GRK2 and breast neoplasm: An active GRK2/HuR/ HIF-1α module, particularly in estrogen-positive luminal A breast tumors could facilitate survival of malignant cells, even before the expanding tumor mass becomes hypoxic, and also improves the adaptation of tumor cells to the hypoxic environment of lymphatic vessels and to other tumor-related stresses, such as chronic over-activation of the adrenergic system, in order to foster tumor progression.