Event In Breast Cancer Progression Research Articles

APPLICATIONS OF TRANSCRIPTOMICS METHODS IN BREAST CANCER

Gene expression studies using cDNA microarrays have revolutionized the breast cancer subclassification. The application of RNA sequencing technologies has revealed additional complexity of breast cancer. The integrated genomic/transcriptomic analysis of breast tumors (METABRIC) and the Cancer Genome Atlas (TCGA) with clinical follow-up data shaped the molecular landscape of breast cancer the last decade. High-throughput RNA sequencing technologies have shown that large proportions of mammalian transcriptome include regulatory non-protein-coding RNAs (ncRNAs) besides protein-coding RNAs. Role of ncRNAs have been well documented in breast cancer. Using RNA sequencing and probe-based transcriptome analyses, several studies, including ours, have emphasized the role alternative splicing events in breast cancer progression. We have demonstrated that Epithelial Splicing Regulatory Protein 1 (ESRP1), a splicing factor, is associated with poor prognosis and endocrine resistance in human ER-positive (ER+) breast tumors. These studies have further implicated that aberrant regulation of alternative splicing plays an important role in all hallmarks of cancer and provide novel strategies for the therapeutics in breast cancer. In addition to bulk sequencing, deconvolution methods such as CIBERSORT was useful to understand the role of individual cells in cancer progression. Using TCGA and METABRIC cohorts, we identified immune-subtypes with better outcomes in triple negative breast cancer (TNBCs). Recently, single cell RNA-seq (sc-RNAseq) and spatial RNA-seq technologies have enabled analysis of single tumor cell phenotypes and intratumor heterogeneity. The application of these technologies to formalin-fixed paraffin-embedded (FFPE) tumor samples with clinical outcomes will present a valuable resource for understanding the inter and intra-tumor heterogeneity in breast cancer.

AKT1 Transcriptomic Landscape in Breast Cancer Cells.

Overexpression and hyperactivation of the serine/threonine protein kinase B (AKT) pathway is one of the most common cellular events in breast cancer progression. However, the nature of AKT1-specific genome-wide transcriptomic alterations in breast cancer cells and breast cancer remains unknown to this point. Here, we delineate the impact of selective AKT1 knock down using gene-specific siRNAs or inhibiting the AKT activity with a pan-AKT inhibitor VIII on the nature of transcriptomic changes in breast cancer cells using the genome-wide RNA-sequencing analysis. We found that changes in the cellular levels of AKT1 lead to changes in the levels of a set of differentially expressed genes and, in turn, imply resulting AKT1 cellular functions. In addition to an expected positive relationship between the status of AKT1 and co-expressed cellular genes, our study unexpectedly discovered an inherent role of AKT1 in inhibiting the expression of a subset of genes in both unstimulated and growth factor stimulated breast cancer cells. We found that depletion of AKT1 leads to upregulation of a subset of genes—many of which are also found to be downregulated in breast tumors with elevated high AKT1 as well as upregulated in breast tumors with no detectable AKT expression. Representative experimental validation studies in two breast cancer cell lines showed a reasonable concurrence between the expression data from the RNA-sequencing and qRT-PCR or data from ex vivo inhibition of AKT1 activity in cancer patient-derived cells. In brief, findings presented here provide a resource for further understanding of AKT1-dependent modulation of gene expression in breast cancer cells and broaden the scope and significance of AKT1 targets and their functions.

Heterotypic clustering of circulating tumor cells and circulating cancer-associated fibroblasts facilitates breast cancer metastasis.

Cancer-associated fibroblasts (CAFs) are recruited to the tumor microenvironment (TME) and are critical drivers of breast cancer (BC) malignancy. Circulating tumor cells (CTCs) travel through hematogenous routes to establish metastases. CTCs circulate both individually and, more rarely, in clusters with other cell types. Clusters of CTCs have higher metastatic potential than single CTCs. Previously, we identified circulating CAFs (cCAFs) in patients with BC and found that while healthy donors had no CTCs or cCAFs, both were present in most Stage IV patients. cCAFs circulate individually, as cCAF-cCAF homotypic clusters, and in heterotypic clusters with CTCs. In this study, we evaluate CTCs, cCAFs, and heterotypic cCAF-CTC clusters in patients with stage I-IV BC. We evaluate the association of heterotypic clusters with BC disease progression and metastasis in a spontaneous mouse model. Using previously established primary BC and CAF cell lines, we examine the metastatic propensity of heterotypic cCAF-CTC clusters in orthotopic and tail vein xenograft mouse models of BC. Using an in vitro clustering assay, we determine factors that may be involved in clustering between CAF and BC cells. We report that the dissemination of CTCs, cCAFs, and clusters is an early event in BC progression, and we find these clusters in all clinical stages of BC. Furthermore, cCAFs-CTC heterotypic clusters have a higher metastatic potential than homotypic CTC clusters in vivo. We also demonstrate that the adhesion and stemness marker CD44, found on a subset of CTCs and CAF cells, is involved in heterotypic clustering of these cells. We identify a novel subset of circulating tumor cell clusters that are enriched with stromal CAF cells in BC patient blood and preclinical mouse models of BC metastasis. Our data suggest that clustering of CTCs with cCAFs augments their metastatic potential and that CD44 might be an important mediator of heterotypic clustering of cCAFs and BC cells.

Prostaglandin E2 Receptor 4 (EP4) as a Therapeutic Target to Impede Breast Cancer-Associated Angiogenesis and Lymphangiogenesis.

Simple SummaryThe formation of new blood (angiogenesis) and lymphatic (lymphangiogenesis) vessels are major events associated with most epithelial malignancies, including breast cancer. Inflammation is a key mediator of both processes, hijacked by many cancers by the aberrant expression of the inflammation-associated enzyme cyclo-oxygenase (COX)-2. In this review, we focus on breast cancer and show that COX-2 is a major promoter of both events, primarily resulting from the activation of prostaglandin (PG) E receptor EP4 on tumor cells, tumor-infiltrating immune cells, and endothelial cells; and induction of oncogenic microRNAs. The COX-2/EP4 pathway also promotes additional events in breast cancer progression, such as cancer cell migration, invasion, and the stimulation of stem-like cells. Based on a combination of studies using multiple breast cancer models, we show that EP4 antagonists hold a major promise in breast cancer therapy in combination with other modalities including immune check-point inhibitors.The formation of new blood (angiogenesis) and lymphatic (lymphangiogenesis) vessels are major events associated with most epithelial malignancies, including breast cancer. Angiogenesis is essential for cancer cell survival. Lymphangiogenesis is critical in maintaining tumoral interstitial fluid balance and importing tumor-facilitatory immune cells. Both vascular routes also serve as conduits for cancer metastasis. Intratumoral hypoxia promotes both events by stimulating multiple angiogenic/lymphangiogenic growth factors. Studies on tumor-associated lymphangiogenesis and its exploitation for therapy have received less attention from the research community than those on angiogenesis. Inflammation is a key mediator of both processes, hijacked by many cancers by the aberrant expression of the inflammation-associated enzyme cyclo-oxygenase (COX)-2. In this review, we focus on breast cancer and showed that COX-2 is a major promoter of both events, primarily resulting from the activation of prostaglandin (PG) E receptor EP4 on tumor cells, tumor-infiltrating immune cells, and endothelial cells; and the induction of oncogenic microRNAs. The COX-2/EP4 pathway also promotes additional events in breast cancer progression, such as cancer cell migration, invasion, and the stimulation of stem-like cells. Based on a combination of studies using multiple breast cancer models, we show that EP4 antagonists hold a major promise in breast cancer therapy in combination with other modalities including immune check-point inhibitors.

Abstract P3-01-29: Impact of heparan sulphate binding domain of chemokine CCL21 to migration of breast cancer cells

Abstract Lymph node metastasis constitutes a key event in breast cancer progression. Chemokines are small proteins, which can promote metastatic spread by inducing cancer cell migration and invasion. Chemokine function is dependant upon their binding to both cell surface heparan sulphate (HS) molecules and to their specific receptor. Our group has demonstrated a significant increase in chemokine receptor CCR7 expression in cancerous breast epithelia compared to healthy controls. This study is designed to test the hypothesis that a non-HS binding forms of chemokine CCL21 can disrupt the normal response to CCL21, therefore reducing the metastasis of CCR7-expressing cancer cells. Truncated CCL21 chemokine (Δ98-134 c-terminal basic extension), was synthesised to investigate a possible linkage between chemokine binding capacity and cell activation. Wild type (WT) and mutant-CCL21 were tested for their ability to stimulate a dose-dependent increase in intracellular-free calcium in peripheral blood mononuclear cell (PBMC) and breast cancer epithelial cells MDA-MB-231. Mutant-CCL21 at concentrations 5 and 10nM showed potential to mobilise Ca2+ at levels similar to that produced by WT-CCl21. A series of experiments was performed to determine how deletion of the HS-binding site altered the ability of CCL21 to stimulate chemotaxis within a concentration gradient generated by free solute diffusion. PBMC stimulated to migrate by wild-type CCL21 was not significantly different from that stimulated by mutant (P> 0.05). Similar results were observed in assays using MDA-MB-231 cells. A further series of experiments was performed to compare the potential of WT and mutant-CCL21 to stimulate the migration of cells across endothelium. In contrast to results for trans-filter migration, it was found that the non HS-binding mutant stimulated no increased in transendothelial cell migration above the background at each of the tested concentrations, 10, 30 and 50 nM respectively (P>0.05). However, WT-CCL21 stimulated significant increased PBMC migration at each of the tested concentration (all P <0.001). Furthermore, the effect of heparin on chemotactic properties of WT and mutant- CCL21 was examined. Interestingly, heparin (250 µg/ml) completely inhibit the chemotaxis mediated by WT-CCL21 (5nM) (P < 0.001), whereas it did not inhibit the chemotaxis at concentrations 100, 250 & 500 µg/ml in response to mutant CCL21 (5nM) (P > 0.05). Similar assay will be performed using MDA-MB-231 cells. Work is ongoing to characterise the biophysical properties of mutant-CCL21 and determine its potential role for a therapeutic blockade of the migration of breast cancer cells in-vivo. Our primarily data showed that mutant CCL21 in xenograft brain tumor models showed substantial inhibition of tumour growth. Our results indicate that truncated CCL21 chemokine might be a potential preventive biofactor for human breast cancer metastasis by targeting chemokine receptor genes. Citation Format: Mohammed Imad Malki. Impact of heparan sulphate binding domain of chemokine CCL21 to migration of breast cancer cells [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-29.

Ductal Carcinoma In Situ Progression in Dog Model of Breast Cancer.

The mechanisms that drive ductal carcinoma in situ (DCIS) progression to invasive cancer are not clear. Studying DCIS progression in humans is challenging and not ethical, thus necessitating the characterization of an animal model that faithfully resembles human disease. We have characterized a canine model of spontaneous mammary DCIS and invasive cancer that shares histologic, molecular, and diagnostic imaging characteristics with DCIS and invasive cancer in women. The purpose of the study was to identify markers and altered signaling pathways that lead to invasive cancer and shed light on early molecular events in breast cancer progression and development. Transcriptomic studies along the continuum of cancer progression in the mammary gland from healthy, through atypical ductal hyperplasia (ADH), DCIS, and invasive carcinoma were performed using the canine model. Gene expression profiles of preinvasive DCIS lesions closely resemble those of invasive carcinoma. However, certain genes, such as SFRP2, FZD2, STK31, and LALBA, were over-expressed in DCIS compared to invasive cancer. The over-representation of myoepithelial markers, epithelial-mesenchymal transition (EMT), canonical Wnt signaling components, and other pathways induced by Wnt family members distinguishes DCIS from invasive. The information gained may help in stratifying DCIS as well as identify actionable targets for primary and tertiary prevention or targeted therapy.

Inhibition of EZH2 Catalytic Activity Selectively Targets a Metastatic Subpopulation in Triple-Negative Breast Cancer

Epigenetic changes are increasingly being appreciated as key events in breast cancer progression. However, breast cancer subtype-specific epigenetic regulation remains poorly investigated. Here we report that EZH2 is a leading candidate of epigenetic modulators associated with the TNBC subtype and that it predicts poor overall survival in TNBC patients. We demonstrate that specific pharmacological or genetic inhibition of EZH2 catalytic activity impairs distant metastasis. We further define a specific EZH2high population with enhanced invasion, mammosphere formation, and metastatic potential that exhibits marked sensitivity to EZH2 inhibition. Mechanistically, EZH2 inhibition differentiates EZH2high basal cells to a luminal-like phenotype by derepressing GATA3 and renders them sensitive to endocrine therapy. Furthermore, dissection of human TNBC heterogeneity shows that EZH2high basal-like 1 and mesenchymal subtypes have exquisite sensitivity to EZH2 inhibition compared with the EZH2low luminal androgen receptor subtype. These preclinical findings provide a rationale for clinical development of EZH2 as a targeted therapy against TNBC metastasis.

Role for the transcriptional activator ZRF1 in early metastatic events in breast cancer progression and endocrine resistance.

Breast cancer is one of the most common malignancies among women which is often treated with hormone therapy and chemotherapy. Despite the improvements in detection and treatment of breast cancer, the vast majority of breast cancer patients are diagnosed with metastatic disease either at the beginning of the disease or later during treatment. Still, the molecular mechanisms causing a therapy resistant metastatic breast cancer are still elusive. In the present study we addressed the function of the transcriptional activator ZRF1 during breast cancer progression. We provide evidence that ZRF1 plays an essential role for the early metastatic events in vitro and acts like a tumor suppressor protein during the progression of breast invasive ductal carcinoma into a more advanced stage. Hence, depletion of ZRF1 results in the acquisition of metastatic behavior by facilitating the initiation of the metastatic cascade, notably for cell adhesion, migration and invasion. Furthermore absence of ZRF1 provokes endocrine resistance via misregulation of cell death and cell survival related pathways. Taken together, we have identified ZRF1 as an important regulator of breast cancer progression that holds the potential to be explored for new treatment strategies in the future.

Abstract P1-01-16: Detection of disseminated tumor cells in DCIS patients impacts local recurrence

Abstract Background Recently it was shown that tumor cell dissemination is an early event in breast cancer progression (Hosseini et al., Nature 2016). This has been backed up by an assessment of over 100,000 patients with in situ carcinoma (DCIS), where some patients developed distant metastases and died from breast cancer without presenting with local invasive recurrence (Narod et al., JAMA Oncology 2015). We therefore analyzed the presence and clinical impact of disseminated tumor cells (DTC) in the bone marrow (BM) of DCIS patients. Methods BM aspirates were collected from patients undergoing surgery for primary DCIS at Tuebingen University Hospital between 2001 and 2016. Exclusion criteria were presence of invasive breast cancer, bilateral or metastatic disease as well as other malignancies in their history. DTC were identified by immunocytochemistry using the A45-B/B3 anti-pancytokeratin antibody. Results 627 patients were included. Median follow-up was 49 months. 72 (11%) had detectable DTC. The detection of DTC was not significantly associated with lymph node positivity (3/479, Fisher's exact test: p=0.307) or tumor size (median 30mm, Wilcoxon test: p=0.952). In 33 (5%) women, a disease recurrence was observed. Of 31 local recurrences 19 were invasive. 7 Patients developed distant metastases, four without an invasive recurrence beforehand. 14 patients died during follow-up. The detection of at least 2 DTC per 1.5x106 mononuclear BM cells was significantly associated with a lower local recurrence free survival (log-rank: p=0.023) whereas there was no significant difference in distant disease free survival (p=0.315) and overall survival (p=0.083). Discussion For the first time, we were able to show that DTC-detection in DCIS patients is associated with local recurrence. The number of distant metastases in women without invasive local recurrence detected in this cohort was comparable to earlier findings at different centers. This study warrants further investigations concerning evolutionary relationship between primary tumor, minimal residual disease, local recurrence and clinically detectable macrometastases. Citation Format: Walter VP, Taran F-A, Wallwiener M, Brucker SY, Hartkopf AD. Detection of disseminated tumor cells in DCIS patients impacts local recurrence [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-16.

Posttranslationally modified progesterone receptors direct ligand-specific expression of breast cancer stem cell-associated gene programs

BackgroundEstrogen and progesterone are potent breast mitogens. In addition to steroid hormones, multiple signaling pathways input to estrogen receptor (ER) and progesterone receptor (PR) actions via posttranslational events. Protein kinases commonly activated in breast cancers phosphorylate steroid hormone receptors (SRs) and profoundly impact their activities.MethodsTo better understand the role of modified PRs in breast cancer, we measured total and phospho-Ser294 PRs in 209 human breast tumors represented on 2754 individual tissue spots within a tissue microarray and assayed the regulation of this site in human tumor explants cultured ex vivo. To complement this analysis, we assayed PR target gene regulation in T47D luminal breast cancer models following treatment with progestin (promegestone; R5020) and antiprogestins (mifepristone, onapristone, or aglepristone) in conditions under which the receptor is regulated by Lys388 SUMOylation (K388 intact) or is SUMO-deficient (via K388R mutation to mimic persistent Ser294 phosphorylation). Selected phospho-PR-driven target genes were validated by qRT-PCR and following RUNX2 shRNA knockdown in breast cancer cell lines. Primary and secondary mammosphere assays were performed to implicate phospho-Ser294 PRs, epidermal growth factor signaling, and RUNX2 in breast cancer stem cell biology.ResultsPhospho-Ser294 PR species were abundant in a majority (54%) of luminal breast tumors, and PR promoter selectivity was exquisitely sensitive to posttranslational modifications. Phospho-PR expression and target gene programs were significantly associated with invasive lobular carcinoma (ILC). Consistent with our finding that activated phospho-PRs undergo rapid ligand-dependent turnover, unique phospho-PR gene signatures were most prevalent in breast tumors clinically designated as PR-low to PR-null (luminal B) and included gene sets associated with cancer stem cell biology (HER2, PAX2, AHR, AR, RUNX). Validation studies demonstrated a requirement for RUNX2 in the regulation of selected phospho-PR target genes (SLC37A2). In vitro mammosphere formation assays support a role for phospho-Ser294-PRs via growth factor (EGF) signaling as well as RUNX2 as potent drivers of breast cancer stem cell fate.ConclusionsWe conclude that PR Ser294 phosphorylation is a common event in breast cancer progression that is required to maintain breast cancer stem cell fate, in part via cooperation with growth factor-initiated signaling pathways and key phospho-PR target genes including SLC37A2 and RUNX2. Clinical measurement of phosphorylated PRs should be considered a useful marker of breast tumor stem cell potential. Alternatively, unique phospho-PR target gene sets may provide useful tools with which to identify patients likely to respond to selective PR modulators that block PR Ser294 phosphorylation as part of rational combination (i.e., with antiestrogens) endocrine therapies designed to durably block breast cancer recurrence.

Abstract PR06: Modeling the tumor microenvironment to identify novel loss of function mutations in breast cancer progression

Abstract Recent next generation sequencing studies have comprehensively mapped the genetic landscape of breast cancer and revealed that only a small number of genes are recurrently mutated in more than 10% of unselected tumors (i.e. TP53, PIK3CA and GATA3), and that the vast majority of recurrent mutations occur at low frequencies. Although some have been shown to be drivers (i.e. confer a selective advantage), such as oncogenic ERBB2 mutations, there is a myriad of significantly altered lower frequency mutations whose functional impact is unknown. We utilized a functional genomics approach silencing the 200 most frequently mutated genes in breast cancer in 3D spheroid cultures that more accurately recapitulate in vivo like conditions, using the MCF10A progression series cell line panel to identify novel loss of function mutations that affect breast cancer progression from non-malignant to highly invasive disease. Genes whose silencing significantly altered spheroid growth were integrated with comprehensive copy number and mutation data in order to analyze the impact of these genes in concert with additional driver alterations in genes such as TP53 and PIK3CA mutations. We identified 11 genes whose silencing with siRNA had a significant effect on growth in two or more cell lines in 3D, including FMN2, FOXA1, NIPBL and CREBBP. Silencing of FMN2 increased spheroid growth in the invasive cell lines only, suggesting loss of function mutations are a later event in breast cancer progression. A second targeted validation screen showed that silencing of a cohort of these genes had limited effect under traditional 2D culture conditions, for example, silencing of maltase-glucoamylase (MGAM) resulted in increased growth in AT1 and DCIS.com cells in 3D while having no effect in 2D; an effect that was recapitulated by treating cells with an established MGAM inhibitor. Furthermore, loss of NIPBL significantly increased spheroid growth in cells harboring TP53 nuclear accumulation, and was significantly co-mutated in TP53 mutant primary tumors, suggestive of epistasis. Integrating genes that when silenced decreased spheroid growth with mutation status in the cell lines identified 3D specific oncogenic dependencies with PIK3CA and novel SZT2 mutations. Using a functional genomic approach in 3D models we have identified recurrently mutated genes whose loss or gain of function contribute to breast cancer progression and furthermore may be epistatic or cooperate with established driver mutations in breast cancer. Citation Format: Barrie Peck, Sarah Maguire, Eamonn Morrison, Patty Wai, Rachael Natrajan. Modeling the tumor microenvironment to identify novel loss of function mutations in breast cancer progression. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr PR06.

Abstract 4805: Whole genome sequencing of primary breast cancers and matched distant metastases

Abstract Metastatic disease is the main cause of death for breast cancer patients, but it is still unclear whether primary tumor characteristics are predictive of the metastasis phenotype. Our aim was to investigate, by analyzing chromosomal structural variation, the clonal similarities between primary breast tumors and their matched distant metastases. For 11 patients, we performed low-coverage (∼10x) whole-genome sequencing on 11 primary breast tumors and 13 matched distant metastases to enumerate chromosomal rearrangements. The tumor genomes (n = 24) harbored a median of 85 (range 18-405) chromosomal rearrangements per tumor, with a median of 82 (26-310) in primaries compared to 87 (18-405) in distant metastases. Similarity between tumors was assessed based on presence or absence of chromosomal rearrangements. Concordance between matched primaries and distant metastases from the same patient was high, with a median of 89% rearrangements being shared (range 61-100%). Nearly all of the rearrangements were patient-specific, with very little overlap when comparing all possible pairings of tumors from different patients (median 3%). The tumors exhibited different genomic patterns of rearrangements: some carried events scattered throughout the genome while other tumors had events in densely clustered foci - chromothripsis-like hotspots - at a few chromosomal locations. Irrespective of the type of rearrangement profile of the tumor genomes, the patterns were highly conserved between the primary tumor and metastasis from the same patient, although in general metastases acquired additional rearrangement events. Our study suggests that analysis of structural variation in tumor genomes could be useful for identifying tumor origin, facilitating cancer detection via measurement of rearrangements in circulating tumor DNA, and estimating degree of relatedness between primary tumors and metastases. Moreover, our finding that distant metastases have a close clonal relationship to the primary tumor at the level of chromosomal structure is most consistent with chromosomal rearrangements being early events in breast cancer progression that remain stable during the development from a primary tumor to its distant metastasis. Citation Format: Man-Hung Tang, Malin Dahlgren, Christian Brueffer, Christof Winter, Yilun Chen, Eleonor Olsson, Martin Sjöström, Pär-Ola Bendahl, Emma Niméus-Malmström, Lao H. Saal, Åke Borg, Sofia K. Gruvberger-Saal. Whole genome sequencing of primary breast cancers and matched distant metastases. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4805. doi:10.1158/1538-7445.AM2015-4805

Abstract PD6-6: Estrogen receptor (ESR1) mutations confer resistance to hormone therapy using a common mechanism

Abstract Background: The idea that somatic estrogen receptor gene (ESR1) mutations could play an important role in the evolution of hormone-responsive breast cancers was proposed by us with our original identification of two ESR1 mutations at residues K303 and Y537. Technical issues with ESR1 mutation detection and the resulting paucity of reports in tumors led many to assume that ESR1 mutations were not there. However, with recent Next Generation Sequencing of metastatic tumors, mutation of ESR1 is now an accepted certainty. ESR1 mutant allele frequencies vary over a wide dynamic range, and are usually a minority population within tumors. Therefore how does a minor subclonal tumor population drive resistance in metastatic tumors? Methods: MCF-7 cells expressing endogeous wild-type ER was transduced with ESR1 mutants K303R, Y537N, Y537S, and D538G lentivirus and stable clones selected. ER transcriptional assays and growth in soft agar were performed. Digital drop (dd) PCR and primer extension snp detection were used to ascertain mutant:WT ESR1 allele frequency in cell lines, 200 primary tumors from patients treated with tamoxifen monotherapy, and 20 metastatic breast tumors. Results: Mutant ER constitutive transcriptional activity was fully antagonized by the antiestrogens tamoxifen or fulvestrant in MCF-7 stable transfectants. In contrast, soft agar growth of all ESR1 mutant-expressing cells was unexpectedly and completely resistant to the growth inhibitory effects of tamoxifen, although mutant-expressing cells were a minority subpopulation in the stable clones. Therefore, in cells with WT ER co-expression, the mutant resistant phenotype dominates. We found that phosphorylation of IGF1Rß; was constitutively increased in all ESR1-mutant expressing cells. Treatment with a specific IGF1Rß inhibitor in combination with tamoxifen drastically restored hormone sensitivity in cells expressing the ESR1 mutations. These results suggest a convergence in resistance mechanisms between the K303R and Y537 ESR1 mutation hot spots. We are exploring whether the dominant mutant ESR1 resistant phenotype occurs via activation of paracrine mediators, and have identified altered IGF-1 and interleukin 6 signaling in mutant-expressing cells. Mutation detection in a retrospective cohort of primary and metastatic breast tumors is ongoing and will be presented. Conclusions: We hypothesize that the selection of dominant-acting ESR1 mutations in tumors is a key event in breast cancer progression, potentially due to the selective pressure of antiestrogens. The dominant-resistant phenotype of ESR1 mutants in a majority WT background supports the subclonal evolution of ESR1 mutations in breast cancer recurrence. A common resistance mechanism (like consitutive IGF1Rß activation) should enable biologic targeting of ESR1 mutation-positive metastatic patients a feasible clinical goal. Support: NIH/NCI R01 CA72038 and CPRIT RP1210732 to SAWF. Citation Format: Luca Gelsomino, Guowei Gu, Yassine Rechoum, Sebastiano Ando', Suzanne AW Fuqua. Estrogen receptor (ESR1) mutations confer resistance to hormone therapy using a common mechanism [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 PD6-6.

Correction: S137 Phosphorylation of Profilin 1 Is an Important Signaling Event in Breast Cancer Progression

Correction: S137 Phosphorylation of Profilin 1 Is an Important Signaling Event in Breast Cancer Progression

Abstract LB-67: Breast cancer-associated lymphangiogenesis: roles of PGE2 and EP4 receptor on lymphatic endothelial cells

Abstract Background: Lymphatic metastasis is a common event in breast cancer, facilitated by tumor-associated lymphangiogenesis, molecular mechanisms of which remain poorly defined. We had earlier shown that endogenous PGE2 resulting from elevated COX-2 expression by breast cancer cells promotes tumor progression and metastasis by multiple mechanisms: inactivation of host immune cells, stimulation of tumor cell migration, tumor-associated angiogenesis and lymphangiogenesis. The latter was due to upregulation of VEGF-C or -D secretion due to activation of EP4 receptors on breast cancer cells and cancer-infiltrating macrophages. Objectives: To examine whether PGE2 in the tumor micro-environment directly promotes lymphangiogenesis by stimulating EP4 receptors on lymphatic endothelial cells (LEC).Approaches: In vitro studies utilized a rat mesenteric lymphatic endothelial cell line (RMLEC) and a COX-2 expressing, VEGF-C/-D producing murine breast cancer cell line C3L5; in vivo studies measured lymphangiogenesis in nude mice. Results RMLEC expressed all EP receptors and responded to PGE2, an EP4 agonist (EP4a) PGE1-OH, or C3L5 cell conditioned media (C3L5-CM) by increased proliferation, migration and accelerated tube formation on growth factor-reduced matrigel. Tube formation on matrigel alone was completely abrogated in the presence of COX 1/2 inhibitor indomethacin (10uM), COX-2 inhibitor (COX-2i) NS-398 (15uM), and a selective EP4 antagonist (EP4A) RQ15986 (2.5 nM), indicating the roles of COX-2 and EP4. Addition of PGE2, EP4a, or C3L5-CM individually in presence of the COX-2i, or EP4A, partially restored the tube formation, reinforcing the role of EP4 on RMLEC. RMLEC grown in the presence of PGE2 showed upregulation of COX2, EP4, VEGF-C and VEGF-D mRNAs. Knocking down EP4 with shRNA in RMLEC abrogated tube formation on matrigel in the absence or presence of PGE-2, EP4a, or C3L5-CM. EP4 silenced RMLEC also became unresponsive to these agents in stimulating PGE2, VEGF-C, and -D production. Finally in a directed in vivo lymphangiogenesis assay (DIVLA) using implants of angioreactors including PGE-2, EP4a or VEGF-C in the dorsal flanks of nude mice, we simultaneously measured lymphangiogenesis and angiogenesis using dual immunostaining of the tissue contents for Lyve-1 and cd31, or prox-1 and cd31. Results demonstrated the lymphangiogenic as well as angiogenic capacity of PGE2 and EP4a in vivo by recruitment of new vessels. Conclusions: Tumor or host-derived PGE2 stimulates lymphangiogenesis, at least in part, by activating EP4 on the LEC. Combined with earlier studies we show that EP4 is a common therapeutic target on tumor and host cells (macrophages and LEC) in abrogating multiple events in breast cancer progression. This may spare cardio-protective prostanoids like PGI2, inhibited by COX-2 inhibitors Citation Format: Peeyush K. Lala, Gannareddy V. Girish, Xiping Xin, Mousumi Majumder, Elena Tutunea-Fatan, Pinki Nandi. Breast cancer-associated lymphangiogenesis: roles of PGE2 and EP4 receptor on lymphatic endothelial cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-67. doi:10.1158/1538-7445.AM2014-LB-67

Differential subcellular and extracellular localisations of proteins required for insulin-like growth factor- and extracellular matrix-induced signalling events in breast cancer progression.

BackgroundCancer metastasis is the main contributor to breast cancer fatalities as women with the metastatic disease have poorer survival outcomes than women with localised breast cancers. There is an urgent need to develop appropriate prognostic methods to stratify patients based on the propensities of their cancers to metastasise. The insulin-like growth factor (IGF)-I: IGF binding protein (IGFBP):vitronectin complexes have been shown to stimulate changes in gene expression favouring increased breast cancer cell survival and a migratory phenotype. We therefore investigated the prognostic potential of these IGF- and extracellular matrix (ECM) interaction-induced proteins in the early identification of breast cancers with a propensity to metastasise using patient-derived tissue microarrays.MethodsSemiquantitative immunohistochemistry analyses were performed to compare the extracellular and subcellular distribution of IGF- and ECM-induced signalling proteins among matched normal, primary cancer and metastatic cancer formalin-fixed paraffin-embedded breast tissue samples.ResultsThe IGF- and ECM-induced signalling proteins were differentially expressed between subcellular and extracellular localisations. Vitronectin and IGFBP-5 immunoreactivity was lower while β1 integrin immunoreactivity was higher in the stroma surrounding metastatic cancer tissues, as compared to normal breast and primary cancer stromal tissues. Similarly, immunoreactive stratifin was found to be increased in the stroma of primary as well as metastatic breast tissues. Immunoreactive fibronectin and β1 integrin was found to be highly expressed at the leading edge of tumours. Based on the immunoreactivity it was apparent that the cell signalling proteins AKT1 and ERK1/2 shuffled from the nucleus to the cytoplasm with tumour progression.ConclusionThis is the first in-depth, compartmentalised analysis of the distribution of IGF- and ECM-induced signalling proteins in metastatic breast cancers. This study has provided insights into the changing pattern of cellular localisation and expression of IGF- and ECM-induced signalling proteins in different stages of breast cancer. The differential distribution of these biomarkers could provide important prognostic and predictive indicators that may assist the clinical management of breast disease, namely in the early identification of cancers with a propensity to metastasise, and/or recur following adjuvant therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-627) contains supplementary material, which is available to authorized users.

S137 Phosphorylation of Profilin 1 Is an Important Signaling Event in Breast Cancer Progression

BackgroundProfilins are actin-modulating proteins regulating many intracellular functions based on their multiple and diverse ligand interactions. They have been implicated to play a role in many pathological conditions such as allergies, cardiovascular diseases, muscular atrophy, diabetes, dementia and cancer. Post-translational modifications of profilin 1 can alter its properties and subsequently its function in a cell. In the present study, we identify the importance of phosphorylation of profilin 1 at serine 137 (S137) residue in breast cancer progression.Methods/Principal FindingsWe found elevated profilin 1 (PFN) in human breast cancer tissues when compared to adjacent normal tissues. Overexpression of wild-type profilin 1 (PFN-WT) in breast cancer MCF7 cells made them more migratory, invasive and adherent independent in comparison to empty vector transfected cells. Mutation in serine phosphorylation site (S137) of profilin 1 (PFN-S137A) significantly abrogated these properties. Mutation affecting actin-binding ability (PFN-R74E) of profilin 1 enhanced its tumorigenic function whereas mutation affecting its poly-L-proline binding function (PFN-H133S) alleviated these mechanisms in breast cancer cells. PFN-WT was found to activate matrix metalloproteinases by zymography, MMP2 and MMP9 in presence of PDBu (phorbol 12, 13 dibutyrate, PI3K agonist) to enhance migration and invasion in MCF7 cells while PFN-S137A did not. Phosphorylation increased migration and invasion in other mutants of profilin 1. Nuclear profilin levels also increased in the presence of PDBu.ConclusionsPrevious studies show that profilin could be executing a dual role in cancer by either suppressing or promoting tumorigenesis in a context dependent manner. In this study we demonstrate for the first time that phosphorylation of profilin 1 at serine 137 enhances oncogenic properties in breast cancer cells. Inhibitors targeting profilin 1 phosphorylation directly or indirectly through inhibition of kinases that phosphorylate profilin could be valuable therapeutic agents that can alter its activity and thereby control the progression of cancer.

Lack of G protein-coupled estrogen receptor (GPER) in the plasma membrane is associated with excellent long-term prognosis in breast cancer

G protein-coupled estrogen receptor (GPER), or GPR30, is a membrane receptor reported to mediate non-genomic estrogen responses. Tamoxifen is a partial agonist at GPER in vitro. Here, we investigated if GPER expression is prognostic in primary breast cancer, if the receptor is treatment-predictive for adjuvant tamoxifen, and if receptor subcellular localization has any impact on the prognostic value. Total and plasma membrane (PM) GPER expression was analyzed by immunohistochemistry in breast tumors from 742 postmenopausal lymph node-negative patients subsequently randomized for tamoxifen treatment for 2-5 years versus no systemic treatment, regardless of estrogen receptor (ER) status, and with a median follow-up of 17 years for patients free of event. PM GPER expression was a strong independent prognostic factor for poor prognosis in breast cancer without treatment-predictive information for tamoxifen. In the tamoxifen-treated ER-positive and progesterone receptor (PgR)-positive patient subgroup, the absence of PM GPER (53 % of all ER-positive tumors) predicted 91 % 20-year distant disease-free survival, compared to 73 % in the presence of GPER (p = 0.001). Total GPER expression showed positive correlations with ER and PgR and negative correlation with histological grade, but the correlations were biphasic. On the other hand, PM GPER expression showed strong negative correlations with ER and PgR, and strong positive correlation with HER2 overexpression and high histological grade. GPER overexpression and PM localization are critical events in breast cancer progression, and lack of GPER in the PM is associated with excellent long-term prognosis in ER-positive and PgR-positive tamoxifen-treated primary breast cancer.

Abstract A126: Change in status promoter of 5 panel gene during progression of atypical hyperplasia to breast cancer.

Abstract Background: DNA methylation is the main epigenetic modification in cancer. The pathological features of breast cancer follow a sequential progression from transition of a normal cell to benign proliferative hyperplasia, hyperplasia with atypia, in situ carcinoma and, eventually, to invasive and metastatic disease. Purpose: This study was designed to evaluate the changes in promoter CpG islands hypermethylation during breast cancer progression from pre-invasive lesions to invasive ductal carcinoma and different methylation patron with benign breast disease. Material and Methods: We performed analysis for the methylation status of 5 promoter CpG island (ESR1, E-Cad, APC, RARB, and 14-3-3-; promoters) in a group with women with normal breast tissue n=74; other group with epithelial atypia/ atypical ductal hyperplasia (n=20), ductal carcinoma in situ (DCIS, n=14) and invasive ductal carcinoma (IDC, n=107). Results: Relative serum levels of methylated gene promoters ESR1 and 14-3-3-; showed significant differences between IDC y normal breast tissue (were significantly higher in IDC than normal breast tissue) and between normal breast tissue and epithelial atypia/ atypical ductal hyperplasia/ ductal carcinoma in situ. There are no differences between IDC and epithelial atypia/ atypical ductal hyperplasia/ ductal carcinoma in situ when 14-3-3-; and ESR1 mean values are compared. In fact, the present findings showed a frequent presence of methylated 14-3-3-; in sera from women with breast benign disease, which could be considered the result of a proliferative alteration of epithelial and stromal components of the breast. Which may indicate presence of occult benign breast disease, although other possible sources of this DNA include normal tissues, which show higher methylation values with increasing age; which might undergo lysis during tumor growth; or premalignant lesion during tumor growth; or premalignant lesion. Conclusions: These findings showed that promoter CpG island methylation changed significantly in pre-invasive lesions, and breast cancer, suggesting that CpG island methylation of tumor-related genes is an early event in breast cancer progression. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A126. Citation Format: Martínez-Galán Joaquina, Juan Ramon Delgado, Blanca Torres-Torres, Rosario Del Moral, Sandra Ríos, M. Isabel Núñez. Change in status promoter of 5 panel gene during progression of atypical hyperplasia to breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A126.

Inhibition of Established Micrometastases by Targeted Drug Delivery via Cell Surface–Associated GRP78

The major cause of morbidity in breast cancer is development of metastatic disease, for which few effective therapies exist. Because tumor cell dissemination is often an early event in breast cancer progression and can occur before diagnosis, new therapies need to focus on targeting established metastatic disease in secondary organs. We report an effective therapy based on targeting cell surface-localized glucose-regulated protein 78 (GRP78). GRP78 is expressed normally in the endoplasmic reticulum, but many tumors and disseminated tumor cells are subjected to environmental stresses and exhibit elevated levels of GRP78, some of which are localized at the plasma membrane. Here, we show that matched primary tumors and metastases from patients who died from advanced breast cancer also express high levels of GRP78. We used a peptidomimetic targeting strategy that uses a known GRP78-binding peptide fused to a proapoptotic moiety [designated bone metastasis targeting peptide 78 (BMTP78)] and show that it can selectively kill breast cancer cells that express surface-localized GRP78. Furthermore, in preclinical metastasis models, we show that administration of BMTP78 can inhibit primary tumor growth as well as prolong overall survival by reducing the extent of outgrowth of established lung and bone micrometastases. The data presented here provide strong evidence that it is possible to induce cell death in established micrometastases by peptide-mediated targeting of cell surface-localized GRP in advanced breast cancers. The significance to patients with advanced breast cancer of a therapy that can reduce established metastatic disease should not be underestimated.