NTRK1 and breast carcinoma: MCF-7, T47-D, BT-20, and MDA-MB-231 breast carcinoma cells secrete NGF and express NGFR; when NGF combines with TrkA, an intracellular signal is sent via p21ras by phosphorylation and the ras-MAPK signal pathway is stimulated to influence gene transcription, translation and mediate cell growth [23,24].