The Role And Mechanism Of Gastric Cancer Cell-derived Exosomes MiR-431-5p In Inhibiting Gastric Cancer By Inducing Ferroptosis

Globally,epidemiological surveys had confirmed that there were more than 1 million new gastric cancer cases and nearly 800,000 deaths each year.More than 70%of gastric cancer cases occur in developing countries,including China.Therefore,gastric cancer was a malignant tumor that threatens human health.Cell death research was critical for the prevention and treatment of hyperproliferative diseases,including cancer.Ferroptosis was a novel form of cell death proposed in 2012,characterized by iron-dependent lipid peroxidation.Tumor cells could adapt to an oxidative environment to regulate ferroptosis and promote tumor growth and malignant progression.Induction of ferroptosis in tumor cells has been shown to be an effective strategy for the treatment of tumors.At present,the important role of the ferroptosis pathway in the malignant progression and treatment of gastric cancer has been confirmed,but its molecular mechanism was still unclear.Exosomes belonged to a family of extracellular vesicles with a diameter of 30-100 nm.Exosomes secreted by tumor cells play a crucial role in the establishment of the tumor microenvironment.Therefore,exosomes could act as information mediators to deliver oncogenic factors secreted by cancer cells into stromal cells.For example,the delivery of micro RNA（miRNA）via exosomes has been extensively reported.Tumor cell-derived exosomes miRNA could affect the development of gastric cancer by entering recipient cells and regulate gene or protein expression,thereby inhibiting or activating certain signaling pathways.Therefore,exosomal miRNA in gastric cancer cells could be used as biomarkers and tools for targeted therapy in gastric cancer.miR-431-5p was a widely studied miRNA in a variety of diseases,and its role in tumors had been widely demonstrated.However,whether exosomal miR-431-5p had an inhibitory effect on gastric cancer by inducing ferroptosis in gastric cancer cells and the mechanism of action were still unclear.Based on this,the following research work was carried out.1.Expression analysis of miR-431-5p in gastric cancer tissues and exosomes of blood samples from clinical patientsCompared with clinical gastric cancer adjacent tissue,miR-431-5p showed significantly lower expression in clinical gastric cancer tissue.Compared with normal human blood sample exosomes,miR-431-5p in clinical gastric cancer patient blood exosomes also showed significantly lower expression.The results showed that the expression of miR-431-5p was significantly negatively correlated with gastric cancer.2.Effects of gastric cancer cell-derived exosomes miR-431-5p on gastric cancer cell proliferation,apoptosis,migration,invasion and tumor growth.Gastric cancer cell-derived exosomes miR-431-5p has the potential to impede the proliferation,migration,and invasion of gastric cancer cells,while augmenting apoptosis.In vivo experiments showed that miR-431-5p also significantly inhibited mouse gastric cancer cell SGC7901 growth of transplanted tumors.3.The effect of gastric cancer cell-derived exosomes miR-431-5p on gastric cancer cell ferroptosisCompared with the control group,gastric cancer cell-derived exosomes miR-431-5p could significantly upregulate the total iron content,lipid ROS content and Fe²⁺content in SGC7901 and HGC27 cells,and significantly inhibited the expression of SLC7A11 and GPX4 in SGC7901 and HGC27 cells.The results showed that gastric cancer cell-derived exosomes miR-431-5p could induce ferroptosis in gastric cancer cells.4.The mechanism of gastric cancer cell-derived exosomes miR-431-5p induced ferroptosis in gastric cancer cellsFirst,potential interaction sites of miR-431-5p and SLC7A11 3’UTR were identified.Compared with the control group,gastric cancer cell-derived exosomes miR-431-5p significantly inhibited the reporter gene activity of SLC7A11 3’UTR in gastric cancer cells SGC7901 and HGC27,indicating that miR-431-5p can regulate the expression of SLC7A11at the post-transcriptional level.miR-431-5p also significantly inhibited the expression of SLC7A11 m RNA and protein levels in gastric cancer cells SGC7901 and HGC27.Although the gastric cancer cell-derived exosomes miR-431-5p can significantly increase the contents of total iron,lipid ROS,Fe²⁺and MDA and inhibit the GSH level in SGC7901 and HGC27cells.However,the increase degree of miR-431-5p on the contents of total iron,lipid ROS,Fe²⁺and MDA,as well as the inhibitory effect on GSH level were reduced by SLC7A11overexpression treatment.Similarly,gastric cancer cell-derived exosomes miR-431-5p could significantly inhibit the expression of SLC7A11 and GPX4 in SGC7901 and HGC27 cells,but the degree of inhibition of SLC7A11 and GPX4 expression was also attenuated by SLC7A11 overexpression treatment.In addition,the effects on the proliferation and apoptosis of gastric cancer cells are also consistent with the above conclusions.These results indicate that SLC7A11 can participate in the process of gastric cancer cell-derived exosomes miR-431-5p inducing gastric cancer cell ferroptosis.In conclusion,the results provide basic research data for exosomal miRNA-induced fer-roptosis in tumor cells,indicating that gastric cancer cell-derived exosomesmiR-431-5 is ex-pected to provide a new therapeutic strategy for gastric cancer,which has important clinical significance.