GDNF and cancer: Recent studies have revealed that cancer cells have an ability to actively migrate along nerves in a mechanism called neural tracking, which is supported by various molecules, including nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF), neural cell adhesion molecule, matrix metalloproteinases (MMPs), and chemokines, which are secreted by tumour cells and other non-tumour cells in the surrounding microenvironment [12].