The Research Of MicroRNA Involved In Radiation-induced Bystander Effects

Recent studies show that micro RNA may play an important role in radiation-induced bystander effects. The aims of this work were to investigate the relationship between micro RNAs and radiation-induced bystander effects(RIBE), and reveal the specific role that micro RNA played in radiation-induced bystander effects. Human fetal lung MRC-5 fibroblasts cell line was used in this study. Using ionizing radiation treatment technique and conditioned-medium transfer method, we established a medium-mediated RIBE research model with frequency of micronuclei and yields of 53BP1 foci and clonogenic survival fraction as biological endpoints. After exposure to X-rays, expression level of mi RNAs was detected by Solexa sequencing. Followed with screening and verifying, mi R-21 was picked out for further investigation about the possible role it played in RIBE. Using fluorescent markers and q RT-PCR methods, we identified that exosomes with mi RNAs cargo were able to shuttle between cells. Subsequently, we manipulated the expression level of mi R-21 in cells and prove that mi R-21 induce RIBE through exosomes. We further identified the mechanism of exosome mediated intercellular communication between tumor cells and normal cells, and primary investigated the mechanism of exosome induced RIBE. The main results of this study were summarized as follows:1. Radiation induced bystander effects were induced in human fetal lung MRC-5 fibroblasts through medium-mediated way by different types of radiation;2. We identified a set of differentially expressed micro RNAs in the cell and culture medium after irradiation, among which the up-regulation of mi R-21 in IR cells and conditioned medium and bystander cells was further verified;3. Transfection of mi R-21 mimics into non-irradiated MRC-5 cells caused bystander-like effects;4. Micro RNA as cargo of exosomes shuttle between same kind of cells or tumor and normal cells;5. Mi R-21 induced RIBE through exosomes.Based on the medium-mediated RIBE research model, our research identified the differentially expressed micro RNAs in the cell culture medium after irradiation. We verified the expression pattern of mi R-21 in the process of bystander effects and firstly reported the mi R-21 induced RIBE through exosomes, which revealed the important roles of mi RNAs and exosomes within RIBE. This research provides potential ideas and method to cancer therapy and prognosis.