SMPD2 and neoplasm: In murine models of human papillomavirus-induced head and neck cancer, tumor innervation is attenuated by inhibiting exosome release using Rab27A/B-deficient mEERL cells (Rab27A−/+ Rab27B−/−) or pharmacological blockade of mature exosome release by neutral sphingomyelinase inhibitor (GW4869).186 In addition, exosomes from colorectal cancer (CT26), melanoma (B16), and breast cancer (4T1) cells induce neurite outgrowth (PC12, rat pheochromocytoma cell line).186 Tumor-derived exosomes promote sensory innervation observed in human cervical cancer (TRPV1+ sensory nerves).