A synthetic BMP-2 mimicking peptide induces glioblastoma stem cell differentiation

Strategies for the Covalent Anchoring of a BMP-2-Mimetic Peptide to PEEK Surface for Bone Tissue Engineering

Researchers in the field of tissue engineering are always searching for new scaffolds for bone repair. Polyetheretherketone (PEEK) is a chemically inert polymer that is insoluble in conventional solvents. PEEK's great potential in tissue engineering applications arises from its ability to not induce adverse reactions when in contact with biological tissues and its mechanical properties, which are similar to those of human bone. These exceptional features are limited by the bio-inertness of PEEK, which causes poor osteogenesis on the implant surface. Here, we demonstrated that the covalent grafting of the sequence (48-69) mapped on the BMP-2 growth factor (GBMP1α) significantly enhances the mineralization and gene expression of human osteoblasts. Different chemical methods were employed for covalently grafting the peptide onto 3D-printed PEEK disks: (a) the reaction between PEEK carbonyls and amino-oxy groups inserted in the peptides' N-terminal sites (oxime chemistry) and (b) the photoactivation of azido groups present in the peptides' N-terminal sites, which produces nitrene radicals able to react with PEEK surface. The peptide-induced PEEK surface modification was assessed using X-ray photoelectron measurements, while the superficial properties of the functionalized material were analyzed by means of atomic force microscopy and force spectroscopy. Live and dead assays and SEM measurements showed greater cell cover on functionalized samples than the control, without any cytotoxicity induction. Moreover, functionalization improved the rate of cell proliferation and the amount of calcium deposits, as demonstrated by the AlamarBlue™ and alizarin red results, respectively. The effects of GBMP1α on h-osteoblast gene expression were assayed using quantitative real-time polymerase chain reaction.

Strategies of immobilizing BMP-2 with 3D-printed scaffolds to improve osteogenesis

The management and definitive treatment of critical-size bone defects in severe trauma, tumor resection and congenital malformation are troublesome for orthopedic surgeons and patients worldwide without recognized good treatment strategies. Researchers and clinicians are working to develop new strategies to treat these problems. This review aims to summarize the techniques used by additive manufacturing scaffolds loaded with BMP-2 to promote osteogenesis and to analyze the current status and trends in relevant clinical translation. Optimize composite scaffold design to enhance bone regeneration through printing technology, material selection, structure design and loading methods of BMP-2 to advance the clinical therapeutic bone repair field.

Polysialic Acid Sustains the Hypoxia-Induced Migration and Undifferentiated State of Human Glioblastoma Cells

Gliomas are the most common primary malignant brain tumors. Glioblastoma, IDH-wildtype (GBM, CNS WHO grade 4) is the most aggressive form of glioma and is characterized by extensive hypoxic areas that strongly correlate with tumor malignancy. Hypoxia promotes several processes, including stemness, migration, invasion, angiogenesis, and radio- and chemoresistance, that have direct impacts on treatment failure. Thus, there is still an increasing need to identify novel targets to limit GBM relapse. Polysialic acid (PSA) is a carbohydrate composed of a linear polymer of α2,8-linked sialic acids, primarily attached to the Neural Cell Adhesion Molecule (NCAM). It is considered an oncodevelopmental antigen that is re-expressed in various tumors. High levels of PSA-NCAM are associated with high-grade and poorly differentiated tumors. Here, we investigated the effect of PSA inhibition in GBM cells under low oxygen concentrations. Our main results highlight the way in which hypoxia stimulates polysialylation in U87-MG cells and in a GBM primary culture. By lowering PSA levels with the sialic acid analog, F-NANA, we also inhibited GBM cell migration and interfered with their differentiation influenced by the hypoxic microenvironment. Our findings suggest that PSA may represent a possible molecular target for the development of alternative pharmacological strategies to manage a devastating tumor like GBM.

Current Opportunities for Targeting Dysregulated Neurodevelopmental Signaling Pathways in Glioblastoma

Glioblastoma (GBM) is the most common and highly lethal type of brain tumor, with poor survival despite advances in understanding its complexity. After current standard therapeutic treatment, including tumor resection, radiotherapy and concomitant chemotherapy with temozolomide, the median overall survival of patients with this type of tumor is less than 15 months. Thus, there is an urgent need for new insights into GBM molecular characteristics and progress in targeted therapy in order to improve clinical outcomes. The literature data revealed that a number of different signaling pathways are dysregulated in GBM. In this review, we intended to summarize and discuss current literature data and therapeutic modalities focused on targeting dysregulated signaling pathways in GBM. A better understanding of opportunities for targeting signaling pathways that influences malignant behavior of GBM cells might open the way for the development of novel GBM-targeted therapies.

Mn-Containing Bioactive Glass-Ceramics: BMP-2-Mimetic Peptide Covalent Grafting Boosts Human-Osteoblast Proliferation and Mineral Deposition

The addition of Mn in bioceramic formulation is gaining interest in the field of bone implants. Mn activates human osteoblast (h-osteoblast) integrins, enhancing cell proliferation with a dose-dependent effect, whereas Mn-enriched glasses induce inhibition of Gram-negative or Gram-positive bacteria and fungi. In an effort to further optimize Mn-containing scaffolds' beneficial interaction with h-osteoblasts, a selective and specific covalent functionalization with a bioactive peptide was carried out. The anchoring of a peptide, mapped on the BMP-2 wrist epitope, to the scaffold was performed by a reaction between an aldehyde group of the peptide and the aminic groups of silanized Mn-containing bioceramic. SEM-EDX, FT-IR, and Raman studies confirmed the presence of the peptide grafted onto the scaffold. In in vitro assays, a significant improvement in h-osteoblast proliferation, gene expression, and calcium salt deposition after 7 days was detected in the functionalized Mn-containing bioceramic compared to the controls.

Tracing the origins of glioblastoma by investigating the role of gliogenic and related neurogenic genes/signaling pathways in GBM development: a systematic review

Background

Glioblastoma is one of the most aggressive tumors. The etiology and the factors determining its onset are not yet entirely known. This study investigates the origins of GBM, and for this purpose, it focuses primarily on developmental gliogenic processes. It also focuses on the impact of the related neurogenic developmental processes in glioblastoma oncogenesis. It also addresses why glial cells are at more risk of tumor development compared to neurons.

Methods

Databases including PubMed, MEDLINE, and Google Scholar were searched for published articles without any date restrictions, involving glioblastoma, gliogenesis, neurogenesis, stemness, neural stem cells, gliogenic signaling and pathways, neurogenic signaling and pathways, and astrocytogenic genes.

Results

The origin of GBM is dependent on dysregulation in multiple genes and pathways that accumulatively converge the cells towards oncogenesis. There are multiple layers of steps in glioblastoma oncogenesis including the failure of cell fate-specific genes to keep the cells differentiated in their specific cell types such as p300, BMP, HOPX, and NRSF/REST. There are genes and signaling pathways that are involved in differentiation and also contribute to GBM such as FGFR3, JAK-STAT, and hey1. The genes that contribute to differentiation processes but also contribute to stemness in GBM include notch, Sox9, Sox4, c-myc gene overrides p300, and then GFAP, leading to upregulation of nestin, SHH, NF-κB, and others. GBM mutations pathologically impact the cell circuitry such as the interaction between Sox2 and JAK-STAT pathway, resulting in GBM development and progression.

Conclusion

Glioblastoma originates when the gene expression of key gliogenic genes and signaling pathways become dysregulated. This study identifies key gliogenic genes having the ability to control oncogenesis in glioblastoma cells, including p300, BMP, PAX6, HOPX, NRSF/REST, LIF, and TGF beta. It also identifies key neurogenic genes having the ability to control oncogenesis including PAX6, neurogenins including Ngn1, NeuroD1, NeuroD4, Numb, NKX6-1 Ebf, Myt1, and ASCL1. This study also postulates how aging contributes to the onset of glioblastoma by dysregulating the gene expression of NF-κB, REST/NRSF, ERK, AKT, EGFR, and others.

Nanoscale Topographical Effects on the Adsorption Behavior of Bone Morphogenetic Protein-2 on Graphite

The interaction between bone morphogenetic protein-2 (BMP-2) and the surface of biomaterials is essential for the restoration of bone and cartilage tissue, inducing cellular differentiation and proliferation. The properties of the surface, including topology features, regulate the conformation and bioactivity of the protein. In this research, we investigated the influence of nanopatterned surfaces on the interaction of a homodimer BMP-2 with graphite material by combining molecular dynamics (MD) and steered molecular dynamics (SMD) simulations. The graphite substrates were patterned as flat, linear grating, square, and circular profiles in combination with BMP-2 conformation in the side-on configuration. Ramachandran plots for the wrist and knuckle epitopes indicated no steric hindrances and provided binding sites to type I and type II receptors. Results showed two optimal patterns that increased protein adsorption of the lower monomer while preserving the secondary structure and leaving the upper monomer free to interact with the cells. Charged residues arginine and lysine and polar residues histidine and tyrosine were the main residues responsible for the strong interaction with the graphite surface. This research provides new molecular-level insights to further understand the mechanisms underlying protein adsorption on nanoscale patterned substrates.

To B (Bone Morphogenic Protein-2) or Not to B (Bone Morphogenic Protein-2): Mesenchymal Stem Cells May Explain the Protein's Role in Osteosarcomagenesis

Osteosarcoma (OS), a primary malignant bone tumor, stems from bone marrow-derived mesenchymal stem cells (BMSCs) and/or committed osteoblast precursors. Distant metastases, in particular pulmonary and skeletal metastases, are common in patients with OS. Moreover, extensive resection of the primary tumor and bone metastases usually leads to bone defects in these patients. Bone morphogenic protein-2 (BMP-2) has been widely applied in bone regeneration with the rationale that BMP-2 promotes osteoblastic differentiation of BMSCs. Thus, BMP-2 might be useful after OS resection to repair bone defects. However, the potential tumorigenicity of BMP-2 remains a concern that has impeded the administration of BMP-2 in patients with OS and in populations susceptible to OS with severe bone deficiency (e.g., in patients with genetic mutation diseases and aberrant activities of bone metabolism). In fact, some studies have drawn the opposite conclusion about the effect of BMP-2 on OS progression. Given the roles of BMSCs in the origination of OS and osteogenesis, we hypothesized that the responses of BMSCs to BMP-2 in the tumor milieu may be responsible for OS development. This review focuses on the relationship among BMSCs, BMP-2, and OS cells; a better understanding of this relationship may elucidate the accurate mechanisms of actions of BMP-2 in osteosarcomagenesis and thereby pave the way for clinically safer and broader administration of BMP-2 in the future. For example, a low dosage of and a slow-release delivery strategy for BMP-2 are potential topics for exploration to treat OS.

Chitosan Covalently Functionalized with Peptides Mapped on Vitronectin and BMP-2 for Bone Tissue Engineering

Worldwide, over 20 million patients suffer from bone disorders annually. Bone scaffolds are designed to integrate into host tissue without causing adverse reactions. Recently, chitosan, an easily available natural polymer, has been considered a suitable scaffold for bone tissue growth as it is a biocompatible, biodegradable, and non-toxic material with antimicrobial activity and osteoinductive capacity. In this work, chitosan was covalently and selectively biofunctionalized with two suitably designed bioactive synthetic peptides: a Vitronectin sequence (HVP) and a BMP-2 peptide (GBMP1a). Nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) investigations highlighted the presence of the peptides grafted to chitosan (named Chit-HVP and Chit-GBMP1a). Chit-HVP and Chit-GBMP1a porous scaffolds promoted human osteoblasts adhesion, proliferation, calcium deposition, and gene expression of three crucial osteoblast proteins. In particular, Chit-HVP highly promoted adhesion and proliferation of osteoblasts, while Chit-GBMP1a guided cell differentiation towards osteoblastic phenotype.

Therapeutic Perspective of Temozolomide Resistance in Glioblastoma Treatment

Glioblastoma (GB) is the most lethal form of primary brain neoplasm. TMZ is the first-line standard treatment, but the strong resistance constrains the efficacy in clinical use. GB contains glioma stem cells (GSCs), which contribute to TMZ resistance, promote cell survival evolvement, and repopulate the tumor mass. This review summarizes the TMZ-resistance mechanisms and discusses several potential therapies from the conservative opinion of GSC-targeted therapy orientation to the current view of TMZ resistance-aimed efficacy, which will provide an understanding of the role of heterogeneity in drug resistance and improve therapeutic efficacy in general.

Peptides Derived from Growth Factors to Treat Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuron losses in memory-related brain structures. The classical features of AD are a dysregulation of the cholinergic system, the accumulation of amyloid plaques, and neurofibrillary tangles. Unfortunately, current treatments are unable to cure or even delay the progression of the disease. Therefore, new therapeutic strategies have emerged, such as the exogenous administration of neurotrophic factors (e.g., NGF and BDNF) that are deficient or dysregulated in AD. However, their low capacity to cross the blood-brain barrier and their exorbitant cost currently limit their use. To overcome these limitations, short peptides mimicking the binding receptor sites of these growth factors have been developed. Such peptides can target selective signaling pathways involved in neuron survival, differentiation, and/or maintenance. This review focuses on growth factors and their derived peptides as potential treatment for AD. It describes (1) the physiological functions of growth factors in the brain, their neuronal signaling pathways, and alteration in AD; (2) the strategies to develop peptides derived from growth factor and their capacity to mimic the role of native proteins; and (3) new advancements and potential in using these molecules as therapeutic treatments for AD, as well as their limitations.

A Systematic Review of Glioblastoma-Targeted Therapies in Phases II, III, IV Clinical Trials

Glioblastoma (GBM), the most frequent and aggressive glial tumor, is currently treated as first line by the Stupp protocol, which combines, after surgery, radiotherapy and chemotherapy. For recurrent GBM, in absence of standard treatment or available clinical trials, various protocols including cytotoxic drugs and/or bevacizumab are currently applied. Despite these heavy treatments, the mean overall survival of patients is under 18 months. Many clinical studies are underway. Based on clinicaltrials.org and conducted up to 1 April 2020, this review lists, not only main, but all targeted therapies in phases II-IV of 257 clinical trials on adults with newly diagnosed or recurrent GBMs for the last twenty years. It does not involve targeted immunotherapies and therapies targeting tumor cell metabolism, that are well documented in other reviews. Without surprise, the most frequently reported drugs are those targeting (i) EGFR (40 clinical trials), and more generally tyrosine kinase receptors (85 clinical trials) and (ii) VEGF/VEGFR (75 clinical trials of which 53 involving bevacizumab). But many other targets and drugs are of interest. They are all listed and thoroughly described, on an one-on-one basis, in four sections related to targeting (i) GBM stem cells and stem cell pathways, (ii) the growth autonomy and migration, (iii) the cell cycle and the escape to cell death, (iv) and angiogenesis.

Inhibition of Bone Morphogenetic Protein 2 Suppresses the Stemness Maintenance of Cancer Stem Cells in Hepatocellular Carcinoma via the MAPK/ERK Pathway

Background

Hepatocellular carcinoma (HCC) remains a life-threatening malignant tumor. Cancer stem cells (CSCs) harbor tumor-initiating capacity and can be used as a therapeutic target for human malignancies. Bone morphogenetic proteins (BMPs) play a regulatory role in CSCs. This study investigated the role and mechanism of BMP2 in CSCs in HCC.

Methods

BMP2 expression in HCC tissues and cells, and CSCs from HepG2 cells and SMMC7721 cells (HepG2-CSCs and SMMC7721-CSCs) was measured. The association between BMP2 expression and prognosis of HCC patients was analyzed. CSCs were interfered with BMP2 to evaluate the abilities of colony and tumor sphere formation, levels of stemness-related markers, epithelial-mesenchymal transition (EMT), and invasion and migration. Levels of MAPK/ERK pathway-related proteins in HepG2-CSCs were detected after BMP2 knockdown. The effect of the activated MAPK/ERK pathway on HepG2-CSCs was assessed. Finally, the effect of BMP2 inhibition on CSCs in HCC was verified in vivo.

Results

BMP2 showed obvious upregulation in HCC tissues and cells and was further upregulated in CSCs in HCC, with its higher expression indicative of worse prognosis. Silencing BMP2 inhibited colony and tumor sphere formation, levels of stemness-related markers, as well as EMT, invasion and migration of HepG2-CSCs and SMMC7721-CSCs. The MAPK/ERK pathway was suppressed after BMP2 knockdown, and its activation reversed the inhibitory effect of shBMP2 on hepatic CSCs. BMP2 accelerated tumor growth and EMT of CSCs in HCC in vivo.

Conclusion

We concluded that BMP2 knockdown inhibited the EMT, proliferation and invasion of CSCs in HCC, thereby hindering the stemness maintenance via suppressing the MAPK/ERK pathway.

Identification of miRNA signature associated with BMP2 and chemosensitivity of TMZ in glioblastoma stem-like cells

Glioblastoma multiform (GBM) is the most lethal intracranial tumor in adults. Glioblastoma stem-like cells (GSCs) are responsible for tumorigenesis and chemotherapy resistance. BMPs are known to increase temozolomide (TMZ) response in GSCs, however, the intracellular molecular mechanism remains largely unknown. In this study, we built a GSC cell model called U87S, and performed RNA sequencing to identify differentially expressed (DE) miRNA profiles in U87S cells treated with BMP2, TMZ or combined BMP2 and TMZ respectively. Bioinformatics analysis revealed that most DE miRNAs were involved in the cancer pathways, suggesting their crucial roles in gliomagenesis. Eight miRNAs from RNA-seq were validated. Four out of these miRNAs (has-miR-199a-3p, hsa-miR-374b-5p, hsa-miR-320d, and hsa-miR-339-5p) were found significantly up-regulated in GBM tumor tissues. One of them, hsa-miR-199a-3p, was significantly correlated with the survival of GBM patients, and differentially expressed in U87S cells. Expression of hsa-miR-199a-3p was up-regulated by BMP. Overexpression of hsa-miR-199a-3p in U87S cells inhibited cell viability and enhanced the cytotoxicity of TMZ. And activation of BMP boosted the effect of hsa-miR-199a-3p on cell viability and TMZ-mediated cytotoxicity. Besides, expressions of five predicted targets of hsa-miR-199a-3p were evaluated. Four of them were differentially expressed in GBM tumors. And one of them, SLC22A18, was associated with the survival of GBM patients. In the end, a hsa-miR-199a-3p-mediated ceRNA network was constructed for the convenience of future study. Together, our data provided DE miRNA expression profiles associated with BMP2 and TMZ in GSCs, which might lead to finding out miRNA-based target therapies that specially target GSCs.

HIF-1α/Wnt signaling-dependent control of gene transcription regulates neuronal differentiation of glioblastoma stem cells

HIF-1α has been suggested to interplay with Wnt signaling components in order to activate a neuronal differentiation process in both normal brain and glioblastoma (GBM). Based on these data, we explored the molecular mechanisms underlying the observed capability of GBM cells to acquire a neuronal phenotype upon Wnt signaling stimulation and how the microenvironment, particularly hypoxia, modulates this process.

Methods: here, the employment of ChIP-seq techniques together with co-immunoprecipitation approaches allowed to reconstruct the molecular interactions responsible for activating specific pro-differentiating transcriptional programs in GBM cells. Moreover, gene silencing/over-expression approaches coupled with the functional analysis of cell phenotype were applied to confirm ChIP-driven hypotheses. Finally, we combined the use of publicly available gene expression datasets with protein expression data by immunohistochemistry to test the clinical relevance of obtained results.

Results: our data clearly suggest that HIF-1α is recruited by the β-catenin/TCF1 complex to foster neuronal differentiation gene transcription in hypoxic GBM cells. Conversely, at higher oxygen levels, the increased expression of TCF4 exerts a transcriptional inhibitory function on the same genomic regions, thus counteracting differentiation. Moreover, we demonstrate the existence of a positive correlation between the expression levels of HIF-1α, TCF1 and neuronal phenotype in GBM tumors, accompanied by the over-expression of several Wnt signaling components, finally affecting patient prognosis.

Conclusion: we unveiled a peculiar mechanism by which TCF1 and HIF-1α can induce a reminiscent neuronal differentiation of hypoxic GBM cells, which is hampered, in normoxia, by high levels of TCF4, thus not only de facto controlling the balance between differentiation and stemness, but also impacting on intra-tumoral heterogeneity and eventually patient outcome.

BMP9 counteracts the tumorigenic and pro-angiogenic potential of glioblastoma

Glioblastoma multiforme (GBM) is a highly vascularized and aggressive brain tumor, with a strong ability to disseminate and invade the surrounding parenchyma. In addition, a subpopulation of GBM stem cells has been reported to possess the ability to transdifferentiate into tumor-derived endothelial cells (TDECs), supporting the resistance to anti-angiogenic treatments of newly formed blood vessels. Bone Morphogenetic Protein 9 (BMP9) is critically involved in the processes of cancer cell differentiation, invasion and metastasis, representing a potential tool in order to impair the intrinsic GBM aggressiveness. Here we demonstrate that BMP9 is able to trigger the activation of SMADs in patient-derived GBM cells, and to strongly inhibit proliferation and invasion by reducing the activation of PI3K/AKT/MAPK and RhoA/Cofilin pathways, respectively. Intriguingly, BMP9 treatment is sufficient to induce a strong differentiation of GBM stem-like cells and to significantly counteract the already reported process of GBM cell transdifferentiation into TDECs not only in in vitro mimicked TDEC models, but also in vivo in orthotopic xenografts in mice. Additionally, we describe a strong BMP9-mediated inhibition of the whole angiogenic process engaged during GBM tumor formation. Based on these results, we believe that BMP9, by acting at multiple levels against GBM cell aggressiveness, can be considered a promising candidate, to be further developed, for the future therapeutic management of GBM.