Abstract: Exosomal miRNAs, derived from tumor cells or their microenvironment, could promote the proliferation, migration and invasion of tumor cells; and enhance tumor metastasis via regulating information exchange between tumor cells and immune cells or metastatic target organs; and induce tumor resistance to cisplatin and gemcitabine; meanwhile, detecting the exosomal miRNAs in the serum and saliva of cancer patients suggested the potential of application in cancer diagnosis and prognosis assessment.

Key words: tumor, microenvironment, exosome, miRNAs, tumorigenic mechanism.