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

Systematic Review of Molecular Targeted Therapies for Adult-Type Diffuse Glioma: An Analysis of Clinical and Laboratory Studies

Gliomas are the most common brain tumor in adults, and molecularly targeted therapies to treat gliomas are becoming a frequent topic of investigation. The current state of molecular targeted therapy research for adult-type diffuse gliomas has yet to be characterized, particularly following the 2021 WHO guideline changes for classifying gliomas using molecular subtypes. This systematic review sought to characterize the current state of molecular target therapy research for adult-type diffuse glioma to better inform scientific progress and guide next steps in this field of study. A systematic review was conducted in accordance with PRISMA guidelines. Studies meeting inclusion criteria were queried for study design, subject (patients, human cell lines, mice, etc.), type of tumor studied, molecular target, respective molecular pathway, and details pertaining to the molecular targeted therapy-namely the modality, dose, and duration of treatment. A total of 350 studies met the inclusion criteria. A total of 52 of these were clinical studies, 190 were laboratory studies investigating existing molecular therapies, and 108 were laboratory studies investigating new molecular targets. Further, a total of 119 ongoing clinical trials are also underway, per a detailed query on clinicaltrials.gov. GBM was the predominant tumor studied in both ongoing and published clinical studies as well as in laboratory analyses. A few studies mentioned IDH-mutant astrocytomas or oligodendrogliomas. The most common molecular targets in published clinical studies and clinical trials were protein kinase pathways, followed by microenvironmental targets, immunotherapy, and cell cycle/apoptosis pathways. The most common molecular targets in laboratory studies were also protein kinase pathways; however, cell cycle/apoptosis pathways were the next most frequent target, followed by microenvironmental targets, then immunotherapy pathways, with the wnt/β-catenin pathway arising in the cohort of novel targets. In this systematic review, we examined the current evidence on molecular targeted therapy for adult-type diffuse glioma and discussed its implications for clinical practice and future research. Ultimately, published research falls broadly into three categories-clinical studies, laboratory testing of existing therapies, and laboratory identification of novel targets-and heavily centers on GBM rather than IDH-mutant astrocytoma or oligodendroglioma. Ongoing clinical trials are numerous in this area of research as well and follow a similar pattern in tumor type and targeted pathways as published clinical studies. The most common molecular targets in all study types were protein kinase pathways. Microenvironmental targets were more numerous in clinical studies, whereas cell cycle/apoptosis were more numerous in laboratory studies. Immunotherapy pathways are on the rise in all study types, and the wnt/β-catenin pathway is increasingly identified as a novel target.

Modeling cartilage pathology in mucopolysaccharidosis VI using iPSCs reveals early dysregulation of chondrogenic and metabolic gene expression

Mucopolysaccharidosis type VI (MPS VI) is a metabolic disorder caused by disease-associated variants in the Arylsulfatase B (ARSB) gene, resulting in ARSB enzyme deficiency, lysosomal glycosaminoglycan accumulation, and cartilage and bone pathology. The molecular response to MPS VI that results in cartilage pathology in human patients is largely unknown. Here, we generated a disease model to study the early stages of cartilage pathology in MPS VI. We generated iPSCs from four patients and isogenic controls by inserting the ARSB cDNA in the AAVS1 safe harbor locus using CRISPR/Cas9. Using an optimized chondrogenic differentiation protocol, we found Periodic acid-Schiff positive inclusions in hiPSC-derived chondrogenic cells with MPS VI. Genome-wide mRNA expression analysis showed that hiPSC-derived chondrogenic cells with MPS VI downregulated expression of genes involved in TGF-β/BMP signalling, and upregulated expression of inhibitors of the Wnt/β-catenin signalling pathway. Expression of genes involved in apoptosis and growth was upregulated, while expression of genes involved in glycosaminoglycan metabolism was dysregulated in hiPSC-derived chondrogenic cells with MPS VI. These results suggest that human ARSB deficiency in MPS VI causes changes in the transcriptional program underlying the early stages of chondrogenic differentiation and metabolism.

Lrig1 regulates the balance between proliferation and quiescence in glioblastoma stem cells

Patients with glioblastoma (GBM) face a dismal prognosis. GBMs are driven by glioblastoma stem cells (GSCs) that display a neural stem cell (NSC)-like phenotype. These glioblastoma stem cells are often in a quiescent state that evades current therapies, namely debulking surgery and chemo/radiotherapy. Leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins have been implicated as regulators of growth factor signalling across many tissue stem cells. Lrig1 is highly expressed in gliomas and importantly, polymorphisms have been identified that are risk alleles for patients with GBM, which suggests some functional role in gliomagenesis. We previously reported that Lrig1 is a gatekeeper of quiescence exit in adult mouse neural stem cells, suppressing epidermal growth factor receptor signalling prior to cell cycle re-entry. Here, we perform gain- and loss-of-function studies to understand the function of Lrig1 in glioblastoma stem cells. Using a novel mouse glioblastoma stem cell model, we show that genetic ablation of Lrig1 in cultured GBM stem cells results in higher proliferation and loss of quiescence. In vivo, mice transplanted with glioblastoma stem cells lacking Lrig1 display lower survival compared to Lrig1 WT glioblastoma stem cells, with tumours displaying increased proportions of proliferative cells and reduced quiescent subpopulations. In contrast, Lrig1 overexpression in mouse glioblastoma stem cells results in enhanced quiescence and reduced proliferation, with impaired tumour formation upon orthotopic transplantation. Mechanistically, we find that Lrig1-null cells have a deficiency in BMP signalling responses that may underlie their lack of responsiveness to quiescence cues in vivo. These findings highlight important roles for Lrig1 in controlling responsiveness to both epidermal growth factor receptor and BMPR signalling, and hence the proportions of quiescent and proliferative subpopulations in GBMs.

Bone Morphogenetic Protein 7 Effect on Human Glioblastoma Cell Transmigration and Migration

Glioblastoma, World Health Organization—grade IV, is the most malignant glioma type and it is still an incurable tumor due to the high level of heterogeneity and uncontrolled metastatic nature. In addition to the tumorigenicity-suppressing activity, bone morphogenetic protein 7 (BMP7) has recently been found for its invasion-promoting role in glioblastoma. However, the detailed and precise mechanism in this issue should have more elucidation. Thus, in this study, we determined the BMP7 effect on glioblastoma transmigration and migration regulations and the underlying mechanisms. Human LN18/LN229 glioblastoma cells were used in this study. Our results showed a higher BMP7/pSmad5 level in human malignant glioma tissues compared to healthy brain tissues. In addition, it was demonstrated that endogenous and exogenous BMP7 stimulation could increase the transmigration and migration capabilities of human LN18/LN229 glioblastoma cells. Moreover, this event is regulated by Smad5 and p75 neurotrophin receptor (p75NTR) signaling. Furthermore, unexpected data are that the Smad1 gene knockdown could lead to the cell death of human LN18 glioblastoma cells. Overall, the present study finds that the invasion-promoting activity of BMP7 might be an autocrine stimulation of glioblastoma and this effect could be regulated by Smad5-p75NTR signaling.

The Role of Neurodevelopmental Pathways in Brain Tumors

Disruptions to developmental cell signaling pathways and transcriptional cascades have been implicated in tumor initiation, maintenance and progression. Resurgence of aberrant neurodevelopmental programs in the context of brain tumors highlights the numerous parallels that exist between developmental and oncologic mechanisms. A deeper understanding of how dysregulated developmental factors contribute to brain tumor oncogenesis and disease progression will help to identify potential therapeutic targets for these malignancies. In this review, we summarize the current literature concerning developmental signaling cascades and neurodevelopmentally-regulated transcriptional programs. We also examine their respective contributions towards tumor initiation, maintenance, and progression in both pediatric and adult brain tumors and highlight relevant differentiation therapies and putative candidates for prospective treatments.

Nanos3, a cancer-germline gene, promotes cell proliferation, migration, chemoresistance, and invasion of human glioblastoma

Background

Radiotherapy, chemotherapy, and surgery have made crucial strides in glioblastoma treatment, yet they often fail; thus, new treatment and new detection methods are needed. Aberrant expression of Nanos3 has been functionally associated with various cancers. Here, we sought to identify the clinical significance and potential mechanisms of Nanos3 in human glioblastoma.

Methods

Nanos3 expression was studied in nude mouse glioblastoma tissues and glioblastoma cell lines by immunohistochemistry, Western blot, and RT-PCR. Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing assay was performed to generate the Nanos3 knockdown glioblastoma cell lines. The effects of Nanos3 on glioblastoma cells proliferation, migration, invasion, chemoresistance, germ cell characteristics, and tumor formation were analyzed by CCK8, transwell, cell survival experiments and alkaline phosphatase staining in vitro and in nude mouse models in vivo. Correlation between the expression of stemness proteins and the expression of Nanos3 was evaluated by Western blot.

Results

We found that Nanos3 was strongly expressed in both glioblastoma cell lines and tissues. Western blot and sequencing assays showed that the Nanos3 knockdown glioblastoma cell lines were established successfully, and we discovered that Nanos3 deletion reduced the proliferation, migration, and invasion of glioblastoma cells in vitro (P < 0.05). Nanos3 knockdown enhanced the sensitivity of glioblastoma cells to doxorubicin (DOX) and temozolomide (TMZ) (P < 0.05), and Nanos3^+/- glioblastoma cell lines did not show the characteristics of the germline cells. In addition, Nanos3 deletion inhibited subcutaneous xenograft tumor growth in vivo (P < 0.001). Moreover, the oncogenesis germline protein levels of CD133, Oct4, Ki67, and Dazl decreased significantly in glioblastoma cells following Nanos3 knockdown.

Conclusions

Both in vitro and in vivo assays suggest that Nanos3, which is a cancer-germline gene, initiates the tumorigenesis of glioblastoma via acquiring the oncogenesis germline traits. These data demonstrate that ectopic germline traits are necessary for glioblastoma growth.

Multi-Omics Analysis Reveals the Pan-Cancer Landscape of Bone Morphogenetic Proteins

Background

Bone morphogenetic proteins (BMPs) are widely involved in cancer development. However, a wealth of conflicting data raises the question of whether BMPs serve as oncogenes or as cancer suppressors.

Material/Methods

By integrating multi-omics data across cancers, we comprehensively analyzed the genomic and pharmacogenomic landscape of BMP genes across cancers.

Results

Surprisingly, our data indicate that BMPs are globally downregulated in cancers. Further genetics and epigenetics analyses show that this abnormal expression is driven by copy number variations, especially heterozygous amplification. We next assessed the BMP-associated pathways and demonstrated that they suppress cell cycle and estrogen hormone pathways. Bone morphogenetic protein interacts with 58 compounds, and their dysfunction can induce drug sensitivity.

Conclusions

Our results define the landscape of the BMP family at a systems level and open potential therapeutic opportunities for cancer patients.

Biological effects of BMP7 on small-cell lung cancer cells and its bone metastasis

Small-cell lung cancer (SCLC) is typically fatal if untreated. It is characterized by early and widespread metastases, and has the ability to rapidly develop resistance to chemotherapy. Bone morphogenetic protein 7 (BMP7), a member of the BMP family of signaling molecules, has been implicated in various types of cancer, particularly prostate cancer and breast cancer. However, there is little knowledge of the function of BMP7 in SCLC. The aim of the present study was to investigate the biological function of recombinant human (rh)BMP7 on SCLC cells and the underlying molecular basis for this regulatory mechanism. The effect of rhBMP7 on SCLC cell lines and associated signaling pathways was investigated. Results suggested that rhBMP7 significantly inhibited the proliferation, motility and invasion of SBC-3 and SBC-5 cells. However, rhBMP7 exhibited no effect on the apoptosis of SBC-5 cells, but promoted apoptosis of SBC-3 cells. Furthermore, cell cycle analysis revealed that rhBMP7 was able to increase the proportion of cells in G1 phase and decrease the S phase proportion. Total and membrane BMP receptor (BMPR)IA and BMPRIB were highly expressed in SBC-5 cells, whereas cytoplasmic BMPRIA and BMPRIB expression was higher in SBC-3 cells. However, activin A receptor type I expression was higher in SBC-3 cells in total and cytoplasmic proteins. Furthermore, following stimulation with rhBMP7, Smad2, Smad4 and p21 were downregulated. We hypothesized that rhBMP7 inhibited the progressiveness of SCLC cells by inducing G1 phase arrest and inhibiting S phase entry. The results of the present study indicated that BMP7 serves a key function in regulating the progression of SCLC.

Cross-species transcriptional analysis reveals conserved and host-specific neoplastic processes in mammalian glioma

Glioma is a unique neoplastic disease that develops exclusively in the central nervous system (CNS) and rarely metastasizes to other tissues. This feature strongly implicates the tumor-host CNS microenvironment in gliomagenesis and tumor progression. We investigated the differences and similarities in glioma biology as conveyed by transcriptomic patterns across four mammalian hosts: rats, mice, dogs, and humans. Given the inherent intra-tumoral molecular heterogeneity of human glioma, we focused this study on tumors with upregulation of the platelet-derived growth factor signaling axis, a common and early alteration in human gliomagenesis. The results reveal core neoplastic alterations in mammalian glioma, as well as unique contributions of the tumor host to neoplastic processes. Notable differences were observed in gene expression patterns as well as related biological pathways and cell populations known to mediate key elements of glioma biology, including angiogenesis, immune evasion, and brain invasion. These data provide new insights regarding mammalian models of human glioma, and how these insights and models relate to our current understanding of the human disease.

Controlled release microspheres loaded with BMP7 suppress primary tumors from human glioblastoma

Glioblastoma tumor initiating cells are believed to be the main drivers behind tumor recurrence, and therefore therapies that specifically manage this population are of great medical interest. In a previous work, we synthesized controlled release microspheres optimized for intracranial delivery of BMP7, and showed that these devices are able to stop the in vitro growth of a glioma cell line. Towards the translational development of this technology, we now explore these microspheres in further detail and characterize the mechanism of action and the in vivo therapeutic potential using tumor models relevant for the clinical setting: human primary glioblastoma cell lines. Our results show that BMP7 can stop the proliferation and block the self-renewal capacity of those primary cell lines that express the receptor BMPR1B. BMP7 was encapsulated in poly (lactic-co-glycolic acid) microspheres in the form of a complex with heparin and Tetronic, and the formulation provided effective release for several weeks, a process controlled by carrier degradation. Data from xenografts confirmed reduced and delayed tumor formation for animals treated with BMP7-loaded microspheres. This effect was coincident with the activation of the canonical BMP signaling pathway. Importantly, tumors treated with BMP7-loaded microspheres also showed downregulation of several markers that may be related to a malignant stem cell-like phenotype: CD133(+), Olig2, and GFAPδ. We also observed that tumors treated with BMP7-loaded microspheres showed enhanced expression of cell cycle inhibitors and reduced expression of the proliferation marker PCNA. In summary, BMP7-loaded controlled release microspheres are able to inhibit GBM growth and reduce malignancy markers. We envisage that this kind of selective therapy for tumor initiating cells could have a synergistic effect in combination with conventional cytoreductive therapy (chemo-, radiotherapy) or with immunotherapy.

Bone morphogenetic protein 7 sensitizes O6-methylguanine methyltransferase expressing-glioblastoma stem cells to clinically relevant dose of temozolomide

Background

Temozolomide (TMZ) is an oral DNA-alkylating agent used for treating patients with glioblastoma. However, therapeutic benefits of TMZ can be compromised by the expression of O6-methylguanine methyltransferase (MGMT) in tumor tissue. Here we used MGMT-expressing glioblastoma stem cells (GSC) lines as a model for investigating the molecular mechanism underlying TMZ resistance, while aiming to explore a new treatment strategy designed to possibly overcome resistance to the clinically relevant dose of TMZ (35 μM).

Methods

MGMT-expressing GSC cultures are resistant to TMZ, and IC50 (half maximal inhibitory concentration) is estimated at around 500 μM. Clonogenic GSC surviving 500 μM TMZ (GSC-500 μM TMZ), were isolated. Molecular signatures were identified via comparative analysis of expression microarray against parental GSC (GSC-parental). The recombinant protein of top downregulated signature was used as a single agent or in combination with TMZ, for evaluating therapeutic effects of treatment of GSC.

Results

The molecular signatures characterized an activation of protective stress responses in GSC-500 μM TMZ, mainly including biotransformation/detoxification of xenobiotics, blocked endoplasmic reticulum stress-mediated apoptosis, epithelial-to-mesenchymal transition (EMT), and inhibited growth/differentiation. Bone morphogenetic protein 7 (BMP7) was identified as the top down-regulated gene in GSC-500 μM TMZ. Although augmenting BMP7 signaling in GSC by exogenous BMP7 treatment did not effectively stop GSC growth, it markedly sensitized both GSC-500 μM TMZ and GSC-parental to 35 μM TMZ treatment, leading to loss of self-renewal and migration capacity. BMP7 treatment induced senescence of GSC cultures and suppressed mRNA expression of CD133, MGMT, and ATP-binding cassette drug efflux transporters (ABCB1, ABCG2), as well as reconfigured transcriptional profiles in GSC by downregulating genes associated with EMT/migration/invasion, stemness, inflammation/immune response, and cell proliferation/tumorigenesis. BMP7 treatment significantly prolonged survival time of animals intracranially inoculated with GSC when compared to those untreated or treated with TMZ alone (p = 0.0017), whereas combination of two agents further extended animal survival compared to BMP7 alone (p = 0.0489).

Conclusions

These data support the view that reduced endogenous BMP7 expression/signaling in GSC may contribute to maintained stemness, EMT, and chemoresistant phenotype, suggesting that BMP7 treatment may provide a novel strategy in combination with TMZ for an effective treatment of glioblastoma exhibiting unmethylated MGMT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0459-1) contains supplementary material, which is available to authorized users.

Development of targeted therapies in treatment of glioblastoma

Glioblastoma (GBM) is a type of tumor that is highly lethal despite maximal therapy. Standard therapeutic approaches provide modest improvement in progression-free and overall survival, necessitating the investigation of novel therapies. Oncologic therapy has recently experienced a rapid evolution toward "targeted therapy", with drugs directed against specific targets which play essential roles in the proliferation, survival, and invasiveness of GBM cells, including numerous molecules involved in signal transduction pathways. Inhibitors of these molecules have already entered or are undergoing clinical trials. However, significant challenges in their development remain because several preclinical and clinical studies present conflicting results. In this article, we will provide an up-to-date review of the current targeted therapies in GBM.

Bone metastasis imaging with SPECT/CT/MRI: a preclinical toolbox for therapy studies

Bone is one of the most common metastatic target sites in breast cancer, with more than 200 thousand new cases of invasive cancer diagnosed in the US alone in 2011. We set out to establish a multimodality imaging platform for bone metastases in small animals as a tool to non-invasively quantify metastasis growth, imaging the ensuing bone lesions and possibly the response to treatment. To this end, a mouse model of osteolytic metastatic bone tumors was characterized with SPECT/CT and MRI over time. A cell line capable of forming bone metastases, MDA-MB-231, was genetically modified to stably express the reporter gene herpes simplex virus-1 thymidine kinase (hsv-1 tk). The intracellular accumulation of the radiolabeled tracer [(123)I]FIAU promoted by HSV-1 TK specifically pinpoints the location of tumor cells which can be imaged in vivo by SPECT. First, a study using tumors implanted subcutaneously was performed. The SPECT/MRI overlays and the ex vivo γ-counting showed a linear correlation in terms of %ID/cm(3) (R(2)=0.93) and %ID/g (R(2)=0.77), respectively. Then, bone metastasis growth was imaged weekly by SPECT/CT and T2-weighted MRI over a maximum of 40 days post-intracardiac injection of tumor cells. The first activity spots detectable with SPECT, around day 20 post-cell injection, were smaller than 2mm(3) and not yet visible by MRI and increased in volume and in %ID over the weeks. Osteolytic bone lesions were visible by CT (in vivo) and μCT (ex vivo). The SPECT/MRI overlays also showed a linear correlation in terms of %ID/cm(3) (R(2)=0.86). In conclusion, a new multimodality imaging platform has been established that non-invasively combines images of active tumor areas (SPECT), tumor volume (MRI) and the corresponding bone lesions (CT and μCT). To our knowledge this is the first report where the combination of soft tissue information from MRI, bone lesions by CT, and reporter gene imaging by SPECT is used to non-invasively follow metastatic bone lesions.

Genomic Analysis of the BMP Family in Glioblastomas

Glioblastoma multiforme (GBM) is a grade IV glioma with a median survival of 15 months. Recently, bone morphogenetic protein (BMP) signaling has been shown to promote survival in xenograft murine models. To gain a better understanding of the role of BMP signaling in human GBMs, we examined the genomic alterations of 90 genes associated with BMP signaling in GBM patient samples. We completed this analysis using publically available datasets compiled through The Cancer Genome Atlas and the Glioma Molecular Diagnostic Initiative. Here we show how mRNA expression is altered in GBM samples and how that is associated with patient survival, highlighting both known and novel associations between BMP signaling and GBM biology.

Cancer subclonal genetic architecture as a key to personalized medicine

The future of personalized oncological therapy will likely rely on evidence-based medicine to integrate all of the available evidence to delineate the most efficacious treatment option for the patient. To undertake evidence-based medicine through use of targeted therapy regimens, identification of the specific underlying causative mutation(s) driving growth and progression of a patient's tumor is imperative. Although molecular subtyping is important for planning and treatment, intraclonal genetic diversity has been recently highlighted as having significant implications for biopsy-based prognosis. Overall, delineation of the clonal architecture of a patient's cancer and how this will impact on the selection of the most efficacious therapy remain a topic of intense interest.

BMPs as therapeutic targets and biomarkers in astrocytic glioma

Astrocytic glioma is the most common brain tumor. The glioma initiating cell (GIC) fraction of the tumor is considered as highly chemoresistant, suggesting that GICs are responsible for glioma relapse. A potential treatment for glioma is to induce differentiation of GICs to a more benign and/or druggable cell type. Given BMPs are among the most potent inducers of GIC differentiation, they have been considered as noncytotoxic therapeutic compounds that may be of use to prevent growth and recurrence of glioma. We herein summarize advances made in the understanding of the role of BMP signaling in astrocytic glioma, with a particular emphasis on the effects exerted on GICs. We discuss the prognostic value of BMP signaling components and the implications of BMPs in the differentiation of GICs and in their sensitization to alkylating drugs and oncolytic therapy/chemotherapy. This mechanistic insight may provide new opportunities for therapeutic intervention of brain cancer.

Gene expression profiling associated with angiotensin II type 2 receptor-induced apoptosis in human prostate cancer cells

Increased expression of angiotensin II type 2 receptor (AT2R) induces apoptosis in numerous tumor cell lines, with either Angiotensin II-dependent or Angiotensin II-independent regulation, but its molecular mechanism remains poorly understood. Here, we used PCR Array analysis to determine the gene and microRNA expression profiles in human prostate cancer cell lines transduced with AT2R recombinant adenovirus. Our results demonstrated that AT2R over expression leads to up-regulation of 6 apoptosis-related genes (TRAIL-R2, BAG3, BNIPI, HRK, Gadd45a, TP53BP2), 2 cytokine genes (IL6 and IL8) and 1 microRNA, and down-regulation of 1 apoptosis-related gene TNFSF10 and 2 cytokine genes (BMP6, BMP7) in transduced DU145 cells. HRK was identified as an up-regulated gene in AT2R-transduced PC-3 cells by real-time RT-PCR. Next, we utilized siRNAs to silence the up-regulated genes to further determine their roles on AT2R overexpression mediated apoptosis. The results showed downregulation of Gadd45a reduced the apoptotic effect by ∼30% in DU145 cells, downregulation of HRK reduced AT2R-mediated apoptosis by more than 50% in PC-3 cells, while downregulation of TRAIL-R2 enhanced AT2R-mediated apoptosis more than 4 times in DU145 cells. We also found that the effects on AT2R-mediated apoptosis caused by downregulation of Gadd45a, TRAIL-R2 and HRK were independent in activation of p38 MAPK, p44/42 MAPK and p53. Taken together, our results demonstrated that TRAIL-R2, Gadd45a and HRK may be novel target genes for further study of the mechanism of AT2R-mediated apoptosis in prostate cancer cells.

miR-656 inhibits glioma tumorigenesis through repression of BMPR1A

Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-β family, plays critical roles in cell differentiation, modeling and regeneration processes in several tissues. BMP-2 is also closely associated with various malignant tumors. microRNAs negatively and posttranscriptionally regulate gene expression and function as oncogenes or tumor suppressors. Herein, we report that miR-656 expression was significantly downregulated in glioma cell lines and tissues. We identified and confirmed that BMP receptor, type 1A (BMPR1A) is a direct target of miR-656. The expression of BMPR1A was negatively correlated with that of miR-656 in human glioma tissues. We further demonstrated that miR-656 suppressed glioma cell proliferation, neurosphere formation, migration and invasion with or without exogenous BMP-2. Engineered knockdown of BMPR1A diminished the antiproliferation effect of miR-656 in vitro. Moreover, the canonical BMP/Smad and non-canonical BMP/mitogen-activated protein kinase (MAPK) pathways were inhibited by miR-656 overexpression. Several cancer-related signaling molecules, including cyclin B, cyclin D1, matrix metalloproteinase-9, p21 and p27, were also involved in miR-656 function in glioma cells. The tumor-suppressing function of miR-656 was validated using an in vivo intracranial xenograft mouse model. Notably, ectopic expression of miR-656 markedly reduced tumor size and prolonged the survival of mice treated with or without BMP-2. These results elucidate the function of miR-656 in glioma progression and suggest a promising application for glioma treatment.

BMP signaling induces astrocytic differentiation of clinically derived oligodendroglioma propagating cells

Oligodendrogliomas are a type of glioma that lack detailed investigation because of an inability to cultivate oligodendroglioma cells that faithfully recapitulate their salient qualities. We have successfully isolated and propagated glioma stem-like cells from multiple clinical oligodendroglioma specimens. These oligodendroglioma-propagating cells (OligPC) are multipotent and form xenografts with oligodendroglioma features. Bone morphogenetic proteins (BMP) are considered potent inhibitors of oligodendrogliogenesis during development; therefore, the effects of BMP signaling in OligPCs were characterized. BMP pathway components are expressed by OligPCs and canonical signaling via Smad proteins is intact. This signaling potently depletes CD133-positive OligPCs, decreasing proliferation, and inducing astrocytic differentiation. Furthermore, analyses revealed that cytoplasmic sequestration of the oligodendrocyte differentiation factors OLIG1/2 by the BMP signaling effectors ID2 and ID4 is a plausible underlying mechanism. These findings elucidate the molecular pathways that underlie the effects of BMP signaling on oligodendroglioma stem-like cells.

IMPLICATIONS

Stem-like cells are capable of propagating oligodendrogliomas, and BMP signaling potently diminishes their stemness by inducing astrocytic differentiation, suggesting that BMP activation may be effective as a cancer stem cell-targeted therapy.

Overcoming intratumor heterogeneity of polygenic cancer drug resistance with improved biomarker integration

Improvements in technology and resources are helping to advance our understanding of cancer-initiating events as well as factors involved with tumor progression, adaptation, and evasion of therapy. Tumors are well known to contain diverse cell populations and intratumor heterogeneity affords neoplasms with a diverse set of biologic characteristics that can be used to evolve and adapt. Intratumor heterogeneity has emerged as a major hindrance to improving cancer patient care. Polygenic cancer drug resistance necessitates reconsidering drug designs to include polypharmacology in pursuit of novel combinatorial agents having multitarget activity to overcome the diverse and compensatory signaling pathways in which cancer cells use to survive and evade therapy. Advances will require integration of different biomarkers such as genomics and imaging to provide for more adequate elucidation of the spatially varying location, type, and extent of diverse intratumor signaling molecules to provide for a rationale-based personalized cancer medicine strategy.

The interconnectedness of cancer cell signaling

The elegance of fundamental and applied research activities have begun to reveal a myriad of spatial and temporal alterations in downstream signaling networks affected by cell surface receptor stimulation including G protein-coupled receptors and receptor tyrosine kinases. Interconnected biochemical pathways serve to integrate and distribute the signaling information throughout the cell by orchestration of complex biochemical circuits consisting of protein interactions and covalent modification processes. It is clear that scientific literature summarizing results from both fundamental and applied scientific research activities has served to provide a broad foundational biologic database that has been instrumental in advancing our continued understanding of underlying cancer biology. This article reflects on historical advances and the role of innovation in the competitive world of grant-sponsored research.

Bone morphogenetic protein modulator BMPER is highly expressed in malignant tumors and controls invasive cell behavior

Bone morphogenetic proteins (BMPs) are growth factors that exert important functions in cell proliferation, migration and differentiation. Till date, multiple human tumors have been reported to display a dysregulation of several members of the BMP pathway that is associated with enhanced malignant tumor growth and metastasis. BMPER (BMP endothelial cell precursor-derived regulator) is a direct BMP modulator that is necessary for BMPs to exert their full-range signaling activity. Moreover, BMPER is expressed by endothelial cells and their progenitors, and has pro-angiogenic features in these cells. Here, we describe the expression of BMPER in human specimens of lung, colon and cervix carcinomas and cell lines derived from such carcinomas. In contrast to healthy tissues, BMPER is highly expressed upon malignant deterioration. Functionally, loss of BMPER in the lung tumor cell line A549 impairs proliferation, migration, invasion as well as tumor cell-induced endothelial cell sprout formation. In contrast, stimulation of A549 cells with exogenous BMPER had no further effect. We found that the BMPER effect may be transduced by regulation of the BMP target transcription factor inhibitor of DNA binding 1 (Id1) and matrix metalloproteinases (MMPs) 9 and 2. These facilitators of cell migration are downregulated when BMPER is absent. To prove the relevance of our in vitro results in vivo, we generated Lewis lung carcinoma cells with impaired BMPER expression and implanted them into the lungs of C57BL/6 mice. In this model, the absence of BMPER resulted in severely reduced tumor growth and tumor angiogenesis. Taken together, these data unequivocally demonstrate that the BMP modulator BMPER is highly expressed in malignant tumors and tumor growth is dependent on the presence of BMPER.

The BMP2/7 heterodimer inhibits the human breast cancer stem cell subpopulation and bone metastases formation

Accumulating evidence suggests that a subpopulation of breast cancer cells, referred to as cancer stem cells (CSCs), have the ability to propagate a tumor and potentially seed new metastases. Furthermore, stimulation of an epithelial-to-mesenchymal transition by factors like transforming growth factor-β (TGFβ) is accompanied with the generation of breast CSCs. Previous observations indicated that bone morphogenetic protein-7 (BMP7) antagonizes the protumorigenic and prometastatic actions of TGFβ, but whether BMP7 action is mechanistically linked to breast CSCs has remained elusive. Here, we have studied the effects of BMP7, BMP2 and a BMP2/7 heterodimer on the formation of human breast CSCs (ALDH(hi)/CD44(hi)/CD24(-/low)) and bone metastases formation in a preclinical model of intra-cardiac injection of MDA-MB-231 cells in athymic nude (Balb/c nu/nu) mice. The BMP2/7 heterodimer was the most efficient stimulator of BMP signaling and very effectively reduced TGFβ-driven Smad signaling and cancer cell invasiveness. The tested BMPs-particularly the heterodimeric BMP2/7-strongly reduced the size of the ALDH(hi)/CD44(hi)/CD24(-/low) CSC subpopulation. In keeping with these in vitro observations, pretreatment of cancer cells with BMPs for 72 h prior to systemic inoculation of the cancer cells inhibited the formation of bone metastases. Collectively, our data support the notion that breast CSCs are involved in bone metastasis formation and describe heterodimeric BMP2/7 as a powerful TGFβ antagonist with anti-metastatic potency.