Cell confluence induces switching from proliferation to migratory signaling by site-selective phosphorylation of PDGF receptors on lipid raft platforms

The Three Pillars of Glioblastoma: A Systematic Review and Novel Analysis of Multi-Omics and Clinical Data

Glioblastoma is the most fatal and common malignant brain tumor, excluding metastasis and with a median survival of approximately one year. While solid tumors benefit from newly approved drugs, immunotherapy, and prevention, none of these scenarios are opening for glioblastoma. The key to unlocking the peculiar features of glioblastoma is observing its molecular and anatomical features tightly entangled with the host's central nervous system (CNS). In June 2024, we searched the PUBMED electronic database. Data collection and analysis were conducted independently by two reviewers. Results: A total of 215 articles were identified, and 192 were excluded based on inclusion and exclusion criteria. The remaining 23 were used for collecting divergent molecular pathways and anatomical features of glioblastoma. The analysis of the selected papers revealed a multifaced tumor with extreme variability and cellular reprogramming that are observable within the same patient. All the variability of glioblastoma could be clustered into three pillars to dissect the physiology of the tumor: 1. necrotic core; 2. vascular proliferation; 3. CNS infiltration. These three pillars support glioblastoma survival, with a pivotal role of the neurovascular unit, as supported by the most recent paper published by experts in the field.

A novel PDGFR inhibitor WQ-C-401 prevents pulmonary vascular remodeling in rats with monocrotaline-induced pulmonary arterial hypertension

Platelet-derived growth factor (PDGF) is one of the most important cytokines associated with pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). PDGF receptor (PDGFR) inhibition exerted therapeutic effects on PAH in clinical trials, but serious side effects warrant the withdrawal of existing drugs. In this study, a novel highly selective PDGFR inhibitor WQ-C-401 was developed, and its effects on PDGFR signaling pathway and pulmonary vascular remodeling in PAH were investigated. Cell proliferation assays and Western blot analysis of PDGFRα/β phosphorylation showed that WQ-C-401 inhibited PDGFR-mediated cell proliferation assay and suppressed PDGFR phosphorylation in a concentration-dependent manner. DiscoverX's KinomeScanTM technology confirmed the good kinome selectivity of WQ-C-401 (S score (1) of PDGFR = (0.01)). In monocrotaline (MCT)-induced PAH rats, intragastric administration of WQ-C-401 (25, 50, 100 mg/kg/d) or imatinib (50 mg/kg/d, positive control) significantly decreased right ventricular systolic pressure (RVSP). Histological analysis demonstrated that WQ-C-401 inhibited pulmonary vascular remodeling by reducing muscularization and fibrosis, as well as alleviated right ventricular hypertrophy in MCT-treated rats. In addition, WQ-C-401 suppressed MCT-induced cell hyperproliferation and CD68+ macrophage infiltration around the pulmonary artery. In vitro, WQ-C-401 inhibited PDGF-BB-induced proliferation and migration of human pulmonary arterial smooth muscle cells (PASMCs). Moreover, Western blot analysis showed that WQ-C-401 concertration-dependently inhibited PDGF-BB-induced phosphorylation of ERK1/2 and PDGFRβ Y751, decreased collagen Ⅰ synthesis and increased alpha smooth muscle actin (α-SMA) expression in PASMCs. Collectively, our results suggest that WQ-C-401 is a selective and potent PDGFR inhibitor which could be a promising drug for the therapeutics of PAH by preventing pulmonary vascular remodeling.

Current status of drugs targeting PDGF/PDGFR

As an important proangiogenic factor, platelet-derived growth factor (PDGF) and its receptor PDGFR are highly expressed in a variety of tumors, fibrosis, cardiovascular and neurodegenerative diseases. Targeting the PDGF/PDGFR pathway is therefore a promising therapeutic strategy. At present, a variety of PDGF/PDGFR targeted drugs with potential therapeutic effects have been developed, mainly including PDGF agonists, inhibitors targeting PDGFR and proteolysis targeting chimera (PROTACs). This review clarifies the structure, biological function and disease correlation of PDGF and PDGFR, and it discusses the current status of PDGFR-targeted drugs, so as to provide a reference for subsequent research.

Biomimetic Scaffolds-A Novel Approach to Three Dimensional Cell Culture Techniques for Potential Implementation in Tissue Engineering

Biomimetic scaffolds imitate native tissue and can take a multidimensional form. They are biocompatible and can influence cellular metabolism, making them attractive bioengineering platforms. The use of biomimetic scaffolds adds complexity to traditional cell cultivation methods. The most commonly used technique involves cultivating cells on a flat surface in a two-dimensional format due to its simplicity. A three-dimensional (3D) format can provide a microenvironment for surrounding cells. There are two main techniques for obtaining 3D structures based on the presence of scaffolding. Scaffold-free techniques consist of spheroid technologies. Meanwhile, scaffold techniques contain organoids and all constructs that use various types of scaffolds, ranging from decellularized extracellular matrix (dECM) through hydrogels that are one of the most extensively studied forms of potential scaffolds for 3D culture up to 4D bioprinted biomaterials. 3D bioprinting is one of the most important techniques used to create biomimetic scaffolds. The versatility of this technique allows the use of many different types of inks, mainly hydrogels, as well as cells and inorganic substances. Increasing amounts of data provide evidence of vast potential of biomimetic scaffolds usage in tissue engineering and personalized medicine, with the main area of potential application being the regeneration of skin and musculoskeletal systems. Recent papers also indicate increasing amounts of in vivo tests of products based on biomimetic scaffolds, which further strengthen the importance of this branch of tissue engineering and emphasize the need for extensive research to provide safe for humansbiomimetic tissues and organs. In this review article, we provide a review of the recent advancements in the field of biomimetic scaffolds preceded by an overview of cell culture technologies that led to the development of biomimetic scaffold techniques as the most complex type of cell culture.

The emerging complexity of PDGFRs: activation, internalization and signal attenuation

The platelet-derived growth factor receptor (PDGFR) family of receptor tyrosine kinases allows cells to communicate with the environment to regulate diverse cellular activities. Here, we highlight recent data investigating the structural makeup of individual PDGFRs upon activation, revealing the importance of the whole receptor in the propagation of extracellular ligand binding and dimerization. Furthermore, we review ongoing research demonstrating the significance of receptor internalization and signal attenuation in the regulation of PDGFR activity. Interactions with internalization machinery, signaling from endosomes, receptor degradation and receptor recycling are physiological means by which cells fine-tune PDGFR responses to growth factor stimulation. In this review, we discuss the biophysical, structural, in silico and biochemical data that have provided evidence for these mechanisms. We further highlight the commonalities and differences between PDGFRα and PDGFRβ signaling, revealing critical gaps in knowledge. In total, this review provides a conclusive summary on the state of the PDGFR field and underscores the need for novel techniques to fully elucidate the mechanisms of PDGFR activation, internalization and signal attenuation.

[Effects of lentivirus-mediated insulin-like growth factor 1 and platelet derived growth factor genes on nucleus pulposus tissue of human degenerated intervertebral disc]

OBJECTIVE

To observe and compare the cytological and biological differences between human normal and degenerated nucleus pulposus (NP), and to investigate the repair effect of insulin-like growth factor 1 (IFG-1) and platelet derived growth factor (PDGF) on human degenerated NP.

METHODS

Human degenerative and normal NP tissues were obtained from operative patients, a portion of which were processed into tissue sections and HE staining was performed to observe the morphological changes of nucleus pulposus cells (NPCs) before and after degeneration of NP. Immunohistochemistry staining was used to determine the expression levels of collagen type Ⅰ, collagen type Ⅱ, B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X (Bax) proteins. Another portion of tissues were isolated and cultured and NPCs morphology was observed under inverted microscope. Western blot analysis was used to detect collagen type Ⅱ protein expression. Then, the gene transfection experiments were launched, including 4 groups, with group A designed as degenerated NPCs only, and groups B, C, and D of degenerated NPCs transfected with IGF-1 gene lentiviral particles, PDGF gene lentiviral particles, and lentiviral particles carrying IGF-1 and PDGF double genes, respectively. At 21 days after transfection, the cell morphology of each group was observed under inverted microscope, the positive rates of IGF-1 and PDGF of each group were measured by flow cytometry, and the expression of collagen type Ⅱ protein was detected by using immunohistochemistry staining and Western blot.

RESULTS

HE staining showed that there were a large number of notochordal cells and a small number of chondrocytes in the central NP tissue of normal group, while the NPCs in degeneration group were significantly reduced, and a large proportion of fibrocartilage tissues were found in NP tissue. Immunohistochemistry staining showed that the percentages of collagen type Ⅰ and Bax protein-positive cells in degeneration group were significantly higher than those of normal group, while the percentages of collagen type Ⅱ and Bcl-2 protein-positive cells were significantly lower than those of normal group ( P<0.05). Western blot showed that the relative expression level of collagen type Ⅱ protein in degeneration group was significantly lower than that in normal group ( t=65.493, P=0.000). At 21 days after gene transfection, compared with group A, the cell viability of groups B, C, and D increased and the morphology became more regular. Flow cytometry showed that the percentages of IGF-1-positive cells in groups B and D were significantly higher than that in group A, and the percentages of PDGF-positive cells in groups C and D were significantly higher than that in group A ( P<0.05). Immunohistochemistry staining showed that the positive stainings of collagen type Ⅱ in groups A, B, C, and D was (±), (+), (+), and (++), respectively. Western blot showed that the relative expression of collagen type Ⅱ protein in groups A, B, C, and D increased by degrees, and the differences between groups were significant ( P<0.05).

CONCLUSION

Both IGF-1 and PDGF can reverse the degeneration of intervertebral discs NPCs and they have synergistic effects, providing experimental basis for its application in clinical treatment approaches for degenerative disc disease.

Ras signals principally via Erk in G1 but cooperates with PI3K/Akt for Cyclin D induction and S-phase entry

Numerous studies exploring oncogenic Ras or manipulating physiological Ras signalling have established an irrefutable role for Ras as driver of cell cycle progression. Despite this wealth of information the precise signalling timeline and effectors engaged by Ras, particularly during G1, remain obscure as approaches for Ras inhibition are slow-acting and ill-suited for charting discrete Ras signalling episodes along the cell cycle. We have developed an approach based on the inducible recruitment of a Ras-GAP that enforces endogenous Ras inhibition within minutes. Applying this strategy to inhibit Ras stepwise in synchronous cell populations revealed that Ras signaling was required well into G1 for Cyclin D induction, pocket protein phosphorylation and S-phase entry, irrespective of whether cells emerged from quiescence or G2/M. Unexpectedly, Erk, and not PI3K/Akt or Ral was activated by Ras at mid-G1, albeit PI3K/Akt signalling was a necessary companion of Ras/Erk for sustaining cyclin-D levels and G1/S transition. Our findings chart mitogenic signaling by endogenous Ras during G1 and identify limited effector engagement restricted to Raf/MEK/Erk as a cogent distinction from oncogenic Ras signalling.

Glucose-regulated protein 78 in lipid rafts elevates vascular smooth muscle cell proliferation of spontaneously hypertensive rats by controlling platelet-derived growth factor receptor signaling

The multifunctional glucose-regulated protein 78 (GRP78) is known to be differentially expressed in the lipid rafts of vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHRs) and normal Wistar-Kyoto (WKY) rats. However, its role in VSMCs from SHRs remains to be elucidated. This work was conducted to investigate the contribution made by GRP78 in VSMCs. GRP78 expression in VSMC lipid rafts decreased in WKY rats with age, but not in SHRs. Transfection with GRP78-siRNA attenuated not only platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation and aortic sprout outgrowth but also the phosphorylation of PDGF receptor (PDGFR)-β, Akt, and extracellular signal-regulated kinase (Erk) 1/2 in VSMCs in response to PDGF-BB. Moreover, GRP78 knockdown also reduced the PDGF-BB-induced dimerization of PDGFR-β and GRP78 in SHR VSMCs. The phosphorylation of GRP78 and PDGFR-β was elevated in VSMCs treated with PDGF-BB and was completely abolished by AG1296 (a PDGFR inhibitor). Moreover, the binding of PDGFR-β to GRP78 and the co-localization of GRP78 to PDGFR-β in VSMCs were stronger in SHRs than in WKY rat controls. This study demonstrates that the PDGF-BB-induced proliferation of SHR VSMCs is mediated by the expressional upregulation of GRP78 on VSMC lipid rafts in SHRs, probably via the regulation of PDGFR-β-GRP78 binding and their cross-activation. These observations indicate that GRP78 may play important roles in the pathological progression of SHR VSMCs.

Human airway smooth muscle cell proliferation from asthmatics is negatively regulated by semaphorin3A

Airway smooth muscle (ASM) hyperplasia is a key feature of airway remodeling in development of lung diseases such as asthma. Anomalous proliferation of ASM cells directly contributes to ASM hyperplasia. However, the molecular mechanisms controlling ASM cell proliferation are not completely understood. Semaphorins are versatile regulators of various cellular processes including cell growth and proliferation. The role of semaphorins in ASM cell proliferation has remained to be addressed. Here, we report that semaphorin 3A (Sema3A) receptor, neuropilin 1 (Nrp1), is expressed on human ASM cells (HASMC) isolated from healthy and asthmatic donors and treatment of these cells with exogenous Sema3A inhibits growth factor-induced proliferation. Sema3A inhibitory effect on HASMC proliferation is associated with decreased tyrosine phosphorylation of PDGFR, downregulation of Rac1 activation, STAT3 and GSK-3β phosphorylation. Bronchial sections from severe asthmatics displayed immunoreactivity of Nrp1, suggestive of functional contribution of Sema3A-Nrp1 axis in airway remodeling. Together, our data suggest Sema3A-Nrp1 signaling as a novel regulatory pathway of ASM hyperplasia.

Involvement of platelet-derived growth factor ligands and receptors in tumorigenesis

Platelet-derived growth factor (PDGF) isoforms and their receptors have important roles during embryogenesis, particularly in the development of various mesenchymal cell types in different organs. In the adult, PDGF stimulates wound healing and regulates tissue homeostasis. However, overactivity of PDGF signalling is associated with malignancies and other diseases characterized by excessive cell proliferation, such as fibrotic conditions and atherosclerosis. In certain tumours, genetic or epigenetic alterations of the genes for PDGF ligands and receptors drive tumour cell proliferation and survival. Examples include the rare skin tumour dermatofibrosarcoma protuberance, which is driven by autocrine PDGF stimulation due to translocation of a PDGF gene, and certain gastrointestinal stromal tumours and leukaemias, which are driven by constitute activation of PDGF receptors due to point mutations and formation of fusion proteins of the receptors, respectively. Moreover, PDGF stimulates cells in tumour stroma and promotes angiogenesis as well as the development of cancer-associated fibroblasts, both of which promote tumour progression. Inhibitors of PDGF signalling may thus be of clinical usefulness in the treatment of certain tumours.

Sialidase NEU3 defines invasive potential of human glioblastoma cells by regulating calpain-mediated proteolysis of focal adhesion proteins

BACKGROUND

Glioblastoma multiforme is one of the most malignant tumors of the human central nervous system characterized by high degree of invasiveness. Focusing on this invasive nature, we investigated whether ganglioside-specific sialidase NEU3 might be involved, because gangliosides are major components of brain tissues, and cell surface sialic acids, as target residues of sialidase catalysis, are thought to be closely related to cell invasion.

METHODS

NEU3 mRNA levels of human glioblastoma specimens were evaluated by quantitative RT-PCR. Human glioblastoma cell lines, U251, A172, and T98G were used for cell invasion and migration by transwell and cell scratching assay. The molecules involved in the signaling cascade were investigated by western blot and immunofluorescent microscopy.

RESULTS

NEU3 expression was down-regulated in human glioblastoma specimens. In the human glioblastoma cell lines, NEU3 overexpression reduced invasion and migration by promoting the assembly of focal adhesions through reduced calpain-dependent proteolysis, but NEU3 silencing resulted in accelerating cell invasion via disassembly of focal adhesions. In NEU3-silenced cells, elevation of calpain activity and GM3 accumulation were observed, as results of reduced sialidase hydrolysis, localization of calpain and GM3 at the cell lamellipodium being demonstrated by immunofluorescence microscopy.

CONCLUSION

Sialidase NEU3 was found to exert a great influence on cell invasion in regulation of calpain activity and focal adhesion disassembly and consequent invasive potential of glioblastoma cells.

GENERAL SIGNIFICANCE

This first demonstration of sialidase involvement in invasive potential of gliolastoma cells may point to NEU3 as an attractive treatment target of human gliomas.