The development and function of the skeleton and bone metastases

Reduction of Osteoclastic Differentiation of Raw 264.7 Cells by EMF Exposure through TRPV4 and p-CREB Pathway

In this study, we investigated the effect of EMF exposure on the regulation of RANKL-induced osteoclast differentiation in Raw 264.7 cells. In the EMF-exposed group, the cell volume did not increase despite RANKL treatment, and the expression levels of Caspase-3 remained much lower than those in the RANKL-treated group. TRAP and F-actin staining revealed smaller actin rings in cells exposed to EMF during RANKL-induced differentiation, indicating that EMF inhibited osteoclast differentiation. EMF-irradiated cells exhibited reduced mRNA levels of osteoclastic differentiation markers cathepsin K (CTSK), tartrate-resistant acid phosphatase (TRAP), and matrix metalloproteinase 9 (MMP-9). Furthermore, as measured by RT-qPCR and Western blot, EMF induced no changes in the levels of p-ERK and p-38; however, it reduced the levels of TRPV4 and p-CREB. Overall, our findings indicate that EMF irradiation inhibits osteoclast differentiation through the TRPV4 and p-CREB pathway.

Fibroblast growth factors signaling in bone metastasis

Many solid tumors metastasize to bone, but only prostate cancer has bone as a single, dominant metastatic site. Recently, the FGF axis has been implicated in cancer progression in some tumors and mounting evidence indicate that it mediates prostate cancer bone metastases. The FGF axis has an important role in bone biology and mediates cell-to-cell communication. Therefore, we discuss here basic concepts of bone biology, FGF signaling axis, and FGF axis function in adult bone, to integrate these concepts in our current understanding of the role of FGF axis in bone metastases.

Zinc Promotes Osteoblast Differentiation in Human Mesenchymal Stem Cells Via Activation of the cAMP-PKA-CREB Signaling Pathway

The crucial trace element zinc stimulates osteogenesis in vitro and in vivo. However, the pathways mediating these effects remain poorly understood. This study aimed to investigate the effects of zinc on osteoblast differentiation in human bone marrow-derived mesenchymal stem cells (hBMSCs) and to identify the molecular mechanisms of these effects. In hBMSCs, zinc exposure resulted in a dose-dependent increase in osteogenesis and increased mRNA and protein levels of the master transcriptional factor RUNX2. Analyzing the upstream signaling pathways of RUNX2, we found that protein kinase A (PKA) signaling inhibition blocked zinc-induced osteogenic effects. Zinc exposure increased transcriptional activity and protein levels of phospho-CREB and enhanced translocation of phospho-CREB into the nucleus. These effects were reversed by H-89, a potent inhibitor of PKA. Moreover, zinc exposure led to dose-dependent increases in levels of intracellular cyclic adenosine monophosphate (cAMP). These findings indicate that zinc activates the PKA signaling pathway by triggering an increase in intracellular cAMP, leading to enhanced osteogenic differentiation in hBMSCs. Our results suggest that zinc exerts osteogenic effects in hBMSCs by activation of RUNX2 via the cAMP-PKA-CREB signaling pathway. Zinc supplementation may offer a promise as a potential pharmaceutical therapy for osteoporosis and other bone loss conditions.

Stromal cells in breast cancer as a potential therapeutic target

Breast cancer in the United States is the second most commonly diagnosed cancer in women. About 1 in 8 women will develop invasive breast cancer over the course of her lifetime and breast cancer remains the second leading cause of cancer-related death. In pursuit of novel therapeutic strategies, researchers have examined the tumor microenvironment as a potential anti-cancer target. In addition to neoplastic cells, the tumor microenvironment is composed of several critical normal cell types, including fibroblasts, vascular and lymph endothelial cells, osteoclasts, adipocytes, and immune cells. These cells have important roles in healthy tissue stasis, which frequently are altered in tumors. Indeed, tumor-associated stromal cells often contribute to tumorigenesis, tumor progression, and metastasis. Consequently, these host cells may serve as a possible target in anti-tumor and anti-metastatic therapeutic strategies. Targeting the tumor associated host cells offers the benefit that such cells do not mutate and develop resistance in response to treatment, a major cause of failure in cancer therapeutics targeting neoplastic cells. This review discusses the role of host cells in the tumor microenvironment during tumorigenesis, progression, and metastasis, and provides an overview of recent developments in targeting these cell populations to enhance cancer therapy efficacy.

TNF‑α and RANKL promote osteoclastogenesis by upregulating RANK via the NF‑κB pathway

Although tumor necrosis factor alpha (TNF-α) is known to serve a critical role in the pathogenesis of inflammatory osteolysis, the exact mechanisms underlying the effects of TNF-α on osteoclast recruitment and differentiation remain unclear. To investigate the mechanisms by which TNF-α influences osteoclast differentiation, mouse bone marrow-derived macrophages (BMMs) were used as osteoclast precursors, and osteoclastogenesis was induced by macrophage colony-stimulating factor and receptor activator of nuclear factor (NF)-κB ligand (RANKL) with or without TNF-α for 4 days. Then, NF-κB was inhibited using the inhibitor, BAY 11–7082. The results indicated that treatment with TNF-α alone did not induce osteoclastogenesis of BMMs. However, TNF-α in combination with RANKL dramatically stimulated the differentiation of osteoclasts and positively regulated the expression of mRNA markers of osteoclasts. Finally, treatment of BMMs with BAY 11–7082 prevented the formation of mature osteoclasts by BMMs treated with TNF-α only or with RANKL, as well as the upregulation of osteoclast marker genes. Therefore, although TNF-α does not induce osteoclastogenesis alone, it does work with RANKL to induce osteoclastic differentiation, and the NF-κB pathway may serve an important role in this process.

Malignancy mimicking bisphosphonate-associated osteonecrosis of the jaw: a case series and literature review

OBJECTIVE

Bisphosphonate-related osteonecrosis of the jaw (BONJ) is a common complication of bisphosphonate treatment that has been well documented over the past decade. Nevertheless, its pathogenesis is poorly understood, and treatment guidelines are based mostly on expert recommendations. Clinicians must be aware of malignancy mimicking BONJ, of which a few cases have been documented in the literature.

STUDY DESIGN

Three patients undergoing long-term treatment with intravenous bisphosphonates for malignant disease demonstrated the distinct diagnostic signs of BONJ. Surgical treatment was performed by resecting the affected bone. In all cases, histologic specimens were taken for analysis.

RESULTS

Histologic analysis of the bone specimen with surrounding soft tissue revealed necrotic bone with signs of inflammation, but also with cells of the underlying malignant disease.

CONCLUSIONS

Clinical and radiographic diagnosis of BONJ should be confirmed by histologic analysis in patients with underlying malignant disease.

Osteosarcoma of the jaws: case report on synchronous multicentric osteosarcomas

Research has shown that osteosarcomas display high potential for metastasis to the lungs, pleurae and bones. Mandible, on the other hand, is an uncommon site for metastatic tumour cell colonization. Nevertheless, a metastatic tumour to mandible might be the first indication of an undiscovered malignancy at a distant site. This case report presents a case of a 61-year-old female patient. An osteosarcoma metastasized to her mandible shortly after the curettage of her jaw cyst. Both the metastatic osteosarcoma and the jaw cyst were confirmed by pathology. Initially, bilateral well-defined radiolucent lesions were shown in her panoramic X-ray image. Also, the diagnosis of a dentigerous cyst was made, based on histology. Two months later, a mixed radiolucent-radio opaque mass, which was confirmed as an osteosarcoma by pathology later, occupied the site of the previously enucleated dentigerous cyst, in her right mandible. Then, an identical osteosarcoma was found in the left pelvis on further doing overall radiological and pathological examinations. The pathologic hypotheses, treatment modality and follow-up of this case have also been presented.

Zinc inhibits osteoclast differentiation by suppression of Ca2+-Calcineurin-NFATc1 signaling pathway

BACKGROUND

Zinc, an essential trace element, inhibits osteoclast differentiation in vitro and in vivo. The molecular mechanism for the inhibitory effect of zinc, however, is poorly understood. The purpose of this study was to investigate the effect of zinc and determine its molecular mechanism on receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis in mouse bone marrow-derived monocyte cells (BMMs) and RAW264.7 cells.

RESULTS

In BMMs, zinc treatment during osteoclast differentiation decreased RANKL-induced osteoclast formation in a dose-dependent manner. We show that zinc suppressed the mRNA levels of nuclear factor of activated T-cells, cytoplasmic 1 (Nfatc1). Zinc also accumulated phospho-Nfatc1 (p-Nfatc1) in the cytosol in a dose-dependent manner and inhibited the translocation of Nfatc1 to the nucleus in RAW264.7 cells. Zinc suppressed the activities of Nfatc1 in the nucleus without changing the activities of NF-κB in RAW264.7 cells. In contrast, calcineurin activity decreased in response to zinc but its protein level was unchanged. RANKL-induced Ca2+ oscillations were inhibited by zinc treatment, but phospho-phospholipase Cγ1 (p-PLCγ1), the upstream signaling molecule of Ca2+ oscillations, was unaffected. Moreover, a constitutively active form of Nfatc1 obviously rescued suppression of osteoclastogenesis by zinc.

CONCLUSIONS

Taken together, these results demonstrate for the first time that the inhibitory effect of zinc during osteoclastogesis is caused by suppressing the Ca2+-Calcineurin-NFATc1 signaling pathway. Thus, zinc may be a useful therapeutic candidate for the prevention of bone loss caused by NFATc1 activation in osteoclasts.

Bone metastasis in a novel breast cancer mouse model containing human breast and human bone

In practice, investigations for bone metastasis of breast cancer rely heavily on models in vivo. Lacking of such ideal model makes it difficult to study the whole process or accurate mechanism of each step of this metastatic disease. Development of xenograft mouse models has made great contributions in this area. Currently, the best animal model of breast cancer metastasizing to bone is NOD/SCID-hu models containing human bone, which makes it possible to let the breast cancer cells and the bone target of osteotropic metastasis be both of human origin. We have developed a novel mouse model containing both human bone and breast, and proved it functional and reliable. In this study, a set of human breast cancer cell line including MDA-MB-231, MDA-MB-231BO, MCF-7, ZR-75-1 and SUM1315 were characterized their osteotropism in this model. A specific cell line SUM1315 made species-specific bone metastasis, certifying the osteotropism-identification utility of the novel mouse model. Furthermore, gene expression and microRNA expression profiling analysis were done to the two SUM1315 derived sub lines isolated and purified from the orthotopic and metastatic xenograft. In addition, to demonstrate the disparity between the "spontaneous" and "forced" bone metastasis in mouse model, MDA-MB-231 cells were inoculated into both the human implants in this model simultaneously, and then primary cultured and profiling analyzed. Supported by overall results of profiling analyses, this study suggested the novel model was a useful tool for understanding, preventing and treating bone metastasis of breast cancer, meanwhile it had provided significant information for further investigations.

Oral metastasis of lung cancer. A challenge for the clinician

BACKGROUND

Bone metastases are a major cause of morbidity in cancer patients. Jawbone metastasis from lung cancer is a rare condition that may occur in the late state of the disease.

CASE REPORT

We report the case of a 74-year-old male presenting with an oral asymptomatic swelling that had grown substantially over the last 2 months. Biopsy and histological examination revealed the presence of a metastatic lung cell adenocarcinoma.

DISCUSSION

Although metastases to the oral cavity are uncommon, clinicians may play a crucial role also in the diagnosis of primary tumors.

Denosumab in breast cancer

Bone destruction is mediated by osteoclasts, whose formation, function, and survival requires the receptor activator of NF-kB ligand (RANKL). Denosumab is a fully human monoclonal antibody to RANKL, thereby inhibiting osteoclast-mediated bone destruction, and blocks the vicious cycle of cancer-mediated bone disease. In breast cancer patients with bone metastases, denosumab was superior to zoledronic acid in delaying time to first on-study skeletal-related event (SRE; HR=0.82; P=0.01 superiority) and time to first and subsequent on-study SREs (HR=0.77; P=0.001). Overall survival, disease progression, and serious adverse events were similar between groups.

Bone continuum of cancer

Many patients with solid tumors, especially breast and prostate cancers, and with multiple myeloma will develop bone metastases or other skeletal complications. The management of bone loss and symptomatic bone metastases is an important issue in the care and maintenance of quality of life for these patients. Morbidity caused by skeletal complications include pain (bone metastases are known as the most common cause of cancer-related pain), hypercalcemia, pathologic fracture, compression of the spinal cord or cauda equine, and spinal instability. Currently, the only Food and Drug Administration-approved therapy for metastatic bone disease is bisphosphonate therapy. A greater understanding of the biomolecular pathways that govern the bone continuum of cancer has helped identify novel targets for drug development. New therapeutic options are currently being investigated for the treatments of bone loss and symptomatic bone metastases. Some of these new drugs and modalities are in advanced stages of clinical development and may soon reach the clinic.

NPY regulation of bone remodelling

Neuropeptide Y (NPY), a classic neuronal regulator of energy homeostasis, is now also known to be involved in the control of bone homeostasis. Of the five known Y receptors through which the NPY family of ligands signals, the Y1 and Y2 receptors have so far been implicated in the control of osteoblast activity and thus bone formation. Analysis of brain specific NPY overexpressing and Y receptor knockout models has revealed a powerful anabolic pathway likely involving hypothalamic Y2 receptors and osteoblastic Y1 receptors. Furthering our understanding of the mechanisms underlying the involvement of the NPY system in the control of bone could lead to the development of therapies to improve bone mass in patients with diseases such as osteoporosis.

Selenium modifies the osteoblast inflammatory stress response to bone metastatic breast cancer

Breast cancer frequently metastasizes to the skeleton resulting in bone degradation due to osteoclast activation. Metastases also downregulate differentiation and the bone-rebuilding function of osteoblasts. Moreover, cancer cells trigger osteoblast inflammatory stress responses. Pro-inflammatory mediators such as interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), expressed by osteoblasts (MC3T3-E1) stimulated with human breast cancer cell (MDA-MB-231) conditioned medium, are pivotal to osteoclast activation and metastasis. Given that these genes are regulated by nuclear factor-kappaB (NF-kappaB), a redox-sensitive transcription factor, we hypothesized that selenium (Se) could abrogate the inflammatory response to metastatic breast cancer cells by modulating NF-kappaB. Caffeic acid phenethyl ester and parthenolide inhibited NF-kappaB activation, as seen by gel shift assays and immunoblotting for p65 in nuclear fractions, as well as decreased production of IL-6 and MCP-1. Supplementation of MC3T3-E1 with methylseleninic acid (MSA) (0.5 microM to 4 microM) reduced the activation of NF-kappaB leading to a decrease in IL-6, MCP-1, COX-2 and iNOS in response to MDA-MB-231 conditioned medium. Addition of MSA to osteoblasts for as little as 15 min suppressed activation of NF-kappaB suggesting that short-lived active metabolites might be involved. However, brief exposure to MSA also brought about an increase in selenoprotein glutathione peroxidase 1. In summary, our data indicate that the osteoblast response to metastatic breast cancer cells is regulated by NF-kappaB activation, which can be effectively suppressed by MSA either through short-lived active metabolites and/or selenoproteins. Thus, Se supplementation may prevent the osteoblast inflammatory response or dampen the vicious cycle established when breast cancer cells, osteoblasts and osteoclasts interact.

Pleiotropic functional properties of androgen receptor mutants in prostate cancer

The androgen receptor (AR) signaling pathway plays an important role during the development of the normal prostate gland, but also during the progression of prostate cancer on androgen ablation therapy. Mutations in the AR gene emerge to keep active the AR signaling pathway and to support prostate cancer cells growth and survival despite the low levels of circulating androgens. Indeed, mutations affecting the ligand binding domain (LBD) of the AR have been shown to generate so-called "promiscuous" receptors that present widened ligand specificity and allow the stimulation of these receptors by a larger spectrum of endogenous hormones. Another class of mutations, arising in the amino-terminal domain (NTD) of the receptor, modulate AR interactions with coregulators involved in cell proliferation regulation. Besides characteristics of these well-known types of mutations, the properties of other classes of AR mutants recently described in prostate cancer are currently under investigation. Most interestingly, in addition to their potential role in the mechanisms which allow prostate cancer cells to escape androgen ablation therapy, data suggest that certain AR mutations are present early in the natural history of the disease and may play a role in many aspects of prostate cancer progression. Surprisingly, singular truncated AR devoid of their carboxy-terminal end (CTE) region seem to exert specific paracrine effects and to induce a clonal cooperation with neighboring prostate cancer cells, which may facilitate both the invasion and metastasis processes. In this article, we review the functional properties of different classes of AR mutants and their potential impact on the natural history of prostate cancer. Hum Mutat 0, 1-14, 2008. (c) 2008 Wiley-Liss, Inc.

Matrix metalloproteinase-1 promotes breast cancer angiogenesis and osteolysis in a novel in vivo model

Matrix metalloproteinase-1 (MMP-1) is critical for mediating breast cancer metastasis to bone. We investigated the role of MMP-1 in breast cancer invasion of soft tissues and bone using human MDA MB-231 breast cancer cells stably transfected with shRNAs against MMP-1 and a novel murine model of bone invasion. MMP-1 produced by breast cancer cells with control shRNA facilitated invasion of tumors into soft tissue in vivo, which correlated with enhanced blood vessel formation at the invasive edge, compared to tumors with silenced MMP-1 expression. Tumors expressing MMP-1 were also associated with osteolysis in vivo, whereas tumors with inhibited MMP-1 levels were not. Additionally, tumor-secreted MMP-1 activated bone-resorbing osteoclasts in vitro. Together, these data suggest a mechanism for MMP-1 in the activation of osteoclasts in vivo. We conclude that breast cancer-derived MMP-1 mediates invasion through soft tissues and bone via mechanisms involving matrix degradation, angiogenesis, and osteoclast activation.

The bone microenvironment in metastasis; what is special about bone?

The skeleton is a common destination for many cancer metastases including breast and prostate cancer. There are many characteristics of bone that make it an ideal environment for cancer cell migration and colonization. Metaphyseal bone, found at the ends of long bone, in ribs, and in vertebrae, is comprised of trabecular bone interspersed with marrow and rich vasculature. The specialized microvasculature is adapted for the easy passage of cells in and out of the bone marrow. Moreover, the metasphyseal regions of bone are constantly undergoing remodeling, a process that releases growth factors from the matrix. Bone turnover also involves the production of numerous cytokines and chemokines that provide a means of communication between osteoblasts and osteoclasts, but co-incidentally can also attract and support metastatic cells. Once in the marrow, cancer cells can interact directly and indirectly with osteoblasts and osteclasts, as well as hematopoietic and stromal cells. Cancer cells secrete factors that affect the network of cells in the bone microenvironment as well as interact with other cytokines. Additionally, transient cells of the immune system may join the local mileau to ultimately support cancer cell growth. However, most metastasized cells that enter the bone marrow are transient; a few may remain in a dormant state for many years. Advances in understanding the bone cell-tumor cell interactions are key to controlling, if not preventing metastasis to bone.

Metastatic tumours to the oral cavity - pathogenesis and analysis of 673 cases

The oral region is an uncommon site for metastatic tumour cell colonization and is usually evidence of a wide spread disease. In 25% of cases, oral metastases were found to be the first sign of the metastatic spread and in 23% it was the first indication of an undiscovered malignancy at a distant site. The jawbones, particularly the mandible, were more frequently affected than the oral soft tissues (2:1). In the oral soft tissues, the attached gingiva was the most commonly affected site (54%). The major primary sites presenting oral metastases were the lung, kidney, liver, and prostate for men, breast, female genital organs (FGO), kidney, and colo-rectum for women. The primary site differs according to oral site colonization, in men the lung was the most common primary site affecting both the jawbones and oral mucosa (22% and 31.3%, respectively) followed by the prostate gland in the jawbones (11%) and kidney in the oral soft tissues (14%). In women, the breast was the most common primary tumour affecting the jawbones and soft tissues (41% and 24.3%, respectively), followed by the adrenal and female genital organs (FGO) in the jawbones (7.7%) and FGO in the soft tissues (14.8%). The clinical presentation of the metastatic lesions differ between the various sites in the oral region. In the jawbones most patients complain of swelling, pain and paresthesia which developed in a relative short period. Early manifestation of the gingival metastases resembled a hyperplastic or reactive lesion, such as pyogenic granuloma, peripheral giant cell granuloma, or fibrous epulis. Because of its rarity, the diagnosis of a metastatic lesion in the oral region is challenging, both to the clinician and to the pathologist, in recognizing that a lesion is metastatic and in determining the site of origin. The clinical presentation of a metastatic lesion in the oral cavity can be deceiving leading to a misdiagnosis of a benign process, therefore, in any case where the clinical presentation is unusual especially in patients with a known malignant disease a biopsy is mandatory.

Biochemical markers in preclinical models of osteoporosis

Although several treatments for osteoporosis exist, further understanding of the mode of action of current treatments, as well as development of novel treatments, are of interest. Thus, preclinical models of osteoporosis are very useful, as they provide the possibility for gaining knowledge about the cellular mechanisms underlying the disease and for studying pharmaceutical prevention or intervention of the disease in simple and strictly controlled systems. In this review, we present a comprehensive collection of studies using biochemical markers of bone turnover for investigation of preclinical models of osteoporosis. These range from pure and simple in vitro systems, such as osteoclast cultures, to ex vivo models, such as cultures of embryonic murine tibiae and, finally, to in vivo models, such as ovariectomy and orchidectomy of rats. We discuss the relevance of the markers in the individual models, and compare their responses to those observed using 'golden standard' methods.

The architecture of the adhesive apparatus of cultured osteoclasts: from podosome formation to sealing zone assembly

BACKGROUND

Osteoclasts are bone-degrading cells, which play a central role in physiological bone remodeling. Unbalanced osteoclast activity is largely responsible for pathological conditions such as osteoporosis. Osteoclasts develop specialized adhesion structures, the so-called podosomes, which subsequently undergo dramatic reorganization into sealing zones. These ring-like adhesion structures, which delimit the resorption site, effectively seal the cell to the substrate forming a diffusion barrier. The structural integrity of the sealing zone is essential for the cell ability to degrade bone, yet its structural organization is poorly understood.

PRINCIPAL FINDINGS

Combining high-resolution scanning electron microscopy with fluorescence microscopy performed on the same sample, we mapped the molecular architecture of the osteoclast resorptive apparatus from individual podosomes to the sealing zone, at an unprecedented resolution. Podosomes are composed of an actin-bundle core, flanked by a ring containing adhesion proteins connected to the core via dome-like radial actin fibers. The sealing zone, hallmark of bone-resorbing osteoclasts, consists of a dense array of podosomes communicating through a network of actin filaments, parallel to the substrate and anchored to the adhesive plaque domain via radial actin fibers.

SIGNIFICANCE

The sealing zone of osteoclasts cultured on bone is made of structural units clearly related to individual podosomes. It differs from individual or clustered podosomes in the higher density and degree of inter-connectivity of its building blocks, thus forming a unique continuous functional structure connecting the cell to its extracellular milieu. Through this continuous structure, signals reporting on the substrate condition may be transmitted to the whole cell, modulating the cell response under physiological and pathological conditions.

Bosentan® inhibits tumor vascularization and bone metastasis in an immunocompetent skin-fold chamber model of breast carcinoma cell metastasis

Angiogenic factors including endothelin-1 (ET-1) play a key role in the progression of breast metastases to bone. We investigated the impact of ET-1 on the development of bone metastases in an immunocompetent murine skin-fold chamber model. Murine mammary carcinoma 4T1 was injected in a skin-fold chamber implanted on CB6 mice along with bone explants. Furthermore, mice were treated with or without a dual selective antagonist of both ET-1 receptors. The progression of the vascularization within the chamber was monitored over time by intravital microscopy (IVM). The tumor growth and the development of bone metastases were assessed by cytokeratin-19 gene expression and histological studies. Results indicate that this new model associated with IVM allows for the continuous monitoring of the change in vascularization associated with the development of bone metastases. Additionally, treatment with an antagonist of both ET-1 receptors was associated with the presence of significantly less vessels near the tumor mass compared to control mice. These changes were correlated with smaller tumor masses and reduced bone invasion (P < 0.05). Thus, in an immunocompetent murine model of breast carcinoma metastases to bone, our data support the hypothesis that vascularization plays a role in tumor development and progression and that ET-1 specifically modulates the angiogenesis associated with breast metastases to the bone.

The molecular dynamics of osteoclast adhesions

Podosomes are specialized adhesive structures that play a central role in bone resorption. In this article we address the molecular diversity and dynamics of podosomes at different states of organization, ranging from scattered distribution over the entire ventral membrane of non-polarized cells, via formation of podosome clusters and developing rings to the assembly of a peripheral belt, resembling the sealing zone of polarized, bone-resorbing osteoclasts. Based on published data and on our own results, we describe here the spatial relationships between key podosome-associated proteins. Using quantitative microscopy, we show here a dramatic increase in the local levels of F-actin, vinculin, paxillin, and alpha-actinin, which occurs upon the transformation of clustered podosomes into rings and sealing zone-like structures. This change is accompanied by a marked decrease in phosphotyrosine levels in the same region. Therefore, our data suggest that a major change in the molecular composition of podosomes is taking place during osteoclast polarization, a change that may be related to adhesion "reinforcement", associated with the assembly of the bone-resorbing apparatus. Studying the nature of the proteins that undergo de-phosphorylation is critical for the understanding of the mechanisms regulating the processes described above.

Effects of third-generation aromatase inhibitors on bone

Low oestradiol levels in women are associated with decreased bone mineral density (BMD) and increased fracture risk. The third-generation aromatase inhibitors (AIs; anastrozole, letrozole, and exemestane) are used in the treatment of early and advanced breast cancer and act by substantially reducing oestrogen synthesis in postmenopausal women. However, due to their mechanism of action, there is concern regarding the long-term effects of these agents on bone, particularly when used in the adjuvant setting. In this paper, the currently available data on the effects of the third-generation AIs on markers of bone turnover, BMD, and fracture risk are reviewed, with the emphasis on results in the adjuvant treatment of early breast cancer. These data suggest that both the steroidal (exemestane) and non-steroidal (anastrozole and letrozole) AIs appear to affect bone turnover. Conclusions regarding any clinically relevant differences between these agents are difficult to make, and further data are awaited from long-term adjuvant use of these three agents in ongoing clinical studies. Postmenopausal women are at increased risk of osteoporosis and fracture, and the increasing use of AIs in the adjuvant treatment of postmenopausal breast cancer patients will require appropriate consideration of fracture risk, with the use of anti-osteoporotic therapies, if necessary.

Serum tartrate-resistant acid phosphatase 5b (TRACP 5b) as a marker of skeletal changes in prostate cancer

Skeletal metastases are a significant problem in prostate cancer (PC). The patients are also exposed to treatment-related skeletal changes. This cross-sectional study evaluated a marker of bone resorption, TRACP 5b in relation to the standard analyte total alkaline phosphatase (tALP) as a marker of skeletal changes. Serum levels of TRACP 5b, tALP and PSA were measured in 130 prostate cancer patients. Comparison was made between patients with (BM+, n = 25) and without (BM-, n = 105) skeletal metastases, and between those treated with (n = 64) or without (n = 66) androgen deprivation (AD). Sensitivities and specificities were calculated for each marker and diagnostic accuracy was evaluated by ROC curve analysis. ROC curves indicated the superior accuracy of tALP, whereas TRACP 5b and PSA were comparable. With tALP the best combination of sensitivity (96%) and specificity of (91%) was reached at a cut-off point 224 U/L, the corresponding values were for TRACP 5b sensitivity (76%), specificity (89%) with a cut-off point 4.89 U/L, and for PSA sensitivity (65%), specificity (81%) at 23 ng/L for skeletal metastases. Patients treated with AD showed with increasing duration an increase in TRACP 5b values. TRACP 5b was less specific than tALP as a marker of skeletal metastases. TRACP 5b may have a role in the diagnostics of skeletal changes in PC with a focus on treatment-related skeletal changes.

Can bone markers guide more effective treatment of bone metastases from breast cancer?

Bone metastases are a common problem for breast cancer patients, causing significant disease-related morbidity and mortality. Bisphosphonates and other cancer therapies can assist in managing these patients. However, assessing treatment efficacy in bone metastases is hampered by the inability to accurately measure disease response within a clinically desirable time frame. Bone-specific biochemical markers, notably type I collagen telopeptide cross-link by-products such as N-telopeptide (NTx) and C-telopeptide (CTx), have been shown to be effective tools for assessing the severity and extent of bone metastases, and the response to bisphosphonates. Elevated NTx levels correlate with adverse clinical outcomes. Normalization of NTx and CTx excretion rates are associated with relief of symptoms and a reduced incidence of skeletal-related events (SRE). This review discusses the expanding role of these bone markers in guiding treatment of bone metastases from breast cancer.

Mechanisms of bone invasion and metastasis in human neuroblastoma

Bone is the second most common site of metastasis in neuroblastoma. Over the last several years, our understanding of the mechanism of bone metastasis in neuroblastoma has significantly improved. Like breast cancer and myeloma, neuroblastoma cells activate osteoclasts to form osteolytic lesions. Activation occurs via the receptor activator of NFkappaB ligand (RANKL) or in the absence of RANKL via activation of bone marrow mesenchymal stem cells and stimulation by these cells of the expression of IL-6, a potent osteoclast activating factor. Several targets for therapeutic intervention can now be identified. Inhibition of osteoclast activation by bisphosphonates has already shown to be effective in preclinical models of neuroblastoma bone metastasis and should now be tested in phase I clinical studies. Inhibition of RANKL and IL-6 are other potential targets that require preclinical studies before being tested in patients. This article provides a review of our current understanding of the mechanisms involved in bone metastasis in neuroblastoma and discusses how this knowledge is leading to the identification of new targets for therapeutic intervention.

Analysis of isolated cranial nerve manifestations in patients with cancer

The aim of this study was to assess the underlying causes of isolated cranial nerve (CN) manifestations in cancer patients. In a prospective study over a 16 month period, 20 of 242 patients presented with isolated CN manifestations, and were assessed for the following: primary site; CN symptoms and signs; length of time between primary diagnosis and neurological involvement; and survival following the neurological diagnosis. The most frequent primary site was determined as hematological malignancy (9/20). Thirteen of the 20 patients presented with single CN manifestations. Underlying causes of CN manifestations in 16 of the 20 patients were related to metastases. They included meningeal carcinomatosis (10/16), brain stem metastases (3/16), primary brain astrocytomas (1/16), and metastases out of the central nervous system (2/16). The remaining four patients' CN manifestations related to non-metastatic conditions. Although most of the isolated CN manifestations were due to systemic metastasis, in particular to the meninges, up to 20% were related to benign conditions.

C-reactive protein is significantly associated with prostate-specific antigen and metastatic disease in prostate cancer

OBJECTIVE

To further analyse the relationship of c-reactive protein (CRP) levels to prostate cancer, by measuring CRP in men with prostate cancer and benign prostatic hypertrophy (BPH), as chronic inflammation has long been linked to cancers with an infectious cause and CRP is a nonspecific marker for inflammation, associated with prostate cancer incidence and progression.

PATIENTS AND METHODS

Data from 114 men, most of whom had had radioactive seeds implanted, were evaluated from November 1990 to April 2002. In addition, 27 men were included who had biopsy-confirmed BPH. CRP was assessed with an automated chemiluminometric high-sensitivity assay kit.

RESULTS

There was no significant difference in CRP levels in men with localized prostate cancer or BPH but levels were significantly higher in men with bone metastases. There was also a significant correlation of CRP level with prostate-specific antigen (PSA) in those with cancer. Because PSA is correlated with disease stage, multiple linear regression was used with CRP as the dependent variable, and PSA and disease stage as independent variables. The regression was significant overall (P < 0.001) and the effect of disease stage on CRP (P < 0.001) was independent of the effect of PSA level (P = 0.001).

CONCLUSION

The strong association of CRP with PSA, independent of tumour stage, suggests that inflammation might be fundamental in prostate cancer, and that chronic inflammation may be a legitimate target for prostate cancer chemoprevention and treatment.

Bone Marrow Mesenchymal Stem Cells Provide an Alternate Pathway of Osteoclast Activation and Bone Destruction by Cancer Cells

The bone is the third most common site of cancer metastasis. To invade the bone, tumor cells produce osteoclast-activating factors that increase bone resorption by osteoclasts. Here we report that human neuroblastoma cells that form osteolytic lesions in vivo do not produce osteoclast-activating factors but rather stimulate osteoclast activity in the presence of human bone marrow mesenchymal stem cells. This alternative pathway of osteoclast activation involves a nonadhesive interaction between neuroblastoma cells and bone marrow mesenchymal stem cells. Stimulated bone marrow mesenchymal stem cells express markedly increased levels of interleukin-6, which is then responsible for osteoclast activation. This report describes a critical role of bone marrow mesenchymal stem cells in bone destruction in cancer.

Assessment of therapeutic response in patients with metastatic bone disease

Metastatic bone disease is common in cancer patients and causes substantial disease-related morbidity and mortality. However, several effective treatments are available for the management of these patients. Bisphosphonates, which inhibit osteoclast-mediated resorption of bone matrix, are especially important because they decrease the incidence of skeletal-related events in many tumour types and can complement antineoplastic therapies. At present, assessment of treatment for bone metastases is hindered by a lack of effective, rapid methods to measure disease response. We discuss the difficulties of current measures of response assessment and describe the development of new radiological and biochemical markers of bone metastases. Assays that detect type I collagen telopeptides as markers of bone resorption seem to be most promising at present.

Osteopontin-deficiency suppresses growth of B16 melanoma cells implanted in bone and osteoclastogenesis in co-cultures

Tumor metastasis and invasion to bone is one of major medical issues in our modern societies. Osteopontin deficiency decreased tumor invasion in bone based on knockout mouse study. In bone, osteopontin is a positive factor to increase tumor invasion.

INTRODUCTION

Osteopontin is an arginine-glycine-aspartate (RGD)-containing protein and is recognized by integrin family members. Osteopontin promotes cell attachment to bone, where it is abundantly present. Because osteopontin levels were reported to be elevated in patients bearing highly metastatic tumors, this molecule has been implicated in the metastasis of tumors. However, the effect of osteopontin on the invasion of tumor cells in bone microenvironment has not been clear. The purpose of this paper is to elucidate the effect of host osteopontin on the behavior of tumor cells in bone.

MATERIALS AND METHODS

Bone marrow ablation was conducted in the femora of mice, and B16 melanoma cells were injected directly into the ablated bone marrow space of the osteopontin-deficient and wildtype mice.

RESULT

Invasion foci of B16 melanoma cells in the cortical bone was observed 7 weeks after tumor cell implantation. The number of the foci was 5-fold less in osteopontin-deficient mice compared with that in wildtype mice. In wildtype mice, trabecular bone formation was not observed in the ablated marrow space where tumor cells were injected. In contrast, significant levels of trabecular bone were observed in the marrow space of osteopontin-deficient mice even after tumor cells were injected. To examine cellular mechanisms underlying these observations, co-cultures of bone marrow cells and B16 cells were conducted. While the presence of B16 cells promoted TRACP+ cell development in wildtype bone marrow cells, such enhancement in TRACP+ cell formation by the co-cultures with B16 cells was reduced in the case of bone marrow cells from osteopontin-deficient mice.

CONCLUSIONS

Osteopontin deficiency reduced the bone loss caused by tumor cell implantation into the bone marrow space.