MicroRNA-30a controls the instability of inducible [CD4.sup.+] Tregs through SOCS1

Inducible regulatory T cells (iTregs) are an important subset of Tregs and play a role in the maintenance of peripheral tolerance, and the occurrence of a number of diseases, including tumors and autoimmune diseases. However, the instability of iTregs is a major obstacle for their potential application in clinical trials. The underlying mechanism of iTreg instability remains largely unknown. In the present study, the expression level of microRNA (miRNA/miR)-30a in murine iTregs was evaluated using reverse transcription-quantitative PCR. miR-30a mimics and a miR-negative control (NC) were transiently transfected into iTregs using Nucleofector technology. The effects of miR-30a on the suppressive function of murine iTregs in vitro and in vivo were investigated using MTT, adoptive cell transfer (ACT) and flow cytometry assays, as well as a murine model of lung cancer. In the present study, it was identified that the expression level of miR-30a was lower in murine iTregs in vitro compared with natural (n)Tregs. Furthermore, compared with miR-NC, miR-30a mimics impaired the suppressive function of murine iTregs on murine [CD4.sup.+] T cell proliferation in vitro, which was accompanied by the altered expression of cytotoxic T lymphocyte-associated antigen 4 and glucocorticoid induced tumor necrosis factor receptor, as well as transforming growth factor-[beta] and interleukin-10. It was also observed that, compared with miR-NC, miR-30a mimics abrogated the suppressive effects of murine iTregs on murine [CD8.sup.+] T cell function in vivo, producing an effective antitumor effect in mice bearing 3LL lung cancer cells in the ACT assay. From a mechanistic point, the expression level of suppressor of cytokine signaling 1, a putative target of miR-30a, was elevated, altering the activation of the Akt and STAT1 pathway in the miR-30a mimic transfected group compared with the miR-NC group, reducing the suppressive function of murine iTregs. The present study identified a role for miR-30a in the instability of iTregs and provided a novel insight into the development of therapeutic strategies for promoting T-cell immunity via the regulation of iTreg instability by targeting specific miRNAs. Key words: [CD4.sup.+][Foxp3.sup.+] Treg cells, microRNA-30a, lung cancer, SOSC1, TGF-[beta]