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The somite-secreted factor Maeg promotes zebrafish embryonic angiogenesis.

ABSTRACT: MAM and EGF containing gene (MAEG), also called Epidermal Growth Factor-like domain multiple 6 (EGFL6), belongs to the epidermal growth factor repeat superfamily. The role of Maeg in zebrafish angiogenesis remains unclear. It was demonstrated that maeg was dynamically expressed in zebrafish developing somite during a time window encompassing many key steps in embryonic angiogenesis. Maeg loss-of-function embryos showed reduced endothelial cell number and filopodia extensions of intersegmental vessels (ISVs). Maeg gain-of-function induced ectopic sprouting evolving into a hyperbranched and functional perfused vasculature. Mechanistically we demonstrate that Maeg promotes angiogenesis dependent on RGD domain and stimulates activation of Akt and Erk signaling in vivo. Loss of Maeg or Itgb1, augmented expression of Notch receptors, and inhibiting Notch signaling or Dll4 partially rescued angiogenic phenotypes suggesting that Notch acts downstream of Itgb1. We conclude that Maeg acts as a positive regulator of angiogenic cell behavior and formation of functional vessels.

SUBMITTER: Wang X

PROVIDER: S-EPMC5363618 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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The somite-secreted factor Maeg promotes zebrafish embryonic angiogenesis.

Wang Xin X Yuan Wei W Wang Xueqian X Qi Jialing J Qin Yinyin Y Shi Yunwei Y Zhang Jie J Gong Jie J Dong Zhangji Z Liu Xiaoyu X Sun Chen C Chai Renjie R Le Noble Ferdinand F Liu Dong D

Oncotarget 20161101 47

MAM and EGF containing gene (MAEG), also called Epidermal Growth Factor-like domain multiple 6 (EGFL6), belongs to the epidermal growth factor repeat superfamily. The role of Maeg in zebrafish angiogenesis remains unclear. It was demonstrated that maeg was dynamically expressed in zebrafish developing somite during a time window encompassing many key steps in embryonic angiogenesis. Maeg loss-of-function embryos showed reduced endothelial cell number and filopodia extensions of intersegmental ve ...[more]

PMID: 27780917

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Project description:Background: By providing oxygen, nutrients and metastatic conduits, tumour angiogenesis is essential for cancer metastasis. Cancer cell-secreted microRNAs can be packaged into exosomes and are implicated in different aspects of tumour angiogenesis. However, the underlying mechanisms are incompletely understood. Methods: The GEPIA database and in situ hybridization assay were used to analyse expression of miR-205 in ovarian tissues. Immunohistochemistry was performed to examine the relationship between miR-205 and microvessel density. Expression of circulating miR-205 was evaluated by RT-PCR and GEO database analysis. Co-culture and exosome labelling experiments were performed to assess exosomal miR-205 transfer from ovarian cancer (OC) cells to endothelial cells ECs. Exosome uptake assays were employed to define the cellular pathways associated with the endocytic uptake of exosomal miR-205. The role of exosomal miR-205 in angiogenesis was further investigated in vivo and in vitro. Western blotting and rescue experiments were applied to detect regulation of the PTEN-AKT pathway by exosomal miR-205 in ECs. Results: miR-205 was up-regulated in OC tissues, and high expression of miR-205 was associated with metastatic progression in OC patients. Moreover, miR-205 was highly enriched in cancer-adjacent ECs, and up-regulation of miR-205 correlated positively with high microvessel density in OC patients. Importantly, miR-205 was markedly enriched in the serum of OC patients, and a high level of miR-205 in circulating exosomes was associated with OC metastasis. In addition, OC-derived miR-205 was secreted into the extracellular space and efficiently transferred to adjacent ECs in an exosome-dependent manner, and the lipid raft-associated pathway plays an important role in regulating uptake of exosomal miR-205. Exosomal miR-205 from OC cells significantly promoted in vitro angiogenesis and accelerated angiogenesis and tumour growth in a mouse model. Furthermore, we found that exosomal miR-205 induces angiogenesis via the PTEN-AKT pathway. Conclusion: These findings demonstrate an exosome-dependent mechanism by which miR-205 derived from cancer cells regulates tumour angiogenesis and implicate exosomal miR-205 as a potential therapeutic target for OC.

Project description:Angiogenesis is a fundamental process that involves in tumor progression and metastasis. Vascular endothelial growth factor (VEGF) family and their receptors are identified as the most prominent regulators of angiogenesis. However, the clinical efficacy of anti-VEGF/VEGFR therapy is not ideal, prompting the needs to further understand mechanisms behind tumor angiogenesis. Here, we found that Dickkopf associated protein 2 (DKK2), a secretory protein highly expressed in metastatic colorectal cancer tissues, could stimulate angiogenesis via a classic VEGF/VEGFR independent pathway. Methods: DKK2 was screened out from microarray data analyzing gene expression profiles of eight pairs of non-metastatic and metastatic human colorectal cancer (CRC) tissues. Immunofluorescence histochemical staining (IHC) was used to detect the expression of DKK2 and angiogenesis in CRC tissues. Chicken chorioallantoic membrane (CAM) assay and Human umbilical vein endothelial cells (HUVEC) tubule formation assay was used for in vitro and in vivo angiogenesis study, respectively. Lactate and glucose concentration in the culture medium was measured by enzyme-linked immunosorbent assay (ELISA). Luciferase reporter assay was used to verify the interaction between miR-493-5p and the 3'UTR of DKK2. Results: DKK2 could stimulate angiogenesis via accelerating the aerobic glycolysis of CRC cells, through which lactate is produced from glucose and accumulated in tumor microenvironment. Lactate functions as the final executor of DDK2 to stimulate tube formation of endothelial cells, and blockage of lactate secretion by lactate transporter (MCT) inhibitors dramatically neutralize the progression and metastasis of CRC both in vitro and in vivo. DKK2 could cooperate with lipoprotein receptor-related protein 6, which is required for glucose uptake, and activated the downstream mTOR signal pathway to accelerate lactate secretion. In addition, the expression of DKK2 is switched on via the demethylation of miR-493-5p, which allows the dissociated of miR-493-5p from the 3'-UTRs of DKK2 and initiates its stimulatory role on CRC progression in an autocrine or paracrine manner. Conclusion: DKK2 promotes tumor metastasis and angiogenesis through a novel VEGF-independent, but energy metabolism related pathway. DKK2 might be a potential anti-angiogenic target in clinical treatment for the advanced CRC patients.

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The somite-secreted factor Maeg promotes zebrafish embryonic angiogenesis.

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The somite-secreted factor Maeg promotes zebrafish embryonic angiogenesis.

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