MicroRNA 155 (miR-155) plays important roles in the regulation of the development and functions of a variety of immune cells. We previously revealed a vital role of miR-155 in regulating the function of dendritic cells (DCs) in
breast cancer. miR-155 deficiency in DCs impaired their maturation, migration,
cytokine production, and ability to activate T cells. In the current study, to exploit the therapeutic value of miR-155 for
breast cancer, we examined the impact of overexpression of miR-155 on antitumor responses generated by DC
vaccines. We boosted miR-155 expression in DCs by generating a miR-155 transgenic mouse strain (miR-155tg) or using lentivirus transduction. DCs overexpressing miR-155 exhibited enhanced functions in response to
tumor antigens. Using miR-155 overexpressing DCs, we generated a DC
vaccine and found that the
vaccine resulted in enhanced antitumor immunity against established breast
cancers in mice, demonstrated by increased effector T cells in the mice, suppressed
tumor growth, and drastically reduced lung
metastasis. Our current study suggests that in future DC
vaccine development for
breast cancer or other solid
tumors, introducing forced miR155 overexpression in DCs via various approaches such as viral transduction or nanoparticle delivery, as well as including other adjuvant agents such as TLR
ligands or immune stimulating
cytokines, may unleash the full therapeutic potential of the DC
vaccines.