| Gastric cancer is still one of the most prevalent cancers in worldwide, and its occurrence and development is an outcome of cell metabolic abnormalities which caused by the imbalance of regulatory network of many genes. Gene expression is regulated at the transcription and translation levels; thus, both transcription factors(TFs) and micro RNAs(mi RNA) play roles in regulation of gene expression. Comprehensive interaction and cooperation regulation can be observed between TFs and mi RNAs, and form a complicated regulatory network. This gene regulatory network could help us to understand cell homeostasis and physiological process, biological function, and mechanism of diseases.In the process of gastric cancer, the malignant proliferation of tumor cells is the initial factor of carcinogenesis. E2 Fs act a vital role in regulating cell cycle progression, by regulating genes required for DNA synthesis in G1/S phase. The vital function of cell-cycle imbalance in tumorigenesis makes E2 Fs is closely related to gastric cancer. The regulatory network associated with E2 Fs may help us to understand the mechanism of gastric cancer and clinicopathologic feature associated with E2 Fs futher.Mi RNA can bind to complementary target gene transcripts, thereby regulating gene transcription. Increasing evidence indicates that mi RNA play a vital role in tumor initiation, progression and metastasis. Recently, a growing body of evidence indicates that mi R-31 was involved with tumor progression and unfavorable prognosis in a variety of cancers. Bioinformatics analysis suggested that E2F2 was identified as a direct target of mi R-31. Therefore, we speculate that mi R-31 might regulate tumor progression and prognosis by upregulating E2F2 in gastric cancer.Therefore, in this study, we investigated the differentially expressed genes and mi RNAs in gastric cancer tissue using microarray. We analyzed them bioinformatically to form the TF-mi RNA regulatory network to relate expression of E2 Fs m RNAs in gastric cancer. We then analyze the function of hub gene and mi RNA in the regulatory network. In addintion, we explored the tumor inhibitive significance of mi R-31 both in gastric cancer tissues and cells, and further identified that E2F2 as a direct functional target mediates multiple suppressive actions of mi R-31 on the progression, metastasis and overall survival in gastric cancer.PartⅠ Transcription factor and mi RNA co-regulatory network associate with E2 Fs in gastric cancer.A total of 45 cases and 15 cases gastric cancer and paired adjacent normal tissues were subjected to differentially gene expression profile and differentially mi RNA expression profile analyses separately. We obtained 887 up-regulated and 93 down-regulated genes and 41 down-regulated and 4 up-regulated mi RNAs in gastric cancer tissues. Using the Transcriptional Regulatory Element Database, we obtained 105 genes that are regulated by the E2 Fs of genes and using Targetscan, mi Randa, mi RDB and mi RWalk tools, we predicted potential targeting genes of mi RNAs. We then built up the E2Fs-related TF and mi RNA co-regulatory gene network and identified 18 hub-genes and mi RNAs. These data showed overexpression of E2 F m RNAs associated with gastric cancer progression.PartⅡ Reasearch of mi R-31 inhibits the development of gastric cancerWe screens out mi R-31 might regulate tumor progression and prognosis by upregulating E2F2 in gastric cancer based on co-regulatory gene network in gastric cancer. mi R-31 expression was down-regulated in 40 gastric cancer tissues compared with the adjacent normal tissues, and low expression of mi R-31 was positively correlated with poor tumor differentiation, lymph node metastasis, advanced T stage and worse overall survival of gastric cancer patients dectected using q RT-PCR and Western blot. Ectopic expression of mi R-31 inhibited cell proliferation, enhanced apoptosis, reduced migration and invasion and blocked G1/S transition in both SGC-7901 and MGC-803 gastric cell lines after transfected with mi R-31 mimics. And enforced expression of mi R-31 could also inhibit the growth of engrafted tumors in vivo by mice xenotransplant model.Part Ⅲ The mechanism of mi R-31 inhibits gastric cancer development by targeting E2F2Here we found that the expression of E2F2 was upregulated in gastric cancer tissues, and inversely correlated with poor tumor differentiation, lymph node metastasis, advanced T stage and worse overall survival of gastric cancer. Luciferase reporter assays and western blot indicated that E2F2 is a direct target of mi R-31. The E2F2 expression had significant negative correlation with mi R-31 levels. Knockdown of E2F2 mimicked the tumor-suppressive effects of mi R-31 in gastric cancer cells. These results indicated that mi R-31 act as a crucial tumor suppressive role in the tumor progression by targeting the expression of E2F2. |
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