Abstract:Gastric cancer is one of the most malignant tumors in the world. In recent years, a number of studies have proved that noncoding RNAs play an important part in many biological processes in gastric cancer such as initiation, proliferation and metastasis. The regulatory network of nocoding RNAs consisting of the micro-RNAs (miRNAs), circular RNAs (circRNAs) and long noncoding RNAs (lncRNAs) are involved in the processes of regulating a variety of gene expressions. At present, the diagnosis of gastric cancer mainly depends on endoscopy, the simple and effective screening measures are still lacking, and the treatment modalities for advanced gastric cancer are also limited. Fortunately, the appearance of noncoding RNAs offers a new perspective for diagnosis and treatment of gastric cancer. The miRNAs can bind to the mRNAs to induce their degradation, and thereby regulate the expressions their target mRNAs at post-transcriptional level. The lncRNAs and circRNAs are able to antagonize the functions of miRNAs by competitively harboring miRNAs, and thereby indirectly regulate the gene expressions. Tumorigenesis can be regarded as the joint outcome of the abnormal features of tumor cells, the formation of tumor microenvironment and the influences of external environmental factors. The noncoding RNAs are closely related to the proliferation, apoptosis, invasion and metastasis of gastric cancer cells. Furthermore, the noncoding RNAs are associated with the autophagy and have great influence on stemness and drug resistance of gastric cancer cells. Tumor microenvironment is generally consisted of the components such as the tumor peripheral vasculature, mesenchymal cells, immune cells, signaling molecules and extracellular matrix. On the one hand, the noncoding RNAs are involved in the process of the formation of tumor microenvironment such as angiogenesis and immunosuppression induced by gastric cancer cells. On the other hand, the noncoding RNAs can function as exosomes to participate the action of microenvironment on gastric cancer cells, so as to affect the biological processes that include the proliferation, metastasis, drug resistance of gastric cancer cells. External environmental factors have great significance for inducing tumorigenesis of gastric cancer. Helicobacter pylori (HP) infection is one of the important causes for the occurrence of gastric cancer, and the noncoding RNAs considerably contribute to the oncogenic properties of the HP. In addition, oxidative stress and EB virus infection can also lead to tumorigenesis of gastric cancer, which are as well associated with the noncoding RNAs. The noncoding RNAs have potential to serve as diagnostic biomarker or therapeutic targets for gastric cancer owing to their essential roles in gastric cancer. The pattern of gene expression modulation shown by majority of current reports is post-transcriptional gene regulation by miRNAs serving as the central event with the lncRNAs or circRNAs as upstream regulators. Both lncRNAs and circRNAs competitively combine with the mRNAs but their reciprocal relationship is still unidentified. The actions of circRNAs in tumor are roughly recognized in recent years and their specific roles in gastric cancer remain to be further explored. Full understanding of the roles of noncoding RNAs in gastric cancer will not only help gain insights into the mechanism of tumorigenesis but may provide novel avenues for diagnosis and treatment gastric cancer. In the future, the noncoding RNAs may probably be used for description of different characteristics of gastric cancer after specification and subdivision, and become the “tumor identity cards” just as genes, which also has great significance for the development of precision medicine or personalized medicine.