ADRB2 and neoplasm: Therefore, as both ADRA2A and ADRB2 receptors are co-expressed in MG-63 cells, and ADRA2A is associated to antiproliferative signaling upon stimulation in malignant cells, ADRB2 blockade by PPN and ADRA2A activation by present catecholamines could collaborate into a greater tumor cell growth inhibition of MG-63 cells.