Overexpression of noggin inhibits BMP-mediated growth of osteolytic prostate cancer lesions

Co-evolution of breast-to-brain metastasis and neural progenitor cells

Brain colonization by metastatic tumor cells offers a unique opportunity to investigate microenvironmental influences on the neoplastic process. The bi-directional interplay of breast cancer cells (mesodermal origin) and brain cells (neuroectodermal origin) is poorly understood and rarely investigated. In our patients undergoing neurosurgical resection of breast-to-brain metastases, specimens from the tumor/brain interface exhibited increased active gliosis as previously described. In addition, our histological characterization revealed infiltration of neural progenitor cells (NPCs) both outside and inside the tumor margin, leading us to investigate the cellular and molecular interactions between NPCs and metastases. Since signaling by the TGF-β superfamily is involved in both developmental neurobiology and breast cancer pathogenesis, we examined the role of these proteins in the context of brain metastases. The brain-metastatic breast cancer cell line MDA-MB-231Br (231Br) expressed BMP-2 at significantly higher levels compared to its matched primary breast cancer cell line MDA-MB-231 (231). Co-culturing was used to examine bi-directional cellular effects and the relevance of BMP-2 overexpression. When co-cultured with NPCs, 231 (primary) tumor cells failed to proliferate over 15 days. However, 231Br (brain metastatic) tumor cells co-cultured with NPCs escaped growth inhibition after day 5 and proliferated, occurring in parallel with NPC differentiation into astrocytes. Using shRNA and gene knock-in, we then demonstrated BMP-2 secreted by 231Br cells mediated NPC differentiation into astrocytes and concomitant tumor cell proliferation in vitro. In xenografts, overexpression of BMP-2 in primary breast cancer cells significantly enhanced their ability to engraft and colonize the brain, thereby creating a metastatic phenotype. Conversely, BMP-2 knockdown in metastatic breast cancer cells significantly diminished engraftment and colonization. The results suggest metastatic tumor cells create a permissive neural niche by steering NPC differentiation toward astrocytes through paracrine BMP-2 signaling.

In vivo inhibition of bone morphogenetic protein-2 on breast cancer cell growth

STUDY DESIGN

In vitro and in vivo study.

OBJECTIVE

To evaluate the role of recombinant human bone morphogenetic protein-2 (rhBMP2) on breast cancer cell (MDA-MB-231 cells) growth.

SUMMARY OF BACKGROUND DATA

Bone morphogenetic proteins (BMPs) are expressed in a variety of human carcinoma cell lines and are known to promote tumor invasion and metastasis. However, their roles in tumor progression have not been fully clarified. In addition, there is no in vivo study regarding the inhibitory effect of BMP2 on breast cancer cell proliferation.

METHOD

Cell proliferation was determined by BrdU incorporation assay and flow cytometry. BMP2 signal transduction pathways were estimated on Western blot. Fifteen animals were divided into 2 groups; 1 (control = 5) was breast cancer cells alone, while the other (experiment = 5) was rhBMP2 + breast cancer cells. Cancer cells were injected into 2 sites (subcutaneous and femur) of nude mice with or without BMP2. Tumor size was determined by direct measurements for subcutaneous tumor formation and by femur radiographs. Histological and immunohistochemical analyses were performed.

RESULTS

RhBMP2 inhibited the proliferation of MDA-MB-231 cells in vitro. Inhibition was associated with changes in both the Smad and Wnt signaling pathways and was ultimately mediated through effects on various cell cycle proteins. Furthermore, rhBMP2 inhibited the growth of MDA-MB-231 cells injected both subcutaneously and intrafemorally.

CONCLUSION

In this model using human breast adenocarcinoma cell line, rhBMP2 has no stimulatory effect of tumor growth. Therefore, we can provide the basic science data to support the utilization in the management of patients with spine tumor in the future.

Orthotopic expression of noggin protein in cancer cells inhibits human lung carcinoma growth in vivo

PURPOSE

We explored the effect of Noggin protein expression on tumor growth in vivo by using fluorescence imaging.

PROCEDURES

Human lung carcinoma MV522 cells were transduced by using bicistronic (EGFP/Nog) or a control (EGFP) lentivirus at >95% efficacy. The transduced cells were implanted in athymic mice either individually or after mixing with DsRed2-expressing MV522 cells.

RESULTS

The expression of Noggin protein was demonstrated in EGFP+/Nog+ but not in EGFP+ cell lysates and conditioned media. Noggin did not inhibit tumor cell proliferation in vitro. Implantation of EGFP+ resulted in rapid tumor growth, whereas mice implanted with EGFP+/Nog+ either failed to develop tumors or developed smaller slowly proliferating ones. In the case of tumors grown from mixtures with DsRed2+ cells, only Noggin-expressing cells resulted in decreased tumor volumes with low vascular density and poorly developed stroma.

CONCLUSION

The effect of Noggin protein expression is a consequence of inhibition of stromal and/or endothelial proliferation in vivo.

Prostate cancer cells and bone stromal cells mutually interact with each other through bone morphogenetic protein-mediated signals

Functional interactions between cancer cells and the bone microenvironment contribute to the development of bone metastasis. Although the bone metastasis of prostate cancer is characterized by increased ossification, the molecular mechanisms involved in this process are not fully understood. Here, the roles of bone morphogenetic proteins (BMPs) in the interactions between prostate cancer cells and bone stromal cells were investigated. In human prostate cancer LNCaP cells, BMP-4 induced the production of Sonic hedgehog (SHH) through a Smad-dependent pathway. In mouse stromal MC3T3-E1 cells, SHH up-regulated the expression of activin receptor IIB (ActR-IIB) and Smad1, which in turn enhanced BMP-responsive reporter activities in these cells. The combined stimulation with BMP-4 and SHH of MC3T3-E1 cells cooperatively induced the expression of osteoblastic markers, including alkaline phosphatase, bone sialoprotein, collagen type II α1, and osteocalcin. When MC3T3-E1 cells and LNCaP cells were co-cultured, the osteoblastic differentiation of MC3T3-E1 cells, which was induced by BMP-4, was accelerated by SHH from LNCaP cells. Furthermore, LNCaP cells and BMP-4 cooperatively induced the production of growth factors, including fibroblast growth factor (FGF)-2 and epidermal growth factor (EGF) in MC3T3-E1 cells, and these may promote the proliferation of LNCaP cells. Taken together, our findings suggest that BMPs provide favorable circumstances for the survival of prostate cancer cells and the differentiation of bone stromal cells in the bone microenvironment, possibly leading to the osteoblastic metastasis of prostate cancer.

BMPs and their clinical potentials

Bone morphogenetic protein (BMP) signaling in diseases is the subject of an overwhelming array of studies. BMPs are excellent targets for treatment of various clinical disorders. Several BMPs have already been shown to be clinically beneficial in the treatment of a variety of conditions, including BMP-2 and BMP-7 that have been approved for clinical application in nonunion bone fractures and spinal fusions. With the use of BMPs increasingly accepted in spinal fusion surgeries, other therapeutic approaches targeting BMP signaling are emerging beyond applications to skeletal disorders. These approaches can further utilize next-generation therapeutic tools such as engineered BMPs and ex vivo- conditioned cell therapies. In this review, we focused to provide insights into such clinical potentials of BMPs in metabolic and vascular diseases, and in cancer. [BMB reports 2011; 44(10): 619-634].

Preclinical orthotopic and intracardiac injection models of human breast cancer metastasis to bone and their use in drug discovery

Breast cancer is the most common malignancy in women, with the development of distant metastases rendering the condition incurable. Relatively little is known about the factors governing the progression from primary tumor to metastasis, in part because of the difficulty in modeling what is a complex series of events. Detailed in this unit are descriptions of two murine models of breast cancer metastasis to bone that can be used to screen the effectiveness of new chemical entities on this disease process.

Unique angiogenic and vasculogenic properties of renal cell carcinoma in a xenograft model of bone metastasis are associated with high levels of vegf-a and decreased ang-1 expression

Management of various tumor metastases to bone has dramatically improved, but this is not so for renal cell carcinoma (RCC), which is a difficult surgical problem due to its great vascularity. Furthermore, the unique mechanisms that mediate RCC vasculogenesis in bone remain unknown. To understand this process we developed a xenograft model that recapitulates highly vascular RCC versus less vascular tumors that metastasize to bone. Human tumor cell lines of RCC (786-O), prostate cancer (PC3), lung cancer (A549), breast cancer (MDA-MB231), and melanoma (A375) were transduced with firefly luciferase (Luc), injected into the tibiae of nude mice, and differences in growth, osteolysis, and vascularity were assessed by longitudinal bioluminescent imaging, micro-CT for measurement of calcified tissues and vascularity and histology. The results showed that while RCC-Luc has reduced growth and osteolytic potential versus the other tumor lines, it displayed a significant increase in vascular volume (p < 0.05). This expansion was due to 3- and 5-fold increases in small and large vessel numbers respectively. In vitro gene expression profiling revealed that RCC-Luc expresses significantly (p < 0.05) more vegf-a (10-fold) and 20- to 30-fold less ang-1 versus the other lines. These data demonstrate the utility of this model to study the unique vasculogenic properties of RCC bone metastases.

Disseminated prostate cancer cells can instruct hematopoietic stem and progenitor cells to regulate bone phenotype

Prostate cancer metastases and hematopoietic stem cells (HSC) frequently home to the bone marrow, where they compete to occupy the same HSC niche. We have also shown that under conditions of hematopoietic stress, HSCs secrete the bone morphogenetic proteins (BMP)-2 and BMP-6 that drives osteoblastic differentiation from mesenchymal precursors. As it is not known, we examined whether metastatic prostate cancer cells can alter regulation of normal bone formation by HSCs and hematopoietic progenitor cells (HPC). HSC/HPCs isolated from mice bearing nonmetastatic and metastatic tumor cells were isolated and their ability to influence osteoblastic and osteoclastic differentiation was evaluated. When the animals were inoculated with the LNCaP C4-2B cell line, which produces mixed osteoblastic and osteolytic lesions in bone, HPCs, but not HSCs, were able to induced stromal cells to differentiate down an osteoblastic phenotype. Part of the mechanism responsible for this activity was the production of BMP-2. On the other hand, when the animals were implanted with PC3 cells that exhibits predominantly osteolytic lesions in bone, HSCs derived from these animals were capable of directly differentiating into tartrate-resistant acid phosphatase-positive osteoclasts through an interleukin-6-mediated pathway. These studies for the first time identify HSC/HPCs as novel targets for future therapy involved in the bone abnormalities of prostate cancer.

Effect of bone morphogenetic protein-2 on proliferation and apoptosis of gastric cancer cells

OBJECTIVE

To investigate the effects of bone morphogenetic protein-2 (BMP-2) on the proliferation, differentiation and apoptosis of normal human gastric mucosal cells and gastric cancer cells.

METHODS

Poorly differentiated gastric cancer BGC823 cells, moderately differentiated gastric cancer cells and normal human gastric mucosal epithelial GES-1 cells were independently treated with recombinant human BMP-2 or its inhibitor Noggin. MTT assay was performed to detect the proliferation, flow cytometry done to measure the cell cycle and apoptosis and immunohistochemistry carried out to determine the expression of cyclin-dependent kinase 4 (CDK4).

RESULTS

BMP-2 exerted inhibitory effect on the growth of all types of cells and the inhibition become more evident with the increase of BMP-2 dose. After treatment with 200 ng/ml BMP-2, cancer cells arrested in G1 phase and those in S phase reduced. Gastric cancer cells had higher CDK4 expression than GES-1 cells. BMP-2 decreased CDK-4 expression in cancer cells but had no influence in GES-1 cells. Noggin conferred promotive effect on the growth of 3 types of cells. In 2 types of cancer cells, treatment with 2000 ng/ml Noggin significantly increased the proportion of cells in S phase but reduced that in G1 phase. However, Noggin did not affect the cell cycle of GES-1 cells. The CDK4 expression was markedly increased in 2 types of cancer cells but that of GES-1 remained unchanged after treatment with 2000 ng/ml Noggin.

CONCLUSIONS

BMP-2 may inhibit the proliferation of both normal and malignant gastric epithelial cells, down-regulate CDK4 expression in gastric cancer cells and arrest gastric cancer cells in G1-phase in cell cycle. Through antagonizing BMP-2, Noggin, may accelerate the proliferation of gastric cancer cells. Thus, the abnormality of BMP signaling pathway may play an important role in the pathogenesis of gastric cancer.

Bone morphogenetic protein 4 (BMP4) is required for migration and invasion of breast cancer

Bone-morphogenetic proteins (BMPs) play an important role in development and many cellular processes. However, their functional role in the development and progression of breast cancer is not clearly understood. In the present study, we performed a systematic expression analysis of the 14 types of BMPs in 10 human breast cancer cell lines. We found that bone morphogenetic protein 4 (BMP4) was one of the most frequently expressed BMPs. Furthermore, the expression level of BMP4 was maybe correlated with the metastatic potential of the cancer lines. Accordingly, overexpression of BMP4 in the breast cancer cell lines MCF-7 and MBA-MD-231 promoted the migration and invasion phenotypes of the cancer cells, whereas RNAi-mediated knockdown of BMP4 expression inhibited the migration and invasion activities of the cancer cells. To identify the important factors that may mediate the BMP4 functions in breast cancer cells, we analyzed a panel of cancer-related genes, and found that the expression of matrix metalloproteinase-1 (MMP-1) and C-X-C chemokine receptor type 4 (CXCR4) sharply increased at both the mRNA and protein levels in the breast cancer cells overexpressing BMP4. Interestingly, when breast cancer cells MDA-MB-231 or MCF-7 were co-cultured with the osteoblast-like cells MG63 to mimic a bone metastasis microenvironment, BMP4 did not exhibit any significant effect on the expression of OPG or RANKL, two important factors in bone remodeling. BMPs antagonists, Noggin, parallel inhibited breast cancer cell migration and invasion and induced bone remodeling. Taken together, our results strongly suggest that BMP4 may promote the migration and invasion of breast cancer cells, at least in part by up-regulating the expressions of MMP-1 and CXCR4. It is conceivable that novel therapeutics for breast cancer may be developed by targeting BMP4 signaling pathway and/or its important downstream mediators in breast cancer cells.

Effects of the bone morphogenetic protein binding protein spp24 (secreted phosphoprotein 24 kD) on the growth of human lung cancer cells

Bone morphogenetic proteins (BMPs) and transforming growth factor-beta (TGF-β) contribute to the growth of some skeletal metastases through autocrine stimulation. Secreted phosphoprotein 24 kDa (spp24) has been shown to bind to both BMP-2 and TGF-β and to markedly inhibit the osteogenic properties of rhBMP-2. We hypothesized that the addition of spp24 would sequester autocrine growth factors (especially BMP-2) and reduce tumor growth in a system (A549 human non-small cell lung cancer cell line) where autocrine stimulation by BMP-2 is known to be important. A549 cells were injected into two sites (subcutaneous and intraosseus) in SCID mice with and without the co-injection of BMP-2 and spp24. Tumor growth after 8 weeks was assessed through gross examination, radiological imaging, and histological analysis. Spp24 attenuated the tumor growth enhancing effects of rhBMP-2 and reduced the tumor growth when added to tumor cells that were not treated with BMP-2. We conclude that spp24 can reduce A549 cell tumor growth in both soft tissue and intraosseus environments. We hypothesize that the mechanism for this inhibition is interruption of autocrine stimulation through the sequestration of BMP-2. Spp24 can be developed into a therapeutic agent that can be employed in clinical situations where the inhibitions of BMPs and related proteins is advantageous.

Human ovarian carcinoma–associated mesenchymal stem cells regulate cancer stem cells and tumorigenesis via altered BMP production

Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment; however, controversy exists regarding their role in solid tumors. In this study, we identified and confirmed the presence of carcinoma-associated MSCs (CA-MSCs) in the majority of human ovarian tumor samples that we analyzed. These CA-MSCs had a normal morphologic appearance, a normal karyotype, and were nontumorigenic. CA-MSCs were multipotent with capacity for differentiating into adipose, cartilage, and bone. When combined with tumor cells in vivo, CA-MSCs promoted tumor growth more effectively than did control MSCs. In vitro and in vivo studies suggested that CA-MSCs promoted tumor growth by increasing the number of cancer stem cells. Although CA-MSCs expressed traditional MSCs markers, they had an expression profile distinct from that of MSCs from healthy individuals, including increased expression of BMP2, BMP4, and BMP6. Importantly, BMP2 treatment in vitro mimicked the effects of CA-MSCs on cancer stem cells, while inhibiting BMP signaling in vitro and in vivo partly abrogated MSC-promoted tumor growth. Taken together, our data suggest that MSCs in the ovarian tumor microenvironment have an expression profile that promotes tumorigenesis and that BMP inhibition may be an effective therapeutic approach for ovarian cancer.

Unravelling the complexity of metastasis - molecular understanding and targeted therapies

Despite recognizing the devastating consequences of metastasis, we are not yet able to effectively treat cancer that has spread to vital organs. The inherent complexity of genomic alterations in late-stage cancers, coupled with numerous heterotypic interactions that occur between tumour and stromal cells, represent fundamental challenges in our quest to understand and control metastatic disease. The incorporation of genomic and other systems level approaches, as well as technological breakthroughs in imaging and animal modelling, have galvanized the effort to overcome gaps in our understanding of metastasis. Future research carries with it the potential to translate the wealth of new knowledge and conceptual advances into effective targeted therapies.

Bone morphogenetic protein -4 and -5 in pancreatic cancer--novel bidirectional players

Bone morphogenetic proteins (BMPs) are multifunctional signaling molecules that have gained increasing interest in cancer research. To obtain a systematic view on BMP signaling in pancreatic cancer we first determined the mRNA expression levels of seven BMP ligands (BMP2-BMP8) and six BMP specific receptors in pancreatic cancer cell lines and normal pancreatic tissue. BMP receptor expression was seen in all cancer and normal samples. Low expression levels of BMP5 and BMP8 were detected in cancer cells compared to the normal samples, whereas BMP4 expression was elevated in 25% of the cases. The impact of BMP4 and BMP5 signaling on cell phenotype was then evaluated in five pancreatic cancer cell lines. Both ligands suppressed the growth of three cell lines (up to 79% decrease in BMP4-treated PANC-1 cells), mainly due to cell cycle changes. BMP4 and BMP5 concurrently increased cell migration and invasion (maximally a 10.8-fold increase in invaded BMP4-treated PANC-1 cells). The phenotypic changes were typically associated with the activation of the canonical SMAD pathway, although such activation was not observed in the PANC-1 cells. Taken together, BMP4 and BMP5 simultaneously inhibit the growth and promote migration and invasion of the same pancreatic cells and thus exhibit a biphasic role with both detrimental and beneficial functions in pancreatic cancer progression.

BMP4 promotes prostate tumor growth in bone through osteogenesis

Induction of new bone formation is frequently seen in the bone lesions from prostate cancer. However, whether osteogenesis is necessary for prostate tumor growth in bone is unknown. Recently, 2 xenografts, MDA-PCa-118b and MDA-PCa-133, were generated from prostate cancer bone metastases. When implanted subcutaneously in severe combined immunodeficient (SCID) mice, MDA-PCa-118b induced strong ectopic bone formation while MDA-PCa-133 did not. To identify the factors that are involved in bone formation, we compared the expression of secreted factors (secretome) from MDA-PCa-118b and MDA-PCa-133 by cytokine array. We found that the osteogenic MDA-PCa-118b xenograft expressed higher levels of bone morphogenetic protein BMP4 and several cytokines including interleukin-8, growth-related protein (GRO), and CCL2. We showed that BMP4 secreted from MDA-PCa-118b contributed to about a third of the osteogenic differentiation seen in MDA-PCa-118b tumors. The conditioned media from MDA-PCa-118b induced a higher level of osteoblast differentiation, which was significantly reduced by treatment with BMP4 neutralizing antibody or the small molecule BMP receptor 1 inhibitor LDN-193189. BMP4 did not elicit an autocrine effect on MDA-PCa-118b, which expressed low to undetectable levels of BMP receptors. Treatment of SCID mice bearing MDA-PCa-118b tumors with LDN-193189 significantly reduced tumor growth. Thus, these studies support a role of BMP4-mediated osteogenesis in the progression of prostate cancer in bone.

Regulation of phosphatase homologue of tensin protein expression by bone morphogenetic proteins in prostate epithelial cells

BACKGROUND

Phosphatase homologue of tensin (PTEN) is the most commonly mutated gene in prostate cancer. Bone morphogenetic proteins (BMPs) are known to promote differentiation and inhibit proliferation. Previously published reports from other organ systems led us to investigate a mechanistic relationship between PTEN and BMP signaling in prostate epithelial cells.

METHODS

We analyzed growth rate and PTEN expression in E6, BPH-1, and C4-2B prostate epithelial cells treated with BMP-4. We also treated doxacyclin-inducible PTEN-C4-2B cells with BMP-4 and doxacyclin to determine the effect of BMP on growth and PTEN expression in conditions of increasing PTEN expression. We determined the dependency of BMP-mediated growth inhibition via siRNA knockdown of PTEN expression and BMP treatment. We determined PTEN protein stability by determining the effect of BMP-4 on PTEN protein at time points after treatment with cyclohexamide, a translation inhibitor.

RESULTS

We found that BMP-4 induces PTEN in E6 and BPH-1 cells and reduces proliferation. Knockdown of PTEN attenuated the growth-inhibiting effects of BMP-4 in these cells. BMP-4 had no effect in PTEN-negative C4-2B cells, but doxacyclin-driven PTEN C4-2B cells responded to BMP-4 with enhanced PTEN and growth inhibition. BMP-4 also increased PTEN protein stability.

CONCLUSIONS

BMP signaling induces PTEN expression and sustains PTEN protein expression resulting in inhibition of prostate epithelial cell growth. These data are the first to identify a mechanistic linkage between BMP signaling and PTEN in the prostate, both of which are independently identified as tumor suppressors and suggest possible coordinate dysregulation in prostate cancer.

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 (10mg/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, (18)F-Fluorodeoxyglucose and (18)F-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.

The role of the BMP signaling antagonist noggin in the development of prostate cancer osteolytic bone metastasis

Members of the BMP and Wnt protein families play a relevant role in physiologic and pathologic bone turnover. Extracellular antagonists are crucial for the modulation of their activity. Lack of expression of the BMP antagonist noggin by osteoinductive, carcinoma-derived cell lines is a determinant of the osteoblast response induced by their bone metastases. In contrast, osteolytic, carcinoma-derived cell lines express noggin constitutively. We hypothesized that cancer cell-derived noggin may contribute to the pathogenesis of osteolytic bone metastasis of solid cancers by repressing bone formation. Intra-osseous xenografts of PC-3 prostate cancer cells induced osteolytic lesions characterized not only by enhanced osteoclast-mediated bone resorption, but also by decreased osteoblast-mediated bone formation. Therefore, in this model, uncoupling of the bone remodeling process contributes to osteolysis. Bone formation was preserved in the osteolytic lesions induced by noggin-silenced PC-3 cells, suggesting that cancer cell-derived noggin interferes with physiologic bone coupling. Furthermore, intra-osseous tumor growth of noggin-silenced PC-3 cells was limited, most probably as a result of the persisting osteoblast activity. This investigation provides new evidence for a model of osteolytic bone metastasis where constitutive secretion of noggin by cancer cells mediates inhibition of bone formation, thereby preventing repair of osteolytic lesions generated by an excess of osteoclast-mediated bone resorption. Therefore, noggin suppression may be a novel strategy for the treatment of osteolytic bone metastases.

Dysregulation of developmental pathways in bone metastasis

It is well-known that pathways normally functioning during embryonic development are dysregulated in cancer. Experimental and clinical studies have established strong connections between aberrant developmental pathways and transformation, as well as other early stage events of cancer progression. There is now emerging evidence that also indicates the contribution of developmental pathways to the pathogenesis of distant metastasis, including bone metastasis. In particular, the Wnt, BMP, and Hedgehog signaling pathways have all been implicated in the development of bone metastasis. These developmental pathways participate in the regulation of cell-autonomous functions in tumor cells as well as tumor-stromal interactions in the bone microenvironment, eventually promoting the formation of osteolytic or osteoblastic bone metastasis.

Autocrine TGF-β protects breast cancer cells from apoptosis through reduction of BH3-only protein, Bim

Cancer cells undergo multi-step processes in obtaining the ability to metastasize, and are constantly exposed to signals that induce apoptosis. Acquisition of anti-apoptotic properties by cancer cells is important for metastasis, and recent studies suggest that transforming growth factor (TGF)-β promotes the survival of certain types of cancer cells. Here, we found that in highly metastatic breast cancer cells, JygMC(A), JygMC(B) and 4T1, TGF-β ligands were produced in autocrine fashion. Pharmacological inhibition of endogenous TGF-β signalling by a TGF-β type I receptor kinase inhibitor in serum-free conditions increased the expression of BH3-only protein, Bim (also known as Bcl2-like 11) in JygMC(A) and JygMC(B) cells, and caused apoptotic cell death. We also found that induction of Bim by TGF-β was not observed in Foxc1 knocked-down cancer cells. These findings suggest that TGF-β plays a crucial role in the regulation of survival of certain types of cancer cells through the TGF-β-Foxc1-Bim pathway, and that specific inhibitors of TGF-β signalling might be useful as apoptosis inducers in breast cancer cells.

Development of an in vitro model to study the impact of BMP-2 on metastasis to bone

Prostate cancer cases and deaths have increased for years, yet the mechanisms involved in prostate cancer metastasis to bone remain poorly understood. To address this need, an effective and relevant in vitro model for the study of prostate cancer bone metastases would be useful. Therefore, a 3D in vitro tissue system was established using prostate cancer cells (PC3), suitable culture conditions and a 3D silk scaffold biomaterial to provide mechanically robust and slow degrading matrices to support the tissues for extended time frames. The role of BMP-2 on the progression of prostate cancer was investigated using this 3D tissue system. The results suggest that BMP-2 stimulates the migration of PC3 cells, suggesting insight into mechanisms involved in this critical step in the disease. The data support the conclusion that this in vitro system mimics aspects of prostate cancer metastasis in the presence of BMP-2, thus the system can be utilized as a starting point as an in vitro model for further studies of prostate cancer development and metastasis, as well as in the screening of new therapeutic treatments.

Emerging biomarkers in breast cancer care

Currently, decision-making for breast cancer treatment in the clinical setting is mainly based on clinical data, histomorphological features of the tumor tissue and a few cancer biomarkers such as steroid hormone receptor status (estrogen and progesterone receptors) and oncoprotein HER2 status. Although various therapeutic options were introduced into the clinic in recent decades, with the objective of improving surgery, radiotherapy, biochemotherapy and chemotherapy, varying response of individual patients to certain types of therapy and therapy resistance is still a challenge in breast cancer care. Therefore, since breast cancer treatment should be based on individual features of the patient and her tumor, tailored therapy should be an option by integrating cancer biomarkers to define patients at risk and to reliably predict their course of the disease and/or response to cancer therapy. Recently, candidate-marker approaches and genome-wide transcriptomic and epigenetic screening of different breast cancer tissues and bodily fluids resulted in new promising biomarker panels, allowing breast cancer prognosis, prediction of therapy response and monitoring of therapy efficacy. These biomarkers are now subject of validation in prospective clinical trials.

Expression of bone morphogenetic protein-2 and its receptors in epithelial ovarian cancer and their influence on the prognosis of ovarian cancer patients

BACKGROUND

To determine the expression of bone morphogenetic protein-2 (BMP-2) and its receptors BMPRIA, BMPRIB, and BMPRII in epithelial ovarian cancer (EOC) and to analyze their influence on the prognosis of ovarian cancer patients.

METHODS

Semi-quantitative RT-PCR and western blot were applied to detect the expression of BMP-2 and its receptors BMPRIA, BMPRIB, and BMPRII in EOC, benign ovarian tumors, and normal ovarian tissue at the mRNA and protein levels. Immunohistochemistry was used to determine the expression of BMP-2 and its receptors in 100 patients with EOC to analyze their influence on the five-year survival rate and survival time of ovarian cancer patients.

RESULTS

(1) The mRNA and protein expression levels of BMP-2, BMPRIB, and BMPRII in ovarian cancer tissue were remarkably lower than those in benign ovarian tumors and normal ovarian tissue, while no significant differences in BMPRIA expression level was found among the three kinds of tissues. (2) The five-year survival rate and the average survival time after surgery of EOC patients with positive expression of BMP-2, BMPRIB, and BMPRII were remarkably higher than those of patients with negative expression of BMP-2, BMPRIB, and BMPRII. BMPRIA expression was not associated with the five-year survival rate or with the average survival time of ovarian cancer patients.

CONCLUSIONS

BMP-2, BMPRIB, and BMPRII exhibited low expression in EOC tissue, and variation or loss of expression may indicate poor prognosis for ovarian cancer patients.

The chemopreventive retinoid 4HPR impairs prostate cancer cell migration and invasion by interfering with FAK/AKT/GSK3beta pathway and beta-catenin stability

Background

Prostate cancer shows an extremely slow progression, appearing in its metastatic, hormone refractory phenotype mostly in elderly men. The chemopreventive targeting of this tumor could accordingly delay its malignancy over life expectancy. The cancer chemopreventive retinoid N-(4 hydroxyphenyl)retinamide (4HPR) has already been shown to restrain prostate cancer growth in vitro and in vivo, though its mechanisms of action are only partially explained.

Results

We found that 4HPR impairs DU145 and PC3 prostate cancer cells migration and invasion by down-regulating FAK and AKT activation and by enhancing β-catenin degradation, causing the downregulation of target genes like cyclin D1, survivin and VEGF. This non-migratory phenotype was similarly produced in both cell lines by stable silencing of β-catenin. 4HPR was able to decrease AKT phosphorylation also when powerfully upregulated by IGF-1 and, consequently, to impair IGF-1-stimulated cell motility. Conversely, the expression of constitutively active AKT (myr-AKT) overcame the effects of 4HPR and β-catenin-silencing on cell migration. In addition, we found that BMP-2, a 4HPR target with antiangiogenic activity, decreased prostate cancer cell proliferation, migration and invasion by down-regulating the pathway described involving AKT phosphorylation, β-catenin stability and cyclin D1 expression.

Conclusion

These data point to 4HPR as a negative regulator of AKT phosphorylation, effectively targeting the β-catenin pathway and inducing a relatively benign phenotype in prostate cancer cells, limiting neoangiogenesis and cell invasion.

SKI-606 (Bosutinib) blocks prostate cancer invasion, growth, and metastasis in vitro and in vivo through regulation of genes involved in cancer growth and skeletal metastasis

In the current study, we have examined the efficacy of a Src/Abl kinase inhibitor SKI-606 (Bosutinib) for its effect on prostate cancer growth and skeletal metastasis. Treatment of highly invasive human prostate cancer cells PC-3 and DU-145 with different doses of SKI-606 decreased Src activation, cell proliferation, migration, and invasion as determined by Matrigel Boyden chamber invasion assay. For in vivo studies, PC-3 cells were inoculated through s.c. or i.t. route into male BALB/c nu/nu or Fox Chase severe combined immunodeficient mice, respectively. Experimental animals treated with SKI-606 developed tumors of a significantly smaller volume and a significant decrease (50%) in experimental skeletal lesion area. A marked increase (32%) in bone volume to tumor volume ratio was also seen by micro-computed tomography analysis of tibias from control and experimental groups of animals. Western blot analysis showed the ability of SKI-606 to significantly decrease the phosphorylation of signaling molecules (AKT, mitogen-activated protein kinase, focal adhesion kinase) and the expression of tumor progression-associated genes uPAR, MMP-2, MMP-9, N-cadherin, fibronectin, BMP-2 (bone morphogenetic protein 2), BMP-6 (bone morphogenetic protein 6), IL-8 (interleukin 8), and TGF-beta (transforming growth factor beta) in prostate cancer cells. SKI-606 is currently in clinical trials for breast cancer and chronic myelogenous leukemia. Results from these studies provide convincing evidence for evaluating its efficacy in prostate cancer patients.

Bone morphogenetic protein 7 is expressed in prostate cancer metastases and its effects on prostate tumor cells depend on cell phenotype and the tumor microenvironment

Bone morphogenetic protein (BMP) signaling is important in prostate development and prostate cancer (PCa) progression. However, because of the multiple effects of different BMPs, no final conclusions have been made as to the role of BMPs in PCa. In our studies, we have focused on BMP-7 because it is involved in prostate morphogenesis, and its expression is regulated by androgens. The objective of our study was to determine BMP-7 expression in PCa metastases and investigate the effects of BMP-7 on PCa cells. Our results show that BMP-7 is expressed in metastatic PCa and its levels are increased in castration-resistant PCa versus androgen-dependent PCa, whereas the expression of BMP-7 is decreased in primary PCa versus normal prostate. Our in vitro results show that BMP-7 inhibits proliferation of androgen-sensitive LNCaP cells, stimulates androgen receptor signaling, increases the expression of differentiation-associated genes, and decreases the levels of some wingless-regulated transcripts. Interestingly, these effects were not detected in C4-2 castration-resistant PCa cells. In vivo expression of BMP-7 in castration-resistant C4-2 cells did not alter proliferation when these cells were grown subcutaneously, but their growth was inhibited in the bone environment. In summary, our results show that BMP-7 is expressed at the highest level in advanced castration-resistant PCa cells and that the inhibitory effects of BMP-7 are dependent on the differentiation status of PCa cells and the tumor microenvironment. Further studies are needed to identify changes in BMP-7 signaling that lead to the loss of its control of proliferation during PCa progression.

A role for NRAGE in NF-kappaB activation through the non-canonical BMP pathway

Background

Previous studies have linked neurotrophin receptor-interacting MAGE protein to the bone morphogenic protein signaling pathway and its effect on p38 mediated apoptosis of neural progenitor cells via the XIAP-Tak1-Tab1 complex. Its effect on NF-κB has yet to be explored.

Results

Herein we report that NRAGE, via the same XIAP-Tak1-Tab1 complex, is required for the phosphorylation of IKK -α/β and subsequent transcriptional activation of the p65 subunit of NF-κB. Ablation of endogenous NRAGE by siRNA inhibited NF-κB pathway activation, while ablation of Tak1 and Tab1 by morpholino inhibited overexpression of NRAGE from activating NF-κB. Finally, cytokine profiling of an NRAGE over-expressing stable line revealed the expression of macrophage migration inhibitory factor.

Conclusion

Modulation of NRAGE expression revealed novel roles in regulating NF-κB activity in the non-canonical bone morphogenic protein signaling pathway. The expression of macrophage migration inhibitory factor by bone morphogenic protein -4 reveals novel crosstalk between an immune cytokine and a developmental pathway.

Bone morphogenetic protein 4 mediates myocardial ischemic injury through JNK-dependent signaling pathway

Bone morphogenetic protein (BMP) signaling regulates embryonic development of many organ systems and defective BMP signaling has been implicated in adult disorders of many of these systems. However, its relevance in cardiac disease has not been reported. Here we demonstrate for the first time that Bmp4 activity promotes cellular apoptosis following ischemia-reperfusion (I/R) injury induced myocardial infarction (MI). Bmp4 heterozygous null mice (Bmp4(+/)(-)) demonstrated reduced infarct size, less myocardial apoptosis and down-regulation of pro-apoptotic proteins relative to wild-type mice following I/R injury. This was associated with reduction in I/R induced BMP4 levels in the left ventricular infarcted region. Furthermore, treatment of neonatal cardiomyocytes with BMP4 resulted in time and dose-dependent increase in cellular apoptosis and activation of the JNK MAP kinase pathway. In contrast, while JNK activation was significantly attenuated in Bmp4(+/)(-) mice and following Smad1 inhibition in myocytes, inhibition of JNK with a specific inhibitory peptide, TAT-JBD(20,) blocked BMP4 induced apoptosis. In vivo treatment of mice with Noggin, an endogenous extracellular BMP antagonist, or dorsomorphin, a small molecule inhibitor of BMP signaling, reduced infarct size, and inhibited pro-apoptotic signaling accompanied by an inhibition of Smad1 phosphorylation and JNK activation. These studies identify a novel role for Bmp4 in the pathogenesis of myocardial infarction and illustrate the use of a small molecule inhibitor of BMP signaling for treatment of acute I/R injury.

Effects of bone morphogenetic protein-2 on proliferation and angiogenesis in oral squamous cell carcinoma

Experimental data and limited patient experience suggest that rhBMP-2 can be used to regenerate bone in acquired segmental defects of the mandible. Most of these defects are caused by resection of oral squamous cell carcinoma (OSCC) and the biologic effects of rhBMP-2 on these carcinoma cells are unknown. The objective of this study was to determine whether rhBMP-2 produces adverse effects on proliferation and angiogenesis in OSCC, two biologic processes critical to tumor formation. In vitro studies included treating OSCC cells with rhBMP-2 or an adenoviral vector containing the cDNA for BMP-2. In vivo studies involved co-transplantation of OSCC cells with bone marrow stromal cells genetically modified to over express BMP-2, to mimic a clinically relevant scenario for regenerating bone using cell-based therapy in a wound containing microscopic residual disease. Proliferation, as measured by a MTT assay in vitro and tumor growth in vivo was not affected by treatment with BMP-2. Angiogenesis, measured by secretion of the proangiogenic molecules VEGF and IL-8 in vitro and microvessel density in vivo, was not affected. Exposure of OSCC cells to BMP-2 does not stimulate proliferation or angiogenesis. Further studies are needed before using rhBMP-2 for bone tissue engineering in oral cancer-related defects.

Prostate cancer cells modulate osteoblast mineralisation and osteoclast differentiation through Id-1

Background:

Id-1 is overexpressed in and correlated with metastatic potential of prostate cancer. The role of Id-1 in this metastatic process was further analysed.

Methods:

Conditioned media from prostate cancer cells, expressing various levels of Id-1, were used to stimulate pre-osteoclast differentiation and osteoblast mineralisation. Downstream effectors of Id-1 were identified. Expressions of Id-1 and its downstream effectors in prostate cancers were studied using immunohistochemistry in a prostate cancer patient cohort (N=110).

Results:

We found that conditioned media from LNCaP prostate cancer cells overexpressing Id-1 had a higher ability to drive osteoclast differentiation and a lower ability to stimulate osteoblast mineralisation than control, whereas conditioned media from PC3 prostate cancer cells with Id-1 knockdown were less able to stimulate osteoclast differentiation. Id-1 was found to negatively regulate TNF-β and this correlation was confirmed in human prostate cancer specimens (P=0.03). Furthermore, addition of recombinant TNF-β to LNCaP Id-1 cell-derived media blocked the effect of Id-1 overexpression on osteoblast mineralisation.

Conclusion:

In prostate cancer cells, the ability of Id-1 to modulate bone cell differentiation favouring metastatic bone disease is partially mediated by TNF-β, and Id-1 could be a potential therapeutic target for prostate cancer to bone metastasis.

A single pretreatment by zoledronic acid converts metastases from osteolytic to osteoblastic in the rat

Bone metastases are severe complications of cancers associated with increased morbidity, pain, risk fracture, and reduced life span for patients. Bisphosphonates emerged as a relief treatment in bone metastases. A single dose of zoledronic acid (78 microg/kg) was injected into six Copenhagen rats 4 days before receiving an intraosseous inoculation of metastatic anaplastic tumor of lymph node and lung cell (MLL) prostate cancer cells. Rat femurs were analyzed for changes by microCT and histomorphometry; trabecular volume, trabecular characteristics, osteoid parameters, osteoblastic surfaces, and osteoclast number were measured. Values were compared to a group of SHAM animals, a group of SHAM animals having received zoledronic acid and animals inoculated with MLL cells. All rats were euthanized after 1 month. MLL cells induced osteolysis in the metaphysis with extension of the tumor to soft tissues through cortical perforations. Zoledronic acid induced a marked osteosclerosis in the primary spongiosa in both SHAM and rats inoculated with MLL. Osteosclerosis was obtained in the secondary spongiosa of MLL rats. The bisphosphonate preserved cortical integrity in all animals, and no extension to soft tissues was observed in most animals. The number of osteoclasts was elevated, indicating that there was no apoptosis of osteoclasts but they became inactive. Osteosclerosis was associated with increased osteoblastic surfaces. A single zoledronic acid injection turned osteolytic metastases into osteosclerotic and preserved cortical integrity.

Bone morphogenetic protein-2 levels are elevated in the patients with gastric cancer and correlate with disease progression

Bone morphogenetic protein-2 (BMP-2) was reported to enhance migration, invasion, and metastasis at the various types of cancer cells. The purpose of this study is to identify the role of BMP-2 in progression of gastric cancer. Forty-four patients with operable gastric cancer were enrolled. Also, twenty healthy volunteers were enrolled as control group. All patients received gastrectomy with D2 lymphadenectomy, and surgical staging was performed. Whole blood was obtained preoperatively in all patients, and serum BMP-2 levels were quantified by commercially available ELISA kit. Immunohistochemical stain for BMP-2 in all gastric cancer tissues was performed using tissue microarray. All patients showed increased serum BMP-2 levels compared with control group, when upper normal limit was defined as the mean of control serum level+2×standard deviation. The mean serum BMP-2 level of lymph node positive group was significantly elevated than that of lymph node-negative group (382.7 pg/ml, 95% CI 341.99-423.4 pg/ml vs 211.69 pg/ml, 95% CI 191.09-232.29 pg/ml, P<0.001). The serum BMP-2 was strongly correlated with the depth of invasion (T stage) and the extent of regional lymph node involvement (N stage) (r=0.662, P<0.001 and r=0.831, P<0.001, respectively). Moreover, the serum BMP-2 was correlated with the grade of tumor histology(r=0.421, P=0.008). Immunohistochemical stain showed the specific expression of BMP-2 in cancer cells compared with normal gastric mucosa. In conclusion, serum BMP-2 is associated with progression from early localized gastric cancer to locally advanced gastric cancer.

Enhanced osteoclastogenesis causes osteopenia in twisted gastrulation-deficient mice through increased BMP signaling

The uncoupling of osteoblastic and osteoclastic activity is central to disorders such as osteoporosis, osteolytic malignancies, and periodontitis. Numerous studies have shown explicit functions for bone morphogenetic proteins (BMPs) in skeletogenesis. Their signaling activity has been shown in various contexts to be regulated by extracellular proteins, including Twisted gastrulation (TWSG1). However, experimental paradigms determining the effects of BMP regulators on bone remodeling are limited. In this study, we assessed the role of TWSG1 in postnatal bone homeostasis. Twsg1-deficient (Twsg1(-/-)) mice developed osteopenia that could not be explained by defective osteoblast function, because mineral apposition rate and differentiation markers were not significantly different compared with wildtype (WT) mice. Instead, we discovered a striking enhancement of osteoclastogenesis in Twsg1(-/-) mice, leading to increased bone resorption with resultant osteopenia. Enhanced osteoclastogenesis in Twsg1(-/-) mice was caused by increased cell fusion, differentiation, and function of osteoclasts. Furthermore, RANKL-mediated osteoclastogenesis and phosphorylated Smad1/5/8 levels were enhanced when WT osteoclasts were treated with recombinant BMP2, suggesting direct regulation of osteoclast differentiation by BMPs. Increase in detectable levels of phosphorylated Smad 1/5/8 was noted in osteoclasts from Twsg1(-/-) mice compared with WT mice. Furthermore, the enhanced osteoclastogenesis in Twsg1(-/-) mice was reversed in vitro in a dose-dependent manner with exposure to Noggin, a BMP antagonist, strongly suggesting that the enhanced osteoclastogenesis in Twsg1 mutants is attributable to increased BMP signaling. Thus, we present a novel and previously uncharacterized role for TWSG1 in inhibiting osteoclastogenesis through regulation of BMP activity.

BMP2 accelerates the motility and invasiveness of gastric cancer cells via activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway

Up-regulation of bone morphogenetic proteins (BMPs) and their receptors by tumor is an important hallmark in cancer progression, as it contributes through autocrine and paracrine mechanisms to tumor development, invasion, and metastasis. Generally, increased motility and invasion are positively correlated with the epithelial-mesenchymal transition (EMT). The purpose of the present study was to determine whether BMP-2 signaling to induce gastric cancer cells to undergo EMT-mediated invasion might pass through the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Herein we showed that gastric cancer cell lines express all the components of BMP-2 signaling, albeit to different extents. Moreover, an increased concentration of BMP-2 strongly enhanced motility and invasiveness in gastric cancer cells, whereas no increase was observed in cells treated with either Noggin (a BMP-2 inhibitor) or BMP-2 blocking antibodies. The stimulation of BMP-2 in gastric cancer cells induces a full EMT characterized by Snail induction, E-cadherin delocalization and down-regulation, and up-regulation of mesenchymal and invasiveness markers. Furthermore, blockade of BMP-2 signaling by Noggin or BMP-2 blocking antibodies also restored these changes in EMT markers. In addition, phosphorylation of Akt was also enhanced by treatment with BMP-2, but not Noggin or BMP-2 blocking antibodies. Pretreatment of gastric cancer cells with PI-3 kinase/Akt kinase inhibitor (kinase-dead Akt [DN-Akt], Akt siRNA, or LY294002) significantly inhibited BMP-2-induced EMT and invasiveness. Overall, our studies suggest that BMP-2 promotes motility and invasion of gastric cancer cells by activating PI-3 kinase/Akt and that targeting of this signaling pathway may provide therapeutic opportunities in preventing metastasis mediated by BMP-2.

Applications of small molecule BMP inhibitors in physiology and disease

Bone morphogenetic proteins (BMPs) provide critical signals for determining cell fate, specifying gastrulation, embryonic patterning, organogenesis, and the remodeling of diverse tissues. Recent work has suggested that in addition to coordinating pivotal events in development, BMPs may also regulate certain homeostatic physiological processes independently of effects on cell growth or differentiation. We recently described the identification of dorsomorphin, a small molecule inhibitor of BMP type I receptors which inhibits BMP signaling in preference to TGF-beta, Activin, and other ligands of the TGF-beta family. We describe a number of strategies using dorsomorphin and its derivatives as probes to assess the physiologic roles of BMP signaling. We also discuss several potential applications for small molecule BMP inhibitors, including stem cell manipulation, and the therapeutic modification of bone remodeling, heterotopic ossification, and iron homeostasis.

Independent and cooperative roles of tumor necrosis factor-alpha, nuclear factor-kappaB, and bone morphogenetic protein-2 in regulation of metastasis and osteomimicry of prostate cancer cells and differentiation and mineralization of MC3T3-E1 osteoblast-like cells

The molecular mechanisms involved in prostate cancer (PC) metastasis and bone remodeling are poorly understood. We recently reported that phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) mediates transcriptional regulation and activation of bone morphogenetic protein (BMP)-2 signaling by nuclear factor (NF)-kappaB in bone metastatic prostate cancer cells. In the present study, we demonstrate that NF-kappaB, whether activated by recombinant human tumor necrosis factor (TNF)-alpha or by ectopic expression of the p65 subunit, is involved in extracellular matrix adhesion and invasion of osteotropic PC-3 and C4-2B, but not LNCaP, cells. The enhanced metastatic potential was associated with transcriptional upregulation of osteopontin, osteocalcin, and collagen IA1 in osteotropic PC cells, suggesting their role in osteomimicry of PC cells. Unlike BMP-4, BMP-2 protein enhanced the invasive properties of C4-2B cells, but not in LNCaP cells. Also, this effect was nullified by Noggin. In addition, BMP-2 mediates TNF-alpha-induced invasion of C4-2B cells in a NF-kappaB-dependent fashion. TNF-alpha or conditioned media (CM) of TNF-alpha-stimulated C4-2B cells upregulated BMP-2 and BMP-dependent Smad transcripts and inhibited receptor activator of NF-kappaB ligand transcripts in RAW 264.7 preosteoclast cells, respectively, implying that this factor may contribute to suppression of osteoclastogenesis via direct and paracrine mechanisms. In contrast, CM of TNF-alpha-stimulate or BMP2-stimulated C4-2B cells induced in vitro mineralization of MC3T3-E1 osteoblast cells in a BMP-2-dependent and NF-kappaB-dependent manner, respectively. Taken together, the results suggest that mutual interactions between these factors may be pivotal not only in enhancing the osteomimicry and metastatic potential of PC cells, but also in bone remodeling and in shifting the balance from osteoclastogenesis towards osteoblastogenesis.

Expression of bone morphogenetic protein 2 and 6 and clinical significance in liver carcinoma

AIM: To investigate the expression of bone morphogenetic protein 2 and 6 (BMP-2, 6) mRNA in human liver cancer, and to explore its relationship with biologic action in liver cancer.

METHODS: The expressions of BMP-2 and BMP-6 in 30 carcinoma liver tissue samples and 30 normal liver tissue samples were detected and analyzed by reverse transcriptase PCR and Western blot.

RESULTS: The relative level of BMP-2 and BMP-6 mRNA was significantly lower in the normal liver tissue samples than in the liver carcinoma tissue samples (0.3245 ± 0.1127 vs 0.8298 ± 0.1187, 0.2947 ± 0.1853 vs 0.7145 ± 0.1373, both P < 0.05). The relative level of BMP-2 and BMP-6 mRNA in III, IV stages of liver cancer was significantly higher than that in I, II stages (0.92431 ± 0.1234 vs 0.69355 ± 0.1925, 0.8354 ± 0.1423 vs 0.6043 ± 0.1234, both P < 0.05). The expression level of BMP-2 and BMP-6 protein were significantly higher in the metastatic liver cancer compared with that without metastasis (0.9854 ± 0.2888 vs 0.6244 ± 0.3087, 0.9076 ± 0.1276 vs 0.5678 ± 0.2493, both P < 0.01).

CONCLUSION: Up-regulated expressions of BMP-2 and BMP-6 play an important role in liver cancer. It may have the active role in invasion and metastasis of liver cancer.

PI3K/Akt-dependent transcriptional regulation and activation of BMP-2-Smad signaling by NF-kappaB in metastatic prostate cancer cells

BACKGROUND

Bone morphogenetic proteins (BMPs) exert osteoinductive effects in prostate cancer (PC) via uncharacterized mechanisms. In this study, we investigated whether the nuclear transcription factor NF-kappaB, implicated in PC metastasis, is involved in transcriptional regulation and activation of BMP-2 or BMP-4/Smad signaling in PC cells.

METHODS

NF-kappaB inhibition was achieved by IkappaBalpha super-repressor adenoviral vector and activation was monitored by EMSA and reporter assays. BMP expression and activation was measured by PCR and reporter assays. Promoter binding assay was performed by chromatin immunoprecipitation (ChIP) assay. Smad1/5/8 phosphorylation was measured by Western blot analysis.

RESULTS

PCR and chimeric BMP-2 and BMP-4 luciferase assays demonstrate that NF-kappaB confers robust and selective activation of BMP-2 in p65 overexpressing or rhTNF-alpha-stimulated PC cells. Inhibition of NF-kappaB significantly reduced transcript levels and autocrine production of BMP-2 by rhTNF-alpha stimulated C4-2B cells and to a lesser extent by the parental LNCaP cells. Selective inhibition of PI3K/Akt suppressed the NF-kappaB-induced BMP-2 promoter activity. Furthermore, suppression of NF-kappaB activation decreased the transcript levels and BMP-2-induced phosphorylation of Smad1/5/8, critical downstream targets of BMP-2 signaling in PC cells. Notably, the activation of BMPRII by BMP-2 is required for modulation of Smad activation by NF-kappaB in PC cells. Based on ChIP analysis, the transcriptional regulation of BMP-2 gene by NF-kappaB may be partially attributed to binding to kappab site on the BMP-2 promoter.

CONCLUSIONS

The data suggest that PI3K/Akt-NF-kappaB axis may promote PC bone metastasis in part by regulating transcription and activation of the BMP-2-Smad signaling cascade in osteotropic PC cells.

Influence of simultaneous targeting of the bone morphogenetic protein pathway and RANK/RANKL axis in osteolytic prostate cancer lesion in bone

Metastasis to bone is the leading cause of morbidity and mortality in advanced prostate cancer patients. Considering the complex reciprocal interactions between the tumor cells and the bone microenvironment, there is increasing interest in developing combination therapies targeting both the tumor growth and the bone microenvironment. In this study, we investigated the effect of simultaneous blockade of BMP pathway and RANK/RANKL axis in an osteolytic prostate cancer lesion in bone. We used a retroviral vector encoding noggin (RetroNoggin) to antagonize the effect of BMPs and RANK:Fc, which is a recombinant RANKL antagonist was used to inhibit RANK/RANKL axis. The tumor growth and bone loss were evaluated using plain radiographs, hind limb tumor measurements, micro PET/CT ((18)FDG and (18)F-fluoride tracer), and histology. Tibias implanted with PC-3 cells developed pure osteolytic lesions at 2-weeks with progressive increase in cortical bone destruction at successive time points. Tibias implanted with PC-3 cells over expressing noggin (RetroNoggin) resulted in reduced tumor size and decreased bone loss compared to the implanted tibias in untreated control animals. RANK:Fc administration inhibited the formation of osteoclasts, delayed the development of osteolytic lesions, decreased bone loss and reduced tumor size in tibias implanted with PC-3 cells. The combination therapy with RANK:Fc and noggin over expression effectively delayed the radiographic development of osteolytic lesions, and decreased the bone loss and tumor burden compared to implanted tibias treated with noggin over expression alone. Furthermore, the animals treated with the combination strategy exhibited decreased bone loss (micro CT) and lower tumor burden (FDG micro PET) compared to animals treated with RANK:Fc alone. Combined blockade of RANK/RANKL axis and BMP pathway resulted in reduced tumor burden and decreased bone loss compared to inhibition of either individual pathway alone in osteolytic prostate cancer lesion in bone. These results suggest that simultaneous targeting of tumor cells and osteoclasts may be the most effective method of inhibiting the progression of established osteolytic metastatic lesions in vivo.

The prognostic significance of BMP-6 signaling in prostate cancer

The importance of bone-morphogenetic proteins in prostate cancer is well recognized. Bone-morphogenetic protein-6 overexpression has been shown to increase the aggressiveness and invasiveness of prostate cancer cells. Recent studies on noggin and sclerostin, potent inhibitors of bone-morphogenetic protein signaling, have found that noggin also modifies the ability of prostate cancer cells to metastasize to bone. Taken together, these results suggest that bone-morphogenetic protein-6 signaling is important in prostate cancer progression. Our study investigated the expression of bone-morphogenetic protein-6, noggin and sclerostin in human prostate specimens (n=136) by immunohistochemical staining. We found that bone-morphogenetic protein-6 was increased (P<0.001), whereas sclerostin was decreased (P=0.004) in prostate cancer compared with nodular hyperplasia. In addition, significantly higher level of bone-morphogenetic protein-6 expression was observed in high-grade prostate cancer with Gleason score >or=7 (P=0.027). Bone-morphogenetic protein-6, noggin and sclerostin alone could not predict the development of distant metastasis in our patient cohort. However, high level of bone-morphogenetic protein-6 and low level of noggin, or high level of bone-morphogenetic protein-6 and low level of both noggin and sclerostin expression in primary prostate cancer significantly predicted development of distant metastasis. The predictive value was still valid when only high-grade prostate cancers were included or when patients with secondary lesion other than bone were excluded. Taken together, these results suggest that a high level of bone-morphogenetic protein-6 signaling, resulting from increased expression of bone-morphogenetic protein-6 and decreased expression of its inhibitors, might promote the development of prostate cancer metastases. Our results also imply the potential use of bone-morphogenetic protein-6, noggin and sclerostin expression together as a prognostic predictor for metastatic progression of prostate cancer.

Bone morphogenetic protein-9 induces apoptosis in prostate cancer cells, the role of prostate apoptosis response-4

Bone morphogenetic proteins (BMP) have been implicated in the development of bone metastases in prostate cancer. In this study, we investigated the role which BMP-9 played in prostate cancer and found that the expression of BMP-9 was decreased or absent in prostate cancer, particularly in the foci of higher grade disease. We further investigated the influence of BMP-9 on the biological behaviors of prostate cancer cells. The forced overexpression of BMP-9 prevented the in vitro growth, cell-matrix adhesion, invasion, and migration of prostate cancer cells. We also elucidated that BMP-9 induced apoptosis in PC-3 cells through the up-regulation of prostate apoptosis response-4. Among the receptors which have been implicated in the signaling of BMP-9, BMPR-IB and BMPR-II have also been implicated in the development and progression of prostate cancer. Knockdown of BMPR-IB or BMPR-II using respective hammerhead ribozyme transgenes could promote cell growth in vitro. We also found that BMPR-II is indispensable for the Smad-dependent signal transduction by BMP-9 in PC-3 cells, in which Smad-1 was phosphorylated and translocated from the cytoplasm into the nuclei. Taken together, BMP-9 inhibits the growth of prostate cancer cells due to the induced apoptosis, which is related to an up-regulation of prostate apoptosis response-4 through a Smad-dependent pathway. BMP-9 could also prevent the migration and invasiveness of prostate cancer. This suggests that BMP-9 may function as a tumor suppressor and apoptosis regulator in prostate cancer.

BMP7 influences proliferation, migration, and invasion of breast cancer cells

Bone morphogenetic protein 7 (BMP7) is a signaling molecule originally identified based on its ability to form bone. It is essential during development, and more recently has also been implicated in cancer pathogenesis. We have recently shown that BMP7 is overexpressed in breast cancer, and that this increased expression is associated with early bone metastasis formation. In the present study, we explored the possible contribution of BMP7 function to the breast cancer cell phenotype. A two-way approach was applied in which BMP7 was silenced using RNA interference in three cell lines with high endogenous expression or, conversely, exogenous BMP7 was added to the growth medium of five cell lines with low or no BMP7 expression. These manipulations led to diverse cell line-specific phenotypic responses. BMP7 manipulation increased cell growth in two cell lines (BT-474, MDA-MB-231), and BMP7 treatment led to reduced growth in four cell lines (HCC1954, MDA-MB-361, T-47D, and ZR-75-30). Growth changes were due to distinct mechanisms since BMP7 silencing led to growth inhibition via G1 arrest in BT-474 cells, whereas BMP7 treatment protected MDA-MB-231 cells from apoptosis. Furthermore, BMP7 stimulation altered the MDA-MB-231 phenotype by inducing a distinct 2.3-fold increase in cell migration and an even more dramatic 3.9-fold increase in cell invasion. In conclusion, BMP7 can promote and inhibit cell growth in breast cancer cell lines and, in a suitable environment, can also considerably induce breast cancer cell migration and invasion.

The Bone Morphogenesis Protein-2 (BMP-2) is associated with progression to metastatic disease in gastric cancer

PURPOSE

Bone Morphogenetic Proteins (BMPs) are members of the TGF-beta superfamily and it has been demonstrated that BMPs enhance migration, invasion and metastasis. The purpose of this study was to identify the association between the serum BMP-2 level and the progression status of gastric cancer.

MATERIALS AND METHODS

Fifty-five patients with metastatic gastric cancer (metastatic disease group), six patients with early gastric cancer without lymph node metastasis (the EGC group), and ten healthy control subjects were enrolled in this study. The serum BMP-2 level was quantified by use of a commercially available ELISA kit. In EGC group patients and patients with metastatic disease, whole blood was obtained before endoscopic mucosal resection and before the commencement of a scheduled cycle of systemic chemotherapy, respectively.

RESULTS

No significant difference in the mean serum BMP-2 levels was observed between the control subjects and the EGC group patients (87.95 pg/ml for the control subjects and 84.50 pg/ml for the EGC group, p=1.0). However, the metastatic disease group patients had a significantly higher level of serum BMP (179.61 pg/ml) than the control subjects and EGC group patients (87.95 pg/ml for the control subjects and 84.50 pg/ml for the EGC group, p<0.0001). Moreover, the mean serum BMP-2 level from patients with a bone metastasis was significantly higher than the mean serum BMP-2 level from patients without a bone metastasis (204.73 pg/ml versus 173.33 pg/ml, p=0.021).

CONCLUSIONS

BMP-2 seems to have a role in progression to metastatic disease in gastric cancer, especially in the late stage of tumorigenesis, including invasion and metastasis. BMP-2 may facilitate bone metastasis in gastric cancer. To confirm these findings, further studies are required with tissue specimens and the use of a cancer cell line.

Antitumoral activity and osteogenic potential of mesenchymal stem cells expressing the urokinase-type plasminogen antagonist amino-terminal fragment in a murine model of osteolytic tumor

Prostate cancer metastasis to bone results in mixed osteolytic and osteoblastic lesions associated with high morbidity, and there is mounting evidence that the urokinase-type plasminogen system is causatively involved in the progression of prostate cancer. Adult mesenchymal stem cells (MSCs) are promising tools for cell-mediated gene therapy with the advantage of osteogenic potential, a critical issue in the case of osteolytic metastases. In this study, we evaluated the therapeutic use of engineered murine MSCs for in vivo delivery of the urokinase-type plasminogen antagonist amino-terminal fragment (hATF) to impair osteolytic prostate cancer cell progression in bone and to repair bone lesions. Bioluminescence imaging revealed that both primary MSCs and the MSC line C3H10T1/2 (C3) expressing hATF (MSC-hATF) significantly inhibited intratibial PC-3 Luciferase (Luc) growth following coinjection in SCID mice. Furthermore, microcomputed tomography imaging of vascular network clearly demonstrated a significant decrease in tumor-associated angiogenesis and a protection from tumor-induced osteolysis in MSC-hATF-treated mice. Importantly, the osteogenic potential of MSC-hATF cells was unaffected, and an area of new bone formation was evidenced in 60% of animals. Together, these data support the concept of MSC-based therapy of tumor osteolysis disease, indicating that MSCs may combine properties of vehicle for angiostatic agent with osteogenic potential. Disclosure of potential conflicts of interest is found at the end of this article.

Bone morphogenetic protein signaling enhances invasion and bone metastasis of breast cancer cells through Smad pathway

Transforming growth factor (TGF)-beta is known to promote tumor invasion and metastasis. Although bone morphogenetic proteins (BMPs), members of the TGF-beta family, are expressed in a variety of human carcinoma cell lines, their roles in tumor progression have not been fully clarified. In this study, we sought to determine the roles of BMPs in the progression of breast cancer bone metastasis using human breast cancer samples and a mouse xenograft model. Immunohistochemical analysis of samples from breast cancer patients as well as a mouse xenograft model of MDA-231-D, highly metastatic human breast cancer cells, revealed phospho-Smad2 and phospho-Smad1/5/8 staining in the nuclei of cancer cells in primary tumor and/or bone metastasis. Using a functional in vivo bioluminescence imaging system, we showed that TGF-beta- and BMP-induced transcriptional pathways are active in bone metastatic lesions in vivo. In addition, both TGF-beta3 and BMP-2 promoted the motility and invasiveness of the MDA-231-D cells in vitro. Moreover, expression of dominant-negative receptors for TGF-beta and/or BMPs in the MDA-231-D cells inhibited invasiveness in vitro and bone metastasis in the xenograft model. These results suggest that BMPs as well as TGF-beta promote invasion and bone metastasis of breast cancer.

Molecular profiling of bladder cancer: involvement of the TGF-beta pathway in bladder cancer progression

A human bladder cancer model of nine cell sublines derived from the BL17/2 cell line was used to evaluate genes related to disease progression. Molecular profiling of sublines that were non-tumorigenic and invasive in nude mice was performed and identified 1367 differentially-expressed genes. Quantitative real-time PCR analysis of six transforming growth factor-beta (TGF-beta) pathway genes using the entire panel of nine cell lines was performed. Bone morphogenetic protein-2 expression was significantly associated with in vivo tumorigenicity of the cell lines (p=0.0228, Mann-Whitney); inhibin-betaB was related to their invasiveness (p=0.0468, Mann-Whitney). Analysis of conditioned medium showed TGF-beta1 production to be significantly associated with the phenotype of the cell line. The study shows the possible involvement of the TGF-beta pathway in bladder cancer progression.

The use of bone morphogenetic protein in spine fusion

BACKGROUND CONTEXT

Because pseudarthrosis remains a clinically significant complication after spinal arthrodesis, the role of recombinant bone morphogenetic proteins (BMPs) is continually evaluated in spine surgery.

PURPOSE

This article reviews the important literature in clinical research involving the use of BMPs in the augmentation of spinal fusion.

STUDY DESIGN/SETTING

Review article.

METHODS

A literature search was performed via MEDLINE through PubMed with the dates January 1960 to July 2007 using the keywords "bone morphogenetic protein, BMP, spinal arthrodesis, and/or bone healing." Pertinent preclinical and clinical publications were chosen based on relevance and quality for inclusion in this study.

RESULTS

Publications focused on the historical context and potential clinical applications using BMP were selected to delineate the risks, benefits, and current indications for the augmentation of spinal arthrodesis.

CONCLUSIONS

Although multiple commercially available recombinant BMPs have demonstrated clinical success in interbody and posterolateral fusions, the associated costs preclude its routine use in spinal arthrodesis. The spine surgeon must assess each patient individually based on age, bone quality, diagnosis, comorbidities, and risks of nonunion to determine the cost effectiveness of the use of BMP to augment spinal fusion.

Cancer metastasis facilitated by developmental pathways: Sonic hedgehog, Notch, and bone morphogenic proteins

This review will highlight the significance of three critical pathways in developmental biology and our emerging understanding of their roles in regulating tumor metastasis: Bone morphogenic protein (BMP), Notch and Sonic hedgehog (SHH). We will discuss parallels between their known roles in development and how these processes can be used by tumor cells to create microenvironments that enhance tumor metastasis. That tumor cells usurp pathways critical to the developing embryo is not surprising, as many of the normal developmental programs include processes that are also seen during tumor progression to a metastatic phenotype, including epithelial to mesenchymal transition (EMT), tissue specific morphogenesis, cellular motility and invasion. BMPs are involved in EMT, contribute to tissue specific morphogenesis, and are expressed in highly-metastatic tumor cells. BMPs have also been hypothesized to have a role in the establishment of a pre-neoplastic niche. Notch and SHH facilitate neovascularization, angiogenesis, EMT and can contribute to the maintenance of highly-metastatic tumor stem cells.