Complementary actions of dopamine D2 receptor agonist and anti‐vegf therapy on tumoral vessel normalization in a transgenic mouse model

Angiogenesis contributes in multiple ways to disease progression in tumors and reduces treatment efficiency. Molecular therapies targeting Vegf signaling combined with chemotherapy or other drugs exhibit promising results to improve efficacy of treatment. Dopamine has been recently proposed to be a novel safe anti‐angiogenic drug that stabilizes abnormal blood vessels and increases therapeutic efficacy. Here, we aimed to identify a treatment to normalize tumoral vessels and restore normal blood perfusion in tumor tissue with a Vegf receptor inhibitor and/or a ligand of dopamine G protein‐coupled receptor D2 (D2R). Dopamine, via its action on D2R, is an endogenous effector of the pituitary gland, and we took advantage of this system to address this question. We have used a previously described Hmga2/T mouse model developing haemorrhagic prolactin‐secreting adenomas. In mutant mice, blood vessels are profoundly altered in tumors, and an aberrant arterial vascularization develops leading to the loss of dopamine supply. D2R agonist treatment blocks tumor growth, induces regression of the aberrant blood supply and normalizes blood vessels. A chronic treatment is able to restore the altered balance between pro‐ and anti‐angiogenic factors. Remarkably, an acute treatment induces an upregulation of the stabilizing factor Angiopoietin 1. An anti‐Vegf therapy is also effective to restrain tumor growth and improves vascular remodeling. Importantly, only the combination treatment suppresses intratumoral hemorrhage and restores blood vessel perfusion, suggesting that it might represent an attractive therapy targeting tumor vasculature. Similar strategies targeting other ligands of GPCRs involved in angiogenesis may identify novel therapeutic opportunities for cancer. What's new? Angiogenesis involving abnormal blood vessel growth is a central feature of cancer that ultimately undermines the effectiveness of treatment. A little explored avenue to overcoming pathogenic angiogenesis entails the normalization of blood supply via enhanced dopamine activity, a known inhibitor of vascular endothelial growth factor (Vegf) signaling. In this study, mice with hemorrhagic prolactin‐secreting adenomas were treated with the dopamine receptor agonist bromocriptine, alone or in combination with axitinib, a Vegf receptor inhibitor. Bromocriptine was found to successfully block aberrant growth of blood vessels and tumors. Given together, bromocriptine and axitinib restored blood vessel