PHD4 Stimulates Tumor Angiogenesis in Osteosarcoma Cells via TGF-α

Exploring the Impact of Exosomal Cargos on Osteosarcoma Progression: Insights into Therapeutic Potential

Osteosarcoma (OS) is a primary malignant bone tumor with high metastasis. Poor prognosis highlights a clinical need for novel therapeutic strategies. Exosomes, also known as extracellular vesicles, have been identified as essential players in the modulation of cancer. Recent studies have suggested that OS-derived exosomes can drive pro-tumorigenic or anti-tumorigenic phenotypes by transferring specific cargos, including proteins, nucleic acids, and metabolites, to neighboring cells, significantly impacting the regulation of cellular processes. This review discusses the advancement of exosomes and their cargos in OS. We examine how these exosomes contribute to the modulation of cellular phenotypes associated with tumor progression and metastasis. Furthermore, we explore the potential of exosomes as valuable biomarkers for diagnostics and prognostic purposes and their role in shaping innovative therapeutic strategies in OS treatment development.

Functional role of MicroRNA/PI3K/AKT axis in osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor that occurs in children and adolescents, and the PI3K/AKT pathway is overactivated in most OS patients. MicroRNAs (miRNAs) are highly conserved endogenous non-protein-coding RNAs that can regulate gene expression by repressing mRNA translation or degrading mRNA. MiRNAs are enriched in the PI3K/AKT pathway, and aberrant PI3K/AKT pathway activation is involved in the development of osteosarcoma. There is increasing evidence that miRNAs can regulate the biological functions of cells by regulating the PI3K/AKT pathway. MiRNA/PI3K/AKT axis can regulate the expression of osteosarcoma-related genes and then regulate cancer progression. MiRNA expression associated with PI3K/AKT pathway is also clearly associated with many clinical features. In addition, PI3K/AKT pathway-associated miRNAs are potential biomarkers for osteosarcoma diagnosis, treatment and prognostic assessment. This article reviews recent research advances on the role and clinical application of PI3K/AKT pathway and miRNA/PI3K/AKT axis in the development of osteosarcoma.

P4HTM: A Novel Downstream Target of GATA3 in Breast Cancer

Breast cancer continues to be a major cause of death among women. The GATA3 gene is often overexpressed in breast cancer and is widely used to support a diagnosis. However, lower expression of GATA3 has been linked to poorer prognosis along with frequent gene mutations. Therefore, the role of GATA3 in breast cancer appears to be context specific. This study aims to identify a new downstream target of GATA3 to better understand its regulatory network. Clinical data analysis identified the prolyl 4-hydroxylase transmembrane protein (P4HTM) as one of the most highly co-expressed genes with GATA3. Immunohistochemical staining of breast tumors confirms co-expression between GATA3 and P4HTM at the protein level. Similar to GATA3, P4HTM expression levels are linked to patient prognosis, with lower levels indicating poorer survival. Genomics data found that GATA3 binds to the P4HTM locus, and that ectopic expression of GATA3 in basal breast cancer cells increases the P4HTM transcript level. These results collectively suggest that P4HTM is a novel downstream target of GATA3 in breast cancer and is involved in tumor progression.

Doxycycline inhibits the progression of metastases in early-stage osteosarcoma by downregulating the expression of MMPs, VEGF and ezrin at primary sites

INTRODUCTION

Osteosarcoma (OS) is the most common primary osseous malignant tumour, with high propensity to metastasise in lungs. Pulmonary micro-metastases are present in up to 80% of patients at initial diagnosis and they are associated with significantly worse prognosis. Doxycycline (Dox) is a synthetic tetracycline that has been shown to have anti-cancer properties in vitro and in vivo, and inhibit angiogenesis - effects that may prove beneficial for several types of cancer. The aim of the present work was to study how Dox affects OS cell growth in vitro and in vivo and OS-driven pulmonary metastasis in vivo.

METHODS

In vitro, the effect of Dox was measured in MG-63 and 143B human OS cell viability, apoptosis, invasion and migration. In vivo, highly metastatic 143B cells were orthotopically implanted into the tibia of SCID mice. The tumour growth and pulmonary metastases between Dox treated and untreated, non-amputated and early amputated xenografts were examined.

RESULTS

In vitro, Dox decreased viability, inhibited invasion, migration, and induced the apoptosis of OS cells. In vivo, Dox significantly enhanced tumour necrosis at primary OS sites, similarly to its in vitro effect, and downregulated the expression of Ki67, MMP2, MMP9, VEGFA and ezrin. It also decreased circulating VEGFA and MMP9 protein levels, in line with the decreased metastatic burden in Dox-treated mice (non-amputated and early-amputated).

CONCLUSIONS

Reprofiling of Dox can prevent the evolvement of pulmonary micro-metastases to clinically detectable macro-metastases and suppress the lethal progress of OS by inhibiting the expression of MMPs, VEGFA and ezrin at primary sites.

Myeloid PHD2 deficiency accelerates neointima formation via Hif-1α

The key players of the hypoxic response are the hypoxia-inducible factors (Hif), whose α-subunits are tightly regulated by Prolyl-4-hydroxylases (PHD), predominantly by PHD2. Monocytes/Macrophages are involved in atherosclerosis but also restenosis and were found at hypoxic and sites of the lesion. Little is known about the role of the myeloid PHD2 in atherosclerosis and neointima formation. The study aimed to investigate the consequences of a myeloid deficiency of PHD2 in the process of neointima formation using an arterial denudation model. LysM-cre mice were crossed with PHD2^fl/fl, PHD2^fl/fl/Hif1α^fl/fl and PHD2^fl/fl/Hif2α^fl/fl to get myeloid specific knockout of PHD2 and the Hif-α subunits. Denudation of the femoral artery was performed and animals were fed a western type diet afterwards with analysis of neointima formation 5 and 35 days after denudation. Increased neointima formation in myeloid PHD2 knockouts was observed, which was blunted by double-knockout of PHD2 and Hif1α whereas double knockout of PHD2 and Hif-2α showed comparable lesions to the PHD2 knockouts. Macrophage infiltration was comparable to the neointima formation, suggesting a more inflammatory reaction, and was accompanied by increased intimal VEGF-A expression. Collagen-content inversely correlated to the extent of neointima formation suggesting a destabilization of the plaque. This effect might be triggered by macrophage polarization. Therefore, in vitro results showed a distinct expression pattern in differentially polarized macrophages with high expression of Hif-1α, VEGF and MMP-1 in proinflammatory M1 macrophages. In conclusion, the results show that myeloid Hif-1α is involved in neointima hyperplasia. Our in vivo and in vitro data reveal a central role for this transcription factor in driving plaque-vascularization accompanied by matrix-degradation leading to plaque destabilization.

Inactivation of mouse transmembrane prolyl 4-hydroxylase increases blood brain barrier permeability and ischemia-induced cerebral neuroinflammation

Hypoxia-inducible factor prolyl 4-hydroxylases (HIF-P4Hs) regulate the hypoxic induction of >300 genes required for survival and adaptation under oxygen deprivation. Inhibition of HIF-P4H-2 has been shown to be protective in focal cerebral ischemia rodent models, while that of HIF-P4H-1 has no effects and inactivation of HIF-P4H-3 has adverse effects. A transmembrane prolyl 4-hydroxylase (P4H-TM) is highly expressed in the brain and contributes to the regulation of HIF, but the outcome of its inhibition on stroke is yet unknown. To study this, we subjected WT and P4htm^−/− mice to permanent middle cerebral artery occlusion (pMCAO). Lack of P4H-TM had no effect on lesion size following pMCAO, but increased inflammatory microgliosis and neutrophil infiltration was observed in the P4htm^−/− cortex. Furthermore, both the permeability of blood brain barrier and ultrastructure of cerebral tight junctions were compromised in P4htm^−/− mice. At the molecular level, P4H-TM deficiency led to increased expression of proinflammatory genes and robust activation of protein kinases in the cortex, while expression of tight junction proteins and the neuroprotective growth factors erythropoietin and vascular endothelial growth factor was reduced. Our data provide the first evidence that P4H-TM inactivation has no protective effect on infarct size and increases inflammatory microgliosis and neutrophil infiltration in the cortex at early stage after pMCAO. When considering HIF-P4H inhibitors as potential therapeutics in stroke, the current data support that isoenzyme-selective inhibitors that do not target P4H-TM or HIF-P4H-3 would be preferred.

Characterization of tryptophan-containing dipeptides for anti-angiogenic effects

AIMS

In the pathogenesis of several diseases, neo-angiogenesis is increased (e.g. tumour growth). The peptide L-glutamyl-L-tryptophan (EW/IM862) has been claimed to exhibit inhibitory effects on tumour growth in vivo. However, the potential role of natural peptides with respect to anti-angiogenic properties is unsettled. The current study explores anti-angiogenic effects of the dipeptides WL, EW, IW and WE.

METHODS AND RESULTS

Using a bottom-up strategy, we first evaluated the effects of the peptides on VEGFR-2 signalling and quantified their effects in different angiogenesis assays. WL consistently had the strongest effects on phosphorylation of VEGFR-2 and downstream signalling. Therefore, this peptide was chosen in comparison with EW to further assess anti-angiogenic properties. However, sprout formation in three-dimensional (3D) fibrin gel bead assay was significantly inhibited by EW only. Furthermore, vessel sprouting in the mouse aortic ring assay was decreased by the presence of WL and EW compared to control. Results from a chorioallantoic membrane assay showed that under vascular endothelial growth factor (VEGF) stimulation WL and EW decreased the number of blood vessels versus control. These results were in line with those obtained in a matrigel plug assay. The VEGF-induced increase in the haemoglobin content was nearly abolished when treatment was combined with either WL or EW application. In the murine model of oxygen-induced retinopathy, WL exhibited a small albeit significant anti-angiogenic effect.

CONCLUSION

Comprehensive screening of WL suggests an anti-angiogenic effect, demonstrated in in vitro, ex vivo and in vivo models. Thus, WL is a dipeptide with potential anti-angiogenic effects and is worthy for further exploration.

Transmembrane Prolyl 4-Hydroxylase is a Novel Regulator of Calcium Signaling in Astrocytes

Prolyl 4-hydroxylases (P4Hs) have vital roles in regulating collagen synthesis and hypoxia response. A transmembrane P4H (P4H-TM) is a recently identified member of the family. Biallelic loss of function P4H-TM mutations cause a severe autosomal recessive intellectual disability syndrome in humans, but functions of P4H-TM are essentially unknown at cellular level. Our microarray data on P4h-tm ^-/- mouse cortexes where P4H-TM is abundantly expressed indicated expression changes in genes involved in calcium signaling and expression of several calcium sequestering ATPases was upregulated in P4h-tm ^-/- primary mouse astrocytes. Cytosolic and intraorganellar calcium imaging of P4h-tm ^-/- cells revealed that receptor-operated calcium entry (ROCE) and store-operated calcium entry (SOCE) and calcium re-uptake by mitochondria were compromised. HIF1, but not HIF2, was found to be a key mediator of the P4H-TM effect on calcium signaling. Furthermore, total internal reflection fluorescence (TIRF) imaging showed that calcium agonist-induced gliotransmission was attenuated in P4h-tm ^-/- astrocytes. This phenotype was accompanied by redistribution of mitochondria from distal processes to central parts of the cell body and decreased intracellular ATP content. Our data show that P4H-TM is a novel regulator of calcium dynamics and gliotransmission.

The prolyl hydroxylase inhibitor roxadustat: Paradigm in drug discovery and prospects for clinical application beyond anemia

Prolyl hydroxylase (PHD) inhibitors, such as roxadustat, can stabilize hypoxia-inducible factor (HIF)-2α and induce erythropoietin (EPO) production under normal conditions. Roxadustat was recently approved as a first-in-class orally active drug for the treatment of renal anemia. In addition, it has garnered growing therapeutic interest for use against various diseases, such as carcinoma, neurological diseases, ocular diseases, and tissue and organ injuries. In this review, we systemically review target validation, hit identification, and further key clinical trials of roxadustat. The prospective clinical applications of PHD inhibitors are then discussed based on this marketed drug.

Distinct Serum and Vitreous Inflammation-Related Factor Profiles in Patients with Proliferative Vitreoretinopathy

INTRODUCTION

Proliferative vitreoretinopathy (PVR), which is regulated by growth factors and cytokines, is the leading cause of failure in vitreoretinal surgery. In this study, we aimed to investigate the role of the human serum and vitreous inflammation-related factors in the development of proliferative vitreoretinopathy (PVR).

METHODS

Blood and vitreous samples were obtained from patients undergoing pars plana vitrectomy. Inflammation-related factors were detected using an immunology multiplex assay on a Luminex® xMAP® platform. Patients with PVR and rhegmatogenous retinal detachment (RRD) were compared with macular hole (MH) or epiretinal membrane (ERM) patients without any other ocular or systemic disease.

RESULTS

Thirty-six serum samples and 34 vitreous samples were obtained. Thirty-one different growth factors and cytokines were detected in serum samples. However, none of the circulating growth factors and cytokines were found to be different from the controls. Ten different growth factors and cytokines were measured in the vitreous samples. The concentration levels of PDGF-AA, TGF-α, VEGF, IL-6, IL-8, and TNFβ were found to have significantly increased in the vitreous of PVR patients.

CONCLUSION

Our study found that none of the circulating inflammation-related factors were changed in PVR or RRD patients, indicating the absence of a system inflammatory biomarkers to predict the development of proliferative vitreoretinopathy. As a supplement to previous research, the concentrations of PDGF-AA, TGF-α, VEGF, IL-6, IL-8, and TNFβ were significantly upregulated in the vitreous of PVR patients. These factors should be considered for preventing PVR.

Hematopoietic hypoxia-inducible factor 2α deficiency ameliorates pathological retinal neovascularization via modulation of endothelial cell apoptosis

A hallmark of proliferative retinopathies, such as retinopathy of prematurity (ROP), is a pathological neovascularization orchestrated by hypoxia and the resulting hypoxia-inducible factor (HIF)-dependent response. We studied the role of Hif2α in hematopoietic cells for pathological retina neovascularization in the murine model of ROP, the oxygen-induced retinopathy (OIR) model. Hematopoietic-specific deficiency of Hif2α ameliorated pathological neovascularization in the OIR model, which was accompanied by enhanced endothelial cell apoptosis. That latter finding was associated with up-regulation of the apoptosis-inducer FasL in Hif2α-deficient microglia. Consistently, pharmacological inhibition of the FasL reversed the reduced pathological neovascularization from hematopoietic-specific Hif2α deficiency. Our study found that the hematopoietic cell Hif2α contributes to pathological retina angiogenesis. Our findings not only provide novel insights regarding the complex interplay between immune cells and endothelial cells in hypoxia-driven retina neovascularization but also may have therapeutic implications for proliferative retinopathies.-Korovina, I., Neuwirth, A., Sprott, D., Weber, S., Sardar Pasha, S. P. B., Gercken, B., Breier, G., El-Armouche, A., Deussen, A., Karl, M. O., Wielockx, B., Chavakis, T., Klotzsche-von Ameln, A. Hematopoietic hypoxia-inducible factor 2α deficiency ameliorates pathological retinal neovascularization via modulation of endothelial cell apoptosis.

[Is Oxygen Deficiency Always Harmful?]

Is Oxygen Deficiency Always Harmful? Abstract. The role of the cardiovascular circulation is to supply tissue with oxygen and nutrients. Oxygen deficiency (hypoxia) is considered life-threatening, since cells die, either through apoptotic or necrotic processes. Tissue tries to counteract this by means of evolutionary signalling pathways, such as the nuclear hypoxia-inducible factor, which protects the tissue by promoting cell survival strategies and simultaneously intervening in angiogenesis, haematogenesis and metabolic processes. Recent findings indicate that these conserved signalling pathways can also function as therapeutic approaches in wound healing of bones and skin, as well as in the regeneration of tissues, e.g. in the liver, and in the hematopoietic system.

Endothelial-specific deficiency of Junctional Adhesion Molecule-C promotes vessel normalisation in proliferative retinopathy

In proliferative retinopathies, like proliferative diabetic retinopathy and retinopathy of prematurity (ROP), the hypoxia response is sustained by the failure of the retina to revascularise its ischaemic areas. Non-resolving retina ischaemia/hypoxia results in upregulation of pro-angiogenic factors and pathologic neovascularisation with ectopic, fragile neovessels. Promoting revascularisation of the retinal avascular area could interfere with this vicious cycle and lead to vessel normalisation. Here, we examined the function of endothelial junctional adhesion molecule-C (JAM-C) in the context of ROP. Endothelial-specific JAM-C-deficient (EC-JAM-C KO) mice and littermate JAM-C-proficient (EC-JAM-C WT) mice were subjected to the ROP model. An increase in total retinal vascularisation was found at p17 owing to endothelial JAM-C deficiency, which was the result of enhanced revascularisation and vessel normalisation, thereby leading to significantly reduced avascular area in EC-JAM-C KO mice. In contrast, pathologic neovessel formation was not affected by endothelial JAM-C deficiency. Consistent with improved vessel normalisation, tip cell formation at the interface between vascular and avascular area was higher in EC-JAM-C KO mice, as compared to their littermate controls. Consistently, JAM-C inactivation in endothelial cells resulted in increased spreading on fibronectin and enhanced sprouting in vitro in a manner dependent on β1-integrin and on the activation of the small GTPase RAP1. Together, endothelial deletion of JAM-C promoted endothelial cell sprouting, and consequently vessel normalisation and revascularisation of the hypoxic retina without altering pathologic neovascularisation. Thus, targeting endothelial JAM-C may provide a novel therapeutic strategy for promoting revascularisation and vessel normalisation in the treatment of proliferative retinopathies.

PI3K/Akt signaling mediated Hexokinase-2 expression inhibits cell apoptosis and promotes tumor growth in pediatric osteosarcoma

Accumulating evidence has shown that PI3K/Akt pathway is frequently hyperactivated in osteosarcoma (OS) and contributes to tumor initiation and progression. Altered phenotype of glucose metabolism is a key hallmark of cancer cells including OS. However, the relationship between PI3K/Akt pathway and glucose metabolism in OS remains largely unexplored. In this study, we showed that elevated Hexokinase-2 (HK2) expression, which catalyzes the first essential step of glucose metabolism by conversion of glucose into glucose-6-phosphate, was induced by activated PI3K/Akt signaling. Immunohistochemical analysis showed that HK2 was overexpressed in 83.3% (25/30) specimens detected and was closely correlated with Ki67, a cell proliferation index. Silencing of endogenous HK2 resulted in decreased aerobic glycolysis as demonstrated by reduced glucose consumption and lactate production. Inhibition of PI3K/Akt signaling also suppressed aerobic glycolysis and this effect can be reversed by reintroduction of HK2. Furthermore, knockdown of HK2 led to increased cell apoptosis and reduced ability of colony formation; meanwhile, these effects were blocked by 2-Deoxy-d-glucose (2-DG), a glycolysis inhibitor through its actions on hexokinase, indicating that HK2 functions in cell apoptosis and growth were mediated by altered aerobic glycolysis. Taken together, our study reveals a novel relationship between PI3K/Akt signaling and aerobic glycolysis and indicates that PI3K/Akt/HK2 might be potential therapeutic approaches for OS.

PI3K/Akt signaling in osteosarcoma

Osteosarcoma (OS) is the most common nonhematologic bone malignancy in children and adolescents. Despite the advances of adjuvant chemotherapy and significant improvement of survival, the prognosis remains generally poor. As such, the search for more effective anti-OS agents is urgent. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway is thought to be one of the most important oncogenic pathways in human cancer. An increasing body of evidence has shown that this pathway is frequently hyperactivated in OS and contributes to disease initiation and development, including tumorigenesis, proliferation, invasion, cell cycle progression, inhibition of apoptosis, angiogenesis, metastasis and chemoresistance. Inhibition of this pathway through small molecule compounds represents an attractive potential therapeutic approach for OS. The aim of this review is to summarize the roles of the PI3K/Akt pathway in the development and progression of OS, and to highlight the therapeutic potential of targeting this signaling pathway. Knowledge obtained from the application of these compounds will help in further understanding the pathogenesis of OS and designing subsequent treatment strategies.

Prolyl-4-hydroxylase 2 enhances hypoxia-induced glioblastoma cell death by regulating the gene expression of hypoxia-inducible factor-α

Oxygen deprivation (hypoxia) is a common feature of solid tumors in advanced stages. The primary cellular transcriptional responses to hypoxia are mainly mediated by the transcription factor hypoxia-inducible factor (HIF). HIF consists of an oxygen-labile α-subunit (HIF-1α, -2α) and a stable β-subunit (ARNT). Prolyl-4-hydroxylase 2 (PHD2) is known as an important mediator of the oxygen-dependent degradation of HIF-α subunits. As HIF-α subunits are not confirmed to be the only substrates of PHD2, it is unknown whether PHD2 regulates HIF-1α and HIF-2α by interacting with other intracellular molecules. In this study, we found that in the glioblastoma cells, PHD2 maintains the gene expression of HIF-1α in dependence of nuclear factor κB and suppresses the gene expression of HIF-2α through HIF-1α. The PHD2-mediated degradation of HIF-1α and HIF-2α seems less important. Furthermore, PHD2 enhances hypoxia-induced glioblastoma cell death by modulating the expression of the HIF target genes glucose transporter 1, vascular endothelial growth factor-A and Bcl-2 binding protein 3. Our findings show that PHD2 inhibits the adaptation of glioblastoma cells to hypoxia by regulating the HIF-α subunits in a non-canonical way. Modulation of PHD2 activity might be considered as a new way to inhibit glioblastoma progression.

From wavy hair to naked proteins: the role of transforming growth factor alpha in health and disease

Since its discovery in 1978 and cloning in 1984, transforming growth factor-alpha (TGF-α, TGFA) has been one of the most extensively studied EGF receptor (EGFR) ligands. In this review, we provide a historical perspective on TGFA-related studies, highlighting what we consider important advances related to its function in normal and disease states.