Prevention Of Breast Cancer Metastasis Research Articles

EHMT2 is a metastasis regulator in breast cancer

Various modes of epigenetic regulation of breast cancer proliferation and metastasis have been investigated, but epigenetic mechanisms involved in breast cancer metastasis remain elusive. Thus, in this study, EHMT2 (a histone methyltransferase) was determined to be significantly overexpressed in breast cancer tissues and in Oncomine data. In addition, knockdown of EHMT2 reduced cell migration/invasion and regulated the expression of EMT-related markers (E-cadherin, Claudin 1, and Vimentin). Furthermore, treatment with BIX-01294, a specific inhibitor of EHMT2, affected migration/invasion in MDA-MB-231 cells. Therefore, our findings demonstrate functions of EHMT2 in breast cancer metastasis and suggest that targeting EHMT2 may be an effective therapeutic strategy for preventing breast cancer metastasis.

Quantification of STAT3 and VEGF expression for molecular diagnosis of lymph node metastasis in breast cancer

Background:Axillary lymph node metastasis is associated with increased risk of regional recurrence, distant metastasis, and poor survival in breast malignant neoplasm. Expression of signal transducer and activator of transcription 3 (STAT3) is significantly associated with tumor formation, migration, and invasion in various cancers. In addition, vascular endothelial growth factor (VEGF) expression could promote angiogenesis and increase the risk of tumorigenesis. To determine correlations among STAT3 expression, VEGF, and clinicopathological data on lymph node involvement in breast cancer patients after surgery.Methods:The mRNA expression levels of STAT3 and VEGFs were measured in 45 breast invasive ductal carcinoma tissues, 45 peritumoral tissues, and 45 adjacent nontumor tissues by real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Postoperative pathological examination revealed explicit axillary lymph node involvement in all patients.Results:Average mRNA levels of STAT3 and VEGFs were the highest in breast invasive ductal carcinoma tissues, followed by peritumoral tissues. High expression of STAT3 showed significant positive correlation with high axillary lymph node involvement and progesterone receptor (PR), VEGF-C, VEGF-D, and vascular endothelial growth factor receptor (VEGFR)-3 expression. The expression levels of STAT3, VEGF-C, and VEGFR-3 were significantly higher in the tumor tissues of patients with axillary lymph node metastasis than in those of patients without the metastasis. Expression levels of VEGF-C and VEGFR-3 were also significantly higher in peritumoral tissues of patients with axillary lymph node metastasis. Positive correlations were found between STAT3 and VEGF-C/-D mRNA levels.Conclusion:These data suggest that STAT3/VEGF-C/VEGFR-3 signaling pathway plays an important role in carcinogenesis and lymph-angiogenesis. Our findings suggest that STAT3 may be a potential molecular biomarker for predicting the involvement of axillary lymph nodes in breast cancer, and therapies targeting STAT3 may be important for preventing breast cancer metastasis.

ROCK inhibition with Fasudil induces beta-catenin nuclear translocation and inhibits cell migration of MDA-MB 231 human breast cancer cells

Tumor aggressiveness is usually associated with metastasis. MDA-MB 231, a triple-negative breast cancer (TNBC), is an aggressive type of breast cancer and associated with early metastasis. The Rho/ROCK pathway is a key regulator of cell motility involving cytoskeleton regulation through stabilization of actin filaments and stress fiber formation. In this study we show that Fasudil, a ROCK inhibitor, inhibited the migration of MDA-MB 231 and A549 cells, without altering the viability of these cells at the concentration of 10 μM, modified tumor cell morphology, with disorganization of stress fibers and promotes activation of the canonical-Wnt/beta-catenin pathway. Therefore, Fasudil present a promising approach to the prevention of breast cancer metastasis through a different mechanism of action from the well-known one.

Protective role of LRRC3B in preventing breast cancer metastasis and recurrence post-bupivacaine.

The present study aimed to investigate the potential effect of leucine-rich repeat containing 3B (LRRC3B) with respect to the inhibition of breast cancer recurrence and metastasis post-anesthesia. The mRNA expression of LRRC3B in breast MDA-MB-231 and MCF-7 cell lines was detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. The effect of bupivacaine on breast cancer cell invasion was analyzed using a Matrigel assay. LRRC3B specific small interfering (si)RNA was constructed and transfected into breast cancer cells using Lipofectamine® 2000 reagent. The influence of bupivacaine on LRRC3B expression was measured based on RT-qPCR. Additionally, the effect of LRRC3B silencing on the invasion of breast cancer cells treated with bupivacaine was analyzed. Compared with the control, LRRC3B expression significantly increased in MDA-MB-231 and in MCF-7 cells as the length of time increased (P<0.05), but the expression of the gene significantly declined in 2 types of cancer cell when the cells were transfected with siRNA-LRRC3B plasma (P<0.05). The administration of 50 µg/ml bupivacaine promoted maximum breast cancer cell invasion, and suppressed LRRC3B mRNA expression in cells. However, when LRRC3B was silenced in cancer cells, 20 µg/ml bupivacaine significantly promoted cancer cell invasion, indicating that bupivacaine suppresses the expression of LRRC3B and promotes cell invasion. The present study suggested that LRRC3B serves a protective role in preventing bupivacaine-induced breast cancer recurrence and metastasis.

Secretion modification region-derived peptide blocks exosome release and mediates cell cycle arrest in breast cancer cells.

PurposeDiscovery and development of a novel anticancer PEG-SMR-Clu peptide to prevent breast cancer metastasis. How breast cancer cells and primary mammary epithelial cells interact and communicate with each other to promote tumorigenesis and how to prevent tumor metastasis has long been a concern of researchers. Cancer cells secrete exosomes containing proteins and RNA. These factors can influence tumor development by directly targeting cancer cells and tumor stroma. In this study, we determined the effects of a peptide as an inhibitor of exosome secretion on breast tumors. We developed a peptide derived from the Secretion Modification Region (SMR) of HIV-1 Nef protein that was modified with PEG on the N-terminus and with a Clusterin (Clu)-binding peptide on the C-terminus. Attachment of PEG to the SMR peptide, termed PEGylation, offers improved water solubility and stability as well as reduced clearance through the kidneys, leading to a longer circulation time. The 12-mer Clu-binding peptide plays multiple roles in tumor development and metastasis. The Clu peptide can be detected by antibody in vivo, thus it has the potential to be used to monitor tumor status and treatment efficacy in animal studies and eventually in cancer patients.ResultsPEG-SMRwt-Clu and PEG-SMRwt peptides inhibited the growth of both of MCF-7 (estrogen responsive, ER+) and MDA-MD-231 (estrogen non-responsive, ER-) human breast cancer cells in a dose and time-dependent manner, without inducing cytotoxic effects. The SMRwt peptide, combined with paclitaxel, induced G2/M phase cell cycle arrest on MCF-7 and MDA-MB-231 cells but did not promote apoptosis. PEG-SMRwt-Clu peptide treatment blocked exosome release from both MCF-7 and MDA-MB-231 cells. This effect was blocked by knockdown of the chaperone protein mortalin by either antibody or siRNA.Materials and methodsMCF-7 and MDA-MB-231 breast tumor cells were treated with PEG-SMR-Clu peptide alone and in combination with paclitaxel and cisplatin. Cell proliferation and viabilty were determined via cell cycle analysis using Cellometer imaging cytometry, Annexin V and MTT assays. The effects of the PEG-SMR-Clu peptide on tumor exosome release were determined by testing isolated exosome fractions, for (i) expression of CD63 and Alix proteins by Western blotting, (ii) NanoSight nanoparticle tracking analysis (NTA 10) to measure exosomes size and concentration, and (iii) measurement of acetylcholinesterase (AchE) for exosome specific enzyme activity.ConclusionsPEG-SMRwt-CLU peptides inhibited the growth of human breast cancer cells and blocked tumor exosome release in vitro. The peptide alone did not cause increased cytotoxicity or apoptosis induction, but did cause cell cycle G2/M phase arrest in both estrogen responsive and non-responsive breast cancer cells. These data suggest a potential therapeutic value of SMR to prevent breast cancer metastasis and as an adjuvant for the chemotherapeutic treatment of human breast cancer.

NecroX-5 prevents breast cancer metastasis by AKT inhibition via reducing intracellular calcium levels

A major goal of breast cancer research is to prevent the molecular events that lead to tumour metastasis. It is well-established that both cytoplasmic and mitochondrial reactive oxygen species (ROS) play important roles in cell migration and metastasis. Accordingly, this study examined the molecular mechanisms of the anti-metastatic effects of NecroX-5, a mitochondrial ROS scavenger. NecroX-5 inhibited lung cancer metastasis by ameliorating migration in a mouse model. In human cancer cells, the inhibition of migration by NecroX-5 is cell type-dependent. We observed that the effect of NecroX-5 correlated with a reduction in mitochondrial ROS, but mitochondrial ROS reduction by MitoQ did not inhibit cell migration. NecroX-5 decreased intracellular calcium concentration by blocking Ca2+ influx, which mediated the inhibition of cell migration, AKT downregulation and the reduction of mitochondrial ROS levels. However, the reduction of mitochondrial ROS was not associated with supressed migration and AKT downregulation. Our study demonstrates the potential of NecroX-5 as an inhibitor of breast cancer metastasis.

The matricellular protein CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and suppressing anoikis.

Matricellular proteins play multiple roles in primary tumor growth, local invasion and tumor angiogenesis. However, their contribution to metastasis and the putative mechanisms involved are less well characterized. In ER-negative human breast cancer, elevated expression levels of the matricellular protein Cysteine-rich angiogenic inducer 61 (CYR61) are associated with more aggressive progression. Here, we investigated the role of CYR61 in breast cancer lung metastasis using the triple negative human breast cancer cell lines MDA-MB-231 and SUM159. Silencing of CYR61 significantly decreased lung metastasis from tumors orthotopically implanted in pre-irradiated or naive mammary tissue and upon tail vein injection. Constitutive CYR61 silencing impaired cancer cell extravasation to the lung during the first 24 hours after tail vein injection. In contrast, CYR61 inducible silencing starting 24 hours after cancer cell injection had no impact on lung metastasis formation. In vitro experiments revealed that CYR61 silencing decreased cancer cell transendothelial migration and motility, reduced CYR61 levels present at the cell surface and sensitized cancer cells to anoikis. Furthermore, we demonstrate that CYR61-dependent cell survival under non-adhesive conditions relied, at least partially, on β1 integrin ligation and AMPKα signaling while it was independent of AKT, FAK and ERK1/2 activation. Our data provide the first evidence that CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and protecting from anoikis during initial seeding to the lung. The uncovered CYR61-β1 integrin-AMPKα axis may serve as a potential therapeutic target to prevent breast cancer metastasis to the lung.

DHA blocks TPA-induced cell invasion by inhibiting MMP-9 expression via suppression of the PPAR-γ/NF-κB pathway in MCF-7 cells

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is considered to have applications in cancer prevention and treatment. The beneficial effects of DHA against cancer metastasis are well established; however, the mechanisms underlying these effects in breast cancer are not clear. Cell invasion is critical for neoplastic metastasis, and involves the degradation of the extracellular matrix by matrix metalloproteinase (MMP)-9. The present study investigated the inhibitory effect of DHA on MMP-9 expression and cell invasion induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in the MCF-7 breast cancer cell line. DHA inhibited the TPA-induced activation of mitogen-activated protein kinase (MAPK) and the transcription of nuclear factor (NF)-κB, but did not inhibit the transcription of activator protein-1. DHA increased the activity of peroxisome proliferator-activated receptor (PPAR)-γ, an effect that was reversed by the application of the PPAR-γ antagonist GW9662. In addition, combined treatment with GW9662 and DHA increased NF-κB-related protein expression. These results indicate that DHA regulates MMP-9 expression and cell invasion via modulation of the MAPK signaling pathway and PPAR-γ/NF-κB activity. This suggests that DHA could be a potential therapeutic agent for the prevention of breast cancer metastasis.

MiR-503-3p promotes epithelial–mesenchymal transition in breast cancer by directly targeting SMAD2 and E-cadherin

Although progress in clinical and basic research has significantly increased our understanding of breast cancer, little is known about the molecular mechanism underlying breast cancer metastasis. Identification of effective therapeutic targets to prevent breast cancer metastasis is urgently needed. The function of miR-503-3p has been investigated in other cancers, but its role in breast cancer remains undefined. Here, we found that miR-503-3p was overexpressed in breast cancer tissue and plasma compared with adjacent normal breast tissue and with plasma from healthy individuals. Moreover, we identified miR-503-3p to be an oncogene of breast cancer cell proliferation, migration and invasion. Upregulation of miR-503-3p in breast cancer cells inhibited expression of epithelial–mesenchymal transition (EMT)-related protein SMAD2 and the epithelial marker protein E-cadherin by directly binding to their mRNA 3′ untranslated region, whereas increased expression of mesenchymal marker proteins, including vimentin and N-cadherin. Taken together, our findings support a critical role for miR-503-3p in induction of breast cancer EMT and suggest that plasma miR-503-3p may be a useful diagnostic biomarker for breast cancer.

Phosphorylation of calcium/calmodulin-stimulated protein kinase II at T286 enhances invasion and migration of human breast cancer cells.

Calcium/calmodulin-stimulated protein kinase II (CaMKII) is a multi-functional kinase that controls a range of cellular functions, including proliferation, differentiation and apoptosis. The biological properties of CaMKII are regulated by multi-site phosphorylation. However, the role that CaMKII phosphorylation plays in cancer cell metastasis has not been examined. We demonstrate herein that CaMKII expression and phosphorylation at T286 is increased in breast cancer when compared to normal breast tissue, and that increased CAMK2 mRNA is associated with poor breast cancer patient prognosis (worse overall and distant metastasis free survival). Additionally, we show that overexpression of WT, T286D and T286V forms of CaMKII in MDA-MB-231 and MCF-7 breast cancer cells increases invasion, migration and anchorage independent growth, and that overexpression of the T286D phosphomimic leads to a further increase in the invasive, migratory and anchorage independent growth capacity of these cells. Pharmacological inhibition of CaMKII decreases MDA-MB-231 migration and invasion. Furthermore, we demonstrate that overexpression of T286D, but not WT or T286V-CaMKII, leads to phosphorylation of FAK, STAT5a, and Akt. These results demonstrate a novel function for phosphorylation of CaMKII at T286 in the control of breast cancer metastasis, offering a promising target for the development of therapeutics to prevent breast cancer metastasis.

Abstract 1909: miR-30c blocks tumor cell homotypic aggregation and promotes anoikis to prevent breast cancer metastasis

Abstract Circulating tumor cells (CTCs) are considered the seeds of distant metastasis, and may be a predictor of poor prognosis in patients with metastatic breast cancers. Compared to single CTCs, clusters of multiple CTCs possess higher metastatic capacity in mouse breast cancer models, indicating that aggregation increases the survival of CTCs in the circulation. However, the molecular mechanisms by which clustered CTCs mediate tumor cell survival are unclear. In this study, we found that miR-30c, which has been identified as an anti-metastatic microRNAs, inhibited primary breast cancer cell homotypic aggregation in vitro by real-time monitoring. Interestingly, only aggregated but not single tumor cells can survive during culture. The death of dissociated primary tumor cells in vitro is caused by anoikis, a form of programmed cell death which is induced by detachment of anchorage-dependent cells from the surrounding extracellular matrix. Therefore, the role of miR-30c in anoikis was determined by culturing breast cancer cells in poly-hema coated plates. We found that miR-30c promoted anoikis, evaluated by Annexin-V staining and caspase3/7 activity. Mechanistic studies indicated that inhibition of Vimentin (Vim), a positive regulator of epithelial-to-mesenchymal transition (EMT), was required for miR-30c induced anoikis. In vivo, lung metastasis was inhibited by miR-30c after tail vein injection of miR-30c over-expressed cells. In summary, our findings provide the new insights into the mechanisms of miR-30c-mediated metastasis inhibition and suggest that targeting CTC clusters could be a novel strategy to prevent metastasis. Citation Format: Xia Liu, Beijie Yu, Wenjing Chen, Huiping Liu. miR-30c blocks tumor cell homotypic aggregation and promotes anoikis to prevent breast cancer metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1909.

Neuromedin B receptor antagonism inhibits migration, invasion, and epithelial-mesenchymal transition of breast cancer cells.

Neuromedin B (NMB) acts as an autocrine growth factor and a pro-angiogenic factor. Its receptor, NMB receptor (NMB-R), is overexpressed in solid tumors. In the present study, we showed that an NMB-R antagonist, PD168368, suppresses migration and invasion of the human breast cancer cell line MDA-MB-231. In addition, PD168368 reduced epithelial-mesenchymal transition (EMT) of breast cancer cells by E-cadherin upregulation and vimentin downregulation. Moreover, we found that PD168368 potently inhibits invivo metastasis of breast cancer. Taken together, these findings suggest that NMB-R antagonism may be an alternative approach to prevent breast cancer metastasis, and targeting NMB-R may provide a novel therapeutic strategy for breast cancer treatment.

The fibroblast Tiam1-osteopontin pathway modulates breast cancer invasion and metastasis.

BackgroundThe tumor microenvironment has complex effects in cancer pathophysiology that are not fully understood. Most cancer therapies are directed against malignant cells specifically, leaving pro-malignant signals from the microenvironment unaddressed. Defining specific mechanisms by which the tumor microenvironment contributes to breast cancer metastasis may lead to new therapeutic approaches against advanced breast cancer.MethodsWe use a novel method for manipulating three-dimensional mixed cell co-cultures, along with studies in mouse xenograft models of human breast cancer and a histologic study of human breast cancer samples, to investigate how breast cancer-associated fibroblasts affect the malignant behaviors of breast cancer cells.ResultsAltering fibroblast Tiam1 expression induces changes in invasion, migration, epithelial-mesenchymal transition, and cancer stem cell characteristics in associated breast cancer cells. These changes are both dependent on fibroblast secretion of osteopontin and also long-lasting even after cancer cell dissociation from the fibroblasts, indicating a novel Tiam1-osteopontin pathway in breast cancer-associated fibroblasts. Notably, inhibition of fibroblast osteopontin with low doses of a novel small molecule prevents lung metastasis in a mouse model of human breast cancer metastasis. Moreover, fibroblast expression patterns of Tiam1 and osteopontin in human breast cancers show converse changes correlating with invasion, supporting the hypothesis that this pathway in tumor-associated fibroblasts regulates breast cancer invasiveness in human disease and is thus clinically relevant.ConclusionsThese findings suggest a new therapeutic paradigm for preventing breast cancer metastasis. Pro-malignant signals from the tumor microenvironment with long-lasting effects on associated cancer cells may perpetuate the metastatic potential of developing cancers. Inhibition of these microenvironment signals represents a new therapeutic strategy against cancer metastasis that enables targeting of stromal cells with less genetic plasticity than associated cancer cells and opens new avenues for investigation of novel therapeutic targets and agents.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0674-8) contains supplementary material, which is available to authorized users.

Recent Advances in Discovering the Role of CCL5 in Metastatic Breast Cancer.

A variety of therapeutic strategies are currently under investigation to inhibit factors that promote tumor invasion, as metastasis is the most common cause of mortality for cancer patients. Notably, considerable emphasis has been placed on studying metastasis as a dynamic process that is highly dependent on the tumor microenvironment. In regards to breast cancer, chemokine C-C motif ligand 5 (CCL5), which is produced by tumor-associated stromal cells, has been established as an important contributor to metastatic disease. This review summarizes recent discoveries uncovering the role of this chemokine in breast cancer metastasis, including conditions that increase the generation of CCL5 and effects induced by this signaling pathway. In particular, CCL-5-mediated cancer cell migration and invasion are discussed in the context of intertwined feedback loops between breast cancer cells and stromal cells. Moreover, the potential use of CCL5 and its receptor chemokine C-C motif receptor 5 (CCR5) as targets for preventing breast cancer metastasis is also reviewed.

Abstract 4650: Novel resveratrol-analog HPIMBD inhibits breast cancer cell metastasis by reversal of epithelial-mesenchymal transition

Abstract Epithelial-mesenchymal transition (EMT) is a biological process that mediates a phenotypical change in the polarized epithelial cells to mesenchymal cells. The process of EMT increases a cell's migratory and invasive properties. It is well documented that the process of EMT plays a very critical role in cancer metastasis. The objective of this study was to characterize the role of a novel Resveratrol analog 4-(E)-{4-hydroxyphenylimino)-methylbenzene, 1,2-diol} (HPIMBD) on EMT in human breast cancer cells. Human breast cancer cells MDA-MB-231 were treated with Resveratrol (Res) and HPIMBD for up to 48 hours. Protein expression levels of E-cadherin, matrix metalloproteases (MMPs), snail, slug, zeb1/2 and nuclear migration of β-catenin were quantified after treatment with Res or HPIMBD and compared with that of the vehicle-treated control cells. mRNA expression levels of β-catenin and wnt-7b were also quantified. Migration MDA-MB-231 cells was determined after treatment with Res or HPIMBD by wound healing assay. Treatment with HPIMBD significantly up-regulated E-cadherin protein expression levels. The up-regulation of E-cadherin by HPIMBD was associated with suppression of snail, slug and Zeb1 protein levels. HPIMBD significantly down-regulated mRNA expression levels of β-catenin and wnt-7b. Furthermore, HPIMBD restricted nuclear migration of β-catenin. Treatment of breast cancer cells with HPIMBD resulted in down-regulation of MMP3 and MMP9 but not MMP2 protein expression levels. Treatment with HPIMBD also prevented breast cancer cell migration. Our studies demonstrtae that HPIMBD decreases the metastatic properties of breast cancer cells by inhibition of EMT and down-regulation of wnt/β catenin pathway. These findings suggest that HPIMBD may have a potential in inhibtion of EMT and may be explored as as a potential therapy to prevent breast cancer metastasis. Note: This abstract was not presented at the meeting. Citation Format: Anwesha Chatterjee, Amruta Ronghe, Subhash Padhye, Hari K. Bhat. Novel resveratrol-analog HPIMBD inhibits breast cancer cell metastasis by reversal of epithelial-mesenchymal transition. [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 4650. doi:10.1158/1538-7445.AM2015-4650

Abstract 1437: The activity of plasma membrane V-ATPases is critical for the invasion of breast cancer cells

Abstract The V-ATPases are a family of ATP-driven proton pumps that have been implicated in breast cancer cell invasion. V-ATPases are found both intracellularly and on the plasma membrane of specialized acid-secreted cells and invasive cancer cells. As available inhibitors of the V-ATPase are membrane-permeable, it has not yet been examined whether intracellular or plasma membrane pumps are critical for invasiveness. It has been proposed that V-ATPases promote invasiveness by localizing to the plasma membrane. To test this hypothesis, we utilized two approaches to specifically inhibit the V-ATPases at the plasma membrane. First, we stably transfected invasive MB231 breast cancer cells with a V5-tagged construct of the membrane-embedded subunit c. This allows for extracellular expression of the V5 epitope. We then found that addition of an anti-V5 antibody specifically inhibited plasma membrane V-ATPase activity as well as in vitro invasion and migration of MB231 cells. Second, we utilized a biotin-conjugated form of the specific V-ATPase inhibitor bafilomycin to inhibit plasma membrane pumps. When bound to streptavidin, this compound is membrane impermeable. Addition of streptavidin-bound biotin-bafilomycin also inhibited in vitro invasion and migration of MB231 cells. These studies suggest that V-ATPases at the plasma membrane play a critical role in breast cancer cell invasion. We hypothesize that plasma membrane V-ATPases participate in invasion by creating an acidic microenvironment that promotes the activity of pH-dependent proteases. Overall, these results have significant implications for targeting the pump to prevent breast cancer metastasis. Citation Format: Kristina Cotter, Joseph Capecci, Souad Sennoune, Markus Huss, Martin Maier, Raul Martinez-Zaguilan, Michael Forgac. The activity of plasma membrane V-ATPases is critical for the invasion of breast cancer cells. [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 1437. doi:10.1158/1538-7445.AM2015-1437

Focusing downstream for safer immunotherapy

CCL3/CCR1 inhibition shows promise for preventing breast cancer metastasis.

Endothelial ALK1 Is a Therapeutic Target to Block Metastatic Dissemination of Breast Cancer.

Exploration of new strategies for the prevention of breast cancer metastasis is justifiably at the center of clinical attention. In this study, we combined a computational biology approach with mechanism-based preclinical trials to identify inhibitors of activin-like receptor kinase (ALK) 1 as effective agents for blocking angiogenesis and metastasis in breast cancer. Pharmacologic targeting of ALK1 provided long-term therapeutic benefit in mouse models of mammary carcinoma, accompanied by strikingly reduced metastatic colonization as a monotherapy or part of combinations with chemotherapy. Gene-expression analysis of breast cancer specimens from a population-based nested case-control study encompassing 768 subjects defined endothelial expression of ALK1 as an independent and highly specific prognostic factor for metastatic manifestation, a finding that was corroborated in an independent clinical cohort. Overall, our results suggest that pharmacologic inhibition of endothelial ALK1 constitutes a tractable strategy for interfering with metastatic dissemination of breast cancer.

Blocking the Adhesion Cascade at the Premetastatic Niche for Prevention of Breast Cancer Metastasis

Shear-resistant adhesion and extravasation of disseminated cancer cells at the target organ is a crucial step in hematogenous metastasis. We found that the vascular adhesion molecule E-selectin preferentially promoted the shear-resistant adhesion and transendothelial migration of the estrogen receptor (ER)(-)/CD44(+) hormone-independent breast cancer cells, but not of the ER(+)/CD44(-/low) hormone-dependent breast cancer cells. Coincidentally, CD44(+) breast cancer cells were abundant in metastatic lung and brain lesions in ER(-) breast cancer, suggesting that E-selectin supports hematogenous metastasis of ER(-)/CD44(+) breast cancer. In an attempt to prevent hematogenous metastasis through the inhibition of a shear-resistant adhesion of CD44(+) cancer cells to E-selectin-expressing blood vessels on the premetastatic niche, an E-selectin targeted aptamer (ESTA) was developed. We demonstrated that a single intravenous injection of ESTA reduced metastases to a baseline level in both syngeneic and xenogeneic forced breast cancer metastasis models without relocating the site of metastasis. The effect of ESTA was absent in E-selectin knockout mice, suggesting that E-selectin is a molecular target of ESTA. Our data highlight the potential application of an E-selectin antagonist for the prevention of hematogenous metastasis of ER(-)/CD44(+) breast cancer.

Abstract BS2-2: Targeting the LIFR-Hippo-YAP pathway as an anti-metastatic strategy

Abstract Deregulation of signaling pathways that control organ size, such as the Hippo-YAP pathway, can lead to tumor formation and metastatic progression. Several upstream regulators are known to provide inputs feeding into the core Hippo pathway. However, the cell membrane receptors that activate the MST (the mammalian Hippo homolog)-LATS-YAP phosphorylation cascade are elusive. Although G-protein-coupled receptors have been found to regulate LATS and YAP phosphorylation, they act in a Hippo-independent manner and do not regulate MST. Combining high-throughput RNA sequencing, functional characterization, mechanistic studies, and clinical validation, we identified leukemia inhibitory factor receptor (LIFR) as a novel breast cancer metastasis suppressor downstream of the miR-9 microRNA and upstream of Hippo signaling. We found that LIFR suppresses metastasis by promoting cell membrane localization of the adaptor protein Scribble, leading to activation of a Hippo kinase cascade and functional inactivation of the transcriptional co-activator YAP. We found that LIFR is commonly downregulated in human breast cancer, and that loss of LIFR in non-metastatic stage I-III breast tumors was highly associated with poor metastasis-free, recurrence-free, and overall survival outcomes in approximately 1,000 patients. Recently, we generated Lifr conditional knockout (cKO) mice to determine whether genetic deletion of Lifr in the breast and other organs leads to increased organ size, tumorigenesis, and metastasis. Notably, we confirmed that Hippo signaling is shut down in Lifr-deficient adult mouse tissues and primary mouse embryonic fibroblasts. The phenotypic characterization of these mice is under way. In preliminary analyses, we indeed observed enlarged organs in Lifr cKO mice, which is what is expected from inactivation of Hippo signaling. These results further validated LIFR as a receptor that triggers the Hippo pathway. We aim to make translational advances on this finding. By delineating the appropriate cutoffs, detection of LIFR could be implemented in the clinic as a prognostic marker of metastatic relapse. We are also developing therapeutic agents to target the miR-9-LIFR-Hippo-YAP pathway as new anti-metastatic strategies. miR-9 antagomirs and LIFR ligands (such as LIF) could be useful for tumors with downregulation but not complete loss of LIFR, whereas agents targeting the functional YAP targets, such as CTGF, may be useful for tumors with either downregulation or complete loss of LIFR. Recently, we established collaboration with FibroGen to develop a human CTGF-neutralizing antibody (FG-3019) as an anti-metastatic agent in preclinical models of breast cancer. We will also investigate whether the blood level of CTGF can serve as a prognostic marker for metastatic relapse and a predictive marker to select patients that would benefit from FG-3019 treatment. These studies will likely facilitate biomarker-driven personalization of breast cancer metastasis prevention and treatment. Citation Format: Li Ma. Targeting the LIFR-Hippo-YAP pathway as an anti-metastatic strategy [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 BS2-2.