BET Bromodomain Suppression Inhibits VEGF-induced Angiogenesis and Vascular Permeability by Blocking VEGFR2-mediated Activation of PAK1 and eNOS

Abstract

The tyrosine kinase receptor vascular endothelial growth factor receptor 2 (VEGFR2) is a critical modulator of angiogenesis. Increasing evidence indicate the important role of bromodomain and extra-terminal domain (BET) of chromatin adaptors in regulating tumor growth and inflammatory response. However, whether BET proteins have a role in angiogenesis and endothelial permeability is unclear. In this study, we observed that treatment with JQ1, a specific BET inhibitor, suppressed in vitro tube formation of human umbilical vein endothelial cells (HUVECs) and in vivo angiogenesis in a Matrigel plug and oxygen-induced retinopathy neovascularization. JQ1 attenuated the VEGF-induced decrease in TEER in HUVECs and prevented Evans blue dye leakage in the VEGF-induced Miles assay in athymic Balb/c nude mice. BET inhibition with JQ1 or shRNA for Brd2 or Brd4 suppressed VEGF-induced migration, proliferation, and stress fiber formation of HUVECs. Furthermore, BET inhibition suppressed phosphorylation of VEGFR2 and PAK1, as well as eNOS activation in VEGF-stimulated HUVECs. Inhibition with VEGFR2 and PAK1 also reduced migration and proliferation, and attenuated the VEGF-induced decrease in TEER. Thus, our observations suggest the important role of BET bromodomain in regulating VEGF-induced angiogenesis. Strategies that target the BET bromodomain may provide a new therapeutic approach for angiogenesis-related diseases.

Autocrine VEGF and IL-8 Promote Migration via Src/Vav2/Rac1/PAK1 Signaling in Human Umbilical Vein Endothelial Cells

“…Previous reports have shown that P21-activated kinase 1 (PAK1), a main downstream effector of Rac1, is involved in regulating endothelial migration and angiogensis [33, 34]. Therefore, we examined whether PAK1 activation also occurred in our system.…”

“…It has been reported that PAK1 activity was required for endothelial cell migration and permeability, and PAK1 inhibition by autoinhibitory domain of PAK1 also suppressed angiogenesis [33, 34]. In addition, Src has been identified as a potent modulator of extracellular signal-regulated PAK1 activity [35].…”

“…In addition, Src has been identified as a potent modulator of extracellular signal-regulated PAK1 activity [35]. Recent studies have suggested that PAK1 can be activated by growth factors and cytokines such as VEGF and IL-8 [34]. Thus, it is worthwhile to explore whether the PAK1 signaling pathway is involved in autocrine VEGF and IL-8-induced endothelial cell migration.…”

Bromodomains in Protozoan Parasites: Evolution, Function, and Opportunities for Drug Development

“…JQ1 has been applied to other human diseases, including liver cancer, inflammatory responses, and angiogenesis-related disease (29)(30)(31). Another BET family inhibitor, I-BET151, was shown to disrupt expression of genes activated in the inflammatory response to bacterial liposaccharide (LPS).…”

Bromodomain and Extra-terminal (BET) Protein Inhibitors Suppress Chondrocyte Differentiation and Restrain Bone Growth

“…Pharmacological inhibition of BET proteins lowers the expression of key transcription factors such as oncogene c-MYC (8), clamps the transductions of PI3K signaling (9), inhibits Gli1 transcription and Hedgehog pathway (10), blocks transcription in neurons (11), represses VEGF-induced angiogenesis and vascular permeability (12), reduces cell viability of osteosarcoma cells and inhibits osteoblastic differentiation (13), and restrains osteoclastogenesis (14). Meanwhile, potent BET inhibitors have been identified as showing antitumor efficacy in a number of preclinical cancer models in recent years, including leukemia, multiple myeloma, lymphoma, melanoma, and gastric cancer (15,16).…”