Expression Profile Analysis Of Long Noncoding RNA In Gastric Cancer

Background and Objective:Gastric cancer is one of the most frequent malignant tumors in the world, especially in East Asian countries, and is also one of the leading causes of cancer death. Due to the lack in effective diagnostic markers, most patients with gastric cancer miss the most appropriate time for diagnosis and treatment, leading to advanced stage, metastasis of tumor and even terminal stage upon presentation.The results of the entire human genome sequencing show that only 1.5-2.0% of genes, termed protein coding gene (PCG), code for proteins. The remaining genes correspond to large noncoding protein regions, which include amounts of transcriptional regulatory elements and noncoding RNA (ncRNA) genes. Usually, noncoding RNA cannot be translated into protein. According to the sizes of noncoding RNA, as well as the number of bases, noncoding RNAs are divided into long noncoding RNA (lncRNA) and small noncoding RNA (sncRNA). LncRNA is a kind of functional RNA which is longer than 200nts, lacking in open reading frames and the ability to code for proteins. Many recent studies have reported that lncRNA is closely related to human diseases, including cancers such as lung, breast, gastric cancer. Many lncRNAs are expressed differentially in gastric cancer, and have been shown to be involved in both oncogenesis and tumor suppressor pathways of gastric cancer, such as cell proliferation and apoptosis.In a bid to discover new biomarkers of gastric cancer, the expression profile of lncRNA in gastric cancer and identified gastric cancer specific lncRNA were obtained from clinical surgical specimens, via microarray and bioinformatics.Experimental summary and methods:1. We collected specimens of four paired gastric cancer and adjacent normal tissue, of which clinical pathological stage is I without lymph node metastasis. Patients’blood tests such as common tumor markers, liver and kidney functions were normal before surgery. After individual isolation of total RNAs, we analyzed the expression of lncRNA and mRNA via microarray, with volcano plot, scatter plot and cluster analysis.2. KOBAS analysis and GO analysis were used to analyze aberrant expressed mRNA and lncRNA co-expressed mRNA to predict possible biologic processes. LncRNA and associated transcripts were also analyzed.3. According to the results above, we chose 10 lncRNAs,5 up-regulated and 5 down-regulated, to verify their expression in gastric tissues and cell lines, in order to identify new potential markers related to gastric cancer for further study.Results:1. With the method of gene microarrays, we found 568 lncRNAs and 523 mRNAs significantly up-regulated, while 170 lncRNAs and 741mRNAs were significantly down-regulated, compared with adjacent normal tissues. This suggests that lncRNA is expressed differently in gastric cancer versus that in paired adjacent normal tissues.2. The results of KOBAS analysis and GO analysis indicated that lncRNAs aberrantly expressed were associated with many biologic processes, such as metabolism, EGFR and angiogenesis, cell apoptosis and ATPase activity.3. The results of qRT-PCR showed that 2 up-regulated lncRNAs (LINC00152 and AK001796) significantly up-regulate both in tissue and cell lines (HGC-27、SNU-5、SGC-7901、 N87), suggesting that the two lncRNAs to be closely related to gastric cancer and may function as potential markers.Conclusion:Firstly, we conducted gastric cancer related lncRNA expression profile, and identified aberrantly expressed lncRNAs. With the analysis of KOBAS and GO, we explored the function and signal pathways in which lncRNA may be involved. Finally, we identified 2 aberrantly expressed gastric cancer-specific lncRNAs (LINC00152 and AK001796) for further study.