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 9

Tumor-derived factors reduce the expression of GRK2 in the endothelium of tumor microvasculature.

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Tumor-derived factors reduce the expression of GRK2 in the endothelium o...
(A) GRK2 downregulation in MLECs exposed to factors secreted by tumoral but not by nontransformed cell lines. WT or GRK2+/– derived MLECs were cocultured with the different malignant or normal mammary (184B5) cell lines as described in Methods (n = 3–4 independent experiments). (B–J) GRK2 expression is markedly decreased in tumor EC cells of breast cancer patients. Immunohistochemical staining of normal and different benign and malignant lesions of the mammary gland reveals that vessels from nontumoral tissues (B–G) show a noticeable signal for GRK2 at the endothelial layer, while tumoral vessels of breast carcinomas (H–J) display lower or even undetectable GRK2 levels. Normal vessels at the tumor margin retain GRK2 staining. Blood vessels were identified by the presence of blood cells and by anatomic features. Representative vessels are indicated with arrows. (B–D) Normal breast, (E) mild hyperplasia, (F) fibroadenoma, (G) adenosis, and (H–J) breast carcinomas samples were analyzed. T, tumoral area; NT, nontumoral area. (K) Relative vessel immunoreactivity was evaluated by two investigators in a blinded fashion and classified as strong, moderate, or faint/absent GRK2-expressing vessels. The percentage ratio of each vessel group to total vessels analyzed in each breast tissue condition was represented. The number of vessels analyzed was 73 in 7 cases of normal breast tissue, 139 in 14 cases of benign lesions, and 138 in 35 patients of breast carcinoma. P values compare normal cells or normal breast tissues. Scale bar: 20 μm.