Purpose: Novel therapeutic targets of estrogen receptor (ER)–positive breast cancers are urgently needed because current antiestrogen therapy causes severe adverse effects, nearly 50% of patients are intrinsically resistant, and the majority of recurrences have maintained ER expression. We investigated the role of estrogen-dependent chemokine expression and subsequent cancer growth in human tissues and experimental breast cancer models. Experimental Design: For in vivo sampling of human chemokines, microdialysis was used in breast cancers of women or normal human breast tissue before and after tamoxifen therapy. Estrogen exposure and targeted therapies were assessed in immune competent PyMT murine breast cancer, orthotopic human breast cancers in nude mice, cell culture of cancer cells, and freshly isolated human macrophages. Cancer cell dissemination was investigated using zebrafish. Results: ER⁺ cancers in women produced high levels of extracellular CCL2 and CCL5 in vivo, which was associated with infiltration of tumor-associated macrophages. In experimental breast cancer, estradiol enhanced macrophage influx and angiogenesis through increased release of CCL2, CCL5, and vascular endothelial growth factor. These effects were inhibited by anti-CCL2 or anti-CCL5 therapy, which resulted in potent inhibition of cancer growth. In addition, estradiol induced a protumorigenic activation of the macrophages. In a zebrafish model, macrophages increased cancer cell dissemination via CCL2 and CCL5 in the presence of estradiol, which was inhibited with anti-CCL2 and anti-CCL5 treatment. Conclusions: Our findings shed new light on the mechanisms underlying the progression of ER⁺ breast cancer and indicate the potential of novel therapies targeting CCL2 and CCL5 pathways. Clin Cancer Res; 21(16); 3794–805. ©2015 AACR.

Matrix metalloproteinases (MMPs) have been suggested as therapeutic targets in cancer treatment, but broad-spectrum MMP inhibitors have failed in clinical trials. Recent data suggest that several MMPs including MMP-9 exert both pro- and antitumorigenic properties. This is also the case of the natural inhibitors of MMPs, tissue inhibitor of metalloproteinases (TIMPs). The inhibitor of MMP-9 is TIMP-1, and high levels of this enzyme have been associated with decreased survival in breast cancer. Inflammation is one hallmark of cancer progression, and MMPs/TIMPs may be involved in the local immune regulation. We investigated the role of MMP-9/TIMP-1 in regulating innate antitumor immunity in breast cancer. Breast cancers were established in nude mice and treated with intratumoral injections of adenoviruses carrying the human TIMP-1 or MMP-9 gene (AdMMP-9). In vivo microdialysis for sampling of cancer cell–derived (human) and stroma-derived (murine) proteins, immunostainings, as well as cell cultures were performed. We report a dose-dependent decrease of tumor growth and angiogenesis after AdMMP-9 treatment. In addition to increased generation of endostatin, AdMMP-9 promoted an antitumor immune response by inducing massive neutrophil infiltration. Neutrophil depletion prior to gene transfer abolished the therapeutic effects of AdMMP-9. Additionally, AdMMP-9 activated tumor-infiltrating macrophages into a tumor-inhibiting phenotype both in vivo and in vitro. AdMMP-9 also inhibited tumor growth in immune-competent mice bearing breast cancers. Adenoviruses carrying the human TIMP-1 gene had no effect on tumor growth or the immune response. Our novel data identify MMP-9 as a potent player in modulating the innate immune response into antitumor activities.

Estradiol (E2) plays a key role in breast cancer progression. Most breast cancer recurrences express the estrogen receptor (ER), but nearly 50% of patients are resistant to antiestrogen therapy. Novel therapeutic targets of ER-positive breast cancers are needed. Protumoral neutrophils expressing the lymphocyte function-associated antigen 1 (LFA-1) integrin may mediate cancer metastasis, and TGFβ1 is the major chemoattractant for neutrophils. The role of E2 in neutrophil–ER+ breast cancer cell interactions is unknown. We studied this in vivo using murine breast cancers in immunocompetent mice and human breast cancers in nude mice. Cell dissemination was evaluated in a zebrafish model, and microdialysis of breast cancer patients was performed. In vitro studies were done with mammosphere cultures of breast cancer cells and human neutrophils. We found that E2 increased the number of LFA-1+ neutrophils recruited to the invasive edge of mouse tumors, increased TGFβ1 secretion and promoted neutrophil infiltration in mammospheres, and induced overexpression of LFA-1 in neutrophils. In zebrafish, in the presence of E2, neutrophils increased dissemination of ER+ breast cancer cells via LFA-1 and TGFβ1, thus causing noninvasive cancer cells to be highly metastatic. Time-lapse imaging in zebrafish revealed close interactions of neutrophils with cancer cells, which drove breast cancer metastasis. We also found that extracellular TGFβ1 was overproduced in human breast cancer tissue compared with adjacent normal breast tissue. Thus, E2 can regulate immune/cancer cell interactions in tumor microenvironments. Our results indicate that extracellular TGFβ1 is a relevant target in human breast cancer. Cancer Immunol Res; 5(3); 234–47. ©2017 AACR.

Fulvestrant inhibits growth of triple negative breast cancer and synergizes with tamoxifen in ERa positive breast cancer by up-regulation of ERβ

Angiogenesis is a key in cancer progression and its regulators are released both by the tumor cells and the stroma. Dietary phytoestrogens, such as the lignan enterolactone (ENL) and the isoflavone genistein (GEN), may differently affect breast cancer growth. In this study, human breast cancer cells (MCF‐7) were established in mice creating a tumor with species‐specific cancer and stroma cells. Ovariectomized athymic mice supplemented with estradiol (E2) were fed basal AIN‐93G diet (BD) or BD supplemented with 100 mg/kg ENL, 100 mg/kg GEN or their combination (ENL+GEN). We show that ENL and ENL+GEN inhibited E2‐induced cancer growth and angiogenesis, whereas GEN alone did not. Microdialysis was used to sample extracellular proteins in tumors in vivo. ENL and ENL+GEN decreased both stroma‐ and cancer cell‐derived VEGF, whereas cancer cell‐derived PlGF increased. In subcutaneous Matrigel plugs in mice, ENL and ENL+GEN decreased E2‐induced endothelial cell infiltration, whereas GEN alone did not. In endothelial cells, ENL inhibited E2‐induced VEGFR‐2 expression, whereas GEN did not. These results suggest that ENL has potent effects on breast cancer growth, even in combination with GEN, by downregulating E2‐stimulated angiogenic factors derived both from the stroma and the cancer cells, whereas dietary GEN does not possess any antiestrogenic effects.

Fat is a major tissue component in human breast cancer (BC). Whether breast adipocytes (BAd) affect early stages of BC metastasis is yet unknown. BC progression is dependent on angiogenesis and inflammation, and interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) are key regulators of these events. Here, we show that BAd increased the dissemination of estrogen receptor positive BC cells (BCC) in vivo in the zebrafish model of metastasis, while dissemination of the more aggressive and metastatic BCC such as estrogen receptor negative was unaffected. While anti-VEGF and anti-IL-8 exhibited equal inhibition of angiogenesis at the primary tumor site, anti-IL-8 reduced BCC dissemination whereas anti-VEGF had minor effects on this early metastatic event. Mechanistically, overexpression of cell-adhesion molecules in BCC and neutrophils via IL-8 increased the dissemination of BCC. Importantly, the extracellular in vivo levels of IL-8 were 40-fold higher than those of VEGF in human BC. Our results suggest that IL-8 is a clinical relevant and promising therapeutic target for human BC.