| Background:Gastric cancer is one of the most prevalent malignant tumors worldwide. In China, gastric cancer is among the most common deadly cancer with more than30million new cases per year and over260,000deaths. The ratio of incidence of gastric cancer between men and women is about3to1. Epidemiological studies have shown that HP(helicobacter pylori) infection, dietary factors (such as high salt-containing food, N-nitroso compounds, insufficient intake of fresh vegetables and fruits), smoking, obesity, family history of cancer, etc., are all closely related with gastric cancer risk.Although people are exposed to the same environmental risk factors, only a fraction of individuals eventually develop into gastric cancer. Similarly, patients with the same pathological type and clinical TNM stage and receiving the same treatment regimen, have different response to treatment and survival, suggesting that individual susceptibility is an important determinant in gastric carcinogenesis. A large number of studies have shown that genetic variation determines the genetic susceptibility of individuals suffering from tumor. At present, the majority of genetic variation is SNP (single nucleotide polymorphism). It has been widely used as molecular markers in the exploration of disease etiology, treatment and prognosis assessment.MicroRNA is a class of evolutionarily conservative endogenous non-coding small RNA widespread in viruses, plants and animals. Research has shown that miRNA can function as oncogene or tumor suppressor gene in the initiation and development of gastric cancer, which provides a novel tool for the diagnosis, treatment and prognostic assessment of gastric cancer. Some miRNAs have been identified as significantly differentially expressed in gastric cancer. However, the most strategy of studies is based on candidate miRNA genes. The number of studies on miRNA profile of gastric cancer is small. The biological functions of most miRNAs are still largely illusive and their functional mechanism need to be further investigated.Objective:The present study aimed to identify the differentially expressed miRNAs in the gastric cancer and explore genetic variation of relevant miRNAs that could alter their expression. Thereafter, we would explore the cooperation between genetic and epigenetic variation in the regulation of gastric cancer development and prognosis. Our study will provide theoretical basis and practical guidance for gastric cancer prevention, individual therapy and prognostic judgement.Methods and Results:Agilent human microRNA microarray was used to profile miRNAs expression in five gastric cancer tissues and their matched adjacent normal tissues. The results showed that eight miRNAs were significantly up-regulated in the gastric cancer tissues (miR-1246,103,107,185,15a,15b,21*, let-7d) while4down-regulated (miR-148a,29c,551b,26a). When screening miRNAs with the lowest false discover rate using the SAM software,5of12significantly differentially expressed miRNAs were identified, i.e., miR-1246,103,107,29c and148a, with a threshold of q<0.05.The results of luciferase assay and NF1mRNA stability assay indicated that miR-107binding to the first binding site within the3’-UTR of NF1could degrade the NF1mRNA stability and thus its protein expression. The results of cell proliferation assay, wound healing assay and transwell assay indicated that inhibition of miR-107expression could up-regulate of NF1expression, which in turn depressing the expression of p-Erk, consequently, inactivating the proliferation, migration and invasion of gastric cancer cell lines.By direct sequencing, we found3SNPs (rs11185777, rs78591545and rs2296616) with minor allele frequency (MAF)>0.05in the flanking region of pre-miR-107gene. We enrolled715gastric cancer cases and804controls to analyze the association of3SNPs with gastric cancer susceptibility. The results showed that the CC genotype of SNP rs78591545was associated with a significantly decreased risk of gastric cancer compared with the CC/CT genotypes (TT vs. CC/CT, adjusted OR=0.58,95%CI=0.37-0.92). Similarly, the TC/CC genotypes of SNP rs2296616were also associated with a significantly decreased risk of gastric cancer compared with the TT genotype (TC/CC vs. TT, adjusted OR=0.48,95%CI=0.37-0.61). We further investigated the relationship between the3SNPs and gastric cancer survival. There were940gastric adenocarcinoma patients with follow-up information included in the study. We observed that none of the3SNPs was related to gastric cancer survival. However, in the stratified analysis, we found that the TC/CC genotypes of SNP rs2296616were significantly associated with unfavorable survival of gastric cancer among the subgroups of age>60years, cardia gastric cancer and clinical TNM stage III when compared with the TT genotype (adjusted HR=1.41,95%CI=1.03-1.94for age>60years;1.49,1.01-2.20for cardia gastric cancer;1.41,1.01-1.99for clinical TNM stage Ⅲ).The mRNA analysis showed that individuals with TC/CC genotypes of SNP rs2296616had lower miR-107but higher NF1expression than those with TT genotype, suggesting that SNP rs2296616could have an impact on the miR-107expression and consequently NF1expression. Luciferase assay indicated that SNP rs2296616that located in the5’flanking region of pre-miR-107did not change the transcriptional activity of the gene.Conclusion:Our study found that SNP rs2296616may contribute to the development and progression of gastric cancer, which could be a marker for gastric cancer risk and prognosis. |
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