Identification Of Gastric Cancer-Related PiRNAs And Their Functions Analysis

ObjectiveTo analyze and identify the differential expressed piRNAs between gastric cancer tissues and paired non-cancerous tissues, to explore the association between their expression and clinicopathological features of gastric cancer; and to study their biological effect in gastric carcinogenesis and to estimate their potential diagnostic value.Methods1. To screen the aberrantly expressed piRNAs, total RNA isolated from gastric cancer and paired non-tumor tissues was used in piRNA microarray assay.2. Real-time RT-PCR was used to detect the expression level of gastric cancer-related piRNAs in gastric cancer tissues and then their association with clinicopathological features such as tissue cllassificatin, differentiation, diameter, invasion, etc. was analyzed.3. The specific inhibitor and mimic of gastric cancer related-piRNAs were designed and synthesized, and then were transfected into gastric cancer cell lines using Lipofectamine 2000 reagent. To probe their possible mechanism in gastric carcinogenesis, MTT assay, flow cytometry and nude mouse transplantation model were used.4. Recovery experiment was used to explore the relationship between the piRNA level and quantity of cancer cells in peripheral blood.5. Analyze the relationship between piR-823 level in peripheral blood of patients with gastric cancer and their clinicopathological features. Analyze its specificity and sensitivity and then evaluated the diagnostic value of gastric cancer-related piRNA.Results1. By cluster analysis from the results of piRNA chip, which domenstrated the differentially expressed piRNAs between gastric cancer tissues and paired non-tumor tissues, two significant aberrantly expressed piRNAs, piR-651 and piR-823, were found in gastric cancer tissues.2. piR-651 and piR-823 were found higherly and lowerly expressed in gastric cancer tissues comparing with paired non-tumor tissue, respectively. No association between their levels and clinicopathological features was found. 3. The growth of gastric cancer cells was both suppressed by both piR-651 inhibitor and piR-823 mimic. The piR-651 inhibitor arrested MGC-803 cells at G₂/M phase; and gastric tumor growth (volumes and weight) was significantly suppressed by piR-823 mimic.4. In recovery experiment, a significant linear relationship between the piR-823 level and the number of circulating tumor cells was found.5. The piR-823 level in peripheral blood from patients with gastric cancer was related with the T stage and distant metastasis. Its specificity and sensitivity were higher then those of common used tumor markers such as CEA and CA19-9.ConclusionGastric cancer-related piRNAs may play crucial role in gastric carcinogenesis. The growth of gastric cancer cells were suppressed by regulating the gastric cancer-related piRNAs levels. piR-823 with other piRNAs may become a biomarker in gastric molecular diagnosis.