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Platelet-derived growth factor receptor-beta (PDGFRβ) is a receptor tyrosine kinase found in cells of mesenchymal origin such as fibroblasts and pericytes. Activation of this receptor is dependent on paracrine ligand induction, and its preferred ligand PDGFB is released by neighboring epithelial and endothelial cells. While expression of both PDGFRβ and PDGFB has been noted in patient breast tumors for decades, how PDGFB-to-PDGFRβ tumor-stroma signaling mediates breast cancer (BC) initiation, progression, and metastasis remains unclear. Here we demonstrate this paracrine signaling pathway mediates both primary tumor growth and metastasis; specifically, metastasis to the brain. Elevated levels of PDGFB accelerated orthotopic tumor growth and intracranial growth of mammary tumor cells while mesenchymal-specific expression of an activating mutant PDGFRβ (PDGFRβ(D849V)) exerted pro-proliferative signals on adjacent mammary tumor cells. Stromal expression of PDGFRβ(D849V) also promoted brain metastases of mammary tumor cells expressing high PDGFB when injected intravenously. In the brain, expression of PDGFRβ(D849V) was observed within a subset of astrocytes, and aged mice expressing PDGFRβ(D849V) exhibited reactive gliosis. Importantly, the PDGFR-specific inhibitor crenolanib significantly reduced intracranial growth of mammary tumor cells. In a tissue microarray comprised of 363 primary human breast tumors, high PDGFB protein expression was prognostic for brain metastases, but not metastases to other sites. Our results advocate the use of mice expressing PDGFRβ(D849V) in their stromal cells as a preclinical model of BC-associated brain metastases (BCBM) and support continued investigation into the clinical prognostic and therapeutic use of PDGFB-to-PDGFRβ signaling in women with BC.

// Yu-Ting Huang 1, 2, * , Qiang Lan 1, 2, * , Girieca Lorusso 1, 2 , Nathalie Duffey 1 , Curzio Ruegg 1, 2 1 Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland 2 National Center for Competence in Research (NCCR), Molecular Oncology, Swiss Institute for Experimental Cancer Research (ISREC)-Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland * These authors contributed equally to this work Correspondence to: Curzio Ruegg, email: curzio.ruegg@unifr.ch Keywords: CYR61, metastasis, extravasation, anoikis resistance Received: June 20, 2016 Accepted: November 19, 2016 Published: November 29, 2016 ABSTRACT 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 β 1 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-β 1 integrin-AMPKα axis may serve as a potential therapeutic target to prevent breast cancer metastasis to the lung.

Despite the substantial advances obtained in the treatment of localized malignancies, metastatic disease still lacks effective treatment and remains the primary cause of cancer mortality, including in breast cancer. Thus, in order to improve the survival of cancer patients it is necessary to effectively improve prevention or treatment of metastasis. To achieve this goal, complementary strategies can be envisaged: the first one is the eradication of established metastases by adding novel modalities to current treatments, such as immunotherapy or targeted therapies. A second one is to prevent tumor cell dissemination to secondary organs by targeting specific steps governing the metastatic cascade and organ-specific tropism. A third one is to block the colonization of secondary organs and subsequent cancer cell growth by impinging on the ability of disseminated cancer cells to adapt to the novel microenvironment. To obtain optimal results it might be necessary to combine these strategies. The development of therapeutic approaches aimed at preventing dissemination and organ colonization requires a deeper understanding of the specific genetic events occurring in cancer cells and of the host responses that co-operate to promote metastasis formation. Recent developments in the field disclosed novel mechanisms of metastasis. In particular the crosstalk between disseminated cancer cells and the host microenvironment is emerging as a critical determinant of metastasis. The identification of tissue-specific signals involved in metastatic progression will open the way to new therapeutic strategies. Here, we will review recent progress in the field, with particular emphasis on the mechanisms of organ specific dissemination and colonization of breast cancer.

Tumor-mobilized bone marrow–derived CD11b+ myeloid cells promote tumor angiogenesis, but how and when these cells acquire proangiogenic properties is not fully elucidated. Here, we show that CD11b+ myelomonocytic cells develop proangiogenic properties during their differentiation from CD34+ hematopoietic progenitors and that placenta growth factor (PlGF) is critical in promoting this education. Cultures of human CD34+ progenitors supplemented with conditioned medium from breast cancer cell lines or PlGF, but not from nontumorigenic breast epithelial lines, generate CD11b+ cells capable of inducing endothelial cell sprouting in vitro and angiogenesis in vivo. An anti–Flt-1 mAb or soluble Flt-1 abolished the generation of proangiogenic activity during differentiation from progenitor cells. Moreover, inhibition of metalloproteinase activity, but not VEGF, during the endothelial sprouting assay blocked sprouting induced by these proangiogenic CD11b+ myelomonocytes. In a mouse model of breast cancer, circulating CD11b+ cells were proangiogenic in the sprouting assays. Silencing of PlGF in tumor cells prevented the generation of proangiogenic activity in circulating CD11b+ cells, inhibited tumor blood flow, and slowed tumor growth. Peripheral blood of breast cancer patients at diagnosis, but not of healthy individuals, contained elevated levels of PlGF and circulating proangiogenic CD11b+ myelomonocytes. Taken together, our results show that cancer cells can program proangiogenic activity in CD11b+ myelomonocytes during differentiation of their progenitor cells in a PlGF-dependent manner. These findings impact breast cancer biology, detection, and treatment. Cancer Res; 71(11); 3781–91. ©2011 AACR.

Prostate cancer is the most common cancer in men and one of the leading causes of cancer-related deaths in Western countries. The extraordinary biological heterogeneity, the increasing incidence of this disease, and the presence of putative premalignant conditions make prostate cancer a crucial pathology to study and test pharmacological or nutritional chemopreventive strategies. It has been demonstrated that the incidence of prostate cancer is lower in Asian people, and that it increases in Asian men living in Western countries; these data point to a pivotal role of diet in the onset of prostate cancer. A large amount of work has been done in investigating chemopreventive properties of dietary compounds widely used in Asian countries (i.e. soy, soybeans, green tea, fish) in respect of the oxidants- and meatrich diet typical of Western people, particularly of central and northern Europe. Some dietary products appear promising as chemopreventive agents for prostate cancer, because they display both anti-oxidant and anti-inflammatory activity – and inflammation is crucial for the aetiology of adeno-carcinoma of the prostate. There is increasing evidence for close correlation between inflammation, the microenvironment and tumour-associated neo-angiogenesis causing the adverse outcomes of prostate cancer. It may thus be useful to develop new strategies to couple the treatment of inflammation-related prostate cancer and the generation of angiopreventive or antiinflammatory molecules to prevent this disease. The search for compounds with few or no adverse effects – particularly cardiovascular – as compared with the agents currently in use is therefore of greatest relevance. This paper reviews the beneficial effects in this context of the most promising compounds: β-carotene, capsaicin, curcumin, daidzein, EGCG, genistein, hyperforin, lycopene, N-acetyl-L-cysteine, reductase inhibitors, resveratrol, selenium, silybinin, quercetin, vitamin-D and vitamin-E.

Endothelial cell senescence and apoptosis are features of numerous human pathologies including atherosclerosis, allograft vasculopathy, heart failure, diabetic retinopathy and scleroderma. In contrast, endothelial cell activation and replication associated with vessel proliferation and angiogenesis are now therapeutic targets in other diseases such as cancer and macular dystrophy. Finally, preventive medicine, in particular cardiovascular and cancer chemoprevention, commonly involve the endothelium. Here we discuss several aspects of the interplay between endothelial cell aging, apoptosis and senescence. Further, we show novel microarray data on endothelial cells "aged" in culture, and note that many genes regulated by the aging process are also modulated by a chemopreventive anti-angiogenic and anti-apoptotic drug, N-acetyl-cysteine (NAC). Focusing on one of these genes, the leukocyte adhesion protein E-selectin, we show that E-selectin is down-modulated with time in culture and upon treatment with NAC at mRNA and protein levels. This correlates with reduced adhesion of breast cancer cells and NF-kB activation in NAC treated endothelial cells. These data underscore the effects of a chemoprevention agent in modulating parameters associated with endothelial cell aging. © 2008 Bentham Science Publishers Ltd.

Hyperforin (Hyp), a polyphenol-derivative of St. John9s wort ( Hypericum perforatum ), has emerged as key player not only in the antidepressant activity of the plant but also as an inhibitor of bacteria lymphocyte and tumor cell proliferation, and matrix proteinases. We tested whether as well as inhibiting leukocyte elastase (LE) activity, Hyp might be effective in containing both polymorphonuclear neutrophil (PMN) leukocyte recruitment and unfavorable eventual tissue responses. The results show that, without affecting in vitro human PMN viability and chemokine-receptor expression, Hyp (as stable dicyclohexylammonium salt) was able to inhibit in a dose-dependent manner their chemotaxis and chemoinvasion (IC 50 = 1 μM for both); this effect was associated with a reduced expression of the adhesion molecule CD11b by formyl-Met-Leu-Phe-stimulated neutrophils and block of LE-triggered activation of the gelatinase matrix metalloproteinase-9. PMN-triggered angiogenesis is also blocked by both local injection and daily i.p. administration of the Hyp salt in an interleukin-8-induced murine model. Furthermore, i.p. treatment with Hyp reduces acute PMN recruitment and enhances resolution in a pulmonary bleomycin-induced inflammation model, significantly reducing consequent fibrosis. These results indicate that Hyp is a powerful anti-inflammatory compound with therapeutic potential, and they elucidate mechanistic keys.

The p120 RasGAP protein negatively regulates Ras via its GAP domain. RasGAP carries several other domains that modulate several signaling molecules such as Rho. RasGAP is also a caspase-3 substrate. One of the caspase-3-generated RasGAP fragments, corresponding to amino acids 158–455 and called fragment N2, was previously reported to specifically sensitize cancer cells to death induced by various anticancer agents. Here, we show that fragment N2 inhibits migration in vitro and that it impairs metastatic progression of breast cancer to the lung. Hence, stress-activated caspase-3 might contribute to the suppression of metastasis through the generation of fragment N2. These results indicate that the activity borne by fragment N2 has a potential therapeutic relevance to counteract the metastatic process.

TAT-RasGAP(317-326), a peptide corresponding to the 317-326 sequence of p120 RasGAP coupled with a cell-permeable TAT-derived peptide, sensitizes the death response of various tumor cells to several anticancer treatments. We now report that this peptide is also able to increase cell adherence, prevent cell migration and inhibit matrix invasion. This is accompanied by a marked modification of the actin cytoskeleton and focal adhesion redistribution. Interestingly, integrins and the small Rho GTP-binding protein, which are well-characterized proteins modulating actin fibers, adhesion and migration, do not appear to be required for the pro-adhesive properties of TAT-RasGAP(317-326). In contrast, deleted in liver cancer-1, a tumor suppressor protein, the expression of which is often deregulated in cancer cells, was found to be required for TAT-RasGAP(317-326) to promote cell adherence and inhibit migration. These results show that TAT-RasGAP(317-326), besides its ability to favor tumor cell death, hampers cell migration and invasion.

Purpose: Local breast cancer relapse after breast-saving surgery and radiotherapy is associated with increased risk of distant metastasis formation. The mechanisms involved remain largely elusive. We used the well-characterized 4T1 syngeneic, orthotopic breast cancer model to identify novel mechanisms of postradiation metastasis. Experimental Design: 4T1 cells were injected in 20 Gy preirradiated mammary tissue to mimic postradiation relapses, or in nonirradiated mammary tissue, as control, of immunocompetent BALB/c mice. Molecular, biochemical, cellular, histologic analyses, adoptive cell transfer, genetic, and pharmacologic interventions were carried out. Results: Tumors growing in preirradiated mammary tissue had reduced angiogenesis and were more hypoxic, invasive, and metastatic to lung and lymph nodes compared with control tumors. Increased metastasis involved the mobilization of CD11b+c-Kit+Ly6GhighLy6Clow(Gr1+) myeloid cells through the HIF1-dependent expression of Kit ligand (KitL) by hypoxic tumor cells. KitL-mobilized myeloid cells homed to primary tumors and premetastatic lungs, to give rise to CD11b+c-Kit− cells. Pharmacologic inhibition of HIF1, silencing of KitL expression in tumor cells, and inhibition of c-Kit with an anti-c-Kit–blocking antibody or with a tyrosine kinase inhibitor prevented the mobilization of CD11b+c-Kit+ cells and attenuated metastasis. C-Kit inhibition was also effective in reducing mobilization of CD11b+c-Kit+ cells and inhibiting lung metastasis after irradiation of established tumors. Conclusions: Our work defines KitL/c-Kit as a previously unidentified axis critically involved in promoting metastasis of 4T1 tumors growing in preirradiated mammary tissue. Pharmacologic inhibition of this axis represents a potential therapeutic strategy to prevent metastasis in breast cancer patients with local relapses after radiotherapy. Clin Cancer Res; 18(16); 4365–74. ©2012 AACR.

Angiogenesis is the base for solid tumour growth and dissemination, and anti-angiogenic drugs have been demonstrated to be active in clinical trials. In addition, it has become increasingly clear that inflammation is a key component in tumour insurgence. Chemoprevention focuses on the primary or secondary prevention of cancer using natural or synthetic agents that usually show mild or no collateral effects. We have noted that angiogenesis, particularly 'inflammatory angiogenesis', is a common target of many chemopreventive molecules, where they most likely suppress the angiogenic switch in pre-malignant tumours, a concept we have termed 'angioprevention'. We have shown that various molecules, such as flavonoids, antioxidants and retinoids, act in the tumour microenvironment inhibiting the recruitment and/or activation of endothelial cells and phagocytes of the innate immunity. We have recently assessed the activity of novel compounds derived from the oleanolic acid triterpenoid, called CDDO-Me and CDDO-Imm. These compounds show a potent anti-angiogenic activity at low dosages. In vivo they inhibit angiogenesis in the Matrigel sponge assay and in KS-Imm (an immortalized Kaposi's sarcoma cell line) tumour growth. In vitro they are able to prevent endothelial cell tubulogenesis when cultured on Matrigel. In human umbilical vein endothelial (HUVE) cells these compounds can inhibit the activation of the extracellular signal-regulated kinase ERK1/2 pathway after stimulation with vascular endothelial growth factor (VEGF). Moreover, from immunofluorescence experiments we observed that treatment with these triterpenoids prevents nuclear factor NF-kappaB translocation into the nucleus and thereby the activation of downstream pathways. The particularly potent anti-angiogenic activity seen in vivo suggest that CDDO-Me may be interacting with an important network of molecular and cellular targets, on endothelial cells, and could be employed for 'angioprevention'. These substances are being assessed in phase I trials in humans in the United States.

Background Angiostatin, an endogenous angiogenesis inhibitor, is a fragment of plasminogen. Its anti-angiogenic activity was discovered with functional assays in vivo, however, its direct action on endothelial cells is moderate and identification of definitive mechanisms of action has been elusive to date. We had previously demonstrated that innate immune cells are key targets of angiostatin, however the pathway involved in this immune-related angiogenesis inhibition was not known. Here we present evidence that IL-12, a principal TH1 cytokine with potent anti-angiogenic activity, is the mediator of angiostatin's activity. Methods Function blocking antibodies and gene-targeted animals were employed or in vivo studies using the subcutaneous matrigel model of angiogenesis. Quantitative real-time PCR were used to assess modulation of cytokine production in vitro. Results Angiostatin inhibts angiogenesis induced by VEGF-TNFα or supernatants of Kaposi's Sarcoma cells (a highly angiogenic and inflammation-associated tumor). We found that function-blocking antibodies to IL-12 reverted angiostatin induced angiogenesis inhibition. The use of KO animal models revealed that angiostatin is unable to exert angiogenesis inhibition in mice with gene-targeted deletions of either the IL-12 specific receptor subunit IL-12Rβ2 or the IL-12 p40 subunit. Angiostatin induces IL-12 mRNA synthesis by human macrophages in vitro, suggesting that these innate immunity cells produce IL-12 upon angiostatin stimulation and could be a major cellular mediator. Conclusion Our data demonstrate that an endogenous angiogenesis inhibitor such as angiostatin act on innate immune cells as key targets in inflammatory angiogenesis. Angiostatin proves to be anti-angiogenic as an immune modulator rather than a direct anti-vascular agent. This article is dedicated to the memory of Prof Judah Folkman for his leadership and for encouragement of these studies.

Angiogenesis is the base for solid tumour growth and dissemination, and anti-angiogenic drugs have been demonstrated to be active in clinical trials. In addition, it has become increasingly clear that inflammation is a key component in tumour insurgence. Chemoprevention focuses on the primary or secondary prevention of cancer using natural or synthetic agents that usually show mild or no collateral effects. We have noted that angiogenesis, particularly 'inflammatory angiogenesis', is a common target of many chemopreventive molecules, where they most likely suppress the angiogenic switch in pre-malignant tumours, a concept we have termed 'angioprevention'. We have shown that various molecules, such as flavonoids, antioxidants and retinoids, act in the tumour microenvironment inhibiting the recruitment and/or activation of endothelial cells and phagocytes of the innate immunity. We have recently assessed the activity of novel compounds derived from the oleanolic acid triterpenoid, called CDDO-Me and CDDO-Imm. These compounds show a potent anti-angiogenic activity at low dosages. In vivo they inhibit angiogenesis in the Matrigel sponge assay and in KS-Imm (an immortalized Kaposi's sarcoma cell line) tumour growth. In vitro they are able to prevent endothelial cell tubulogenesis when cultured on Matrigel. In human umbilical vein endothelial (HUVE) cells these compounds can inhibit the activation of the extracellular signal-regulated kinase ERK1/2 pathway after stimulation with vascular endothelial growth factor (VEGF). Moreover, from immunofluorescence experiments we observed that treatment with these triterpenoids prevents nuclear factor NF-kappaB translocation into the nucleus and thereby the activation of downstream pathways. The particularly potent anti-angiogenic activity seen in vivo suggest that CDDO-Me may be interacting with an important network of molecular and cellular targets, on endothelial cells, and could be employed for 'angioprevention'. These substances are being assessed in phase I trials in humans in the United States.

Hyperforin, the major lipophilic compound contained in extracts of Hypericum perforatum, is responsible for the antidepressant activity associated with the extract. Recently, several other biological properties of Hyperforin have been unveiled including inhibition of tumour invasion and angiogenesis. The mechanism of the anti-angiogenic activity of Hyperforin remains to be fully elucidated. We show that treatment with non-cytotoxic concentrations of Hyperforin restrains, in a dose-dependent manner, the capacity of endothelial cells to migrate towards relevant chemotactic stimuli. Hyperforin inhibits the organisation of HUVE endothelial cells in capillary-like structures in vitro, and potently represses angiogenesis in vivo in the Matrigel sponge assay in response to diverse angiogenic agents. Immunofluorescent staining shows that in cytokine-activated endothelial HUVE cells Hyperforin prevents translocation to the nucleus of NF-κB, a transcription factor regulating numerous genes involved in cell growth, survival, angiogenesis and invasion. Under Hyperforin treatment in vivo, the growth of Kaposi's sarcoma - a highly angiogenic tumour - is strongly inhibited, with the resultant tumours remarkably reduced in size and in vascularisation as compared with controls. Hyperforin has also been reported to have anti-inflammatory properties. Here we show that Hyperforin inhibits neutrophil and monocyte chemotaxis in vitro and angiogenesis in vivo induced by angiogenic chemokines (CXCL8 or CCL2). These results highlight the potential for Hyperforin as an anti-inflammatory angioprevention agent, acting as a strong inhibitor of inflammation- or tumour-triggered angiogenesis, and provide new therapeutic approaches to halting pathology-associated angiogenesis. © 2009 Elsevier Ltd. All rights reserved.

We show that the synthetic oleanane triterpenoid, CDDO-methyl ester (CDDO-Me; methyl 2-cyano-3,12-dioxoolean-1,9-dien-28-oate) is an effective agent for suppressing angiogenesis, both in cell culture and in vivo. The potency of CDDO-Me is particularly striking when dosed in vivo to inhibit the angiogenic effects of vascular endothelial growth factor and tumor necrosis factor-α in Matrigel sponge assays; activity is seen at i.p. doses of CDDO-Me as low as 0.003 mg/kg of body weight. If the Matrigel sponges are impregnated with CDDO-Me just before implantation in the mice, picomolar doses of CDDO-Me will suppress angiogenesis. CDDO-Me also inhibits growth of endothelial cells in monolayer cultures and suppresses neovascular morphogenesis in three-dimensional cultures, but significantly higher doses (50-200 nmol/L) are required. We also show antiangiogenic effects of CDDO-Me on xenografts of Kaposi's sarcoma cells in immunocompromised mice, using CD31 as a marker. Several known individual molecular targets of CDDO-Me and related triterpenoids that are relevant to all of these findings include nuclear factor-κB signaling, signal transducers and activators of transcription signaling, and transforming growth factor-β signaling, as well as Keap1, the endogenous inhibitor of the transcription factor Nrf2. However, the particularly potent antiangiogenic activity seen in vivo in the present experiments suggest that CDDO-Me, as an angioprevention agent, may be interacting with an entire network of molecular and cellular targets, rather than at a single molecular locus or in a single-cell type. [Mol Cancer Ther 2007;6(12):3139–46]

The intricate interplay between the endothelium and immune cells has been well recognized in the context of immune responses. However, the fact that this inter-relation extends well beyond immune regulation is becoming increasingly recognized, with particular regards to the influence of the immune system on the essential endothelial process of angiogenesis, where the contribution of cytokines drives the angiogenic process. As angiogenesis is an important component of numerous pathological states, among these chronic inflammatory conditions and cancer, understanding the role of cytokines and chemokines in guiding new vessel formation provides key insight into novel therapeutic modalities. Here we review the actions of principal cytokines and chemokines on the angiogenic process and discuss how both can be considered potential pharmaceutical targets or pharmaceuticals themselves for modulation of angiogenesis in chronic inflammation associated with cancer, rheumatoid arthritis and other inflammatory diseases.

Cancer cells acquire cell-autonomous capacities to undergo limitless proliferation and survival through the activation of oncogenes and inactivation of tumor suppressor genes. Nevertheless, the formation of a clinically relevant tumor requires support from the surrounding normal stroma, also referred to as the tumor microenvironment. Carcinoma-associated fibroblasts, leukocytes, bone marrow-derived cells, blood and lymphatic vascular endothelial cells present within the tumor microenvironment contribute to tumor progression. Recent evidence indicates that the microenvironment provides essential cues to the maintenance of cancer stem cells/cancer initiating cells and to promote the seeding of cancer cells at metastatic sites. Furthermore, inflammatory cells and immunomodulatory mediators present in the tumor microenvironment polarize host immune response toward specific phenotypes impacting tumor progression. A growing number of studies demonstrate a positive correlation between angiogenesis, carcinoma-associated fibroblasts, and inflammatory infiltrating cells and poor outcome, thereby emphasizing the clinical relevance of the tumor microenvironment to aggressive tumor progression. Thus, the dynamic and reciprocal interactions between tumor cells and cells of the tumor microenvironment orchestrate events critical to tumor evolution toward metastasis, and many cellular and molecular elements of the microenvironment are emerging as attractive targets for therapeutic strategies.

Neoadjuvant and adjuvant chemotherapies provide survival benefits to breast cancer patients, in particular in estrogen receptor negative (ER-) cancers, by reducing rates of recurrences. It is assumed that the benefits of (neo)adjuvant chemotherapy are due to the killing of disseminated, residual cancer cells, however, there is no formal evidence for it. Here, we provide experimental evidence that ER- breast cancer cells that survived high-dose Doxorubicin and Methotrexate based chemotherapies elicit a state of immunological dormancy. Hallmark of this dormant phenotype is the sustained activation of the IRF7/IFN-β/IFNAR axis subsisting beyond chemotherapy treatment. Upregulation of IRF7 in treated cancer cells promoted resistance to chemotherapy, reduced cell growth and induced switching of the response from a myeloid derived suppressor cell-dominated immune response to a CD4+/CD8+ T cell-dependent anti-tumor response. IRF7 silencing in tumor cells or systemic blocking of IFNAR reversed the state of dormancy, while spontaneous escape from dormancy was associated with loss of IFN-β production. Presence of IFN-β in the circulation of ER- breast cancer patients treated with neoadjuvant Epirubicin chemotherapy correlated with a significantly longer distant metastasis-free survival. These findings establish chemotherapy-induced immunological dormancy in ER- breast cancer as a novel concept for (neo)adjuvant chemotherapy activity, and implicate sustained activation of the IRF7/IFN-β/IFNAR pathway in this effect. Further, IFN-β emerges as a potential predictive biomarker and therapeutic molecule to improve outcome of ER- breast cancer patients treated with (neo)adjuvant chemotherapy., SCOPUS: ar.j, info:eu-repo/semantics/published