Production and regulation of interleukin-11 by breast cancer cells

The IL6-like Cytokine Family: Role and Biomarker Potential in Breast Cancer

IL6-like cytokines are a family of regulators with a complex, pleiotropic role in both the healthy organism, where they regulate immunity and homeostasis, and in different diseases, including cancer. Here we summarise how these cytokines exert their effect through the shared signal transducer IL6ST (gp130) and we review the extensive evidence on the role that different members of this family play in breast cancer. Additionally, we discuss how the different cytokines, their related receptors and downstream effectors, as well as specific polymorphisms in these molecules, can serve as predictive or prognostic biomarkers with the potential for clinical application in breast cancer. Lastly, we also discuss how our increasing understanding of this complex signalling axis presents promising opportunities for the development or repurposing of therapeutic strategies against cancer and, specifically, breast neoplasms.

Interleukin 11 (IL-11): Role(s) in Breast Cancer Bone Metastases

Bone metastases represent the main problem related to the progression of breast cancer, as they are the main cause of death for these patients. Unfortunately, to date, bone metastases are incurable and represent the main challenge for the researcher. Chemokines and cytokines affect different stages of the metastatic process, and in bone metastases, interleukin (IL) -6, IL-8, IL-1β, and IL-11 participate in the interaction between cancer cells and bone cells. This review focuses on IL-11, a pleiotropic cytokine that, in addition to its well-known effects on several tissues, also mediates certain signals in cancer cells. In particular, as IL-11 works on bone remodeling, it plays a relevant role in the osteolytic vicious cycle of bone resorption and tumour growth, which characterizes bone metastasis. IL-11 appears as a candidate for anti-metastatic therapy. Even if different therapeutic approaches have considered IL-11 and the downstream-activated gp130 signaling pathways activated downstream of gp130, further studies are needed to decipher the contribution of the different cytokines and their mechanisms of action in breast cancer progression to define therapeutic strategies.

Interleukin-11-expressing fibroblasts have a unique gene signature correlated with poor prognosis of colorectal cancer

Interleukin (IL)-11 is a member of the IL-6 family of cytokines and is involved in multiple cellular responses, including tumor development. However, the origin and functions of IL-11-producing (IL-11⁺) cells are not fully understood. To characterize IL-11⁺ cells in vivo, we generate Il11 reporter mice. IL-11⁺ cells appear in the colon in murine tumor and acute colitis models. Il11ra1 or Il11 deletion attenuates the development of colitis-associated colorectal cancer. IL-11⁺ cells express fibroblast markers and genes associated with cell proliferation and tissue repair. IL-11 induces the activation of colonic fibroblasts and epithelial cells through phosphorylation of STAT3. Human cancer database analysis reveals that the expression of genes enriched in IL-11⁺ fibroblasts is elevated in human colorectal cancer and correlated with reduced recurrence-free survival. IL-11⁺ fibroblasts activate both tumor cells and fibroblasts via secretion of IL-11, thereby constituting a feed-forward loop between tumor cells and fibroblasts in the tumor microenvironment.

The stromal fibroblast population in the colon is composed of heterogeneous and distinct cell subtypes that play a crucial role in the development of colitis and colon cancer. Here the authors generate IL-11 reporter mice and characterize the origin and phenotype of inflammatory IL-11⁺ fibroblasts in colitis and colon cancer preclinical models.

Inhibition of Tyrosine-Phosphorylated STAT3 in Human Breast and Lung Cancer Cells by Manuka Honey is Mediated by Selective Antagonism of the IL-6 Receptor

Aberrantly high levels of tyrosine-phosphorylated signal transducer and activator of transcription 3 (p-STAT3) are found constitutively in ~50% of human lung and breast cancers, acting as an oncogenic transcription factor. We previously demonstrated that Manuka honey (MH) inhibits p-STAT3 in breast cancer cells, but the exact mechanism remained unknown. Herein, we show that MH-mediated inhibition of p-STAT3 in breast (MDA-MB-231) and lung (A549) cancer cell lines is accompanied by decreased levels of gp130 and p-JAK2, two upstream components of the IL-6 receptor (IL-6R) signaling pathway. Using an ELISA-based assay, we demonstrate that MH binds directly to IL-6Rα, significantly inhibiting (~60%) its binding to the IL-6 ligand. Importantly, no evidence of MH binding to two other cytokine receptors, IL-11Rα and IL-8R, was found. Moreover, MH did not alter the levels of tyrosine-phosphorylated or total Src family kinases, which are also constitutively activated in cancer cells, suggesting that signaling via other growth factor receptors is unaffected by MH. Binding of five major MH flavonoids (luteolin, quercetin, galangin, pinocembrin, and chrysin) was also tested, and all but pinocembrin could demonstrably bind IL-6Rα, partially (30-35%) blocking IL-6 binding at the highest concentration (50 μM) used. In agreement, each flavonoid inhibited p-STAT3 in a dose-dependent manner, with estimated IC50 values in the 3.5-70 μM range. Finally, docking analysis confirmed the capacity of each flavonoid to bind in an energetically favorable configuration to IL-6Rα at a site predicted to interfere with ligand binding. Taken together, our findings identify IL-6Rα as a direct target of MH and its flavonoids, highlighting IL-6R blockade as a mechanism for the anti-tumor activity of MH, as well as a viable therapeutic target in IL-6-dependent cancers.

Production and characterization of genetically modified human IL-11 variants

Interleukin-11 (IL-11) has been expected as a drug on severe thrombocytopenia caused by myelo-suppressive chemotherapy. Whereas, development of IL-11 inhibitor is also expected for a treatment against IL-11 related cancer progression. Here, we will demonstrate the creation of various kinds of genetically modified hIL-11s. Modified vectors were constructed by introducing N- or O-glycosylation site on the region of hIL-11 that does not belong to the core α-helical motif based on the predicted secondary structure. N-terminal (N: between 22 to 23 aa), the first loop (M1:70 to 71 aa), the second loop (M2:114-115 aa), the third loop (M3:160-161 aa) and C-terminal (C: 200- aa) were selected for modification. A large scale production system was established and the characteristics of modified hIL-11s were evaluated. The structure was analyzed by amino acid sequence and composition analysis and CD-spectra. Glycan was assessed by monosaccharide composition analysis. Growth promoting activity and biological stability were analyzed by proliferation of T1165 cells. N-terminal modified proteins were well glycosylated and produced. Growth activity of 3NN with NASNASNAS sequence on N-terminal was about tenfold higher than wild type (WT). Structural and biological stabilities of 3NN were also better than WT and residence time in mouse blood was longer than WT. M1 variants lacked growth activity though they are well glycosylated and secondary structure is very stable. Both of 3NN and OM1 with AAATPAPG on M1 associated with hIL-11R strongly. These results indicate N-terminal and M1 variants will be expected for practical use as potent agonists or antagonists of hIL-11.

Emerging roles for IL-11 signaling in cancer development and progression: Focus on breast cancer

Interleukin (IL)-11 is a member of the IL-6 family of cytokines that is defined by the shared use of the GP130 signal transducing receptor subunit. In addition of its long recognized activities as a hemopoietic growth factor, IL-11 has an emerging role in epithelial cancer biology. Through the activation of the GP130-Janus kinase signaling cascade and associated transcription factor STAT3, IL-11 can confer many of the tumor intrinsic 'hallmark' capabilities to neoplastic cells, if they express the ligand-specific IL-11Rα receptor subunit. Accordingly, IL-11 signaling has recently been identified as a rate-limiting step for the growth tumors arising from the mucosa of the gastrointestinal tract. However, there is less appreciation for a potential role of IL-11 to support breast cancer progression, apart from its well documented capacity to facilitate bone metastasis. Here we review evidence that IL-11 expression in breast cancer correlates with poor disease outcome and discuss some of the molecular mechanisms that are likely to underpin these observations. These include the capacity of IL-11 to stimulate survival and proliferation of cancer cells alongside angiogenesis of the primary tumor and of metastatic progenies at distant organs. We review current strategies to interfere with IL-11 signaling and advocate that inhibition of IL-11 signaling may represent an emerging therapeutic opportunity for numerous cancers.

Autocrine production of IL-11 mediates tumorigenicity in hypoxic cancer cells

IL-11 and its receptor, IL-11Ra, are expressed in human cancers; however, the functional role of IL-11 in tumor progression is not known. We found that IL11 is a hypoxia-inducible, VHL-regulated gene in human cancer cells and that expression of IL11 mRNA was dependent, at least in part, on HIF-1. A cooperative interaction between HIF-1 and AP-1 mediated transcriptional activation of the IL11 promoter. Additionally, we found that human cancer cells expressed a functional IL-11Ra subunit, which triggered signal transduction either by exogenous recombinant human IL-11 or by autocrine production of IL-11 in cells cultured under hypoxic conditions. Silencing of IL11 dramatically abrogated the ability of hypoxia to increase anchorage-independent growth and significantly reduced tumor growth in xenograft models. Notably, these results were phenocopied by partial knockdown of STAT1 in a human prostate cancer cell line (PC3), suggesting that this pathway may play an important role in mediating the effects of IL-11 under hypoxic conditions. In conclusion, these results identify IL11 as an oxygen- and VHL-regulated gene and provide evidence of a pathway "hijacked" by hypoxic cancer cells that may contribute to tumor progression.

IL-11 produced by breast cancer cells augments osteoclastogenesis by sustaining the pool of osteoclast progenitor cells

BACKGROUND

Interleukin (IL)-11, a cytokine produced by breast cancer, has been implicated in breast cancer-induced osteolysis (bone destruction) but the mechanism(s) of action remain controversial. Some studies show that IL-11 is able to promote osteoclast formation independent of the receptor activator of NF-κB ligand (RANKL), while others demonstrate IL-11 can induce osteoclast formation by inducing osteoblasts to secrete RANKL. This work aims to further investigate the role of IL-11 in metastasis-induced osteolysis by addressing a new hypothesis that IL-11 exerts effects on osteoclast progenitor cells.

METHODS

To address the precise role of breast cancer-derived IL-11 in osteoclastogenesis, we determined the effect of breast cancer conditioned media on osteoclast progenitor cells with or without an IL-11 neutralizing antibody. We next investigated whether recombinant IL-11 exerts effects on osteoclast progenitor cells and survival of mature osteoclasts. Finally, we examined the ability of IL-11 to mediate osteoclast formation in tissue culture dishes and on bone slices in the absence of RANKL, with suboptimal levels of RANKL, or from RANKL-pretreated murine bone marrow macrophages (BMMs).

RESULTS

We found that freshly isolated murine bone marrow cells cultured in the presence of breast cancer conditioned media for 6 days gave rise to a population of cells which were able to form osteoclasts upon treatment with RANKL and M-CSF. Moreover, a neutralizing anti-IL-11 antibody significantly inhibited the ability of breast cancer conditioned media to promote the development and/or survival of osteoclast progenitor cells. Similarly, recombinant IL-11 was able to sustain a population of osteoclast progenitor cells. However, IL-11 was unable to exert any effect on osteoclast survival, induce osteoclastogenesis independent of RANKL, or promote osteoclastogenesis in suboptimal RANKL conditions.

CONCLUSIONS

Our data indicate that a) IL-11 plays an important role in osteoclastogenesis by stimulating the development and/or survival of osteoclast progenitor cells and b) breast cancer may promote osteolysis in part by increasing the pool of osteoclast progenitor cells via tumor cell-derived IL-11. However, given the heterogeneous nature of the bone marrow cells, the precise mechanism by which IL-11 treatment gives rise to a population of osteoclast progenitor cells warrants further investigation.

Bioengineering embryonic stem cell microenvironments for the study of breast cancer

Breast cancer is the most prevalent disease amongst women worldwide and metastasis is the main cause of death due to breast cancer. Metastatic breast cancer cells and embryonic stem (ES) cells display similar characteristics. However, unlike metastatic breast cancer cells, ES cells are nonmalignant. Furthermore, embryonic microenvironments have the potential to convert metastatic breast cancer cells into a less invasive phenotype. The creation of in vitro embryonic microenvironments will enable better understanding of ES cell-breast cancer cell interactions, help elucidate tumorigenesis, and lead to the restriction of breast cancer metastasis. In this article, we will present the characteristics of breast cancer cells and ES cells as well as their microenvironments, importance of embryonic microenvironments in inhibiting tumorigenesis, convergence of tumorigenic and embryonic signaling pathways, and state of the art in bioengineering embryonic microenvironments for breast cancer research. Additionally, the potential application of bioengineered embryonic microenvironments for the prevention and treatment of invasive breast cancer will be discussed.

Preeclampsia-related increase of interleukin-11 expression in human decidual cells

Preeclampsia is associated with increased systemic inflammation and superficial trophoblast invasion, which leads to insufficient uteroplacental blood flow. Interleukin (IL)-11 mediates pro- and anti-inflammatory processes and facilitates decidualization. To identify IL11 expression in vivo at the maternal-placental interface in preeclampsia and control specimens and to evaluate the regulatory effects of tumor necrosis factor-α (TNF) and IL1B, cytokines elevated in preeclampsia, on IL11 levels in first trimester decidual cells in vitro, placental sections were immunostained for IL11. Leukocyte-free first trimester decidual cells were incubated with estradiol (E(2))±10(-7)  mol/l medroxyprogesterone acetate±TNF or IL1B± inhibitors of the p38 MAP kinase (p38 MAPK), nuclear factor-κ B (NFKB), or protein kinase C (PKC) signaling pathways. An ELISA assessed secreted IL11 levels, and quantitative RT-PCR measured IL11 mRNA. IL11 immunoreactivity in placental sections was significantly higher in the cytoplasm of preeclamptic decidual cells versus gestational age-matched controls. Compared to decidual cells, IL11 immunostaining in neighboring trophoblast is lower, perivascular, and not different between control and preeclamptic specimens. TNF and IL1B enhanced levels of IL11 mRNA and secreted IL11 in cultured decidual cells. Specific inhibitors of the p38 MAPK and NFKB, but not PKC signaling pathways, reduced the stimulatory effect of IL1B. Expression of decidual IL11 is increased in preeclampsia and suggests a role for IL11 in the pathogenesis of preeclampsia.

More than a sidekick: the IL-6 family cytokine IL-11 links inflammation to cancer

IL-11, a member of the IL-6 family of cytokines, exerts pleiotropic activities by stimulating hemopoiesis and thrombopoiesis, regulating macrophage differentiation, and conferring mucosal protection in the intestine. These effects are mediated by a multimeric complex comprising the ligand-binding IL-11Rα and the ubiquitously expressed gp130R β-subunit, which together, trigger intracellular signaling and engagement of Stat3. In turn, activated Stat3 promotes cell survival and proliferation as well as immune responses associated with inflammatory diseases and tumor progression. IL-6 and IL-11 compete for interaction with gp130, resulting in tissue-specific functions depending on the expression patterns of their respective α-subunit receptors. Although traditionally, IL-6 has been associated with aberrant Stat3 activation and associated pathologies, here, we discuss newly emerging roles for IL-11 in linking inflammation to cancer progression. We propose that in light of the recurrence of persistent STAT3 activation and elevated IL-11 expression in inflammation-associated gastrointestinal cancers in humans, inhibition of Stat3 or pharmacologically, more amenable upstream molecules such as IL-11 may represent novel, therapeutic targets.

Identification of prospective factors promoting osteotropism in breast cancer: a potential role for CITED2

Breast cancer metastases develop in the bone more frequently than any other site and are a common cause of morbidity in the form of bone pain, pathological fractures, nerve compression and life-threatening hypercalcemia. Despite ongoing research efforts, the molecular and cellular mechanisms that regulate breast cancer cell homing to and colonization of the bone as well as resultant pathological bone alteration remain poorly understood. To identify key mediators promoting breast cancer metastasis to bone, we utilized an immunocompetent, syngeneic murine model of breast cancer metastasis employing the mammary tumor cell line NT2.5. Following intracardiac injection of NT2.5 cells in neu-N mice, metastases developed in the bone, liver and lung, closely mimicking the anatomical distribution of metastases in patients with breast cancer. Using an in vivo selection process, we established NT2.5 sublines demonstrating an enhanced ability to colonize the bone and liver. Genome-wide cDNA microarray analysis comparing gene expression between parental NT2.5 cells and established sublines revealed both known and novel mediators of bone metastasis and osteolysis, including the transcriptional co-activator CITED2. In further studies, we found that expression of CITED2 was elevated in human primary breast tumors and bone metastasis compared to normal mammary epithelium and was highest in breast cancer cell lines that cause osteolytic bone metastasis in animal models. In addition, reducing CITED2 expression in NT2.5 cells inhibited the establishment of bone metastasis and osteolysis in vivo, suggesting a potential role for CITED2 in promoting breast cancer bone metastasis.

Extracellular calcium increases bisphosphonate-induced growth inhibition of breast cancer cells

Introduction

Bisphosphonates have become standard therapy for the treatment of skeletal complications related to breast cancer. Although their therapeutic effects mainly result from an inhibition of osteoclastic bone resorption, in vitro data indicate that they also act directly on breast cancer cells, inhibiting proliferation and inducing apoptosis.

Methods

The present study examined the effects of calcium (from 0.6 to 2.0 mmol/l) on the antitumour activity of the bisphosphonate ibandronate (1 to 1,000 nmol/l) on MDA-MB-231 and MCF-7 breast cancer cells. Cell culture densities were determined using crystal violet staining assay. Apoptotic cell death was assessed by annexin V-phycoerythrin and 7-amino-actinomycin double staining.

Results

At low calcium concentration, 30 μmol/l ibandronate had no effect on MDA-MB-231 cells growth and only slightly inhibited MCF-7 cells growth. Higher calcium levels significantly increased growth inhibition as well as cell apoptosis induced by ibandronate. We observed similar effects with zoledronic acid. Of note, enhancement of ibandronate-induced growth inhibition was also observed in other breast cancer cell lines (T-47D, ZR-75, Hs-578T and BT-549 cells). The growth inhibitory effect of ibandronate in the presence of high concentrations of calcium was partly suppressed by the calcium chelator EGTA (ethylene glycol tetra-acetic acid). In addition, in the presence of calcium at high concentrations, cells accumulated more [¹⁴C]ibandronate than at low calcium concentrations. We obtained further evidence of enhancement of cellular ibandronate accumulation by calcium by demonstrating that high calcium levels increased the inhibition of protein prenylation induced by the bisphosphonate.

Conclusion

Altogether, our data suggest that extracellular calcium, probably through its binding to ibandronate, markedly increased its cellular accumulation and its inhibitory activity on breast tumour cells. Thus, calcium released during the process of tumour-induced osteolysis might enhance the antitumour effects of bisphosphonates and contribute to their therapeutic efficacy.

The role of growth differentiation factor-9 (GDF-9) and its analog, GDF-9b/BMP-15, in human breast cancer

BACKGROUND

There has been a recent surge of interest in the role of growth differentiation factors and other bone morphogenic proteins in the development and spread of cancer. In this study we have provided evidence that highlights the significance of growth and differentiation factor-9a (GDF-9a) and GDF-9b (bone morphogenic protein-15, BMP-15) in breast cancer development and progression.

METHODS

Primary breast cancer samples (n = 109) and matched background tissues from same patients (n = 33) were processed for frozen section and RNA extraction. Frozen sections from matched tissues were immunostained with GDF-9a and GDF-9b antibodies. Staining intensity was analyzed by computer image analysis. RNA was reverse transcribed and quantified before analysis by quantitative polymerase chain reaction (Q-PCR). Results were expressed as number of transcripts (standardized by beta-actin). The data were compared with the clinical outcome of the disease. The biological effects of the molecule were studied using in vitro assays after forced expression in breast cancer cells.

RESULTS

Highly aggressive breast cancer cells did not express GDF-9a. On forced expression of GDF-9a, breast cancer cells became less invasive. These laboratory findings were analyzed against the clinical information. Primary breast cancer samples with good predicted prognosis had a significantly higher level of GDF-9a than in samples with poor predicted prognosis (P = .004). Patients who remained disease-free at the end of a 10-year follow-up had significantly higher levels of both GDF-9a and GDF-9b in their tissue than those with poor clinical outcome (P = .001 and .014, respectively).

CONCLUSION

Growth differentiation factor-9 family expressed in breast cancer has an inhibitory effect on the progression of human breast cancer.

Breast cancer bone metastasis and current small therapeutics

Patients with advanced breast cancer frequently develop metastasis to bone. Bone metastasis results in intractable pain and a high risk of fractures due to tumor-driven bone loss (osteolysis), which is caused by increased osteoclast activity. Osteolysis releases bone-bound growth factors including transforming growth factor beta (TGF-beta). The widely accepted model of osteolytic bone metastasis in breast cancer is based on the hypothesis that the TGF-beta released during osteolytic lesion development stimulates tumor cell parathyroid hormone related protein (PTHrP), causing stromal cells to secrete receptor activator of NFkappaB ligand (RANKL), thus increasing osteoclast differentiation. Elevated osteoclast numbers results in increased bone resorption, leading to more TGF-beta being released from bone. This interaction between tumor cells and the bone microenvironment results in a vicious cycle of bone destruction and tumor growth. Bisphosphonates are commonly prescribed small molecule therapeutics that target tumor-driven osteoclastic activity in osteolytic breast cancers. In addition to bisphosphonate therapies, steroidal and non-steroidal antiestrogen and adjuvant therapies with aromatase inhibitors are additional small molecule therapies that may add to the arsenal for treatment of osteolytic breast cancer. This review focuses on a brief discussion of tumor-driven osteolysis and the effects of small molecule therapies in reducing osteolytic tumor progression.

A new optical and nuclear dual-labeled imaging agent targeting interleukin 11 receptor alpha-chain

Optical imaging has great potential for studying molecular recognitions both in vivo and in vitro, yet nuclear imaging is the most effective clinical molecular imaging modality. The combination of optical and nuclear imaging modalities may provide complementary information for improving diagnosis and management of diseases. In this study we developed an optical and nuclear dual-labeled imaging agent, 111In-DTPA-Bz-NH-SA-K(IR-783-S-Ph-CO)-c(CGRRAGGSC)NH2, called DLIA-IL11Ralpha. 111In-DTPA-Bz-NH-SA is the radiotracer moiety; a near-infrared dye IR-783-S-Ph-COOH serves as the fluorescent emitter; and the cyclic peptide c(CGRRAGGSC), which is known to target interleukin 11 receptor alpha-chain (IL-11Ralpha), delivers the desired imaging agent to its target. Experiments revealed that the cyclic peptide c(CGRRAGGSC) continued to possess the targeting capability to IL-11Ralpha after the conjugation of the optical and nuclear tracers. Furthermore, the presence of the metal isotope chelator did not cause quenching of fluorescence emission. The cross validation and direct comparison of optical and nuclear imaging of a tumor was achieved using a single injection, and the preliminary results show the conjugate has tumor targeting capabilities in vivo.

TGF-beta promotes the establishment of renal cell carcinoma bone metastasis

Bone metastases develop in approximately 30% of patients with RCC, and the mechanisms responsible for this phenomenon are unknown. We found that TGF-beta1 stimulation of RCC bone metastasis cells promotes tumor growth and bone destruction possibly by stimulating paracrine interactions between tumor cells and the bone.

INTRODUCTION

Bone metastasis is a frequent complication and causes marked morbidity in patients with renal cell carcinoma (RCC). Surprisingly, the specific mechanisms of RCC interaction with bone have been scarcely studied despite the inability to prevent or effectively treat bone metastasis. Bone is a reservoir for various growth factors including the pleiotropic cytokine TGF-beta1. TGF-beta1 has been shown to have tumor-supportive effects on advanced cancers and evidence suggests its involvement in promoting the development of breast cancer bone metastasis. Here, we studied the potential role of TGF-beta1 in the growth of RCC bone metastasis (RBM).

MATERIALS AND METHODS

To inhibit TGF-beta1 signaling, RBM cells stably expressing a dominant-negative (DN) TGF-betaRII cDNA were generated. The in vivo effect of TGF-beta1 on RBM tumor growth and osteolysis was determined by histological and radiographic analysis, respectively, of athymic nude mice after intratibial injection of parental, empty vector, or DN RBM cells. The in vitro effect of TGF-beta1 on RBM cell growth was determined after TGF-beta1 treatment by MTT assay.

RESULTS

TGF-beta1 and the TGF-beta receptors I and II (TGF-betaRI/II) were consistently expressed in both RBM tissues and cell lines. Inhibition of TGF-beta1 signaling in RBM cells significantly reduced tumor establishment and osteolysis observed in vivo after injection into the murine tibia, although no effect on tumor establishment was observed after injection of RBM cells subcutaneously or into the renal subcapsule. Treatment of five RBM cell lines with TGF-beta1 in vitro either had no effect (2/5) or resulted in a significant inhibition (3/5) of cell growth, suggesting that TGF-beta1 may promote RBM tumor growth indirectly in vivo.

CONCLUSIONS

TGF-beta1 stimulation of RBM cells plays a role in promoting tumor growth and subsequent osteolysis in vivo, likely through the initiation of tumor-promoting paracrine interactions between tumor cells and the bone microenvironment. These data suggest that inhibition of TGF-beta1 signaling may be useful in the treatment of RBM.

Expression of Interleukin 11 and Its Receptor and Their Prognostic Value in Human Breast Cancer

BACKGROUND

Recent experimental evidence has shown a potential role of interleukin (IL)-11 and its receptor in breast cancer development and progression. However, there is little clinical information to support this hypothesis. We examined the expression of IL-11 and its receptor in primary breast cancer tissue samples and correlated their level of expression with the clinical outcome.

METHODS

Primary breast cancer samples (n=109) and matched background tissue obtained from patients in the cohort (n=33) were processed for frozen section and RNA extraction. Frozen sections from matched tissues were immunostained with IL-11 and IL-11 receptor antibodies. Staining intensity was analyzed by computer image analysis. RNA was reverse-transcribed and quantified before analysis by quantitative polymerase chain reaction. Results were expressed as the number of transcripts (standardized by beta-actin). The data were compared with the clinical outcome of the disease.

RESULTS

The intensity of staining for both IL-11 and the IL-11 receptor was distinctly high in tumor samples (P<.01). The transcript level of IL-11 was significantly higher in node-positive tumor samples compared with node-negative samples (P=.02). Tumors with a poor prognostic index and poor histological grade showed a higher level of IL-11. A higher level of IL-11 was linked to poorer survival with Kaplan-Meier survival analysis.

CONCLUSIONS

IL-11 can be a predictor of poor prognosis in human breast cancer.

COX-2 Induces IL-11 Production in Human Breast Cancer Cells

BACKGROUND

Cyclooxygenase-2 (COX-2) is overexpressed in 40% of human invasive breast cancers. Interleukin-11 (IL-11), a potent mediator of osteoclastogenesis, is involved in breast cancer metastasis to bone. Since breast cancers that overexpress COX-2 are associated with a higher rate of metastasis to bone, we hypothesized that COX-2 expression in tumor cells would induce IL-11.

MATERIALS AND METHODS

We transfected MCF-7 (poorly metastatic) and MDA-231 (highly metastatic) human breast cancer cell lines with COX-2 expression vectors. COX-2 overexpression was confirmed by Western blot and PGE(2) immunoassay, and IL-11 production was measured by immunoassay. We also used a nude mouse model to study COX-2 and IL-11 production from breast cancer cells that metastasized to bone. The bone-seeking clones (BSC) were isolated and cultured from the long bone metastases.

RESULTS

COX-2 transfection caused an approximately 5- to 6-fold increase in IL-11 production in both MCF-7 and MDA-231 cells. MDA-435S-COX2-BSC (cells isolated from bone metastasis) produced elevated levels of IL-11 and PGE2 (an important mediator of COX-2) as compared to the parental MDA-435S-COX2 cells. Furthermore, a treatment with low 1- to 2-microm concentration NS-398 or Celecoxib significantly reduced the production of IL-11 in COX-2-transfected MDA-231 cells, thus confirming the involvement of COX-2 in IL-11 induction.

CONCLUSION

COX-2-mediated production of IL-11 in breast cancer cells may be vital to the development of osteolytic bone metastases in patients with breast cancer, and a COX-2 inhibitor may be useful in inhibiting this process.

Nuclear factor-kappaB-dependent mechanisms in breast cancer cells regulate tumor burden and osteolysis in bone

A central mediator of a wide host of target genes, the nuclear factor-kappaB (NF-kappaB) family of transcription factors, has emerged as a molecular target in cancer and diseases associated with bone destruction. To evaluate how NF-kappaB signaling in tumor cells regulates processes associated with osteolytic bone tumor burden, we stably infected the bone-seeking MDA-MB-231 breast cancer cell line with a dominant-negative mutant IkappaB that prevents phosphorylation of IkappaBalpha and associated nuclear translocation of NF-kappaB. Blockade of NF-kappaB signaling in MDA-MB-231 cells by the mutant IkappaB decreased in vitro cell proliferation, expression of the proinflammatory, bone-resorbing cytokine interleukin-6, and in vitro bone resorption by tumor/osteoclast cocultures while reciprocally up-regulating production of the proapoptotic enzyme caspase-3. Suppression of NF-kappaB transcription in these breast cancer cells also reduced incidence of in vivo tumor-mediated osteolysis after intratibial injection of tumor cells in female athymic nude mice. Immunohistochemistry showed that the cancerous lesions formed in bone by MDA-MB-231 cells express both interleukin-6 and the p65 subunit of NF-kappaB at the bone-tumor interface. NF-kappaB signaling in breast cancer cells therefore promotes bone tumor burden and tumor-mediated osteolysis through combined control of tumor proliferation, cell survival, and bone resorption. These findings imply that NF-kappaB and its associated genes may be relevant therapeutic targets in osteolytic tumor burden.

The production of interleukin-11 and decidualization are compromised in endometrial stromal cells derived from patients with infertility

IL-11 signaling is critical for decidualization of the endometrial stroma in early pregnancy in the mouse. In this study, we investigate the function of IL-11 signaling in cAMP-induced decidualization of human endometrial stromal cells. We show that treatment of endometrial stromal cells with 8-bromo-cAMP (8-Br-cAMP) results in an increase in the levels of secreted IL-11, whereas levels of cell surface IL-11 receptor alpha are similar with or without 8-Br-cAMP treatment. The production of IL-11 correlates with the production of molecular markers of decidualization, prolactin and IGF-binding protein-1. The expression of these markers is inhibited when IL-11 signaling is specifically blocked in decidualizing endometrial stromal cells by the IL-11 antagonist W147A. We demonstrate that 8-Br-cAMP-induced endometrial stromal cells derived from patients with primary infertility produce lower levels of prolactin, IGF-binding protein-1, and IL-11 than cells derived from fertile women. Our results suggest that IL-11 expression is critically important during decidualization in the human endometrium, and that aberrant regulation of endometrial IL-11 production may be associated with some types of infertility.

Serum Interleukin-11 in Patients with Benign Prostatic Hyperplasia and Prostate Cancer

To clarify whether serum levels of interleukin-11 (IL-11) could be a useful marker in patients with prostate cancer, serum IL-11 was determined in 73 and 23 men with prostate cancer and benign prostate hyperplasia (BPH), respectively, before treatment. There were no statistical differences of IL-11 levels between patients with prostate cancer and BPH. Patients with hormone-resistant prostate cancer had a significantly higher level of IL-11 than those with untreated cancer. Serum IL-11 levels may be a potential tumor marker for prostate cancer progression.

Relevance of breast cancer cell lines as models for breast tumours: an update

The number of available breast cancer cell (BCC) lines is small, and only a very few of them have been extensively studied. Whether they are representative of the tumours from which they originated remains a matter of debate. Whether their diversity mirrors the well-known inter-tumoural heterogeneity is another essential question. While numerous similarities have long been found between cell lines and tumours, recent technical advances, including the use of micro-arrays and comparative genetic analysis, have brought new data to the discussion. This paper presents most of the BCC lines that have been described in some detail to date. It evaluates the accuracy of the few of them widely used (MCF-7, T-47D, BT-474, SK-BR-3, MDA-MB-231, Hs578T) as tumour models. It is concluded that BCC lines are likely to reflect, to a large extent, the features of cancer cells in vivo. The importance of oestrogen receptor-alpha (gene ESR1 ) and Her-2/ neu ( ERBB2 ) as classifiers for cell lines and tumours is underlined. The recourse to a larger set of cell lines is suggested since the exact origin of some of the widely used lines remains ambiguous. Investigations on additional specific lines are expected to improve our knowledge of BCC and of the dialogue that these maintain with their surrounding normal cells in vivo.

Tumor necrosis factor-alpha induces interleukin-6 production via extracellular-regulated kinase 1 activation in breast cancer cells

Interleukin-6 (IL-6) and interleukin-11 (IL-11) are frequently produced by breast cancer cells. These interleukins promote osteoclast formation and may mediate osteolysis at the site of breast cancer bone metastases. Transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) up-regulate IL-6 and IL-11 production in a cytokine-dependent fashion in breast cancer cells, but very little is known about their intracellular signaling pathways in breast cancer cells. To study TGF-beta, TNF-alpha and IL-1beta regulation of IL-6 and IL-11 production in human MDA-MB-231 breast cancer cells, we established single cell clones stably expressing dominant negative (DN) forms of the mitogen-activated protein kinases p38 (p38/AF) or ERK1 (ERK1K71R). We show here, that while basal, TGF-beta and IL-1beta induced IL-6 production was similar in parental cells and in pcDNA3 control, ERK1K71R and p38/AF clones, TNF-alpha induced IL-6 production was blunted in the ERK1K71R clones. TGF-beta and IL-1beta, but not TNF-alpha, induced IL-11 production in parental MDA-MB-231 cells. Similar findings were detected in clones stably expressing p38/AF and ERK1K71R, which did not change basal IL-11 production either. In conclusion, TNF-alpha induced IL-6 production is mediated via ERK1 activation in MDA-MB-231 cells. These observations may be helpful in designing new anti-osteolytic therapies.

Mechanisms of osteolytic bone metastases in breast carcinoma

Osteolytic and osteoblastic metastases are often the cause of considerable morbidity in patients with advanced prostate and breast carcinoma. Breast carcinoma metastasis to bone occurs because bone provides a favorable site for aggressive behavior of metastatic cancer cells. A vicious cycle arises between cancer cells and the bone microenvironment, which is mediated by the production of growth factors such as transforming growth factor beta and insulin growth factor from bone and parathyroid hormone-related protein (PTHrP) produced by tumor cells. Osteolysis and tumor cell accumulation can be interrupted by inhibiting any of these limbs of the vicious cycle. For example, bisphosphonates (e.g., pamidronate, ibandronate, risedronate, clodronate, and zoledronate) inhibit both bone lesions and tumor cell burden in bone in experimental models of breast carcinomametastasis. Neutralizing antibodies to PTHrP, which inhibit PTHrP effects on osteoclastic bone resorption, also reduce osteolytic bone lesions and tumor burden in bone. Other pharmacologic approaches to inhibit PTHrP produced by breast carcinoma cells in the bone microenvironment also produce similar beneficial effects. Identification of the molecular mechanisms responsible for osteolytic metastases is crucial in designing effective therapy for this devastating complication.

Immunolocalization of matrix metalloproteinases and their inhibitors in clinical specimens of bone metastasis from breast carcinoma

Matrix metalloproteinases (MMPs) are essential in several stages of the metastatic process, and in normal bone development and remodeling. We explored whether the interaction between tumor cells and bone leads to changes in MMP and tissue inhibitor of MMP (TIMP) expression thus affecting osteolysis in metastatic bone disease. Using immunohistochemistry we have investigated the MMP/TIMP expression in tumor cells, fibroblasts, osteoblasts and osteoclasts. Thirty one specimens of bone metastasis from breast carcinoma were stained for MMP-1, -2, -9, MT1-MMP and TIMP-1, and -2 and compared with staining in normal breast tissue, primary breast carcinoma and normal bone. Specimens came from patients in three clinical scenarios: from open biopsies without or with pathological fracture, or bone marrow biopsies containing tumor from patients with pancytopenia but without clinical evidence of osteolysis. By bone histomorphometry the latter group showed a heavy tumor load not different from the open biopsy groups but displayed little active bone resorption and low numbers of osteoclasts. Cell type-specific MMP/TIMP expression was observed and the staining patterns were comparable between the three groups of patients. Though no major differences in the MMP/TIMP staining of tumor cells and fibroblasts were observed between bone metastasis and primary tumor, we showed that tumor cells do express MMPs capable of degrading bone matrix collagen. The number and activity of osteoclasts and osteoblasts was increased dramatically in bone metastases, their MMP/TIMP profiles, however, were not different from normal bone, suggesting that the mechanism of bone degradation by osteoclasts is not different from normal bone remodelling.

Breast cancer increases osteoclastogenesis by secreting M-CSF and upregulating RANKL in stromal cells

BACKGROUND

Breast cancer metastasis to bone causes resorption of the mineralized matrix by osteoclasts. Macrophage colony stimulating factor (M-CSF)and receptor activator of the NF-kappaB ligand (RANKL) are produced by stromal cells and are essential for osteoclast formation. The human breast cancer cell line, MDA-MB-231, reliably forms bone metastases in a murine model and stimulates osteoclast formation in culture. We hypothesized that MDA-MB-231 stimulates osteoclast formation through secretion of M-CSF and/or RANKL.

MATERIALS AND METHODS

We cocultured MDA-MB-231 and a bone marrow derived cell line, UAMS-33, and evaluated the expression of M-CSF and RANKL mRNA. Osteoclast formation was assessed using these cells added to hematopoietic cell cultures.

RESULTS

MDA-MB-231 exhibited constitutive expression of M-CSF mRNA. As expected, addition of recombinant M-CSF (30 ng/ml) and RANKL (30 ng/ml) to hematopoietic osteoclast precursors supported osteoclast formation, while the addition of soluble RANKL alone or MDA-231 without added RANKL did not. Notably, coculture of MDA-231 with hematopoietic cells and added soluble RANKL stimulated significant osteoclast formation, indicating that MDA-231 served as an effective source for M-CSF. MDA-231 did not express RANKL. However, when cocultured with the murine bone marrow stromal cell line UAMS-33, RANKL expression was significantly increased in the latter cells. MDA-231 also stimulated osteoclast formation in coculture with UAMS-33 and hematopoietic cells.

CONCLUSIONS

We conclude that MDA-MB-231 increases osteoclast formation by secreting adequate amounts of M-CSF protein and enhancing the expression of RANKL by stromal support cells. The ability to stimulate osteoclasts may explain the ability to metastasize to bone.

Breast cancer cells release factors that induced apoptosis in human bone marrow stromal cells

Breast cancer is associated frequently with skeletal metastases, which cause significant morbidity. The main mechanism is an increase in osteoclast-mediated bone resorption. We postulated that osteoblasts could be other essential target cells and previously showed that conditioned medium (CM) of breast cancer cells (BCCs) inhibits the proliferation of osteoblast-like cells. In this study, we investigated the effects of BCC-secreted products on osteoprogenitor cells using a clonal fetal human bone marrow stromal preosteoblastic cell line (FHSO-6) that expresses alkaline phosphatase (ALP) activity, type I collagen (COLI), and increased osteocalcin (OC) and osteopontin under treatment with dexamethasone (Dex), 1,25-dihydroxyvitamin D [1,25(OH)2D], or recombinant human bone morphogenetic protein 2 (rhBMP-2). Treatment with MCF-7 CM inhibited FHSO-6 cell survival in a dose-dependent and irreversible manner. Morphological investigation indicated that MCF-7 CM increased both apoptotic and necrotic cell number. MCF-7 CM increased caspases activity and a broad inhibitor of caspase activity (benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethyl ketone [z-VAD-fmk]) partly reversed the CM-induced inhibition of FHSO-6 cell survival. Western blot analyses revealed an increased bax/bcl-2 ratio in MCF-7 CM-treated FHSO-6 cells. MCF-7 cells exhibit FasLigand as membrane-bound protein and as a soluble cytokine in the CM. Deprivation of MCF-7 CM from active FasLigand by saturation with a soluble Fas molecule suppressed the induction of FHSO-6 apoptosis, whereas fibroblast CM, which did not contain FasLigand, only weakly modified FHSO-6 cell survival because of increased cell necrosis. These data indicate that FasLigand secreted by BCCs induces apoptosis and necrosis of human preosteoblastic stromal cells through caspase cascade modulated by the bax and bcl-2 protein level. The induction of apoptosis in human bone marrow stromal cells by BCCs may contribute to the inappropriately low osteoblast reaction and bone formation during tumor-induced osteolysis in bone metastases.

Interleukins-6 and -11 expression in primary breast cancer and subsequent development of bone metastases

Breast cancers frequently metastasize to bone where they often cause extensive tumor-induced osteoclast-mediated osteolysis. Interleukin-6 (IL-6) and IL-11 are two cytokines exhibiting osteolytic properties through their potent stimulation of osteoclast formation. We investigated the expression of IL-6 and IL-11 in 99 invasive primary breast tumors by immunohistochemistry and in situ hybridization, respectively. We examined their potential as predictive factors for further development of bone metastases. 52/90 (57%) of tumor samples showed IL-6 cytoplasmic immunostaining. There was no significant association between IL-6 status and any of the classical prognostic factors. 15/89 (17%) of the tumor samples expressed IL-11 mRNA. A positive IL-11 mRNA status was associated with a low tumor grade (P=0.05). Tumors expressing IL-11 mRNA had a statistically significant (P=0.002) higher rate of bone metastases occurrence (12/15, 80%) than IL-11 negative tumors (27/74, 37%). Such association was not found for IL-6. Our findings demonstrate for the first time IL-11 gene expression in some primary invasive breast tumors and suggest the potential of this cytokine as possible biological predictive factor for the development of bone metastases.

Estrogen receptor analysis in primary breast tumors by ligand-binding assay, immunocytochemical assay, and northern blot: a comparison

Estrogen receptor (ER) status is an important parameter in breast cancer management. In this study, ER protein contents established by two conventional techniques were confronted to ER mRNA level, to analyze whether the latter may be introduced in routine assay. Eighty-seven breast tumor samples were examined. ER amounts were determined by ligand-binding assay (LBA) and by computer-assisted immunocytochemical assay (ICA), ER mRNA was analysed and quantified by northern blot. Seventy-seven percent of tumor samples examined were positive for ER mRNA and they all expressed the 6.7-kb receptor signal. No trace of small-sized ER mRNA variants was detected in any sample. Following akaike information criterion (AIC) discriminant analysis, a simple linear correlation was found between ER mRNA levels and ER amounts provided by LBA. This was not observed when either mRNA or LBA values were compared to ICA values. These latter were found to rapidly reach a plateau at increasing mRNA or LBA values. In conclusion, our data points to the linear correlation between ER amounts determined in breast tumors at both protein and mRNA levels by quantitative methods; they also indicate that the semi-quantitative computer-associated ICA may complement rather than replace these quantitative methods.

Interleukin-11 (IL-11) in human endometrium: expression throughout the menstrual cycle and the effects of cytokines on endometrial IL-11 production in vitro

Interleukin-11 is a member of the IL-6 family of cytokines. Its presence in mouse decidua has been shown and experiments in genetically modified mice have suggested the importance of its receptor in stromal cell decidualization. In this study we used immunocytochemistry to determine expression of IL-11 in human endometrium. The effects of TNFalpha, IL-1alpha and TGFbeta on IL-11 production by epithelial and stromal cells was also investigated. Immunocytochemical staining in sections cut from 19 endometrial biopsies obtained throughout the menstrual cycle showed that IL-11 was expressed in both human endometrial epithelial and stromal cells, with epithelial staining being more intense than that seen in the stromal cells, at all times except the late secretory phase when the intensity was similar. Basal IL-11 production by cultured epithelial cells was greater than basal production by stromal cells. IL-1alpha, TNFalpha and TGFbeta (0.1-10 ng/ml) all caused a concentration-dependent increase in IL-11 production by both epithelial and stromal cells, but stimulated: basal values were greater for stromal than epithelial cells for all three cytokines. This work shows, for the first time, the presence of IL-11 within the human endometrium and that its production is controlled by other cytokines, which are postulated to play a role in implantation. Thus IL-11 may also play an important role in human endometrial function and embryo implantation.

Interleukin-11 receptor expression in primary ovarian carcinomas

OBJECTIVES

The objectives of this study were to determine (1) the frequency of expression of the interleukin-11 receptor alpha subunit (IL-11Ralpha) and its signal transducing subunit, gp130, among primary ovarian carcinomas; (2) the frequency of expression of IL-11 in ovarian carcinomas; and (3) the potential role IL-11 might have in ovarian cancer cell biology.

METHODS

An immunohistochemical assay was used to determine the expression of IL-11Ralpha and the gp130 cofactor among primary ovarian carcinomas; the expression of IL-11 in ovarian malignancies was determined using reverse transcription polymerase chain reaction (RT-PCR). The ability of IL-11 to stimulate [3H]thymidine incorporation in IL-11R-expressing ovarian carcinoma cell lines (OVCAR-3 and SKOV-3) and/or abrogate cell death mediated by apoptosis-inducing agents using an ELISA assay that quantitates DNA fragmentation was also studied.

RESULTS

IL-11Ralpha was expressed in the malignant epithelial cells of 45 of 48 (93.8%) primary ovarian carcinoma samples studied. In 45 primary ovarian carcinoma samples where both components of the IL-11 receptor (IL-11Ralpha and gp130) were examined, coexpression was observed in 42 (93.3%). Expression of the IL-11 receptor components was also found in the stromal layer. Coexpression of IL-11Ralpha and gp130 was commonly observed in both benign ovarian tumors and in the epithelial layer of normal ovaries. In contrast, IL-11 mRNA was expressed in only 3 of 21 malignant samples studied (14.3%). Recombinant human IL-11 was unable either to stimulate [3H]thymidine incorporation or to block cell death effected by paclitaxel or Fas-activating antibodies in in vitro assays using OVCAR -3 or SKOV-3 cells.

CONCLUSIONS

The IL-11 receptor system is commonly expressed in both malignant and nonmalignant ovarian tissues, although its function in ovarian epithelial cell biology remains unclear.

Increased expression of the interleukin-11 receptor and evidence of STAT3 activation in prostate carcinoma

Previous investigations have shown that interleukin-6, a member of the JAK-STAT activating family of cytokines, plays an important role in prostate carcinoma. Here we demonstrate the co-expression of another member of this cytokine family, interleukin-11 (IL-11), and components of its receptor (interleukin-11 receptor; IL-11R), ie, IL-11Ralpha (involved in ligand recognition), and gp130 (involved in signal transduction) in cultured normal and malignant prostate-derived epithelial cell lines. In the DU-145 prostate carcinoma cell line, rhIL-11 stimulates a transient and dose-dependent increase in the tyrosine 705-phosphorylated, active form of STAT3 (STAT3 P-Tyr705), involved in the downstream signaling of IL-11R and other members of the gp130-dependent receptors. The ability of IL-11 to activate STAT3 in prostate-derived cells may be mechanistically important, given recent data suggesting that constitutively activated STAT3 may be associated with the malignant phenotype. In 51 human primary tissues derived from normal prostate, benign prostatic hyperplasia, and prostate carcinomas, IL-11Ralpha and gp130 were commonly expressed, with a statistically significant elevation in the expression of IL-11Ralpha in prostate carcinoma. Also, the tyrosine-phosphorylated, activated form of STAT3 was observed more prominently in the nuclei of cells residing in malignant glands compared to those in nonmalignant samples. Thus, the IL-11 receptor system is up-regulated in prostate carcinoma, and may be one part of a cytokine network that maintains STAT3 in its activated form in these tissues.

gp130 Cytokine family and bone cells

Bone tissue is continually being remodelled according to physiological circumstances. Two main cell populations (osteoblasts and osteoclasts) are involved in this process, and cellular activities (including cell differentiation) are modulated by hormones, cytokines and growth factors. Within the last 20 years, many factors involved in bone tissue metabolism have been found to be closely related to the inflammatory process. More recently, a cytokine family sharing a common signal transducer (gp130) had been identified, which appears to be a key factor in bone remodelling. This family includes interleukin 6, interleukin 11, oncostatin M, leukaemia inhibitory factor, ciliary neurotrophic factor and cardiotrophin-1. This paper provides an exhaustive review of recent knowledge on the involvement of gp130 cytokine family in bone cell (osteoblast, osteoclast, etc.) differentiation/activation and in osteoarticular pathologies.

Protein production by osteoblasts: modulation by breast cancer cell-derived factors

Breast cancer cells (BCC) frequently metastasize to bone where they may cause tumor-induced osteolysis (TIO). While the important eroding role of the osteoclasts in TIO is well admitted, the possibility that BCC and/or osteoblasts activated by tumoral factors could also directly degrade bone matrix in this pathology has been much less investigated. We show here that the net collagen amount produced in vitro by normal human osteoblasts and osteoblast-like cells was significantly reduced by culture medium conditioned by several BCC lines, including three newly isolated ones. There was no evidence for a decrease in collagen synthesis, as assessed by the production of the carboxyterminal propeptide of type I collagen. In contrast, the effect of BCC-derived medium on collagen amount was attenuated by inhibitors of matrix metalloproteinases (MMPs) as well as by tranexamic acid, an inhibitor of the plasminogen conversion to plasmin, while it was abolished in presence of the two kinds of proteinase inhibitors. This osteoblastic protein degradation activity appeared to be attributable to factors secreted by the osteoblasts as well as by BCC. These factors had molecular weights lower as well as higher than 10 kD. Our data suggest that besides the eroding action of osteoclasts, BCC- and osteoblast-derived MMPs and serine proteinases might play a direct role in bone collagen degradation in TIO.

A novel orthotopic model of breast cancer metastasis to bone

Breast cancer affects approximately one woman in twelve and kills more women than any other cancer. If detected early, patients have a five year survival rate of 66%, but once metastatic disease has developed, there is no effective treatment. About 70% of patients with metastatic disease have bone involvement, while lungs and liver are the other common targets. Bone metastases cause severe pain, pathological fractures and hypercalcaemia and thus are a significant clinical problem. The development of new therapies for metastatic breast carcinoma depends on a better understanding of the mechanism of homing of the tumour cells to bone, liver and lungs and the factors required for their growth in these organs. Research on mechanisms of breast cancer metastasis, particularly to bone, has relied on in vitro studies or on tumour models in which the inoculation route is designed to promote delivery of tumour cells to a specific organ. Metastases in bone are achieved by inoculation into the right ventricle of the heart. To our knowledge there has been no report of a model of metastatic spread from the mammary gland to distant sites which reliably includes bone. In this paper, we describe our recent development of a novel murine model of metastatic breast carcinoma. The new model is unique in that the pattern of metastatic spread closely resembles that observed in human breast cancer. In particular, these murine breast tumours metastasise to bone from the primary breast site and cause hypercalcaemia, characteristics not normally found in murine tumours, but common in human disease. Furthermore, in a preliminary characterisation of this model, we show that secretion of parathyroid hormone-related protein, a role for which has been implicated in breast cancer spread to bone, correlates with metastasis to bone. This model therefore provides an excellent experimental system in which to investigate the factors that control metastatic spread of breast cancer to specific sites, particularly bone. The special advantage of this system is that it involves the whole metastasis process, beginning from the primary site. Existing models consider mechanisms that pertain to growth of tumour once the site has been reached. An understanding of the regulation of these factors by potential therapeutic agents could lead to improvement in therapies designed to combat metastatic disease. For the first time, this development will allow exploration of the molecular basis of site-specific metastasis of breast cancer to bone in a clinically relevant model.