Schwann cell‐derived exosomes promote lung cancer progression via miRNA‐21‐5p

Schwann cells (SCs), the primary glial cells of the peripheral nervous system, which have been identified in many solid tumors, play an important role in cancer development and progression by shaping the tumor immunoenvironment and supporting the development of metastases. Using different cellular, molecular, and genetic approaches with integrated bioinformatics analysis and functional assays, we revealed the role of human SC-derived exosomal miRNAs in lung cancer progression in vitro and in vivo. We found that exosomal miRNA-21 from SCs up-regulated the proliferation, motility, and invasiveness of human lung cancer cells in vitro, which requires functional Rab small GTPases Rab27A and Rab27B in SCs for exosome release. We also revealed that SC exosomal miRNA-21-5p regulated the functional activation of tumor cells by targeting metalloprotease inhibitor RECK in tumor cells. Integrated bioinformatic analyses showed that hsa-miRNA-21-5p is associated with poor prognosis in patients with lung adenocarcinoma and can promote lung cancer progression through multiple signaling pathways including the MAPK, PI3K/Akt, and TNF signaling. Furthermore, in mouse xenograft models, SC exosomes and SC exosomal hsa-miRNA-21-5p augmented human lung cancer cell growth and lymph node metastasis in vivo. Together our data revealed, for the first time, that SC-secreted exosomes and exosomal miRNA-21-5p promoted the proliferation, motility, and spreading of human lung cancer cells in vitro and in vivo. Thus, exosomal miRNA-21 may play an oncogenic role in SC-accelerated progression of lung cancer and this pathway may serve as a new therapeutic target for further evaluation.