In view of GRK2 upregulation in luminal breast cancer cell lines, in spontaneous tumors in mice, and in some patients with invasive ductal carcinoma (61), confirming the expression levels of GRK2 in perivascular cells and ECs will contribute to clarifying the mechanism by which GRK2 regulates angiogenesis in different types of breast cancer. Here, GRK2 is linked to breast cancer.