Radiotherapy-induced overexpression of exosomal miRNA-378a-3p in cancer cells limits natural killer cells cytotoxicity.

We here hypothesized that tumor-derived exosomal miRNA (TexomiR) released from irradiated tumors may play a role in the tumor cells escape to natural killer (NK) cells. Our study included the use of different cancer cell lines, blood biopsies of xenograph mice model and patients treated with radiotherapy. The irradiation of cancer cells promotes the TET2-mediated demethylation of miR-378 promoter, miR-378a-3p overexpression and its loading in exosomes, inducing the decrease of granzyme-B (GZMB) secretion by NK cells. An inverse correlation between TexomiR-378a-3p and GZMB was observed in murine and human blood samples. Our work identifies TexomiR-378a-3p as a molecular signature associated with the loss of NK cells cytotoxicity via the decrease of GZMB expression upon radiotherapy.