RANKL-dependent and RANKL-independent mechanisms of macrophage-osteoclast differentiation in breast cancer

Oroxylin A suppresses breast cancer-induced osteoclastogenesis and osteolysis as a natural RON inhibitor

BACKGROUND

Malignant breast cancer cells trigger the over-activation of osteoclast precursor cells, leading to bone loss and severe pain. Targeted inhibition of osteoclast differentiation has emerged as an important strategy for treating bone syndromes induced by breast cancer.

PURPOSE

The objective is to discover natural osteoclast inhibitor to treat osteoclastogenesis and bone destruction induced by breast cancer, and clarify the specific mechanisms.

METHODS

Recepteur d'origine Nantais (RON) protein was employed to search the natural osteoclast inhibitor for breast cancer-induced osteoclastogenesis by molecular docking, molecular dynamics simulation and cellular thermal shift assay (CETSA). In the in vitro experiment, breast cancer MDA-MB-231 cell-conditioned medium (MDA-MB-231 CM) was used to induce osteoclastogenesis in murine bone marrow-derived macrophages (BMMs), aiming to elucidate the effects and mechanisms of the natural osteoclast inhibitor. In the in vivo model, MDA-MB-231 cells was injected into the mouse tibia to evaluate the therapeutic effect of drug on breast cancer-induced bone destruction.

RESULTS

We discovered a significant increase in the expression of RON during MDA-MB-231 CM-induced osteoclast differentiation in vitro. Molecular docking analysis found that oroxylin A (OA), a flavonoid derived from the Chinese medicine Scutellaria baicalensis Georgi, showed binding ability with RON, while its impact and mechanism on breast cancer-induced osteoclastogenesis and osteolysis remains unclear. Molecular dynamics simulation and CETSA further revealed that OA bound directly to the RON protein, and it also decreased RON expression in breast cancer CM-induced osteoclastogenesis. Correspondingly, OA suppressed the MDA-MB-231 CM-induced osteoclastogenesis and bone resorption in vitro. The downstream signals of RON including Src and NFATc1, as well as the osteoclast-specific genes, were downregulated by OA. Of interesting, the suppressive effect of OA on osteoclastogenesis induced by MDA-MB-231 CM was abolished after RON was knocked down by the specific RON-siRNA, this further confirmed that OA showed inhibitory effects on osteoclasts through targeting RON. In addition, we found that OA attenuated MDA-MB-231 cell-induced osteolysis and reduced the number of osteoclasts in vivo.

CONCLUSION

Our results indicate that OA acts as a natural RON inhibitor to suppress breast cancer-induced osteoclastogenesis and osteolysis. This provides new strategy for treating breast cancer-induced bone destruction and related syndromes.

Epiberberine inhibits bone metastatic breast cancer-induced osteolysis

ETHNOPHARMACOLOGICAL RELEVANCE

The anti-tumor related diseases of Coptidis Rhizoma (Huanglian) were correlated with its traditional use of removing damp-heat, clearing internal fire, and counteracting toxicity. In the recent years, Coptidis Rhizoma and its components have drawn extensive attention toward their anti-tumor related diseases. Besides, Coptidis Rhizoma is traditionally used as an anti-inflammatory herb. Epiberberine (EPI) is a significant alkaloid isolated from Coptidis Rhizoma, and exhibits multiple pharmacological activities including anti-inflammatory. However, the effect of epiberberine on breast cancer and the inflammatory factors of metastatic breast cancer-induced osteolysis has not been demonstrated clearly.

AIM OF THE STUDY

Bone metastatic breast cancer can lead to osteolysis via inflammatory factors-induced osteoclast differentiation and function. In this study, we try to analyze the effect of epiberberine on breast cancer and the inflammatory factors of metastatic breast cancer-induced osteolysis.

METHODS

To evaluate whether epiberberine could suppress bone metastatic breast cancer-induced osteolytic damage, healthy female Balb/c mice were intratibially injected with murine triple-negative breast cancer 4T1 cells. Then, we examined the inhibitory effect and underlying mechanism of epiberberine on breast cancer-induced osteoclastogenesis in vitro. Xenograft assay was used to study the effect of epiberberine on breast cancer cells in vivo. Moreover, we also studied the inhibitory effects and underlying mechanisms of epiberberine on RANKL-induced osteoclast differentiation and function in vitro.

RESULTS

The results show that epiberberine displayed potential therapeutic effects on breast cancer-induced osteolytic damage. Besides, our results show that epiberberine inhibited breast cancer cells-induced osteoclast differentiation and function by inhibiting secreted inflammatory cytokines such as IL-8. Importantly, we found that epiberberine directly inhibited RANKL-induced differentiation and function of osteoclast without cytotoxicity. Mechanistically, epiberberine inhibited RANKL-induced osteoclastogensis via Akt/c-Fos signaling pathway. Furthermore, epiberberine combined with docetaxel effectively protected against bone loss induced by metastatic breast cancer cells.

CONCLUSIONS

Our findings suggested that epiberberine may be a promising natural compound for treating bone metastatic breast cancer-induced osteolytic damage by inhibiting IL-8 and is worthy of further exploration in preclinical and clinical trials.

The Secretome of Parental and Bone Metastatic Breast Cancer Elicits Distinct Effects in Human Osteoclast Activity after Activation of β2 Adrenergic Signaling

The sympathetic nervous system (SNS), particularly through the β2 adrenergic receptor (β2-AR), has been linked with breast cancer (BC) and the development of metastatic BC, specifically in the bone. Nevertheless, the potential clinical benefits of exploiting β2-AR antagonists as a treatment for BC and bone loss-associated symptoms remain controversial. In this work, we show that, when compared to control individuals, the epinephrine levels in a cohort of BC patients are augmented in both earlier and late stages of the disease. Furthermore, through a combination of proteomic profiling and functional in vitro studies with human osteoclasts and osteoblasts, we demonstrate that paracrine signaling from parental BC under β2-AR activation causes a robust decrease in human osteoclast differentiation and resorption activity, which is rescued in the presence of human osteoblasts. Conversely, metastatic bone tropic BC does not display this anti-osteoclastogenic effect. In conclusion, the observed changes in the proteomic profile of BC cells under β-AR activation that take place after metastatic dissemination, together with clinical data on epinephrine levels in BC patients, provided new insights on the sympathetic control of breast cancer and its implications on osteoclastic bone resorption.

Stromal Co-Cultivation for Modeling Breast Cancer Dormancy in the Bone Marrow

Cancers metastasize to the bone marrow before primary tumors can be detected. Bone marrow micrometastases are resistant to therapy, and while they are able to remain dormant for decades, they recur steadily and result in incurable metastatic disease. The bone marrow microenvironment maintains the dormancy and chemoresistance of micrometastases through interactions with multiple cell types and through structural and soluble factors. Modeling dormancy in vitro can identify the mechanisms of these interactions. Modeling also identifies mechanisms able to disrupt these interactions or define novel interactions that promote the reawakening of dormant cells. The in vitro modeling of the interactions of cancer cells with various bone marrow elements can generate hypotheses on the mechanisms that control dormancy, treatment resistance and reawakening in vivo. These hypotheses can guide in vivo murine experiments that have high probabilities of succeeding in order to verify in vitro findings while minimizing the use of animals in experiments. This review outlines the existing data on predominant stromal cell types and their use in 2D co-cultures with cancer cells.

Breast carcinomas with osteoclast-like giant cells: a comprehensive clinico-pathological and molecular portrait and evidence of RANK-L expression

Breast carcinomas (BC) with osteoclast-like giant cells (OGC) are rare. Despite their distinct stromal features, their molecular characteristics remain unknown. Here, we report comprehensive clinico-pathological and molecular findings for 27 patients diagnosed with BC-OGC at Institut Curie between 2000 and 2021. Seventeen (63%) cases were invasive carcinomas of no special type (IC NST) with OGC (OGC-IC NST), four (15%) were mixed or multifocal cases with and without OGC (OGC-Mixed), and six (22%) were metaplastic carcinomas with OGC (OGC-MC). All OGC-IC NST and OGC-Mixed cases were ER+ HER2- tumors (most being luminal A based on transcriptomic subtyping, when available), while all OGC-MC were triple-negative. The median age at diagnosis was 46, 45 and 62 years for OGC-IC NST, OGC-Mixed and OGC-MC, respectively. Three patients developed distant metastases (one OGC-IC NST, two OGC-Mixed), one of whom died of metastatic disease (OGC-Mixed), and one other patient died of locally advanced disease (OGC-MC). Histopathological evaluation comparing 13 OGC-IC NST and 19 control IC NST without OGC confirmed that OGC-IC NST showed significantly higher density of vessels (by CD34 immunohistochemistry (IHC)), iron deposits (Perls stain), and CD68 and CD163-positive cell infiltrates. Genomic findings for nine OGC-IC NST and four OGC-MC were consistent with the underlying histologic subtype, including activating alterations of the PI3K/AKT/mTOR pathway in 7/13 cases. Using RNA-seq data, differential gene expression analysis between OGC-IC NST (n = 7) and control IC NST without OGC (n = 7) revealed significant overexpression of TNFSF11 (RANK-L), TNFRSF11A (RANK), CSF1 (M-CSF), CSF1R, and genes encoding osteoclastic enzymes (MMP9, ACP5, CTSK, CTSB) in OGC-IC NST, while OPG (osteoprotegerin) was underexpressed. We also confirmed for the first time RANK-L expression in BC with OGC by IHC (seen in 15 out of 16 cases, and only in 2 of 16 controls without OGC). These findings could offer a rationale for further investigating RANK-L as a therapeutic target in BC with OGC.

Regulation of TNF-Induced Osteoclast Differentiation

Increased osteoclast (OC) differentiation and activity is the critical event that results in bone loss and joint destruction in common pathological bone conditions, such as osteoporosis and rheumatoid arthritis (RA). RANKL and its decoy receptor, osteoprotegerin (OPG), control OC differentiation and activity. However, there is a specific concern of a rebound effect of denosumab discontinuation in treating osteoporosis. TNFα can induce OC differentiation that is independent of the RANKL/RANK system. In this review, we discuss the factors that negatively and positively regulate TNFα induction of OC formation, and the mechanisms involved to inform the design of new anti-resorptive agents for the treatment of bone conditions with enhanced OC formation. Similar to, and being independent of, RANKL, TNFα recruits TNF receptor-associated factors (TRAFs) to sequentially activate transcriptional factors NF-κB p50 and p52, followed by c-Fos, and then NFATc1 to induce OC differentiation. However, induction of OC formation by TNFα alone is very limited, since it also induces many inhibitory proteins, such as TRAF3, p100, IRF8, and RBP-j. TNFα induction of OC differentiation is, however, versatile, and Interleukin-1 or TGFβ1 can enhance TNFα-induced OC formation through a mechanism which is independent of RANKL, TRAF6, and/or NF-κB. However, TNFα polarized macrophages also produce anabolic factors, including insulin such as 6 peptide and Jagged1, to slow down bone loss in the pathological conditions. Thus, the development of novel approaches targeting TNFα signaling should focus on its downstream molecules that do not affect its anabolic effect.

Osteoclast Fusion: Physiological Regulation of Multinucleation through Heterogeneity-Potential Implications for Drug Sensitivity

Classically, osteoclast fusion consists of four basic steps: (1) attraction/migration, (2) recognition, (3) cell-cell adhesion, and (4) membrane fusion. In theory, this sounds like a straightforward simple linear process. However, it is not. Osteoclast fusion has to take place in a well-coordinated manner-something that is not simple. In vivo, the complex regulation of osteoclast formation takes place within the bone marrow-in time and space. The present review will focus on considering osteoclast fusion in the context of physiology and pathology. Special attention is given to: (1) regulation of osteoclast fusion in vivo, (2) heterogeneity of osteoclast fusion partners, (3) regulation of multi-nucleation, (4) implications for physiology and pathology, and (5) implications for drug sensitivity and side effects. The review will emphasize that more attention should be given to the human in vivo reality when interpreting the impact of in vitro and animal studies. This should be done in order to improve our understanding of human physiology and pathology, as well as to improve anti-resorptive treatment and reduce side effects.

CXCR2: A Novel Mediator of Mammary Tumor Bone Metastasis

Most breast cancer patients die due to bone metastasis. Although metastasis accounts for 5% of the breast cancer cases, it is responsible for most of the deaths. Sometimes even before the detection of a primary tumor, most of the patients have bone and lymph node metastasis. Moreover, at the time of death, breast cancer patients have the bulk of the tumor burden in their bones. Therapy options are available for the treatment of primary tumors, but there are minimal options for treating breast cancer patients who have bone metastasis. C-X-C motif chemokine receptor type 2 (CXCR2) receptor-mediated signaling has been shown to play a critical role during bone-related inflammations and its ligands C-X-C motif chemokine ligand 6 (CXCL6) and 8 (CXCL8) aid in the resorption of bone during bone metastasis. In this study, we tested the hypothesis that CXCR2 contributes to mammary tumor-induced osteolysis and bone metastasis. In the present study, we examined the role of both tumor cell-derived and host-derived CXCR2 in influencing mammary tumor cell bone metastasis. For understanding the role of tumor cell-derived CXCR2, we utilized Cl66 CXCR2 knockdown (Cl66-shCXCR2) and Cl66-Control cells (Cl66-Control) and observed a significant decrease in tumor growth and tumor-induced osteolysis in Cl66-shCXCR2 cells in comparison with the Cl66-Control cells. Next, for understanding the role of host-derived CXCR2, we utilized mice with genomic knockdown of CXCR2 (Cxcr2^-/-) and injected Cl66-Luciferase (Cl66-Luc) or 4T1-Luciferase (4T1-Luc) cells. We observed decreased bone destruction and metastasis in the bone of Cxcr2^-/- mice. Our data suggest the importance of both tumor cell- and host-derived CXCR2 signaling in the bone metastasis of breast cancer cells.

Hallmarks of Bone Metastasis

Breast cancer bone metastasis develops as the result of a series of complex interactions between tumor cells, bone marrow cells, and resident bone cells. The net effect of these interactions are the disruption of normal bone homeostasis, often with significantly increased osteoclast and osteoblast activity, which has provided a rational target for controlling tumor progression, with little or no emphasis on tumor eradication. Indeed, the clinical course of metastatic breast cancer is relatively long, with patients likely to experience sequential skeletal-related events (SREs), often over lengthy periods of time, even up to decades. These SREs include bone pain, fractures, and spinal cord compression, all of which may profoundly impair a patient's quality-of-life. Our understanding of the contributions of the host bone and bone marrow cells to the control of tumor progression has grown over the years, yet the focus of virtually all available treatments remains on the control of resident bone cells, primarily osteoclasts. In this perspective, our focus is to move away from the current emphasis on the control of bone cells and focus our attention on the hallmarks of bone metastatic tumor cells and how these differ from primary tumor cells and normal host cells. In our opinion, there remains a largely unmet medical need to develop and utilize therapies that impede metastatic tumor cells while sparing normal host bone and bone marrow cells. This perspective examines the impact of metastatic tumor cells on the bone microenvironment and proposes potential new directions for uncovering the important mechanisms driving metastatic progression in bone based on the hallmarks of bone metastasis.

Non-Canonical (RANKL-Independent) Pathways of Osteoclast Differentiation and Their Role in Musculoskeletal Diseases

Osteoclasts are multinucleated cells derived from mononuclear phagocyte precursors (monocytes, macrophages); in the canonical pathway of osteoclastogenesis, these cells fuse and differentiate to form specialised bone-resorbing osteoclasts in the presence of receptor activator for nuclear factor kappa B ligand (RANKL). Non-canonical pathways of osteoclastogenesis have been described in which several cytokines and growth factors are able to substitute for RANKL. These humoral factors can generally be divided into those which, like RANKL, are tumour necrosis family (TNF) superfamily members and those which are not; the former include TNFα lymphotoxin exhibiting inducible expression and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes (LIGHT), a proliferation inducing ligand (APRIL) and B cell activating factor (BAFF); the latter include transforming growth factor beta (TGF-β), interleukin-6 (IL-6), IL-8, IL-11, nerve growth factor (NGF), insulin-like growth factor-I (IGF-I) and IGF-II. This review summarises the evidence for these RANKL substitutes in inducing osteoclast differentiation from tissue-derived and circulating mononuclear phagocytes. It also assesses the role these factors are likely to play in promoting the pathological bone resorption seen in many inflammatory and neoplastic lesions of bone and joint including rheumatoid arthritis, aseptic implant loosening and primary and secondary tumours of bone.

The induction of CXCR4 expression in human osteoblast-like cells (MG63) by CoCr particles is regulated by the PLC-DAG-PKC pathway

BACKGROUND

Osteolysis which leads to aseptic loosening of implants is a fundamental problem in joint replacement surgery (arthroplasty) and the leading cause for implant failure and revision surgery. Metal (CoCr) particles separated from implants by wear cause osteolysis and the failure of orthopedic implants, but the molecular mechanism is not clear. The chemokine receptor CXCR4 has been shown to play a pivotal role in periprosthetic osteolysis. The aim of this study was to determine which signal transduction pathway (PLC-DAG-PKC or MAPK/ERK) induces CXCR4 expression in osteoblast-like cells (MG63) cells.

METHODS

MG63 and Jurkat cells were stimulated with different amounts of particles (10⁷ , 10⁶ , and 10⁵ ) for different time periods (30 min to 24 h), in the presence and absence of specific inhibitors (chelerythrine for the PLC-DAG-PKC pathway and PD98059 for the MAPK/ERK pathway). The expression of CXCR4-specific mRNA was determined by real-time polymerase chain reaction (PCR), and the PKC activity was measured by Western Blot using an antibody specific for PKC-related phosphorylation.

RESULTS

Real-time PCR data showed that CXCR4 mRNA expression in MG63 cells induced by CoCr particles was significantly diminished by the PKC-specific inhibitor chelerythrine. This effect was not observed with the MAPK/ERK inhibitor PD98059. The involvement of PKC was also confirmed by an intensified phosphorylation pattern after stimulation with CoCr particles. In Jurkat cells, none of the inhibitors exhibited any effect.

CONCLUSION

The induction of CXCR4-specific mRNA expression in MG63 cells after stimulation with CoCr particles is regulated by the PLC-DAG-PKC pathway and not by the MAPK/ERK pathway. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2326-2332, 2017.

Dendritic and mast cell involvement in the inflammatory response to primary malignant bone tumours

Background

A chronic inflammatory cell infiltrate is commonly seen in response to primary malignant tumours of bone. This is known to contain tumour-associated macrophages (TAMs) and lymphocytes; dendritic cells (DCs) and mast cells (MCs) have also been identified but whether these and other inflammatory cells are seen commonly in specific types of bone sarcoma is uncertain.

Methods

In this study we determined the nature of the inflammatory cell infiltrate in 56 primary bone sarcomas. Immunohistochemistry using monoclonal antibodies was employed to assess semiquantitatively CD45+ leukocyte infiltration and the extent of the DC, MC, TAM and T and B lymphocyte infiltrate.

Results

The extent of the inflammatory infiltrate in individual sarcomas was very variable. A moderate or heavy leukocyte infiltrate was more commonly seen in conventional high-grade osteosarcoma, undifferentiated pleomorphic sarcoma and giant cell tumour of bone (GCTB) than in Ewing sarcoma, chordoma and chondrosarcoma. CD14+/CD68+ TAMs and CD3+ T lymphocytes were the major components of the inflammatory cell response but (DC-SIGN/CD11c+) DCs were also commonly noted when there was a significant TAM and T lymphocyte infiltrate. MCs were identified mainly at the periphery of sarcomas, including the osteolytic tumour-bone interface.

Discussion

Our findings indicate that, although variable, some malignant bone tumours (e.g. osteosarcoma, GCTB) are more commonly associated with a pronounced inflammatory cell infiltrate than others (e.g. chondrosarcoma. Ewing sarcoma); the infiltrate is composed mainly of TAMs but includes a significant DC, T lymphocyte and MC infiltrate.

Conclusion

Tumours that contain a heavy inflammatory cell response, which includes DCs, TAMs and T lymphocytes, may be more amenable to immunomodulatory therapy. MCs are present mainly at the tumour edge and are likely to contribute to osteolysis and tumour invasion.

FTY-720P Suppresses Osteoclast Formation by Regulating Expression of Interleukin-6 (IL-6), Interleukin-4 (IL-4), and Matrix Metalloproteinase 2 (MMP-2)

Background

Osteoclast formation is closely related to the immune system. FTY720, a new immunosuppressive agent, has some functions in immune regulation. Its main active ingredients become FTY-720P in vivo by phosphorylation modification. The objective of this study was to determine the effects of FTY-720 with various concentrations on osteoclasts in vitro.

Material/Methods

RAW264.7 cells and bone marrow-derived mononuclear phagocytes (BMMs) were treated with RANKL to obtain osteoclasts in vitro. To investigate the role of FTY-720 in osteoclast formation, trap enzyme staining was performed and the number of osteoclasts was counted. Bone slices were stained with methylene blue, we counted the number of lacunae after bone slices were placed into dishes together with osteoclasts, and we observed the effect and function of FTY-720 in osteoclasts induced by RAW264.7 cells and BMMs. Then, we used a protein array kit to explore the effects of FTY-720P on osteoclasts.

Results

The results of enzyme trap staining and F-actin staining experiments show that, with the increasing concentration of FTY-720P, the number of osteoclast induced by RAW264.7 cells and BMMs gradually decreased (P<0.05), especially when the FTY-720P concentration reached 1000 ng/ml, and the number of osteoclasts formed was the lowest (P<0.05). With bone lacuna toluidine blue staining, the results also show that, with the increasing concentration of FTY-720P, the number of bone lacuna gradually decreased (P<0.05), and the number of lacunae is lowest when the concentration reached 800 ng/ml. Finally, protein array results showed that IL-4, IL-6, IL-12, MMP-2, VEGF-C, GFR, basic FGF, MIP-2, and insulin proteins were regulated after FTY-720P treatment.

Conclusions

FTY-720P can suppress osteoclast formation and function, and FTY-720P induces a series of cytokine changes.

TRAIL-based therapy in pediatric bone tumors: how to overcome resistance

Osteosarcoma and Ewing's sarcoma, the two most frequent malignant primary tumors preferentially arise in children and young adults, and have a poor prognosis. TRAIL represents a promising therapeutic approach for most cancers but in the case of primary bone tumors, osteosarcoma cell lines are highly resistant to this pro-apoptotic cytokine. In addition, another signaling pathway mediating cell proliferation and migration may be even activated in this subset of resistant cells leading to protumoral effect. Therapeutic perspectives are linked to possibility to overcome TRAIL resistance by combining other drugs with TRAIL or death receptors agonistic antibodies. We hypothesized that the bone microenvironment may provide a favorable niche for TRAIL resistance that might be targeted by new resensitizing agents.

Everolimus restrains the paracrine pro-osteoclast activity of breast cancer cells

Background

Breast cancer (BC) cells secrete soluble factors that accelerate osteoclast (OC) differentiation, leading to the formation of osteolytic bone metastases. In the BOLERO-2 trial, BC patients with bone involvement who received Everolimus had a delayed tumor progression in the skeleton as a result of direct OC suppression through the inhibition of mTOR, in addition to the general suppressor effect on the cancer cells. Here, we explored the effect of Everolimus, as mTOR inhibitor, on the pro-OC paracrine activity of BC cells.

Methods

Both MDA-MB-231 and MCF-7 BC cell lines were incubated with sub-lethal amounts of Everolimus, and their conditioned supernatants were assessed for their capacity to differentiate OCs from PBMC from healthy donors, as well as to interfere with their bone resorbing activity shown on calcium phosphate slices. We also measured the mRNA levels of major pro-OC factors in Everolimus-treated BC cells and their secreted levels by ELISA, and evaluated by immunoblotting the phosphorylation of transcription factors enrolled by pathways cooperating with the mTOR inhibition. Finally, the in vivo pro-OC activity of these cells was assessed in SCID mice after intra-tibial injections.

Results

We found that Everolimus significantly inhibited the differentiation of OCs and their in vitro bone-resorbing activity, and also found decreases of both mRNA and secreted pro-OC factors such as M-CSF, IL-6, and IL-1β, whose lower ELISA levels paralleled the defective phosphorylation of NFkB pathway effectors. Moreover, when intra-tibially injected in SCID mice, Everolimus-treated BC cells produced smaller bone metastases than the untreated cells.

Conclusions

mTOR inhibition in BC cells leads to a suppression of their paracrine pro-OC activity by interfering with the NFkB pathway; this effect may also account for the delayed progression of bone metastatic disease observed in the BOLERO-2 trial.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1717-8) contains supplementary material, which is available to authorized users.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

Particle characterisation and cytokine expression in failed small-diameter metal-on-metal total hip arthroplasties

The peri-prosthetic tissue response to wear debris is complex and influenced by various factors including the size, area and number of particles. We hypothesised that the ‘biologically active area’ of all metal wear particles may predict the type of peri-prosthetic tissue response.

Peri-prosthetic tissue was sampled from 21 patients undergoing revision of a small diameter metal-on-metal (MoM) total hip arthroplasty (THA) for aseptic loosening. An enzymatic protocol was used for tissue digestion and scanning electron microscope was used to characterise particles. Equivalent circle diameters and particle areas were calculated. Histomorphometric analyses were performed on all tissue specimens. Aspirates of synovial fluid were collected for analysis of the cytokine profile analysis, and compared with a control group of patients undergoing primary THA (n = 11) and revision of a failed ceramic-on-polyethylene arthroplasty (n = 6).

The overall distribution of the size and area of the particles in both lymphocyte and non-lymphocyte-dominated responses were similar; however, the subgroup with lymphocyte-dominated peri-prosthetic tissue responses had a significantly larger total number of particles.

14 cytokines (interleukin (IL)-1ß, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17, interferon (IFN)-γ, and IFN-gamma-inducible protein 10), chemokines (macrophage inflammatory protein (MIP)-1α and MIP-1ß), and growth factors (granulocyte macrophage colony stimulating factor (GM-CSF) and platelet derived growth factor) were detected at significantly higher levels in patients with metal wear debris compared with the control group.

Significantly higher levels for IL-1ß, IL-5, IL-10 and GM-CSF were found in the subgroup of tissues from failed MoM THAs with a lymphocyte-dominated peri-prosthetic response compared with those without this response.

These results suggest that the ‘biologically active area’ predicts the type of peri-prosthetic tissue response. The cytokines IL-1ß, IL-5, IL-10, and GM-CSF are associated with lymphocyte-dominated tissue responses from failed small-diameter MoM THA.

Cite this article: Bone Joint J 2015;97-B:917–23.

The association between RANKL and Osteoprotegerin gene polymorphisms with breast cancer

Breast cancer is the most common cause of cancer death among women (522,000 deaths in 2012). Imbalance between RANKL and OPG is observed in many cancers, including breast cancer. Consequently, SNPs in the genes of RANKL and OPG may be involved in breast cancer development. This study included 276 subjects. Group I (n = 100) healthy females as a control group, group II (n = 96) breast cancer patients without bone metastases, and group III (n = 80) breast cancer patients with bone metastases. RANKL rs9533156, OPG rs2073618, and OPG rs2073617 SNPs and their serum protein levels were studied for a possible association with breast cancer development. The allele frequency [(OR: 4.832 CI 2.18-10.71, P = 0.001) and genotype distribution (P = 0.001)] of OPG SNP rs2073618 showed a highly significant difference between breast cancer patients and healthy controls. The allele C is more common in breast cancer patients. The allele frequency [(OR: 0.451 CI 0.232-0.879, P = 0.018) and genotype distribution (P = 0.003)] of RANKL SNP rs9533156 differed significantly between breast cancer patients and healthy controls. The allele T is more common in breast cancer patients. The allele frequency [(OR: 0.36 CI 0.184-0.705, P = 0.002) and genotype distribution (P = 0.011)] of OPG SNP rs2073617 differed significantly between breast cancer patients and healthy controls. The allele T is more common in breast cancer patients. The C allele of OPG SNP rs2073618 may be associated with breast cancer development. No association was found between any of the SNPs and the serum protein levels of RANKL and OPG.

Metallic debris from metal-on-metal total hip arthroplasty regulates periprosthetic tissues

The era of metal-on-metal (MoM) total hip arthroplasty has left the orthopaedic community with valuable insights and lessons on periprosthetic tissue reactions to metallic debris. Various terms have been used to describe the tissue reactions. Sometimes the nomenclature can be confusing. We present a review of the concepts introduced by Willert and Semlitsch in 1977, along with further developments made in the understanding of periprosthetic tissue reactions to metallic debris. We propose that periprosthetic tissue reactions be thought of as (1) gross (metallosis, necrosis, cyst formation and pseudotumour); (2) histological (macrophage-dominated, lymphocyte-dominated or mixed); and (3) molecular (expression of inflammatory mediators and cytokines such as interleukin-6 and tumor necrosis factor-alpha). Taper corrosion and modularity are discussed, along with future research directions to elucidate the antigen-presenting pathways and material-specific biomarkers which may allow early detection and intervention in a patient with adverse periprosthetic tissue reactions to metal wear debris.

Metallic wear debris may regulate CXCR4 expression in vitro and in vivo

CXCR4, the chemokine receptor for CXCL12, also known as SDF-1 (stromal cell derived factor-1), has been shown to play a pivotal role in bone metastasis, inflammatory, and autoimmune conditions but has not been investigated in periprosthetic osteolysis. We co-cultured osteoblast-like cells with increasing concentrations of metallic (Co-35Ni-20Cr-10Mo and Co-28Cr-6Mo) and Co-ions simulating wear debris. Real-time polymerase chain reaction (RT-PCR) and Western blotting were used to quantify gene and protein expression of CXCR4. The expression of tumor necrosis factor-alpha (TNF-α) and the effects of AMD3100 (bicyclam) on both CXCR4 and TNF-α expression among these cells was investigated. RT-PCR showed an increase in CXCR4 mRNA (7.5-fold for MG63 and 4.0-fold for SaOs-2 cells) among cells co-cultured with metal alloy particles. Western blotting showed a time-dependent increase in protein expression of CXCR4. The attempted blockade of CXCR4 by its known competitive receptor agonist AMD3100 led to a significant inhibition TNF-α mRNA expression. Immunohistochemistry showed CXCR4 positivity among patients with failed metal-on-metal hip replacements and radiographic evidence of osteolysis. Our data collectively suggest that the CXCR4 chemokine is upregulated in a dose- and time-dependent manner in the presence of metallic wear debris.

MAPK11 in breast cancer cells enhances osteoclastogenesis and bone resorption

Breast cancer cells frequently metastasize to bone and induce osteolytic bone destruction in patients. These metastases cause severe bone pain, high risk of fractures and hypercalcemia, and are essentially incurable and fatal. Recent studies show that breast cancer cells in bone activate osteoclastogenesis and bone resorption. However the underlying mechanism is poorly understood. This study shows that the p38 MAPK (p38) isoform MAPK11 (p38β) is expressed in breast cancer cells. By using specific small hairpin RNAs for MAPK11, we demonstrated that p38β-mediated p38 activity in breast cancer cells is responsible for breast cancer-induced osteolytic bone destruction. The addition of conditioned media from breast cancer cell lines MDA-MB-231 and MDA-MB-468, which have high expression of p38β, induced osteoclast differentiation and bone resorption. In contrast, knockdown of p38β in breast cancer cells reduced osteoclast differentiation in vitro and reduced bone destruction in severe combined immunodeficiency (SCID) mouse models. The knockdown of p38β did not affect tumor growth or survival or the ability of cancer cells to home to bone. Furthermore, our results showed that p38β upregulated the expression and secretion of monocyte chemotactic protein-1 (MCP-1) in breast cancer cells, and upregulated MCP-1 activates osteoclast differentiation and activity. This study elucidates a novel molecular mechanism of breast cancer cell-induced osteolytic bone destruction. This study also indicates that targeting breast cancer cell p38β and its product MCP-1 may be a viable approach to treat or prevent bone destruction in patients with bone-metastatic breast cancer.

Preclinical evaluation of zoledronate using an in vitro mimetic cellular model for breast cancer metastatic bone disease

BACKGROUND

The interactions between metastatic breast cancer cells and host cells of osteoclastic lineage in bone microenvironment are essential for osteolysis. In vitro studies to evaluate pharmacological agents are mainly limited to their direct effects on cell lines. To mimic the communication between breast cancer cells and human osteoclasts, a simple and reproducible cellular model was established to evaluate the effects of zoledronate (zoledronic acid, ZOL), a bisphosphonate which exerts antiresorptive properties.

METHODS

Human precursor osteoclasts were cultured on bone-like surfaces in the presence of stimuli (sRANKL, M-CSF) to ensure their activation. Furthermore, immature as well as activated osteoclasts were co-cultured with MDA-MB-231 breast cancer cells. TRAP5b and type I collagen N-terminal telopeptide (NTx) were used as markers. Osteoclasts' adhesion to bone surface and subsequent bone breakdown were evaluated by studying the expression of cell surface receptors and certain functional matrix macromolecules in the presence of ZOL.

RESULTS

ZOL significantly suppresses the precursor osteoclast maturation, even when the activation stimuli (sRANKL and M-SCF) are present. Moreover, it significantly decreases bone osteolysis and activity of MMPs as well as precursor osteoclast maturation by breast cancer cells. Additionally, ZOL inhibits the osteolytic activity of mature osteoclasts and the expression of integrin β3, matrix metalloproteinases and cathepsin K, all implicated in adhesion and bone resorption.

CONCLUSIONS

ZOL exhibits a beneficial inhibitory effect by restricting activation of osteoclasts, bone particle decomposition and the MMP-related breast cancer osteolysis.

GENERAL SIGNIFICANCE

The proposed cellular model can be reliably used for enhancing preclinical evaluation of pharmacological agents in metastatic bone disease.

Variability of the paracrine-induced osteoclastogenesis by human breast cancer cell lines

Breast cancer frequently metastasizes to the bone, often leading to the formation of osteolytic lesions. This work compares the paracrine-induced osteoclastogenesis mediated by four human breast cancer cell lines, the estrogen-receptor positive T47D and MCF-7 and the estrogen-negative SK-BR-3 and Hs-578T cell lines. Human osteoclast precursor cells were cultured in the presence of conditioned media from the breast cancer cell lines (10% and 20%), collected at different culture periods (48 h, 7 days, and 14 days). Cultures performed in the absence or the presence of M-CSF and RANKL served as negative and positive control, respectively. Results showed that the cell lines differentially expressed several osteoclastogenic genes. All cell lines exhibited a significant osteoclastogenic potential, evidenced by a high TRAP activity and number of osteoclastic cells, expression of several osteoclast-related genes, and, particularly, a high calcium phosphate resorption activity. Differences among the osteoclastogenic potential of the cell lines were noted. T47D and MCF-7 cell lines displayed the highest and the lowest osteoclastogenic response, respectively. Despite the variability observed, MEK and NF-κB signaling pathways, and, at a lesser extent, PGE2 production, seemed to have a central role on the observed osteoclastogenic response. In conclusion, the tested breast cancer cell lines exhibited a high osteoclastogenic potential, although with some variability on the cell response profile, a factor to be considered in the development of new therapeutic approaches for breast cancer-induced bone metastasis.

Normal breast tissue of obese women is enriched for macrophage markers and macrophage-associated gene expression

Activation of inflammatory pathways is one plausible mechanism underlying the association between obesity and increased breast cancer risk. However, macrophage infiltration and local biomarkers of inflammation in breast adipose tissue have seldom been studied in association with obesity. Gene expression profiles of normal breast tissue from reduction mammoplasty patients were evaluated by whole genome microarrays to identify patterns associated with obesity status (normal-weight, body mass index (BMI) <25; overweight, BMI 25-29.9; obese, BMI ≥30). The presence of macrophage-enriched inflammatory loci with immunopositivity for CD68 protein was evaluated by immunohistochemistry (IHC). After adjusting for confounding by age, 760 genes were differentially expressed (203 up and 557 down; FDR = 0.026) between normal-weight and obese women. Gene ontology analysis suggested significant enrichment for pathways involving IL-6, IL-8, CCR5 signaling in macrophages and RXRα and PPARα activation, consistent with a pro-inflammatory state and suggestive of macrophage infiltration. Gene set enrichment analysis also demonstrated that the genomic signatures of monocytes and macrophages were over-represented in the obese group with FDR of 0.08 and 0.13, respectively. Increased macrophage infiltration was confirmed by IHC, which showed that the breast adipose tissue of obese women had higher average macrophage counts (mean = 8.96 vs. 3.56 in normal-weight women) and inflammatory foci counts (mean = 4.91 vs. 2.67 in normal-weight women). Obesity is associated with local inflammation and macrophage infiltration in normal human breast adipose tissues. Given the role of macrophages in carcinogenesis, these findings have important implications for breast cancer etiology and progression.

The small molecule harmine regulates NFATc1 and Id2 expression in osteoclast progenitor cells

Small molecule compounds that potently affect osteoclastogenesis could be useful as chemical probes for elucidating the mechanisms of various biological phenomena and as effective therapeutic strategies against bone resorption. An osteoclast progenitor cell-based high-throughput screening system was designed to target activation of NFAT, which is a key event for osteoclastogenesis. Orphan ligand library screening using this system identified the β-carboline derivative harmine, which is a highly potent inhibitor of dual-specificity tyrosine-phosphorylation regulated kinase 1A (DYRK1A), to be an NFAT regulator in osteoclasts. RAW264.7 cells highly expressed DYRK1A protein, and in vitro phosphorylation assay demonstrated that harmine directly inhibited the DYRK1A-mediated phosphorylation (in-activation) of NFATc1. Harmine promoted the dephosphorylation (activation) of NFATc1 in RAW264.7 cells within 24h, and it significantly increased the expression of NFATc1 in RAW264.7 cells and mouse primary bone marrow macrophages (BMMs) both in the presence and absence of RANKL stimulation. Although harmine promoted NFATc1 expression and stimulated target genes for osteoclastogenesis, cell-cell fusion and the formation of TRAP-positive multinucleated osteoclasts from RAW264.7 cells and BMMs was significantly inhibited by harmine treatment. Meanwhile, harmine remarkably promoted the expression of inhibitor of DNA binding/differentiation-2 (Id2), which is a negative regulator for osteoclastogenesis, in RAW264.7 cells and BMMs. An Id2-null-mutant showed slightly increased osteoclast formation from BMMs, and the harmine-mediated inhibition of osteoclast formation was abolished in the BMMs of Id2-null-mutant mice. These results suggest that harmine is a potent activator of NFATc1 that interferes with the function of DYRK1A in osteoclast precursors and also up-regulates Id2 protein, which may dominantly inhibit expression pathways associated with cell-cell fusion, thereby leading to the disruption of the fusion events mediating osteoclastogenesis. The small molecule harmine is therefore expected to provide an experimental tool for investigating signaling cascades in osteoclastogenesis, especially those centered on DYRK1A-mediated NFATc1 and Id2 regulation.

Bone metastasis: mechanisms and therapeutic opportunities

The skeleton is one of the most common sites for metastatic cancer, and tumors arising from the breast or prostate possess an increased propensity to spread to this site. The growth of disseminated tumor cells in the skeleton requires tumor cells to inhabit the bone marrow, from which they stimulate local bone cell activity. Crosstalk between tumor cells and resident bone and bone marrow cells disrupts normal bone homeostasis, which leads to tumor growth in bone. The metastatic tumor cells have the ability to elicit responses that stimulate bone resorption, bone formation or both. The net result of these activities is profound skeletal destruction that can have dire consequences for patients. The molecular mechanisms that underlie these painful and often incurable consequences of tumor metastasis to bone are beginning to be recognized, and they represent promising new molecular targets for therapy.

Expression pattern of receptor activator of NFκB (RANK) in a series of primary solid tumors and related bone metastases

Receptor activator of NFκB ligand (RANKL), RANK, and osteoprotegerin (OPG) represent the key regulators of bone metabolism both in normal and pathological conditions, including bone metastases. To our knowledge, no previous studies investigated and compared RANK expression in primary tumors and in bone metastases from the same patient. We retrospectively examined RANK expression by immunohistochemistry in 74 bone metastases tissues from solid tumors, mostly breast, colorectal, renal, lung, and prostate cancer. For 40 cases, tissue from the corresponding primary tumor was also analyzed. Sixty-six (89%) of the 74 bone metastases were RANK-positive and, among these, 40 (59.5%) showed more than 50% of positive tumor cells. The median percentage of RANK-positive cells was 60% in primary tumors and metastases, without any statistically significant difference between the two groups (P=0.194). The same percentage was obtained by considering only cases with availability of samples both from primary and metastasis. Our study shows that RANK is expressed by solid tumors, with high concordance between bone metastasis and corresponding primary tumor. These data highlight the central role of RANK/RANKL/OPG pathway as potential therapeutic target not only in bone metastasis management, but also in the adjuvant setting.

Tumor-supportive and osteoclastogenic changes induced by breast cancer-derived factors are reversed by inhibition of {gamma}-secretase

During breast cancer metastasis to bone, tumor cells home to bone marrow, likely targeting the stem cell niche, and stimulate osteoclasts, which mediate osteolysis required for tumor expansion. Although osteoblasts contribute to the regulation of the hematopoietic stem cell niche and control osteoclastogenesis through production of proresorptive cytokine RANKL (receptor activator of NF-κB ligand), their role in cancer metastases to bone is not fully understood. C57BL/6J mouse bone marrow cells were treated for 3–12 days with ascorbic acid (50 μg/ml) in the presence or absence of 10% medium conditioned by breast carcinoma cells MDA-MB-231, 4T1, or MCF7. Treatment with cancer-derived factors resulted in a sustained 40–60% decrease in osteoblast differentiation markers, compared with treatment with ascorbic acid alone, and induced an osteoclastogenic change in the RANKL/osteoprotegerin ratio. Importantly, exposure of bone cells to breast cancer-derived factors stimulated the subsequent attachment of cancer cells to immature osteoblasts. Inhibition of γ-secretase using pharmacological inhibitors DAPT and Compound E completely reversed cancer-induced osteoclastogenesis as well as cancer-induced enhancement of cancer cell attachment, identifying γ-secretase activity as a key mediator of these effects. Thus, we have uncovered osteoblasts as critical intermediary of premetastatic signaling by breast cancer cells and pinpointed γ-secretase as a robust target for developing therapeutics potentially capable of reducing both homing and progression of cancer metastases to bone.

Soluble TRAIL could enhance bone destruction acting on Rank-ligand in estrogen-independent human breast cancer cell line MDA-MB-231

The development and spread of tumors is associated with the ability of malignant cells to avoid detection and subsequent elimination by the immune system, to grow in non-native sites and to avoid programmed or induced cell death. In addition to the well-described role of osteoprotegerin in the regulation of bone turnover, there is an emerging evidence that osteoprotegerin may have an additional function due to its ability to bind and inhibit the members of the tumor necrosis factor (TNF)-superfamily, such as TNF-alpha and TNF-related apoptosis inducing ligand (TRAIL). We have shown that the breast cancer cell line MDA-MB-231 produces a sufficient amount of osteoprotegerin to bind TRAIL, resulting in an upregulation of receptor activator factor kappa B ligand (RANKL) expression. In conclusion, the presence of osteoprotegerin, as secreted by this cell line, acting as a paracrine factor, could affect breast cancer RANKL production inducing an enhancement of osteolysis and the perpetuation of a vicious cycle. A better understanding of the complex tumor cell-host cell interactions in the bone microenvironment, and of the autocrine and paracrine effects of the secreted (from tumor cells) and released (from bone matrix) factors may facilitate development of effective strategies to inhibit disease progression.

Breast adenocarcinoma MCF-7 cell line induces spontaneous osteoclastogenesis via a RANK-ligand-dependent pathway

The metastasis of breast cancer to the skeleton is a serious clinical problem resulting in hypercalcemia, bone fragility and insurmountable pain. The invasion of bony tissue by neoplastic cells usually very rapidly affects the balance between bone apposition and bone resorption. In order to elucidate a mechanism for cancer-induced osteoclastogenesis, cells from a human breast cancer line, MCF-7, were directly co-cultured with murine monocytes RAW 264.7 type CRL 2278. Compared with controls, co-culture of MCF-7 induced differentiation of multinucleated cells by membrane-bound and soluble receptor activator of NF-kB ligand (RANKL) as quantified by ELISA, Western blot analysis, transmission electron microscopy (TEM), and immunocytochemistry. The aim of this study was to determine an in vitro model system of MCF-7 human breast cancer cells grown together with monocytes to show that expression of RANKL promotes osteoclastogenesis, which may indicate a mechanism for the development of osteolytic lesions in breast cancer bone metastasis.