Expression of bone morphogenetic protein 6 in normal mammary tissue and breast cancer cell lines and its regulation by epidermal growth factor

Identification of biomarkers associated with the invasion of nonfunctional pituitary neuroendocrine tumors based on the immune microenvironment

Introduction

The invasive behavior of nonfunctioning pituitary neuroendocrine tumors (NF-PitNEts) affects complete resection and indicates a poor prognosis. Cancer immunotherapy has been experimentally used for the treatment of many tumors, including pituitary tumors. The current study aimed to screen the key immune-related genes in NF-PitNEts with invasion.

Methods

We used two cohorts to explore novel biomarkers in NF-PitNEts. The immune infiltration-associated differentially expressed genes (DEGs) were obtained based on high/low immune scores, which were calculated through the ESTIMATE algorithm. The abundance of immune cells was predicted using the ImmuCellAI database. WGCNA was used to construct a coexpression network of immune cell-related genes. Random forest analysis was used to select the candidate genes associated with invasion. The expression of key genes was verified in external validation set using quantitative real-time polymerase chain reaction (qRT‒PCR).

Results

The immune and invasion related DEGs was obtained based on the first dataset of NF-PitNEts (n=112). The immune cell-associated modules in NF-PitNEts were calculate by WGCNA. Random forest analysis was performed on 81 common genes intersected by immune-related genes, invasion-related genes, and module genes. Then, 20 of these genes with the highest RF score were selected to construct the invasion and immune-associated classification model. We found that this model had high prediction accuracy for tumor invasion, which had the largest area under the receiver operating characteristic curve (AUC) value in the training dataset from the first dataset (n=78), the self-test dataset from the first dataset (n=34), and the independent test dataset (n=73) (AUC=0.732/0.653/0.619). Functional enrichment analysis revealed that 8 out of the 20 genes were enriched in multiple signaling pathways. Subsequently, the 8-gene (BMP6, CIB2, FABP5, HOMER2, MAML3, NIN, PRKG2 and SIDT2) classification model was constructed and showed good efficiency in the first dataset (AUC=0.671). In addition, the expression levels of these 8 genes were verified by qRT‒PCR.

Conclusion

We identified eight key genes associated with invasion and immunity in NF-PitNEts that may play a fundamental role in invasive progression and may provide novel potential immunotherapy targets for NF-PitNEts.

Expression of genes related to iron homeostasis in breast cancer

BACKGROUND

The dysfunctions in the metabolism of iron have an important role in many pathological conditions, ranging from disease with iron deposition to cancer. Studies on malignant diseases of the breast reported irregular expression in genes associated with iron metabolism. The variations are related to findings that have prognostic significance. This study evaluated the relationship of the expression levels of transferrin receptor 1 (TFRC), iron regulatory protein 1 (IRP1), hepcidin (HAMP), ferroportin 1 (FPN1), hemojuvelin (HFE2), matriptase 2 (TMPRSS6), and miR-122 genes in the normal and malignant tissues of breast cancer patients.

METHODS & RESULTS

The normal and malignant tissues from 75 women with breast malignancies were used in this study. The patients did not receive any treatment previously. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used in figuring the levels of gene expression associated with iron metabolism. When the malignant and normal tissues gene expression levels were analyzed, expression of TFRC increased (1.586-fold); IRP1 (0.594 fold) and miR-122 (0.320 fold) expression decreased; HAMP, FPN1, HFE2, and TMPRSS6 expressions did not change. FPN1 and IRP1 had a positive association, and this association was statistically significant (r = 0.266; p = 0.022). IRP1 and miR-122 had a positive association, and this association had statistical significance (r = 0.231; p = 0.048).

CONCLUSIONS

Our study portrayed the important association between genes involved in iron hemostasis and breast malignancy. The results could be used to establish new diagnostic techniques in the management of breast malignancies. The alterations in the metabolism of malignant breast cells with normal breast cells could be utilized to achieve advantages in treatment.

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.

An investigation of the relationship between TMPRSS6 gene expression, genetic variants and clinical findings in breast cancer

Breast cancer is one of the most common types of cancer among women worldwide. The TMPRSS6 (Transmembrane Serine Protease 6) gene encodes matriptase-2, which plays an important role in iron hemostasis as the hepcidin regulator and may play a role in breast cancer susceptibility. In this study, we examined the expression levels of the TMPRSS6 gene in healthy tissues and tumor tissues of breast cancer patients; and the relationship between these levels and pathological findings. The relationship between TMPRSS6 polymorphisms (rs733655, rs5756506, rs2413450, rs855791, rs2235324, rs4820268) and patients' hematological parameters. The gene expression study encompassed 47 breast cancer patients and the gene polymorphism study consisted of 181 breast cancer patients and 100 healthy controls. Gene expression analysis was performed by qRT-PCR. The genotyping of TMPRSS6 polymorphisms was performed by RT-PCR. TMPRSS6 gene expression levels in tumor tissues were found to be 1.88 times higher than the expression levels in the control tissues. We examined the relationship between TMPRSS6 gene expression levels and pathological data, statistically significant relationship was found between patient's estrogen receptor (ER) and HER2 findings and TMPRSS6 gene expression (respectively p = 0.02, p = 0.002). When the relationship between TMPRSS6 gene polymorphisms related genotypes distributions and hematological findings was investigated, a significant relationship was identified between mean corpuscular hemoglobin concentration (MCHC) parameter and the polymorphism of only the rs733655. According to our findings, the increase in TMPRSS6 gene expression in cancerous tissues shows that matriptase-2 may be effective in the cancer process. Thus TMPRSS6 gene polymorphisms may affect the disease process by affecting the blood parameters of patients.

Bone morphogenetic proteins mediate crosstalk between cancer cells and the tumour microenvironment at primary tumours and metastases (Review)

Bone morphogenetic proteins (BMP) are pluripotent molecules, co‑ordinating cellular functions from early embryonic and postnatal development to tissue repair, regeneration and homeostasis. They are also involved in tumourigenesis, disease progression and the metastasis of various solid tumours. Emerging evidence has indicated that BMPs are able to promote disease progression and metastasis by orchestrating communication between cancer cells and the surrounding microenvironment. The interactions occur between BMPs and epidermal growth factor receptor, hepatocyte growth factor, fibroblast growth factor, vascular endothelial growth factor and extracellular matrix components. Overall, these interactions co‑ordinate the cellular functions of tumour cells and other types of cell in the tumour to promote the growth of the primary tumour, local invasion, angiogenesis and metastasis, and the establishment and survival of cancer cells in the metastatic niche. Therefore, the present study aimed to provide an informative summary of the involvement of BMPs in the tumour microenvironment.

MiR-223-3p targeting epithelial cell transforming sequence 2 oncogene inhibits the activity, apoptosis, invasion and migration of MDA-MB-468 breast cancer cells

Purpose

This research was to investigate the role of miR-223-3p targeting epithelial cell transforming sequence 2 oncogene (ECT2) in activity, apoptosis, invasion and migration of MDA-MB-468 breast cancer (BC) cells.

Methods

The human BC cell lines MDA-MB-468 were used for the experiment. They were divided into six groups: blank group (no plasmid transfection), NC group (negative control, transfected empty plasmid), miR-223-3p mimic group (transfected miR-223-3p mimic plasmid), miR-223-3p inhibitor group (transfected miR-223-3p inhibitor plasmid), si-ECT2 group (transfected si ECT2 plasmid) and miR-223-3p mimic+oe-ECT2 group (transfected with miR-223-3p mimic plasmid and ECT2 plasmid).

Results

Compared with the NC group, the mRNA and protein expression of Bax in miR-223-3p mimic and si-ECT2 groups were significantly increased, while the mRNA and protein expression of ECT2, Bcl-2, vascular endothelial growth factor (VEGF), and TGF-β1 were significantly decreased (all P<0.05). Compared with the NC group, the expression of miR-223-3p and the mRNA and protein expression of Bax were significantly decreased in the miR-223-3p inhibitor group, while the mRNA and protein expression of ECT2, Bcl-2, VEGF and TGF-β1 were significantly increased (both P<0.05). Compared with the single processing group, the mRNA and protein expression of Bax in the miR-223-3p mimic+si-ECT2 group were significantly increased, while the mRNA and protein expression of ECT2, Bcl-2, VEGF, and TGF-β1 were significantly decreased (all P<0.05).

Conclusion

MiR-223-3p targets and inhibits the expression of ECT2, thus inhibiting the invasion and migration of BC cells, and promoting cell apoptosis. miR-223-3p plays a protective role in BC.

Expression of bone morphogenetic protein 6 in non-small cell lung cancer and its significance

The present study investigated the expression and clinical significance of bone morphogenetic protein 6 (BMP-6) in patients with non-small cell lung cancer (NSCLC). The tumor and adjacent normal lung tissues were harvested from 65 patients with NSCLC. BMP-6 mRNA expression was measured by reverse transcription-quantitative polymerase chain reaction, while protein expression was measured using immunohistochemistry or an ELISA. Cell viability was determined using Cell Counting Kit-8. The association of BMP-6 mRNA expression with the prognosis of patients with NSCLC was analyzed using the Kaplan-Meier plotter database. BMP-6 mRNA expression in NSCLC tumor tissues was significantly reduced, compared with the adjacent normal lung tissues (P<0.001), yet no significant differences were observed between patients with different clinicopathological features (P>0.05). The expression level of BMP-6 protein in NSCLC tumor tissues was significantly reduced, compared with the adjacent normal lung tissues (P<0.05). Analysis with the Kaplan-Meier plotter database revealed that patients with NSCLC with low BMP-6 mRNA expression had a reduced overall survival rate (P<0.01). The active BMP6 protein significantly inhibited cell proliferation in H460, H1299, A549 and H520 cells. In conclusion, BMP-6 is a tumor suppressor in lung cancer and loss of BMP-6 expression is significantly associated with a poor prognosis in patients with NSCLC.

Bone morphogenetic proteins, breast cancer, and bone metastases: striking the right balance

Bone morphogenetic proteins (BMPs) belong to the TGF-β super family, and are essential for the regulation of foetal development, tissue differentiation and homeostasis and a multitude of cellular functions. Naturally, this has led to the exploration of aberrance in this highly regulated system as a key factor in tumourigenesis. Originally identified for their role in osteogenesis and bone turnover, attention has been turned to the potential role of BMPs in tumour metastases to, and progression within, the bone niche. This is particularly pertinent to breast cancer, which commonly metastasises to bone, and in which studies have revealed aberrations of both BMP expression and signalling, which correlate clinically with breast cancer progression. Ultimately a BMP profile could provide new prognostic disease markers. As the evidence suggests a role for BMPs in regulating breast tumour cellular function, in particular interactions with tumour stroma and the bone metastatic microenvironment, there may be novel therapeutic potential in targeting BMP signalling in breast cancer. This review provides an update on the current knowledge of BMP abnormalities and their implication in the development and progression of breast cancer, particularly in the disease-specific bone metastasis.

Key Factors in Breast Cancer Dissemination and Establishment at the Bone: Past, Present and Future Perspectives

Bone metastases associated with breast cancer remain a clinical challenge due to their associated morbidity, limited therapeutic intervention and lack of prognostic markers. With a continually evolving understanding of bone biology and its dynamic microenvironment, many potential new targets have been proposed. In this chapter, we discuss the roles of well-established bone markers and how their targeting, in addition to tumour-targeted therapies, might help in the prevention and treatment of bone metastases. There are a vast number of bone markers, of which one of the best-known families is the bone morphogenetic proteins (BMPs). This chapter focuses on their role in breast cancer-associated bone metastases, associated signalling pathways and the possibilities for potential therapeutic intervention. In addition, this chapter provides an update on the role receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG) play on breast cancer development and their subsequent influence during the homing and establishment of breast cancer-associated bone metastases. Beyond the well-established bone molecules, this chapter also explores the role of other potential factors such as activated leukocyte cell adhesion molecule (ALCAM) and its potential impact on breast cancer cells' affinity for the bone environment, which implies that ALCAM could be a promising therapeutic target.

Expression of Bone Morphogenetic Protein-6 and Bone Morphogenetic Protein Receptors in Myoepithelial Cells of Canine Mammary Gland Tumors

To study the ectopic chondrogenesis in canine mammary mixed tumors, the expression of bone morphogenetic protein-6 (BMP-6) and specific BMP receptors (BMPRs), BMPR-IA, BMPR-IB, and BMPR-II, was examined using immunohistochemical and immunoblot analysis in 39 canine mammary gland tumors. Immunohistochemically, BMP-6 and all three types of BMPRs were coexpressed in the myoepithelial cells and chondrocytes in six of eight benign mixed tumors. In complex adenomas, myoepithelial cells showed an expression pattern of BMP-6, BMPR-IA, and BMPR-II similar to those in benign mixed tumors, whereas immunoreactivity for BMPR-IB was very mild. The myoepithelial cells proliferating within the basement membrane showed more intense immunoreactivity for BMP-6 and all BMPRs as compared with those proliferating in the interstitial areas. Western blotting analysis revealed immunopositive bands at 40–45 kDa for BMP-6 in the samples from simple and complex adenomas and benign mixed tumors. The BMPR-IB-specific bands at 45 kDa were most detected in benign mixed tumors. Because among BMPRs, BMPR-IB is thought to be the major receptor for BMP-6 for primary chondrogenesis, these findings suggest that the expression of BMP and its receptors on the myoepithelial cells might play a role in the ectopic cartilage formation in canine mammary gland tumors, especially in benign mixed tumors.

A Molecular View of Pathological Microcalcification in Breast Cancer

Breast microcalcification is a potential diagnostic indicator for non-palpable breast cancers. Microcalcification type I (calcium oxalate) is restricted to benign tissue, whereas type II (calcium hydroxyapatite) occurs both in benign as well as in malignant lesions. Microcalcification is a pathological complication of the mammary gland. Over the past few decades, much attention has been paid to exploit this property, which forms the basis for advances in diagnostic procedures and imaging techniques. The mechanism of its formation is still poorly understood. Hence, in this paper, we have attempted to address the molecular mechanism of microcalcification in breast cancer. The central theme of this communication is "how a subpopulation of heterogeneous breast tumor cells attains an osteoblast-like phenotype, and what activities drive the process of pathophysiological microcalcification, especially at the invasive or infiltrating front of breast tumors". The role of bone morphogenetic proteins (BMPs) and tumor associated macrophages (TAMs) along with epithelial to mesenchymal transition (EMT) in manipulating this pathological process has been highlighted. Therefore, this review offers a novel insight into the mechanism underlying the development of microcalcification in breast carcinomas.

The integrative epigenomic-transcriptomic landscape of ER positive breast cancer

Background

While recent integrative analyses of copy number and gene expression data in breast cancer have revealed a complex molecular landscape with multiple subtypes and many oncogenic/tumour suppressor driver events, much less is known about the role of DNA methylation in shaping breast cancer taxonomy and defining driver events.

Results

Here, we applied a powerful integrative network algorithm to matched DNA methylation and RNA-Seq data for 724 estrogen receptor (ER)-positive (ER+) breast cancers and 111 normal adjacent tissue specimens from The Cancer Genome Atlas (TCGA) project, in order to identify putative epigenetic driver events and to explore the resulting molecular taxonomy. This revealed the existence of nine functionally deregulated epigenetic hotspots encompassing a total of 146 genes, which we were able to validate in independent data sets encompassing over 1000 ER+ breast cancers. Integrative clustering of the matched messenger RNA (mRNA) and DNA methylation data over these genes resulted in only two clusters, which correlated very strongly with the luminal-A and luminal B subtypes. Overall, luminal-A and luminal-B breast cancers shared the same epigenetically deregulated hotspots but with luminal-B cancers exhibiting increased aberrant DNA methylation patterns relative to normal tissue. We show that increased levels of DNA methylation and mRNA expression deviation from the normal state define a marker of poor prognosis. Our data further implicates epigenetic silencing of WNT signalling antagonists and bone morphogenetic proteins (BMP) as key events underlying both luminal subtypes but specially of luminal-B breast cancer. Finally, we show that DNA methylation changes within the identified epigenetic interactome hotspots do not exhibit mutually exclusive patterns within the same cancer sample, instead exhibiting coordinated changes within the sample.

Conclusions

Our results indicate that the integrative DNA methylation and transcriptomic landscape of ER+ breast cancer is surprisingly homogeneous, defining two main subtypes which strongly correlate with luminal-A/B subtype status. In particular, we identify WNT and BMP signalling as key epigenetically deregulated tumour suppressor pathways in luminal ER+ breast cancer, with increased deregulation seen in luminal-B breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0159-0) contains supplementary material, which is available to authorized users.

BMP-6 inhibits cell proliferation by targeting microRNA-192 in breast cancer

Although bone morphogenetic protein-6 (BMP-6) has been identified as a tumor suppressor associated with breast cancer differentiation and metastasis, the potential roles of BMP-6 in regulating cell cycle progression have not been fully examined. In the present study, we provide the novel finding that induction of BMP-6 in MDA-MB-231 breast cancer cells significantly inhibits cell proliferation by decreasing the number of cells in S phase of the cell cycle, resulting in inhibition of tumorigenesis in a nude mouse xenograft model. Further investigation indicated that BMP-6 up-regulates the expression of microRNA-192 (miR-192) in MDA-MB-231 cells. Elevated expression of miR-192 caused cell growth arrest, which is similar to the effect of BMP-6 induction. Importantly, depletion of endogenous miR-192 by miRNA inhibition significantly attenuated BMP-6-mediated repression of cell cycle progression. In breast cancer tissue, miR-192 expression is significantly down-regulated in tumor samples and positively correlates with the expression of BMP-6, demonstrating the inhibitory effect of BMP-6 on cell proliferation through miR-192 regulation. Additionally, using the RT(2) Profiler PCR Array, retinoblastoma 1 (RB1) was identified as a direct target of the BMP-6/miR-192 pathway in regulating cell proliferation in breast cancer. In conclusion, we have identified an important role for BMP-6/miR-192 signaling in the regulation of cell cycle progression in breast cancer. Furthermore, BMP-6/miR-192 was expressed at low levels in breast cancer specimens, indicating that this pathway might represent a promising therapeutic target for breast cancer treatment.

Network and data integration for biomarker signature discovery via network smoothed T-statistics

Predictive, stable and interpretable gene signatures are generally seen as an important step towards a better personalized medicine. During the last decade various methods have been proposed for that purpose. However, one important obstacle for making gene signatures a standard tool in clinics is the typical low reproducibility of signatures combined with the difficulty to achieve a clear biological interpretation. For that purpose in the last years there has been a growing interest in approaches that try to integrate information from molecular interaction networks. We here propose a technique that integrates network information as well as different kinds of experimental data (here exemplified by mRNA and miRNA expression) into one classifier. This is done by smoothing t-statistics of individual genes or miRNAs over the structure of a combined protein-protein interaction (PPI) and miRNA-target gene network. A permutation test is conducted to select features in a highly consistent manner, and subsequently a Support Vector Machine (SVM) classifier is trained. Compared to several other competing methods our algorithm reveals an overall better prediction performance for early versus late disease relapse and a higher signature stability. Moreover, obtained gene lists can be clearly associated to biological knowledge, such as known disease genes and KEGG pathways. We demonstrate that our data integration strategy can improve classification performance compared to using a single data source only. Our method, called stSVM, is available in R-package netClass on CRAN (http://cran.r-project.org).

The bone morphogenetic protein receptor-1A pathway is required for lactogenic differentiation of mammary epithelial cells in vitro

Bone morphogenetic proteins (BMPs) have been implicated in the control of proliferation, tissue formation, and differentiation. BMPs regulate the biology of stem and progenitor cells and can promote cellular differentiation, depending on the cell type and context. Although the BMP pathway is known to be involved in early embryonic development of the mammary gland via mesenchymal cells, its role in later epithelial cellular differentiation has not been examined. The majority of the mammary gland development occurs post-natal, and its final functional differentiation is characterized by the emergence of alveolar cells that produce milk proteins. Here, we tested the hypothesis that bone morphogenetic protein receptor 1A (BMPR1A) function was required for mammary epithelial cell differentiation. We found that the BMPR1A-SMAD1/5/8 pathway was predominantly active in undifferentiated mammary epithelial cells, compared with differentiated cells. Reduction of BMPR1A mRNA and protein, using short hairpin RNA, resulted in a reduction of SMAD1/5/8 phosphorylation in undifferentiated cells, indicating an impact on this pathway. When the expression of the BMPR1A gene knocked down in undifferentiated cells, this also prevented beta-casein production during differentiation of the mammary epithelial cells by lactogenic hormone stimulation. Addition of Noggin, a BMP antagonist, also prevented beta-casein expression. Together, this demonstrated that BMP-BMPR1A-SMAD1/5/8 signal transduction is required for beta-casein production, a marker of alveolar cell differentiation. This evidence functionally identifies BMPR1A as a potential new regulator of mammary epithelial alveolar cell differentiation.

BMP-6 inhibits MMP-9 expression by regulating heme oxygenase-1 in MCF-7 breast cancer cells

PURPOSE

BMP-6, which belongs to the TGF-β superfamily, is a multifunctional molecule with distinct abilities in embryogenesis and organogenesis. Our recent research has implied that BMP-6 may suppress breast cancer metastasis. In the present study, we extended to elucidate the molecular mechanism by which BMP-6 exerts its anti-tumorigenic effect.

METHODS

The Boyden chamber assay was used to examine the ability of BMP-6 and HO-1 in MCF-7 malignant progress. RT-PCR, western blot, luciferase assay, and quantitative CHIP were used to determine the potential mechanism and signaling pathways by which BMP-6 and HO-1 function as anti-metastatic factors in MCF-7 cells.

RESULTS

The Boyden chamber assay showed that BMP-6 inhibited the migration and invasion of MCF-7 cells, which effect was significantly deprived by knockdown of HO-1. We further demonstrated that BMP-6 treatment resulted in an activation of HO-1 transcription through the recruitment of Smad1/5 to the Smad-responsive element on its promoter. In addition, BMP-6-induced up-regulation of HO-1 exhibited an inhibitory effect on MMP-9 secretion in a paracrine action in MCF-7 cells. Overexpression of BMP-6 and HO-1 synergistically suppressed MMP-9 transcription, which effect was specifically mediated via the MAPK/p38/AP-1 signaling. However, blockade of HO-1 using ZnPPIX totally abolished BMP-6-regulated MMP-9 activation in MCF-7 cells.

CONCLUSIONS

These observations suggest a novel role of BMP-6/HO-1 cascade to relieve breast cancer metastasis by regulating the secretion of growth factors in tumor microenvironment.

Bone morphogenetic protein-10 (BMP-10) inhibits aggressiveness of breast cancer cells and correlates with poor prognosis in breast cancer

Our recent study showed that a novel member of bone morphogenetic protein (BMP) family, BMP-10, was decreased in prostate cancer. In the present study, we investigated the implication of BMP-10 in breast cancer, particularly the relation of its expression with clinical aspects. The expression of BMP-10 was examined in a cohort of human breast cancer specimens (normal, n = 23; cancer, n = 97), using both quantitative real-time PCR and immunohistochemical staining. The full-length human BMP-10 was cloned into a mammalian expression plasmid vector and then transfected into breast cancer cells. The effect on growth, cell matrix adhesion, motility, and invasion of MDA-MB-231 cells by BMP-10 was then investigated using in vitro growth assays. Immunohistochemical staining and quantitative real-time PCR revealed a decreased expression of BMP-10 in breast cancer. Further analysis of BMP-10 transcript level against the clinical aspect demonstrated that the decreased BMP-10 expression correlated with disease progression, bone metastasis, and poor prognosis. The disease-free survival of the patients with a higher level of BMP-10 was 132.8 (95% CI, 122.0-143.5) months, significantly longer compared to 93.7 (95% CI, 60.3-127.2) months for patients with a lower level of BMP-10 expression (P = 0.043). The overexpression of BMP-10 has broad inhibitory effects on the in vitro growth, invasion, and motility of breast cancer cells. Taken together, BMP-10 can inhibit the cell growth of breast cancer cells, and decreased BMP-10 expression correlates to poor prognosis and disease progression, particularly the lymphatic and bone metastasis. Bone morphogenetic protein-10 (BMP-10) may function as a tumor suppressor in breast cancer.

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.

Estrogen and xenoestrogens in breast cancer

There is growing concern that estrogenic environmental compounds that act as endocrine-disrupting chemicals might potentially have adverse effects on hormone-sensitive organs such as the breast. This concern is further fueled by evidence indicating that natural estrogens, specifically 17beta-estradiol, are important factors in the initiation and progression of breast cancer. We have developed an in vitro-in vivo model in which we have demonstrated the carcinogenicity of E2 in human breast epithelial cells MCF-10F. Hypermethylation of NRG1, STXBP6, BMP6, CSS3, SPRY1, and SNIP were found at different progression stages in this model. The use of this powerful and unique model has provided a tool for exploring whether bisphenol A and butyl benzyl phthalate have relevance in the initiation of breast cancer. These studies provide firsthand evidence that the natural estrogen 17beta-estradiol and xenoestrogenic substances like bisphenol A are able to induce neoplastic transformation in human breast epithelial cells.

Multiple endocrine regulation by bone morphogenetic protein system

Bone morphogenetic proteins (BMPs) were originally identified with regard to their actions to regulate ectopic formation of bone and cartilage and early embryonic development. Subsequently, our research program has investigated a BMP system that exists in the mammalian ovary and plays roles in regulating numerous granulosa cell functions. BMP ligands including BMP-2, -4, -6, -7 and -15 were found to inhibit gondotropin-dependent progesterone synthesis by granulosa cells, which led to the hypothesis that BMPs are a physiological luteinization inhibitor in growing ovarian follicles during the follicular phase of the ovarian cycle. The physiological importance of the BMP system for normal mammalian reproduction has been further recognized by the discovery of aberrant reproductive phenotypes of female sheep and humans having mutated genes encoding BMP-15. Physiological roles of BMPs in the pituitary, hypothalamus, adrenal and other tissues have also been discovered. Here we discuss recent advances in the understanding of autocrine/paracrine actions of BMPs in the systemic regulation of endocrine function.

Bone morphogenic protein 6: a member of a novel class of prognostic factors expressed by normal and malignant plasma cells inhibiting proliferation and angiogenesis

Pathogenesis of multiple myeloma is associated with an aberrant expression of pro-proliferative, pro-angiogenic and bone-metabolism-modifying factors by malignant plasma cells. Given the frequently long time span from diagnosis of early-stage plasma cell dyscrasias to overt myeloma and the mostly low proliferation rate of malignant plasma cells, we hypothesize these to similarly express a novel class of inhibitory factors of potential prognostic relevance. Bone morphogenic proteins (BMPs) represent possible candidates as they inhibit proliferation, stimulate bone formation and have an effect on the survival of cancer patients. We assessed the expression of BMPs and their receptors by Affymetrix DNA microarrays (n=779) including CD138-purified primary myeloma cell samples (n=635) of previously untreated patients. BMP6 is the only BMP expressed by malignant and normal plasma cells. Its expression is significantly lower in proliferating myeloma cells, myeloma cell lines or plasmablasts. BMP6 significantly inhibits the proliferation of myeloma cell lines, survival of primary myeloma cells and in vitro angiogenesis. A high BMP6 expression in primary myeloma cell samples delineates significantly superior overall survival for patients undergoing high-dose chemotherapy independent of conventional prognostic factors (International Staging System (ISS) stage, beta(2) microglobulin).

Applications of RNA interference in cancer therapeutics as a powerful tool for suppressing gene expression

Cancer poses a tremendous therapeutic challenge worldwide, highlighting the critical need for developing novel therapeutics. A promising cancer treatment modality is gene therapy, which is a form of molecular medicine designed to introduce into target cells genetic material with therapeutic intent. The history of RNA interference (RNAi) has only a dozen years, however, further studies have revealed that it is a potent method of gene silencing that has developed rapidly over the past few years as a result of its extensive importance in the study of genetics, molecular biology and physiology. RNAi is a natural process by which small interfering RNA (siRNA) duplex directs sequence specific post-transcriptional silencing of homologous genes by binding to its complementary mRNA and triggering its elimination. RNAi has been extensively used as a novel and effective gene silencing tool for the fundamental research of cancer therapeutics, and has displayed great potential in clinical treatment.

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.

Dual mechanism of deltaEF1 expression regulated by bone morphogenetic protein-6 in breast cancer

The metastatic nature of breast cancer has been well recognized, yet the mechanisms through which breast cancer cells acquire their invasive properties have not been clearly elucidated. Our previous study indicates that BMP-6 restores E-cadherin-mediated EMT through repressing deltaEF1 in breast cancer. However, the mechanism by which BMP-6 regulates deltaEF1 expression remains unclear. In this study, we confirmed the significant role of BMP-6 in inhibiting MDA-MB-231 migration through decreasing deltaEF1 expression which subsequently relieves deltaEF1-mediated invasion. The inhibitory effect of BMP-6 through deltaEF1 regulation was supported by an inverse correlation of BMP-6/miR-192 and deltaEF1 expressions observed in both MDA-MB-231 and MCF-7 cells and clinical tumor specimens. Moreover, BMP-6 treatment or miR-192 transfection decreased the reporter activity of the deltaEF1 3'-UTR-luc, validating that deltaEF1 is a target of miR-192. Meanwhile, we also found that BMP-6 acted as a potent transcriptional repressor of the human deltaEF1 promoter. Mutation of the AP-1 binding site on this promoter abolished BMP-6-induced transrepression of deltaEF1. Depletion of BMP-6 expression by RNAi resulted in a significant increase in the promoter activity of deltaEF1. Our study has provided novel findings of a dual mechanism for BMP-6-regulated deltaEF1 expression in breast cancer cells, involving cross-talks between AP-1-mediated transcriptional repression and miRs-mediated translational inhibition.

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.

Bone morphogenetic protein 6 inhibit stress-induced breast cancer cells apoptosis via both smad and P38 pathways

Breast carcinoma is one of the most common malignant tumors and has become a more common cancer in women. BMP6 was abnormally expressed in breast cancer specimens and cell lines. However, the contribution of BMP6 in promoting breast cancer progression remains unknown. The purpose of our study was to establish whether expression of BMP6 in breast cancer cells affect their proliferation or apoptosis and the mechanism. We found that BMP6 inhibited proliferation of MDA-MB-231 cells and blocked cell cycle at G(0)/G(1) stage. BMP6 also inhibited serum deprivation induced apoptosis in MDA-MB-231 cells. At the 4 days of serum starvation, BMP6 reduced the percentage of caspase-3 positive cells from 49% to 21%, BMP6 also reduced sub-G(1) peak induced by serum starvation. In contrast, BMP6 significantly enhanced survivin expression both at mRNA and protein levels. Dominant negative-survivin and Antisense-survivin impaired BMP6 induced antiapoptotic effect. BMP6 enhanced survivin expression at the transcription level in a Smad-dependent manner. BMP6 also played its antiapoptotic effect through activation p38 MAPK signal pathway, independent of smad/survivin pathway. These results suggested that BMP6 induced cell cycle arrest in estrogen-insensitive breast cancer cells. BMP6 inhibits stress-induced apoptosis via both Smad and p38 signal pathways.

BMP-6 promotes E-cadherin expression through repressing deltaEF1 in breast cancer cells

BACKGROUND

Bone morphogenetic protein-6 (BMP-6) is critically involved in many developmental processes. Recent studies indicate that BMP-6 is closely related to tumor differentiation and metastasis.

METHODS

Quantitative RT-PCR was used to determine the expression of BMP-6, E-cadherin, and deltaEF1 at the mRNA level in MCF-7 and MDA-MB-231 breast cancer cells, as well as in 16 breast cancer specimens. Immunoblot analysis was used to measure the expression of deltaEF1 at the protein level in deltaEF1-overexpressing and deltaEF1-interfered MDA-MB-231 cells. Luciferase assay was used to determine the rhBMP-6 or deltaEF1 driven transcriptional activity of the E-cadherin promoter in MDA-MB-231 cells. Quantitative CHIP assay was used to detect the direct association of deltaEF1 with the E-cadherin proximal promoter in MDA-MB-231 cells.

RESULTS

MCF-7 breast cancer cells, an ER+ cell line that expressed high levels of BMP-6 and E-cadherin exhibited very low levels of deltaEF1 transcript. In contrast, MDA-MB-231 cells, an ER- cell line had significantly reduced BMP-6 and E-cadherin mRNA levels, suggesting an inverse correlation between BMP-6/E-cadherin and deltaEF1. To determine if the same relationship exists in human tumors, we examined tissue samples of breast cancer from human subjects. In 16 breast cancer specimens, the inverse correlation between BMP-6/E-cadherin and deltaEF1 was observed in both ER+ cases (4 of 8 cases) and ER- cases (7 of 8 cases). Further, we found that BMP-6 inhibited deltaEF1 transcription, resulting in an up-regulation of E-cadherin mRNA expression. This is consistent with our analysis of the E-cadherin promoter demonstrating that BMP-6 was a potent transcriptional activator. Interestingly, ectopic expression of deltaEF1 was able to block BMP-6-induced transactivation of E-cadherin, whereas RNA interference-mediated down-regulation of endogenous deltaEF1 in breast cancer cells abolished E-cadherin transactivation by BMP-6. In addition to down-regulating the expression of deltaEF1, BMP-6 also physically dislodged deltaEF1 from E-cadherin promoter to allow the activation of E-cadherin transcription.

CONCLUSION

We conclude that repression of deltaEF1 plays a key role in mediating BMP-6-induced transcriptional activation of E-cadherin in breast cancer cells. Consistent with the fact that higher level of deltaEF1 expression is associated with more invasive phenotype of breast cancer cells, our collective data suggests that deltaEF1 is likely the switch through which BMP-6 restores E-cadherin-mediated cell-to-cell adhesion and prevents breast cancer metastasis.

Epigenetic regulation of bone morphogenetic protein-6 gene expression in breast cancer cells

Bone morphogenetic protein-6 (BMP-6) is closely correlated with tumor differentiation and skeletal metastasis. Our previous research found that BMP-6 gene expression can be activated dose-dependently by estrogen in estrogen receptor positive (ER(+)) breast cancer cell line MCF-7, but not in ER negative (ER(-)) cell line MDA-MB-231. This experiment is designed to investigate the epigenetic regulatory mechanism of the BMP-6 gene expression in breast cancer cell lines MDA-MB-231, MCF-7 and T47D with regard to the methylation status in the 5' flanking region of the human BMP-6 gene. The endogenous level of BMP-6 mRNA in ER(-) cell line MDA-MB-231 was relatively lower than that in ER(+) MCF-7 and T47D cell lines. After the treatment with 5-aza-2'-deoxycytidine (5-aza-dC, especially in the concentration of 10 microM), the BMP-6 mRNA expression in MDA-MB-231 was obviously up-regulated. However, 5-aza-dC treatment failed to regulate the expression of BMP-6 in MCF-7 and T47D cells. Using enzyme restriction PCR (MSRE-PCR), as well as bisulfite sequencing (BSG), methylation of human BMP-6 gene promoter was detected in MDA-MB-231; while in MCF-7 and T47D, BMP-6 gene promoter remained demethylated status. In 33 breast tumor specimens, promoter methylation of BMP-6 was detected by methylation-specific PCR, hypermethylation of BMP-6 was observed in ER negative cases (16 of 16 cases (100%)), while obviously lower methylation frequency were observed in ER positive cases (3 of 17 cases (18%)), indicating that BMP-6 promoter methylation status is correlated with ER status in breast cancer.

The role of growth differentiation factor-9 (GDF-9) and its analog, GDF-9b/BMP-15, in human breast cancer

BACKGROUND

There has been a recent surge of interest in the role of growth differentiation factors and other bone morphogenic proteins in the development and spread of cancer. In this study we have provided evidence that highlights the significance of growth and differentiation factor-9a (GDF-9a) and GDF-9b (bone morphogenic protein-15, BMP-15) in breast cancer development and progression.

METHODS

Primary breast cancer samples (n = 109) and matched background tissues from same patients (n = 33) were processed for frozen section and RNA extraction. Frozen sections from matched tissues were immunostained with GDF-9a and GDF-9b antibodies. Staining intensity was analyzed by computer image analysis. RNA was reverse transcribed and quantified before analysis by quantitative polymerase chain reaction (Q-PCR). Results were expressed as number of transcripts (standardized by beta-actin). The data were compared with the clinical outcome of the disease. The biological effects of the molecule were studied using in vitro assays after forced expression in breast cancer cells.

RESULTS

Highly aggressive breast cancer cells did not express GDF-9a. On forced expression of GDF-9a, breast cancer cells became less invasive. These laboratory findings were analyzed against the clinical information. Primary breast cancer samples with good predicted prognosis had a significantly higher level of GDF-9a than in samples with poor predicted prognosis (P = .004). Patients who remained disease-free at the end of a 10-year follow-up had significantly higher levels of both GDF-9a and GDF-9b in their tissue than those with poor clinical outcome (P = .001 and .014, respectively).

CONCLUSION

Growth differentiation factor-9 family expressed in breast cancer has an inhibitory effect on the progression of human breast cancer.

A comprehensive expression survey of bone morphogenetic proteins in breast cancer highlights the importance of BMP4 and BMP7

Bone morphogenetic proteins (BMPs) regulate diverse cellular processes, such as proliferation, differentiation, and apoptosis. The BMPs have been studied in several cancers, but thus far contradictory results have been obtained and, especially in breast cancer, information on BMPs is still limited. We performed a systematic expression survey of BMPs and their receptors in breast cancer. mRNA expression was studied of seven BMP ligands (BMP2-BMP8) and six receptors (ACVR1, BMPR1A, BMPR1B, BMPR2, ACVR2A, and ACVR2B) that specifically mediate BMP signals. Expression levels were determined in 22 breast cancer cell lines, 39 primary breast tumors, normal human mammary epithelial cell line, and normal mammary gland using semiquantitative RT-PCR. The expression frequencies and expression levels of different BMPs varied considerably in breast cancer with BMP4 and BMP7 being most frequently expressed and showing highest expression levels. The BMP specific receptors were more uniformly expressed and indicated that breast cancer is fully capable of transmitting BMP signals. Expression frequencies and levels for both the ligands and the receptors were in good concordance between the breast cancer cell lines and primary tumors. We can conclude that breast cancers possess functional BMP signaling machinery on the cell surface with distinct differences in the expression of various BMP ligands. Our survey focuses the attention particularly toward BMP4 and BMP7 and suggests their importance in breast cancer. Breast cancer cell lines and the data generated here serve as a good resource for further studies on BMP function in breast cancer.

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.

Tenascin-W is found in malignant mammary tumors, promotes alpha8 integrin-dependent motility and requires p38MAPK activity for BMP-2 and TNF-alpha induced expression in vitro

Tenascins represent a family of extracellular matrix glycoproteins with distinctive expression patterns. Here we have analyzed the most recently described member, tenascin-W, in breast cancer. Mammary tumors isolated from transgenic mice expressing hormone-induced oncogenes reveal tenascin-W in the stroma around lesions with a high likelihood of metastasis. The presence of tenascin-W was correlated with the expression of its putative receptor, alpha8 integrin. HC11 cells derived from normal mammary epithelium do not express alpha8 integrin and fail to cross tenascin-W-coated filters. However, 4T1 mammary carcinoma cells do express alpha8 integrin and their migration is stimulated by tenascin-W. The expression of tenascin-W is induced by BMP-2 but not by TGF-beta1, though the latter is a potent inducer of tenascin-C. The expression of tenascin-W is dependent on p38MAPK and JNK signaling pathways. Since preinflammatory cytokines also act through p38MAPK and JNK signaling pathways, the possible role of TNF-alpha in tenascin-W expression was also examined. TNF-alpha induced the expression of both tenascin-W and tenascin-C, and this induction was p38MAPK- and cyclooxygenase-dependent. Our results show that tenascin-W may be a useful diagnostic marker for breast malignancies, and that the induction of tenascin-W in the tumor stroma may contribute to the invasive behavior of tumor cells.

Bone Morphogenetic Proteins Are Expressed by Both Bone-Forming and Non-Bone-Forming Lesions

Context.-Bone morphogenetic proteins (BMPs) are thought to be responsible for bone formation; they cause bone to form in soft tissues and are clinically used in helping fracture union or tumor reconstructions. Skeletal metastases from epithelial tumors may be either bone-forming (blastic) or non-bone-forming (lytic).Objective.-We studied the expression of BMPs in a variety of primary and secondary lesions of bone (both bone-forming and non-bone-forming) to determine if there was a consistent relationship between bone formation and BMP expression.Design.-We compared a bone-forming lesion (fibrous dysplasia) with a non-bone-forming lesion (desmoid tumor), using reverse transcription-polymerase chain reaction, Northern blot analysis, and immunohistochemistry to detect BMPs. We also studied a number of non-bone-forming secondary lesions (carcinomas that formed lytic metastases to the skeleton) and found BMP production in most of these tumors.Results.-We found that BMPs were expressed in both bone-forming and non-bone-forming benign musculoskeletal lesions. In the first part of the study, BMPs were found in both fibrous dysplasia and desmoid tumors. Bone morphogenetic proteins were also expressed by several tumors. In the next part of the study (paraffin-embedded tissue), BMPs were expressed by a variety of tumors, irrespective of the radiological nature (blastic or lytic) of their metastases.Conclusions.-We conclude that BMP production alone cannot explain bone formation, and other factors either alone or in combination may be responsible for blastic metastases to the skeleton and for bone formation by primary bone lesions, such as fibrous dysplasia.

Transcriptional regulation of a BMP-6 promoter by estrogen receptor alpha

The effects of 17beta-estradiol (E2) and ICI 182,780 (ICI) on activity of a BMP-6 promoter were compared in osteoblast-like and breast cancer cells transiently transfected with ERalpha. E2 but not ICI stimulated BMP-6 reporter activity in breast cancer cells, whereas the opposite was observed in osteoblast-like cells, associated with lack of AF-2 dependence of the response, and absent intranuclear localization of ERalpha, suggesting the involvement of a distinct ERalpha-dependent response mechanism in osteoblasts.

INTRODUCTION

Previous studies suggest that the tissue-selective effect of antiestrogens on bone reflects the ability of these compounds to target certain osteoblast regulatory genes. To explore this hypothesis, we examined whether antiestrogens preferentially stimulate the bone morphogenetic protein 6 (BMP-6) promoter in bone cells, and if so, whether this activity is associated with a distinct estrogen receptor (ER)alpha-dependent response mechanism to that in other cell types.

MATERIALS AND METHODS

We compared the effects of 17beta-estradiol (E2) and ICI 182,780 (ICI) on activity of a 4.3-kb BMP-6 reporter construct in osteoblast-like cells (human MG63 and SaOS-2 cells and rat ROS 17/2.8 cells), human MCF-7 and T47-D breast cancer cell lines, and HepG2 hepatoma cells, after transient transfection with ERalpha, ERbeta, and mutant ER constructs.

RESULTS

E2, but not ICI, stimulated BMP-6 reporter activity by approximately 100% in MCF-7, T47-D cells, and HepG2 cells when transfected with ERalpha. In contrast, in ERalpha-transfected osteoblast-like cells, an increase in reporter activity of approximately 75% was observed after treatment with ICI but not E2. The response of MG63 cells to ICI and MCF-7 cells to E2 both required ERalpha as opposed to ERbeta and the ERalpha activation function (AF)-1 activation domain. However, whereas the AF-2 domain was also required for E2 to stimulate reporter activity in MCF-7 cells, the response to ICI in MG63 cells was AF-2 independent. In further studies where we compared the intracellular distribution of ERalpha associated with these responses, E2-dependent stimulation of the BMP-6 reporter in MCF-7 cells was associated with intranuclear localization of ERalpha, whereas extranuclear localization was seen in rat osteosarcoma cells (ROS) cells treated with ICI.

CONCLUSIONS

Antiestrogens selectively stimulate BMP-6 reporter activity in osteoblast-like cells through a distinct ERalpha-dependent mechanism characterized by independence of the AF-2 domain and extranuclear localization of ERalpha.

Overexpression of bone morphogenetic protein-6 (BMP-6) in murine epidermis suppresses skin tumor formation by induction of apoptosis and downregulation of fos/jun family members

Bone morphogenetic protein-6 (BMP-6) is a member of the transforming growth factor-beta superfamily. In murine skin, BMP-6 is highly expressed in postmitotic keratinocytes from day 15.5 p.c. till day 6 p.p. Expression in adult skin remains at very low levels, but pathological conditions such as wounding induce the expression of BMP-6. We demonstrate that tumor promotion by TPA (12-O-tetradecanoylphorbol-13-acetate) also induces expression of BMP-6 in suprabasal keratinocytes. This induction is due to post-transcriptional regulation since the level of BMP-6 mRNA remained unchanged. We performed two-stage skin carcinogenesis experiments with transgenic mice epidermally overexpressing BMP-6. These mice display augmented mitotic indices in normal and TPA-treated epidermis when compared to controls. Despite this hyperproliferation, BMP-6 transgenics showed a delayed development and strong suppression of benign and malignant skin tumor formation. In order to resolve this paradox we determined apoptotic frequencies as well as the expression of constituents of AP-1 (activator protein-1) which is essential for tumor promotion. A higher rate of apoptotic keratinocytes was detectable in transgenic mice versus controls and a downregulation of mRNA for jun/fos family members in transgenic skin after TPA-treatment. Thus expression of BMP-6 augments apoptosis and downregulates the transcription of AP-1 family members thereby establishing tumor resistance.

Bone sialoprotein, bone morphogenetic protein 6 and thymidine phosphorylase expression in localized human prostatic adenocarcinoma as predictors of clinical outcome: a clinicopathological and immunohistochemical study of 43 cases

PURPOSE

Skeletal metastases are the hallmark of advanced prostate cancer and recurrence after local surgery is common. Currently to our knowledge no biological markers predict the risk of disease progression in individuals with localized prostate cancer. In a search for predictive markers we evaluated the expression of bone sialoprotein and bone morphogenetic protein 6, 2 bone related proteins, and the angiogenic factor thymidine phosphorylase.

MATERIALS AND METHODS

The study population included 43 men who presented with localized prostate cancer treated with radical prostatectomy. Bone sialoprotein, bone morphogenetic protein 6 and thymidine phosphorylase expression was assessed by immunohistochemical testing. Results were analyzed in relation to pathological disease stage, Gleason score and clinical outcome. Clinical followup was 4.3 to 11.4 years after surgery (median 7.9).

RESULTS

Disease did not progress in 17 of the 43 cases, while recurrence and/or metastasis developed in the other 26 at a median of 6.5 and 6.9 years, respectively. Bone sialoprotein and bone morphogenetic protein 6 expression detected in 28 (65%) and 29 (67%) of the 43 samples, respectively, was significantly associated (p = 0.0001). Thymidine phosphorylase detected in 26 samples (60%) was not related to bone sialoprotein and/or bone morphogenetic protein 6 positivity. Bone sialoprotein and/or bone morphogenetic protein 6 expression correlated with bone metastasis, while thymidine phosphorylase expression was related to local recurrence (p = 0.002 and/or 0.007, and 0.00007, respectively). On multivariate analysis only the correlation of thymidine phosphorylase expression with recurrence remained statistically significant (p = 0.002). Co-expression of the 3 markers was observed in the samples of 10 of the 11 patients (90%) with bone metastases and only in 5 of the 17 (29%) who were disease-free.

CONCLUSIONS

This study indicates that the expression of bone sialoprotein, bone morphogenetic protein 6 and thymidine phosphorylase determined at a clinically early stage of disease by a simple immunohistochemical technique would enable subgroups of patients to be identified that are at different risks of bone metastasis or recurrence. Detection of such markers would provide additional prognostic information that would be useful for patients with intermediate or low Gleason score or stage disease. These patients would benefit from a more adapted clinical follow-up.

Expression of bone morphogenetic protein-6 (BMP-6) in myoepithelial cells in canine mammary gland tumors

Seventy-three mammary tumors and three mammary tissue specimens were examined to elucidate the expression of bone morphogenetic protein (BMP)-6 in the myoepithelial cells of canine mammary gland tumors. Morphologically, the myoepithelial cells were classified into four types: resting and proliferating cells inside the basement membrane, and spindle- and star-shaped cells proliferating in the outer area of the basement membrane. The characteristics of these myoepithelial cells were confirmed by immunohistochemistry using antibodies raised against keratin, cytokeratin 19, alpha-smooth muscle actin, and vimentin. In simple adenoma, a small number of resting myoepithelial cells was immunopositive for BMP-6. In complex adenomas and benign mixed tumors, all types of myoepithelial cells, depending in some cases on their specific location within the tumor, were immunopositive for BMP-6, but almost all of the tubular epithelial cells were immunonegative. Foci consisting of a proliferation of BMP-6-positive star- and spindle-shaped cells had mucinous stroma with marked hyaline and chondroid changes. In contrast, the foci with BMP-6-negative spindle- and star-shaped cells tended to have mucinous stroma without chondroid change. Several types of mesenchymal cells including chondrocytes, osteoblasts, and fibroblastlike cells in the mixed tumors, showed an intense immunopositive reaction for the BMP-6 antibody, and were located close to the ectopic cartilage and bone matrix. No significant immunoreactivity for BMP-6 was observed in most of the malignant mammary tumors; only one malignant mixed tumor was examined. All of these findings indicate that BMP-6 expression in myoepithelial cells may increase in complex adenomas and benign mixed tumors in canine mammary glands, and that BMP-6 expression is most intense in the vicinity of chondroid matrix in these tumors.

BMP-7-induced cell cycle arrest of anaplastic thyroid carcinoma cells via p21(CIP1) and p27(KIP1)

The aim of the present study was to investigate the effect of bone morphogenetic protein (BMP-7) on thyroid carcinoma cell growth. Addition of BMP-7 inhibited the proliferation of four out of six human anaplastic thyroid carcinoma cell lines, observed as decreased incorporation of (3)H-thymidine and decreased cell number. The growth inhibitory effect was cell density-dependent; sparse cells were inhibited by BMP-7 whereas dense cells were not. Cell cycle analysis by flow cytometry showed an increased fraction of cells in the G1-phase and subsequent decrease in both S- and G2/M-phase after BMP-7 stimulation. Furthermore, BMP-7 caused an upregulation of the cyclin-dependent kinase inhibitors (CDKIs) p21 and p27, decreased activity of Cdk2 and Cdk6, and hypophosphorylation of the retinoblastoma protein (pRb). These findings suggest a growth inhibitory effect of BMP-7 on anaplastic thyroid carcinoma cells by inhibition of Cdk activity shifting the Rb protein to the hypophosphorylated state.

Epigenetic regulation of human bone morphogenetic protein 6 gene expression in prostate cancer

Bone morphogenetic proteins (BMPs), belonging to the transforming growth factor-beta (TGF-beta) superfamily, are multifunctional molecules that regulate bone induction and organ development. Among BMPs, BMP-6 has been shown to be overexpressed in prostate cancer and is speculated to be associated with bone-forming skeletal metastasis. We investigated the regulatory mechanism of the BMP-6 gene expression in prostate cancer cell lines DU-145, LNCaP, PC-3, and PC-3M with regard to the methylation status of the CpG island in the 5' flanking region of the human BMP-6 gene. By sequence-specific analysis of methylated cytosines, we show here that the methylation status of the CpG loci around the Sp1 site of the BMP-6 promoter is related to its steady-state expression and an alternative splicing of messenger RNA (mRNA) in prostate cancer cell lines. Furthermore, a study of clinical cases of benign and malignant prostate lesion by in situ hybridization showed that BMP-6 expression was high at both primary and secondary sites in cases of advanced cancer with metastasis. Demethylation of the CpG loci around the Spl binding site was shown in cases with high BMP-6 expression by sequencing analysis of the methylated cytosine from paraffin-embedded materials. Our results suggested that during cancer progression, besides inactivation of tumor suppressor genes by hypermethylation, activation of certain genes like BMP-6 by selective demethylation was a common epigenetic event giving a variable character to the invading and metastasizing cancer cells.

Bone morphogenetic protein-4 inhibits proliferation and induces apoptosis of multiple myeloma cells

Bone morphogenetic proteins (BMPs) can be isolated from organic bone matrix and are able to initiate de novo cartilage and bone formation. Here it is shown that BMP-4 inhibited DNA synthesis in a dose-dependent manner in 3 IL-6-dependent multiple myeloma (MM) cell lines (OH-2, IH-1, and ANBL-6). In contrast, no effect on DNA synthesis was observed in 3 IL-6-independent MM cell lines (JJN-3, U266, and RPMI 8226). BMP-4 induced cell cycle growth arrest in the G(0)/G(1) phase in OH-2 and ANBL-6 cells but not in IH-1 cells. BMP-4 induced apoptosis in OH-2 and IH-1 cells, but not significantly in ANBL-6 cells. Furthermore, BMP-4 induced apoptosis in freshly isolated MM cells from 4 of 13 patients. In the OH-2 and ANBL-6 cell lines and in a patient sample, immunoblotting showed that BMP-4 down-regulated IL-6-induced tyrosine phosphorylation of Stat3, suggesting a mechanism for the apparent antagonism between IL-6 and BMP-4. BMP-4 or analogues may be attractive therapeutic agents in MM because of possible beneficial effects on both tumor burden and bone disease.

Bone morphogenetic proteins secreted by breast cancer cells upregulate bone sialoprotein expression in preosteoblast cells

It is well established that bone metastases comprise bone; however, the exact factors/mechanisms involved remain unknown. We hypothesized that tumor cells secreted factors capable of altering normal bone metabolism. The aims of the present study were to (1) determine the effects of secretory products isolated from HT-39 cells, a human breast cancer cell line, on osteoprogenitor cell (MC3T3-E1 cells) behavior, and (2) identify tumor-derived factor(s) that alters osteoblast activities. Conditioned media (CM) from HT-39 cells were collected following a 24-h serum-free culture. The ability of CM to alter gene expression in MC3T3-E1 cells was determined by Northern analysis. CM effects on cell proliferation and mineralization ability were determined using a Coulter counter and von Kossa stain, respectively. MC3T3-E1 cells were treated with CM plus noggin, a factor known to block bone morphogenic proteins (BMPs), to determine whether BMPs, shown to be present in CM, were linked with CM effects on MC3T3-E1 cell activity. In addition, inhibitors of MAP kinase kinase (MEK), protein kinase C (PKC), and protein kinase A were used to identify the intracellular signaling pathway(s) by which the active factors in CM regulated osteoblast behavior. CM treatment significantly enhanced BSP mRNA (2.5-fold over control), but had no effect on cell proliferation. Mineralization assay showed that CM enhanced mineral nodule formation compared to controls. Noggin inhibited CM-induced upregulation of BSP mRNA, suggesting that BMPs were responsible for upregulating BSP gene expression in MC3T3-E1 cells. The PKC inhibitor blocked CM-mediated upregulation of BSP, suggesting involvement of the PKC pathway in regulating BSP expression. BMPs secreted by HT-39 cells may be responsible for enhancing BSP expression in MC3T3-E1 cells. Continued studies targeted at determining the role of BMPs in regulating bone metabolism are important for understanding the pathogenesis of bone diseases.

Mullerian inhibiting substance inhibits breast cancer cell growth through an NFkappa B-mediated pathway

Müllerian inhibiting substance (MIS), a member of the transforming growth factor-beta superfamily, induces regression of the Müllerian duct in male embryos. In this report, we demonstrate MIS type II receptor expression in normal breast tissue and in human breast cancer cell lines, breast fibroadenoma, and ductal adenocarcinomas. MIS inhibited the growth of both estrogen receptor (ER)-positive T47D and ER-negative MDA-MB-231 breast cancer cell lines, suggesting a broader range of target tissues for MIS action. Inhibition of growth was manifested by an increase in the fraction of cells in the G(1) phase of the cell cycle and induction of apoptosis. Treatment of breast cancer cells with MIS activated the NFkappaB pathway and selectively up-regulated the immediate early gene IEX-1S, which, when overexpressed, inhibited breast cancer cell growth. Dominant negative IkappaBalpha expression ablated both MIS-mediated induction of IEX-1S and inhibition of growth, indicating that activation of the NFkappaB signaling pathway was required for these processes. These results identify the NFkappaB-mediated signaling pathway and a target gene for MIS action and suggest a putative role for the MIS ligand and its downstream interactors in the treatment of ER-positive as well as negative breast cancers.

Expression, regulation and clinical significance of bone morphogenetic protein 6 in esophageal squamous-cell carcinoma

Bone morphogenetic proteins (BMPs) are multifunctional cytokines. BMP-6 is involved in early steps of keratinogenesis. Esophageal squamous-cell carcinoma often shows abnormal keratinization. The aim of this study was to examine the expression and regulation of BMP-6 in esophageal carcinoma and to determine the relationship of its expression with tumor characteristics and survival. Avidin-biotin-peroxidase staining was performed using paraffin-wax-embedded tumor specimens collected from 172 patients with esophageal squamous-cell carcinoma, who underwent potentially curative surgery. Expression of BMP-6 and EGF-receptor in the esophageal-squamous-cell-carcinoma cell line COLO-680N and the hypopharyngeal-squamous-cell-carcinoma cell line FaDu was assayed with specific RT-PCR. In standard cell-cultivation conditions, COLO-680N and FaDu cells showed distinct expression of BMP-6, whereas in serum-free conditions BMP-6 expression was hardly detectable. The addition of EGF or EGF-related growth factors could elevate BMP-6 mRNA content. Immunohistochemically, all 172 tumors exhibited cytoplasmic immunoreactivity for BMP-6. The content of BMP-6 protein was inversely correlated with tumor differentiation (p < 0.01). Univariate survival analysis revealed that 74 patients with tumors of low immunoreactivity had higher 2-year and 5-year survival rates (50.0%/27.7%) than 75 patients with tumors of high immunoreactive scores (33.3%/21.6%). (p < 0.05). We conclude that BMP-6 is expressed in esophageal squamous-cell carcinoma. EGF-receptor activation is crucial for regulation of BMP-6 expression. BMP-6 protein content is correlated with the grade of tumor-cell differentiation and may add to indications of poor prognosis.