Pathophysiologic interactions in skeletal metastasis

Ablation Techniques in Cancer Pain

Painful bone metastases are a frequently encountered problem in oncology practice. The skeletal system is the third most common site of metastatic disease and up to 85% of patients with breast, prostate, and lung cancer may develop bone metastases during the course of their disease.

Human-derived osteoblast-like cells and pericyte-like cells induce distinct metastatic phenotypes in primary breast cancer cells

Approximately 70% of advanced breast cancer patients will develop bone metastases, which accounts for ∼90% of cancer-related mortality. Breast cancer circulating tumor cells (CTCs) establish metastatic tumors in the bone after a close interaction with local bone marrow cells including pericytes and osteoblasts, both related to resident mesenchymal stem/stromal cells (BM-MSCs) progenitors. In vitro recapitulation of the critical cellular players of the bone microenvironment and infiltrating CTCs could provide new insights into their cross-talk during the metastatic cascade, helping in the development of novel therapeutic strategies. Human BM-MSCs were isolated and fractionated according to CD146 presence. CD146+ cells were utilized as pericyte-like cells (PLCs) given the high expression of the marker in perivascular cells, while CD146- cells were induced into an osteogenic phenotype generating osteoblast-like cells (OLCs). Transwell migration assays were performed to establish whether primary breast cancer cells (3384T) were attracted to OLC. Furthermore, proliferation of 3384T breast cancer cells was assessed in the presence of PLC- and OLC-derived conditioned media. Additionally, conditioned media cultures as well as transwell co-cultures of each OLCs and PLCs were performed with 3384T breast cancer cells for gene expression interrogation assessing their induced transcriptional changes with an emphasis on metastatic potential. PLC as well as their conditioned media increased motility and invasion potential of 3384T breast cancer cells, while OLC induced a dormant phenotype, downregulating invasiveness markers related with migration and proliferation. Altogether, these results indicate that PLC distinctively drive 3384T cancer cells to an invasive and migratory phenotype, while OLC induce a quiescence state, thus recapitulating the different phases of the in vivo bone metastatic process. These data show that phenotypic responses from metastasizing cancer cells are influenced by neighboring cells at the bone metastatic niche during the establishment of secondary metastatic tumors.

Bone metastases in thyroid cancer

•

Osseous metastases (OMs) occur in only 4% of all thyroid cancer patients but are associated with greatly increased morbidity and mortality.

•

OMs are about twice as frequent in follicular, hurthle cell, and medullary thyroid cancers as compared to papillary thyroid cancers.

•

OMs are often lytic, triggered via activation of osteoclasts by tumor cells in a “vicious cycle”.

•

OMs are often initially asymptomatic, but associated with eventual skeletal related events in >75%.

•

Early identification of OMs, preemptive treatment with antiresorptive agents, and aggressive treatment of focal lesions before crisis are key.

Whereas preemptive screening for the presence of lymph node and lung metastases is standard-of-care in thyroid cancer patients, bone metastases are less well studied and are often neglected in thyroid cancer patient surveillance. Bone metastases in thyroid cancer are, however, independently associated with poor/worse prognosis with a median overall survival from detection of only 4 years despite an otherwise excellent prognosis for the vast majority of thyroid cancer patients. In this review we summarize the state of current knowledge as pertinent to bony metastatic disease in thyroid cancer, including clinical implications, impacts on patient function and quality of life, pathogenesis, and therapeutic opportunities, proposing approaches to patient care accordingly. In particular, bone metastasis pathogenesis appears to reflect cooperatively between cancer and the bone microenvironment creating a “vicious cycle” of bone destruction rather than due exclusively to tumor invasion into bone. Additionally, bone metastases are more frequent in follicular and medullary thyroid cancers, requiring closer bone surveillance in patients with these histologies. Emerging data also suggest that treatments such as multikinase inhibitors (MKIs) can be less effective in controlling bone, as opposed to other (e.g. lung), metastases in thyroid cancers, making special attention to bone critical even in the setting of active MKI therapy. Although locoregional therapies including surgery, radiotherapy and ablation play important roles in palliation, antiresorptive agents including bisphosphonates and denosumab appear individually to delay and/or lessen skeletal morbidity and complications, with dosing frequency of every 3 months appearing optimal; their early application should therefore be strongly considered.

xCT knockdown in human breast cancer cells delays onset of cancer-induced bone pain

Cancers in the bone produce a number of severe symptoms including pain that compromises patient functional status, quality of life, and survival. The source of this pain is multifaceted and includes factors secreted from tumor cells. Malignant cells release the neurotransmitter and cell-signaling molecule glutamate via the oxidative stress-related cystine/glutamate antiporter, system x_C^-, which reciprocally imports cystine for synthesis of glutathione and the cystine/cysteine redox cycle. Pharmacological inhibition of system x_C^- has shown success in reducing and delaying the onset of cancer pain-related behavior in mouse models. This investigation describes the development of a stable siRNA-induced knockdown of the functional trans-membrane system x_C^- subunit xCT ( SLC7A11) in the human breast cancer cell line MDA-MB-231. Clones were verified for xCT knockdown at the transcript, protein, and functional levels. RNAseq was performed on a representative clone to comprehensively examine the transcriptional cellular signature in response to xCT knockdown, identifying multiple differentially regulated factors relevant to cancer pain including nerve growth factor, interleukin-1, and colony-stimulating factor-1. Mice were inoculated intrafemorally and recordings of pain-related behaviors including weight bearing, mechanical withdrawal, and limb use were performed. Animals implanted with xCT knockdown cancer cells displayed a delay until the onset of nociceptive behaviors relative to control cells. These results add to the body of evidence suggesting that a reduction in glutamate release from cancers in bone by inhibition of the system x_C^- transporter may decrease the severe and intractable pain associated with bone metastases.

Generation of a co-culture cell micropattern model to simulate lung cancer bone metastasis for anti-cancer drug evaluation

A549/OB co-culture micropattern was fabricated through μ-eraser strategy to mimic lung cancer bone metastasis for DOX efficacy evaluation.

Preparation of tetrazine-containing [2 + 1] complexes of 99mTc and in vivo targeting using bioorthogonal inverse electron demand Diels–Alder chemistry

A new ^99mTc-labelled tetrazine for targeted imaging using bioorthogonal chemistry was developed and evaluated in vivo using a trans-cyclooctene derived bisphosphonate targeting regions of high bone turnover and bone lesions.

Halloysite Nanotube Coatings Suppress Leukocyte Spreading

The nanoscale topography of adhesive surfaces is known to be an important factor governing cellular behavior. Previous work has shown that surface coatings composed of halloysite nanotubes enhance the adhesion, and therefore capture of, rare target cells such as circulating tumor cells. Here we demonstrate a unique feature of these coatings in their ability to reduce the adhesion of leukocytes and prevent leukocyte spreading. Surfaces were prepared with coatings of halloysite nanotubes and functionalized for leukocyte adhesion with E-selectin, and the dilution of nanotube concentration revealed a threshold concentration below which cell spreading became comparable to smooth surfaces. Evaluation of surface roughness characteristics determined that the average distance between discrete surface features correlated with adhesion metrics, with a separation distance of ∼2 μm identified as the critical threshold. Computational modeling of the interaction of leukocytes with halloysite nanotube-coated surfaces of varying concentrations demonstrates that the geometry of the cell surface and adhesive counter-surface produces a significantly diminished effective contact area compared to a leukocyte interacting with a smooth surface.

Bisphosphonates and bone metastases: current status and future directions

Since bone metastases in advanced cancer are common and frequently lead to skeletal-related morbid complications, their treatment remains a major challenge in cancer therapy. Bisphosphonates not only significantly decreased the odds ratios for fracture, need for radiotherapy, and incidence of hypercalcemia, but also had proven ability in the preservation of the 3D microstructure of bone that is responsible for bone stability. Bisphosphonates are well tolerated and have a very low incidence of serious side effects. Consequently, bisphosphonates have become the standard of care for the treatment of malignant bone disease. Benefits of bisphosphonate treatment appears to be more pronounced with longer treatment, indicating that they should be continued until no longer clinically relevant. As this advice has substantial implications on resources, it is essential that the use of bisphosphonates is evidence based.

Inhibition of breast cancer-cell glutamate release with sulfasalazine limits cancer-induced bone pain

Cancer in bone is frequently a result of metastases from distant sites, particularly from the breast, lung, and prostate. Pain is a common and often severe pathological feature of cancers in bone, and is a significant impediment to the maintenance of quality of life of patients living with bone metastases. Cancer cell lines have been demonstrated to release significant amounts of the neurotransmitter and cell-signalling molecule l-glutamate via the system xC(-) cystine/glutamate antiporter. We have developed a novel mouse model of breast cancer bone metastases to investigate the impact of inhibiting cancer cell glutamate transporters on nociceptive behaviour. Immunodeficient mice were inoculated intrafemorally with the human breast adenocarcinoma cell line MDA-MB-231, then treated 14days later via mini-osmotic pumps inserted intraperitoneally with sulfasalazine, (S)-4-carboxyphenylglycine, or vehicle. Both sulfasalazine and (S)-4-carboxyphenylglycine attenuated in vitro cancer cell glutamate release in a dose-dependent manner via the system xC(-) transporter. Animals treated with sulfasalazine displayed reduced nociceptive behaviours and an extended time until the onset of behavioural evidence of pain. Animals treated with a lower dose of (S)-4-carboxyphenylglycine did not display this reduction in nociceptive behaviour. These results suggest that a reduction in glutamate secretion from cancers in bone with the system xC(-) inhibitor sulfasalazine may provide some benefit for treating the often severe and intractable pain associated with bone metastases.

Oxidative stress and cancer pain

Breast cancers are the most common source of metastases to bone, of which cancer-induced bone pain is a frequent pathological feature. Cancer-induced bone pain is a unique pain state with multiple determinants that remains to be well understood and managed. Current standard treatments are limited by dose-dependent side effects that can reduce the quality of life of patients. Glutamate is a neurotransmitter and bone cell-signalling molecule that is released via the system x(c)(-) cystine/glutamate antiporter from cancer cell types that frequently metastasize to bone, including breast cancers. In cancer cells, glutamate release is understood to be a side effect of the cellular response to oxidative stress that upregulates the expression and activity of system x(c)(-) to promote the increased import of cystine. Attenuation of glutamate release from cancer cells has been demonstrated to result in reductions in associated cancer-induced bone pain in animal models. This review examines the clinical implications of attenuating cystine uptake and glutamate release in the treatment of cancer-induced bone pain.

Zinc finger E-box binding homeobox 1 promotes invasion and bone metastasis of small cell lung cancer in vitro and in vivo

Bone is one of the most frequent targets of small cell lung cancer (SCLC) metastasis and is closely associated with a poor prognosis, but the specific cellular gene alterations responsible for SCLC with bone metastasis are unclear. Zinc finger E-box binding homeobox 1 (ZEB1) as an E-box transcriptional repressor has been suggested that an important inducer of the epithelial-mesenchymal transition (EMT) and a promoter of tumor metastasis in colon, breast and lung cancers. However, the relationship between ZEB1 and SCLC with bone metastasis is unclear. In this study, ZEB1 was found to be highly expressed in bone-metastatic SCLC tissues and cell lines as compared with those that were non-metastatic (P < 0.05). Using a lentivirus RNA interference technique to knockdown ZEB1 expression in bone-metastatic SCLC cells (SBC-5 cell line), we found that ZEB1 siRNA could inhibit the invasive and migratory ability and decrease parathyroid hormone-related protein expression, as determined by invasion assays and enzyme-linked immunosorbent assays. Besides, ZEB1 siRNA significantly inhibited the bone metastasis of SBC-5 cells in vivo. Furthermore, overexpression of ZEB1 in SBC-3 cells, which demonstrate promoted bone-metastatic potential, dramatically promoted their invasive and migratory ability and parathyroid hormone-related protein expression as well as increased the number and sites of bone metastases in vivo compare to the control group. We also found that SBC-3 cells underwent EMT, as indicated by decreased epithelial markers and increased mesenchymal marker expression. Taken together, these results indicate that ZEB1 promoted the invasive ability and bone metastasis of SCLC cells, and that this was partially mediated via the EMT pathway.

Physiopathology of spine metastasis

The metastasis is the spread of cancer from one part of the body to another. Two-thirds of patients with cancer will develop bone metastasis. Breast, prostate and lung cancer are responsible for more than 80% of cases of metastatic bone disease. The spine is the most common site of bone metastasis. A spinal metastasis may cause pain, instability and neurological injuries. The diffusion through Batson venous system is the principal process of spinal metastasis, but the dissemination is possible also through arterial and lymphatic system or by contiguity. Once cancer cells have invaded the bone, they produce growth factors that stimulate osteoblastic or osteolytic activity resulting in bone remodeling with release of other growth factors that lead to a vicious cycle of bone destruction and growth of local tumour.

Extracellular glutamate alters mature osteoclast and osteoblast functions

Glutamatergic intercellular communication is involved in many aspects of metabolic homeostasis in normal bone. In bone metastasis, the balance between bone formation and degradation is disrupted. Although the responsible mechanisms are not clear, we have previously identified that cancer cell lines used in bone tumour models secrete glutamate, suggesting that tumour-derived glutamate may disrupt sensitive signalling systems in bone. This study examines the role of glutamate in mature osteoclastic bone resorption, osteoblast differentiation, and bone nodule formation. Glutamate was found to have no effect on the survival or activity of mature osteoclasts, although glutamate transporter inhibition and receptor blockade increased the number of bone resorption pits. Furthermore, transporter inhibition increased the area of resorbed bone while significantly decreasing the number of osteoclasts. Alkaline phosphatase activity and extracellular matrix mineralization were used as measurements of osteoblast differentiation. Glutamate significantly increased osteoblast differentiation and mineralization, but transport inhibitors had no effect. These studies support earlier findings suggesting that glutamate may be more important for osteoclastogenesis than for osteoclast proliferation or functions. Since glutamate is capable of changing the differentiation and activities of both osteoclast and osteoblast cell types in bone, it is reasonable to postulate that tumour-derived glutamate may impact bone homeostasis in bone metastasis.

A by-product of glutathione production in cancer cells may cause disruption in bone metabolic processes

Bone is a frequent site for metastasis of breast and prostate cancers, often resulting in pathologic changes in bone metabolism and severe pain. The mechanisms involved are not well understood, but tumour cells may release factors that interfere with bone homeostasis. Several observations have led us to hypothesize that the functional disruptions in bone metastasis are the result of a biological process common to many cell types. The high metabolic activity characteristic of cancer cells often upregulates oxidative stress protection mechanisms such as the antioxidant molecule glutathione. In maintaining redox balance, this normal metabolic response may result in unintended pathologic effects in certain sensitive organ sites. Malignant glioma cells kill surrounding neurons in the brain specifically by secreting the amino acid glutamate, an obligatory waste product of glutathione synthesis. We suggest that glutamate release is a plausible mechanism that may account for the pathologic changes in bone metastasis, since bone, like brain, is also highly sensitive to glutamatergic disruption. This report reviews the available evidence to draw a mechanistic connection between tumour cell oxidative stress and the pathology seen in patients with bone metastasis.

Targeting the {alpha} receptor for platelet-derived growth factor as a primary or combination therapy in a preclinical model of prostate cancer skeletal metastasis

PURPOSE

Platelet-derived growth factor α (PDGFRα) is highly expressed in primary prostate cancer and associated skeletal metastases. Here, we tested whether targeting this receptor could impair metastatic colonization and progression, as well as prolong survival, either as primary or as combination therapy.

EXPERIMENTAL DESIGN

We used a preclinical animal model of metastasis in which PC3-ML human prostate cancer cells are inoculated directly in the blood circulation. First, the humanized, monoclonal antibody IMC-3G3 was administered to mice bearing established skeletal metastases. Second, we targeted the stromal PDGFRα with IMC-1E10, an antibody specific for the murine receptor. Third, IMC-3G3 and the bisphosphonate zoledronic acid (ZA), administered separately or in combination, were tested on the progression of skeletal lesions and overall survival. In addition, the ability of IMC-3G3 and ZA to impair initial colonization of the bone marrow by prostate cancer cells was investigated.

RESULTS

The blockade of PDGFRα on prostate cancer cells by IMC-3G3 reduces the size of established skeletal metastases, whereas the IMC-1E10 antibody directed against the stromal PDGFRα fails to inhibit metastatic progression. IMC-3G3 and ZA, either separately or in combination, significantly slow tumor growth and seem to prolong survival. Lastly, the blockade of PDGFRα by IMC-3G3 inhibits the initial phase of bone colonization, whereas ZA is ineffective at this stage.

CONCLUSION

This study presents compelling evidence that targeting PDGFRα with IMC-3G3 delays the progression of early metastatic foci and reduces the size of more established lesions. In addition, IMC-3G3, either alone or in combination with ZA, prolongs survival in animal models.

Cancer cell lines release glutamate into the extracellular environment

Bone is one of the most frequent sites for metastasis of breast and prostate cancers. Bone metastases are associated with pathologic changes in bone turnover and severe pain. The mechanisms that trigger these effects are not well understood, but it is postulated that tumour cells release factors which interfere with signalling processes critical to bone homeostasis. We have identified that several cancer cell lines known to cause bone disruption in animal models of bone metastasis appear to secrete glutamate into their extracellular environment in vitro. Although these cells also express specific glutamate receptors, the implications of this potentially disruptive chemical signal are discussed in relation to normal glutamate-dependent communication processes in bone and a possible mechanistic connection is made between tumour cell glutamate release and the development of pathological changes in bone turnover.

Thyroid and bone

This article provides a summary of the numerous interactions between the thyroid gland and the skeleton, in the normal state, in disorders of thyroid function and as a result of thyroid malignancy. It recaps the current understanding of bone growth and development in the endochondral growth plate and the normal mechanisms of mature bone remodeling. The actions of thyroid hormones on these processes are described, and the clinical impact of thyroid disorders and their treatments on the bone are summarized. Finally, our current understanding of the physiology of bone metastases from thyroid cancer is covered.

Advances in the Treatment of Bone Metastases

The skeleton is the third most common site for cancer to spread to after the liver and lungs. Malignancies that can cause destruction of skeletal bones include multiple myeloma and metastatic disease of the breast, prostate, and lung. Bone metastases are problematic for patients with cancer because accelerated bone breakdown occurs with many associated complications. One or more of the following problems may occur: pain, hypercalcemia, pathologic fractures, myelosuppression, and spinal cord compression with subsequent progressive immobility. Quality of life is affected negatively, and associated feelings of fear, grief, anger, despair, anxiety, and depression can occur. Management of malignancies of the bone involves a multimodal approach. Therapies include analgesia, hormone therapy, chemotherapy, surgery, radiation therapy, and the use of bisphosphonates. Nurses can be instrumental in promoting positive outcomes for patients with bone metastases.

Bone mineral density, bone turnover, and osteoprotegerin in depressed women with and without borderline personality disorder

OBJECTIVE

Low bone mineral density has repeatedly been reported in patients with major depressive disorder (MDD), and MDD has been discussed as a risk factor for the development of osteoporosis. MDD in young adults often occurs in the context of borderline personality disorder (BPD), and both MDD and BPD have been associated with a dysregulation of the hypothalamic-pituitary-adrenal system and subsequent hypercortisolemia. To date, it is unclear whether comorbid BPD in depressed patients modulates the extent of bone mass reduction. Therefore, we examined bone density, markers of bone turnover, and proinflammatory cytokines in depressed patients with and without BPD. Patients with BPD alone and healthy women served as comparison groups.

METHOD

Twenty-four patients with MDD and 23 patients with comorbid MDD and BPD were included. Sixteen patients with BPD and 20 healthy women of similar body mass index served as the comparison group. BMD was assessed by means of dual-energy x-ray absorptiometry. Markers of bone turnover, endocrine and immune parameters were determined. For data analysis, the group of depressed patients without comorbid BPD was divided according to age into two groups (younger depressed patients with a mean age of 30 years and older patients with a mean age of 42.9 years).

RESULTS

BMD at the lumbar spine was significantly reduced in a) depressed women with comorbid BPD (mean age, 28.6 years) and in b) older depressed patients without BPD (mean age, 42.9 years). Osteocalcin, a marker of osteoblastic activity, and crosslaps, a marker of bone loss, were significantly different between the study groups. Tumor necrosis factor-alpha was increased in depressed patients when compared with healthy women. Furthermore, TNF-alpha was positively correlated with serum crosslaps, a marker for osteoclastic activity.

CONCLUSION

Depression is associated with reduced bone mass, in particular in patients with comorbid BPD. Possible factors contributing to BMD reduction include endocrine and immune alterations associated with either MDD or BPD. We conclude from our data that a history of MDD with and without comorbid BPD should be considered as a risk factor in clinical assessment instruments for the identification of persons prone to osteoporosis.

[18F]fluorodeoxyglucose positron emission tomography is more sensitive than skeletal scintigraphy for detecting bone metastasis in endemic nasopharyngeal carcinoma at initial staging

PURPOSE

Bone metastasis occurs frequently in patients with endemic nasopharyngeal carcinoma (NPC). The main objective of this study is to evaluate positron emission tomography (PET) using fluorine-18-labeled fluorodeoxyglucose ([18F]FDG) and conventional skeletal scintigraphy (SS) for detecting bone metastasis at initial staging. Auxiliary objectives are to identify risk factors for bone metastasis and features associated with poor survival in patients with bone metastasis.

PATIENTS AND METHODS

Patients with endemic NPC before initiation of treatment were enrolled. PET and SS were performed at initial staging and compared using McNemar's paired-sample test. Bone metastasis was considered to be present if there was any reliable evidence identified within 1 year after primary diagnosis. Multiple logistic regression and Cox's proportional hazards models were used for auxiliary objectives.

RESULTS

Thirty (15%) of 202 eligible patients were found to have bone metastasis. [18F]FDG PET was found to be more sensitive than SS in the patient-based analysis (P = .006) and in the region-based analysis at the spine (P = .001). Advanced N stage was the only significant risk factor (P < .0001), and the coexistence of hepatic metastasis was a prognosticator of poor survival (P = .017). The survival was not significantly better for patients with bone metastasis undetected at primary staging than for those with initially detectable bone metastasis (P = .620).

CONCLUSION

[18F]FDG PET is more sensitive than SS for detecting bone metastasis in endemic NPC at initial staging, whereas SS can be considered as supplementary in this setting.

New paradigms for therapy for osteosarcoma

Osteosarcoma is a primary bone malignancy generally affecting the young, with 60% of cases occurring before the age of 25 years and the peak incidence at 15 years. Survival has improved over the past several decades, with non- metastatic disease having an approximately 70% chance of long-term survival. Unfortunately, patients with metastatic disease at diagnosis or those who have recurrent disease have a dismal prognosis, with approximately 20% surviving long term. In this review article we describe several new therapies in development for osteosarcoma. These include immune-based therapies, strategies to inhibit tumor growth, radiotherapy, and the introduction of new chemotherapies and targets.

The emerging role of CD44 in regulating skeletal micrometastasis

The hyaluronan (HA) receptor CD44 has a well documented role in tumour metastasis. This review focuses on the potential significance of CD44 expression and function in regulating the metastasis of both haematological malignancies and solid tumours to the bone. Specifically, the review will discuss the evidence that HA-CD44 interactions facilitate the arrest of circulating malignant cells upon the bone marrow endothelial cells and discuss data that suggests CD44 may orchestrate the ability of tumour cells to regulate the modification of the bone matrix and support its colonisation by malignant cells.

Prostate cancer metastases to bone: pathophysiology, pain management, and the promise of targeted therapy

Bone metastases are a significant cause of pain and morbidity in prostate cancer, especially if they lead to complications such as pathological fractures and spinal cord compression. Palliation of pain can be achieved with radiation, radioisotopes, hormone therapy, chemotherapy, and bisphosphonates. Bisphosphonates also reduce the risk of skeletal complications. Studies with animal models and advances in understanding the molecular basis for bone metastases have yielded new targets for therapy. Some of the promising therapeutic trials are reviewed in this paper.

Use of bisphosphonates can dramatically improve pain in advanced hormone-refractory prostate cancer patients

INTRODUCTION

Approximately 85% of patients who die from prostate cancer present the spread of bone metastases. Even though the radiological appearance of such metastases is osteoblastic, it is now known that these lesions coexist in their microenvironment with blastic and lytic lesions. The process always begins with bone lysis by osteoclast proliferation, paralleling nearby bone deposition. The treatment options are palliative and have poor clinical response with short-lived improvement. We have studied the clinical effect of bisphosphonates (clodronate) in the treatment of skeletal complications from prostate cancer.

MATERIALS AND METHODS

In an open prospective study, 58 patients with hormone-refractory prostate cancer with bone metastases were assessed from November 2000 to September 2003. The mean age was 70.3 y (range: 51-87 y). Bone scintigraphy, plain X-ray, assaying of prostate-specific antigen (PSA) and biochemical tests were requested before and following treatment. Patients were previously and subsequently assessed using the visual pain scale (0-10) and Karnofsky's index after the first and second intravenous (i.v.) infusions (administration of i.v. clodronate every 28 days) and every 4-6 months thereafter. Student's t-test was used for statistical analysis.

RESULTS

A total of 53 patients (91.4%) showed improvement after the first and/or second cycle, which persisted for at least 4 months (average 6.3 months). The averages on the visual pain scale improved from 7.4 (range: 2-8) to 2.4 (0-7) and on Karnofsky's index from 43 (32-58) to 73 (50-82). The radiological appearance of the metastases improved in 27 patients (46.5%) and there were few relapses (six patients; 10.3%).

CONCLUSIONS

Clodronate was effective in the treatment of skeletal complications from prostate cancer. There was an objective response in 91.4% of treated patients, with a marked improvement in the subjective visual pain scale evaluation as well as on Karnofsky's index, with low side effects.

Integrin alpha5beta1 promotes survival of growth-arrested breast cancer cells: an in vitro paradigm for breast cancer dormancy in bone marrow

The mechanisms of long-term survival of occult breast cancer cells in the bone marrow microenvironment are not known. Using selected bone marrow stromal components with demonstrated roles in promoting growth arrest and survival of breast cancer cells, we reconstituted an in vitro model for dormancy of breast cancer cells in bone marrow. According to this model, basic fibroblast growth factor, a mammary differentiation factor abundant in the bone marrow stroma, induces growth arrest of relatively well-differentiated breast cancer cells, induces a spread appearance, and restricts their survival to fibronectin by up-regulating integrin alpha5beta1. Most of the basic fibroblast growth factor-arrested cells fail to establish optimal ligation to fibronectin and undergo cell death. Cells that do attach to fibronectin, another major constituent of the bone marrow microenvironment, stay alive and growth-arrested for many weeks. Although capable of adhering to other stromal proteins collagen and laminin, dormant cells do not gain a survival advantage from these interactions. Using function-blocking peptides, we show a specific contribution of alpha5beta1-fibronectin interaction in maintaining survival of growth-arrested cells, potentially by negatively modulating apoptotic response via signaling pathways. Blocking of phosphatidylinositol 3'-kinase and Akt inhibits survival of dormant clones, demonstrating this as one of those pathways. Experiments with human bone marrow stroma cocultures confirm the role of fibronectin ligation in maintaining survival of dormant clones.

Parathyroid hormone-related protein (PTHrP) is responsible for production of bone metastasis, but not visceral metastasis, by human small cell lung cancer SBC-5 cells in natural killer cell-depleted SCID mice

We previously established an osteolytic bone metastasis model with multiorgan dissemination in natural killer (NK) cell-depleted severe combined immunodeficient (SCID) mice using human small cell lung cancer cells (SBC-5), which highly express the parathyroid hormone-related protein (PTHrP). In our present study, we evaluated the role of PTHrP on bone metastasis by SBC-5 cells using anti-PTHrP neutralizing antibody (Ab). Anti-PTHrP Ab did not affect the proliferation or cytokine production of SBC-5 cells in vitro. Repeated intravenous injection with anti-PTHrP Ab inhibited the formation of bone metastasis in a dose-dependent manner, while the same treatment had no significant effect on the metastasis to visceral organs (lung, liver, kidney and lymph node). In addition, treatment with anti-PTHrP Ab improved the elevated serum calcium level, associated with inhibition of osteolytic bone metastasis, suggesting that anti-PTHrP Ab inhibited bone metastasis via suppression of bone resorption probably by neutralizing PTHrP. These findings suggest that PTHrP is essential for bone metastasis, but not visceral metastasis, by small cell lung cancer SBC-5 cells.

Differential expression of osteopontin and bone sialoprotein in bone metastasis of breast and prostate carcinoma

Breast and prostate cancer often metastasise to the skeleton. Interestingly, the histopathological characteristics of the bone lesions that arise from these two cancer types differ. Breast tumours give rise to metastases in the skeleton with a mixed lytic/sclerotic pattern, whereas a predominantly sclerotic pattern is seen in metastases from prostate tumours. Osteopontin (OPN) and bone sialoprotein (BSP) are bone matrix proteins that have been implicated in the selective affinity of cancer cells for bone. In the present study, 21 patient cases with skeletal metastasis and their respective primary tumours (12 with breast cancer, 9 with prostate cancer) were investigated by immunohistochemistry in order to assess the level of OPN and BSP. Moderate to strong OPN expression was found in 42% of all breast tumours and in 56% of all prostate tumours. Significantly more breast cancer bone metastases exhibited high OPN expression, 83%, as compared with prostate tumour bone metastases, 11% (P = 0.0019). In contrast, moderate to strong BSP expression was found in 33% of breast tumours and in 89% of prostate tumours. In the bone lesions, only 33% of breast tumour metastases showed moderate/strong BSP expression compared to 100% of prostate tumour metastases (P = 0.0046). This divergent pattern of OPN/BSP expression could be an important determinant for the different characteristics of these two types of bone metastasis, i.e., lytic vs. sclerotic, consistent with the proposed role of OPN in differentiation and activation of osteoclasts and of BSP as a stimulator of bone mineralisation.

Combination of early bisphosphonate administration and irradiation leads to improved remineralization and restabilization of osteolytic bone metastases in an animal tumor model

BACKGROUND

The goal of the current study was to analyze the combined effect of bisphosphonates (BPs) and irradiation on remineralization and restabilization of osteolytic bone metastases in an animal tumor model.

METHODS

Bone metastases were induced in male Wistar rats via intraosseous injection of the Walker carcinosarcoma 256B cell line into both proximal tibia metaphyses on Day 1 of the study. Three treatment groups were analyzed. All animals received a single radiation dose of 17 grays (in the form of 6-megaelectron-volt electrons) on Day 7 and were sacrificed on Day 49. Group 1 (the control group) was treated with irradiation only. Groups 2 and 3 received additional BPs (clodronate; daily intraperitoneal injection dose, 20 mg/kg per day). In Group 2, BPs were given before irradiation, on Days 3-6; this schedule later was referred to as early BP treatment. In Group 3, BPs were administered simultaneously with irradiation, on Days 7-10; this schedule later was referred to as simultaneous BP treatment. The endpoints of the study were bone density and microstructural parameters of bone on Day 49. Bone density was measured using X-ray absorption. Microstructural parameters of bone were assessed using histomorphometry. A total of thirty tibiae were analyzed in each group.

RESULTS

After irradiation, bone density was significantly higher among animals in the early BP treatment group compared with those in the control group and those in the simultaneous BP treatment group (P = 0.001). Histomorphometric analysis of bone showed significantly better-preserved (P < 0.001) microstructural parameters (bone area, trabecular number, and trabecular separation) in the early BP treatment group compared with the control and simultaneous BP treatment groups.

CONCLUSIONS

Early BP administration in combination with irradiation led to improved remineralization and restabilization of osteolytic bone metastases in an animal tumor model.

Clodronate for treatment of bone metastases in hormone refractory prostate cancer

INTRODUCTION

Approximately 85% of patients who die from prostate cancer have bone metastases. Even though the radiological aspect of such metastases is osteoblastic, we currently know that these lesions are mixed, with coexisting blastic and lytic lesions, always beginning with bone lysis by osteoclast proliferation. Treatment options are palliative and have poor response, and when there is an improvement it is usually short-lived. This work intends to study the effect of clodronate in the treatment of skeletal complications of prostate cancer.

MATERIALS AND METHODS

In an open prospective study 32 patients with hormone refractory prostate cancer with metastases to bones were assessed, in the period between November 2000 and September 2002. Mean age was 69 years (51 to 83 years). Patients were previously assessed by a pain scale and Karnofsky index. They underwent bone scintigraphy, X-ray, dosage of prostate specific antigen (PSA) and biochemical tests before and following treatment (administration of intravenous clodronate every 28 days). The Student's t-test was used for statistical analysis.

RESULTS

Twenty-nine patients (90.6%) showed improvement after the first and the 2nd cycles, which persisted for at least 4 months. Average on the pain scale improved from 7.7 to 2.1 and Karnofsky index raised from 42 to 71. Radiological aspect of the metastases improved in 15 patients (46.8%) and side effects were low (only 2 patients - 6.2%).

CONCLUSION

Bisphosphonate was effective in the treatment of skeletal complications of prostate cancer, presenting an objective response in 90.6% of treated patients, with a marked improvement in the pain scale, Karnofsky index and consequently in the quality of life of patients, and with low side effects.

The potential role of bisphosphonates in prostate cancer

Skeletal morbidity secondary to metastases and osteoporosis is common in patients with advanced prostate cancer. Despite the typically sclerotic nature of prostate cancer metastases, osteoclast mediated osteolysis may play a significant role. This review addresses the newly recognised antitumour effects of bisphosphonates in addition to their role in inhibiting osteoclast mediated bone resorption. Both preclinical and clinical evidence of a role for bisphosphonates in the treatment and prevention of bone metastases secondary to prostate cancer is assessed.

Stromal factors involved in prostate carcinoma metastasis to bone

BACKGROUND

Prostate carcinoma (PC) frequently metastasizes to bone, where it causes significant morbidity and mortality. Stromal elements in the primary and metastatic target organs are important mediators of tumor cell intravasation, chemoattraction, adhesion to target organ microvascular endothelium, extravasation, and growth at the metastatic site.

METHODS

The role of stromal factors in bone metastasis was determined with a cyclic DNA microarray comparison of a bone-derived cell PC cell line with a soft tissue-derived cell PC cell line and by evaluating the effects of selected stromal components on PC cell chemotaxis, cell adhesion to human bone marrow endothelium (HBME), and PC cell growth.

RESULTS

The authors demonstrate that PC cells express protease-activated receptor 1 (PAR1; thrombin receptor), and its expression is up-regulated in PC compared with normal prostate tissue. In addition, this overexpression was very pronounced in bone-derived PC cell lines (VCaP and PC-3) compared with soft tissue PC cell lines (DUCaP, DU145, and LNCaP). The authors report that bone stromal factors, including stromal cell-derived factor 1 (SDF-1) and collagen Type I peptides, are chemoattractants for PC cells, and they demonstrate that some of these factors (e.g., extracellular matrix components, transforming growth factor beta, bone morphogenic proteins [BMPs], and SDF-1) significantly alter PC-HBME interaction in vitro. Finally, stromal factors, such as BMPs, can regulate the proliferation of PC cells in vitro.

CONCLUSIONS

Soluble and insoluble elements of the stroma are involved in multiple steps of PC metastasis to bone. The authors hypothesize that PAR1 may play a central role in prostate tumorigenesis.

Assessment of the effects of breast cancer on bone and the response to therapy

The skeleton is the most frequent site of metastatic disease in breast cancer and also the site of greatest morbidity. In addition, there is now recognition that accelerated bone loss associated with chemotherapy or hormonal therapy leads to an increased risk of osteoporosis in long-term breast cancer survivors. An improved range of treatment options is available and assessment of skeletal response both to the disease and to therapy is therefore of growing importance. Plain radiographs remain widely used to assess response, but are of limited sensitivity. The isotope bone scan is more sensitive, but lacks specificity. Computerised tomography, magnetic resonance imaging and positron emission tomography all have an increasing role. In treatment-induced osteoporosis, bone mineral density is now readily measured by DEXA scanning. Tumour markers such as CEA, CA 15-3, CA 549 and TPA may have a role in assessing response, but probably in combination rather than individually, using an appropriate quantitative model. Several trials have shown that bone markers, especially markers of bone resorption such as Ntx, Ctx, PYD and DPD, appear to have strong potential as rapid, convenient and inexpensive measures of response. There is also evidence that they may be used as predictive or prognostic indicators. Evidence is accumulating that the reduction of bone resorption markers into the normal range results in substantially reduced morbidity in metastatic breast cancer and that this should be a major target of therapy.

Bony pathology in the cancer patient

Bony pathology in the cancer patient represents a significant source of morbidity and mortality. Complications include insufficiency and pathological fractures resulting from either medical treatments or bony metastases that can cause significant functional limitations. Additional complications include spinal cord compression, hypercalcemia, and bone marrow failure. Rehabilitation management of such conditions is reviewed, with an emphasis on diagnostic and therapeutic management. Bracing and focused rehabilitation programs facilitate maximal participation and functional outcomes, which can result in an enhanced quality of life. Specific rehabilitation goals and strategies are discussed, with an emphasis on tailoring these according to the functional staging of the patient.

Strategies for management of prostate cancer-related bone pain

Prostate cancer is one of the most common malignancies and a leading cause of cancer-related death in men worldwide. In the majority of cases, prostate cancer metastases to the skeleton, in which case cancer-related bone pain becomes a major cause of morbidity. Androgen ablation is the treatment of choice for securing regression of skeletal metastases in the majority of cases. Intermittent androgen ablation is an attractive alternative, aimed at minimising adverse effects of hormone deprivation but also potentially delaying hormone-refractoriness. The development of hormone-refractoriness is heralded by a significant increase in morbidity largely because of escalating bone pain caused by the progression of the metastatic process. Skillful use of analgesics is initially successful but eventually fails to control symptoms. Localised metastases are best treated with local radiotherapy that is rapidly effective. Over the last few years, it has become clear that therapeutic modalities using bone-seeking radionuclides or bisphosphonates have been effective in the palliation of prostate cancer-related bone pain, although not affecting survival. The main limiting factor with the use of radionuclides is bone marrow suppression, also a feature of the very late stages of prostate cancer. Bisphosphonates do not carry this disadvantage. Results of large double-blind, placebo-controlled studies should be awaited, however, before advocating the widespread use of these agents in the management of patients with prostate cancer and skeletal metastases.

Canine prostate induces new bone formation in mouse calvaria: A model of osteoinduction by prostate tissue

BACKGROUND

Osteoblastic metastases are common in patients with advanced prostate cancer. The pathophysiology of the new bone formation at metastatic sites is not currently known, but it is hypothesized that growth factors secreted by the prostate may be involved. Unfortunately, most rodent models of prostate cancer with metastasis to bone are osteolytic and not osteoblastic. Significant osteolysis by tumor cells at metastatic sites may also lead to fractures or bone instability. Misinterpretation of new periosteal bone due to bone instability as tumor-cell osteoinduction is another disadvantage of the osteolytic models. To circumvent these problems, we have developed a model system of new bone formation in the calvaria of nude mice stimulated by normal canine prostate tissue.

METHODS

Collagenase-digested normal prostate tissue was implanted adjacent to the calvaria of nude mice. Calvaria were examined at 2 weeks post-implantation for changes in the bone microenvironment by histology, calcein uptake at sites of bone mineralization, and tartrate-resistant acid phosphatase staining for osteoclasts.

RESULTS

The prostate tissue remained viable and induced abundant new woven bone formation on the adjacent periosteal surface. In some cases new bone formation also was induced on the distant or concave calvarial periosteum. The new bone stained intensely with calcein, which demonstrated mineralization of the bone matrix. The new bone formation on prostate-implanted calvaria significantly increased (1.7-fold) the thickness of the calvaria compared with control calvaria. New bone formation was not induced in calvaria of mice implanted with normal canine kidney, urinary bladder, spleen, or skeletal muscle tissue, or mice with surgically-induced disruption of the periosteum. Osteoclast numbers in the medullary spaces and periosteum of calvaria were mildly increased (61%) in mice with implanted prostate tissue.

CONCLUSIONS

This animal model will be useful for investigating the roles of prostate-derived growth factors on new bone formation in vivo.

Receptor activator of nuclear factor-kappaB ligand and osteoprotegerin: potential implications for the pathogenesis and treatment of malignant bone diseases

BACKGROUND

The current review summarizes the roles of the ligand, receptor activator of nuclear factor-kappaB ligand (RANKL), its receptor, receptor activator of nuclear factor-kappaB (RANK), and its decoy receptor, osteoprotegerin (OPG), on osteoclast biology and bone resorption. Furthermore, it highlights the impact of these compounds on the pathogenesis of malignant bone diseases, including tumor metastasis, humoral hypercalcemia of malignancy, and multiple myeloma. Finally, the authors discuss the therapeutic potential of OPG in the management of malignancies involving the skeleton.

METHODS

After its discovery and cloning, the biologic effects of RANKL, RANK, and OPG have been characterized by in vitro experiments and in vivo studies. The generation of knock-out mice and transgenic mice has produced animal models with absent or excessive production of these cytokine components that display opposite abnormal skeletal phenotypes (osteoporosis or osteopetrosis). The potential effect of RANKL and OPG has been assessed by evaluating these compounds in various animal models of metabolic and malignant bone disease and by administering OPG to humans.

RESULTS

Abnormal bone resorption due to local or systemic stimulation of osteoclast differentiation and activation is a hallmark of various benign and malignant bone diseases. RANKL, RANK, and OPG form an essential cytokine system that is capable of regulating all aspects of osteoclast functions, including proliferation, differentiation, fusion, activation, and apoptosis. The balance of bone resorption depends on the local RANKL-to-OPG ratio, which is enhanced in bone metastases and humoral hypercalcemia of malignancy. The exogenous administration of OPG to tumor-bearing animals corrects the increased RANKL-to-OPG ratio, and reverses the skeletal complications of malignancies.

CONCLUSIONS

Abnormalities of the RANKL/OPG system have been implicated in the pathogenesis of various primary and secondary bone malignancies. The systemic administration of OPG appears to be a potent novel therapeutic agent for treatment of these disorders.

A matrix metalloproteinase inhibitor, batimastat, retards the development of osteolytic bone metastases by MDA-MB-231 human breast cancer cells in Balb C nu/nu mice

Bone resorption is a dominant feature of many bone metastases and releases factors from the bone matrix that can promote the expression of the metastatic phenotype in cancer cells. Since proteolytic enzymes, including matrix metalloproteinases (MMPs) contribute to bone destruction by metastatic tumour cells and host cells, we have examined the effect of a MMP inhibitor, batimastat, on the ability of MDA-MB-231 cells to degrade bone in vitro and to form bone metastases in BalbC nu/nu mice. In vitro, the neoplastic cells produced MMP-2 and MMP-9, degraded [3H]-proline-labelled osteoblast matrices, and formed resorption pits in cortical bone. These phenomena were inhibited by < or = 20 microM batimastat. To induce vertebral and long bone metastases in vivo, 1x10(5) MDA-MB-231 cells were injected into the arterial circulation of BalbC nu/nu mice. Test groups were also given 30 mg/kg batimastat intraperitoneally (i.p.). After 21 days, the long bone metastases were characterised by a 67% reduction of metaphyseal medullary bone and complete replacement of marrow by tumour. In tumour-bearing mice that had been treated with 30 mg/kg batimastat i.p., the tumour volume decreased 8-fold, osteolysis was inhibited by 35%, and replacement of the bone marrow by tumour was inhibited by 65%. Similar effects were observed in the vertebral metastases. These data provide evidence that MDA-MB-231 cells can degrade osteoblast matrices and mineralised bone in vitro and support the hypothesis that MMPs are involved in the pathogenesis of osteolytic bone metastases in vivo. They demonstrate that an agent which inhibits proteolysis can retard the development of osteolytic bone metastases in this model.