Bone morphogenetic protein-5, -6 and -7 inhibit growth and induce apoptosis in human myeloma cells

A cell cycle centric view of tumour dormancy

Tumour dormancy and recurrent metastatic cancer remain the greatest clinical challenge for cancer patients. Dormant tumour cells can evade treatment and detection, while retaining proliferative potential, often for years, before relapsing to tumour outgrowth. Cellular quiescence is one mechanism that promotes and maintains tumour dormancy due to its central role in reducing proliferation, elevating cyto-protective mechanisms, and retaining proliferative potential. Quiescence/proliferation decisions are dictated by intrinsic and extrinsic signals, which regulate the activity of cyclin-dependent kinases (CDKs) to modulate cell cycle gene expression. By clarifying the pathways regulating CDK activity and the signals which activate them, we can better understand how cancer cells enter, maintain, and escape from quiescence throughout the progression of dormancy and metastatic disease. Here we review how CDK activity is regulated to modulate cellular quiescence in the context of tumour dormancy and highlight the therapeutic challenges and opportunities it presents.

High concentrations of soluble endoglin can inhibit BMP9 signaling in non-endothelial cells

Endoglin (ENG) is a single-pass transmembrane protein highly expressed on vascular endothelial cells, although low expression levels can be detected in many other cell types. Its extracellular domain can be found in circulation known as soluble endoglin (sENG). Levels of sENG are elevated in many pathological conditions, in particular preeclampsia. We have shown that while loss of cell surface ENG decreases BMP9 signaling in endothelial cells, knocking down ENG in blood cancer cells enhances BMP9 signaling. Despite sENG binding to BMP9 with high affinity and blocking the type II receptor binding site on BMP9, sENG did not inhibit BMP9 signaling in vascular endothelial cells, but the dimeric form of sENG inhibited BMP9 signaling in blood cancer cells. Here we report that in non-endothelial cells such as human multiple myeloma cell lines and the mouse myoblast cell line C2C12, both monomeric and dimeric forms of sENG inhibit BMP9 signaling when present at high concentrations. Such inhibition can be alleviated by the overexpression of ENG and ACVRL1 (encoding ALK1) in the non-endothelial cells. Our findings suggest that the effects of sENG on BMP9 signaling is cell-type specific. This is an important consideration when developing therapies targeting the ENG and ALK1 pathway.

FKBP12 is a major regulator of ALK2 activity in multiple myeloma cells

BACKGROUND

The immunophilin FKBP12 binds to TGF-β family type I receptors, including the BMP type I receptor ALK2. FKBP12 keeps the type I receptor in an inactive state and controls signaling activity. Removal of FKBP12 with drugs such as the FKBP-ligand FK506 enhances BMP activity in various cell types. In multiple myeloma cells, activation of SMAD1/5/8 leads to apoptosis. We hypothesized that removing FKBP12 from ALK2 in myeloma cells would potentiate BMP-induced ALK2-SMAD1/5/8 activity and in consequence cell death.

METHODS

Multiple myeloma cell lines were treated with FK506, or other FKBP-binding compounds, combined with different BMPs before analyzing SMAD1/5/8 activity and cell viability. SMAD1/5/8 activity was also investigated using a reporter cell line, INA-6 BRE-luc. To characterize the functional signaling receptor complex, we genetically manipulated receptor expression by siRNA, shRNA and CRISPR/Cas9 technology.

RESULTS

FK506 potentiated BMP-induced SMAD1/5/8 activation and apoptosis in multiple myeloma cell lines. By using FKBP-binding compounds with different affinity profiles, and siRNA targeting FKBP12, we show that the FK506 effect is mediated by binding to FKBP12. Ligands that typically signal via ALK3 in myeloma cells, BMP2, BMP4, and BMP10, did not induce apoptosis in cells lacking ALK3. Notably, BMP10 competed with BMP6 and BMP9 and antagonized their activity via ALK2. However, upon addition of FK506, we saw a surprising shift in specificity, as the ALK3 ligands gained the ability to signal via ALK2 and induce apoptosis. This indicates that the receptor complex can switch from an inactive non-signaling complex (NSC) to an active one by adding FK506. This gain of activity was also seen in other cell types, indicating that the observed effects have broader relevance. BMP2, BMP4 and BMP10 depended on BMPR2 as type II receptor to signal, which contrasts with BMP6 and BMP9, that activate ALK2 more potently when BMPR2 is knocked down.

CONCLUSIONS

In summary, our data suggest that FKBP12 is a major regulator of ALK2 activity in multiple myeloma cells, partly by switching an NSC into an active signaling complex. FKBP12 targeting compounds devoid of immunosuppressing activity could have potential in novel treatment strategies aiming at reducing multiple myeloma tumor load. Video Abstract.

NORAD promotes multiple myeloma cell progression via BMP6/P-ERK1/2 axis

Multiple myeloma (MM) is one of the most common tumors of the hematological system and remains incurable. Recent studies have shown that long noncoding RNA NORAD is a potential oncogene in a variety of tumors. However, the general biological role and clinical value of NORAD in MM remains unknown. In this study, we measured NORAD expression in bone marrow of 60 newly diagnosed MM, 30 post treatment MM and 17 healthy donors by real-time quantitative polymerase chain reaction (qPCR). The NORAD gene was knockdown by lentiviral transfection in MM cell lines, and the effects of NORAD on apoptosis, cell cycle and cell proliferation in MM cells were examined by flow cytometry, CCK8 assay, EDU assay and Western blot, and the differential genes after knockdown of NORAD were screened by mRNA sequencing, followed by in vivo experiments and immunohistochemical assays. We found that knockdown of NORAD promoted MM cell apoptosis, induced cell cycle G1 phase arrest, and inhibited MM cell apoptosis in in vivo and in vitro experiments. Mechanistically, NORAD plays these roles through the BMP6/P-ERK1/2 axis. We discuss a novel mechanism by which NORAD acts pro-tumorigenically in MM via the BMP6/P-ERK1/2 axis.

Upregulated bone morphogenetic protein 5 enhances proliferation and epithelial-mesenchymal transition process in benign prostatic hyperplasia via BMP/Smad signaling pathway

BACKGROUND

Benign prostatic hyperplasia (BPH) is one of the most common illnesses in aging men. Recent studies found that bone morphogenetic protein 5 (BMP5) is upregulated in BPH tissues, however, the role of BMP5 in the development of BPH has not been examined. The current study aims to elucidate the potential roles of BMP5 and related signaling pathways in BPH.

METHODS

Human prostate cell lines (BPH-1, WPMY-1) and human/rat hyperplastic prostate tissues were utilized. Western blot, quantitative real-time polymerase chain reaction, immunofluorescent staining, and immunohistochemical staining were performed. BMP5-silenced and -overexpressed cell models were generated and then cell cycle progression, apoptosis, and proliferation were determined. The epithelial-mesenchymal transition (EMT) was also quantitated. And rescue experiments by BMP/Smad signaling pathway agonist or antagonist were accomplished. Moreover, BPH-related tissue microarray analysis was performed and associations between clinical parameters and expression of BMP5 were analyzed.

RESULTS

Our study demonstrated that BMP5 was upregulated in human and rat hyperplastic tissues and localized both in the epithelial and stromal compartments of the prostate tissues. E-cadherin was downregulated in hyperplastic tissues, while N-cadherin and vimentin were upregulated. Overexpression of BMP5 enhanced cell proliferation and the EMT process via phosphorylation of Smad1/5/8, while knockdown of BMP5 induced cell cycle arrest at G0/G1 phase and blocked the EMT process. Moreover, a BMP/Smad signaling pathway agonist and antagonist reversed the effects of BMP5 silencing and overexpression, respectively. In addition, BMP5 expression positively correlated with prostate volume and total prostate-specific antigen.

CONCLUSION

Our novel data suggest that BMP5 modulated cell proliferation and the EMT process through the BMP/Smad signaling pathway which could contribute to the development of BPH. However, further studies are required to determine the exact mechanism. Our study also indicated that BMP/Smad signaling may be rediscovered as a promising new therapeutic target for the treatment of BPH.

BMP5 silencing inhibits chondrocyte senescence and apoptosis as well as osteoarthritis progression in mice

In this study, we using the in vivo destabilization of the medial meniscus (DMM) mouse model to investigate the role of bone morphogenetic protein 5 (BMP5) in osteoarthritis (OA) progression mediated via chondrocyte senescence and apoptosis. BMP5 expression was significantly higher in knee articular cartilage tissues of OA patients and DMM model mice than the corresponding controls. The Osteoarthritis Research Society International scores based on histological staining of knee articular cartilage sections were lower in DMM mice where BMP5 was knocked down in chondrocytes than the corresponding controls 4 weeks after DMM surgery. DMM mice with BMP5-deficient chondrocytes showed reduced levels of matrix-degrading enzymes such as MMP13 and ADAMTS5 as well as reduced cartilage destruction. BMP5 knockdown also decreased chondrocyte apoptosis and senescence by suppressing the activation of p38 and ERK MAP kinases. These findings demonstrate that BMP5 silencing inhibits chondrocyte senescence and apoptosis as well as OA progression by downregulating activity in the p38/ERK signaling pathway.

Morphogens and growth factor signalling in the myeloma bone-lining niche

Multiple myeloma is a malignancy caused by the clonal expansion of abnormal plasma cells. Myeloma cells have proven to be incredibly successful at manipulating their microenvironment to promote growth and to evade modern therapies. They have evolved to utilise the integral signalling pathways of the bone and bone marrow to drive disease progression. The bone marrow is often described in the context of a single structure that fills the bone cavity and supports normal haematopoiesis. However, within that structure exists two anatomically different niches, the perivascular niche and the endosteal niche. These contain different cell types functioning to support normal immune and blood cell production as well as healthy bone. These cells secrete numerous signalling molecules that can influence myeloma cell biology and behaviour. The endosteal niche is home to specific bone cell lineages and plays a pivotal role in myeloma cell establishment and survival. This review will concentrate on some of the signalling pathways that are hijacked by myeloma cells to shape a favourable environment, and the different influences myeloma cells are exposed to depending on their spatial location within the bone marrow.

Targeting dormant tumor cells to prevent cancer recurrence

Over the years, developments in oncology led to significantly improved clinical outcome for cancer patients. However, cancer recurrence after initial treatment response still poses a major challenge, as it often involves more aggressive, metastatic disease. The presence of dormant cancer cells is associated with recurrence, metastasis, and poor clinical outcome, suggesting that these cells may play a crucial role in the process of disease relapse. Cancer cell dormancy typically presents as growth arrest while retaining proliferative capacity and can be induced or reversed by a wide array of cell-intrinsic and cell-extrinsic factors. Conventional therapies preferentially target fast-dividing cells, leaving dormant cancer cells largely insensitive to these treatments. In this review, we discuss the role of dormant cancer cells in cancer recurrence and highlight how novel therapy strategies based on cell-cycle modulation, modifications of existing drugs, or enhanced drug-delivery vehicles may be used to specifically target this subpopulation of tumor cells, and thereby have the potential to prevent disease recurrence.

Receptor binding competition: A paradigm for regulating TGF-β family action

The transforming growth factor (TGF)-β family is a group of structurally related, multifunctional growth factors, or ligands that are crucially involved in the development, regulation, and maintenance of animal tissues. In humans, the family counts over 33 members. These secreted ligands typically form multimeric complexes with two type I and two type II receptors to activate one of two distinct signal transduction branches. A striking feature of the family is its promiscuity, i.e., many ligands bind the same receptors and compete with each other for binding to these receptors. Although several explanations for this feature have been considered, its functional significance has remained puzzling. However, several recent reports have promoted the idea that ligand-receptor binding promiscuity and competition are critical features of the TGF-β family that provide an essential regulating function. Namely, they allow a cell to read and process multi-ligand inputs. This capability may be necessary for producing subtle, distinctive, or adaptive responses and, possibly, for facilitating developmental plasticity. Here, we review the molecular basis for ligand competition, with emphasis on molecular structures and binding affinities. We give an overview of methods that were used to establish experimentally ligand competition. Finally, we discuss how the concept of ligand competition may be fundamentally tied to human physiology, disease, and therapy.

Activins as Dual Specificity TGF-β Family Molecules: SMAD-Activation via Activin- and BMP-Type 1 Receptors

Activins belong to the transforming growth factor (TGF)-β family of multifunctional cytokines and signal via the activin receptors ALK4 or ALK7 to activate the SMAD2/3 pathway. In some cases, activins also signal via the bone morphogenetic protein (BMP) receptor ALK2, causing activation of the SMAD1/5/8 pathway. In this study, we aimed to dissect how activin A and activin B homodimers, and activin AB and AC heterodimers activate the two main SMAD branches. We compared the activin-induced signaling dynamics of ALK4/7-SMAD2/3 and ALK2-SMAD1/5 in a multiple myeloma cell line. Signaling via the ALK2-SMAD1/5 pathway exhibited greater differences between ligands than signaling via ALK4/ALK7-SMAD2/3. Interestingly, activin B and activin AB very potently activated SMAD1/5, resembling the activation commonly seen with BMPs. As SMAD1/5 was also activated by activins in other cell types, we propose that dual specificity is a general mechanism for activin ligands. In addition, we found that the antagonist follistatin inhibited signaling by all the tested activins, whereas the antagonist cerberus specifically inhibited activin B. Taken together, we propose that activins may be considered dual specificity TGF-β family members, critically affecting how activins may be considered and targeted clinically.

A Multi-Omics Analysis of Bone Morphogenetic Protein 5 (BMP5) mRNA Expression and Clinical Prognostic Outcomes in Different Cancers Using Bioinformatics Approaches

Cumulative studies have provided controversial evidence for the prognostic values of bone morphogenetic protein 5 (BMP5) in different types of cancers such as colon, breast, lung, bladder, and ovarian cancer. To address the inconsistent correlation of BMP5 expression with patient survival and molecular function of BMP5 in relation to cancer progression, we performed a systematic study to determine whether BMP5 could be used as a prognostic marker in human cancers. BMP5 expression and prognostic values were assessed using different bioinformatics tools such as ONCOMINE, GENT, TCGA, GEPIA, UALCAN, PrognoScan, PROGgene V2 server, and Kaplan-Meier Plotter. In addition, we used cBioPortal database for the identification and analysis of BMP5 mutations, copy number alterations, altered expression, and protein-protein interaction (PPI). We found that BMP5 is frequently down-regulated in our queried cancer types. Use of prognostic analysis showed negative association of BMP5 down-regulation with four types of cancer except for ovarian cancer. The highest mutation was found in the R321*/Q amino acid of BMP5 corresponding to colorectal and breast cancer whereas the alteration frequency was higher in lung squamous carcinoma datasets (>4%). In PPI analysis, we found 31 protein partners of BMP5, among which 11 showed significant co-expression (p-value < 0.001, log odds ratio > 1). Pathway analysis of differentially co-expressed genes with BMP5 in breast, lung, colon, bladder and ovarian cancers revealed the BMP5-correlated pathways. Collectively, this data-driven study demonstrates the correlation of BMP5 expression with patient survival and identifies the involvement of BMP5 pathways that may serve as targets of a novel biomarker for various types of cancers in human.

Acute upregulation of bone morphogenetic protein-4 regulates endogenous cell response and promotes cell death in spinal cord injury

Traumatic spinal cord injury (SCI) elicits a cascade of secondary injury mechanisms that induce profound changes in glia and neurons resulting in their activation, injury or cell death. The resultant imbalanced microenvironment of acute SCI also negatively impacts regenerative processes in the injured spinal cord. Thus, it is imperative to uncover endogenous mechanisms that drive these acute injury events. Here, we demonstrate that the active form of bone morphogenetic protein-4 (BMP4) is robustly and transiently upregulated in acute SCI in rats. BMP4 is a key morphogen in neurodevelopment; however, its role in SCI is not fully defined. Thus, we elucidated the ramification of BMP4 upregulation in a preclinical model of compressive/contusive SCI in the rat by employing noggin, an endogenous antagonist of BMP ligands, and LDN193189, an intracellular inhibitor of BMP signaling. In parallel, we studied cell-specific effects of BMP4 on neural precursor cells (NPCs), oligodendrocyte precursor cells (OPCs), neurons and astrocytes in vitro. We demonstrate that activation of BMP4 inhibits differentiation of spinal cord NPCs and OPCs into mature myelin-expressing oligodendrocytes, and acute blockade of BMPs promotes oligodendrogenesis, oligodendrocyte preservation and remyelination after SCI. Importantly, we report for the first time that BMP4 directly induces caspase-3 mediated apoptosis in neurons and oligodendrocytes in vitro, and noggin and LDN193189 remarkably attenuate caspase-3 activation and lipid peroxidation in acute SCI. BMP4 also enhances the production of inhibitory chondroitin sulfate proteoglycans (CSPGs) in activated astrocytes in vitro and after SCI. Interestingly, our work reveals that despite the beneficial effects of BMP inhibition in acute SCI, neither noggin nor LDN193189 treatment resulted in long-term functional recovery. Collectively, our findings suggest a role for BMP4 in regulating acute secondary injury mechanisms following SCI, and a potential target for combinatorial approaches to improve endogenous cell response and remyelination.

Bone Morphogenetic Protein 4 Gene Therapy in Mice Inhibits Myeloma Tumor Growth, But Has a Negative Impact on Bone

Multiple myeloma is characterized by accumulation of malignant plasma cells in the bone marrow. Most patients suffer from an osteolytic bone disease, caused by increased bone degradation and reduced bone formation. Bone morphogenetic protein 4 (BMP4) is important for both pre‐ and postnatal bone formation and induces growth arrest and apoptosis of myeloma cells. BMP4‐treatment of myeloma patients could have the potential to reduce tumor growth and restore bone formation. We therefore explored BMP4 gene therapy in a human‐mouse model of multiple myeloma where humanized bone scaffolds were implanted subcutaneously in RAG2^−/− γC^−/−mice. Mice were treated with adeno‐associated virus serotype 8 BMP4 vectors (AAV8‐BMP4) to express BMP4 in the liver. When mature BMP4 was detectable in the circulation, myeloma cells were injected into the scaffolds and tumor growth was examined by weekly imaging. Strikingly, the tumor burden was reduced in AAV8‐BMP4 mice compared with the AAV8‐CTRL mice, suggesting that increased circulating BMP4 reduced tumor growth. BMP4‐treatment also prevented bone loss in the scaffolds, most likely due to reduced tumor load. To delineate the effects of BMP4 overexpression on bone per se, without direct influence from cancer cells, we examined the unaffected, non‐myeloma femurs by μCT. Surprisingly, the AAV8‐BMP4 mice had significantly reduced trabecular bone volume, trabecular numbers, as well as significantly increased trabecular separation compared with the AAV8‐CTRL mice. There was no difference in cortical bone parameters between the two groups. Taken together, BMP4 gene therapy inhibited myeloma tumor growth, but also reduced the amount of trabecular bone in mice. Our data suggest that care should be taken when considering using BMP4 as a therapeutic agent. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Transcriptomic profiling of the myeloma bone-lining niche reveals BMP signalling inhibition to improve bone disease

Multiple myeloma is an incurable, bone marrow-dwelling malignancy that disrupts bone homeostasis causing skeletal damage and pain. Mechanisms underlying myeloma-induced bone destruction are poorly understood and current therapies do not restore lost bone mass. Using transcriptomic profiling of isolated bone lining cell subtypes from a murine myeloma model, we find that bone morphogenetic protein (BMP) signalling is upregulated in stromal progenitor cells. BMP signalling has not previously been reported to be dysregulated in myeloma bone disease. Inhibition of BMP signalling in vivo using either a small molecule BMP receptor antagonist or a solubilized BMPR1a-FC receptor ligand trap prevents trabecular and cortical bone volume loss caused by myeloma, without increasing tumour burden. BMP inhibition directly reduces osteoclastogenesis, increases osteoblasts and bone formation, and suppresses bone marrow sclerostin levels. In summary we describe a novel role for the BMP pathway in myeloma-induced bone disease that can be therapeutically targeted.

Hyaluronan hydrogels delivering BMP-6 for local targeting of malignant plasma cells and osteogenic differentiation of mesenchymal stromal cells

Multiple myeloma is a malignant disease characterized by accumulation of clonal plasma cells in the bone marrow. Uncoupling of bone formation and resorption by myeloma cells leads to osteolytic lesions. These are prone to fracture and represent a possible survival space for myeloma cells under treatment causing disease relapse. Here we report on a novel approach suitable for local treatment of multiple myeloma based on hyaluronic acid (HA) hydrogels mimicking the physical properties of the bone marrow. The HA hydrogels are complexed with heparin to achieve sustained presentation and controlled release of bone morphogenetic protein 6 (BMP-6). Others and we have shown that BMP-6 induces myeloma cell apoptosis and bone formation. Using quartz crystal microbalance and enzyme-linked immunosorbent assay, we measured an initial surface density of 400 ng BMP6/cm², corresponding to two BMP-6 per heparin molecule, with 50% release within two weeks. HA-hydrogels presenting BMP-6 enhanced the phosphorylation of Smad 1/5 while reducing the activity of BMP-6 antagonist sclerostin. These materials induced osteogenic differentiation of mesenchymal stromal cells and decreased the viability of myeloma cell lines and primary myeloma cells. BMP-6 functionalized HA-hydrogels represent a promising material for local treatment of myeloma-induced bone disease and residual myeloma cells within lesions to minimize disease relapse or fractures. STATEMENT OF SIGNIFICANCE: Multiple myeloma is a hematological cancer characterized by the accumulation of clonal plasma cells in the bone marrow and local suppression of bone formation, resulting in osteolytic lesions and fractures. Despite recent advances in systemic treatment of multiple myeloma, it is rare to achieve a targeted suppression of myeloma cells and healing of bone lesions. Here we present hydrogels which mimic the physico-chemical properties of the bone marrow, consisting of hyaluronic acid with crosslinked heparin for the controlled presentation of bioactive BMP-6. The hydrogels decrease the viability of myeloma cell lines and primary myeloma cells and induces osteogenic differentiation of mesenchymal stromal cells. The presentation of BMP-6 in the hyaluronan hydrogels enhances the phosphorylation of Smad1/5 while reducing the activity of the BMP-6 antagonist sclerostin. As such, BMP-6 functionalized hyaluronan hydrogels represent a promising material for the localized eradication of myeloma cells.

Wnt5a induces and maintains prostate cancer cells dormancy in bone

Wnt5a from osteoblastic niche induces and maintains the dormancy of prostate cancer cells in bone and inhibits bone metastasis in a preventive manner, uncovering a potential therapeutic utility of Wnt5a in the treatment of bone metastatic prostate cancer.

In a substantial fraction of prostate cancer (PCa) patients, bone metastasis appears after years or even decades of latency. Canonical Wnt/β-catenin signaling has been proposed to be implicated in dormancy of cancer cells. However, how these tumor cells are kept dormant and recur under control of Wnt/β-catenin signaling derived from bone microenvironment remains unknown. Here, we report that Wnt5a from osteoblastic niche induces dormancy of PCa cells in a reversible manner in vitro and in vivo via inducing Siah E3 Ubiquitin Protein Ligase 2 (SIAH2) expression, which represses Wnt/β-catenin signaling. Furthermore, this effect of Wnt5a-induced dormancy of PCa cells depends on receptor tyrosine kinase-like orphan receptor 2 (ROR2), and a negative correlation of ROR2 expression with bone metastasis–free survival is observed in PCa patients. Therefore, these results demonstrate that Wnt5a/ROR2/SIAH2 signaling axis plays a crucial role in inducing and maintaining PCa cells dormancy in bone, suggesting a potential therapeutic utility of Wnt5a via inducing dormancy of PCa cells in bone.

Alteration of tumor suppressor BMP5 in sporadic colorectal cancer: a genomic and transcriptomic profiling based study

Background

Although the genetic spectrum of human colorectal cancer (CRC) is mainly characterized by APC, KRAS and TP53 mutations, driver genes in tumor initiation have not been conclusively demonstrated. In this study, we aimed to identify novel markers for CRC.

Methods

We performed exome analysis of sporadic colorectal cancer (sCRC) coding regions to screen loss of function (LoF) mutation genes, and carried out systems-level approaches to confirm top rank gene in this study.

Results

We identified loss of BMP5 is an early event in CRC. Deep sequencing identified BMP5 was mutated in 7.7% (8/104) of sCRC samples, with 37.5% truncating mutation frequency. Notably, BMP5 negative expression and its prognostic value is uniquely significant in sCRC but not in other tumor types. Furthermore, BMP5 expression was positively correlated with E-cadherin in CRC patients and its dysregulation play a vital role in epithelial-mesenchymal transition (EMT), thus triggering tumor initiation and development. RNA sequencing identified, independent of BMP/Smads pathway, BMP5 signaled though Jak-Stat pathways to inhibit the activation of oncogene EPSTI1.

Conclusions

Our result support a novel concept that the importance of BMP5 in sCRC. The tumor suppressor role of BMP5 highlights its crucial role in CRC initiation and development.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0925-7) contains supplementary material, which is available to authorized users.

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.

BMPR2 inhibits activin and BMP signaling via wild-type ALK2

TGF-β/BMP superfamily ligands require heteromeric complexes of type 1 and 2 receptors for ligand-dependent downstream signaling. Activin A, a TGF-β superfamily member, inhibits growth of multiple myeloma cells, but the mechanism for this is unknown. We therefore aimed to clarify how activins affect myeloma cell survival. Activin A activates the transcription factors SMAD2/3 through the ALK4 type 1 receptor, but may also activate SMAD1/5/8 through mutated variants of the type 1 receptor ALK2 (also known as ACVR1). We demonstrate that activin A and B activate SMAD1/5/8 in myeloma cells through endogenous wild-type ALK2. Knockdown of the type 2 receptor BMPR2 strongly potentiated activin A- and activin B-induced activation of SMAD1/5/8 and subsequent cell death. Furthermore, activity of BMP6, BMP7 or BMP9, which may also signal via ALK2, was potentiated by knockdown of BMPR2. Similar results were seen in HepG2 liver carcinoma cells. We propose that BMPR2 inhibits ALK2-mediated signaling by preventing ALK2 from oligomerizing with the type 2 receptors ACVR2A and ACVR2B, which are necessary for activation of ALK2 by activins and several BMPs. In conclusion, BMPR2 could be explored as a possible target for therapy in patients with multiple myeloma.This article has an associated First Person interview with the first author of the paper.

The anti-myeloma activity of bone morphogenetic protein 2 predominantly relies on the induction of growth arrest and is apoptosis-independent

Multiple myeloma (MM), a malignancy of the bone marrow, is characterized by a pathological increase in antibody-producing plasma cells and an increase in immunoglobulins (plasmacytosis). In recent years, bone morphogenetic proteins (BMPs) have been reported to be activators of apoptotic cell death in neoplastic B cells in MM. Here, we use bone morphogenetic protein 2 (BMP2) to show that the "apoptotic" effect of BMPs on human neoplastic B cells is dominated by anti-proliferative activities and cell cycle arrest and is apoptosis-independent. The anti-proliferative effect of BMP2 was analysed in the human cell lines KMS12-BM and L363 using WST-1 and a Coulter counter and was confirmed using CytoTox assays with established inhibitors of programmed cell death (zVAD-fmk and necrostatin-1). Furthermore, apoptotic activity was compared in both cell lines employing western blot analysis for caspase 3 and 8 in cells treated with BMP2 and FasL. Additionally, expression profiles of marker genes of different cell death pathways were analysed in both cell lines after stimulation with BMP2 for 48h using an RT-PCR-based array. In our experiments we observed that there was rather no reduction in absolute cell number, but cells stopped proliferating following treatment with BMP2 instead. The time frame (48–72 h) after BMP2 treatment at which a reduction in cell number is detectable is too long to indicate a directly BMP2-triggered apoptosis. Moreover, in comparison to robust apoptosis induced by the approved apoptotic factor FasL, BMP2 only marginally induced cell death. Consistently, neither the known inhibitor of apoptotic cell death zVAD-fmk nor the necroptosis inhibitor necrostatin-1 was able to rescue myeloma cell growth in the presence of BMP2.

BMP-7 induces apoptosis in human germinal center B cells and is influenced by TGF-β receptor type I ALK5

Selection and maturation of B cells into plasma cells producing high-affinity antibodies occur in germinal centers (GC). GCs form transiently in secondary lymphoid organs upon antigen challenge, and the GC reaction is a highly regulated process. TGF-β is a potent negative regulator, but the influence of other family members including bone morphogenetic proteins (BMPs) is less known. Studies of human peripheral blood B lymphocytes showed that BMP-6 suppressed plasmablast differentiation, whereas BMP-7 induced apoptosis. Here, we show that human naïve and GC B cells had a strikingly different receptor expression pattern. GC B cells expressed high levels of BMP type I receptor but low levels of type II receptors, whereas naïve B cells had the opposite pattern. Furthermore, GC B cells had elevated levels of downstream signaling components SMAD1 and SMAD5, but reduced levels of the inhibitory SMAD7. Functional assays of GC B cells revealed that BMP-7 suppressed the viability-promoting effect of CD40L and IL-21, but had no effect on CD40L- and IL-21-induced differentiation into plasmablasts. BMP-7-induced apoptosis was counteracted by a selective TGF-β type I receptor (ALK4/5/7) inhibitor, but not by a selective BMP receptor type I inhibitor. Furthermore, overexpression of truncated ALK5 in a B-cell line counteracted BMP-7-induced apoptosis, whereas overexpression of truncated ALK4 had no effect. BMP-7 mRNA and protein was readily detected in tonsillar B cells, indicating a physiological relevance of the study. Altogether, we identified BMP-7 as a negative regulator of GC B-cell survival. The effect was counteracted by truncated ALK5, suggesting greater complexity in regulating BMP-7 signaling than previously believed.

Utilizing BMP-2 muteins for treatment of multiple myeloma

Multiple myeloma (MM) represents a haematological cancer characterized by the pathological hyper proliferation of antibody-producing B-lymphocytes. Patients typically suffer from kidney malfunction and skeletal disorders. In the context of MM, the transforming growth factor β (TGFβ) member Activin A was recently identified as a promoter of both accompanying symptoms. Because studies have shown that bone morphogenetic protein (BMP)-2-mediated activities are counteracted by Activin A, we analysed whether BMP2, which also binds to the Activin A receptors ActRII and ActRIIB but activates the alternative SMAD-1/5/8 pathway, can be used to antagonize Activin A activities, such as in the context of MM. Therefore three BMP2 derivatives were generated with modified binding activities for the type II (ActRIIB) and/or type I receptor (BMPRIA) showing either increased or decreased BMP2 activity. In the context of MM these BMP2 muteins show two functionalities since they act as a) an anti-proliferative/apoptotic agent against neoplastic B-cells, b) as a bone-formation promoting growth factor. The molecular basis of both activities was shown in two different cellular models to clearly rely on the properties of the investigated BMP2 muteins to compete for the binding of Activin A to the Activin type II receptors. The experimental outcome suggests new therapeutic strategies using BMP2 variants in the treatment of MM-related pathologies.

Bmp5 Regulates Neural Crest Cell Survival and Proliferation via Two Different Signaling Pathways

Neural crest progenitor cells, which give rise to many ectodermal and mesodermal derivatives, must maintain a delicate balance of apoptosis and proliferation for their final tissue contributions. Here we show that zebrafish bmp5 is expressed in neural crest progenitor cells and that it activates the Smad and Erk signaling pathways to regulate cell survival and proliferation, respectively. Loss-of-function analysis showed that Bmp5 was required for cell survival and this response is mediated by the Smad-Msxb signaling cascade. However, the Bmp5-Smad-Msxb signaling pathway had no effect on cell proliferation. In contrast, Bmp5 was sufficient to induce cell proliferation through the Mek-Erk-Id3 signaling cascade, whereas disruption of this signaling cascade had no effect on cell survival. Taken together, our results demonstrate an important regulatory mechanism for bone morphogenic protein-initiated signal transduction underlying the formation of neural crest progenitors. Stem Cells 2017;35:1003-1014.

TGF-beta receptor mediated telomerase inhibition, telomere shortening and breast cancer cell senescence

Human telomerase reverse transcriptase (hTERT) plays a central role in telomere lengthening for continuous cell proliferation, but it remains unclear how extracellular cues regulate telomerase lengthening of telomeres. Here we report that the cytokine bone morphogenetic protein-7 (BMP7) induces the hTERT gene repression in a BMPRII receptor- and Smad3-dependent manner in human breast cancer cells. Chonic exposure of human breast cancer cells to BMP7 results in short telomeres, cell senescence and apoptosis. Mutation of the BMPRII receptor, but not TGFbRII, ACTRIIA or ACTRIIB receptor, inhibits BMP7-induced repression of the hTERT gene promoter activity, leading to increased telomerase activity, lengthened telomeres and continued cell proliferation. Expression of hTERT prevents BMP7-induced breast cancer cell senescence and apoptosis. Thus, our data suggest that BMP7 induces breast cancer cell aging by a mechanism involving BMPRII receptor- and Smad3-mediated repression of the hTERT gene.

Bone metastasis: the importance of the neighbourhood

During the past decade preclinical studies have defined many of the mechanisms used by tumours to hijack the skeleton and promote bone metastasis. This has led to the development and widespread clinical use of bone-targeted drugs to prevent skeletal-related events. This understanding has also identified a critical dependency between colonizing tumour cells and the cells of bone. This is particularly important when tumour cells first arrive in bone, adapt to their new microenvironment and enter a long-lived dormant state. In this Review, we discuss the role of different bone cell types in supporting disseminated tumour cell dormancy and reactivation, and highlight the new opportunities this provides for targeting the bone microenvironment to control dormancy and bone metastasis.

Osteoclasts control reactivation of dormant myeloma cells by remodelling the endosteal niche

Multiple myeloma is largely incurable, despite development of therapies that target myeloma cell-intrinsic pathways. Disease relapse is thought to originate from dormant myeloma cells, localized in specialized niches, which resist therapy and repopulate the tumour. However, little is known about the niche, and how it exerts cell-extrinsic control over myeloma cell dormancy and reactivation. In this study, we track individual myeloma cells by intravital imaging as they colonize the endosteal niche, enter a dormant state and subsequently become activated to form colonies. We demonstrate that dormancy is a reversible state that is switched ‘on' by engagement with bone-lining cells or osteoblasts, and switched ‘off' by osteoclasts remodelling the endosteal niche. Dormant myeloma cells are resistant to chemotherapy that targets dividing cells. The demonstration that the endosteal niche is pivotal in controlling myeloma cell dormancy highlights the potential for targeting cell-extrinsic mechanisms to overcome cell-intrinsic drug resistance and prevent disease relapse.

Therapy resistant dormant myeloma cells contribute to disease relapse. Here, the authors use intravital microscopy to track the location of these cells and demonstrate that they hone to the endosteal niche within the bone.

Activin A inhibits BMP-signaling by binding ACVR2A and ACVR2B

Background

Activins are members of the TGF-β family of ligands that have multiple biological functions in embryonic stem cells as well as in differentiated tissue. Serum levels of activin A were found to be elevated in pathological conditions such as cachexia, osteoporosis and cancer. Signaling by activin A through canonical ALK4-ACVR2 receptor complexes activates the transcription factors SMAD2 and SMAD3. Activin A has a strong affinity to type 2 receptors, a feature that they share with some of the bone morphogenetic proteins (BMPs). Activin A is also elevated in myeloma patients with advanced disease and is involved in myeloma bone disease.

Results

In this study we investigated effects of activin A binding to receptors that are shared with BMPs using myeloma cell lines with well-characterized BMP-receptor expression and responses. Activin A antagonized BMP-6 and BMP-9, but not BMP-2 and BMP-4. Activin A was able to counteract BMPs that signal through the type 2 receptors ACVR2A and ACVR2B in combination with ALK2, but not BMPs that signal through BMPR2 in combination with ALK3 and ALK6.

Conclusions

We propose that one important way that activin A regulates cell behavior is by antagonizing BMP-ACVR2A/ACVR2B/ALK2 signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-015-0104-z) contains supplementary material, which is available to authorized users.

Bone Regeneration Using Bone Morphogenetic Proteins and Various Biomaterial Carriers

Trauma and disease frequently result in fractures or critical sized bone defects and their management at times necessitates bone grafting. The process of bone healing or regeneration involves intricate network of molecules including bone morphogenetic proteins (BMPs). BMPs belong to a larger superfamily of proteins and are very promising and intensively studied for in the enhancement of bone healing. More than 20 types of BMPs have been identified but only a subset of BMPs can induce de novo bone formation. Many research groups have shown that BMPs can induce differentiation of mesenchymal stem cells and stem cells into osteogenic cells which are capable of producing bone. This review introduces BMPs and discusses current advances in preclinical and clinical application of utilizing various biomaterial carriers for local delivery of BMPs to enhance bone regeneration.

A peculiar molecular profile of umbilical cord-mesenchymal stromal cells drives their inhibitory effects on multiple myeloma cell growth and tumor progression

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are under intensive investigation in preclinical models of cytotherapies against cancer, including multiple myeloma (MM). However, the therapeutic use of stromal progenitors holds critical safety concerns due to their potential MM-supporting activity in vivo. Here, we explored whether MSCs from sources other than BM, such as adipose tissue (AD-MSCs) and umbilical cord (UC-MSCs), affect MM cell growth in comparison to either normal (nBM-MSCs) or myelomatous marrow MSCs (MM-BM-MSCs). Results from both proliferation and clonogenic assays indicated that, in contrast to nBM- and MM-BM-MSCs, both AD and particularly UC-MSCs significantly inhibit MM cell clonogenicity and growth in vitro. Furthermore, when co-injected with UC-MSCs into mice, RPMI-8226 MM cells formed smaller subcutaneous tumor masses, while peritumoral injections of the same MSC subtype significantly delayed the tumor burden growing in subcutaneous plasmocytoma-bearing mice. Finally, both microarrays and ELISA revealed different expression of several genes and soluble factors in UC-MSCs as compared with other MSCs. Our data suggest that UC-MSCs have a distinct molecular profile that correlates with their intrinsic anti-MM activity and emphasize the UCs as ideal sources of MSCs for future cell-based therapies against MM.

The role of bone morphogenetic proteins in myeloma cell survival

Multiple myeloma is characterized by slowly growing clones of malignant plasma cells in the bone marrow. The malignant state is frequently accompanied by osteolytic bone disease due to a disturbed balance between osteoblasts and osteoclasts. Bone morphogenetic proteins (BMPs) are present in the bone marrow and are important for several aspects of myeloma pathogenesis including growth and survival of tumor cells, bone homeostasis, and anemia. Among cancer cells, myeloma cells are particularly sensitive to growth inhibition and apoptosis induced by BMPs and therefore represent good models to study BMP receptor usage and signaling. Our review highlights and discusses the current knowledge on BMP signaling in myeloma.

Multiple myeloma exacerbation following utilization of bone morphogenetic protein-2 in lateral lumbar interbody fusion: a case report and review of the literature

BACKGROUND CONTEXT

Recent studies generated antithetic results regarding the safety of bone morphogenetic protein-2 (BMP-2) use in spine surgery, and the effect of this biologic adjunct on myeloma cells remains to be fully elucidated.

PURPOSE

The purpose of this study was to present a case of multiple myeloma (MM) exacerbation after BMP-2 implantation in the setting of lateral lumbar interbody fusion (LLIF).

STUDY DESIGN

Case report and literature review.

METHODS

The medical records, laboratory findings, and radiographic imaging studies of an 86-year-old female patient with exacerbation of previously undiagnosed MM were reviewed.

RESULTS

The patient presented with a 10-year history of debilitating lower back pain and bilateral lower extremity claudication. Radiographic studies depicted lumbar scoliosis and lateral spondylolisthesis. Preoperative serum immunofixation electrophoresis showed a serum immunoglobulin A kappa paraprotein-peak; however, the patient had never been diagnosed with MM or reported any unexplained fever, night sweats, or weight loss indicative of MM. The patient underwent LLIF from L1-L5 supplemented by BMP-2. On postoperative day 1, the patient was evaluated by the hematology department for paraproteinemia. Serum electrophoresis showed decreased albumin, hypogammaglobulinemia, and suspicious broadening of the complement component in the beta region. Postoperative imaging studies (19 weeks) depicted progression of a previously visible intraosseous lesion, and anterior cortical breakthrough (L5), in addition to a soft tissue mass at the T10 level. Histological examination of iliac crest and T10 vertebral biopsies showed fatty marrow infiltration by plasma cells and plasma cell dyscrasia, proving the diagnosis of MM. The patient died 10 months after surgery due to complications related to a methicillin-resistant Staphylococcus aureus infection.

CONCLUSIONS

Based on the present case, perhaps one should consider that in patients with abnormal electrophoresis results, even in the absence of a prior diagnosis of MM as well as in the absence of symptoms indicative of MM, BMPs should be administered only after preoperative exclusion of neoplastic disease.

Bone morphogenetic protein-9 suppresses growth of myeloma cells by signaling through ALK2 but is inhibited by endoglin

Multiple myeloma is a malignancy of plasma cells predominantly located in the bone marrow. A number of bone morphogenetic proteins (BMPs) induce apoptosis in myeloma cells in vitro, and with this study we add BMP-9 to the list. BMP-9 has been found in human serum at concentrations that inhibit cancer cell growth in vitro. We here show that the level of BMP-9 in serum was elevated in myeloma patients (median 176 pg/ml, range 8–809) compared with healthy controls (median 110 pg/ml, range 8–359). BMP-9 was also present in the bone marrow and was able to induce apoptosis in 4 out of 11 primary myeloma cell samples by signaling through ALK2. BMP-9-induced apoptosis in myeloma cells was associated with c-MYC downregulation. The effects of BMP-9 were counteracted by membrane-bound (CD105) or soluble endoglin present in the bone marrow microenvironment, suggesting a mechanism for how myeloma cells can evade the tumor suppressing activity of BMP-9 in multiple myeloma.

Role of Smad proteins in resistance to BMP-induced growth inhibition in B-cell lymphoma

Bone morphogenetic protein (BMP) expression and signaling are altered in a variety of cancers, but the functional impact of these alterations is uncertain. In this study we investigated the impact of expression of multiple BMPs and their signaling pathway components in human B-cell lymphoma. BMP messages, in particular BMP7, were detected in normal and malignant B cells. Addition of exogenous BMPs inhibited DNA synthesis in most lymphoma cell lines examined, but some cell lines were resistant. Tumor specimens from three out of five lymphoma patients were also resistant to BMPs, as determined by no activation of the BMP effectors Smad1/5/8. We have previously shown that BMP-7 potently induced apoptosis in normal B cells, which was in contrast to no or little inhibitory effect of this BMP in the lymphoma cells tested. BMP-resistance mechanisms were investigated by comparing sensitive and resistant cell lines. While BMP receptors are downregulated in many cancers, we documented similar receptor levels in resistant and sensitive lymphoma cells. We found a positive correlation between activation of Smad1/5/8 and inhibition of DNA synthesis. Gene expression analysis of two independent data sets showed that the levels of inhibitory Smads varied across different B-cell lymphoma. Furthermore, stable overexpression of Smad7 in two different BMP-sensitive cell lines with low endogenous levels of SMAD7, rendered them completely resistant to BMPs. This work highlights the role of Smads in determining the sensitivity to BMPs and shows that upregulation of Smad7 in cancer cells is sufficient to escape the negative effects of BMPs.

BMPs and their clinical potentials

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

Bone morphogenetic proteins induce apoptosis in multiple myeloma cells by Smad-dependent repression of MYC

Bone morphogenetic proteins (BMPs) have been shown to induce apoptosis and growth arrest in myeloma cells. However, the molecular mechanisms behind these events are not known. The MYC oncogene is a master regulator of cell growth and protein synthesis and MYC overexpression has been proposed to be associated with the progression of multiple myeloma. Here, we show that BMP-induced apoptosis in myeloma cells is dependent on downregulation of MYC. Moreover, the results suggest that targeting the MYC addiction in multiple myeloma is an efficient way of killing a majority of primary myeloma clones. We also found that myeloma cells harboring immunoglobulin (IG)-MYC translocations evaded BMP-induced apoptosis, suggesting a novel way for myeloma cells to overcome potential tumor suppression by BMPs.

Imaging bone morphogenetic protein 7 induced cell cycle arrest in experimental gliomas

Bone morphogenetic protein 7 (BMP-7) belongs to the superfamily of transforming growth factor β-like cytokines, which can act either as tumor suppressors or as tumor promoters depending on cell type and differentiation. Our investigations focused on analyzing the effects of BMP-7 during glioma cell proliferation in vitro and in vivo. BMP-7 treatment decreased the proliferation of Gli36ΔEGFR-LITG glioma cells up to 50%through a cell cycle arrest in the G(1) phase but not by induction of apoptosis. This effect was mediated by the modulation of the expression and phosphorylation of cyclin-dependent kinase 2, cyclin-dependent kinase inhibitor p21, and downstream retinoblastoma protein. Furthermore, in vivo optical imaging of luciferase activity of Gli36ΔEGFR-LITG cells implanted intracranially into nude mice in the presence or absence of BMP-7 treatment corroborated the antiproliferative effects of this cytokine. This report clearly underlines the tumor-suppressive role of BMP-7 in glioma-derived cells. Taken together, our results indicate that manipulating the BMP/transforming growth factor β signaling cascade may serve as a new strategy for imaging-guided molecular-targeted therapy of malignant gliomas.

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

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

Expression of BMP-7 in human gastric cancer and its clinical significance. Br J Cancer. 2011;104:714-718. [PMID: 21224856 DOI: 10.1038/sj.bjc.6606075]

BACKGROUND

Bone morphogenetic protein-7 (BMP-7) is a signalling molecule belonging to the transforming growth factor--superfamily. Recent studies have demonstrated the clinical impact of BMP-7 expression in various human cancers. However, there have been few reports detailing this in gastric cancer.

METHODS

We immunohistochemically investigated the expression of BMP-7 in 233 gastric cancer patients to disclose the clinicopathological features of BMP-7-positive gastric cancer.

RESULTS

Immunohistochemically, in human gastric cancer, BMP-7 expression was identified in cellular membranes but also in the cytoplasm of cancer cells. Bone morphogenetic protein-7-positive expression was found in 129 of 233 patients (55%). Bone morphogenetic protein-7 expression was correlated with tumour size, nodal involvement, lymphatic invasion, venous invasion and histology (P<0.05). Bone morphogenetic protein-7 expression was significantly correlated with patient postoperative outcome, especially in the undifferentiated group. Multivariate analysis revealed BMP-7 expression as one of the independent prognostic factors next to the depth of invasion and nodal involvement (P<0.01).

CONCLUSIONS

From the data collected, it would be appropriate to conclude on the possible regulation of gastric cancer progression by autocrine or paracrine BMP-7 loops. We can use BMP-7 expression as one of the strong predictors of risk of tumour recurrence in gastric cancer.

Molecular pathogenesis of multiple myeloma: chromosomal aberrations, changes in gene expression, cytokine networks, and the bone marrow microenvironment

This chapter focuses on two aspects of myeloma pathogenesis: (1) chromosomal aberrations and resulting changes in gene and protein expression with a special focus on growth and survival factors of malignant (and normal) plasma cells and (2) the remodeling of the bone marrow microenvironment induced by accumulating myeloma cells. We begin this chapter with a discussion of normal plasma cell generation, their survival, and a novel class of inhibitory factors. This is crucial for the understanding of multiple myeloma, as several abilities attributed to malignant plasma cells are already present in their normal counterpart, especially the production of survival factors and interaction with the bone marrow microenvironment (niche). The chapter closes with a new model of pathogenesis of myeloma.

Bone morphogenetic protein 4 (BMP4) signaling in retinoblastoma cells

Bone morphogenetic proteins (BMPs) - expressed in the developing retina - are known to be involved in the regulation of cell proliferation and apoptosis in several tumor entities. The objective of this study was to determine the role of the BMP4 pathway in retinoblastoma cells, which are absent in a functional retinoblastoma (RB1) gene. BMP receptors were detected in all retinoblastoma cell lines investigated. A correct transmission of BMP signaling via the Smad1/5/8 pathway could be demonstrated in WERI-Rb1 retinoblastoma cells and application of recombinant human BMP4 resulted in an increase in apoptosis, which to a large extend is caspase independent. Cell proliferation was not affected by BMP4 signaling, although the pRb-related proteins p107 and p130, contributing to the regulation of the same genes, are still expressed. WERI-Rb1 cells exhibit elevated endogenous levels of p21(CIP1) and p53, but we did not detect any increase in p53, p21(CIP1)or p27(KIP1) expression levels. Id proteins became, however, strongly up-regulated upon exogenous BMP4 treatment. Thus, RB1 loss in WERI-Rb1 cells is obviously not compensated for by pRb-independent (e.g. p53-dependent) cell cycle control mechanisms, preventing an anti-proliferative response to BMP4, which normally induces cell cycle arrest.

The canonical BMP signaling pathway is involved in human monocyte-derived dendritic cell maturation

Bone morphogenetic proteins (BMPs), members of the transforming growth factor-β superfamily, are multifunctional polypeptides regulating a broad spectrum of functions in embryonic and adult tissues. Recent reports have demonstrated that BMPs regulate the survival, proliferation and differentiation of several cell types in the immune system. In this study, we investigate the effects of BMP signaling activation on the capacity of human dendritic cells (DCs) to stimulate immune responses. Human DCs express type I and type II BMP receptors (BMPRIA, BMPRIB, type IA activin receptor, BMPRII) and BMP signal transduction molecules (Smad1, 5, and 8, as well as Smad4). On BMP stimulation, Id1-3 (inhibitor of differentiation 1-3/DNA binding) mRNA expression is upregulated and this effect can be blocked with the inhibitor dorsomorphin, showing that the canonical BMP signal transduction pathway is functionally active in DCs. BMP signaling activation promotes the phenotypic maturation of human DCs by increasing the expression of co-stimulatory molecules and also CD83, programmed cell death ligand 1 (PD-L1) and PD-L2, and stimulates cytokine secretion, mainly interleukin-8 and tumor necrosis factor-α. Accordingly, BMP-treated DCs exhibit an enhanced T-cell stimulatory capacity. BMP signaling also enhances the survival of human DCs increasing the Bcl-2/Bax ratio. Finally, the expression of Runx transcription factors is increased in mature DCs, and the mRNA levels of Runx1-3 are upregulated in response to BMP stimulation, indicating that Runx transcription factor family may mediate the effects of BMP signaling in human DC maturation.

Bone morphogenetic proteins: a critical review. Cell Signal. 2011;23:609-620. [PMID: 20959140 DOI: 10.1016/j.cellsig.2010.10.003]

Bone Morphogenetic Proteins (BMPs) are potent growth factors belonging to the Transforming Growth Factor Beta superfamily. To date over 20 members have been identified in humans with varying functions during processes such as embryogenesis, skeletal formation, hematopoiesis and neurogenesis. Though their functions have been identified, less is known regarding levels of regulation at the extracellular matrix, membrane surface, and receptor activation. Further, current models of activation lack the integration of these regulatory mechanisms. This review focuses on the different levels of regulation, ranging from the release of BMPs into the extracellular components to receptor activation for different BMPs. It also highlights areas in research that is lacking or contradictory.

CpG-oligodeoxynucleotide inhibits Smad-dependent bone morphogenetic protein signaling: effects on myeloma cell apoptosis and in vitro osteoblastogenesis

The TLR9 agonist CpG-oligodeoxynucleotide (CpG-ODN) with a phosphorothioate backbone (PTO-CpG-ODN) is evaluated in clinical trials as a vaccine adjuvant or as treatment of cancers. Bone morphogenetic proteins (BMPs) regulate growth and differentiation of several cell types, and also induce apoptosis of cancer cells. Cross-talk between BMP- and TLR-signaling has been reported, and we aimed to investigate whether CpG-ODN influenced BMP-induced osteoblast differentiation or BMP-induced apoptosis of malignant plasma cells. We found that PTO-CpG-ODN inhibited BMP-2-induced osteoblast differentiation from human mesenchymal stem cells. Further, PTO-CpG-ODN counteracted BMP-2- and BMP-6-induced apoptosis of the human myeloma cell lines IH-1 and INA-6, respectively. In contrast, PTO-CpG-ODN did not antagonize the antiproliferative effect of BMP-2 on hMSCs or IH-1 cells. Inhibition of Smad-signaling and p38 MAPK-signaling indicated that apoptosis of IH-1 cells is dependent on Smad-signaling downstream of BMP, whereas the antiproliferative effect of BMP-2 on IH-1 cells also involves p38 MAPK-signaling. Together, the data suggested a specific inhibition by PTO-CpG-ODN on BMP-Smad-signaling. Supporting this we found that PTO-CpG-ODN inhibited BMP-induced phosphorylation of receptor-Smads in human mesenchymal stem cells and myeloma cell lines. This effect appeared to be independent of TLR9 because GpC-ODN and other ODNs with the ability to form multimeric structures inhibited Smad-signaling as efficiently as PTO-CpG-ODNs, and because knockdown of TLR9 by small interfering RNA in INA-6 cells did not blunt the effect of PTO-CpG-ODN. In conclusion, our results demonstrate that PTO-CpG-ODN inhibits BMP-signaling, and thus might provoke unwanted TLR9-independent side effects in patients.

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.