Bone Metastasis Formation Research Articles

Systemic PPARγ Antagonism Reduces Metastatic Tumor Progression in Adipocyte-Rich Bone in Excess Weight Male Rodents.

Primary tumors are widely associated with an excess in body fat. The role of adipose tissue on tumor cell homing to bone is yet poorly defined. In this study, we aimed to assess whether bone colonization by tumor cells is favored by an adipocyte-rich bone marrow. We delineated the accompanying alterations of the bone microenvironment and established a treatment approach that interferes with high fat diet (HFD)-induced bone metastasis formation. We were able to show that adipocytes affect skeletal tumor growth in a metastatic model of breast cancer in male rats and melanoma in male mice as well as in human breast cancer bone biopsies. Indeed, HFD-induced bone marrow adiposity was accompanied by accelerated tumor progression and increased osteolytic lesions. In human bone metastases, bone marrow adiposity correlated with tumor cell proliferation. By antagonization of the adipocyte differentiation and storage pathway linked to the peroxisome proliferator-activated receptor gamma (PPARγ) with bisphenol-A-diglycidylether (BADGE), we were able to decelerate tumor progression and subsequent osteolytic damage in the bones of two distinct metastatic animal models exposed to HFD. Overall these data show that adipose tissue is a critical factor in bone metastases and cancer-induced bone loss. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Cellular plasticity in bone metastasis.

Metastasis is responsible for a large majority of death from malignant solid tumors. Bone is one of the most frequently affected organs in cancer metastasis, especially in breast and prostate cancer. Development of bone metastasis requires cancer cells to successfully complete a number of challenging steps, including local invasion and intravasation, survival in circulation, extravasation and initial seeding, and finally, formation of metastatic colonies after a period of dormancy or indolent growth. During this process, cancer cells often undergo a series of cellular and molecular changes to gain cellular plasticity that helps them adapt to various environments they encounter along the journey of metastasis. Understanding the mechanisms behind cellular plasticity and adaptation during the formation of bone metastasis is crucial for the development of novel therapies.

LIGHT as regulator of bone homeostasis during osteolytic bone metastasis formation in non-small cell lung cancer patients

LIGHT as regulator of bone homeostasis during osteolytic bone metastasis formation in non-small cell lung cancer patients

Ephrin-B2-EphB4 communication mediates tumor-endothelial cell interactions during hematogenous spread to spinal bone in a melanoma metastasis model.

Metastases account for the majority of cancer deaths. Bone represents one of the most common sites of distant metastases, and spinal bone metastasis is the most common source of neurological morbidity in cancer patients. During metastatic seeding of cancer cells, endothelial-tumor cell interactions govern extravasation to the bone and potentially represent one of the first points of action for antimetastatic treatment. The ephrin-B2-EphB4 pathway controls cellular interactions by inducing repulsive or adhesive properties, depending on forward or reverse signaling. Here, we report that in an in vivo metastatic melanoma model, ephrin-B2-mediated activation of EphB4 induces tumor cell repulsion from bone endothelium, translating in reduced spinal bone metastatic loci and improved neurological function. Selective ephrin-B2 depletion in endothelial cells or EphB4 inhibition increases bone metastasis and shortens the time window to hind-limb locomotion deficit from spinal cord compression. EphB4 overexpression in melanoma cells ameliorates the metastatic phenotype and improves neurological outcome. Timely harvesting of bone tissue after tumor cell injection and intravital bone microscopy revealed less tumor cells attached to ephrin-B2-positive endothelial cells. These results suggest that ephrin-B2-EphB4 communication influences bone metastasis formation by altering melanoma cell repulsion/adhesion to bone endothelial cells, and represents a molecular target for therapeutic intervention.

Bone metastasis is associated with acquisition of mesenchymal phenotype and immune suppression in a model of spontaneous breast cancer metastasis

The most common site of breast cancer metastasis is the bone, occurring in approximately 70% of patients with advanced disease. Bone metastasis is associated with severe morbidities and high mortality. Therefore, deeper understanding of the mechanisms that enable bone-metastatic relapse are urgently needed. We report the establishment and characterization of a bone-seeking variant of breast cancer cells that spontaneously forms aggressive bone metastases following surgical resection of primary tumor. We characterized the modifications in the immune milieu during early and late stages of metastatic relapse and found that the formation of bone metastases is associated with systemic changes, as well as modifications of the bone microenvironment towards an immune suppressive milieu. Furthermore, we characterized the intrinsic changes in breast cancer cells that facilitate bone-tropism and found that they acquire mesenchymal and osteomimetic features. This model provides a clinically relevant platform to study the functional interactions between breast cancer cells and the bone microenvironment, in an effort to identify novel targets for intervention.

Abstract 3055: Xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, shows efficacy in a human breast cancer model of bone metastasis

Abstract Bone metastases are a frequent complication of cancer and are associated with considerable morbidity. Bones provide a permissive environment for metastatic colonization due to their dynamic turnover and an abundance of secreted factors that are required for bone maintenance. Insulin-like growth factors (IGF) are the most abundant growth factors in bone and are required for normal skeletal development and function. IGFs also promote cancer progression, aggressiveness, and treatment resistance via activation of the IGF-1 receptor (IGF-1R) and insulin receptor variant A (IR-A). Of specific relevance to bone metastases, excessive bone destruction in osteolytic metastatic lesions leads to a release of IGF-1 from the bone matrix, thus promoting proliferation of metastatic tumor cells, stimulating tumor cell homing to bones, and contributing to further enhancement of bone destruction. Therapeutic targeting of the IGF axis may therefore provide an effective method for treating bone metastases. The aim of this study was to explore the efficacy of the IGF-1/-2 ligand blocking antibody, xentuzumab (BI 836845[1]), alone and in combination with the mTOR inhibitor everolimus, in a breast cancer bone metastasis xenograft model. MDA-231-BoM cells[2], a subline of MDA-MB-231 selected in vivo for enhanced metastatic ability to bone, were injected intra-cardiacly to form bone metastases, and via tail vein to form lung/visceral metastases and treated with xentuzumab, everolimus, and the combination thereof. Tumor burden was monitored by bioluminescence imaging, and metastasis-associated osteolysis was measured by quantitative bone micro-computed tomography. Tumor-associated morbidity was evaluated by a multi-parameter health scoring scheme. Metastatic tumor burden in the bone was significantly reduced upon treatment with xentuzumab in monotherapy and in combination with everolimus vs. placebo. Xentuzumab (±everolimus) reduced the number and size of osteolytic lesions, delayed and diminished bone metastasis-associated morbidity, and prolonged survival. In contrast, the growth of lung/visceral metastases developing upon intravenous injection of tumor cells was not inhibited by xentuzumab. In summary, the IGF-1/-2 neutralizing antibody xentuzumab showed efficacy in a breast cancer bone metastasis model (with and without everolimus) but did not affect metastatic tumor growth in lung/visceral organs. A phase II trial evaluating the xentuzumab/ everolimus/ exemestane triple combination in HR+BC patients with non-visceral disease is currently ongoing (NCT03659136). [1] Friedbichler et al, 2014. Mol Cancer Ther 13(2):399 [2] Kang et al, 2003. Cancer Cell 3:537 Citation Format: Ulrike Weyer-Czernilofsky, Izabela Krecioch, Stephan Handschuh, Martin Glösmann, Mario Kuttke, Robin Jacob, Anna C. Obenauf. Xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, shows efficacy in a human breast cancer model of bone metastasis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3055.

Osteoclast Signal Transduction During Bone Metastasis Formation.

Osteoclasts are myeloid lineage-derived bone-resorbing cells of hematopoietic origin. They differentiate from myeloid precursors through a complex regulation process where the differentiation of preosteoclasts is followed by intercellular fusion to generate large multinucleated cells. Under physiological conditions, osteoclastogenesis is primarily directed by interactions between CSF-1R and macrophage colony-stimulating factor (M-CSF, CSF-1), receptor activator of nuclear factor NF-κB (RANK) and RANK ligand (RANKL), as well as adhesion receptors (e.g., integrins) and their ligands. Osteoclasts play a central role in physiological and pathological bone resorption and are also required for excessive bone loss during osteoporosis, inflammatory bone and joint diseases (such as rheumatoid arthritis) and cancer cell-induced osteolysis. Due to the major role of osteoclasts in these diseases the better understanding of their intracellular signaling pathways can lead to the identification of potential novel therapeutic targets. Non-receptor tyrosine kinases and lipid kinases play major roles in osteoclasts and small-molecule kinase inhibitors are emerging new therapeutics in diseases with pathological bone loss. During the last few years, we and others have shown that certain lipid (such as phosphoinositide 3-kinases PI3Kβ and PI3Kδ) and tyrosine (Src−family and Syk) kinases play a critical role in osteoclast differentiation and function in humans and mice. Some of these signaling pathways shows similarity to immunoreceptor-like receptor signaling and involves important other enzymes (e.g., PLCγ2) and adapter proteins (such as the ITAM−bearing adapters DAP12 and the Fc-receptor γ-chain). Here, we review recently identified osteoclast signaling pathways and their role in osteoclast differentiation and function as well as pathological bone loss associated with osteolytic tumors of the bone. A better understanding of osteoclast signaling may facilitate the design of novel and more efficient therapies for pathological bone resorption and osteolytic skeletal metastasis formation.

Role of Bone Targeting Agents in the Prevention of Bone Metastases from Breast Cancer.

Breast cancer (BC) is the most common malignancy in women worldwide and leads, in more than 70% of patients with advanced disease, to skeleton colonization and formation of bone metastases (BM). This condition implies a severe disability and deterioration of the quality of life, with consequent additional social costs. In recent decades, several studies explored the role of agents acting within the bone microenvironment to counteract BM development, and several bone-targeting agents (BTAs) have been introduced in the clinical practice to manage bone lesions and reduce the risk of skeletal complications. However, long-term exposure to these agents is not free from potential toxicities and needs careful monitoring. In this context, the potential capability to prevent BM onset in selected BC patients, through the early administration of BTAs, has been explored by several researchers, with the belief that “prevention is better than cure” and that, ultimately, metastatic BC is an incurable condition. Here, we revised the mechanisms of BM development in BC as well as the strategies for selecting high-risk patients suitable for early BTA treatment.

TIE2 Induces Breast Cancer Cell Dormancy and Inhibits the Development of Osteolytic Bone Metastases.

Breast cancer (BCa) cells disseminating to the bone can remain dormant and resistant to treatments for many years until relapsing as bone metastases. The tyrosine kinase receptor TIE2 induces the dormancy of hematopoietic stem cells, and could also induce the dormancy of BCa cells. However, TIE2 is also a target for anti-angiogenic treatments in ongoing clinical trials, and its inhibition could then restart the proliferation of dormant BCa cells in bone. In this study, we used a combination of patient data, in vitro, and in vivo models to investigate the effect of TIE2 in the dormancy of bone metastases. In BCa patients, we found that a higher TIE2 expression is associated with an increased time to metastases and survival. In vitro, TIE2 decreased cell proliferation as it increased the expression of cyclin-dependent kinase inhibitors CDKN1A and CDKN1B and arrested cells in the G0/G1 phase. Expression of TIE2 also increased the resistance to the chemotherapeutic 5-Fluorouracil. In mice, TIE2 expression reduced tumor growth and the formation of osteolytic bone metastasis. Together, these results show that TIE2 is sufficient to induce dormancy in vitro and in vivo, and could be a useful prognostic marker for patients. Our data also suggest being cautious when using TIE2 inhibitors in the clinic, as they could awaken dormant disseminated tumor cells.

Non-coding RNAs in bone remodelling and bone metastasis: Mechanisms of action and translational relevance.

Bone metastases are frequent complications in patients with advanced cancer, which can be fatal or may rapidly impede the quality of life of patients. Current treatments for patients with bone metastases are palliative. Therefore, a better understanding of the molecular mechanisms that precede the overt development of skeletal lesions could lead to better therapeutic interventions. In this review, we present evidence that non-coding RNAs (ncRNAs) such as long ncRNAs, microRNAs, and circular RNAs are emerging as master regulators of bone metastasis formation. We highlight potential opportunities for the therapeutic targeting of ncRNAs. Furthermore, we discuss the possibility that ncRNAs may be used as biomarkers in the context of bone metastases, which might provide insight for improving the response to current bone-targeting therapies. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

The Effects of TGF-β Signaling on Cancer Cells and Cancer Stem Cells in the Bone Microenvironment.

Background: Transforming growth factor-β (TGF-β) plays a key role in bone metastasis formation; we hypothesized the possible involvement of TGF-β in the induction of cancer stem cells (CSCs) in the bone microenvironment (micro-E), which may be responsible for chemo-resistance. Methods: Mouse mammary tumor cells were implanted under the dorsal skin flap over the calvaria and into a subcutaneous (subQ) lesions in female mice, generating tumors in the bone and subQ micro-Es. After implantation of the tumor cells, mice were treated with a TGF-β R1 kinase inhibitor (R1-Ki). Results: Treatment with R1-Ki decreased tumor volume and cell proliferation in the bone micro-E, but not in the subQ micro-E. R1-Ki treatment did not affect the induction of necrosis or apoptosis in either bone or subQ micro-E. The number of cells positive for the CSC markers, SOX2, and CD166 in the bone micro-E, were significantly higher than those in the subQ micro-E. R1-Ki treatment significantly decreased the number of CSC marker positive cells in the bone micro-E but not in the subQ micro-E. TGF-β activation of the MAPK/ERK and AKT pathways was the underlying mechanism of cell proliferation in the bone micro-E. BMP signaling did not play a role in cell proliferation in either micro-E. Conclusion: Our results indicated that the bone micro-E is a key niche for CSC generation, and TGF-β signaling has important roles in generating CSCs and tumor cell proliferation in the bone micro-E. Therefore, it is critically important to evaluate responses to chemotherapeutic agents on both cancer stem cells and proliferating tumor cells in different tumor microenvironments in vivo.

Multiple actions of parathyroid hormone-related protein in breast cancer bone metastasis.

The sequence similarity within the amino-terminal regions of parathyroid hormone (PTH) and PTH-related protein (PTHrP) allows the two to share actions at a common site, the PTH1 receptor. A number of biological activities have been ascribed to actions of other domains within PTHrP. PTHrP production by late stage breast cancer has been shown to contribute to bone metastasis formation through promotion of osteoclast formation and bone resorption by action through PTH1 receptors. There is evidence also for a role for PTHrP early in breast cancer that is protective against tumour progression. No signalling pathway has been identified for this effect. PTHrP has also been identified as a factor promoting the emergence of breast cancer cells from dormancy in bone. In that case, PTHrP does not function through activation of PTH1 receptors, despite having very substantial effects on transcriptional activity of the breast cancer cells. This indicates actions of PTHrP that are non-canonical, that is, mediated through domains other than the amino-terminal. It is concluded that PTHrP has several distinct paracrine, autocrine, and intracrine actions in the course of breast cancer pathophysiology. Some are mediated through action at PTH1 receptors and others are controlled by other domains within PTHrP. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

Abstract 4614: Establishment of a HER2 positive breast cancer bone metastasis model for validation of novel therapies

Abstract Breast cancers with overexpression of human epidermal growth factor receptor 2 (HER2+) have aggressive clinical behavior, and at advanced stages are associated with increased risk for developing metastases to distant organs including bones, brain and lungs. The aim of this study was to establish a systemic metastasis model for HER2+ breast cancer with a special interest in bone metastasis. The effects of cell number, estrogen supplementation and mouse strain on metastasis formation were studied. In the study, 5-6 weeks old athymic nude and Rag2 mice (n=10-13 per group) were used. Half of the mice received estrogen supplementation (E2-releasing rods 5µg/day) one week before inoculation of the cancer cells. The mice were inoculated intracardially with 1 or 5 x 105 luciferase-labelled triple-positive (ER, PR positive and HER2 overexpressing) human BT-474 breast cancer cells. The formation of metastases was followed by bioluminescence imaging (BLI) at inoculation and once a week for the duration of the study. At sacrifice, X-ray imaging was performed and the bones were collected for histological analysis. The formation of bone metastases was observed in all study groups, and bone metastases were dominant in the model. Based on BLI, bone metastases developed in nude mice earlier than in Rag2 mice. However, detection of metastases in Rag2 mice was challenging due to dark fur hindering the signal transmittance. The bone metastases appeared between 7 to 36 days after inoculation of the cancer cells in nude mice and between 20 to 43 days in Rag2 mice. The number of bone metastases was higher in nude mice. E2 supplement accelerated the development of bone metastases in both mouse strains. In nude mice with E2 supplement, bone metastases appeared between 7 to 14 days compared to between 20 to 36 days in mice without E2 supplement. In Rag2 mice with E2 supplement bone metastases formed between 20 to 28 days compared to between 36 to 43 days without E2 supplement. The use of higher cell number accelerated the development of bone metastases but had no major effect on their incidence in both mouse strains. Take rate of bone metastases was 90-100% in nude mice with E2 supplement compared to 30-50% without E2 supplement. In Rag2 mice, the take rate of bone metastases was 50% with E2 supplement. X-ray imaging showed estrogen induced bone growth and large tumor-induced osteolytic lesions in the hind limbs in both strains. Due to the extensive bone lesions and occasional fractures, the first mice were sacrificed 50 days after inoculation of the cancer cells. Both mouse strains occasionally developed metastases in soft tissues including brain and ovaries. In conclusion, a high rate of bone metastasis was achieved in athymic nude mice supplemented with E2. This model can be used to study the efficacy of anti-cancer, such as HER2-targeted, compounds on tumor growth at metastatic locations or on the prevention of metastasis formation. Citation Format: Tiina E. Kähkönen, Mari I. Suominen, Jenni H. Mäki-Jouppila, Jussi M. Halleen, Jenni Bernoulli, Derek Grant. Establishment of a HER2 positive breast cancer bone metastasis model for validation of novel therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4614.

Deregulated miRNAs in osteoporosis: effects in bone metastasis.

Starting from their role exerted on osteoblast and osteoclast differentiation and activity pathways, microRNAs (miRNAs) have been recently identified as regulators of different processes in bone homeostasis. For this purpose, in a recent review, we highlighted, as deregulated miRNAs could be involved in different bone diseases such as osteoporosis. In addition, recent studies supported the concept that osteoporosis-induced bone alterations might offer a receptive site for cancer cells to form bone metastases, However, to date, no data on specific-shared miRNAs between osteoporosis and bone metastases have been considered and described to clarify the evidence of this link. The main goal of this review is to underline as deregulated miRNAs in osteoporosis may have specific roles in the development of bone metastases. The review showed that several circulating osteoporotic miRNAs could facilitate tumor progression and bone-metastasis formation in several tumor types, i.e., breast cancer, prostate cancer, non-small-cell lung cancer, esophageal squamous cell carcinoma, and multiple myeloma. In detail, serum up-regulation of pro-osteoporotic miRNAs, as well as serum down-regulation of anti-osteoporotic miRNAs are common features of all these tumors and are able to promote bone metastasis. These results are of key importance and could help researcher and clinicians to establish new therapeutic strategies connected with deregulation of circulating miRNAs and able to interfere with pathogenic processes of osteoporosis, tumor progressions, and bone-metastasis formation.

Bone vascular niche E-selectin induces mesenchymal-epithelial transition and Wnt activation in cancer cells to promote bone metastasis.

SUMMARYHow disseminated tumor cells (DTCs) engage specific stromal components in distant organs for survival and outgrowth is a critical but poorly understood step of the metastatic cascade. Previous studies have demonstrated the importance of the epithelial-mesenchymal transition (EMT) in promoting the cancer stem cell properties needed for metastasis initiation, while the reverse process of mesenchymal-epithelial transition (MET) is required for metastatic outgrowth. Here we report that this paradoxical requirement for simultaneous induction of both MET and cancer stem cell traits in DTCs is provided by bone vascular niche E-selectin, whose direct binding to cancer cells promotes bone metastasis by inducing MET and activating Wnt signaling. E-selectin binding activity mediated by α1–3 Fucosyltransferases Fut3/Fut6 and Glg1 are instrumental to the formation of bone metastasis. These findings provide unique insights into the functional role of E-selectin as a component of the vascular niche critical for metastatic colonization in bone.

The Uncovered Role of Immune Cells and NK Cells in the Regulation of Bone Metastasis.

Bone is one of the main metastatic sites of solid tumors like breast, lung, and prostate cancer. Disseminated tumor cells (DTCs) and cancer stem cells (CSCs) represent the main target to counteract bone metastatization. These cells often localize in bone marrow (BM) at level of pre-metastatic niche: they can remain dormant for years or directly grow and create bone lesion, according to the different stimulations received in BM. The immune system in bone marrow is dampened and represents an appealing site for DTCs/CSCs. NK cells have an important role in controlling tumor progression, but their involvement in bone metastasis formation is an interesting and not fully investigated issue. Indeed, whether NK cells can interfere with CSC formation, kill them at the site of primary tumor, during circulation or in the pre-metastic niche needs to be elucidated. This review focuses on different aspects that regulate DTC/CSC life in bone and how NK cells potentially control bone metastasis formation.

Abstract P1-05-01: Breast cancer cell-derived IL-1B drives metastasis and colonisation of the bone microenvironment

Abstract Background: Breast cancer bone metastases are incurable and new therapeutic targets needed. After homing and colonising bone, cancer cells remain dormant, until signals from the microenvironment stimulate their proliferation to form overt metastases. We have recently identified interleukin-1B (IL-1B) as a potential marker for predicting breast cancer patients at increased risk of skeletal relapse and established a role for IL-1 signalling in tumour dormancy in bone. Here we present novel data to support that tumour cell-derived IL-1B plays major roles in breast cancer metastasis and growth in bone. Methods: Tumour/stromal IL-B and IL-1R1 expression was assessed in samples from the AZURE study following immunohistochemical staining. A humanised mouse model of MDA-MB-231 bone metastasis was used to assess effects of the IL-1R antagonist, Anakinra, on tumour growth and spontaneous metastasis. Effects of tumour cell-derived IL-1B on parameters associated with epithelial to mesenchymal transition and metastasis were measured by ELISA, QPCR, Western blot, transwell and scratch assays in MDA-MB-231, MCF7 and T47D cells transfected with IL-1B/control. Homing of breast cancer cells to bone was monitored in BALB/c nude mice intra venously injected with IL-1B overexpressing/control cells. To assess anti-tumour effects of IL-1 inhibition combined with standard of care, BALB/c or C57BL/6 mice were injected with 4T1 or E0771 cells (intra cardiac or intra ductal) 7-days prior to administration of Anakinra, doxorubicin, zoledronic acid (ZA) or placebo, alone or in combination for 14 days. Results: In tissue samples from >1300 patients with stage II/III breast cancer, active IL-1B in tumour cells correlated with relapse in bone (hazard ratio 1.85; 95% CI 1.05-3.26; P=0.02) and other sites (hazard ratio 2.09; 95% CI 1.26-3.48; P=0.0016). In a model of spontaneous human breast cancer metastasis to human bone, Anakinra significantly reduced metastasis to bone (from 80% in control animals to, 20% in Anakinra treated mice) and reduced the number of tumour cells shed into the circulation. Genetic manipulation of breast cancer cells to overexpress IL-1B demonstrated that exogenous production of IL-1B promoted EMT (decreased E-Cadherin, N-Cadherin and G-Catenin), invasion, migration and organ-specific homing in ER-ve (MDA-MB-231) and ER+ve (T47D and MCF7) cells in vitro and in vivo. Contact between tumour cells and osteoblasts or bone marrow cells increased IL-1B secretion from all three cell types. Exposure of tumour cells to IL-1B in the absence of bone cells did not stimulate tumour cell proliferation. Instead, elevated concentrations of IL-1B caused expansion of the bone metastatic niche (increased osteoblasts and blood vessels) that in turn stimulated tumour proliferation. Adding Anakinra to chemotherapy and ZA to mice injected with E0771 cells completely prevented bone metastasis formation and reduced extra-skeletal metastasis by 33%. In mice injected with 4T1 cells, the triple combination therapy reduced bone metastasis by 50% and extra-skeletal metastases by 65%. Conclusion: Our novel data demonstrate that IL-1B/IL-1R1 signalling plays an important role in breast cancer metastasis to bone. Pharmacological inhibition of IL-1B has potential as a novel treatment. Citation Format: Ottewell PD, Lefley DV, Freeman K, Gregory WM, Hanby AM, Spicer-Hadlington AR, Liu X, Bradbury SM, Hambley L, Allocca G, Cookson V, Kruithof de-Julio M, Coleman RE, Brown JE, Holen I, Tulotta C. Breast cancer cell-derived IL-1B drives metastasis and colonisation of the bone microenvironment [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-05-01.

Species-dependent extracranial manifestations of a brain seeking breast cancer cell line.

PurposeMetastatic brain tumors pose a severe problem in the treatment of patients with breast carcinoma. Preclinical models have been shown to play an important role in unraveling the underlying mechanisms behind the metastatic process and evaluation of new therapeutic approaches. As the size of the rat brain allows improved in vivo imaging, we attempted to establish a rat model for breast cancer brain metastasis that allows follow-up by 7 tesla (7T) preclinical Magnetic Resonance Imaging (MRI).ProceduresGreen fluorescent protein-transduced (eGFP) MDA-MB-231br breast cancer cells were labeled with micron-sized particles of iron oxide (MPIOs) and intracardially injected in the left ventricle of female nude rats and mice. 7T preclinical MRI was performed to show the initial distribution of MPIO-labeled cancer cells and to visualize metastasis in the brain. Occurrence of potential metastasis outside the brain was evaluated by 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET)/computed tomography (CT) and potential bone lesions were assessed using [18F]sodium fluoride ([18F]NaF) PET/CT.ResultsThe first signs of brain metastasis development were visible as hyperintensities on T2-weighted (T2w) MR images acquired 3 weeks after intracardiac injection in rats and mice. Early formation of unexpected bone metastasis in rats was clinically observed and assessed using PET/CT. Almost no bone metastasis development was observed in mice after PET/CT evaluation.ConclusionsOur results suggest that the metastatic propensity of the MDA-MB-231br/eGFP cancer cell line outside the brain is species-dependent. Because of early and abundant formation of bone metastasis with the MDA-MB-231br/eGFP cancer cell line, this rat model is currently not suitable for investigating brain metastasis as a single disease model nor for evaluation of novel brain metastasis treatment strategies.

Autotaxin-β interaction with the cell surface via syndecan-4 impacts on cancer cell proliferation and metastasis.

Autotaxin (ATX) promotes cancer cell metastasis through the production of lysophosphatidic acid (LPA). ATX binds to αvβ3 integrins controlling metastasis of breast cancer cells. We screened a series of cancer cell lines derived from diverse human and mouse solid tumors for the capacity of binding to ATX and found only a modest correlation with their level of αvβ3 integrin expression. These results strongly suggested the existence of another cell surface ATX-interacting factor. Indeed, ATXα has been shown to bind heparan-sulfate chains because of its unique polybasic insertion sequence, although the biological significance is unknown. We demonstrated here, that among all cell surface heparan-sulfate proteoglycans, syndecan-4 (SDC4) was essential for cancer cell interaction with ATXβ but was restrained by heparan-sulfate chains. In addition, exogenous ATXβ-induced MG63 osteosarcoma cell proliferation required physical interaction of ATXβ with the cell surface via an SDC4-dependent mechanism. In a preclininal mouse model, targeting SDC4 on 4T1 mouse breast cancer cells inhibited early bone metastasis formation. Furthermore, SDC4-prometastatic activity was totally abolished in absence of ATX expression. In conclusion our results determined that ATX and SDC4 are engaged in a reciprocal collaboration for cancer cell metastasis providing the rational for the development of novel anti-metastasis therapies.

Bone metastasis treatment modeling via optimal control.

Metastatic disease is a lethal stage of cancer progression. It is characterized by the spread of aberrant cells from a primary tumor to distant tissues like the bone. Several treatments are used to deal with bone metastases formation, but they are palliative since the disease is considered incurable. Computational and mathematical models are used to understand the underlying mechanisms of how bone metastasis evolves. In this way, new therapies aiming to reduce or eliminate the metastatic burden in the bone tissue may be proposed. We present an optimal control approach to analyze some common treatments for bone metastasis. In particular, we focus on denosumab treatment, an anti-resorptive therapy, and radiotherapy treatment which has a cell killing action. We base our work in a variant of an existing model introduced by Komarova. The new model incorporates a logistic equation in order to describe the bone metastasis evolution. We provide proofs of existence and uniqueness of solutions to the corresponding optimal control problems for each treatment. Moreover, we present some numerical simulations to analyze the effectiveness of both treatments when different interactions between cancer and bone cells occur. A discussion of the obtained results is provided.