ARTN and cancer: PNI is a complex phenomenon that involves multidirectional communication of cells, including fibroblasts, pancreatic stellate cells, immune cells and Schwann cells, and molecules and pathways, including neurotrophic factors, neurotrophin receptors, chemokines, axonal guidance molecules, cellular adhesion molecules, matrix metalloproteinases and neurotransmitters between nerves and the cancer microenvironment [24].