Developmental and tumoral vascularization is regulated by G protein–coupled receptor kinase 2
Verónica Rivas, … , Federico Mayor Jr., Petronila Penela
Verónica Rivas, … , Federico Mayor Jr., Petronila Penela
Published October 25, 2013
Citation Information: J Clin Invest. 2013;123(11):4714-4730. https://doi.org/10.1172/JCI67333.
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Research Article Oncology

Developmental and tumoral vascularization is regulated by G protein–coupled receptor kinase 2

Abstract

Tumor vessel dysfunction is a pivotal event in cancer progression. Using an in vivo neovascularization model, we identified G protein–coupled receptor kinase 2 (GRK2) as a key angiogenesis regulator. An impaired angiogenic response involving immature vessels was observed in mice hemizygous for Grk2 or in animals with endothelium-specific Grk2 silencing. ECs isolated from these animals displayed intrinsic alterations in migration, TGF-β signaling, and formation of tubular networks. Remarkably, an altered pattern of vessel growth and maturation was detected in postnatal retinas from endothelium-specific Grk2 knockout animals. Mouse embryos with systemic or endothelium-selective Grk2 ablation had marked vascular malformations involving impaired recruitment of mural cells. Moreover, decreased endothelial Grk2 dosage accelerated tumor growth in mice, along with reduced pericyte vessel coverage and enhanced macrophage infiltration, and this transformed environment promoted decreased GRK2 in ECs and human breast cancer vessels. Our study suggests that GRK2 downregulation is a relevant event in the tumoral angiogenic switch.

Authors

Verónica Rivas, Rita Carmona, Ramón Muñoz-Chápuli, Marta Mendiola, Laura Nogués, Clara Reglero, María Miguel-Martín, Ramón García-Escudero, Gerald W. Dorn II, David Hardisson, Federico Mayor Jr., Petronila Penela

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Figure 6

Specific downregulation of endothelial GRK2 expression causes vascular malformations during embryonic development and at adulthood.

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Specific downregulation of endothelial GRK2 expression causes vascular m...
(A–D) Endothelial-specific ablation of GRK2 leads to a delayed formation of the aortic media. GRK2 immunoreactivity is reduced in endothelium of E11.5 embryos (arrows in D), while GRK2 staining of nervous ganglia adjacent to the aorta is unaffected. The aortic endothelium shows defective covering of SMA-positive cells (arrows in B) in mutant animals. (E–I) Vascular defects in E10.5 embryos upon specific ablation of endothelial GRK2. Angiogenesis of the hindbrain is delayed in Tie2Cre-Grk2fl/fl embryos. PECAM1-positive vessels can be seen within the neuroectoderm of control embryos (arrowhead in E), but they are scarce or absent in Tie2Cre-Grk2fl/fl embryos (arrows in E–I indicate representative vessels). Vessels of the perineural plexus (arrows in E) and of the limb bud (arrows in H) are dilated in the mutant embryo as compared with the WT (F and G, respectively). The paired aorta from this Tie2Cre-Grk2fl/fl embryo also shows a reduced left branch (arrow in I), similar to that of the systemic mutant (see Supplemental Figure 5). (J–S) Adult mice with endothelial-specific ablation of GRK2 show disorganization and dilatation of small vessels and capillaries in the liver (arrows in O and P). GRK2 staining is strongly reduced in the cardiac endocardium (compare to arrows in J and N) and coronary endothelium of Tie2Cre-Grk2fl/fl mice. Extravascular blood accumulations without PECAM1-positive endothelium covering (arrows in Q) and lacking SMA and laminin immunoreactivity (arrows in R and S) suggests microhemorrhages. A normal coronary vessel is shown (arrowhead in R). Scale bar: 25 μm (C–F); 50 μm (A, B, G–I, K, L, O, and P); 100 μm (J, M, N, and Q–S).