Angiogenesis stimulated by PDGF-CC, a novel member in the PDGF family, involves activation of PDGFR-alphaalpha and -alphabeta receptors

The effect of fibroblast growth factor 2 on neovascular vessels depends on the stage of angiogenesis

Objective

The exact relationship between fibroblast growth factor 2 (FGF2) and choroidal neovascularization (CNV) remains unclear. In this study, using optical coherence tomography angiography (OCTA) and FGF2-tg mice which are transgenic mice with a rhodopsin promoter/FGF2 gene fusion, we aimed to investigate the dynamics of FGF2's role in angiogenesis over time.

Methods

We developed laser-induced CNV models of FGF2-tg and wild-type (WT) mice and then separated them into two groups using different laser photocoagulation (PC) conditions. The first group received 3 intense PC shots (1st PC) altogether (one-time PC group), while the other group received 3 intense PC shots (1st PC) followed by 6 additional weak PC shots (2 nd PC) on the 7th day after 1st PC (two-times PC group).

Results

Using OCTA to observe vessel changes within the same individual over time, there was no difference in the timing of vessel transition from the CNV development phase to the CNV regression phase between FGF2-tg and WT mice in the one-time PC group. In contrast, the neovascular vessels in the two-times PC group of FGF2-tg mice were maintained at least 28 days post-2nd PC without regression. In addition, mature vessels surrounded by PDGFRβ positive pericytes and α-SMA positive smooth muscle cells were observed. Real-time qPCR showed a substantial increase in apelin mRNA expression in the one-time PC group of FGF2-tg, rather than VEGF-A (p < 0.05, n = 5 or 6). Moreover, the expression levels of PDGFRβ, apelin, and Ang1 were significantly higher in FGF2-tg mice of two-times PC group than in WT mice (p < 0.05, n = 5 or 6).

Conclusions

FGF2 not only promotes neovascularization via the apelin/APJ system, which is independent of VEGF signaling pathway, but also helps maintain and stabilize pre-existing neovascular vessels by stimulating PDGFRβ and Ang1. The effect of FGF2 on the neovascular vessels depends on the stage of angiogenesis.

The interaction of platelet-related factors with tumor cells promotes tumor metastasis

Platelets not only participate in thrombosis and hemostasis but also interact with tumor cells and protect them from mechanical damage caused by hemodynamic shear stress and natural killer cell lysis, thereby promoting their colonization and metastasis to distant organs. Platelets can affect the tumor microenvironment via interactions between platelet-related factors and tumor cells. Metastasis is a key event in cancer-related death and is associated with platelet-related factors in lung, breast, and colorectal cancers. Although the factors that promote platelet expression vary slightly in terms of their type and mode of action, they all contribute to the overall process. Recognizing the correlation and mechanisms between these factors is crucial for studying the colonization of distant target organs and developing targeted therapies for these three types of tumors. This paper reviews studies on major platelet-related factors closely associated with metastasis in lung, breast, and colorectal cancers.

CDK4/6 inhibitors induce breast cancer senescence with enhanced anti-tumor immunogenic properties compared with DNA-damaging agents

Since therapy-induced senescence (TIS) can either support or inhibit cancer progression, identifying which types of chemotherapeutic agents can produce the strongest anti-tumor TIS is an important issue. Here, cyclin-dependent kinase4/6 inhibitors (CDK4/6i)-induced senescence was compared to the TIS induced by conventional DNA-damaging agents. Despite both types of agents eliciting a similar degree of senescence, we observed increased expression of the senescence-associated secretory phenotype (SASP) and ligands related to pro-tumor immunity (IL6, CXCL8, TGFβ, CD274, and CEACAM1) and angiogenesis (VEGFA) mainly in TIS induced by DNA-damaging agents rather than by CDK4/6i. Additionally, although all agents increased the expression of anti-tumor immunomodulatory proteins related to antigen presentation (MHC-I, B2M) and T cell chemokines (CXCL9, 10, 11), CDK4/6i-induced senescent cells still maintained this expression at a similar or even higher intensity than cells treated with DNA-damaging agents, despite the absence of nuclear factor-kappa-B (NF-κB) and p53 activation. These data suggest that in contrast with DNA-damaging agents, which augment the pro-tumorigenic microenvironment via pro-inflammatory SASP, CDK4/6i can generate TIS only with antitumor immunomodulatory proteins.

PDGF-C promotes cell proliferation partially via downregulating BOP1

Platelet-derived growth factor C (PDGF-C) is a member of PDGF/VEGF family, which is well-known for important functions in the vascular system. It is widely reported that PDGF-C is able to modulate cell proliferation. However, it is still not very clear about this cell modulating mechanism at the molecular level. In a screening of factors regulated by PDGF-C protein, we fished out a factor called block of proliferation 1 (BOP1), which is a pivotal regulator of ribosome biogenesis and cell proliferation. In this study, we investigated the regulation of BOP1 by PDGF-C and its role in modulating cell proliferation. We found that BOP1 was downregulated at both mRNA and protein levels in cells treated with PDGF-C-containing conditioned medium. On the other hand, BOP1 was upregulated in PDGF-C deficient mice. Furthermore, we confirmed that overexpression of BOP1 inhibited HEK293A cell proliferation, whereas knockdown of BOP1 promoted cell proliferation. The mitogenic effect of PDGF-C could be attenuated by downregulation of BOP1. Our results demonstrate a clear PDGF-C-BOP1 signaling that modulates cell proliferation.

Mapping cardiac remodeling in chronic kidney disease

Patients with advanced chronic kidney disease (CKD) mostly die from sudden cardiac death and recurrent heart failure. The mechanisms of cardiac remodeling are largely unclear. To dissect molecular and cellular mechanisms of cardiac remodeling in CKD in an unbiased fashion, we performed left ventricular single-nuclear RNA sequencing in two mouse models of CKD. Our data showed a hypertrophic response trajectory of cardiomyocytes with stress signaling and metabolic changes driven by soluble uremia-related factors. We mapped fibroblast to myofibroblast differentiation in this process and identified notable changes in the cardiac vasculature, suggesting inflammation and dysfunction. An integrated analysis of cardiac cellular responses to uremic toxins pointed toward endothelin-1 and methylglyoxal being involved in capillary dysfunction and TNFα driving cardiomyocyte hypertrophy in CKD, which was validated in vitro and in vivo. TNFα inhibition in vivo ameliorated the cardiac phenotype in CKD. Thus, interventional approaches directed against uremic toxins, such as TNFα, hold promise to ameliorate cardiac remodeling in CKD.

Molecular and spatial landmarks of early mouse skin development

A wealth of specialized cell populations within the skin facilitates its hair-producing, protective, sensory, and thermoregulatory functions. How the vast cell-type diversity and tissue architecture develops is largely unexplored. Here, with single-cell transcriptomics, spatial cell-type assignment, and cell-lineage tracing, we deconstruct early embryonic mouse skin during the key transitions from seemingly uniform developmental precursor states to a multilayered, multilineage epithelium, and complex dermal identity. We identify the spatiotemporal emergence of hair-follicle-inducing, muscle-supportive, and fascia-forming fibroblasts. We also demonstrate the formation of the panniculus carnosus muscle (PCM), sprouting blood vessels without pericyte coverage, and the earliest residence of mast and dendritic immune cells in skin. Finally, we identify an unexpected epithelial heterogeneity within the early single-layered epidermis and a signaling-rich periderm layer. Overall, this cellular and molecular blueprint of early skin development-which can be explored at https://kasperlab.org/tools-establishes histological landmarks and highlights unprecedented dynamic interactions among skin cells.

The effect of Xuezhikang capsule on gene expression profile in brown adipose tissue of obese spontaneously hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

Obesity is a critical threat to global health, and brown adipose tissue (BAT) is a potential target for the treatment of obesity and comorbidities. Xuezhikang Capsule (XZK), an extract of red yeast rice, has remarkable clinical efficacy and is widely used for the treatment of hyperlipidemia and coronary heart disease. However, its modulatory effect on BAT remains unknown.

AIM OF THIS STUDY

The aim of this study was to investigate the protective mechanism of XZK in the obese spontaneously hypertensive rat (SHR) model by evaluating the regulatory effect of XZK on the BAT gene profile through transcriptome sequencing.

MATERIALS AND METHODS

The SHRs were randomly divided into four groups: the standard chow diet (STD) group, the STD supplemented with 126 mg/kg of XZK group, the high-fat diet (HFD) group, and the HFD supplemented with 126 mg/kg of XZK group. All SHRs were fed for 18 weeks. The metabolic phenotypes, including body weight, fat mass, oral glucose tolerance test (OGTT), and serum glucose and lipid levels, was evaluated, and hematoxylin and eosin staining (H&E) staining was performed to evaluate the adipose tissue histopathological phenotype. Transcriptome sequencing was performed to determine the mechanism by which XZK improves the metabolic phenotype and the expression of key differential expression genes was verified by real-time quantitative polymerase chain reaction (qRT-PCR).

RESULTS

XZK inhibited HFD-induced weight gain and adipose tissue remodeling in SHRs and prevented hypertrophy of epididymal adipocytes and maintained the brown fat phenotype. XZK intervention also improved glucose and lipid metabolism in SHRs, as suggested by a reduction in serum triglyceride (TG), low-density cholesterol (LDL-C), and fasting blood glucose (FBG) levels as well as increasing in serum high-density cholesterol (HDL-C) levels. Transcriptome sequencing analysis confirmed the regulatory effect of XZK on the gene expression profile of BAT, and the expression patterns of 45 genes were reversed by the XZK intervention. Additionally, the results of the transcriptome analysis of 10 genes that are important for brown fat function were in line with the results of qRT-PCR.

CONCLUSIONS

XZK protected SHRs from HFD-induced obesity, inhibited fat accumulation and improved glucolipid metabolism. Additionally, the protective effect of XZK on the overall metabolism of obese SHRs might partly be related to its regulatory effect on the BAT gene expression profile. These findings might provide novel therapeutic strategies for obesity-related metabolic diseases in traditional Chinese medicine (TCM).

PDGF inhibits BMP2-induced bone healing

Bone regeneration depends on a pool of bone/cartilage stem/progenitor cells and signaling mechanisms regulating their differentiation. Using in vitro approach, we have shown that PDGF signaling through PDGFRβ inhibits BMP2-induced osteogenesis, and significantly attenuates expression of BMP2 target genes. We evaluated outcomes of treatment with two anabolic agents, PDGF and BMP2 using different bone healing models. Targeted deletion of PDGFRβ in αSMA osteoprogenitors, led to increased callus bone mass, resulting in improved biomechanical properties of fractures. In critical size bone defects BMP2 treatment increased proportion of osteoprogenitors, while the combined treatment of PDGF BB with BMP2 decreased progenitor number at the injury site. BMP2 treatment induced significant bone formation and increased number of osteoblasts, while in contrast combined treatment with PDGF BB decreased osteoblast numbers. This is in vivo study showing that PDGF inhibits BMP2-induced osteogenesis, but inhibiting PDGF signaling early in healing process does not improve BMP2-induced bone healing.

Micro-RNA193a-3p Inhibits Breast Cancer Cell Driven Growth of Vascular Endothelial Cells by Altering Secretome and Inhibiting Mitogenesis: Transcriptomic and Functional Evidence

Breast cancer (BC) cell secretome in the tumor microenvironment (TME) facilitates neo-angiogenesis by promoting vascular endothelial cell (VEC) growth. Drugs that block BC cell growth or angiogenesis can restrict tumor growth and are of clinical relevance. Molecules that can target both BC cell and VEC growth as well as BC secretome may be more effective in treating BC. Since small non-coding microRNAs (miRs) regulate cell growth and miR193a-3p has onco-suppressor activity, we investigated whether miR193a-3p inhibits MCF-7-driven growth (proliferation, migration, capillary formation, signal transduction) of VECs. Using BC cells and VECs grown in monolayers or 3D spheroids and gene microarrays, we demonstrate that: pro-growth effects of MCF-7 and MDA-MB231 conditioned medium (CM) are lost in CM collected from MCF-7/MDA-MB231 cells pre-transfected with miR193a-3p (miR193a-CM). Moreover, miR193a-CM inhibited MAPK and Akt phosphorylation in VECs. In microarray gene expression studies, miR193a-CM upregulated 553 genes and downregulated 543 genes in VECs. Transcriptomic and pathway enrichment analysis of differentially regulated genes revealed downregulation of interferon-associated genes and pathways that induce angiogenesis and BC/tumor growth. An angiogenesis proteome array confirmed the downregulation of 20 pro-angiogenesis proteins by miR193a-CM in VECs. Additionally, in MCF-7 cells and VECs, estradiol (E2) downregulated miR193a-3p expression and induced growth. Ectopic expression of miR193a-3p abrogated the growth stimulatory effects of estradiol E2 and serum in MCF-7 cells and VECs, as well as in MCF-7 and MCF-7+VEC 3D spheroids. Immunostaining of MCF-7+VEC spheroid sections with ki67 showed miR193a-3p inhibits cell proliferation. Taken together, our findings provide first evidence that miR193a-3p abrogates MCF-7-driven growth of VECs by altering MCF-7 secretome and downregulating pro-growth interferon signals and proangiogenic proteins. Additionally, miR193a-3p inhibits serum and E2-induced growth of MCF-7, VECs, and MCF-7+VEC spheroids. In conclusion, miRNA193a-3p can potentially target/inhibit BC tumor angiogenesis via a dual mechanism: (1) altering proangiogenic BC secretome/TME and (2) inhibiting VEC growth. It may represent a therapeutic molecule to target breast tumor growth.

Role of platelet-derived growth factor c on endothelial dysfunction in cardiovascular diseases

Loss of endothelial function is a common feature to all cardiovascular diseases (CVDs). One of the risk factors associated with the development of CVDs is the hyperglycaemia that occurs in patients with metabolic disorders such as Type 1 and Type 2 diabetes mellitus. Hyperglycaemia causes endothelial dysfunction through increased production of reactive oxygen species (ROS) from different cellular sources leading to oxidative stress. Vascular endothelial growth factor (VEGF) is essential in the stimulation and maintenance of endothelial functional aspects and, although it can mitigate the impact of ROS, VEGF-mediated signalling is partially inhibited in diabetes mellitus. The search for therapeutic strategies that preserve, protect and improve the functions of the endothelium is of great relevance in the investigation of CVDs associated with hyperglycaemia. Platelet-derived growth factor C (PDGF-C) is a peptide with angiogenic properties, independent of VEGF, that stimulates angiogenesis and revascularization of ischemic tissue. In a diabetic mouse model, PDGF-C stimulates mature endothelial cell migration, angiogenesis, endothelial progenitor cell mobilization, and increased neovascularization, and protects blood vessels in a retinal degeneration model activating anti-apoptosis and proliferation signalling pathways in endothelial cells. This review summarizes the information on the damage that high d-glucose causes on endothelial function and the beneficial effects that PDGF-CC could exert in this condition.

Diverse roles of tumor-stromal PDGFB-to-PDGFRβ signaling in breast cancer growth and metastasis

Over the last couple of decades, it has become increasingly apparent that the tumor microenvironment (TME) mediates every step of cancer progression and solid tumors are only able to metastasize with a permissive TME. This intricate interaction of cancer cells with their surrounding TME, or stroma, is becoming more understood with an ever greater knowledge of tumor-stromal signaling pairs such as platelet-derived growth factors (PDGF) and their cognate receptors. We and others have focused our research efforts on understanding how tumor-derived PDGFB activates platelet-derived growth factor receptor beta (PDGFRβ) signaling specifically in the breast cancer TME. In this chapter, we broadly discuss PDGF and PDGFR expression patterns and signaling in normal physiology and breast cancer. We then detail the expansive roles played by the PDGFB-to-PDGFRβ signaling pathway in modulating breast tumor growth and metastasis with a focus on specific cellular populations within the TME, which are responsive to tumor-derived PDGFB. Given the increasingly appreciated importance of PDGFB-to-PDGFRβ signaling in breast cancer progression, specifically in promoting metastasis, we end by discussing how therapeutic targeting of PDGFB-to-PDGFRβ signaling holds great promise for improving current breast cancer treatment strategies.

Platelet-derived growth factor signalling in neurovascular function and disease

Platelet-derived growth factors are critical for cerebrovascular development and homeostasis. Abnormalities in this signalling pathway are implicated in neurological diseases, especially those where neurovascular dysfunction and neuroinflammation plays a prominent role in disease pathologies, such as stroke and Alzheimer's disease; the angiogenic nature of this pathway also draws its significance in brain malignancies such as glioblastoma where tumour angiogenesis is profuse. In this review, we provide an updated overview of the actions of the platelet-derived growth factors on neurovascular function, their role in the regulation of perivascular cell types expressing the cognate receptors, neurological diseases associated with aberrance in signalling, and highlight the clinical relevance and therapeutic potentials of this pathway for central nervous system diseases.

Hypoxia-Mimetic CoCl2 Agent Enhances Pro-Angiogenic Activities in Ovine Amniotic Epithelial Cells-Derived Conditioned Medium

Amniotic epithelial stem cells (AECs) are largely studied for their pro-regenerative properties. However, it remains undetermined if low oxygen (O₂) levels that AECs experience in vivo can be of value in maintaining their biological properties after isolation. To this aim, the present study has been designed to evaluate the effects of a hypoxia-mimetic agent, cobalt chloride (CoCl₂), on AECs’ stemness and angiogenic activities. First, a CoCl₂ dose-effect was performed to select the concentration able to induce hypoxia, through HIF-1α stabilization, without promoting any cytotoxicity effect assessed through the analysis of cell vitality, proliferation, and apoptotic-related events. Then, the identified CoCl₂ dose was evaluated on the expression and angiogenic properties of AECs’ stemness markers (OCT-4, NANOG, SOX-2) by analysing VEGF expression, angiogenic chemokines’ profiles, and AEC-derived conditioned media activity through an in vitro angiogenic xeno-assay. Results demonstrated that AECs are sensitive to the cytotoxicity effects of CoCl₂. The unique concentration leading to HIF-1α stabilization and nuclear translocation was 10 µM, preserving cell viability and proliferation up to 48 h. CoCl₂ exposure did not modulate stemness markers in AECs while progressively decreasing VEGF expression. On the contrary, CoCl₂ treatment promoted a significant short-term release of angiogenic chemokines in culture media (CM). The enrichment in bio-active factors was confirmed by the ability of CoCl₂-derived CM to induce HUVEC growth and the cells’ organization in tubule-like structures. These findings demonstrate that an appropriate dose of CoCl₂ can be adopted as a hypoxia-mimetic agent in AECs. The short-term, chemical-induced hypoxic condition can be targeted to enhance AECs’ pro-angiogenic properties by providing a novel approach for stem cell-free therapy protocols.

Expression and function of PDGF-C in development and stem cells

Platelet-derived growth factor C (PDGF-C) is a relatively new member of the PDGF family, discovered nearly 20 years after the finding of platelet-derived growth factor A (PDGF-A) and platelet-derived growth factor B (PDGF-B). PDGF-C is generally expressed in most organs and cell types. Studies from the past 20 years have demonstrated critical roles of PDGF-C in numerous biological, physiological and pathological processes, such as development, angiogenesis, tumour growth, tissue remodelling, wound healing, atherosclerosis, fibrosis, stem/progenitor cell regulation and metabolism. Understanding PDGF-C expression and activities thus will be of great importance to various research disciplines. In this review, however, we mainly discuss the expression and functions of PDGF-C and its receptors in development and stem cells.

The Cellular Prion Protein and the Hallmarks of Cancer

Simple Summary

The cellular prion protein PrP^C is best known for its involvement, under its pathogenic isoform, in a group of neurodegenerative diseases. Notwithstanding, an emerging role for PrP^C in various cancer-associated processes has attracted increasing attention over recent years. PrP^C is overexpressed in diverse types of solid cancers and has been incriminated in various aspects of cancer biology, most notably proliferation, migration, invasion and metastasis, as well as resistance to cytotoxic agents. This article aims to provide a comprehensive overview of the current knowledge of PrP^C with respect to the hallmarks of cancer, a reference framework encompassing the major characteristics of cancer cells.

Abstract

Beyond its causal involvement in a group of neurodegenerative diseases known as Transmissible Spongiform Encephalopathies, the cellular prion protein PrP^C is now taking centre stage as an important contributor to cancer progression in various types of solid tumours. The prion cancer research field has progressively expanded in the last few years and has yielded consistent evidence for an involvement of PrP^C in cancer cell proliferation, migration and invasion, therapeutic resistance and cancer stem cell properties. Most recent data have uncovered new facets of the biology of PrP^C in cancer, ranging from its control on enzymes involved in immune tolerance to its radio-protective activity, by way of promoting angiogenesis. In the present review, we aim to summarise the body of literature dedicated to the study of PrP^C in relation to cancer from the perspective of the hallmarks of cancer, the reference framework defined by Hanahan and Weinberg.

Role of PDGF-A/B Ligands in Cardiac Repair After Myocardial Infarction

Platelet-derived growth factors (PDGFs) are powerful inducers of cellular mitosis, migration, angiogenesis, and matrix modulation that play pivotal roles in the development, homeostasis, and healing of cardiac tissues. PDGFs are key signaling molecules and important drug targets in the treatment of cardiovascular disease as multiple researchers have shown that delivery of recombinant PDGF ligands during or after myocardial infarction can reduce mortality and improve cardiac function in both rodents and porcine models. The mechanism involved cannot be easily elucidated due to the complexity of PDGF regulatory activities, crosstalk with other protein tyrosine kinase activators, and diversity of the pathological milieu. This review outlines the possible roles of PDGF ligands A and B in the healing of cardiac tissues including reduced cell death, improved vascularization, and improved extracellular matrix remodeling to improve cardiac architecture and function after acute myocardial injury. This review may highlight the use of recombinant PDGF-A and PDGF-B as a potential therapeutic modality in the treatment of cardiac injury.

Glycosylation at Asn254 Is Required for the Activation of the PDGF-C Protein

Platelet-derived growth factor C (PDGF-C) is a member of the PDGF/VEGF (vascular endothelial growth factor) family, which includes proteins that are well known for their mitogenic effects on multiple cell types. Glycosylation is one of the most important forms of posttranslational modification that has a significant impact on secreted and membrane proteins. Glycosylation has many well-characterized roles in facilitating protein processing and contributes to appropriate folding, conformation, distribution, and stability of proteins that are synthesized intracellularly in the endoplasmic reticulum (ER) and Golgi apparatus. Although the general process and functions of glycosylation are well documented, there are most likely others yet to be discovered, as the glycosylation of many potential substrates has not been characterized. In this study, we report that the PDGF-C protein is glycosylated at three sites, including Asn25, Asn55, and Asn254. However, we found that mutations at any of these sites do not affect the protein expression or secretion. Similarly, disruption of PDGF-C glycosylation had no impact on its progression through the ER and Golgi apparatus. However, the introduction of a mutation at Asn254 (N254 A) prevents the activation of full-length PDGF-C and its capacity for signaling via the PDGF receptor. Our findings reveal that glycosylation affects PDGF-C activation rather than the protein synthesis or processing. This study characterizes a crucial modification of the PDGF-C protein, and may shed new light on the process and function of glycosylation.

Cerebrovascular development: mechanisms and experimental approaches

The cerebral vasculature plays a central role in human health and disease and possesses several unique anatomic, functional and molecular characteristics. Despite their importance, the mechanisms that determine cerebrovascular development are less well studied than other vascular territories. This is in part due to limitations of existing models and techniques for visualisation and manipulation of the cerebral vasculature. In this review we summarise the experimental approaches used to study the cerebral vessels and the mechanisms that contribute to their development.

Co-invalidation of Prnp and Sprn in FVB/N mice affects reproductive performances and highlight complex biological relationship between PrP and Shadoo

Shadoo and PrP belongs to the same protein family, whose biological function remains poorly understood. Previous experiments reported potential functional redundancies or antagonisms between these two proteins, depending on the tissue analysed. While knockdown experiments suggested the requirement of Shadoo in the absence of PrP during early mouse embryogenesis, knockout ones, on the contrary, highlighted little impact, if any, of the double-knockout of these two loci. In the present study, we reinvestigated the phenotype associated with the concomitant knockout of these two genes using newly produced FVB/N Sprn knockout mice. In this genetic background, the combined two genes' knockout induces intra-uterine growth retardations, likely resulting from placental failures highlighted by transcriptomic analyses that revealed potential redundant or antagonist roles of these two proteins in different developmental-related pathways. It also induced an increased perinatal-lethality and ascertained the role of these two loci in the lactation process.

Cancer-associated fibroblast secretion of PDGFC promotes gastrointestinal stromal tumor growth and metastasis

Targeted therapies for gastrointestinal stromal tumor (GIST) are modestly effective, but GIST cannot be cured with single agent tyrosine kinase inhibitors. In this study, we sought to identify new therapeutic targets in GIST by investigating the tumor microenvironment. Here, we identified a paracrine signaling network by which cancer-associated fibroblasts (CAFs) drive GIST growth and metastasis. Specifically, CAFs isolated from human tumors were found to produce high levels of platelet-derived growth factor C (PDGFC), which activated PDGFC-PDGFRA signal transduction in GIST cells that regulated the expression of SLUG, an epithelial-mesenchymal transition (EMT) transcription factor and downstream target of PDGFRA signaling. Together, this paracrine induce signal transduction cascade promoted tumor growth and metastasis in vivo. Moreover, in metastatic GIST patients, SLUG expression positively correlated with tumor size and mitotic index. Given that CAF paracrine signaling modulated GIST biology, we directly targeted CAFs with a dual PI3K/mTOR inhibitor, which synergized with imatinib to increase tumor cell killing and in vivo disease response. Taken together, we identified a previously unappreciated cellular target for GIST therapy in order to improve disease control and cure rates.

Understanding angiogenesis and the role of angiogenic growth factors in the vascularisation of engineered tissues

Tissue engineering is a rapidly developing field with many potential clinical applications in tissue and organ regeneration. The development of a mature and stable vasculature within these engineered tissues (ET) remains a significant obstacle. Currently, several growth factors (GFs) have been identified to play key roles within in vivo angiogenesis, including vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF), FGF and angiopoietins. In this article we attempt to build on in vivo principles to review the single, dual and multiple GF release systems and their effects on promoting angiogenesis. We conclude that multiple GF release systems offer superior results compared to single and dual systems with more stable, mature and larger vessels produced. However, with more complex release systems this raises other problems such as increased cost and significant GF-GF interactions. Upstream regulators and pericyte-coated scaffolds could provide viable alternative to circumnavigate these issues.

Vitreous metabolomics profiling of proliferative diabetic retinopathy

AIMS/HYPOTHESIS

Proliferative diabetic retinopathy (PDR) with retinal neovascularisation (NV) is a leading cause of vision loss. This study identified a set of metabolites that were altered in the vitreous humour of PDR patients compared with non-diabetic control participants. We corroborated changes in vitreous metabolites identified in prior studies and identified novel dysregulated metabolites that may lead to treatment strategies for PDR.

METHODS

We analysed metabolites in vitreous samples from 43 PDR patients and 21 non-diabetic epiretinal membrane control patients from Japan (age 27-80 years) via ultra-high-performance liquid chromatography-mass spectrometry. We then investigated the association of a novel metabolite (creatine) with retinal NV in mouse oxygen-induced retinopathy (OIR). Creatine or vehicle was administered from postnatal day (P)12 to P16 (during induced NV) via oral gavage. P17 retinas were quantified for NV and vaso-obliteration.

RESULTS

We identified 158 metabolites in vitreous samples that were altered in PDR patients vs control participants. We corroborated increases in pyruvate, lactate, proline and allantoin in PDR, which were identified in prior studies. We also found changes in metabolites not previously identified, including creatine. In human vitreous humour, creatine levels were decreased in PDR patients compared with epiretinal membrane control participants (false-discovery rate <0.001). We validated that lower creatine levels were associated with vascular proliferation in mouse retina in the OIR model (p = 0.027) using retinal metabolomics. Oral creatine supplementation reduced NV compared with vehicle (P12 to P16) in OIR (p = 0.0024).

CONCLUSIONS/INTERPRETATION

These results suggest that metabolites from vitreous humour may reflect changes in metabolism that can be used to find pathways influencing retinopathy. Creatine supplementation could be useful to suppress NV in PDR. Graphical abstract.

Expression of angiogenic growth factors in canine squamous cell cancers

Skin and subcutaneous tissue tumors are the most common neoplasms in dogs. The most common sites of origin in dogs include digits, skin and the oral cavity including cheek and retromandibular area. We investigated canine squamous cell carcinoma (SCC) samples from 15 dogs and classified them histopathologically according to the degree of differentiation. bFGF, VEGF-C, TGF-β, PDGF-A, PDGF-C and PDGFR-α expressions were assessed using immunohistochemistry to determine the roles of growth factors during SCC. We found that TGF-β1 immunolabeling was elevated significantly compared to healthy controls in SCC originating from nailbeds, while expression of other growth factors did not change significantly. Our findings might explain the role of TGF-β1 in the infiltrative and malignant behavior of SCC originating from nailbeds.

Analysis of angiogenic and stromal biomarkers in a large malignant mesothelioma cohort

BACKGROUND

Malignant mesothelioma (MM) is an aggressive malignancy of the pleura and other mesothelial membranes. Agents targeting vascular endothelial growth factor (VEGF) such as bevacizumab; and multi-kinase inhibitors such as nintedanib [angiokinase inhibitor of VEGF, platelet-derived growth factor (PDGF) receptor and fibroblast growth factor receptor (FGFR)] have recently demonstrated efficacy in MM.

METHODS

Tissue microarrays (TMAs) were created from formalin-fixed, paraffin-embedded tissue samples obtained from 326 patients with MM who were treated surgically. PDGF-CC, FGFR-1, VEGF and CD31 expression were analysed by immunohistochemical (IHC) staining. The H-score method assigned a score of 0-300 to each sample, based on the percentage of cells stained at different intensities. CD31 was evaluated via Chalkley's method to evaluate microvessel density. We evaluated the association between expression of the biomarkers, clinicopathological factors and outcomes, in patients with MM.

RESULTS

CD31 high (≥5) was seen in only 31/302 (10.3%) irrespective of histology. PDGF-CC high (≥150) was seen in 203 /310 (65%) of all samples. VEGF high (≥80) was seen in 219/322 (68%) of all MM with 143/209 (68%) of epithelioid histology. FGFR-1 high (≥40) was seen in 127/310 (41%) of all MM. There was no association of VEGF and FGFR-1 IHC with survival nor differences between histological subtypes. There was a non-significant trend towards poorer survival in epithelioid tumours with increased PDGF-CC expression (OS 18.5 vs 13.2 months; HR 0.7928; 95% CI 0.5958 to 1.055, P = 0.1110). High CD31 score was associated with significantly poorer survival (OS 12 vs 8.6 months; HR 0.48; 95% CI 0.2873 to 0.7941, P = 0.0044). Of the 31 patients with high CD31 scores; 23/31 (74%) were also high for PDGF-CC and 20/31 (64%) with high VEGF scores. CD31 was found to be an independent prognostic factor in multivariate analysis (HR 1.540; 95% CI 1.018 to 2.330; p = 0.041).

CONCLUSIONS

High CD31 was an independent poor prognostic factor and high PDGF-CC expression was associated with poor survival in MM. Abrogating these pathways may have prognostic implications.

Heterogeneity of cancer-associated fibroblasts: Opportunities for precision medicine

Despite marked development in cancer therapies during recent decades, the prognosis for advanced cancer remains poor. The conventional tumor-cell-centric view of cancer can only explain part of cancer progression, and thus a thorough understanding of the tumor microenvironment (TME) is crucial. Among cells within the TME, cancer-associated fibroblasts (CAFs) are attracting attention as a target for cancer therapy. However, CAFs present a heterogeneous population of cells and more detailed classification of CAFs and investigation of functions of each subset is needed to develop novel CAF-targeted therapies. In this context, application of newly developed approaches to single-cell analysis has already made an impact on our understanding of the heterogeneity of CAFs. Here, we review the recent literature on CAF heterogeneity and function, and discuss the possibility of novel therapies targeting CAF subsets.

Expression levels of circulatory mir-185-5p, vascular endothelial growth factor, and platelet-derived growth factor target genes in endometriosis

BACKGROUND

Using blood-based biomarkers such as microRNAs (miRNAs) may allow particularly effective and minimally invasive diagnosis and treatment of endometriosis. Objective: We evaluated the differential expression of circulating miRNA-185-5p (miR-185-5p), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) target genes between endometriosis and healthy women.

MATERIALS AND METHODS

25 women with a history of endometriosis (grad III-IV) diagnosed by laparoscopy as the case group and 25 women without endometriosis underwent laparoscopy for ovarian cysts or pelvic pain as the control group were enrolled in this case-control study. Blood samples were obtained, and total RNA was used for high-throughput small RNA sequencing, and this was confirmed by means of quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

miRNA expression profiling using non-coding RNA sequencing revealed that one miRNA including miR-185-5p was significantly down-regulated in the case group compared with the controls. The qRT-PCR results showed significant downregulation of the expression level of miR-185-5p (p < 0.01) in the plasma of the case group. Receiver operating characteristic (ROC) curve analysis showed the area of miR-185-5p under the ROC curve for endometriosis diagnosis was 0.919 (p < 0.001). The RT-PCR results demonstrated that there was no significant difference in the expression of VEGF and PDGF mRNA of blood samples in the cases compared to the control group (PDGF, p = 0.09 and VEGF, p = 0.36).

CONCLUSION

The low expression of miR-185-5p in the plasma of women with endometriosis could be employed as an important non-invasive biomarker for early detection and screening of endometriosis by blood samples.

Overexpression of Platelet-Derived Growth Factor and Its Receptor Are Correlated with Oral Tumorigenesis and Poor Prognosis in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a cancerous disease with poor prognosis. According to the statistics, the 5-year survival rate has not improved significantly over the past 20 years. The platelet-derived growth factor (PDGF) and its signaling pathway is a key regulator of angiogenesis and tumorigenesis. High level of PDGF and its receptor (PDGFR) have been reported in several types of malignancies. In this study, we investigated the relationship of the molecular expression levels of PDGF and PDGFR with clinicopathological parameters in OSCC. To this end, we measured the mRNA and protein levels of PDGF and PDGFR by real-time quantitative PCR (qRT-PCR), immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA), respectively. We found positive correlations of the mRNA levels of PDGFA, PDGFB, and PDGFRB with lymph node metastasis and poor overall survival (OS). High expression of PDGF, PDGFRA, and PDGFRB were remarkably associated with lymph node metastasis and poor OS, as determined by immunohistochemistry. Preoperative serum levels of PDGF-AA and PDGF-BB had a positive correlation with preoperative platelet count. Elevated serum levels of PDGF-AA. PDGF-BB, and platelet count correlated with lymph node metastasis and an unfavorable outcome. In multivariate Cox regression analysis, PDGFA mRNA, PDGFB mRNA, PDGFRB mRNA, PDGF immunoexpression, PDGFRB immunoexpression, serum PDGF-AA, serum PDGF-BB, and platelet count emerged as significant independent prognostic factors for OS. In vitro, we found that elevated PDGF promotes colony formation, migration, and invasiveness of SAS and OECM-1 cancer cell lines. Our results suggest that the expression level of serum PDGF has the potential to become a useful diagnostic marker for the prognosis of OSCC. In addition, PDGFR should be considered as a potential therapeutic target for OSCC. Furthermore, research should be undertaken to elucidate the role of PDGF and PDGFR regarding the behavior of tumor cells in OSCC.

Platelet-derived growth factor-BB promotes proliferation and migration of retinal microvascular pericytes by up-regulating the expression of C-X-C chemokine receptor types 4

Stromal cell-derived growth factor (SDF)-1α acts as a ligand to C-X-C chemokine receptors 4 (CXCR4) and 7 (CXCR7), which are involved in the formation of choroidal neovascularization. Previous studies have demonstrated crosstalk between the platelet-derived growth factor (PDGF)-BB/PDGF receptor (PDGFR)-β and SDF-1α/CXCR4 axes during tumor neovascularization by increasing the recruitment of pericytes. However, the effects of interactions between these two signaling pathways in retinal microvascular pericytes remain poorly understood. Western blotting and reverse transcription-quantitative PCR were used to measure CXCR4 and CXCR7 expression in PDGF-BB-treated pericytes, whilst Cell Counting Kit-8 and Transwell migration assays were used to investigate cell viability and migration following PDGF-BB pretreatment on SDF-1α-treated pericytes. Exogenous PDGF-BB enhanced CXCR4 and CXCR7 expression through PDGFR-β in a dose- and time-dependent manners. In addition, PDGF-BB increased cell viability and migration in SDF-1α-treated pericytes, which were inhibited by AMD3100 and niclosamide, inhibitors for CXCR4 and STAT3 respectively. Crosstalk between PDGF-BB/PDGFR-β and SDF-1α/CXCR4/CXCR7 were involved in the JAK2/STAT3 signaling pathway. PDGF-BB treatment enhanced CXCR4, CXCR7 and PDGFR-βexpression, which may be associated with the phosphorylation of STAT3. siRNA-PDGFR-β transfection reduced CXCR4 and CXCR7 expression in pericytes. Therefore, PDGF-BB directly targets PDGFR-β and serves an important role in regulating CXCR4 and CXCR7 expression, ultimately affecting viability and migration in SDF-1α-treated pericytes. Therefore, targeting CXCR4/CXCR7 may serve as a potential therapeutic strategy for fundus diseases.

Similarities and differences between mesenchymal stem/progenitor cells derived from various human tissues

BACKGROUND

Mesenchymal stromal/stem cells (MSCs) constitute a promising tool in regenerative medicine and can be isolated from different human tissues. However, their biological properties are still not fully characterized. Whereas MSCs from different tissue exhibit many common characteristics, their biological activity and some markers are different and depend on their tissue of origin. Understanding the factors that underlie MSC biology should constitute important points for consideration for researchers interested in clinical MSC application.

AIM

To characterize the biological activity of MSCs during longterm culture isolated from: bone marrow (BM-MSCs), adipose tissue (AT-MSCs), skeletal muscles (SM-MSCs), and skin (SK-MSCs).

METHODS

MSCs were isolated from the tissues, cultured for 10 passages, and assessed for: phenotype with immunofluorescence and flow cytometry, multipotency with differentiation capacity for osteo-, chondro-, and adipogenesis, stemness markers with qPCR for mRNA for Sox2 and Oct4, and genetic stability for p53 and c-Myc; 27 bioactive factors were screened using the multiplex ELISA array, and spontaneous fusion involving a co-culture of SM-MSCs with BM-MSCs or AT-MSCs stained with PKH26 (red) or PKH67 (green) was performed.

RESULTS

All MSCs showed the basic MSC phenotype; however, their expression decreased during the follow-up period, as confirmed by fluorescence intensity. The examined MSCs express CD146 marker associated with proangiogenic properties; however their expression decreased in AT-MSCs and SM-MSCs, but was maintained in BM-MSCs. In contrast, in SK-MSCs CD146 expression increased in late passages. All MSCs, except BM-MSCs, expressed PW1, a marker associated with differentiation capacity and apoptosis. BM-MSCs and AT-MSCs expressed stemness markers Sox2 and Oct4 in long-term culture. All MSCs showed a stable p53 and c-Myc expression. BM-MSCs and AT-MSCs maintained their differentiation capacity during the follow-up period. In contrast, SK-MSCs and SM-MSCs had a limited ability to differentiate into adipocytes. BM-MSCs and AT-MSCs revealed similarities in phenotype maintenance, capacity for multilineage differentiation, and secretion of bioactive factors. Because AT-MSCs fused with SM-MSCs as effectively as BM-MSCs, AT-MSCs may constitute an alternative source for BM-MSCs.

CONCLUSION

Long-term culture affects the biological activity of MSCs obtained from various tissues. The source of MSCs and number of passages are important considerations in regenerative medicine.

Novel multi-targeted inhibitors suppress ocular neovascularization by regulating unique gene sets

Neovascular diseases, such as many cancers and ocular disorders, are life threatening and devastating. Although anti-vascular endothelial growth factor A (VEGF-A) therapy is available, many patients are not responsive and drug resistance can develop. To try to overcome these problems, combination therapy targeting VEGF-A and platelet-derived growth factor B (PDGF-B) was tested. However, one obvious drawback was that the other VEGF and PDGF family members were not inhibited and therefore could compensate. Indeed, this was, at least to some extent, demonstrated by the disappointing outcomes. To this end, we designed novel multi-targeted inhibitors that can block most of the VEGF and PDGF family members simultaneously by making a fusion protein containing the ligand-binding domains of vascular endothelial growth factor receptor 1 (VEGFR1), vascular endothelial growth factor receptor 2 (VEGFR2) and platelet-derived growth factor receptor beta (PDGFRβ), which can therefore act as a decoy blocker for most of the VEGF and PDGF family members. Indeed, in cultured cells, the novel inhibitors suppressed the migration and proliferation of both vascular endothelial cells and smooth muscle cells, and abolished VEGFR2 and PDGFRβ activation. Importantly, in a choroidal neovascularization model in vivo, the novel inhibitor inhibited ocular neovascularization more efficiently than the mono-inhibitors against VEGFR or PDGFR alone respectively. Mechanistically, a genome-wide microarray analysis unveiled that the novel inhibitor regulated unique sets of genes that were not regulated by the mono-inhibitors, further demonstrating the functional uniqueness and superiority of the novel inhibitor. Together, we show that the multi-targeted inhibitors that can block VEGFR1, VEGFR2 and PDGFRβ simultaneously suppress pathological angiogenesis more efficiently than monotherapy, and may therefore have promising therapeutic value for the treatment of neovascular diseases.

Mapping Tyrosine Kinase Receptor Dimerization to Receptor Expression and Ligand Affinities

Tyrosine kinase receptor (RTK) ligation and dimerization is a key mechanism for translating external cell stimuli into internal signaling events. This process is critical to several key cell and physiological processes, such as in angiogenesis and embryogenesis, among others. While modulating RTK activation is a promising therapeutic target, RTK signaling axes have been shown to involve complicated interactions between ligands and receptors both within and across different protein families. In angiogenesis, for example, several signaling protein families, including vascular endothelial growth factors and platelet-derived growth factors, exhibit significant cross-family interactions that can influence pathway activation. Computational approaches can provide key insight to detangle these signaling pathways but have been limited by the sparse knowledge of these cross-family interactions. Here, we present a framework for studying known and potential non-canonical interactions. We constructed generalized models of RTK ligation and dimerization for systems of two, three and four receptor types and different degrees of cross-family ligation. Across each model, we developed parameter-space maps that fully determine relative pathway activation for any set of ligand-receptor binding constants, ligand concentrations and receptor concentrations. Therefore, our generalized models serve as a powerful reference tool for predicting not only known ligand: Receptor axes but also how unknown interactions could alter signaling dimerization patterns. Accordingly, it will drive the exploration of cross-family interactions and help guide therapeutic developments across processes like cancer and cardiovascular diseases, which depend on RTK-mediated signaling.

Benefits of Gardening Activities for Cognitive Function According to Measurement of Brain Nerve Growth Factor Levels

The objective of this study was to determine the effects of gardening activities in senior individuals on brain nerve growth factors related to cognitive function. Forty-one senior individuals (age 76.6 ± 6.0 years) were recruited from the local community in Gwangjin-gu, Seoul, South Korea. A 20-min low-to-moderate intensity gardening activity intervention, making a vegetable garden, was performed by the subjects in a garden plot located on the Konkuk University (Seoul, South Korea) campus. The gardening involved six activities including cleaning a garden plot, digging, fertilizing, raking, planting/transplanting, and watering. To determine the effects of the gardening activities on brain nerve growth factors related to memory, blood samples were drawn twice from each subject before and after the gardening activity by professional nurses. The levels of brain nerve growth factors, including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF), were analyzed. Levels of BDNF and PDGF were significantly increased after the gardening activity. This study revealed a potential benefit of gardening activities for cognitive function in senior individuals.

Platelet‑derived growth factor D promotes the angiogenic capacity of endothelial progenitor cells

Neovascularization and re-endothelialization rely on endothelial progenitor cells (EPCs). However, the recruitment and angiogenic roles of EPCs are subject to regulation through the vascular microenvironment, which remains largely unknown. Platelet-derived growth factor D (PDGF-D) is a new member of the PDGF family that binds the PDGFR-β homodimer. However, it remains unknown whether and how it affects the angiogenic capacity of EPCs and participates in tube-like formation. EPCs were derived from rat bone marrow cells, and the gain-of-function approach was used to study the effects of PDGF-D on the biological activities of EPCs. EPCs that stably express PDGF-D were generated by lentiviral-mediated transduction, and the expression levels were evaluated by western blotting and reverse transcription, followed by real-time quantitative polymerase chain reaction (RT-qPCR). The biological activities of EPCs evaluated in the present study included proliferation, adhesion, migration, tube formation and senescence. Furthermore, the downstream signaling of PDGF-D was explored by western blot analysis. The results revealed that the lentiviral-mediated expression of PDGF-D in the microenvironment promoted the migration, proliferation, adhesion and tube formation of EPCs. In addition, PDGF-D suppressed the senescence of EPCs. Mechanistically, PDGF-D induced the phosphorylation of several signaling molecules, including STAT3, AKT, ERK1/2, mTOR and GSK-3β, suggesting that PDGF-D enhanced the angiogenic function of EPCs through PDGF receptor-dependent and -independent signaling pathways. In conclusion, PDGF-D promotes the angiogenic capacity of EPCs, including proliferation, migration, adhesion and tube formation, and thereby contributes to angiogenesis.

Role of the tumor microenvironment in digestive neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.

Progesterone treatment enhances the expansion of placental immature myeloid cells in a mouse model of premature labor

INTRODUCTION

immature-myeloid cells (IMCs) are proangiogenic bone marrow (BM)-derived cells that normally differentiate into inflammatory cells such as neutrophils, monocytes and dendritic cells (DCs). We characterized placental IMCs comparing their gene expression and subpopulations to tumor IMCs, and tested our hypothesis that progesterone that inhibits preterm labor, may affect their abundance and differentiation.

METHODS

differences between IMC-subpopulations in subcutaneous tumors versus placentas in C57BL/6 or ICR (CD-1) mice were analyzed by flow cytometry and gene expression was detected by microarrays. BM- and placental cells were incubated with or without progesterone and IMC subpopulations were analyzed. For preterm labor induction pregnant mice pretreated or not with progesterone were or were not treated with Lipopolysaccharide (LPS).

RESULTS

we detected enrichment of granulocytic-IMCs in placentas compared to tumors, paralleled by a decrease in monocytic-IMCs. mRNA expression of placenta- versus tumor IMCs revealed profound transcriptional alterations. Progesterone treated BM-CD11b⁺ cells ex-vivo induced enrichment of granulocytic-IMCs and a decrease in monocytic-IMCs and DCs. LPS treatment in-vivo led to an increase in BM-IMCs in both progesterone pretreated or non-pretreated mice. In the placenta LPS decreased the IMC population while progesterone led to complete abrogation of this effect.

DISCUSSION

placental IMCs differ from tumor-IMCs in both subpopulations and gene expression. Progesterone enhances the proliferation of placenta-specific granulocytic IMCs ex-vivo and LPS induced labor is accompanied by a decrease in placental IMCs only in progesterone non-pretreated mice. We thus speculate that the protective effect of progesterone in preventing preterm labor may be explained at least in part by this specific anti-inflammatory effect.

Development of monoclonal anti-PDGF-CC antibodies as tools for investigating human tissue expression and for blocking PDGF-CC induced PDGFRα signalling in vivo

PDGF-CC is a member of the platelet-derived growth factor (PDGF) family that stimulates PDGFRα phosphorylation and thereby activates intracellular signalling events essential for development but also in cancer, fibrosis and neuropathologies involving blood-brain barrier (BBB) disruption. In order to elucidate the biological and pathological role(s) of PDGF-CC signalling, we have generated high affinity neutralizing monoclonal antibodies (mAbs) recognizing human PDGF-CC. We determined the complementarity determining regions (CDRs) of the selected clones, and mapped the binding epitope for clone 6B3. Using the monoclonal 6B3, we determined the expression pattern for PDGF-CC in different human primary tumours and control tissues, and explored its ability to neutralize PDGF-CC-induced phosphorylation of PDGFRα. In addition, we showed that PDGF-CC induced disruption of the blood-retinal barrier (BRB) was significantly reduced upon intraperitoneal administration of a chimeric anti-PDGF-CC antibody. In summary, we report on high affinity monoclonal antibodies against PDGF-CC that have therapeutic efficacy in vivo.

PDGF-CC underlies resistance to VEGF-A inhibition and combinatorial targeting of both suppresses pathological angiogenesis more efficiently

Anti-VEGF-A therapy has proven to be effective for many neovascular diseases. However, drug resistance to anti-VEGF-A treatment can develop. Also, not all patients with neovascular diseases are responsive to anti-VEGF-A treatment. The mechanisms underlying these important issues remain unclear. In this study, using different model systems, we found that inhibition of VEGF-A directly upregulated PDGF-CC and its receptors in multiple cell types in pathological angiogenesis in vitro and in vivo. Importantly, we further revealed that combinatorial targeting of VEGF-A and PDGF-CC suppressed pathological angiogenesis more efficiently than monotherapy. Given the potent angiogenic activity of PDGF-CC, our findings suggest that the development of resistance to anti-VEGF-A treatment may be caused by the compensatory upregulation of PDGF-CC, and combined inhibition of VEGF-A and PDGF-CC may have therapeutic advantages in treating neovascular diseases.

Microenvironmental control of breast cancer subtype elicited through paracrine platelet-derived growth factor-CC signaling

Breast tumors of the basal-like, hormone receptor-negative, subtype remain an unmet clinical challenge, as patients exhibit a high rate of recurrence and poor survival. Co-evolution of the malignant mammary epithelium and its underlying stroma instigates cancer-associated fibroblasts (CAFs) to endorse most, if not all, hallmarks of cancer progression. Here, we delineate a previously unappreciated role for CAFs as determinants of the molecular subtype of breast cancer. We identified a paracrine cross-talk between cancer cells expressing platelet-derived growth factor (PDGF)-CC and CAFs expressing the cognate receptors in human basal-like mammary carcinomas. Genetic or pharmacological intervention with PDGF-CC activity in mouse models of cancer resulted in conversion of basal-like breast cancers into a hormone receptor-positive state that conferred sensitivity to endocrine therapy in previously impervious tumors. We conclude that specification of the basal-like subtype of breast cancer is under microenvironmental control and therapeutically actionable in order to achieve sensitivity to endocrine therapy.

PDGF-C and PDGF-D signaling in vascular diseases and animal models

Members of the platelet-derived growth factor (PDGF) family are well known to be involved in different pathological conditions. The cellular and molecular mechanisms induced by the PDGF signaling have been well studied. Nevertheless, there is much more to discover about their functions and some important questions to be answered. This review summarizes the known roles of two of the PDGFs, PDGF-C and PDGF-D, in vascular diseases. There are clear implications for these growth factors in several vascular diseases, such as atherosclerosis and stroke. The PDGF receptors are broadly expressed in the cardiovascular system in cells such as fibroblasts, smooth muscle cells and pericytes. Altered expression of the receptors and the ligands have been found in various cardiovascular diseases and current studies have shown important implications of PDGF-C and PDGF-D signaling in fibrosis, neovascularization, atherosclerosis and restenosis.

Etv2-miR-130a-Jarid2 cascade regulates vascular patterning during embryogenesis

Remodeling of the primitive vasculature is necessary for the formation of a complex branched vascular architecture. However, the factors that modulate these processes are incompletely defined. Previously, we defined the role of microRNAs (miRNAs) in endothelial specification. In the present study, we further examined the Etv2-Cre mediated ablation of Dicer^L/L and characterized the perturbed vascular patterning in the embryo proper and yolk-sac. We mechanistically defined an important role for miR-130a, an Etv2 downstream target, in the mediation of vascular patterning and angiogenesis in vitro and in vivo. Inducible overexpression of miR-130a resulted in robust induction of vascular sprouts and angiogenesis with increased uptake of acetylated-LDL. Mechanistically, miR-130a directly regulated Jarid2 expression by binding to its 3’-UTR region. Over-expression of Jarid2 in HUVEC cells led to defective tube formation indicating its inhibitory role in angiogenesis. The knockout of miR-130a showed increased levels of Jarid2 in the ES/EB system. In addition, the levels of Jarid2 transcripts were increased in the Etv2-null embryos at E8.5. In the in vivo settings, injection of miR-130a specific morpholinos in zebrafish embryos resulted in perturbed vascular patterning with reduced levels of endothelial transcripts in the miR-130a morphants. Further, co-injection of miR-130a mimics in the miR-130a morphants rescued the vascular defects during embryogenesis. qPCR and in situ hybridization techniques demonstrated increased expression of jarid2a in the miR-130a morphants in vivo. These findings demonstrate a critical role for Etv2-miR-130a-Jarid2 in vascular patterning both in vitro and in vivo.

Use of multitarget tyrosine kinase inhibitors to attenuate platelet-derived growth factor signalling in lung disease

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) play a fundamental role in the embryonic development of the lung. Aberrant PDGF signalling has been documented convincingly in a large variety of pulmonary diseases, including idiopathic pulmonary arterial hypertension, lung cancer and lung fibrosis. Targeting PDGF signalling has been proven to be effective in these diseases. In clinical practice, the most effective way to block PDGF signalling is to inhibit the activity of the intracellular PDGFR kinases. Although the mechanism of action of such drugs is not specific for PDGF signalling, the medications have a broad therapeutic index that allows clinical use. The safety profile and therapeutic opportunities of these and future medications that target PDGFs and PDGFRs are reviewed.

An increasing role for PDGF signalling inhibitors in clinical trials for the treatment of various pulmonary diseaseshttp://ow.ly/buaI30f9HcN

Platelet-derived growth factor-C and -D in the cardiovascular system and diseases

The cardiovascular system is among the first organs formed during development and is pivotal for the formation and function of the rest of the organs and tissues. Therefore, the function and homeostasis of the cardiovascular system are finely regulated by many important molecules. Extensive studies have shown that platelet-derived growth factors (PDGFs) and their receptors are critical regulators of the cardiovascular system. Even though PDGF-C and PDGF-D are relatively new members of the PDGF family, their critical roles in the cardiovascular system as angiogenic and survival factors have been amply demonstrated. Understanding the functions of PDGF-C and PDGF-D and the signaling pathways involved may provide novel insights into both basic biomedical research and new therapeutic possibilities for the treatment of cardiovascular diseases.

A Review of Anti-Angiogenic Targets for Monoclonal Antibody Cancer Therapy

Tumor angiogenesis is a key event that governs tumor progression and metastasis. It is controlled by the complicated and coordinated actions of pro-angiogenic factors and their receptors that become upregulated during tumorigenesis. Over the past several decades, vascular endothelial growth factor (VEGF) signaling has been identified as a central axis in tumor angiogenesis. The remarkable advent of recombinant antibody technology has led to the development of bevacizumab, a humanized antibody that targets VEGF and is a leading clinical therapy to suppress tumor angiogenesis. However, despite the clinical efficacy of bevacizumab, its significant side effects and drug resistance have raised concerns necessitating the identification of novel drug targets and development of novel therapeutics to combat tumor angiogenesis. This review will highlight the role and relevance of VEGF and other potential therapeutic targets and their receptors in angiogenesis. Simultaneously, we will also cover the current status of monoclonal antibodies being developed to target these candidates for cancer therapy.

Platelet-derived growth factor-C promotes human melanoma aggressiveness through activation of neuropilin-1

Despite recent progress in advanced melanoma therapy, identification of signalling pathways involved in melanoma switch from proliferative to invasive states is still crucial to uncover new therapeutic targets for improving the outcome of metastatic disease. Neuropilin-1 (NRP-1), a co-receptor for vascular endothelial growth factor-A (VEGF-A) tyrosine kinase receptors (VEGFRs), has been suggested to play a relevant role in melanoma progression. NRP-1 can be activated by VEGF-A also in the absence of VEGFRs, triggering specific signal transduction pathways (e.g. p130Cas phosphorylation). Since melanoma cells co-expressing high levels of NRP-1 and platelet derived growth factor-C (PDGF-C) show a highly invasive behaviour and PDGF-C shares homology with VEGF-A, in this study we have investigated whether PDGF-C directly interacts with NRP-1 and promotes melanoma aggressiveness. Results demonstrate that PDGF-C specifically binds in vitro to NRP-1. In melanoma cells expressing NRP-1 but lacking PDGFRα, PDGF-C stimulates extra-cellular matrix (ECM) invasion and induces p130Cas phosphorylation. Blockade of PDGF-C function by neutralizing antibodies or reduction of its secretion by specific siRNA inhibit ECM invasion and vasculogenic mimicry. Moreover, PDGF-C silencing significantly down-modulates the expression of Snail, a transcription factor involved in tumour invasiveness that is highly expressed in NRP-1 positive melanoma cells. In conclusion, our results demonstrate for the first time a direct activation of NRP-1 by PDGF-C and strongly suggest that autocrine and/or paracrine stimulation of NRP-1 by PDGF-C might contribute to the acquisition of a metastatic phenotype by melanoma cells.

Cancer of the Peripheral Nerve in Neurofibromatosis Type 1

The RASopathy neurofibromatosis 1 is an autosomal dominant hereditary cancer syndrome that represents a major risk for the development of malignancies, particularly malignant peripheral nerve sheath tumors (MPNSTs). MPNSTs are unique sarcomas that originate from the peripheral nerve and represent the only primary cancer of the peripheral nervous system. To date, surgery is the only treatment modality proven to have survival benefit for MPNSTs and even when maximal surgery is feasible, these tumors are rarely curable, despite the use of chemotherapy and radiation. In this review, we discuss the current state-of-the-art treatments for MPNSTs, latest therapeutic developments, and critical aspects of the underlying molecular and pathophysiology that appear promising for therapeutic developments in the future. In particular, we discuss the specific elements of cancer in the peripheral nerve and how that may impel development of unique therapies for this form of sarcoma.

The Role of PDGFs and PDGFRs in Colorectal Cancer

Introduction. Colorectal cancer (CRC) is an important cause of morbidity and mortality worldwide. Angiogenesis was reported as one important mechanism activated in colorectal carcinogenesis. Tumor microenvironment associated angiogenesis involves a large spectrum of signaling molecules and deciphering their role in colorectal carcinogenesis still represents a major challenge. The aim of our study is to point out the diagnosis and prediction role of PDGF family and their receptors in colorectal carcinogenesis. Material and Methods. A systematic search in Medline and PubMed for studies reporting the role of platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) in tumor biology related to CRC was made. Results. PDGFs are important growth factors for normal tissue growth and division, with an important role in blood vessel formation. PDGFs/PDGFRs signaling pathway has been demonstrated to be involved in angiogenesis mainly by targeting pericytes and vascular smooth muscle cells. High levels of PDGF-BB were reported in CRC patients compared to those with adenomas, while elevated levels of PDGFR α/β in the stroma of CRC patients were correlated with invasion and metastasis. Moreover, PDGF-AB and PDGF-C were correlated with early diagnosis, cancer grading, and metastatic disease. Conclusions. Both PDGFs and PDGFRs families play an important role in colorectal carcinogenesis and could be considered to be investigated as useful biomarkers both for diagnosis and treatment of CRC.