Furthermore, many soluble factors of neurotrophic or axon-guiding nature such as NGF [147,160], brain-derived neurotrophic factor (BDNF) [147,161], neurotrophin 3 (NT-3) [147,162], glial-cell-derived neurotrophic factor (GDNF) [163], neurturin [164], artemin [165,166], sonic hedgehog [167,168], SEMA3D [169], and others are overexpressed by pancreatic tumour cells. Here, GDNF is linked to pancreatic neoplasm.