GRK2 and medullary thyroid gland carcinoma: While overexpressed on the protein level in primary non-medullary thyroid cancer tissue as compared to adjacent normal tissue, recombinant overexpression of ADRBK1 in two poorly differentiated thyroid cell lines has been reported to result in significantly decreased proliferation of the cells, suggesting an anti-proliferative role of ADRBK1 in these cells [47].