Patients with densely innervated tumors suffer with increased metastasis and decreased survival as compared to those with less innervated tumors. Scientists at Sanford Research hypothesized that in some tumors, nerves are acquired by a tumor-induced process, called axonogenesis. They used PC12 cells as an in vitro neuronal model, human tumor samples and murine in vivo models to test this hypothesis. When appropriately stimulated, PC12 cells extend processes, called neurites. The scientists show that patient tumors release vesicles, called exosomes, which induce PC12 neurite outgrowth. Using a cancer mouse model, they show that tumors compromised in exosome release are less innervated than controls. Moreover, in vivo pharmacological blockade of exosome release similarly attenuates tumor innervation. They characterize these nerves as sensory in nature and demonstrate that axonogenesis is potentiated by the exosome-packaged axonal guidance molecule, EphrinB1. These findings indicate that tumor released exosomes induce tumor innervation and exosomes containing EphrinB1 potentiate this activity.
Validation of human exosome purification
a Scanning electron micrograph of exosomes purified from human plasma. Scale bar, 200 nm. n = 4 biological samples. b Atomic force microscopy amplitude trace of exosomes purified from human plasma. Size range, 63–105 nm. Scale bar, 500 nm. n = 7 biological samples. c Representative nanoparticle tracking analysis of exosomes purified from human plasma. N = 4 biological samples. d Western blot analysis of control (Cntl) and patient (Pt) exosomes (exos). Western blots have been cropped for clarity and conciseness. Nl1-2 plasma from healthy volunteers, TL 1 normal adult tonsil. n = 3 technical replicates