Osteoblastic Component Research Articles

Abstract 2824: Establishing prostate cancer models for orthotopic and bone metastatic growth using the 22Rv1cell line

Abstract Prostate cancer is the second most common cancer in men with new cases diagnosed in 1.4 million men each year. Luckily the 5-year survival rates in developed countries are high reaching over 90%. However, approximately one third will develop a metastatic disease. In metastatic patients, prostate cancer almost always progresses despite the androgen deprivation therapy and is then referred to as “castration-resistant (mCRPC)”. Bone is involved in 80% of patients with metastasis, and the bone lesions are typically osteoblastic. The 22Rv1 human prostate carcinoma cell line is androgen sensitive and shown to express androgen receptor (AR). They also express low levels of prostate-specific membrane antigen (PSMA). The aim of this study was to establish orthotopic and intratibial preclinical in vivo prostate cancer models that can be used in drug development when targeting cancer cells and their local environment. Male athymic nude mice (5-6 weeks old) and NOG mice (over 20 weeks old) were used in the study. 2.5 × 105 22Rv1 cells (ATCC) were inoculated orthotopically into the prostate of NOG mice, and 5 × 105 cells were inoculated intratibially into the bone marrow cavity of athymic nude mice. Tumor growth was followed by PSA measurements every second week using Human PSA ELISA assay. In addition, in the intratibial model, tumor-induced bone changes were monitored by X-ray imaging of the hind limbs. Prostates and hind limbs were collected at sacrifice, fixed in 10% NBF, and processed to paraffin blocks for further histological analysis. Sections of prostate were stained with hematoxylin-eosin (HE) and AR. Tumor-bearing and contralateral (healthy) tibias were stained with HE - OrangeG, MGT, TRAP, and AR. The observed tumor take rate was 92% in the orthotopic and 100% in the intratibial models. Confirmed by IHC, tumors formed in both the orthotopic and intratibial models expressed AR. 22Rv1 cells formed osteoblastic - lytic mixed bone lesions in the intratibial model. Based on lesion areas, randomization of the tumor bearing mice in the intratibial model can be done after 2 weeks from cancer cell inoculation. Taken together, the 22Rv1 prostate cancer models are relatively fast growing, express AR and present good take rates. Furthermore, the intratibial model represents robust tumor-induced changes in bone with strong osteoblastic component. Thus, these models have several advantages in efficacy studies of novel drug candidates for prostate cancer. Citation Format: Justyna Zdrojewska, Katja Fagerlund, Jenni H. Mäki-Jouppila, Mari I. Suominen. Establishing prostate cancer models for orthotopic and bone metastatic growth using the 22Rv1cell line [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2824.

Morphogen signaling by Wnt/β-catenin pathway and microenvironmental alteration in the bone marrow of agricultural pesticide exposure-induced experimental aplastic anemia.

The etiologic link between pesticide toxicity and aplastic anemia in agricultural and agro-industrial setting has been frequently reported in epidemiological studies conducted worldwide. Chronic pesticide toxicity causes long-term bone marrow injury and perturbs the normal hematopoietic physiology, including survival of hematopoietic progenitor cells and bone marrow's blood cell forming ability. The purpose of this study is to understand the mechanism of pesticide toxicity-mediated bone marrow aplasia by studying Wnt/β-catenin signaling pathway and microenvironmental stromal components. An agricultural pesticide formulation comprising of cypermethrin, chlorpyriphos, and hexaconazole was used to induce bone marrow aplasia in inbred Swiss albino mice. Marrow failure followed by the onset of aplastic condition was confirmed by pancytopenic peripheral blood and hypocellular bone marrow filled with adipocytes. Significant downregulation of canonical Wnt/β-catenin signaling was identified by expression analysis of Wnt3a, β-catenin, and telomerase reverse transcriptase in the aplastic bone marrow hematopoietic stem/progenitor compartment. Along with signaling deregulation, disruption in both the osteoblastic and vascular stromal components was observed in the pesticide-exposed bone marrow microenvironment when compared to control. In this study, we tried to establish the correlation among disease pathophysiology, signaling deregulation in the hematopoietic cells, and bone marrow microenvironmental alteration during environmental exposure-mediated aplastic hematopoietic catastrophe, which may shed light on the unexplored mechanistic perspective of this fatal blood disease.

Metaplastic woven bone in bone metastases: A Fourier-transform infrared analysis and imaging of bone quality (FTIR)

Most osteolytic tumors are in fact mixed and contain an osteoblastic component associated with the predominant osteolytic areas. This metaplastic woven bone is always evidenced by histological analysis even in the absence of radiological expression. Metaplastic bone formation reflects the activation of new osteoblasts coming from the stimulation of the dormant lining cells. Twelve patients with secondary metastases of the iliac crest evidenced by hot spots on a 99Tc-MBP san were diagnosed by histomorphometry on bone biopsies. Fourier Transformed InfraRed analysis and Imaging (FTIRI) was used on 4μm thick sections of undecalcified bone. The mineralization degree, carbonate substitution, crystallinity and the cross-links ratio of collagen (1660/1690cm-1 bands) were determined. The matrix characteristics were analyzed and imaged in the pre-existing residual bone and in the metaplastic woven bone in the vicinity of the tumor cells. FTIRI provided images of the phosphate, amide and combination of peak ratio after having selected the peaks of interest. In addition, the matrix properties can be measured and compared between the old and newly-formed bones. Woven bone appeared poorly calcified with a low phosphate/amide ratio (P=0.03) crystallinity (P<0.0001) and carbonate substitution (P=0.003). Collagen was less mature as evidenced by lower cross-links (P=0.01). Woven bone associated with bone metastasis appears poorly mineralized and rapidly elaborated by osteoblasts. The collagenous phase of the bone matrix has a low level of reticulation. FTIRI is a powerful tool to measure and visualize the various components of the bone matrix in human diseases.

Abstract 876: Imaging the interaction of leukemia and bone marrow microenvironment in murine model of ALL

Abstract Interactions of leukemia and the bone marrow (BM) microenvironment are known to play a key role in the survival and growth of leukemic cells, and we have shown that HIF-1α stabilization in BM stromal cells facilitates leukemia homing and progression (Chen et al. Blood 2012, 119:4971). Leukemic cells have been shown to hijack the homeostatic mechanisms of normal hematopoietic stem cells (HSCs) and take refuge within the BM niche. This mechanism is pivotal during chemotherapy and contributes to disease relapse. In this study, we aimed to characterize the time-dependent progression of BM hypoxia involving both acute lymphocytic leukemia (ALL) cells and components of the BM niche, using multiphoton intravital microscopy (MP-IVM) . We generated a transplantable, fluorescent leukemia model by retrovirally transducing C57Bl6-Ai14 murine BM cells that express red fluorescing tdTomato with the p190-Bcr/Abl oncogene (KG Harutyunyan et al, Blood 2014 124:2396). The resulting p190-Bcr/Abl tdTomato cells caused rapid development of ALL in non-irradiated C57Bl6 immunocompetent mice, manifested by infiltration of multiple organ and BM sites, followed by death within 14-18 days. We utilized Col2.3-GFPemd transgenic mice as recipients of leukemia to highlight the osteoblastic niche, and visualized vasculature by injection of TRITC-dextran. We showed the dynamic of homing and engraftment of ALL leukemic B cells (LBC) in OB-GFP recipient mice, with homing in the vicinity of blood vessels visualized by MP-IVM, followed by proliferation and leukemia expansion. This was accompanied by invasion of both vascular and osteoblastic components of BM microenvironment. Longitudinal assessment of hypoxia utilizing pimonidazole staining showed progressive development of BM hypoxia starting from Day 10 p.i., paralleling leukemia progression, despite the abundant vascularization of the BM. To assess the integrity of the BM vascular niche during leukemia progression the experimental mice were intravitally injected with low doses of an Alexa-Fluor-647-conjugated VE-cadherin antibody (MG. Poulos et al, Epub 2013 Sep 5) to visualize the number and morphology of the perfused vessels and to analyze the architecture of the hematopoietic compartment. We observed that at late stage of leukemia progression (day 12-14 p.i) BM vessels are disorganized as a result of expansion of leukemic B cells. Ongoing longitudinal imaging experiments will characterize the cellular origin of hypoxic niche cells and the dynamic of vasculature alteration in ALL. In summary, these findings demonstrate rapid development of intra-BM hypoxia that parallels leukemia progression and involves interactions between leukemia cells and BM niche cells, as well as disordered vasculature. Citation Format: Karine G. Harutyunyan, Saradhi Mallampati, Anna Zal, Mateusz Rytelewski, Michael C. Gutkin, Jason M. Butler, Tomasz Zal, Marina Konopleva. Imaging the interaction of leukemia and bone marrow microenvironment in murine model of ALL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 876. doi:10.1158/1538-7445.AM2017-876

Chapter Three - Procollagen Assays in Cancer

The synthesis rates of fibrillar collagens can be assessed in blood by measuring propeptides set free from corresponding procollagens before fiber formation. Type I collagen is the major component of the organic matrix of bone, but it is also found in other connective tissues. The serum concentration of the amino-terminal propeptide of type I procollagen, PINP, functions as a measure of type I collagen synthesis during normal bone turnover, but it is also released from bone metastases that involve an osteoblastic component. Type III collagen is a major constituent of soft tissues and the corresponding amino-terminal propeptide, PIIINP, reflects collagen synthesis. Circulating PIIINP tends to be affected by malignomas that grow in the peritoneal cavity or affect bone marrow. Many studies on procollagen markers in cancer have been cross-sectional or demonstrated treatment effects in patient groups. Markers that originate from bone turnover have wide reference intervals, but low biologic variability in individuals. Thus, they appear better suited for monitoring versus diagnostic purposes. There is still definite need for research on the use of procollagen markers in the followup of individual patients undergoing cancer treatment or being monitored after such treatment.

Role of Circulating Osteogenic Progenitor Cells in Calcific Aortic Stenosis

The purpose of this study was to determine the role of circulating endothelial progenitor cells with osteoblastic phenotype (EPC-OCN) in human aortic valve calcification (AVC). Recent evidence suggests that rather than passive mineralization, AVC is an active atherosclerotic process with an osteoblastic component resembling coronary calcification. We have recently identified circulating EPCs with osteogenic properties carrying both endothelial progenitor (CD34, KDR) and osteoblastic (osteocalcin [OCN]) cell surface markers. Blood samples from controls (n = 22) and patients with mild to moderate calcific aortic stenosis (mi-moAS, n = 17), severe calcific AS (sAS, n = 26), and both sAS and severe coronary artery disease (sCAD) (n = 33) were collected during diagnostic coronary angiography. By using flow cytometry, peripheral blood mononuclear cells were analyzed for CD34, KDR, and OCN. Resected normal and calcified aortic valves were analyzed histologically. Patients with mi-moAS and patients with sAS/sCAD had significantly less EPCs (CD34+/KDR+/OCN-) than controls. Patients with sAS showed significantly higher numbers of EPC-OCN (CD34+/KDR+/OCN+) than controls. In addition, the percentage of EPC costaining for OCN was higher in all disease groups compared with controls. A subgroup analysis of younger patients with bicuspid sAS showed a similar pattern of significantly lower EPCs but a high percentage of coexpression of OCN. Immunofluorescence showed colocalization of nuclear factor kappa-B and OCN in diseased and normal valves. CD34+/OCN+ cells were abundant in the endothelial and deeper cell layers of calcific aortic valve tissue but not in normal aortic valve tissue. Circulating EPC-OCN may play a significant role in the pathogenesis and as markers of prognostication of calcific AS.

Rapidly deforming gastric carcinosarcoma with osteoblastic component: An autopsy case report

Carcinosarcomas are rare, malignant, biphasic tumors simultaneously comprising carcinoma and sarcoma in a single tumor. We present an extremely rare case of gastric carcinosarcoma with an osteoblastic component that drastically changed its shape within 2 mo. A 59-year-old male patient presented to the emergency outpatient unit with a complaint of black stool. Gastrointestinal endoscopy showed an ulcerated mass in the cardia of the lesser curvature of the stomach. Biopsy specimens revealed only adenocarcinoma. Two months later, the ulcerated lesion drastically changed its shape into an exophytic tumor. Total gastrectomy was performed. In the resected specimen, the gastric tumor contained both adenocarcinoma and sarcoma components with lace-like osteoid. The patient died 7 mo after the operation, and an autopsy was performed. In the autopsy, widespread metastases were present in the liver, lung, lymph nodes and peritoneum. In this report, we describe a case of gastric carcinosarcoma and presume its tumorigenesis based on the autopsy findings.

Peripheral cannabinoid type 2 receptor regulates osteoclast formation, MDA-MB-231 breast cancer cell migration and bone marrow/tumour cell interaction via PI3 kinase/AKT and P38 pathways

The skeleton is the most common site of metastasis in human prostate cancer (PCa). Through over-expression of the Wnt inhibitor Dickkopf-1 (DKK-1), we previously demonstrated that Wnts contribute to the osteoblastic component of PCa skeletal metastases. Herein, we demonstrate that knock-down of DKK-1 using shRNA in osteolytic PC-3 PCa cells delayed the development of both soft tissue and osseous lesions compared to DKK-1+ control shRNA cells. Similarly, systemic treatment with a DKK-1 neutralizing antibody decreased overall tumor burden following intracardiac injection of PC-3 cells 8.3-fold compared to IgG-treated control mice (p<0.028) demonstrating that DKK-1 facilitates tumor growth. DKK-1 shRNA transfected cells were found to have increased expression of the cyclin dependent kinase inhibitor p21CIP1/WAF1 (CDKN1A) and a 32% increase in G1 arrest compared to DKK-1+ shcontrol transfected cells. Simultaneous knock-down of p21 accelerated tumor growth of DKK-1 shRNA transfected cells in vivo suggesting that DKK-1 knock-down led to p21-mediated suppression of cell cycle and tumor growth. Taken together, the data support the hypothesis that DKK-1 expression in PCa cells facilitates tumor growth by blocking Wnt-mediated suppression of cell cycle through p21.

P21CIP-1/WAF-1 Induction Is Required to Inhibit Prostate Cancer Growth Elicited by Deficient Expression of the Wnt Inhibitor Dickkopf-1

Osteoblastic bone metastases are the most common metastases produced by human prostate cancers (PCa). Deregulated activity of Wnt growth factors resulting from overexpression of the Wnt inhibitor Dickkopf-1 (DKK-1) is known to contribute to formation of the osteoblastic component of PCa skeletal bone metastases. In this study, we report that DKK-1 knockdown in osteolytic human PCa cells unexpectedly delays the development of both soft tissue and osseous lesions. PCa cells deficient in DKK-1 expression did not increase canonical Wnt signaling in target osteoblast cell lines; however, DKK-1 knockdown PCa cells exhibited increased expression of the CDK inhibitor p21(CIP1/WAF1) and a 32% increase in G(1) arrest compared with control cells. Ablating p21(CIP1/WAF1) in PCa cells deficient in DKK-1 was sufficient to rescue tumor growth. Collectively, our findings demonstrate that DKK-1 overexpression supports tumor growth in part by restricting expression of p21(CIP1/WAF1) through a mechanism independent of canonical Wnt signaling.

Combined inhibition of the BMP pathway and the RANK-RANKL axis in a mixed lytic/blastic prostate cancer lesion

The purpose of this study was to investigate the influence of combined inhibition of receptor activator of nuclear factor kappa-B ligand (RANKL) and bone morphogenetic protein (BMP) activity in a mixed lytic/blastic prostate cancer lesion in bone. Human prostate cancer cells (C4 2b) were injected into immunocompromised mice using an intratibial injection model to create mixed lytic/blastic lesions. RANK-Fc, a recombinant RANKL antagonist, was injected subcutaneously three times a week (10 mg/kg) to inhibit RANKL and subsequent formation, function and survival of osteoclasts. Inhibition of BMP activity was achieved by transducing prostate cancer cells ex vivo with a retroviral vector expressing noggin (retronoggin; RN). There were three treatment groups (RANK-Fc treatment, RN treatment and combined RN and RANK-Fc treatment) and two control groups (untreated control and empty vector control for the RN treatment group). The progression of bone lesion and tumor growth was evaluated using plain radiographs, hindlimb tumor size, 18F-Fluorodeoxyglucose and 18F-fluoride micro PET-CT, histology and histomorphometry. Treatment with RANK-Fc alone inhibited osteolysis and transformed a mixed lytic/blastic lesion into an osteoblastic phenotype. Treatment with RN alone inhibited the osteoblastic component in a mixed lytic/blastic lesion and resulted in formation of smaller osteolytic bone lesion with smaller soft tissue size. The animals treated with both RN and RANK-Fc demonstrated delayed development of bone lesions, inhibition of osteolysis, small soft tissue tumors and preservation of bone architecture with less tumor induced new bone formation. This study suggests that combined inhibition of the RANKL and the BMP pathway may be an effective biologic therapy to inhibit the progression of established mixed lytic/blastic prostate cancer lesions in bone.

Therapeutic Approach of Primary Bone Tumours by Bisphosphonates

Bone tumours can be dissociated in two main categories: i) primary bone tumours (benign or malignant) including mainly osteosarcoma and other sarcomas.ii)and giant cell tumour and bone metastases originate from others cancer (Breast, prostate, kidney cancer, etc). These tumours are able to destroy or/and induce a new calcified matrix. However, the first step of bone tumour development is associated with an induction of bone resorption and the establishment of a vicious cycle between the osteoclasts and the tumour growth. Indeed, bone resorption contributes to the pathogenesis of bone tumour by the release of cytokines (IL6, TNFα) which govern the bone tumour's development and which are trapped into the bone matrix. Bisphosphonates (BPs) are chemical compounds of P-C-P structure with a high affinity for bone hydroxyapatite crystals. Thus, they have been used as a carrier for radio nucleotides to develop novel approaches of bone imaging. BPs exert also indirect anti-tumour activities in vivo. Indeed, BPs directly interfere with the bone microenvironment and target osteoclasts, endothelial cells and immune cells (tumour-associated macrophages, γ9δ2 T cells). BPs induce tumour cell death in vitro and same activity is suspected in vivo. The present review summarizes the mechanisms of actions of BPs as well as their clinical interests in bone primary tumours.

Abstract 4321: A four-pronged imaging approach to characterization of bone metastasis in mouse models

Abstract Introduction: The process of bone metastasis involves both osteoblastic and resorptive components and is a common feature of both prostate and breast cancers. The ability to visualize and quantify the early stages of bone involvement in mouse models of bone metastasis would provide a platform for development of new agents targeted at inhibition or treatment of bone metastases. Two approaches that stand to enable this are 18F-NaF PET and optical imaging using biphosphonate fluorescent probes such as Osteosense, through targeting of hydroxyapatite (HA), a biomarker for osteoblastic activity. Additionally, bioluminescence imaging using luciferase expressing tumor lines and micro-CT imaging of the skeleton can enable anatomic characterization of tumor burden and development of bone lesion in bone metastasis models. Methods: MDA-MB-231-luc-D3H2LN human mammary adenocarcinoma cells (105 cells in 100µl) were injected into the left ventricle of female nu/nu mice on Day 0 approximately 6-7min after IP injection of luciferin (150mg/kg). Bioluminescence scans were used to determine successful injection by distribution of light throughout the body. On Day 14, all tumor pool mice were imaged using bioluminescence and enrolled on study based on incidence of luciferase signals at bone sites. After staging, serial bioluminescence imaging was used to localize tumor signals and determine incidence and growth of bone metastases and micro-CT was used to image the extent of bone lesions associated with the metastases. Additionally, whole body PET scans were used at multiple time points after 90min uptake of 18F-NaF. Images were reconstructed using a 2D OSEM method and localized bone sites segmented and analyzed for standardized uptake value (SUV). Fluorescence imaging was also used 24h after administration of Osteosense 750 to characterize localization of the tracer at the bone sites of interest. After background correction, the bone sites of interest were segmented and analyzed for average efficiency. The 18F-NaF and Osteosense endpoints were correlated with bioluminescence determined tumor burden and location. Results and Discussion: Both 18F-NaF PET imaging and fluorescent imaging using Osteosense highlighted localized bone signals that could be correlated with bioluminescent signals and micro-CT visualized bone lesions from approximately Day 17. Both the PET and fluorescence imaging approaches showed early indication of bone involvement, presumably through HA, indicating osteoblastic activity. This multi-endpoint approach enabled non-invasive determination of both soft tumor and bone components of metastatic bone disease. An approach like this may enable more quantitative characterization of the early stages of bone metastasis in mouse models, and facilitate development of bone targeted treatments. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4321.

Abstract C9: An in vitro model of osteoblastic bone metastasis in prostate cancer

Abstract Prostate cancer progression is characterized by a striking affinity to spread to bone, where it forms metastases predominately of an osteoblastic phenotype, resulting in a significant source of morbidity. Currently, animal models for studying the development of these osteoblastic metastases are limited due to a lack of spontaneous osteoblastic metastasis development. In order to recapitulate osteoblastic metastasis development, an in vitro, three dimensional culture system was created utilizing silk fibroin scaffolds. LNCaP cells were seeded to silk scaffolds with human bone marrow derived mesenchymal stem cells (hMSCs) and cultured for 6 weeks. Examination after co-culture revealed through histological analysis that hMSCs underwent osteogenic differentiation in response to LNCaP paracrine signals. Paracrine interactions between hMSCs and LNCaPs were studied and IL-6, known to promote androgen independent growth, was found to be transiently expressed by hMSCs over the first two weeks of co-culture. In addition to secreted soluble signaling factors, the effect of extracellular matrix signals on the LNCaP cells was examined. LNCaP cells grown in a decellularized matrix, derived from hMSCs having undergone osteogenic differentiation, showed a 12 fold survival advantage in androgen depleted conditions over controls. This data indicates the ability of the co-culture system to stimulate differentiation of hMSCs towards an osteogenic linage and release soluble and extracellular matrix cues which stimulate androgen independent disease progression. The in vitro co-culture system presents a scalable and high throughput method for studying the molecular mechanisms underlying the osteoblastic component of prostate cancer bone metastasis. Citation Information: Cancer Res 2009;69(23 Suppl):C9.

Zoledronic Acid Inhibits Both the Osteolytic and Osteoblastic Components of Osteosarcoma Lesions in a Mouse Model

To evaluate the efficacy of zoledronic acid (ZOL) against osteosarcoma (OS) growth, progression, and metastatic spread using an animal model of human OS that closely resembles the human disease. Human K-HOS or KRIB OS cells, tagged or untagged with a luciferase reporter construct, were transplanted directly into the tibial cavity of nude mice. ZOL was given as weekly, or a single dose of 100 microg/kg body weight, equivalent to the 4 mg i.v. dose used clinically. Tumor growth at the primary site and as pulmonary metastases was monitored by bioluminescence imaging and histology, and OS-induced bone destruction was measured using high-resolution micro-computed tomography. Mice transplanted with OS cells exhibited aberrant bone remodeling in the area of cancer cell transplantation, with areas of osteolysis mixed with extensive new bone formation extending from the cortex. ZOL administration prevented osteolysis and significantly reduced the amount of OS-induced bone formation. However, ZOL had no effect on tumor burden at the primary site. Importantly, ZOL failed to reduce lung metastasis and in some cases was associated with larger and more numerous metastatic lesions. Our data show that clinically relevant doses of ZOL, while protecting the bone from OS-induced bone destruction, do not inhibit primary tumor growth. Moreover, lung metastases were not reduced and may even have been promoted by this treatment, indicating that caution is required when the clinical application of the bisphosphonate class of antiresorptives is considered in OS.

Zoledronic acid inhibits both the osteolytic and osteoblastic components of osteosarcoma lesions in both an immunodeficient and immunocompetent animal model

Zoledronic acid inhibits both the osteolytic and osteoblastic components of osteosarcoma lesions in both an immunodeficient and immunocompetent animal model

Src as a therapeutic target in men with prostate cancer and bone metastases

While responsive to androgen ablation in its early stages, prostate cancer eventually becomes castration-resistant and metastasizes preferentially to bone. Once this happens, the disease carries considerable morbidity and is incurable. The process of bone metastasis involves a complex interplay between tumour and bone tissue. The eventual characteristic clinical presentation of disorganized osteoblastic bone lesions is preceded by a facilitatory osteoblastic phase; an osteoblastic component then continues to underlie the process. Increasing evidence has shown a ubiquitous role for Src (a proto-oncogene tyrosine-protein kinase) in multiple tumour and bone-signalling processes involved in prostate tumour progression, driving proliferation, survival, migration and transition to androgen-independent growth. It is also intimately involved in positively regulating osteoclast physiology. As such, this molecule represents an attractive target for managing progressing prostate cancer. Encouraging results have been obtained in preclinical and clinical studies using Src inhibitors like AZD0530 and dasatinib. Both compounds reduced markers of bone resorption, in patients with cancer and those with advanced castration-resistant prostate cancer, respectively. Moreover, because Src is central to many mechanisms thought to be responsible for the development of castration resistance, adding Src inhibitors to a treatment regimen might reverse this phenomenon. As a result, many Src inhibitors are in preclinical development. This review explores Src inhibition as a strategy for managing bone metastasis in prostate cancer, with a particular focus on targeting the critical osteoclastic response. Other emerging and novel approaches are also considered.

Dickkopf‐1 expression increases early in prostate cancer development and decreases during progression from primary tumor to metastasis

Prostate cancer (PCa) frequently metastasizes to the bone and induces osteoblastic lesions. We previously demonstrated through over-expression of the Wnt inhibitor dickkopf-1 (DKK-1) that Wnts contribute to the osteoblastic component of PCa osseous lesions in vivo. To test the clinical significance of DKK-1 expression during PCa progression, tissue microarrays were stained for DKK-1 protein by immunohistochemistry. DKK-1 expression index (EI) was found to increase in PIN and primary lesions compared to non-neoplastic tissue (106 +/- 10 vs. 19 +/- 6, respectively, where the EI is the product of the percent expression and staining intensity). DKK-1 expression was also found to be higher in all PCa metastatic lesions (56 +/- 21 EI) compared to non-neoplastic tissues but was significantly decreased versus primary PCa lesions (P < 0.008). The decline in DKK-1 correlated with a shift of beta-catenin staining from the nucleus to the cytoplasm suggesting possible mechanism for the observed decrease in DKK-1 levels during PCa progression. Within metastatic lesions, DKK-1 expression was least abundant in PCa bone metastases relative to all soft tissue PCa metastatic lesions except lymph node metastases. High DKK-1 expression within PCa metastases was further associated with shorter over-all patient survival. Taken together, these data demonstrate that elevated DKK-1 expression is an early event in PCa and that as PCa progresses DKK-1 expression declines, particularly in advanced bone metastases. The decline of DKK-1 in bone metastases can unmask Wnts' osteoblastic activity. These data support a model in which DKK-1 is a molecular switch that transitions the phenotype of PCa osseous lesions from osteolytic to osteoblastic.

BMP7: A New Bone Metastases Prevention?

Prostate cancer is the most frequently diagnosed cancer in men and a leading cause of cancer death. More than 218,000 cases will occur in 2007, and prostate cancer will lead to more than 27,000 deaths.1 Although the 5-year survival rate is excellent for localized stages (100%), the relative survival rapidly decreases to 33% when prostate cancer metastasizes.1 Cancer cells from prostate primary tumors commonly colonize bones, and postmortem analyses show that 65 to 75% of patients with advanced disease have bone metastases.2 Scientific knowledge of bone metastasis pathophysiology has increased in recent years, but effective therapy for this devastating complication of cancer remains suboptimal. In this issue of The American Journal of Pathology, Buijs and colleagues3 shed more light into pathophysiology of bone metastases. More importantly, they apply this knowledge to develop novel therapy for bone metastases using bone morphogenetic protein 7 (BMP7).

The Bisphosphonate YM529 Inhibits Osteolytic and Osteoblastic Changes and CXCR-4–Induced Invasion in Prostate Cancer

Bisphosphonates are useful for the treatment of prostate cancer bone metastasis. However, the role of bisphosphonate on the development of the osteoblastic component of prostate cancer bone metastases is not defined. In the present study, the third-generation bisphosphonate, YM529 (minodoronate), was tested for its effects on the osteolytic PC-3 and novel osteoblastic LNCaP-SF cell lines. YM529 inhibited both osteolytic and osteoblastic changes in an intratibial tumor injection murine model. In vitro, YM529 inhibited both the proliferation and the invasion of both prostate cancer cell lines. The stromal cell-derived factor-1 (or CXCL12)/CXCR-4 pathway is believed to play an important role in the development of prostate cancer bone metastases. Thus, we determined if YM529 affected this pathway. YM529 suppressed CXCR-4 expression in PC-3 and LNCaP-SF in vitro and in vivo and this was associated with decreased in vitro invasion. These results suggest that YM529 may inhibit cancer cell invasion into the bone matrix by repressing the expression of CXCR-4 in bone metastasis lesions.

Lower Extremity Swelling after Treatment for Thigh Synovial Sarcoma

Lower Extremity Swelling after Treatment for Thigh Synovial Sarcoma