NGFR and neoplasm: Possible mechanisms that play role in resistance to dopamine agonists include decreased expression of dopamine receptors in tumor cells, changes in other receptors that modulate dopamine receptors (e.g., nerve growth factor receptor), changes in downstream cascades (e.g., in subunit of the G-protein), an increase in angiogenesis markers, and an increase in fibrosis due to disturbances in the transforming growth factor β1 pathway [4].