis. Together, our results define an NCOA1/AP-1/CSF1 regulatory axis that promotes breast cancer metastasis, offering a novel therapeutic target for impeding this process. Cancer Res; 74(13); 3477–88. ©2014 AACR.

Purpose: The use of aromatase inhibitors (AI) in the treatment of estrogen receptor (ER)-positive, postmenopausal breast cancer has proven efficacy. However, inappropriate activation of ER target genes has been implicated in the development of resistant tumors. The ER coactivator protein AIB1 has previously been associated with initiation of breast cancer and resistance to endocrine therapy. Experimental Design: Here, we investigated the role of AIB1 in the deregulation of ER target genes occurring as a consequence of AI resistance using tissue microarrays of patients with breast cancer and cell line models of resistance to the AI letrozole. Results: Expression of AIB1 associated with disease recurrence (P = 0.025) and reduced disease-free survival time (P = 0.0471) in patients treated with an AI as first-line therapy. In a cell line model of resistance to letrozole (LetR), we found ERα/AIB1 promoter recruitment and subsequent expression of the classic ER target genes pS2 and Myc to be constitutively upregulated in the presence of both androstenedione and letrozole. In contrast, the recruitment of the ERα/AIB1 transcriptional complex to the nonclassic ER target cyclin D1 and its subsequent expression remained sensitive to steroid treatment and could be inhibited by treatment with letrozole. Molecular studies revealed that this may be due in part to direct steroid regulation of c-jun-NH2-kinase (JNK), signaling to Jun and Fos at the cyclin D1 promoter. Conclusion: This study establishes a role for AIB1 in AI-resistant breast cancer and describes a new mechanism of ERα/AIB1 gene regulation which could contribute to the development of an aggressive tumor phenotype. Clin Cancer Res; 18(12); 3305–15. ©2012 AACR.

Background: Cutaneous melanoma is an aggressive disease. S100beta is an established biomarker of disease progression; however, the mechanism of its regulation in melanoma is undefined. Methods: Expression of HOXC11 and SRC-1 was examined by immunohistochemistry and immunofluorescence. Molecular and cellular techniques were used to investigate regulation of S100beta, including, western blot, qPCR, ChIP and migration assays. Results: Expression levels of the transcription factor HOXC11 and its coactivator SRC-1 were significantly elevated in malignant melanoma in comparison with benign nevi (P

Epidemiological, clinical, and molecular studies suggest a role for oestrogen in thyroid cancer. How oestrogen mediates its effects and the consequence of it on clinical outcome has not been fully elucidated. The participation of coregulatory proteins in modulating oestrogen receptor (ER) function and input of crosstalk with the tyrosine kinase receptor HER2 was investigated. Oestrogen induced cell proliferation in the follicular thyroid cancer (FTC)-133 cells, but not in the anaplastic 8305C cell line. Knockdown of the coactivator steroid receptor coactivator (SRC)-1 inhibited FTC-133 basal, but not oestrogen induced, cell proliferation. Oestrogen also increased protein expression of SRC-1 and the ER target gene cyclin D1 in the FTC-133 cell line. ERα, ERβ, the coregulatory proteins SRC-1 and nuclear corepressor (NCoR), and the tyrosine kinase receptor HER2 were localised by immunohistochemistry and immnofluorescence in paraffin-embedded tissue from thyroid tumour patients (n=111). ERα was colocalised with both SRC-1 and NCoR to the nuclei of the tumour epithelial cells. Expression of ERα and NCoR was found predominantly in non-anaplastic tumours and was significantly associated with well-differentiated tumours and reduced incidence of disease recurrence. In non-anaplastic tumours, HER2 was significantly associated with SRC-1, and these proteins were associated with poorly differentiated tumours, capsular invasion and disease recurrence. Totally, 87% of anaplastic tumours were positive for SRC-1. Kaplan–Meier estimates of disease-free survival indicated that in thyroid cancer, SRC-1 strongly correlates with reduced disease-free survival (PP

Purpose: This study investigates the role of the p160 coactivators AIB1 and SRC-1 independently, and their interactions with the estrogen receptor, in the development of resistance to endocrine treatments. Experimental Design: The expression of the p160s and the estrogen receptor, and their interactions, was analyzed by immunohistochemistry and quantitative coassociation immunofluorescent microscopy, using cell lines, primary breast tumor cell cultures, and a tissue microarray with breast cancer samples from 560 patients. Results: Coassociation of the p160s and estrogen receptor α was increased in the LY2 endocrine-resistant cell line following treatment with tamoxifen in comparison with endocrine-sensitive MCF-7 cells. In primary cultures, there was an increase in association of the coactivators with estrogen receptor α following estrogen treatment but dissociation was evident with tamoxifen. Immunohistochemical staining of the tissue microarray revealed that SRC-1 was a strong predictor of reduced disease-free survival (DFS), both in patients receiving adjuvant tamoxifen treatment and untreated patients (P < 0.0001 and P = 0.0111, respectively). SRC-1 was assigned a hazard ratio of 2.12 using a Cox proportional hazards model. Endocrine-treated patients who coexpressed AIB1 with human epidermal growth factor receptor 2 had a significantly shorter DFS compared with all other patients (P = 0.03). Quantitative coassociation analysis in the patient tissue microarray revealed significantly stronger colocalization of AIB1 and SRC-1 with estrogen receptor α in patients who have relapsed in comparison with those patients who did not recur (P = 0.026 and P = 0.00001, respectively). Conclusions: SRC-1 is a strong independent predictor of reduced DFS, whereas the interactions of the p160 proteins with estrogen receptor α can predict the response of patients to endocrine treatment.

Abstract #3032 The p160 coactivators AIB1 and SRC-1 are known to play a critical role in modulating transcription in breast cancer cells in conjunction with ligand-bound estrogen receptor. The interactions of the p160 proteins with this nuclear receptor are also important in the development of resistance to endocrine treatments. Using quantitative coassociation immunofluorescent microscopy, the colocalisation of the p160s and ERα was increased in the LY2 endocrine resistant cell line following treatment with the anti-estrogen tamoxifen in comparison to the endocrine sensitive MCF-7 cell line. In cell cultures derived from patient tumours at the time of primary surgery prior to treatment, there was an increase in association of the coactivators with ERα following treatment with estrogen but dissociation was evident in the presence of tamoxifen. Immunohistochemical staining of a tissue microarray, constructed from 560 breast cancer patients, revealed that SRC-1 was a strong predictor of reduced disease-free survival, both in patients receiving adjuvant tamoxifen treatment and untreated patients (p Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3032.

Microtubule assembly and disassembly is required for the maintenance of cell structure, mobility, and division. However, the cellular and biochemical implications of microtubule disruption are not fully understood. Using a proteomic approach, we found that the peptidyl-prolyl isomerase, cyclophilin A, was increased in plasma membrane extracts from chronic myeloid leukemia cells after microtubule disruption. In addition, we found that two peptidyl-prolyl isomerases, cyclophilin A and pin1, are overexpressed up to 10-fold in hematological malignancies compared with normal peripheral blood mononuclear cells. Although previous reports suggest that cyclophilin A is localized to the cytosol of mammalian cells, we found that cyclophilin A and pin1 are both localized to the nucleus and nuclear domains in hematopoietic cells. Microtubule disruption of hematopoietic cells caused a dramatic subcellular redistribution of cyclophilin A and pin1 from the nucleus to the cytosol and plasma membrane. We suggest that this accounts for the increased cyclophilin A at the plasma membrane of chronic myeloid leukemia cells after microtubule disruption. The subcellular redistribution of cyclophilin A and pin1 occurred in a c-Jun NH(2)-terminal kinase- and serine protease-dependent manner. Moreover, the altered subcellular localization of the peptidyl-prolyl isomerases occurred in a dose- and time-dependent manner after microtubule disruption and was found to correlate with G(2)/M arrest and precede induced cell death. These results suggest that the function of peptidyl-prolyl isomerases may be influenced by microtubule dynamics throughout the cell cycle, and their altered localization may be an important part of the mechanism by which microtubule-disrupting agents exert their cytostatic effects.