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 7

Endothelial GRK2 levels influence tumor growth by altering pericyte recruitment and tumor microvasculature.

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Endothelial GRK2 levels influence tumor growth by altering pericyte recr...
(A) Tumors implanted in mice with reduced endothelial expression of GRK2 exhibit higher growth rates. B16F10 melanoma cells were subcutaneously injected in mice and tumor size was monitored as described in Methods (n = 3–4 animals for each condition in 3 independent experiments). P values indicated in comparisons between WT and hemizygous mice and between hemizygous and Tie2Cre-Grk2fl/– mice. (B and C) Higher occurrence of large and dilated vessels in tumors grown in Tie2Cre-Grk2fl/– mice. Tumor sections were stained with the endothelial biotinylated ILB4 marker and hematoxylin counterstained. Vessel size was calculated as detailed in Methods. Distribution of vessel diameter in each condition is shown in C. (D and E) Reduced pericyte recruitment in tumors implanted in Tie2Cre-Grk2fl/– mice. Sections of tumors were (D) stained with biotinylated ILB4 and anti-SMA antibodies or (E) double stained with fluorescein-ILB4 and anti-SMA antibodies to quantify the mural coverage as described in Methods. Data were expressed as a percentage of the total ILB4-positive area. (F) Tumors grown in Tie2Cre-Grk2fl/– mice show increased macrophage density compared to those implanted in WT mice. The number of F4/80-positive cells in different sections covering the whole tumor mass is shown. Two distinct specimens were analyzed for each condition. Scale bar: 100 μm.