MicroRNAs in immune regulation--opportunities for cancer immunotherapy

Endogenously produced microRNAs are predicted to regulate the translation of over two-thirds all human gene transcripts. Certain microRNAs regulate expression of genes that are critically involved in both innate and adaptive immune responses. Immune cells represent a highly attractive target for microRNA gene therapy approaches, as these cells can be isolated, treated and then reintroduced into the patient. In this short review, we discuss how recent discoveries on the roles of microRNAs in immune-regulation will advance the field of cancer immunology and immunotherapy. Targets identified already in T cells include microRNAs, miR-17-92 family, miR-155, and miR-181a. In macrophages, miR-125b, miR-146, and miR-155 act as Pathogen Associated Molecular Pattern Molecule-associated microRNAs and miR-34C and miR-214 as Damage Associated Molecular Pattern Molecules-associated miRs. We have also demonstrated that the ability of tumors to serve as targets for cytolytic effectors is regulated by miR-222 and miR-339.