Breast cancer cells induce osteoclast formation by stimulating host IL-11 production and downregulating granulocyte/macrophage colony-stimulating factor

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.

IL-6 Cytokine Family: A Putative Target for Breast Cancer Prevention and Treatment

The IL-6 cytokine family is a group of signaling molecules with wide expression and function across vertebrates. Each member of the family signals by binding to its specific receptor and at least one molecule of gp130, which is the common transmembrane receptor subunit for the whole group. Signal transduction upon stimulation of the receptor complex results in the activation of multiple downstream cascades, among which, in mammary cells, the JAK-STAT3 pathway plays a central role. In this review, we summarize the role of the IL-6 cytokine family—specifically IL-6 itself, LIF, OSM, and IL-11—as relevant players during breast cancer progression. We have compiled evidence indicating that this group of soluble factors may be used for early and more precise breast cancer diagnosis and to design targeted therapy to treat or even prevent metastasis development, particularly to the bone. Expression profiles and possible therapeutic use of their specific receptors in the different breast cancer subtypes are also described. In addition, participation of these cytokines in pathologies of the breast linked to lactation and involution of the gland, as post-partum breast cancer and mastitis, is discussed.

In situ Synthesized Monosodium Urate Crystal Enhances Endometrium Decidualization via Sterile Inflammation During Pregnancy

High level of uric acid (UA) is the major origin of gout, and is highly associated with various pregnant complications, such as preeclampsia and gestational diabetes. However, UA’s level and role in the very early stage of pregnancy has not been uncovered. This study aims to investigate the relevance of serum UA and decidualization, an essential process for the establishment and maintenance of pregnancy in women and mice during the early stage of pregnancy. In this study, we first proved that expression level of UA synthase xanthine dehydrogenase (XDH) is highly increased along with decidualization of endometrial stromal cells in both in vitro and in vivo models. Furthermore, serum and endometrial levels of UA are higher in mice with decidualized uterin horn and in vitro decidualized stromal cells. The existence of monosodium urate (MSU) crystal was also confirmed by immunostaining. Next, the roles of MSU on decidualization were explored by both in vitro and in vivo models. Our data shows MSU crystal but not UA enhances the decidualization response of endometrial stromal cells, via the upregulation of inflammatory genes such Ptgs2 and Il11. inhibiting of Cox-2 activity abolishes MSU crystal induced higher expression of decidualization marker Prl8a2. At last, in women, we observed enriched expression of XDH in decidua compare to non-decidualized endometrium, the serum level of UA is significantly increased in women in very early stage of pregnancy, and drop down after elective abortion. In summary, we observed an increased serum UA level in the early stage of women’s pregnancy, and proved that the increased level of UA results from the expressed XDH in decidualizing endometrium of both human and mouse, leading to the formation of MSU crystal. MSU crystal can enhance the decidualization response via inflammatory pathways. Our study has uncovered the association between UA, MSU, and decidualization during the early stage of pregnancy.

Conditions Mimicking the Cancer Microenvironment Modulate the Functional Outcome of Human Chorionic Villus Mesenchymal Stem/Stromal Cells in vitro

Mesenchymal stem/stromal cells isolated from chorionic villi of human term placentae (CV-MSCs) possess unique biological characters. They exhibit self-renewal, directional migration, differentiation, and immunomodulatory effects on other cell lineages, by virtue of which they can be utilized as therapeutic carriers, for drug targeting, and therapy. Tumors display characteristic features of a damaged tissue microenvironment, which is saturated with conditions such as hypoxia, sustained inflammation, and increased oxidative stress. CV-MSCs function normally in a high oxidative stress environment induced by hydrogen peroxide (H₂O₂) and glucose and also protect endothelial cells from their damaging effects. For their therapeutic applications in a disease like cancer, it is necessary to ascertain the effects of tumor microenvironment on their functional outcome. In this study, we investigated the functional activities, of CV-MSCs in response to conditioned media (CM) obtained from the culture of breast cancer cell line MDA-231 (CM-MDA231). CV-MSCs were exposed to CM-MDA231 for different spatio-temporal conditions, and their biological functions as well as modulation in gene expression were evaluated. Effect of CM-MDA231 on factors responsible for changes in functional outcome were also investigated at the protein levels. CV-MSCs exhibited significant reduction in proliferation but increased adhesion and migration after CM-MDA231 treatment. Interestingly, there was no change in their invasion potential. CM-MDA231 treatment modulated expression of various genes involved in important cellular events including, integration, survival, message delivery and favorable outcome after transplantation. Analysis of pathways related to cell cycle regulation revealed significant changes in the expression of p53, and increased phosphorylation of Retinoblastoma (Rb) and Checkpoint Kinase 2 in CV-MSCs treated with CM-MDA231. To summarize, these data reveal that CV-MSCs retain the ability to survive, adhere, and migrate after sustained treatment with CM-MDA231, a medium that mimics the cancer microenvironment. These properties of CV-MSCs to withstand the inflammatory tumor like microenvironment prove that they may make useful candidate in a stem cell based therapy against cancer. However, further pre-clinical studies are needed to validate their therapeutic usage.

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.

The downregulation of IGFBP3 by TGF-β signaling in oral cancer contributes to the osteoclast differentiation

Oral squamous cell carcinoma (OSCC) frequently invades nearby bone and bone involvement determines the prognosis of patients. Growth factors, stored in the bone matrix and released during bone destruction, are known as key components in the bone-tumor interaction. However, the coordination of growth factor signals and the precise mechanism of bone destruction in oral cancer are still unclear. In the study, we investigated the differential cytokine expression profile of oral cancer cells by TGF-β treatment and the function of altered expression of cytokines on the osteoclast differentiation. We established TGFBR2-knockdown cells using small hairpin RNA. TGF-β was treated to both TGFBR2 expressing and knockdown cells and the culture supernatants were analyzed using a cytokine array kit. We found that the TGF-β inhibited IGFBP3 level and enhanced MMP9 level. We confirmed this regulation of IGFBP3 and MMP9 by TGF-β using ELISA and zymography, respectively. IGFBP3 is known as to modulate the bioavailability of IGF1, which is abundant in the bone microenvironment and regulates osteoclast differentiation. Therefore, we further analyzed the function of IGFBP3 on osteoclastogenesis. Although IGFBP3 increased the viability of murine bone marrow macrophages, the osteoclast differentiation of these cells was blocked by IGFBP3 in a dose-dependent manner. These results revealed a novel pathway for the regulation of osteoclastogenesis by oral cancer cells, which may be a new therapeutic target for osteolysis induced by oral cancer infiltrating into the bone.

Cancer Conditioned Medium Modulates Functional and Phenotypic Properties of Human Decidua Parietalis Mesenchymal Stem/Stromal Cells

Background

Mesenchymal Stem/Stromal Cells (MSCs) from the decidua parietalis (DPMSCs) of human term placenta express several molecules with important biological and immunological properties. DPMSCs induce natural killer cell expression of inflammatory receptors and their cytotoxic activity against cancer cells. These properties make DPMSCs promising therapeutical agent for cancer. The successful development of MSCs as an anti-cancer therapeutic cells rely on their ability to function in a hostile inflammatory and oxidative stress cancer environment. Here, we studied the effects of conditioned medium obtained from the culture of breast cancer cells (CMMDA-231) on the functional and phenotypic properties of DPMSCs.

Methods

DPMSCs were cultured with CMMDA-231 and important functions of DPMSCs were measured. The effect of CMMDA-231 on DPMSC expression of several genes with different functions was also evaluated.

Results

DPMSCs were able to function in response to CMMDA-231, but with reduced proliferative and adhesive potentials. Preconditioning of DPMSCs with CMMDA-231 enhanced their adhesion while reducing their invasion. In addition, CMMDA-231 modulated DPMSC expression of many genes with various functional (i.e., proliferation, adhesion, and invasion) properties. DPMSCs also showed increased expression of genes with anti-cancer property.

Conclusion

These data show the ability of DPMSCs to survive and function in cancer environment. In addition, preconditioning of DPMSCs with CMMDA-231 enhanced their anti-cancer properties and thus demonstrating their potential as an anti-cancer therapeutic agent. However, future studies are essential to reveal the mechanism underlying the effects of MDA-231 on DPMSC functional activities and also to confirm the anti-cancer therapeutic potential of DPMSCs.

Bone Metastases in Neuroendocrine Neoplasms: From Pathogenesis to Clinical Management

Bone represents a common site of metastases for several solid tumors. However, the ability of neuroendocrine neoplasms (NENs) to localize to bone has always been considered a rare and late event. Thanks to the improvement of therapeutic options, which results in longer survival, and of imaging techniques, particularly after the introduction of positron emission tomography (PET) with gallium peptides, the diagnosis of bone metastases (BMs) in NENs is increasing. The onset of BMs can be associated with severe skeletal complications that impair the patient’s quality of life. Moreover, BMs negatively affect the prognosis of NEN patients, bringing out the lack of curative treatment options for advanced NENs. The current knowledge on BMs in gastro-entero-pancreatic (GEP) and bronchopulmonary (BP) NENs is still scant and is derived from a few retrospective studies and case reports. This review aims to perform a critical analysis of the evidence regarding the role of BMs in GEP- and BP-NENs, focusing on the molecular mechanisms underlining the development of BMs, as well as clinical presentation, diagnosis, and treatment of BMs, in an attempt to provide suggestions that can be used in clinical practice.

The Mode-of-Action of Targeted Alpha Therapy Radium-223 as an Enabler for Novel Combinations to Treat Patients with Bone Metastasis

Bone metastasis is a common clinical complication in several cancer types, and it causes a severe reduction in quality of life as well as lowering survival time. Bone metastases proceed through a vicious self-reinforcing cycle that can be osteolytic or osteoblastic in nature. The vicious cycle is characterized by cancer cells residing in bone releasing signal molecules that promote the differentiation of osteoclasts and osteoblasts either directly or indirectly. The increased activity of osteoclasts and osteoblasts then increases bone turnover, which releases growth factors that benefit metastatic cancer cells. In order to improve the prognosis of patients with bone metastases this cycle must be broken. Radium-223 dichloride (radium-223), the first targeted alpha therapy (TAT) approved, is an osteomimetic radionuclide that is incorporated into bone metastases where its high-linear energy transfer alpha radiation disrupts both the activity of bone cells and cancer cells. Therefore, radium-223 treatment has been shown preclinically to directly affect cancer cells in both osteolytic breast cancer and osteoblastic prostate cancer bone metastases as well as to inhibit the differentiation of osteoblasts and osteoclasts. Clinical studies have demonstrated an increase in survival in patients with metastatic castration-resistant prostate cancer. Due to the effectiveness and low toxicity of radium-223, several novel combination treatment strategies are currently eliciting considerable research interest.

Interleukin-6 Interweaves the Bone Marrow Microenvironment, Bone Loss, and Multiple Myeloma

The immune system is strongly linked to the maintenance of healthy bone. Inflammatory cytokines, specifically, are crucial to skeletal homeostasis and any dysregulation can result in detrimental health complications. Interleukins, such as interleukin 6 (IL-6), act as osteoclast differentiation modulators and as such, must be carefully monitored and regulated. IL-6 encourages osteoclastogenesis when bound to progenitors and can cause excessive osteoclastic activity and osteolysis when overly abundant. Numerous bone diseases are tied to IL-6 overexpression, including rheumatoid arthritis, osteoporosis, and bone-metastatic cancers. In the latter, IL-6 can be released with growth factors into the bone marrow microenvironment (BMM) during osteolysis from bone matrix or from cancer cells and osteoblasts in an inflammatory response to cancer cells. Thus, IL-6 helps create an ideal microenvironment for oncogenesis and metastasis. Multiple myeloma (MM) is a blood cancer that homes to the BMM and is strongly tied to overexpression of IL-6 and bone loss. The roles of IL-6 in the progression of MM are discussed in this review, including roles in bone homing, cancer-associated bone loss, disease progression and drug resistance. MM disease progression often includes the development of drug-resistant clones, and patients commonly struggle with reoccurrence. As such, therapeutics that specifically target the microenvironment, rather than the cancer itself, are ideal and IL-6, and its myriad of downstream signaling partners, are model targets. Lastly, current and potential therapeutic interventions involving IL-6 and connected signaling molecules are discussed in this review.

Exosomal Release of L-Plastin by Breast Cancer Cells Facilitates Metastatic Bone Osteolysis

Bone metastasis from breast and prostate carcinomas is facilitated by activation of bone-resorbing osteoclasts. Using proteomics approaches, we have identified peroxiredoxin-4 (PRDX4) as a cancer-secreted mediator of osteoclastogenesis. We now report characterization of L-plastin in the conditioned media (CM) of MDA-MB-231 human breast cancer cells using immunoblotting and mass spectrometry. The osteoclastogenic potential of MDA-MB-231 CM with siRNA-silenced L-plastin was significantly reduced. L-plastin was detected in cancer-derived exosomes, and inhibition of exosomal release significantly decreased the osteoclastogenic capacity of MDA-MB-231 CM. When added to osteoclast precursors primed with RANKL for 2 days, recombinant L-plastin induced calcium/NFATc1-mediated osteoclastogenesis to the levels similar to continuous treatment with RANKL. Using shRNA, we generated MDA-MB-231 cells lacking L-plastin, PRDX4, or both and injected these cell populations intratibially in CD-1 immunodeficient mice. Micro-CT and histomorphometric analysis demonstrated a complete loss of osteolysis when MDA-MB-231 cells lacking both L-plastin and PRDX4 were injected. A meta-analysis established an increase in L-plastin and PRDX4 mRNA expression in numerous human cancers, including breast and prostate carcinomas. This study demonstrates that secreted L-plastin and PRDX4 mediate osteoclast activation by human breast cancer cells.

Lysophosphatidic acid enhances breast cancer cells-mediated osteoclastogenesis

Lysophosphatidic acid (LPA) is known to play a critical role in breast cancer metastasis to bone. In this study, we tried to investigate any role of LPA in the regulation of osteoclastogenic cytokines from breast cancer cells and the possibility of these secretory factors in affecting osteoclastogenesis. Effect of secreted cytokines on osteoclastogenesis was analyzed by treating conditioned media from LPA-stimulated breast cancer cells to differentiating osteoclasts. Result demonstrated that IL-8 and IL-11 expression were upregulated in LPA-treated MDA-MB-231 cells. IL-8 was induced in both MDA-MB-231 and MDA-MB-468, however, IL-11 was induced only in MDA-MB-231, suggesting differential LPARs participation in the expression of these cytokines. Expression of IL-8 but not IL-11 was suppressed by inhibitors of PI3K, NFkB, ROCK and PKC pathways. In the case of PKC activation, it was observed that PKCδ and PKCμ might regulate LPA-induced expression of IL-11 and IL-8, respectively, by using specific PKC subtype inhibitors. Finally, conditioned Medium from LPA-stimulated breast cancer cells induced osteoclastogenesis. In conclusion, LPA induced the expression of osteolytic cytokines (IL-8 and IL-11) in breast cancer cells by involving different LPA receptors. Enhanced expression of IL-8 by LPA may be via ROCK, PKCu, PI3K, and NFkB signaling pathways, while enhanced expression of IL-11 might involve PKCδ signaling pathway. LPA has the ability to enhance breast cancer cells-mediated osteoclastogenesis by inducing the secretion of cytokines such as IL-8 and IL-11.

Inhibitory effects of low intensity pulsed ultrasound on osteoclastogenesis induced in vitro by breast cancer cells

Background

Bone tissue is one of the main sites for breast metastasis; patients diagnosed with advanced breast cancer mostly develop bone metastasis characterized by severe osteolytic lesions, which heavily influence their life quality. Low Intensity Pulsed Ultrasound (LIPUS) is a form of mechanical energy able to modulate various molecular pathways both in cancer and in health cells.

The purpose of the present study was to evaluate for the first time, the ability of LIPUS to modulate osteolytic capability of breast cancer cells.

Methods

Two different approaches were employed: a) Indirect method -conditioned medium obtained by MDA-MB-231 cell line treated or untreated with LIPUS was used to induce osteoclast differentiation of murine macrophage Raw264.7 cell line; and b) Direct method -MDA-MB-231 were co-cultured with Raw264.7 cells and treated or untreated with LIPUS.

Results

LIPUS treatment impaired MDA-MB-231 cell dependentosteoclast differentiation and produced a reduction of osteoclast markers such as Cathepsin K, Matrix Metalloproteinase 9 and Tartrate Resistant Acid Phosphatase, suggesting its role as an effective and safe adjuvant in bone metastasis management.

Conclusion

LIPUS treatment could be a good and safety therapeutic adjuvant in osteolyitic bone metastasis not only for the induction properties of bone regeneration, but also for the reduction of osteolysis.

Regulation of Osteoclast Differentiation by Cytokine Networks

Cytokines play a pivotal role in maintaining bone homeostasis. Osteoclasts (OCs), the sole bone resorbing cells, are regulated by numerous cytokines. Macrophage colony-stimulating factor and receptor activator of NF-κB ligand play a central role in OC differentiation, which is also termed osteoclastogenesis. Osteoclastogenic cytokines, including tumor necrosis factor-α, IL-1, IL-6, IL-7, IL-8, IL-11, IL-15, IL-17, IL-23, and IL-34, promote OC differentiation, whereas anti-osteoclastogenic cytokines, including interferon (IFN)-α, IFN-β, IFN-γ, IL-3, IL-4, IL-10, IL-12, IL-27, and IL-33, downregulate OC differentiation. Therefore, dynamic regulation of osteoclastogenic and anti-osteoclastogenic cytokines is important in maintaining the balance between bone-resorbing OCs and bone-forming osteoblasts (OBs), which eventually affects bone integrity. This review outlines the osteoclastogenic and anti-osteoclastogenic properties of cytokines with regard to osteoimmunology, and summarizes our current understanding of the roles these cytokines play in osteoclastogenesis.

The dual regulatory role of miR-204 in cancer

MicroRNAs (miRNAs) are a group of endogenous, small (about 22 nucleotides) non-coding RNAs which negatively regulate gene expressions. As one of them, miR-204 originates from the sixth intron of the transient receptor potential melastatin 3 (TRPM3) gene. Therefore, expression of miR-204 is under the control of the TRPM3 promoter and regulated by genetic and epigenetic mechanisms. miR-204 has been found to play the important roles in development of eyes and adipogenesis. Its pathological functions have been observed in a few diseases including pulmonary arterial hypertension, diabetes, and various types of cancers. It is believed that miR-204 acts as a tumor-suppressor via promoting apoptosis, conferring the resistance of cancer cells to chemotherapy, and suppressing the self-renewal of cancer stem cells (CSCs) and the epithelial to mesenchymal transition (EMT). Expression of miR-204 is repressed by its targets XRN1 and TRKB in prostate cancer and endometrial carcinoma, respectively; therefore, they establish an oncogenic feedback loops that play an important role promoting development of cancer. In this review, we summarize our current knowledge regarding miR-204, including its expression, regulation and biological functions, especially focusing our discussion on its role in tumor development and tumor progression.

The role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding

BACKGROUND

Human pregnancy requires robust hemostasis to prevent hemorrhage during extravillous trophoblast (EVT) invasion of the decidualized endometrium, modification of spiral arteries and post-partum processes. However, decidual hemorrhage (abruption) can occur throughout pregnancy from poorly transformed spiral arteries, causing fetal death or spontaneous preterm birth (PTB), or it can promote the aberrant placentation observed in intrauterine growth restriction (IUGR) and pre-eclampsia; all leading causes of perinatal or maternal morbidity and mortality. In non-fertile cycles, the decidua undergoes controlled menstrual bleeding. Abnormal uterine bleeding (AUB) accompanying progestin-only, long-acting, reversible contraception (pLARC) accounts for most discontinuations of these safe and highly effective agents, thereby contributing to unwanted pregnancies and abortion. The aim of this study was to investigate the role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding.

METHODS

We conducted a critical review of the literature arising from PubMed searches up to December 2015, regarding in situ and in vitro expression and regulation of several specific proteins involved in uterine hemostasis in decidua and cycling endometrium. In addition, we discussed clinical and molecular mechanisms associated with pLARC-induced AUB and pregnancy complications with abruptions, chorioamnionitis or pre-eclampsia.

RESULTS

Progestin-induced decidualization of estradiol-primed human endometrial stromal cells (HESCs) increases in vivo and in vitro expression of tissue factor (TF) and type-1 plasminogen activator inhibitor (PAI-1) while inhibiting plasminogen activators (PAs), matrix metalloproteinases (MMPs), and the vasoconstrictor, endothelin-1 (ET-1). These changes in decidual cell-derived regulators of hemostasis, fibrinolysis, extracellular matrix (ECM) turnover, and vascular tone prevent hemorrhage during EVT invasion and vascular remodeling. In non-fertile cycles, progesterone withdrawal reduces TF and PAI-1 while increasing PA, MMPs and ET-1, causing menstrual-associated bleeding, fibrinolysis, ECM degradation and ischemia. First trimester decidual hemorrhage elicits later adverse outcomes including pregnancy loss, pre-eclampsia, abruption, IUGR and PTB. Decidual hemorrhage generates excess thrombin that binds to decidual cell-expressed protease-activated receptors (PARs) to induce chemokines promoting shallow placentation; such bleeding later in pregnancy generates thrombin to down-regulate decidual cell progesterone receptors and up-regulate cytokines and MMPs linked to PTB. Endometria of pLARC users display ischemia-induced excess vasculogenesis and progestin inhibition of spiral artery vascular smooth muscle cell proliferation and migration leading to dilated fragile vessels prone to bleeding. Moreover, aberrant TF-derived thrombin signaling also contributes to the pathogenesis of endometriosis via induction of angiogenesis, inflammation and cell survival.

CONCLUSION

Perivascular decidualized HESCs promote endometrial hemostasis during placentation yet facilitate menstruation through progestational regulation of hemostatic, proteolytic, and vasoactive proteins. Pathological endometrial hemorrhage elicits excess local thrombin generation, which contributes to pLARC associated AUB, endometriosis and adverse pregnancy outcomes through several biochemical mechanisms.

Molecular alterations that drive breast cancer metastasis to bone

Epithelial cancers including breast and prostate commonly progress to form incurable bone metastases. For this to occur, cancer cells must adapt their phenotype and behaviour to enable detachment from the primary tumour, invasion into the vasculature, and homing to and subsequent colonisation of bone. It is widely accepted that the metastatic process is driven by the transformation of cancer cells from a sessile epithelial to a motile mesenchymal phenotype through epithelial-mesenchymal transition (EMT). Dissemination of these motile cells into the circulation provides the conduit for cells to metastasise to distant organs. However, accumulating evidence suggests that EMT is not sufficient for metastasis to occur and that specific tissue-homing factors are required for tumour cells to lodge and grow in bone. Once tumour cells are disseminated in the bone environment, they can revert into an epithelial phenotype through the reverse process of mesenchymal-epithelial transition (MET) and form secondary tumours. In this review, we describe the molecular alterations undertaken by breast cancer cells at each stage of the metastatic cascade and discuss how these changes facilitate bone metastasis.

Autoimmune pulmonary alveolar proteinosis co-existing with breast cancer: a case report

Introduction

Pulmonary alveolar proteinosis is a rare pulmonary disease characterized by excessive alveolar accumulation of surfactant due to defective alveolar clearance by macrophages. There are only a few published case reports of pulmonary alveolar proteinosis occurring in association with solid cancers. To the best of our knowledge, there are no previously reported cases of pulmonary alveolar proteinosis associated with breast cancer.

Case presentation

A 48-year-old Asian woman, a nonsmoker, presented to our institution with a right breast mass. Biopsy examination of the lesion revealed scirrhous carcinoma. A chest computed tomography scan for metastases showed abnormal shadows in both upper lung fields. As a result of flexible fiberscopic bronchoscopy, this patient was diagnosed as having pulmonary alveolar proteinosis. This case was categorized as autoimmune pulmonary alveolar proteinosis due to the positive anti-granulocyte-macrophage colony-stimulating factor antibody. Pulmonary alveolar proteinosis decreased gradually after mastectomy.

Conclusions

The present case involved the coincident occurrence of autoimmune pulmonary alveolar proteinosis with breast cancer; breast cancer may be a factor during pulmonary alveolar proteinosis development.

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.

Breast cancer cells induce osteolytic bone lesions in vivo through a reduction in osteoblast activity in mice

Bone metastases are severely debilitating and have a significant impact on the quality of life of women with metastatic breast cancer. Treatment options are limited and in order to develop more targeted therapies, improved understanding of the complex mechanisms that lead to bone lesion development are warranted. Interestingly, whilst prostate-derived bone metastases are characterised by mixed or osteoblastic lesions, breast-derived bone metastases are characterised by osteolytic lesions, suggesting unique regulatory patterns. This study aimed to measure the changes in bone formation and bone resorption activity at two time-points (18 and 36 days) during development of the bone lesion following intratibial injection of MDA-MB-231 human breast cancer cells into the left tibiae of Severely Combined Immuno-Deficient (SCID) mice. The contralateral tibia was used as a control. Tibiae were extracted and processed for undecalcified histomorphometric analysis. We provide evidence that the early bone loss observed following exposure to MDA-MB-231 cells was due to a significant reduction in mineral apposition rate, rather than increased levels of bone resorption. This suggests that osteoblast activity was impaired in the presence of breast cancer cells, contrary to previous reports of osteoclast-dependent bone loss. Furthermore mRNA expression of Dickkopf Homolog 1 (DKK-1) and Noggin were confirmed in the MDA-MB-231 cell line, both of which antagonise osteoblast regulatory pathways. The observed bone loss following injection of cancer cells was due to an overall thinning of the trabecular bone struts rather than perforation of the bone tissue matrix (as measured by trabecular width and trabecular separation, respectively), suggesting an opportunity to reverse the cancer-induced bone changes. These novel insights into the mechanisms through which osteolytic bone lesions develop may be important in the development of new treatment strategies for metastatic breast cancer patients.

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.

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.

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.

The binding characteristics of a cyclic nonapeptide, c(CGRRAGGSC), in LNCaP human prostate cancer cells

Previous studies have demonstrated that interleukin-11 (IL-11) and the IL-11 receptor (IL-11R) are associated with the regulation of tumor progression and may play a significant role in bone metastases. The nonapeptide structure c(CGRRAGGSC) is a phage display-selected IL-11 mimic, which binds to IL-11R. The aim of this study is to investigate the binding characteristics of a cyclic nonapeptide c(CGRRAGGSC) in LNCaP human prostate cancer cells. To investigate its binding and uptake effects, c(CGRRAGGSC) was labeled with a fluorescent dye, LSS670. The binding location of LSS670 cyclic nonapeptide in LNCaP cells was investigated by fluorescence microscopy. Flow cytometry was used to detect the fluorescence of LSS670-c(CGRRAGGSC) in LNCaP cells. The binding of LSS670-c(CGRRAGGSC) in LNCaP cells was inhibited by unlabeled cyclic nonapeptide, depending on the varying density of c(CGRRAGGSC) and different time points. The molecular probe bound to the LNCaP cell membrane and cytoplasm through fluorescence tracing. In the saturation experiments performed in vitro, the K(d) value was 3.2±0.02 nM and the B(max) value was 754±34 fmol/mg.pro. The 50% inhibiting concentration (IC(50)) was 6.31±0.12 nmol/l and the K(i) value was 2.11±0.14 nmol/l in competitive inhibition experiments. Our results suggest that c(CGRRAGGSC) is able to specifically bind to LNCaP cells through a receptor-mediated pathway.

Identification of microRNAs inhibiting TGF-β-induced IL-11 production in bone metastatic breast cancer cells

Development of bone metastases is dependent on the cancer cell-bone cell interactions in the bone microenvironment. Transforming growth factor β (TGF-β) is released from bone during osteoclastic bone resorption and induces production of osteolytic factors, such as interleukin 11 (IL-11), in breast cancer cells. IL-11 in turn increases osteolysis by stimulating osteoclast function, launching a vicious cycle of cancer growth and bone destruction. We aimed to identify and functionally characterize microRNAs (miRNAs) that mediate the bone metastatic process, focusing on miRNAs that regulate the TGF-β induction of IL-11. First, we profiled the expression of 455 miRNAs in a highly bone metastatic MDA-MB-231(SA) variant as compared to the parental MDA-MB-231 breast cancer cell line and found 16 miRNAs (3.5%) having a >3-fold expression difference between the two cell types. We then applied a cell-based overexpression screen with Pre-miRNA constructs to functionally identify miRNAs regulating TGF-β-induced IL-11 production. This analysis pinpointed miR-204, miR-211, and miR-379 as such key regulators. These miRNAs were shown to directly target IL11 by binding to its 3′ UTR. MiR-379 also inhibited Smad2/3/4-mediated transcriptional activity. Gene expression analysis of miR-204 and miR-379-transfected cells indicated that these miRNAs downregulated the expression of several genes involved in TGF-β signaling, including prostaglandin-endoperoxide synthase 2 (PTGS2). In addition, there was a significant correlation between the genes downregulated by miR-379 and a set of genes upregulated in basal subtype of breast cancer. Taken together, the functional evidence and clinical correlations imply novel mechanistic links between miRNAs and the key steps in the bone metastatic process in breast cancer, with potential clinical relevance.

Increased osteocyte death in multiple myeloma patients: role in myeloma-induced osteoclast formation

The involvement of osteocytes in multiple myeloma (MM)-induced osteoclast (OCL) formation and bone lesions is still unknown. Osteocytes regulate bone remodelling at least partially, as a result of their cell death triggering OCL recruitment. In this study, we found that the number of viable osteocytes was significantly smaller in MM patients than in healthy controls, and negatively correlated with the number of OCLs. Moreover, the MM patients with bone lesions had a significantly smaller number of viable osteocytes than those without, partly because of increased apoptosis. These findings were further confirmed by ultrastructural in vitro analyses of human preosteocyte cells cocultured with MM cells, which showed that MM cells increased preosteocyte death and apoptosis. A micro-array analysis showed that MM cells affect the transcriptional profiles of preosteocytes by upregulating the production of osteoclastogenic cytokines such as interleukin (IL)-11, and increasing their pro-osteoclastogenic properties. Finally, the osteocyte expression of IL-11 was higher in the MM patients with than in those without bone lesions. Our data suggest that MM patients are characterized by a reduced number of viable osteocytes related to the presence of bone lesions, and that this is involved in MM-induced OCL formation.

Breast cancer at bone metastatic sites: recent discoveries and treatment targets

Breast carcinoma is the most common cancer of women. Bones are often involved with breast carcinoma metastases with the resulting morbidity and reduced quality of life. Breast cancer cells arriving at bone tissues mount supportive microenvironment by recruiting and modulating the activity of several host tissue cell types including the specialized bone cells osteoblasts and osteoclasts. Pathologically activated osteoclasts produce osteolytic lesions associated with bone pain, pathological fractures, cord compression and other complications of metastatic breast carcinoma at bone. Over the last decade there has been enormous growth of knowledge in the field of osteoclasts biology both in the physiological state and in the tumor microenvironment. This knowledge allowed the development and implementation of several targeted therapeutics that expanded the armamentarium of the oncologists dealing with the metastases-associated osteolytic disease. While the interactions of cancer cells with resident bone cells at the established metastatic gross lesions are well-studied, the preclinical events that underlie the progression of disseminated tumor cells into micrometastases and then into clinically-overt macrometastases are just starting to be uncovered. In this review, we discuss the established information and the most recent discoveries in the pathogenesis of osteolytic metastases of breast cancer, as well as the corresponding investigational drugs that have been introduced into clinical development.

Effects of medroxyprogesterone acetate on gene expression in myometrial explants from pregnant women

CONTEXT

Progesterone is important physiologically and therapeutically to maintain uterine quiescence during pregnancy, in part through controlling myometrial gene expression.

OBJECTIVE

The objective of the study was to use expression microarray and quantitative reverse transcriptase-PCR (qRT-PCR) validation to determine the changes in gene expression induced by prolonged exposure of human myometrium to a synthetic progestogen.

DESIGN

Myometrial explants, obtained at elective cesarean section (n=9), were maintained in culture, under 0.6 g tension, for 65 h in the presence of medroxyprogesterone acetate (100 nm) or vehicle. Expression array was performed using Illumina beadchip arrays. Approximately 30% of differentially expressed transcripts were validated in biological replicates (n=10) by qRT-PCR.

RESULTS

The 114 significantly regulated transcripts were significantly enriched in inflammatory response (P=0.00001), growth factor activity (P=0.0004), and cytokine activity genes (P=0.008). Thirty-four transcripts were validated using qRT-PCR in explants obtained from 10 further women. There was very close agreement in the fold changes obtained by array and qRT-PCR (r2=0.9, P<0.0001). We confirmed significant down-regulation of a number of genes that have been well characterized as progesterone sensitive (IL-1B, IL-6, PTGS2, and GJA1). However, the top and sixth most down-regulated transcripts encoded two cytokines, IL-11 and IL-24, respectively, not previously implicated in mediating the effects of progesterone in myometrium. Both were validated by qRT-PCR (4.3- and 2.2-fold down-regulated, both P<0.001).

CONCLUSIONS

Medroxyprogesterone acetate controls expression of multiple genes in myometrium, including many that have not previously been characterized as progestogen regulated in this tissue, including IL-11 and IL-24. It is plausible that proteins encoded by some of these genes may have important but as yet uncharacterized effects in controlling human parturition.

The dual role of IL-6-type cytokines on bone remodeling and bone tumors

Many factors such as vitamins, hormones and cytokines, control bone metabolism and remodeling. Cytokines of the interleukin-6 family, by acting on bone cells (i.e. osteoblasts and osteoclasts), have an important role in the bone tissue but they recently appeared as double-edged swords. They sustain bone formation but they can also drive bone loss in various osteolytic pathologies. Similarly, development of bone cancers can be either prevented or enhanced by these cytokines, depending on the cell type, the stage of the tumor and the bone environment. This dual effect is also apparent at the level of the signal transducer and activator of transcription and the mitogen-activated protein kinases, the two main signaling pathways that mediate opposite effects in bone cells.

Osteoclast precursors acquire sensitivity to breast cancer derived factors early in differentiation

The development of osteolytic breast cancer bone metastases relies on the ability of tumor cells to stimulate the formation of bone-resorbing osteoclasts. We have studied the effects of soluble factors produced by MDA-MB-231 breast carcinoma cells on osteoclast formation from human monocytic precursors and RAW 264.7 monocytic cells. Although factors produced by breast cancer cells were ineffective in inducing osteoclast formation from monocytes, priming with RANKL for 1-3 days dramatically increased receptiveness of osteoclast precursors to cancer-derived factors, which enhanced osteoclast formation 2-3 fold in the absence of supporting cell types. Osteoclasts formed by exposure to cancer factors expressed proteases critical for bone resorption, cathepsin K and matrix metalloproteinase 9, and were capable of resorbing calcified matrices. Expression of key osteoclastogenic transcription factor NFATc1 in osteoclast precursors was dramatically increased by short treatment with RANKL. NFATc1 was localized in the nuclei of primed osteoclast precursors when RANKL was present; however removal of RANKL led to rapid nuclear export of NFATc1. Cancer-derived factors were able to substitute for RANKL in supporting nuclear localization of NFATc1. Using neutralizing antibodies against TGFbeta, and a kinase inhibitor targeting the TGFbeta type I receptor, we identified TGFbeta as a permissive factor, required for the effects of breast cancer cells on NFATc1 nuclear accumulation and osteoclast formation. Our data suggest that, during differentiation, osteoclast precursors acquire the competency to respond to factors secreted by breast cancer cells, which may serve to promote tumor growth at skeletal sites undergoing active bone turnover.

Cyclooxygenase-2 expression in primary breast cancers predicts dissemination of cancer cells to the bone marrow

PURPOSE

Cyclooxygenase-2 (COX2) plays a role in breast cancer progression at various stages starting from pre-malignant phenotype to clinical metastasis. Breast cancer metastasizes commonly to the bone and preclinical studies suggest an involvement of COX2 in this process. Detection of disseminated tumor cells in the bone marrow of patients at the time of surgery correlates with the subsequent development of clinical bone metastasis. Therefore, to investigate whether COX2 is important for breast cancer metastasis in humans, we analyzed COX2 protein expression by immunostaining of primary tumors from 112 operable stages I, II, or III patients and determined its correlation with bone marrow micrometastasis (BMM).

METHODS

We detected COX2 protein in primary tumors by immunostaining with a monoclonal antibody, and tumor cells present in the bone marrow by immunostaining for epithelial cytokeratins and by morphological criteria.

RESULTS

COX2 expression in primary breast cancer correlated with BMM in a highly statistically significant manner (P = 0.006). Our statistical analyses of correlations of the COX2 positivity in primary tumor with other clinically relevant indicators revealed that COX2 positivity correlates with high nuclear grade (P = 0.0004). Furthermore, we were able to detect COX2 protein in BMM by immunostaining.

CONCLUSIONS

These studies indicate that COX2 produced in primary breast cancer cells may be vital to the initial development of BMM that may subsequently lead to osteolytic bone metastases in patients with breast cancer, and that COX2 inhibitors may be useful in halting this process.

Molecular biology of bone metastasis

Metastasis is a final stage of tumor progression. Breast and prostate cancer cells preferentially metastasize to bone, wherein they cause incurable osteolytic and osteoblastic lesions. The bone matrix is rich in factors, such as transforming growth factor-beta and insulin-like growth factors, which are released into the tumor microenvironment by osteolysis. These factors stimulate the growth of tumor cells and alter their phenotype, thus promoting a vicious cycle of metastasis and bone pathology. Physical factors within the bone microenvironment, including low oxygen levels, acidic pH, and high extracellular calcium concentrations, may also enhance tumor growth. These elements of the microenvironment are potential targets for chemotherapeutic intervention to halt tumor growth and suppress bone metastasis.

The roles of proteolytic enzymes in the development of tumour-induced bone disease in breast and prostate cancer

Tumour-induced bone disease is a common clinical feature of advanced breast and prostate cancer and is associated with considerable morbidity for the affected patients. Our understanding of the molecular mechanisms underlying the development of bone metastases is incomplete, but proteolytic enzymes are implicated in a number of processes involved in both bone metastasis and in normal bone turnover, including matrix degradation, cell migration, angiogenesis, tumour promotion and growth factor activation. Malignant as well as non-malignant cells in the primary and secondary sites express these enzymes, the activity of which may be regulated by soluble factors, cell- or matrix-associated components, as well as a number of cell signalling pathways. A number of secreted and cell surface-associated proteolytic enzymes are implicated in tumour-induced bone disease, including the matrix metalloproteinases, lysosomal cysteine proteinases and plasminogen activators. This review will introduce the role of proteolytic enzymes in normal bone turnover and give an overview of the studies in which their involvement and regulation in the development of bone metastases in breast and prostate cancer has been described. The results from trials involving protease inhibitors in clinical development will also be briefly discussed.

Tumor metastasis to bone

Establishment of skeletal metastasis involves bidirectional interactions between the tumor cell and the cellular elements in the bone microenvironment. A better understanding of the pathophysiology of bone metastasis will be critical in developing the means to prevent bone metastasis or inhibit its progression. The receptor activator of nuclear factor-kappaB (RANK)/RANK ligand pathway has emerged as the key pathway regulating osteolysis in skeletal metastasis. A number of candidate factors, including the Wnt (wingless int) proteins, endothelin-1, and bone morphogenetic proteins, have been implicated in the establishment of osteoblastic metastasis. The complex nature of tumor-bone microenvironment interactions and the presence of multiple pathways that lead to bone metastasis suggests that simultaneous targeting of these pathways in the metastatic cascade are required for effective treatment. This review discusses current understanding of the pathophysiologic mechanisms that underlie the establishment of bone metastasis and potential molecular therapeutic strategies for prevention and treatment of bone metastasis.

Metastasis: the seed and soil theory gains identity

The metastatic spread of tumor cells to distant sites represents the major cause of cancer-related deaths. Cancer metastasis involves a series of complex interactions between tumor cells and microenvironment that influence its biological effectiveness and facilitate tumor cell arrest to distant organs. More than a century since Paget developed the theory of seed and soil, the enigma of tissue specificity observed in metastatic colonization of tumor cells begins to unfold itself. The advent of new technologies has led to the discovery of novel molecules and pathways that confer metastasis-associated properties to the cancer cells, mediating organ specificity and unique genetic signatures have been developed using microarray studies. Future clinical studies and new antimetastatic compounds aiming to improve survival of patients with metastasis will most probably be based on these signatures. This review summarizes the plethora of old and new molecules that are strongly correlated with organ-specific metastases and which provide now an identity to the theory of seed and soil.

Rutile and titanium particles differentially affect the production of osteoblastic local factors

Titanium and its alloys are widely used as implant materials for dental and orthopaedic applications. To improve their wear and corrosion resistance, several surface modifications that give rise to an outer ceramic layer of rutile have been developed. It is expected that after a long period of functional loading, rutile debris will arise from these modified surfaces. We have compared the in vitro biocompatibility of subcytotoxic doses of rutile and titanium particles of phagocytosable size in primary cultures of human osteoblasts. Particles were visualized using a spectral confocal microscope by reflection. Both types of particles aggregated in the culture media and were efficiently internalized by osteoblasts as agglomerates. Treatment of isolated cultures of osteoblasts with rutile particles stimulated the release of IL-6, PGE2, and GM-CSF to a lesser extent than titanium. The influence of macrophages on the particle-induced stimulation of those local factors was analyzed by coculturing TPA-differentiated THP-1 cells with osteoblasts. Under these conditions, levels of IL-6 and PGE2 after treatment of cocultured osteoblasts with rutile particles were lower than after exposure to titanium. These results indicate that rutile debris shows a lower bioreactivity than titanium when tested in cultures of human osteoblasts and support the improved biocompatibility of titanium-based implants modified to create an outer layer of rutile on their surfaces.

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.

COX-2 involvement in breast cancer metastasis to bone

Cyclooxygenase-2 (COX-2) is expressed in 40% of human invasive breast cancers. Bone is the predominant site of metastasis in case of breast cancer. We investigated the role of COX-2 in a suitable mouse model of breast cancer metastasis to bone using the whole-body luciferase imaging of cancer cells. We provide several lines of evidence that COX-2 produced in breast cancer cells is important for bone metastasis in this model including (1) COX-2 transfection enhanced the bone metastasis of MDA-435S cells and (2) breast cancer cells isolated and cultured from the bone metastases produced significantly more prostaglandin E(2) (an important mediator of COX-2) than the parental injected cell populations of breast cancer cells. Next, we found that a COX-2 inhibitor, MF-tricyclic, inhibited bone metastasis caused by a bone-seeking clone both in prevention regimen (in which case mice started receiving MF-tricyclic 1 week before the injection of cancer cells) and in treatment regimen (in which case mice received MF-tricyclic after the development of bone metastasis). These studies indicate that COX-2 produced in breast cancer cells may be vital to the development of osteolytic bone metastases in patients with breast cancer, and that COX-2 inhibitors may be useful in halting this process.

NF-kappaB in breast cancer cells promotes osteolytic bone metastasis by inducing osteoclastogenesis via GM-CSF

Advanced breast cancers frequently metastasize to bone, resulting in osteolytic lesions, yet the underlying mechanisms are poorly understood. Here we report that nuclear factor-kappaB (NF-kappaB) plays a crucial role in the osteolytic bone metastasis of breast cancer by stimulating osteoclastogenesis. Using an in vivo bone metastasis model, we found that constitutive NF-kappaB activity in breast cancer cells is crucial for the bone resorption characteristic of osteolytic bone metastasis. We identified the gene encoding granulocyte macrophage-colony stimulating factor (GM-CSF) as a key target of NF-kappaB and found that it mediates osteolytic bone metastasis of breast cancer by stimulating osteoclast development. Moreover, we observed that the expression of GM-CSF correlated with NF-kappaB activation in bone-metastatic tumor tissues from individuals with breast cancer. These results uncover a new and specific role of NF-kappaB in osteolytic bone metastasis through GM-CSF induction, suggesting that NF-kappaB is a potential target for the treatment of breast cancer and the prevention of skeletal metastasis.

Cytokines in breast cancer

In recent decades many advances have occurred in the understanding of the role of cytokines in breast cancer. New signalling pathways of interleukin (IL)-1 family, IL-6, IL-11, IL-18, interferons (IFNs) and interferon regulatory factors 1 (IRF-1) and 2 (IRF-2) have been found within tumour microenvironments and in metastatic sites. Some cytokines (IL-1, IL-6, IL-11, TGFbeta) stimulate while others (IL-12, IL-18, IFNs) inhibit breast cancer proliferation and/or invasion. Similarly, high circulating levels of some cytokines seem to be favourable (soluble IL-2R) while others are unfavourable (IL-1beta, IL-6, IL-8, IL-10, IL-18, gp130) prognostic indicators. So far IL-2, IFNalpha, IFNbeta and occasionally IFNgamma, IL-6, IL-12 have been the cytokines used for anti tumour treatment of advanced breast cancer either to induce or increase hormone sensitivity and/or to stimulate cellular immunity. Disappointing results occurred in most trials; however, two long-term pilot studies suggest that IL-2 and IFNbeta, when used appropriately can have a positive effect on clinical benefit and overall survival of patients with minimal residual disease after chemotherapy or with disseminated disease controlled by conventional endocrine therapy.

Osteoprotegerin and bone mass in squamous cell head and neck cancer patients

Osteoprotegerin (OPG) is considered one of the main regulators of bone remodeling. Various patterns of serum OPG levels have been described in different types of tumors. We undertook this study to determine serum OPG levels in patients with squamous cell head and neck cancer (SCHNC), analyzing their relationship with other metabolic bone parameters and bone mineral density (BMD), as well as the possible influence of chemotherapy. Forty male patients with localized SCHNC were studied, and their results were compared with those of 40 healthy male controls. The type of treatment followed by each patient was noted. Age, weight, height, and lifestyle habits were recorded; and OPG, Ca(2+), intact parathyroid hormone (iPTH), 25-Hydroxyvitamin D (25OHD) and 1,25-Dihydroxyvitamin D (1,25(OH)(2)D), bone alkaline phosphatase, osteocalcin, and serum C-terminal cross-links telopeptide of type I collagen (ICTP) were determined. Dual-energy X-ray absorptiometry BMD at the lumbar spine, femoral neck, and hip was also measured. Serum OPG was higher in patients than in controls (91.7 +/- 25.8 vs. 77.2 +/- 26.3, P = 0.02). ICTP (a bone resorption marker) was 37% higher in patients (P = 0.007). Bone mass was lower in patients at the lumbar spine, femoral neck, and total hip. Lumbar spine Z-score showed a significant progressive decrease in controls, stage I-III patients, and stage IV patients. Logistic regression analysis showed a significant association between the disease and serum OPG levels, the odds ratio per standard deviation increase of this being 1.9 (95% confidence interval 1.1-3.8, P = 0.04) after adjusting for bone mass and ICTP serum levels, as well as for alcohol and smoking history. Adjustment for alcohol intake and tobacco use did not cancel out BMD differences between patients and controls. Patients with SCHNC show increased OPG serum levels, increased bone resorption, and decreased bone mass. The OPG rise appears to be unrelated to the BMD decrease, and the BMD decrease seems to be, at least in part, independent of smoking and drinking habits. No differences in either OPG or BMD were seen between patients with and without chemotherapy. Further studies are needed to clarify the mechanisms responsible for OPG and BMD changes in SCHNC.

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.