Effect Of Tumor-associated MicroRNAs On The Longevity And Function Of Dendritic Cells

Dendritic cells (DCs) are the strongest antigen presenting cells which connect innate immunity and adaptive immunity. They can regulate the immune response and induce the immune tolerance in vivo. DCs play an important role in tumor immunity. On one hand, DCs inhibit tumor growth. On the other hand, the growth of the tumor impairs the function of DCs and the whole immune system profoundly. In this thesis, we focus on the effect of certain tumor associated miRNAs and their target genes on the survival and function of DCs. Main findings:(1) Identification of tumor associated miRNAs in dendritic cells. Through microarray-chip, combined with RT-PCR, we have analyzed the up-and down-regulated miRNAs in tumor associated DCs, which are coclutured with tumor cells, and demonstrated several tumor associated miRNAs, such as miR-22, miR-128and miR-503.(2) Tumor-associated miR-22and miR-503modulate the survival and longevity of dendritic cells by targeting YWHAZ and Bcl2signaling pathways. Tumors use a wide array of immunosuppressive strategies, such as reducing the longevity and survival of dendritic cells (DCs), to diminish immune responses and limit the effect of immunotherapy. We found that tumors upregulate the expression of multiple microRNAs (miRNAs), such as miR-16-1, miR-22, miR-155, and miR-503. These tumor-associated miRNAs influenced the survival and longevity of DCs by affecting the expression of multiple molecules that are associated with apoptotic signaling pathways. Specifically, miR-22targeted YWHAZ to interrupt the PI3K/Akt and MAPK signaling pathways, and miR-503downregulated Bcl2expression. The increased expression of miR-22and miR-503in the tumor-associated DCs causes the reduced survival and longevity of DCs. Thus, tumor-associated miRNAs can target multiple intracellular signaling molecules to cause the apoptosis of DCs in the tumor environment. Use of miR-22and miR-503as inhibitors may therefore represent a new strategy to improve DC-based immunothcrapies against tumors. (3) Tumor-associated mir-22affects DCs’ functions by targeting p38MAPK. p38, a critical molecule of the MAPK signaling pathway, has a crucial role in regulating the maturation and activation of DCs. We demonstrate that mir-22regulates P38’s expression by acting on p38’s3’-UTR. Transfection of miR-22increase the excretion of cytokine IL-6. DC transfected using miR-22may mediate the differentiation of naive T cell toward Th17cell. In vivo experiments demonstrate that miR-22can promote the immune ability against tumors. Thus, our research suggests that miR-22can be potentially acted as a targeting molecule for tumor immunotherapy.(4) miR-128targets p38to regulate the production of IL-6in DCs. Combined with bioinformatics analysis, p38was predicted as potential target of series of microRNAs. In this study, using dual luciferase reporter assays, our results demonstrate that miR-128could repress p38expression by binding to the3UTR of p38in a direct and sequence-specific manner. Moreover, transfection of miR-128mimics significantly decrease the protein level of p38in dendritic cell, and promote production of cytokine IL-6. Furthermore, results obtained in this thesis provide a new evidence for the effect of microRNA on regulating tumor immunity.In conclusion, tumor associated miRNAs may affect the survival and longevity and modulate the function of dendritic cells by targeting their targeting molecules. The results not only bring about profound impact on understanding the mechanisms of tumor incidence and development but also on the immunotherapy against tumors.