GEP100-Arf6-AMAP1-Cortactin Pathway Frequently Used in Cancer Invasion Is Activated by VEGFR2 to Promote Angiogenesis

Abstract

Angiogenesis and cancer invasiveness greatly contribute to cancer malignancy.Arf6 and its effector, AMAP1, are frequently overexpressed in breast cancer, and constitute a central pathway to induce the invasion and metastasis. In this pathway, Arf6 is activated by EGFR via GEP100. Arf6 is highly expressed also in human umbilical vein endothelial cells (HUVECs) and is implicated in angiogenesis. Here, we found that HUVECs also highly express AMAP1, and that vascular endothelial growth factor receptor-2 (VEGFR2) recruits GEP100 to activate Arf6. AMAP1 functions by binding to cortactin in cancer invasion and metastasis. We demonstrate that the same GEP100-Arf6-AMAP1-cortactin pathway is essential for angiogenesis activities, including cell migration and tubular formation, as well as for the enhancement of cell permeability and VE-cadherin endocytosis of VEGF-stimulated HUVECs. Components of this pathway are highly expressed in pathologic angiogenesis, and blocking of this pathway effectively inhibits VEGF- or tumor-induced angiogenesis and choroidal neovascularization. The GEP100-Arf6-AMAP1-cortactin pathway, activated by receptor tyrosine kinases, appears to be common in angiogenesis and cancer invasion and metastasis, and provides their new therapeutic targets.

Arf6 regulates tumour angiogenesis and growth through HGF-induced endothelial β1 integrin recycling

“…These observations led us to speculate that Arf6 might be involved in HGF-stimulated tumour angiogenesis. In support of this proposal, Arf6 has recently been shown to be involved in angiogenesis-related cell functions in vitro [23][24][25][26] . However, the in vivo functions of Arf6 in endothelial cells, in particular in relationship to HGF-regulated tumour angiogenesis and growth, have not been explored.…”

“…Hashimoto et al 26 have shown that knockdown of Arf6 in HUVECs increases their vascular permeability, which is generally controlled by vesicular trafficking of vascular endothelial-cadherin induced by VEGF stimulation. More recently, it has been demonstrated that interleukin 1b regulates endothelial cell permeability through Arf6 activation to allow inflammatory cells to be recruited to inflammatory sites 43 .…”

Brag2 differentially regulates β1- and β3-integrin-dependent adhesion in endothelial cells and is involved in developmental and pathological angiogenesis

“…Several stimuli, such as integrin binding to fibronectin, as well as stimulation with growth factors, cytokines and guidance molecules may induce the activation of Arf6 in EC [18,20,27,44]. Arf6 can be activated by several guanine exchange nucleotide factors (GEFs) [7].…”

“…Arf6 can be activated by several guanine exchange nucleotide factors (GEFs) [7]. Brag2 (GEP100/IQSEC1) is a GEF activating the small ArfGTPases Arf4, Arf5 and Arf6 [33,48] and is expressed in EC [20,45]. Brag2 was found to promote the invasive activity of breast cancer cells [34] and myoblast fusion [11,37].…”

“…However, the role of Brag2 in the regulation of integrins in EC was not studied thus far. In EC VEGF stimulation induces the association of VEGFR2 with Brag2 and induces the activation of Arf6 [20]. Interestingly, Semaphorin 3E-induced over-activation of the Brag2/Arf6 pathway results in collapse of EC and angiogenesis inhibition [45].…”