Exosomal miR-499a-5p promotes cell proliferation, migration and EMT via mTOR signaling pathway in lung adenocarcinoma

Tumor-derived exosomes contain informative microRNAs involved in carcinogenesis, cell migration, invasion and epithelial-mesenchymal transition (EMT), eventually contributing to metastasis of cancers. This study aims to clarify which and how exosomal miRNA affects tumor carcinogenesis and metastasis. Among them, miR-499a-5p was upregulated in both highly metastatic lung cancer cell line and their exosomes. MiR-499a-5p over-expression promoted cell proliferation, migration and EMT, while miR-499a-5p knockdown suppressed these processes in vitro. Inhibition of miR-499a-5p by antagomirs administration restrained tumor growth in vivo. Consequently, miR499a-sufficient exosomes, derived from highly metastatic cell line, enhanced cell proliferation, migration and EMT via mTOR pathway, and the effect could be inhibited by miR-499a-5p inhibitor. The study reveals the potential diagnostic and therapeutic value of cancer-derived exosomal miR-499a-5p, and sheds a new insight on a novel molecular mechanism which modulates metastasis.