Expression of bone morphogenetic proteins in human prostatic adenocarcinoma and benign prostatic hyperplasia

NTRK3-Rearranged Prostatic Acinar Adenocarcinoma: Report of a Patient and Review of the Literature

Molecular investigations have led to increased therapeutic options for prostatic adenocarcinoma. A single case report of a PRPSAP1::NTRK3 gene fusion occurring in prostate cancer was previously reported. A review of the literature revealed that NTRK gene rearrangements are exceedingly rare molecular events in prostate cancer. NTRK gene fusions can be oncogenic drivers or develop as resistance mechanisms. The tumor-agnostic approvals of TRK inhibitors by the FDA provide additional rationale for molecular investigations of aggressive prostatic adenocarcinomas. This may prove to be an additional therapeutic option for patients with aggressive prostatic carcinomas refractory to initial therapy. We report a case of an aggressive castrate-resistant prostatic adenocarcinoma with a BMP6::NTRK3 gene fusion.

Management of non-unions of the malleolar fractures- Current Evidence

Although malleolar non-union is uncommon, it is associated with significant morbidity. Managing this problem requires understanding ankle fracture biomechanics and bone healing. We present in this article the pertinent points to be considered in evaluating and managing patients with malleolar non-union. Our discussion will focus on the important risk factors contributing to this problem, and the need to carefully consider the biomechanical stability and the biological environment to ensure successful bony unions.

Bone morphogenetic protein pathway responses and alterations of osteogenesis in metastatic prostate cancers

BACKGROUND

Prostate cancer is a common cancer in men that annually results in more than 33 000 US deaths. Mortality from prostate cancer is largely from metastatic disease, reflecting on the great strides in the last century of treatments in care for the localized disease. Metastatic castrate resistant prostate cancer (mCRPC) will commonly travel to the bone, creating unique bone pathology that requires nuanced treatments in those sites with surgical, radio and chemotherapeutic interventions. The bone morphogenetic protein (BMP) pathway has been historically studied in the capacity to regulate the osteogenic nature of new bone. New mineralized bone generation is a frequent and common observation in mCRPC and referred to as blastic bone lesions. Less common are bone destructive lesions that are termed lytic.

METHODS

We queried the cancer genome atlas (TCGA) prostate cancer databases for the expression of the BMP pathway and found that distinct gene expression of the ligands, soluble antagonists, receptors, and intracellular mediators were altered in localized versus metastatic disease. Human prostate cancer cell lines have an innate ability to promote blastic- or lytic-like bone lesions and we hypothesized that inhibiting BMP signaling in these cell lines would result in a distinct change in osteogenesis gene expression with BMP inhibition.

RESULTS

We found unique and common changes by comparing these cell lines response and unique BMP pathway alterations. We treated human PCa cell lines with distinct bone pathologic phenotypes with the BMP inhibitor DMH1 and found distinct osteogenesis responses. We analyzed distinct sites of metastatic PCa in the TCGA and found that BMP signaling was selectively altered in commons sites such as lymph node, bone and liver compared to primary tumors.

CONCLUSIONS

Overall we conclude that BMPs in metastatic prostate cancer are important signals and functional mediators of diverse processes that have potential for individualized precision oncology in mCRPC.

Gibberellin derivative GA-13315 overcomes multidrug resistance in breast cancer by up-regulating BMP6 expression

Chemoresistance represents a major obstacle in breast cancer treatment. Bone morphogenetic protein 6 (BMP6) was reported to participate in the occurrence and development of various tumors. In the present study, the results of transcriptome sequencing, qRT-PCR and western blot analysis revealed that BMP6 was down-regulated in multidrug resistant MCF-7/Adr breast cancer cells and BMP6 overexpression sensitized MCF-7/Adr cells to chemotherapeutic drugs, indicating that BMP6 downregulation was involved in the mechanisms of multidrug resistance (MDR) of MCF-7/Adr breast cancer cells. GA-13315 (GA5) is a new tetracyclic diterpenoid selected from a series of gibberellin derivatives. Here, we found that GA5 exhibited more potent anti-tumor activity in multidrug resistant MCF-7/Adr breast cancer cells and xenografts, indicating that GA5 could overcome MDR. Mechanistically, GA5 increased BMP6 expression, and BPM6 knockdown partially reversed the inhibitory effect of GA5 on cell proliferation. Furthermore, we found that ERK phosphorylation and P-gp expression were increased in MCF-7/Adr cells when compared with MCF-7 cells. Either overexpression of BMP6 or treatment the cells with GA5 significantly decreased ERK phosphorylation and P-gp expression, indicating that GA5 reversed MDR of MCF-7/Adr cells by upregulating BMP6, thereby inhibiting the activation of ERK signaling pathway and reducing P-gp expression. Collectively, our present study demonstrated that the MDR of MCF-7/Adr cells was closely related to the low expression of BMP6, and revealed the molecular mechanisms by which GA5 overcame MDR in breast cancer, providing evidence in supporting the development of GA5 to be a promising agent for overcoming MDR in clinical cancer therapy in the future.

DNA methylation-based diagnostic, prognostic, and predictive biomarkers in colorectal cancer

DNA methylation is an epigenetic mechanism regulating gene expression. Changes in DNA methylation were suggested to be useful biomarkers for diagnosis, and for the determination of prognosis and treatment response. Here, we provide an overview of methylation-based biomarkers in colorectal cancer. First, we start with the two methylation-based diagnostic biomarkers already approved for colorectal cancer, SEPT9 and the combination of NDRG4 and BMP3. Then, we provide a list-based overview of new biomarker candidates depending on the sample source including plasma, stool, urine, and surgically removed tumor tissues. The most often identified markers like SDC2, VIM, APC, MGMT, SFRP1, SFRP2, and NDRG4 have distinct functions previously linked to tumor progression. Although numerous studies have identified tumor-specific methylation changes, most of these alterations were observed in a single study only. The lack of validation in independent samples means low reproducibility and is a major limitation. The genome-wide determination of methylation status (methylome) can provide data to solve these issues. In the third section of the review, methylome studies focusing on different aspects related to CRC, including precancerous lesions, CRC-specific changes, molecular subtypes, aging, and chemotherapy response are summarized. Notably, techniques simultaneously analyzing a large set of regions can also uncover epigenetic regulation of genes which have not yet been associated with tumorigenesis previously. A remaining constraint of studies published to date is the low patient number utilized in these preventing the identification of clinically valuable biomarker candidates. Either future large-scale studies or the integration of already available methylome-level data will be necessary to uncover biomarkers sufficiently robust for clinical application.

Targeting the BMP Pathway in Prostate Cancer Induced Bone Disease

From the 33,000 men in the U.S. who die from prostate cancer each year, the majority of these patients exhibit metastatic disease with bone being the most common site of metastasis. Prostate cancer bone metastases are commonly blastic, exhibiting new growth of unhealthy sclerotic bone, which can cause painful skeletal related events. Patient's current care entails androgen deprivation therapy, anti-resorptive agents, radiation, and chemotherapy to help control the spread of the cancer but little intervention is available to treat blastic bone disease. The transforming growth factor beta (TGFβ) and bone morphogenetic protein (BMP) pathways are known to regulate bone growth and resorption of destructive lytic bone lesions, yet the role of TGFβ/BMP signaling in prostate cancer blastic vs lytic bone lesions are not fully understood. We hypothesized that to target the BMP/TGFβ pathway, a useful biomarker of bone lytic or blastic pathology would have superior response. We show distinct BMP vs. TGFβ signaling in clinical samples of human prostate cancer bone metastases with either lytic or blastic pathologies. BMPs exhibit distinct effects on bone homeostasis, so to examine the effect of BMP inhibition on healthy bone, we treated mice with the BMP receptor small molecule antagonist DMH1 and saw a modest temporary improvement in bone health, with increased trabecular bone. We next sought to use the BMP inhibitor DMH1 to treat bone metastasis engraftment seeded by a caudal artery injection of the lytic human prostate cell line PC3 in immunodeficient mice. The colonization by PC3 cells to the bone were restricted with DMH1 treatment and bone health was importantly preserved. We next proceeded to test BMP inhibition in an injury model of established bone metastasis via intratibial injection of the MYC-CaP mouse prostate cell line into FVBN syngeneic mice. DMH1 treated mice had a modest decrease in trabecular bone and reduced lymphocytes in circulation without affecting tumor growth. Taken together we show unique responses to BMP inhibition in metastatic prostate cancer in the bone. These studies suggest that profiling bone lesions in metastatic prostate cancer can help identify therapeutic targets that not only treat the metastatic tumor but also address the need to better treat the distinct tumor induced bone disease.

Screening key miRNAs and genes in prostate cancer by microarray analysis

BACKGROUND

Prostate cancer (PCa) is the second most frequent cancer and the fifth leading cause of cancer-related death in men while the mechanisms remain unclear.

METHODS

Differentially expressed mRNAs (DEmRNAs) and miRNAs (DEmiRNAs) between PCa and non-tumor controls were identified by using microarray analysis. Functional annotation of DEmRNAs, construction of protein-protein interaction (PPI) network and prediction of upstream transcription factors and downstream target DEmRNAs of DEmiRNAs were conducted to further research functions of key DEmRNAs and DEmiRNAs. Validation of selected DEmRNAs and survival analysis were conducted by using The Cancer Genome Atlas (TCGA).

RESULTS

Total of 91 DEmRNAs and 62 DEmiRNAs were obtained. Thrombospondin-4 precursor (THBS4) was the most significantly up-regulated DEmRNA whose product was predicted to interact with the hub protein of the PCa-specific PPI network, collagen type I alpha 1 chain (COL1A1). Both ATP binding cassette subfamily C member 4 (ABCC4) and endothelin receptor type B (EDNRB) have great prognostic value for PCa. Thrombospondin type 1 domain containing 4 (THSD4) was a down-regulated DEmRNA regulated by several cancer-related miRNAs including has-miR-107, hsa-miR-3175 and hsa-miR-484. Two miRNAs (hsa-miR-428 and hsa-miR-4284) involve in PCa by regulating BMP5-BAMBI interaction and TGF-beta signaling pathway. The expression of selected DEmRNAs between PCa and non-tumor controls in TCGA was consistent with that in our microarray analysis, generally.

CONCLUSIONS

Key DEmRNAs and DEmiRNAs between PCa and non-tumor controls were identified in this study which provided clues for exploring the molecular mechanism and developing potential biomarkers and therapeutic target sites for PCa.

Gene Selection for the Discrimination of Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide. Cancer discrimination is a typical application of gene expression analysis using a microarray technique. However, microarray data suffer from the curse of dimensionality and usual imbalanced class distribution between the majority (tumor samples) and minority (normal samples) classes. Feature gene selection is necessary and important for cancer discrimination.

OBJECTIVES

To select feature genes for the discrimination of CRC.

METHODS

We improve the feature selection algorithm based on differential evolution, DEFSw by using RUSBoost classifier and weight accuracy instead of the common classifier and evaluation measure for selecting feature genes from imbalance data. We firstly extract differently expressed genes (DEGs) from the CRC dataset of the TCGA and then select the feature genes from the DEGs using the improved DEFSw algorithm. Finally, we validate the selected feature gene sets using independent datasets and retrieve the cancer related information for these genes based on text mining through the Coremine Medical online database.

RESULTS

We select out 16 single-gene feature sets for colorectal cancer discrimination and 19 single-gene feature sets only for colon cancer discrimination.

CONCLUSIONS

In summary, we find a series of high potential candidate biomarkers or signatures, which can discriminate either or both of colon cancer and rectal cancer with high sensitivity and specificity.

The Use of Bone Grafts, Bone Graft Substitutes, and Orthobiologics for Osseous Healing in Foot and Ankle Surgery

Achieving fusion in osseous procedures about the foot and ankle presents unique challenges to the surgeon. Many patients have comorbidities that reduce osseous healing rates, and the limited space and high weightbearing demand placed on fusion sites makes the choice of bone graft, bone graft substitute, or orthobiologic agent of utmost importance. In this review, we discuss the essential characteristics of grafts, including their osteoconductive, osteoinductive, osteogenic, and angiogenic properties. Autologous bone graft remains the gold standard and contains all these properties. However, the convenience and lack of donor site morbidity of synthetic bone grafts, allografts, and orthobiologics, including growth factors and allogenic stem cells, has led to these being used commonly as augments.

Molecular Pathogenesis and Diagnostic Imaging of Metastatic Jaw Tumors

Metastasis is the spread of malignant cells from a primary tumor to distant sites through lymphatics or blood vessels. Malignant lesions metastasizing to the oral and perioral region are a rarity indeed. Malignant lesions could metastasize to both soft tissue of oral cavity and the hard tissues of the jaws and recent meta-analysis showed that metastasis is more common in the jaws than oral soft tissues because of rich vascular supply. The incidence is very low when compared to the incidence of primary oral cancers; nevertheless, one has to include in the diagnostic workup, metastatic malignant lesions, when an irregular ill-defined radiolucency or radiodensity with ragged edges in noted. It could be a challenging task for a diagnostician, in cases with the presence and location of the primary tumor is unknown. Advanced oral imaging technologies and biochemical markers play a vital role in diagnosing such lesions.

Emerging roles of the bone morphogenetic protein pathway in cancer: potential therapeutic target for kinase inhibition

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-β (TGF-β) family signalling pathway. Similar to TGF-β, the complex roles of BMPs in development and disease are demonstrated by their dichotomous roles in various cancers and cancer stages. Although early studies implicated BMP signalling in tumour suppressive phenotypes, the results of more recent experiments recognize BMPs as potent tumour promoters. Many of these complexities are becoming illuminated by understanding the role of BMPs in their contextual role in unique cell types of cancer and the impact of their surrounding tumour microenvironment. Here we review the emerging roles of BMP signalling in cancer, with a focus on the molecular underpinnings of BMP signalling in individual cancers as a valid therapeutic target for cancer prevention and treatment.

Autotaxin-lysophosphatidic acid-LPA3 signaling at the embryo-epithelial boundary controls decidualization pathways

During pregnancy, up-regulation of heparin-binding (HB-) EGF and cyclooxygenase-2 (COX-2) in the uterine epithelium contributes to decidualization, a series of uterine morphological changes required for placental formation and fetal development. Here, we report a key role for the lipid mediator lysophosphatidic acid (LPA) in decidualization, acting through its G-protein-coupled receptor LPA₃ in the uterine epithelium. Knockout of Lpar3 or inhibition of the LPA-producing enzyme autotaxin (ATX) in pregnant mice leads to HB-EGF and COX-2 down-regulation near embryos and attenuates decidual reactions. Conversely, selective pharmacological activation of LPA₃ induces decidualization via up-regulation of HB-EGF and COX-2. ATX and its substrate lysophosphatidylcholine can be detected in the uterine epithelium and in pre-implantation-stage embryos, respectively. Our results indicate that ATX-LPA-LPA₃ signaling at the embryo-epithelial boundary induces decidualization via the canonical HB-EGF and COX-2 pathways.

Coexpression of growth differentiation factor 11 and reactive oxygen species in metastatic oral cancer and its role in inducing the epithelial to mesenchymal transition

OBJECTIVES

The aim of this study was to investigate growth differentiation factor 11 (GDF11) and reactive oxygen species (ROS) expression in metastatic oral cancer and explored their roles in inducing epithelial to mesenchymal transition (EMT).

STUDY DESIGN

The expression of GDF11, ROS, and EMT-related markers was evaluated in primary tumor tissues from patients with oral squamous cell carcinoma (OSCC). SCC-9 cells, a human tongue carcinoma cell line, were treated with recombinant GDF11. Induction of EMT, expression of EMT-related markers, and the effect of ROS on EMT in SCC-9 cells were analyzed.

RESULTS

Overexpression of GDF11 and ROS was observed in patients with metastatic oral cancer. Downregulated expression of E-cadherin and upregulated expression of vimentin, δ-EF1, SIP-1, MMP-2, and MMP-9 were observed in patients with metastatic oral cancer, relative to the expression of these factors in patients with nonmetastatic oral cancer. With recombinant GDF11 treatment, obvious spindle-shaped cells appeared, and gene expressions of EMT-related markers were altered in SCC-9 cells. Treatment with the powerful antioxidant N-acetylcysteine inhibited GDF11-induced EMT and cell migration.

CONCLUSIONS

GDF11 induces EMT and cell migration with ROS involvement in SCC-9 cells. Overexpression of GDF11 and ROS is associated with metastatic oral cancer. GDF11 and ROS may participate in metastasis of oral cancer through EMT.

Bone morphogenetic protein-2 and tumor growth: Diverse effects and possibilities for therapy

Concern regarding safety with respect to the clinical use of human bone morphogenetic protein-2 (BMP-2) has become an increasingly controversial topic. The role of BMP-2 in carcinogenesis is of particular concern. Although there have been many studies of this topic, the results have been contradictory and confusing. We conducted a systematic review of articles that are relevant to the relationship or effect of BMP-2 on all types of tumors and a total of 97 articles were included. Studies reported in these articles were classified into three major types: "expression studies", "in vitro studies", and "in vivo studies". An obvious pattern was that those works that hypothesize an inhibitory effect for BMP-2 most often examined only the proliferative properties of the tumor cells. This subset of studies also contained an extraordinary number of contradictory findings which made drawing a reliable general conclusion impossible. In general, we support a pro-tumorigenesis role for BMP-2 based on the data from these in vitro cell studies and in vivo animal studies, however, more clinical studies should be carried out to help make a firm conclusion.

Association Between BMP-2 and Carcinogenicity

STUDY DESIGN

Literature review.

OBJECTIVE

To evaluate the association between recombinant human bone morphogenetic protein-2 (rhBMP-2) and malignancy.

SUMMARY OF BACKGROUND DATA

The use of rhBMP-2 in spine surgery has been the topic of much debate as studies assessing the association between rhBMP-2 and malignancy have come to conflicting conclusions.

METHODS

A systematic review of the literature was performed using the PubMed-National Library of Medicine/National Institute of Health databases. Only non-clinical studies directly addressing BMP-2 and cancer were included. Articles were categorized by study type (animal, in vitro cell line/human/animal), primary malignancy, cancer attributes, and whether BMP-2 was pro-malignancy or not.

RESULTS

A total of 4,131 articles were reviewed. Of those, 515 articles made reference to both BMP-2 and cancer, 99 of which were found to directly examine the role of BMP-2 in cancer. Seventy-five studies were in vitro and 24 were animal studies. Forty-three studies concluded that BMP-2 enhanced cancer function, whereas 18 studies found that BMP-2 suppressed malignancy. Thirty-six studies did not examine whether BMP-2 enhanced or suppressed cancer function. Fifteen studies demonstrated BMP-2 dose dependence (9 enhancement, 6 suppression) and one study demonstrated no dose dependence. Nine studies demonstrated BMP-2 time dependence (6 enhancement, 3 suppression). However, no study demonstrated that BMP-2 caused cancer de novo.

CONCLUSION

Currently, conflicting data exist with regard to the effect of exogenous BMP-2 on cancer. The majority of studies addressed the role of BMP-2 in prostate (17%), breast (17%), and lung (15%) cancers. Most were in vitro studies (75%) and examined cancer invasiveness and metastatic potential (37%). Of 99 studies, there was no demonstration of BMP-2 causing cancer de novo. However, 43% of studies suggested that BMP-2 enhances tumor function, motivating more definitive research on the topic that also includes clinically meaningful dose- and time-dependence.

LEVEL OF EVIDENCE

2.

Bone morphogenetic proteins in tumour associated angiogenesis and implication in cancer therapies

Bone morphogenetic protein (BMP) belongs to transforming growth factor-β superfamily. To date, more than 20 BMPs have been identified in humans. BMPs play a critical role in embryonic and postnatal development, and also in maintaining homeostasis in different organs and tissues by regulating cell differentiation, proliferation, survival and motility. They play important roles in the development and progression of certain malignancies, including prostate cancer, breast cancer, lung cancer, etc. Recently, more evidence shows that BMPs are also involved in tumour associated angiogenesis. For example BMP can either directly regulate the functions of vascular endothelial cells or indirectly influence the angiogenesis via regulation of angiogenic factors, such as vascular endothelial growth factor (VEGF). Such crosstalk can also be reflected in the interaction with other angiogenic factors, like hepatocyte growth factor (HGF) and basic fibroblast growth factor (bFGF). All these factors are involved in the orchestration of the angiogenic process during tumour development and progression. Review of the relevant studies will provide a comprehensive prospective on current understanding and shed light on the corresponding therapeutic opportunity.

Hepcidin regulation in prostate and its disruption in prostate cancer

Hepcidin is a circulating peptide hormone made by the liver that is a central regulator of systemic iron uptake and recycling. Here, we report that prostate epithelial cells also synthesize hepcidin, and that synthesis and secretion of hepcidin are markedly increased in prostate cancer cells and tissue. Prostatic hepcidin functions as an autocrine hormone, decreasing cell surface ferroportin, an iron exporter, increasing intracellular iron retention, and promoting prostate cancer cell survival. Synthesis of hepcidin in prostate cancer is controlled by a unique intersection of pathways that involves BMP4/7, IL6, Wnt, and the dual BMP and Wnt antagonist, SOSTDC1. Epigenetic silencing of SOSTDC1 through methylation is increased in prostate cancer and is associated with accelerated disease progression in patients with prostate cancer. These results establish a new connection between iron metabolism and prostate cancer, and suggest that prostatic dysregulation of hepcidin contributes to prostate cancer growth and progression.

Beta-catenin is elevated in human benign prostatic hyperplasia specimens compared to histologically normal prostate tissue

Benign prostatic hyperplasia (BPH) is linked to lower urinary tract symptoms (LUTS) such as incomplete bladder emptying, urinary frequency and urgency. Mechanisms responsible for BPH are not fully known. Here, we tested whether beta-catenin (CTNNB1) immunostaining intensity and distribution differ in human glandular BPH tissue specimens compared to normal prostate tissue. Multiplex immunostaining of CTNNB1, its putative transcriptional target gene lymphoid enhancer binding factor 1 (LEF1), and the epithelial marker E-cadherin were examined in clinical human prostate specimens with or without histological BPH (pure epithelial or mixed stromal-epithelial nodules). BPH specimens were obtained from 24 men who experienced LUTS and underwent transurethral resection of the prostate surgery. Control specimens were tumor-adjacent histologically normal prostate tissue from 48 patients who underwent radical prostatectomy. The resulting multispectral images were unmixed and optical densities recorded to quantify staining abundance, cellular (membranous, cytoplasmic, and nuclear) and tissue localization (stromal versus epithelial), and determination of percentage of CTNNB1-positive cells. The following CTNNB1 indices were significantly higher in BPH compared to normal prostate tissue: overall staining intensity, staining intensity in prostate stromal cell membranes, cytoplasm and nuclei, and prostate epithelial cell nuclei. The following LEF1 indices were significantly lower in BPH compared to tumor-adjacent normal prostate tissue: stromal LEF1 staining intensity, percentage of LEF1-positive stromal cells, and intensity of LEF1 staining in stromal cell membranes, cytoplasm, and nuclei. The percentage of stromal cells with CTNNB1(+)/LEF1(-) nuclei was higher and percentage of stromal cells with CTNNB1(-)/LEF1(+) nuclei was lower in BPH compared to tumor-adjacent normal prostate tissues. These results support the hypothesis that CTNNB1 expression increases in specific BPH tissue compartments. Further, since nuclear LEF1 staining does not coincide with cytoplasmic or nuclear CTNNB1 staining, it does not appear to be a reliable index of CTNNB1 activity in adult human prostate.

The host microenvironment influences prostate cancer invasion, systemic spread, bone colonization, and osteoblastic metastasis

Prostate cancer (PCa) is the second leading cause of cancer death in men worldwide. Most PCa deaths are due to osteoblastic bone metastases. What triggers PCa metastasis to the bone and what causes osteoblastic lesions remain unanswered. A major contributor to PCa metastasis is the host microenvironment. Here, we address how the primary tumor microenvironment influences PCa metastasis via integrins, extracellular proteases, and transient epithelia-mesenchymal transition (EMT) to promote PCa progression, invasion, and metastasis. We discuss how the bone-microenvironment influences metastasis; where chemotactic cytokines favor bone homing, adhesion molecules promote colonization, and bone-derived signals induce osteoblastic lesions. Animal models that fully recapitulate human PCa progression from primary tumor to bone metastasis are needed to understand the PCa pathophysiology that leads to bone metastasis. Better delineation of the specific processes involved in PCa bone metastasize is needed to prevent or treat metastatic PCa. Therapeutic regimens that focus on the tumor microenvironment could add to the PCa pharmacopeia.

Prostate cancer bone metastases acquire resistance to androgen deprivation via WNT5A-mediated BMP-6 induction

Background:

Androgen ablation is the first-line therapy for patients with metastatic prostate cancer (CaP). However, castration resistance will eventually emerge. In the present study, we have investigated the role of bone morphogenetic protein-6 (BMP-6) in the development of castration-resistant prostate cancer (CRPC) in the context of bone metastases.

Methods:

We initially investigated the clinical course of 158 men with advanced CaP who were treated with primary androgen deprivation therapy. To elucidate the underlying mechanism of CRPC in the context of bone metastases, we examined the impact of bone stromal cells on CaP in the absence of androgens using a co-culture model.

Results:

In the 158 patients, we found that the median time to prostate-specific antigen progression was significantly shorter when bone metastases were present (14 months (95% CI, 10.2–17.8 months) vs 57 months (95% CI, 19.4–94.6 months)). These results suggest that bone–tumour interactions may accelerate castration resistance. Consistent with this hypothesis, in vitro co-cultures demonstrated that CaP cells proliferated under an androgen-depleted condition when incubated with bone stromal cells. Mechanistically, gene expression analysis using quantitative polymerase chain reaction arrays showed a dramatic induction of BMP-6 by CaP cell lines in the presence of bone stromal cells. Further studies revealed that WNT5A derived from bone stromal cells induced the expression of BMP-6 by CaP cells; BMP-6 in turn stimulated cellular proliferation of CaP cells in an androgen-deprived media via a physical interaction between Smad5 and β-catenin. Intracellularly, WNT5A increased BMP-6 expression via protein kinase C/NF-κB pathway in CaP cell lines.

Conclusions:

These observations suggest that bone–CaP interaction leads to castration resistance via WNT5A/BMP-6 loop.

Hypermethylation leads to bone morphogenetic protein 6 downregulation in hepatocellular carcinoma

BACKGROUND

In the liver, bone morphogenetic protein 6 (BMP-6) maintains balanced iron metabolism. However, the mechanism that underlies greater BMP-6 expression in hepatocellular carcinoma (HCC) tissue than adjacent non-cancerous tissue is unclear. This study sought to investigate the epigenetic mechanisms of BMP-6 expression by analysing the relationship between the DNA methylation status of BMP-6 and the expression of BMP-6.

METHODS

Methylation-specific polymerase chain reaction (PCR), bisulphite sequencing PCR, the MethyLight assay, and quantitative real-time PCR were performed to examine BMP-6 methylation and mRNA expression levels. Immunohistochemistry (IHC) was performed on tissue arrays to evaluate the BMP-6 protein level.

RESULTS

BMP-6 mRNA expression was approximately 84.09% lower in HCC tissues than in adjacent non-cancerous tissues, and this low level of expression was associated with a poor prognosis. Moreover, the hypermethylation observed in HCC cell lines and HCC tissues was correlated with the BMP-6 mRNA expression level, and this correlation was validated following treatment with 5-aza-CdR, a demethylation agent. In addition, BMP-6 DNA methylation was upregulated by 68.42% in 114 clinical HCC tissue samples compared to adjacent normal tissues, whereas the BMP-6 staining intensity was downregulated by 77.03% in 75 clinical HCC tissue samples in comparison to adjacent normal tissues. Furthermore, elevated expression of BMP-6 in HCC cell lines inhibited cell colony formation.

CONCLUSIONS

Our results suggest that BMP-6 CpG island hypermethylation leads to decreased BMP-6 expression in HCC tissues.

Functional domains of androgen receptor coactivator p44/Mep50/WDR77and its interaction with Smad1

p44/MEP50/WDR77 has been identified as a coactivator of androgen receptor (AR), with distinct growth suppression and promotion function in gender specific endocrine organs and their malignancies. We dissected the functional domains of p44 for protein interaction with transcription factors, transcriptional activation, as well as the functional domains in p44 related to its growth inhibition in prostate cancer. Using a yeast two-hybrid screen, we identified a novel transcription complex AR-p44-Smad1, confirmed for physical interaction by co-immunoprecipitaion and functional interaction with luciferase assays in human prostate cancer cells. Yeast two-hybrid assay revealed that the N-terminal region of p44, instead of the traditional WD40 domain at the C-terminus, mediates the interaction among p44, N-terminus of AR and full length Smad1. Although both N and C terminal domains of p44 are necessary for maximum AR transcriptional activation, the N terminal fragment of p44 alone maintains the basic effect on AR transcriptional activation. Cell proliferation assays with N- and C- terminal deletion mutations indicated that the central portion of p44 is required for nuclear p44 mediated prostate cancer growth inhibition.

BMP4 reverses multidrug resistance through modulation of BCL-2 and GDNF in glioblastoma

Patients with glioblastoma are commonly treated with chemotherapy. But a significant proportion of patients develop disease progression after an initial response to chemotherapy. Presently, there is no standard of care for such patients. The bone morphogenetic protein 4 (BMP4) has been reported to play a tumor-suppressing role in glioblastoma, but its role in glioblastoma multidrug resistance (MDR) is not clear. We reported that BMP4 can reverse MDR of glioblastoma through the inhibition of B-cell lymphoma 2(BCL-2) and glial cell derived neurotrophic factor (GDNF). We showed that the expression level of BMP4 was lower in glioblastoma compared to normal brain tissue, and also showed that BMP4 expression decreased in multidrug resistance cell line U251/TMZ compared to U251 cells. Our research demonstrated that over-expression of BMP4 can reverse the multidrug resistance. BCL-2 and GDNF were inhibited when BMP4 was over-expressed, and this data were consistent with the negative relationship in human samples; analysis of 40 patient's glioblastoma and brain samples revealed a significant negative correlation between BMP4 and BCL-2, GDNF. When BCL-2 and GDNF were knocked down, the effect of BMP4 in regulating MDR was partially lost. This novel result showed, for the first time, that BMP4 can reverse MDR in glioblastoma, which involved negative inhibition of BCL-2 and GDNF.

Bone morphogenetic protein 4 expression in multiple normal and tumor tissues reveals its importance beyond development

Bone morphogenetic proteins (BMPs) are extracellular signaling molecules that belong to the transforming growth factor β (TGFβ) superfamily and are known to regulate cell proliferation, differentiation and motility, especially during development. BMP4 has an indispensable role in vertebrate development while limited information on BMP4 expression and function exists in adult tissues. Nevertheless, its contribution to cancer development and progression has gained increasing interest in recent years. Functional studies, especially in breast cancer, have implicated BMP4 both in inhibition of cell proliferation and in promotion of cell migration and invasion. To gain an insight into the function of BMP4 in normal and cancer tissues, BMP4 protein expression levels were analyzed by immunohistochemistry in 34 different normal organs/tissues, 34 different tumor types and finally in 486 breast cancer samples where possible associations between BMP4 and clinicopathological parameters were statistically evaluated. In over 20% of normal and malignant tissues, BMP4 was expressed at high level. Strong expression was observed particularly in some normal epithelial cells, such as bladder and stomach, and in squamous cell carcinomas. In breast cancer, strong BMP4 expression was detected in 25% of patients, and was associated with low proliferation index and increased frequency of tumor recurrence. Taken together, BMP4 is expressed in a subset of normal adult tissues and is likely to contribute to tissue homeostasis. However, in tumors, BMP4 expression levels vary considerably, implying diverse roles in different tumor types. This role is biphasic in breast cancer as BMP4 expression is linked to reduced proliferation and increased recurrence, thus corroborating our previous in-vitro functional data.

Genetic variants in CASP3, BMP5, and IRS2 genes may influence survival in prostate cancer patients receiving androgen-deprivation therapy

Several genome-wide association studies (GWAS) have been conducted to identify the common single nucleotide polymorphisms (SNPs) that influence the risk of prostate cancer. It was hypothesized that some prostate cancer-associated SNPs might relate to the clinical outcomes in patients treated for prostate cancer using androgen-deprivation therapy (ADT). A cohort of 601 patients who have received ADT for prostate cancer was genotyped for 29 SNPs that have been associated with prostate cancer in Cancer Genetic Markers of Susceptibility GWAS, and within the genes that have been implicated in cancer. Prognostic significance of these SNPs on the disease progression, prostate cancer-specific mortality (PCSM) and all-cause mortality (ACM) after ADT were assessed by Kaplan-Meier analysis and Cox regression model. Three SNPs, namely CASP3 rs4862396, BMP5 rs3734444 and IRS2 rs7986346, were found to be closely associated with the ACM (P≤0.042), and BMP5 rs3734444 and IRS2 rs7986346 were also noted to be significantly related to the PCSM (P≤0.032) after adjusting for the known clinicopathologic predictors. Moreover, patients carrying a greater number of unfavorable genotypes at the loci of interest had a shorter time to ACM and PCSM during ADT (P for trend <0.001). Our results suggest that CASP3 rs4862396, BMP5 rs3734444 and IRS2 rs7986346 may affect the survival in patients after ADT for prostate cancer, and the analysis of these SNPs can help identify patients at higher risk of poor outcome.

Bone morphogenetic protein signaling: implications in urology

The bone morphogenetic proteins (BMPs), as members of the transforming growth factor-beta (TGF-beta) superfamily, not only control bone formation, but also regulate multiple key steps during embryonic development and differentiation. Furthermore, BMPs play critical roles in maintaining the homeostasis of the cardiovascular, pulmonary, reproductive, urogenital, and nervous systems in adult life. Like all members of the TGF-beta superfamily, BMP signaling is mediated through a heteromeric complex of type I and type II transmembrane serine/threonine kinase receptors. The subsequent signal transduction cascade includes either the canonical Smad-dependent or non-canonical Smad-independent pathways. Reflecting the critical function of BMPs, BMP signaling is tightly regulated at multiple steps by various mechanisms including extracellular endogenous antagonists, neutralizing antibodies/extracellular soluble receptor domains, small molecule inhibitors, cytoplasmic inhibitory Smads, and transcriptional co-repressors. Recently, dorsomorphin, the first small molecule inhibitor of BMP signaling, was identified and suggested as a useful tool for dissecting the mechanisms of signaling pathways and for developing novel therapeutics for diverse human diseases that are related to the BMP signaling pathways. In this article, we discuss various mechanisms involved in regulating BMP signaling pathways and their implications for urology.

The Yin and Yang of bone morphogenetic proteins in cancer

Bone morphogenetic proteins (BMPs) were first studied as growth factors or morphogens of the transforming growth factor-beta superfamily. These growth molecules, originally associated with bone and cartilage development, are now known to play an important role in morphogenesis and homeostasis in many other tissues. More recently, significant contributions from BMPs, their receptors, and interacting molecules have been linked to carcinogenesis and tumor progression. On the other hand, BMPs can sometimes function as a tumor suppressor. Our report highlights these new roles in the pathogenesis of cancer that may suggest novel targets for therapeutic intervention.

Post-treatment circulating plasma BMP6 mRNA and H3K27 methylation levels discriminate metastatic prostate cancer from localized disease

BACKGROUND

We evaluated the utility of post-treatment plasma levels of the circulating bone-morphogenetic protein-6-specific mRNA (cBMP6 mRNA), cell-free DNA (cf-DNA), apoptotic nucleosomes and Histone H3 lysine 27 trimethylation (H3K27me3), in discriminating metastatic prostate cancer (PCa) from organ confined, locally controlled disease.

METHODS

Peripheral blood was taken from the patients at the end of therapy, and quantitative PCR was performed to amplify cBMP6 mRNA or cf-DNA from plasma while apoptotic nucleosomes and H3K27me3 were determined by ELISA-based approaches. Following blinded measurements, the markers were compared between the patients with local (n=22), local advanced (n=11) or metastatic disease (n=28).

RESULTS

Of the four markers investigated, the cBMP6 mRNA and H3K27me3 levels revealed significant differences between the three subgroups. We found higher levels of cBMP6 mRNA in the patients with metastases than in those with localized (p=0.001) or local advanced disease (p=0.05). When compared to cBMP6, H3K27me3 displayed an inverse distribution and was significantly lower in the patients with metastatic disease than in those with localized (p=0.05) or local advanced disease (p=0.024). There was no correlation between the different markers and total PSA levels or Gleason score at diagnosis.

CONCLUSION

Our study provides evidence that post-treatment analysis of cBMP6 mRNA and H3K27me3 may be used to distinguish metastatic PCa from organ confined, locally controlled disease.

The expression of osteoclastogenesis-associated factors and osteoblast response to osteolytic prostate cancer cells

BACKGROUND

Prostate cancer (PCa) has a propensity to metastasize to bone. Tumor cells replace bone marrow and can elicit an osteoblastic, osteolytic, or mixed bone response. Our objective was to elucidate the mechanisms and key factors involved in promoting osteoclastogenesis in PCa bone metastasis.

METHODS

We cultured osteoblast-like MC3T3-E1 cells with conditioned medium (CM) from PC-3 and C4-2B cells. MC3T3-E1 mineralization decreased in the presence of PC-3 CM, whereas C4-2B CM had no effect on mineralization. Using oligo arrays and validating by real-time PCR, we observed a decrease in the expression of mineralization-associated genes in MC3T3-E1 cells grown in the presence of PC-3 CM. In addition, PC-3 CM induced the expression of osteoclastogenesis-associated genes IGFBP-5, IL-6, MCP-1, and RANKL while decreasing OPG expression in MC3T3-E1 cells. Furthermore, CM from MC3T3-E1 cells cultured in the presence of PC-3 CM, in association with soluble RANKL, increased osteoclastogenesis in RAW 264.7 cells. Investigation of PCa metastases and xenografts by immunohistochemistry revealed that the osteoclastic factor IL-6 was expressed in the majority of PCa bone metastases and to a lesser extent in PCa soft tissue metastases. In vitro it was determined that soluble IL-6R (sIL-6R) was necessary for IL-6 to inhibit mineralization in MC3T3-E1 cells.

RESULTS

PC-3 cells inhibit osteoblast activity and induce osteoblasts to produce osteoclastic factors that promote osteoclastogenesis, and one of these factors, IL-6, is highly expressed in PCa bone metastases.

CONCLUSIONS

IL-6 may have an important role in promoting osteoclastogenesis in PCa bone metastasis through its' interaction with sIL-6R.

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.

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.

The induction of endochondral bone formation by transforming growth factor-beta(3): experimental studies in the non-human primate Papio ursinus

Transforming growth factor-β₃ (TGF-β₃), a multi-functional growth modulator of embryonic development, tissue repair and morphogenesis, immunoregulation, fibrosis, angiogenesis and carcinogenesis, is the third mammalian isoform of the TGF-β subfamily of proteins. The pleiotropism of the signalling proteins of the TGF-β superfamily, including the TGF-β proteins per se, are highlighted by the apparent redundancy of soluble molecular signals initiating de novo endochondral bone induction in the primate only. In the heterotopic bioassay for bone induction in the subcutaneous site of rodents, the TGF-β₃ isoform does not initiate endochondral bone formation. Strikingly and in marked contrast to the rodent bioassay, recombinant human (h)TGF-β₃, when implanted in the rectus abdominis muscle of adult non-human primates Papio ursinus at doses of 5, 25 and 125 μg per 100 mg of insoluble collagenous matrix as carrier, induces rapid endochondral bone formation resulting in large corticalized ossicles by day 30 and 90. In the same animals, the delivery of identical or higher doses of theTGF-β₃ protein results in minimal repair of calvarial defects on day 30 with limited bone regeneration across the pericranial aspect of the defects on day 90. Partial restoration of the bone induction cascade by the hTGF-β₃ protein is obtained by mixing the hTGF-β₃ device with minced fragments of autogenous rectus abdominis muscle thus adding responding stem cells for further bone induction by the hTGF-β₃ protein. The observed limited bone induction in hTGF-β₃/treated and untreated calvarial defects in Papio ursinus and therefore by extension to Homo sapiens, is due to the influence of Smad-6 and Smad-7 down-stream antagonists of the TGF-β signalling pathway. RT-PCR, Western and Northern blot analyses of tissue specimens generated by the TGF-β₃ isoform demonstrate robust expression of Smad-6 and Smad-7 in orthotopic calvarial sites with limited expression in heterotopic rectus abdominis sites. Smad-6 and -7 overexpression in hTGF-β₃/treated and untreated calvarial defects may be due to the vascular endothelial tissue of the arachnoids expressing signalling proteins modulating the expression of the inhibitory Smads in pre-osteoblastic and osteoblastic calvarial cell lines controlling the induction of bone in the primate calvarium.

Prostate cancer induces bone metastasis through Wnt-induced bone morphogenetic protein-dependent and independent mechanisms

Prostate cancer (PCa) is frequently accompanied by osteosclerotic (i.e., excessive bone production) bone metastases. Although bone morphogenetic proteins (BMP) and Wnts are mediators of PCa-induced osteoblastic activity, the relation between them in PCa bone metastases is unknown. The goal of this study was to define this relationship. Wnt3a and Wnt5a administration or knockdown of DKK-1, a Wnt inhibitor, induced BMP-4 and 6 expression and promoter activation in PCa cells. DKK-1 blocked Wnt activation of the BMP promoters. Transfection of C4-2B cells with axin, an inhibitor of canonical Wnt signaling, blocked Wnt3a but not Wnt5a induction of the BMP promoters. In contrast, Jnk inhibitor I blocked Wnt5a but not Wnt3a induction of the BMP promoters. Wnt3a, Wnt5a, and conditioned medium (CM) from C4-2B or LuCaP23.1 cells induced osteoblast differentiation in vitro. The addition of DKK-1 and Noggin, a BMP inhibitor, to CM diminished PCa CM-induced osteoblast differentiation in a synergistic fashion. However, pretreatment of PCa cells with DKK-1 before collecting CM blocked osteoblast differentiation, whereas pretreatment with Noggin only partially reduced osteoblast differentiation, and pretreatment with both DKK-1 and Noggin had no greater effect than pretreatment with DKK-1 alone. Additionally, knockdown of BMP expression in C4-2B cells inhibited Wnt-induced osteoblastic activity. These results show that PCa promotes osteoblast differentiation through canonical and noncanonical Wnt signaling pathways that stimulate both BMP-dependent and BMP-independent osteoblast differentiation. These results show a clear link between Wnts and BMPs in PCa-induced osteoblast differentiation and provide novel targets, including the noncanonical Wnt pathway, for therapy of PCa.

BMP-6 over-expression in prostate cancer is associated with increased Id-1 protein and a more invasive phenotype

Bone morphogenetic protein-6 (BMP-6) has been strongly implicated in prostate cancer development and bone metastasis. Our previous data showed that BMP-6 mRNA was absent in patients with benign prostatic hyperplasia, but evident in primary tumours with established secondary skeletal metastases. To examine the role of BMP-6 in prostate cancer progression, we have developed a BMP-6-regulatable, doxycycline-inducible gene expression system. BMP-6 induction by doxycycline addition led to increased levels of BMP-6 RNA and protein, associated with nuclear translocation of SMADs and activation of the downstream target gene Id-1. BMP-6 protein did not enhance the proliferation rate of PC3M cells but did significantly increase the rate of migration and invasion in both PC3M and DU145 cells. Increased metalloproteinase (MMP-1 and MMP-9) mRNA levels were also observed following BMP-6 induction. Luciferase reporter assays confirmed BMP-6-mediated activation of MMP-1 and MMP-9 promoters, indicating direct transcriptional activation of MMPs by BMP-6. BMP-6 stimulation also led to an increase in phosphorylation levels of MAPK proteins. We next examined the effects of BMP-6 on the downstream gene Id-1 in a cohort of prostate cancer patients. A tissue microarray (TMA) was constructed and samples stained for BMP-6 and Id-1 expression. We observed a significant increase in the intensity of staining of epithelial BMP-6 in the cancer cases compared to the benign cases (Mann-Whitney U test, p < 0.0005) and in the intensity of staining of epithelial Id-1 in the cancer cases compared to the benign cases (Mann-Whitney U test, p = 0.015). We further observed a significant positive correlation between epithelial staining for Id-1 and BMP-6 (p = 0.001) across all samples for both benign and cancer cases. These data demonstrate that BMP-6 promotes migration and invasion of prostate cancer cells, potentially through activation of Id-1 and MMP activation.

HGF/SF up-regulates the expression of bone morphogenetic protein 7 in prostate cancer cells

Both HGF and BMP-7 have been implicated in the prostate cancer, particularly in bone metastasis. We recently demonstrated an up-regulation of BMP receptors by HGF in prostate cancer cells. Whether HGF has an effect on BMP-7 is still unknown. In the current study, we investigated the effects of HGF on the expression of BMP-7 in prostate cancer cells. Human prostate cancer cells, PC-3 and DU-145, were exposed to HGF at different concentrations for up to 24 hours. The mRNA levels of BMP7 were detected using RT-PCR and Quantitative PCR, and protein levels using Western blotting and immunocytochemistry. The levels of the BMP-7 transcripts in both PC-3 and DU-145 cells were up-regulated by the treatment with HGF in a concentration dependent and time related manner. The rise in BMP-7 mRNA was accompanied by an increase in protein levels, an effect completely blocked by the HGF antagonist, NK4. We further assessed this effect in an in vivo murine tumor model and showed that HGF up-regulated BMP-7 in prostate tumors. The antagonist of HGF, NK4 similarly blocked the induction of BMP-7 by HGF under the in vivo conditions. Taken together, HGF/SF can regulate BMP-7 expression in prostate cancer cells, both in vitro and in vivo. It may have a significant influence on the progression of prostate cancer and/or the development of bone metastasis.

Tumor metastasis to bone

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

Bone morphogenic factor gene dosage abnormalities in prostatic intraepithelial neoplasia and prostate cancer

Abnormal expression of bone morphogenic proteins (BMP) has been reported in prostate cancer as compared to benign prostatic tissue. Since aberrations in gene expression often result from alterations in gene copy number, we have investigated this possibility in patients with early prostate cancer. Probes for fluorescence in situ hybridization for the BMP, BMP5, BMP7, and UC28 gene loci were developed and applied to archival sections with areas of adjacent benign epithelium, high-grade prostatic intraepithelial neoplasia, and prostate carcinoma. Two hundred nuclei from each region were evaluated. No deletions of the gene loci examined were observed, but gain of BMP2, BMP5, BMP7, and UC28 occurred in 58, 50, 50, and 67% of tumor foci, respectively. These aberrations in copy number may be caused by early events in tumor development because they were also present in 10-30% of high-grade prostatic intraepithelial hyperplasia foci. In addition, one tumor demonstrated a tandem amplification of the UC28 gene locus. Approximately half of the prostate tumors displayed increased copy numbers of the BMP2, BMP5, BMP7, and UC28 gene loci, which may account for their abnormal gene expression patterns in neoplastic prostate tissue.

Bone metabolism and new targets for intervention

Bone metastasis is a common complication of prostate cancer and is associated with significant morbidity for patients. Bone metabolism and prostate cancer metastasis to bone are complex processes. The interactions between host cells and metastatic prostate cancer cells are important components of organ-specific cancer progression. In addition to traditional treatment approaches, targeted therapy is currently becoming more popular. Bone metabolism, metastatic processes of prostate cancer, and the targeting of treatment for advanced disease are discussed here.

Control of prostate cell growth: BMP antagonizes androgen mitogenic activity with incorporation of MAPK signals in Smad1

Alterations in the signaling pathways of bone morphogenetic proteins (BMPs) and activation of the ERK/MAP kinase (MAPK) pathway by growth factors have been implicated in the development and progression of prostate cancer. Smad1 acts as a substrate for MAPKs and also performs a central role in transmitting signals from BMPs. We found that BMPs/Smad1 signaling inhibits the growth of androgen-sensitive prostate cancer cells. Upon the incorporation of ERK/MAPK signals at its linker region, Smad1 physically interacts with androgen-activated androgen receptor (AR) and suppresses its functions. BMPs induce the function of Smad1 as an AR transcriptional corepressor. We demonstrated in vivo that Smad1 signaling is low in androgen-regulated growth of prostate cancer, is activated after castration, and also is decreased in hormone-independent tumors. The activation status of ERK/MAPK parallels Smad1 in the progression of prostate cancer; thus, our findings indicate a molecular basis for the integration of signals of MAPK and Smad1 in the progression and androgen regulation of prostate cancer.

Prostate-specific antigen induces apoptosis of osteoclast precursors: potential role in osteoblastic bone metastases of prostate cancer

BACKGROUND

Prostate cancer is frequently associated with bone metastases with marked osteoblastic changes and low osteoclastic activity but its mechanism is not well understood. We previously reported that prostate-specific antigen (PSA) stimulated the proliferation and the activation of osteoblasts. In this study, we investigated the effect of PSA on osteoclastogenesis.

METHODS

Two human prostate cancer cell lines and PSA were directly injected into human adult bone (HAB) implanted into NOD/SCID mice, followed by morphological analysis. RAW 264.7 cells, murine osteoclast precursor, were treated with PSA.

RESULTS

PSA-producing LNCaP and PSA caused a significant decrease of osteoclast precursors and osteoclasts in HAB accompanied by osteoblast proliferation and new bone formation, while PSA-nonproducing PC3 showed increasing osteoclasts with osteolysis. PSA induced apoptosis of RAW 264.7 cells in vitro. PSA-induced apoptosis was dependent of enzymatic activity of PSA and was specific to immature tartrate-resistant acid phosphatase-negative mononuclear RAW 264.7 cells.

CONCLUSIONS

PSA plays a crucial role for osteoblastic bone metastasis by promoting both osteoblasts proliferation and apoptosis of osteoclast precursors.

The metastatic cascade in prostate cancer

Morbidity and mortality due to prostate cancer are mainly a result of prostate cancer metastases. After the initial neoplastic transformation of cells, the process of metastasis involves a series of sequential steps, which involve neoangiogenesis and lymphangiogenesis, loss of adhesion with migration away from the primary tumour and entry into the systemic vasculature or lymphatics. Metastatic growth in sites such as lymph nodes and bone marrow then involves the specific non-random homing of prostate cancer cells. An appreciation and understanding of this metastatic cascade in relation to prostate cancer is clinically important in order to stratify men with prostate cancer into prognostic groups. Moreover, it is crucial in the future development of therapies that can prevent metastases.

Bone morphogenetic protein-2 promotes the haptotactic migration of murine osteoblastic and osteosarcoma cells by enhancing incorporation of integrin beta1 into lipid rafts

Cell migration is essential for both organogenesis and tumor progression. Bone morphogenetic proteins (BMPs) are reported to be critical for not only bone formation but also tumor invasion. Here, we found that treatment with recombinant human BMP-2 (rhBMP-2) enhanced the haptotactic response of murine osteoblastic MC3T3-E1 and osteosarcoma Dunn cells to various extracellular matrix (ECM) components, including fibronectin, type I collagen, and laminin-1. Function-blocking antibody against integrin alpha5beta1 partially inhibited haptotaxis to fibronectin, suggesting that the response was propagated via these integrins. rhBMP-2 slightly increased the expression level of integrin beta1, and enhanced the speed of cell spreading on fibronectin, focal adhesion formation and phosphorylation of focal adhesion kinase (FAK) at Tyr397. By means of sucrose gradient flotation, incorporation of integrin beta1 in fractions of detergent (CHAPS) resistant membrane was increased when the cells were treated with rhBMP-2. Further, treatment with methyl-beta-cyclodextrin to deplete membrane cholesterol abrogated the effect of rhBMP-2 on haptotaxis, and exogenously added cholesterol reversed this inhibitory effect. Collectively, these results provide insights into the mechanism by which BMP signaling enhances cell migration by modulating fibronectin-integrin beta1 signaling via cholesterol enriched membrane microdomains, lipid rafts.

Vascular endothelial growth factor contributes to prostate cancer-mediated osteoblastic activity

Prostate cancer frequently metastasizes to bone resulting in the formation of osteoblastic metastases through unknown mechanisms. Vascular endothelial growth factor (VEGF) has been shown recently to promote osteoblast activity. Accordingly, we tested if VEGF contributes to the ability of prostate cancer to induce osteoblast activity. PC-3, LNCaP, and C4-2B prostate cancer cell lines expressed both VEGF-165 and VEGF-189 mRNA isoforms and VEGF protein. Prostate cancer cells expressed the mRNA for VEGF receptor (VEGFR) neuropilin-1 but not the VEGFRs Flt-1 or KDR. In contrast, mouse pre-osteoblastic cells (MC3T3-E1) expressed Flt-1 and neuropilin-1 mRNA but not KDR. PTK787, a VEGFR tyrosine kinase inhibitor, inhibited the proliferation of human microvascular endothelial cells but not prostate cancer proliferation in vitro. C4-2B conditioned medium induced osteoblast differentiation as measured by production of alkaline phosphatase and osteocalcin and mineralization of MC3T3-E1. PTK787 blocked the C4-2B conditioned medium-induced osteoblastic activity. VEGF directly induced alkaline phosphatase and osteocalcin but not mineralization of MC3T3-E1. These results suggest that VEGF induces initial differentiation of osteoblasts but requires other factors, present in C4-2B, to induce mineralization. To determine if VEGF influences the ability of prostate cancer to develop osteoblastic lesions, we injected C4-2B cells into the tibia of mice and, after the tumors grew for 6 weeks, administered PTK787 for 4 weeks. PTK787 decreased both intratibial tumor burden and C4-2B-induced osteoblastic activity as measured by bone mineral density and serum osteocalcin. These results show that VEGF contributes to prostate cancer-induced osteoblastic activity in vivo.

Bone morphogenetic protein-6 promotes osteoblastic prostate cancer bone metastases through a dual mechanism

Prostate cancer frequently metastasizes to bone where it forms osteoblastic lesions through unknown mechanisms. Bone morphogenetic proteins (BMP) are mediators of skeletal formation. Prostate cancer produces a variety of BMPs, including BMP-6. We tested the hypothesis that BMP-6 contributes to prostate cancer-induced osteosclerosis at bone metastatic sites. Prostate cancer cells and clinical tissues produced BMP-6 that increased with aggressiveness of the tumor. Prostate cancer-conditioned medium induced SMAD phosphorylation in the preosteoblast MC3T3 cells, and phosphorylation was diminished by anti-BMP-6 antibody. Prostate cancer-conditioned medium induced mineralization of MC3T3 cells, which was blocked by both the BMP inhibitor noggin and anti-BMP-6. Human fetal bones were implanted in severe combined immunodeficient mice and after 4 weeks, LuCaP 23.1 prostate cancer cells were injected both s.c. and into the bone implants. Anti-BMP-6 or isotype antibody administration was then initiated. Anti-BMP-6 reduced LuCaP 23.1-induced osteoblastic activity, but had no effect on its osteolytic activity. This was associated with increased osteoblast numbers and osteoblast activity based on bone histomorphometric evaluation. As endothelin-1 has been implicated in bone metastases, we measured serum endothelin-1 levels but found they were not different among the treatment groups. In addition to decreased bone production, anti-BMP-6 reduced intraosseous, but not s.c., tumor size. We found that BMP-2, BMP-4, BMP-6, and BMP-7 had no direct effect on prostate cancer cell growth, but BMP-2 and BMP-6 increased the in vitro invasive ability of prostate cancer cell. These data show that prostate cancer promotes osteoblastic activity through BMP-6 and that, in addition to its bone effects, suggest that BMPs promote the ability of the prostate cancer cells to invade the bone microenvironment.

Bone morphogenetic protein 2 (BMP-2) and induction of tumor angiogenesis

PURPOSE

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta family and play an important role in the regulation of embryonic vasculogenesis but their role in postnatal angiogenesis remains to be clarified. In this study we investigated a possible role of BMP-2 in the promotion of tumor angiogenesis.

METHODS

We studied the effect of BMP-2 on human dermal microvascular endothelial cells (HDMECs) and examined a possible angiogenic activity of BMP-2 with the mouse sponge assay. The effect of BMP-2 overexpression on tumor vascularization was also analyzed in xenografts of human BMP-2 transfected MCF-7 breast cancer cells (MCF-7/BMP2) in mice.

RESULTS

BMP receptor activation selectively induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) in contrast to the ERK1/2 MAP kinases. In keeping with this finding, BMP-2 had no significant effect on endothelial cell proliferation but promoted HDMEC tube formation in the matrigel assay. The transcription factor inhibitor of differentiation 1 (Id1), which is known to play an important role in neovascularization of tumors, was confirmed as a BMP target in HDMECs. Immunohistochemical analysis of sponge sections revealed that BMP-2 induced vascularization and showed an additive enhancement of angiogenesis with VEGF. In the murine breast cancer xenograft model, human MCF-7 cells with stable overexpression of BMP-2 developed vascularized tumors while empty vector control MCF-7 cells failed to form tumors.

CONCLUSIONS

We conclude that activation of the BMP pathway by BMP-2 can promote vascularization and might be involved in tumor angiogenesis possibly by stimulating the Id1 and p38 MAPK pathway.

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.