The present invention provides materials and methods related to the discovery that tumor secreted miR-21 and miR-29a can function by binding as ligands to receptors of the Tolllike receptor family, murine TLR7 and human TLR8, in immune cells, triggering a TLR-mediated prometastatic inflammatory response, which leads to tumor growth and metastasis. Thus, by acting as paracrine agonists of TLRs, secreted miRNAs are key regulators of the tumor microenvironment. This mechanism of action of miRNAs is important in the tumor-immune system communication, in tumor growth and spread, and in cancer treatment.
