The Function Of MiR-31Inhibits Gastric Cancer Metastasis And Its Mechanism

BackgroundThe miR-31gene is located at9p21.3. Although there is growing evidenceshowing that miR-31has different expression patterns in different cancers, theexact function of miR-31involved in cancer remains unclear. Recent studies haveshown that miR-31expression is specifically attenuated in metastatic breastcancer cells compared with that in normal breast cell and miR-31inhibited breastcancer metastasis by targeting multiple genes including ITGA5, RDX and RhoA.Our previous studies have revealed that miR-31was down regulated in distalgastric adenocarcinoma tissues by microarray analysis. In our initiation study wealso found that overexpression of miR-31suppressed gastric cancer cell migrationin vitro demonstrated that overexpression of miR-31has the effect of suppressinggastric cancer cell metastasis. The further study of the biological functions ofmiR-31in gastric carcinoma metastasis will be of great help in understanding themechanisms of occurrence and progression of gastric carcinoma and underlyingmechanisms of metastasis.Objectives1. To examine the expression of miR-31in gastric cancer tissues and celllines and to analyze its relationship between miR-31expression and theclinicopathlological features.2. To analyze the effects of miR-31on gastric cancer cell proliferation,invasion, migration and adhesion in vitro.3. MiRNA targets prediction softwares were used to predict which targetgenes may contribute to miR-31mediated of gastric cancer metastasis.Methods1. To examine the expression of miR-31in human gastric cancer tissues, twenty pairs of human gastric cancer tissues and adjacent non-tumor tissues wereobtained from patients who underwent surgical resection at the Chinese PLAGeneral Hospital. Real-time quantitative reverse transcriptase-PCR was used todetect the expression of miR-31in gastric cancer tissues. The correlationsbetween miR-31expression and clinicopathological features were analyzed bynon-parametric tests. RT-PCR was also used to detect the expression of miR-31ingastric cacer cell lines SGC-7901and BGC-823as well with the normal gastriccell line GES-1.2. To explor the function of miR-31on gastric cancer cells, the tumorbiology behviors of SGC-7901and BGC-823cells transfected with miR-31mimics and negative control were analyzed by apotosis detect assay, colonyformation assay, transwell cell migration and Matrigel invasion assay, Scatchhealing and adhesion assay.3. The miR-31targets predicted by computer-aided algorithms wereobtained from PicTar (http://pictar.mdc-berlin.de/), TargetScan6.2(http://www.targetscan.org/vert-61/) and miRDB (http://mirdb.org/miRDB/).Then, the overlap of these results were further studied by Gomir analysis softwarebased on the Gene ontology database. Then we determined which genes maycontribute to gastric cancer metastasis by western-blot.Results1. We found significant low expression of miR-31in twenty gastric cancertissues compared with their non-tumor counterparts by real-time RT-PCR. Wealso found significant down-expression of miR-31in two gastric cancer cell linescompared with GES-1cell lines. Moreover, the expression of miR-31wasdemonstrated to be associated with lymph-node metastasis, poor pT stage, poorpN stage by non-parametric tests.2. Transwell cell migration and Matrigel invasion assay and Scatch healingassay in BGC-823, SGC-7901cell lines demonstrated that overexpression ofmiR-31has the effect of suppressing gastric cancer cell invasion and metastasis. 3. We used PicTar, TargetScan and miRDB software to predict the miR-31target and bioinformatics indicates that AKAP7、APBB2、CTNND2、 HIAT1、HIF1AN、JAZF1、KHDRBS3、MAP4K5、PEX5、 PPP2R2A、RGS4、RHOA、 RSBN1、 SEPHS1、 SH2D1A、 SLC6A6、 SNX4、 STX12、TACC1、TACC2、YWHAE were the co-targets. Bioinformatics analysis indicates thatRhoA might be the targets of miR-31.Conclusions1. MiR-31may associated with in gastric cancer initiation, development andprogression. MiR-31was down regulated in gastric cancer tissues compared withthat in their matched non-tumor adjacent tissues. The expression levels of miR-31were associated with lymph-node metastasis and poor pN stage.2. Increased expression of miR-31significantly suppresse the invasion andmigration abilities of gastric cancer cells in vitro. But there are no significanteffect of miR-31on proliferation and apoptosis of gastric cancer cells.3. RhoA might be a functional target of miR-31in regulating gastric cancermetastasis.