HIF1A and colonic neoplasm: Further molecular investigations reveal that colon cancer cells release exosomal miR-21-5p, which suppresses the expression of Von Hippel-Lindau tumor suppressor (VHL), prevents the degradation of hypoxia inducible factor 1 subunit alpha (HIF-1α) and correspondingly, increases the transcription of NGF in Schwann cells as well as the secretion of NGF from Schwann cells.