Study On The Role Of CircRNAs In The Process Of Radiation-Induced Intestinal Injury And The CGAS-STING Signaling In Cancer Progression

The small intestine is highly sensitive to ionizing radiation,and is the main injury site of radiation therapy for abdominal and pelvic tumors as well as exposure to nuclear accidents.Radiation-induced intestinal injury can cause anorexia,vomiting,diarrhea,dehydration,systemic infection,and even death.Currently,there isn't effective ways to prevent or treat radiation-induced intestinal injury.Circular RNA?circRNA?is a large class of non-coding RNAs.It has shown that circRNAs play an important role in the regulation of physiological functions.However,the role and mechanism of circRNAs in radiation-induced intestinal injury are not clear.This topic explores the role of circRNAs in radiation-induced intestinal injury.Firstly,mice were divided into two groups:the control group and the irradiated group.The irradiated group was administrated 14 Gy abdominal irradiation to establish a model of radiation-induced intestinal injury,and the model was verified by pathological experiments.Then the jejunal was performed transcriptome sequencing.2751 circRNAs was detected in the two groups,and 90 differentially expressed circRNAs was screened.The analysis of GO and KEGG signaling pathways in differentially expressed circRNAs targeted mRNAs revealed that these circRNAs were involved in cytokine secretion and MAPK signaling pathway,providing a basis for further study of the mechanism of circRNAs in radiation-induced intestinal injury.Secondly,a novel circRNA was screened by qRT-PCR in significantly up-regulated circRNAs after radiation,named circDmbtl₃456.The circRNA has significant tissue specificity,i.e.,has high expression only in the intestine,and is therefore suspected to be closely related to radiation-induced intestinal injury.Then,overexpressing circDmbtl₃456 in mouse intestinal epithelial cells,its effect on radiation sensitivity and DNA damage/repair at the cellular level was investigated.The colony formation experiment indicated that overexpression of circDmbtl 3456 could enhance the radiation resistance.Comet assay and y-H2AX immunofluorescence assay demonstrated that overexpression of circDmbtl₃456 reduced radiation-induced DNA damage.The flow cytometry assay indicated that overexpression of circDmbtl₃456 could reduce the radiation-induced G2/M phase arrest.Rad51 immuno-fluorescence assays demonstrated that overexpression of circDmbtl 3456 enhanced Rad51-mediated DNA damage repair.Finally,this subject also explored the possible mechanism preliminarily.The RNA pull down and RNA IP experiments demonstrated that circDmbtl₃456 may binding Parpl protein to mediate downstream function.In summary,this study identified that circRNAs changing during the process of radiation-induced intestinal injury,and explored the effects and mechanisms of circDmbtl₃456.This topic systematically studied the relationship between circRNAs and radiation-induced intestinal injury,and opened up new ideas for the study of radiation-induced intestinal injury.Recent studies reveal critical roles for cyclic GMP-AMP synthase?cGAS?and stimulator of interferon genes?STING?signaling axis in innate and adaptive antitumor immunity of tumor microenvironment?TME?.However,little is known regarding the regulation of cGAS-STING signaling in cancer cells.Herein,we investigated the role of cGAS and STING in cancer.Firstly,Cancer cells treated with STING agonist 2',3'-cGAMP produced cytokines,e.g.,CCL5,CXCL10,and CXCL11,which served as chemo-attractants of immune cells.Injection of the 2',3'-cGAMP induced tumor regression in vivo in syngeneic and immunodeficient mice grafted with cancer cells and a spontaneous breast tumor model.Secondly,We explored the role of cGAS protein in cancer progression.Knockout of Mb21dl gene?encoding mouse cGAS?in colon carcinoma MC38 cells eliminated tumor growth in vivo.Immunohistochemistry?IHC?staining in breast cancers showing heterogeneously inter-tumorous expression of cGAS and STING protein.STING expression in breast cancers were elevated as compared to normal breasts and significantly correlated.cGAS protein expression were reduced,and relatively loweer levels of cGAS protein expression in cancer cells correlates with better clinical outcomes.Finally,in a retrospective cohort of breast cancer patients,we found that double negative expression of cGAS and STING in cancer cells independently conferred a lower risk of relapse and significantly correlated with longer relapse-free and overall survival.This finding may further enhance the accuracy of prognostic testing and precision medicine for the clinical management of breast cancer.Together,these data demonstrated that deregulation of cGAS-STING signaling,including abnormal protein expression or activation in cancer cells,contributes to ungoverned tumor growth,which warrants precisely targeted therapies aiming at abnormality of cGAS-STING signaling in cancer treatment.