【作者】 曾樱；

【导师】 王斌； 王雪融；

【作者基本信息】 南京医科大学 ， 药理学， 2010， 硕士

【摘要】 胃癌是最常见的消化道恶性肿瘤之一。虽然自20世纪30年代以来,胃癌的发病率在世界范围内呈下降趋势,但仍然位居肿瘤致死原因的第二位。中国属于胃癌高发区,胃癌仍然是威胁我国居民健康的重要疾病之一。胃癌的发生是多步骤、多因素的,是环境因素和遗传因素共同作用的结果。已证实其发病风险和多种基因的多态性相关,这些基因编码的信号分子包括miRNAs(microRNAs)、免疫球蛋白超家族成员、代谢酶、以及参与炎症反应、DNA修复、氧化损伤的多种信号分子等。研究者以基因遗传变异为切入点,研究其与胃癌遗传易感性的关系。鉴于胃癌多病因、涉及不同信号通路的特点,本研究着重对编码微RNAs的基因变异和炎症反应信号分子的基因变异与胃癌的遗传易感性进行了深入的研究。已有研究证实,miR-146a(microRNA-146a)和巨噬细胞移动抑制因子(Macrophage migration inhibitory factor, MIF)参与癌症发生发展。而编码这些蛋白的基因的单核苷酸多态性如Pre-miR-146a C/G、MIF-173 G/C也与基因表达水平和(或)蛋白功能密切相关。目前尚无研究关注这些基因单核苷酸多态性与胃癌遗传易感性的关系,因此,本研究采用病例对照设计,用单因素和多因素的统计分析方法,研究了Pre-miR-146a C/G和MIF-173 G/C基因多态性与胃癌遗传易感性的关系。本研究可发现与胃癌发病相关的基因型,为胃癌高危人群或易感个体的筛查提供诊断指标;可从遗传学角度进一步阐明胃癌的发病机制,为胃癌的预防和治疗提供理论依据。第一部分:Pre-miR-146a C/G基因多态性与胃癌遗传易感性为研究Pre-miR-146a C/G基因多态性和胃癌患病风险的相关性,我们进行了一项以医院为基础的病例对照研究。研究对象为304位胃癌病人和304位年龄及性别配对的对照受试者,基因型是通过PCR-RFLP方法测定。病例组和对照组基因型分布存在统计学差异(P=0.037)。相对纯合子CC基因型携带者,变异基因型(CG+GG)携带者患胃癌的风险增加了58%比值比[校正比值比(Odds Ratio,OR)为1.58,95%可信区间(Confidence Interval, CI)为1.12-2.22]。分层分析结果显示变异基因型增加的胃癌风险在低年龄组(年龄≤58)、男性和非吸烟者有显著意义(校正OR分别是1.76、1.53和1.55;95%CI分别是1.08-2.87,1.04-2.27和1.06-2.28)。进一步对肿瘤分化程度、浸润深度、发病部位和淋巴结转移等临床病理学特征与变异基因型的相关性进行分层分析,结果显示无统计学差异。研究结果表明Pre-miR-146a C/G多态性和胃癌发病风险相关。第二部分:巨噬细胞移动抑制因子-173G/C基因多态性与胃癌遗传易感性MIF是T细胞分化的细胞因子,能抑制巨噬细胞迁移,在炎症反应、酶和激素的活化以及肿瘤的发生中发挥重要作用。MIF基因位于染色体22q11.2位点,其-173G/C(rs755622)单核苷酸多态性与多种疾病的易感性密切相关。为研究MIF-173G/C多态性和胃癌风险的相关性,我们进行一项以医院为基础的病例对照研究。研究对象为283个胃癌病例和283个年龄及性别匹配的对照,基因型是通过PCR-RFLP方法测定。病例组和对照组基因型分布存在统计学差异(P=0.008)。病例组变异C等位基因频率高于对照组(P=0.015)。相对野生GG基因型携带者,变异纯合子CC基因型携带者患胃癌的风险增加3.49倍(校正OR=3.49, 95%CI=1.53-7.97)。进一步分层分析显示变异基因型(GC+CC)增加的胃癌风险在男性组有显著意义(校正OR=1.52, 95%CI=1.03-2.25)。进一步对胃癌病人的临床病理特征分层分析显示,变异基因型(GC+CC)与肿瘤浸润深度正相关。研究结果表明MIF-173G/C多态性是胃癌的一个遗传易感因素。通过对以上涉及不同通路信号分子基因变异与胃癌风险相关性的研究,并在考虑了性别、年龄、吸烟状态、居住环境、高血压和糖尿病等因素后进行的多因素分析结果,进一步佐证了胃癌的发生是多因素和多阶段逐步演变的过程,有助于在分子水平加深对胃癌病因和发病机制的认识。研究结果为制定胃癌高危人群的筛选提供了筛选指标,对胃癌的个性化预防、治疗措施提供了重要的理论依据。更多还原

【Abstract】 Gastric cancer is a major cause of morbidity and mortality among malignant tumor of digestive tract. Although the incidence of gastric cancer has decreased since the 1930s, it remains the second most fatal malignancy in the world. Gastric cancer is a major public health issue in China where about half of the worldwide gastric cancer cases occur. It is a complex, multistep and multifactorial process, and is thought to result from an interaction between genetic backgrounds and environmental factors. Epidemiological studies show that the risk of gastric cancer was influenced by polymorphisms of many genes including microRNAs, immunoglobulin superfamily members, metabolic enzymes, other molecules involved in inflammatory response, DNA repair, oxidative damage, and et al. Our group explored the molecular markers with potential to predict occurrence and progression of gastric cancer, based on the hypothesis that there might be a similar genetic background that makes some individuals more susceptible to gastric cancer and liable to metastases in cancer progression. In the present study, we are particularly focusing on the single nucleotide polymorphisms (SNPs) of genes encoding microRNAs and immunoglobulin superfamily members.Recently, microRNA-146a (miRNA-146a) and Macrophage migration inhibitor factor (MIF) have been linked to tumorigenesis. SNPs of these genes including Pre-miR-146a C/G and MIF-173G/C have been confirmed to be associated with the expression of the genes and (or) the function of the proteins.However, to our knowledge, there is no study concerning association between these polymorphisms and susceptibility to gastric cancer. Thus, we conducted a hospital-based, case-control study to assess the association between the risk of gastric cancer and the Pre-miR-146a C/G and MIF-173G/C polymorphism by univariate and multivariate analysis.It is important to find the polymorphisms which could be used as the marker for genetic susceptibility to gastric cancer. Identification of genetic factors that are responsible for susceptibility to gastric cancer is indispensable for establishing novel and efficient ways of preventing the disease.PartⅠ: A Study on the Association between Pre-miR-146a C/G Polymorphism and Susceptibility to Gastric CancerTo investigate the association between Pre-miR-146a C/G polymorphism and gastric cancer risk, we conducted a hospital-based case-control study of 304 gastric cancer cases and 304 controls matched on age and gender. The genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found that the genotype frequencies were significantly different (P=0.037) between cases and controls. Compared with the CC homozygotes, the variant genotypes (CG + GG) were associated with a 58% increased risk of gastric cancer (adjusted OR=1.58, 95% CI=1.12-2.22). Further stratification analyses indicated that the increased risk was especially noteworthy in young subjects (age≤58) (adjusted OR=1.76, 95% CI=1.08-2.87), males (adjusted OR=1.53, 95% CI=1.04-2.27) and non-smokers (adjusted OR=1.55, 95% CI=1.06-2.28). We also evaluated the correlations of the variant genotypes with clinicopathologic features of gastric cancer, including tumor differentiation, depth of tumor infiltration, lymph node status and tumor location. However, no statistically significant association was observed. Our results suggest that the Pre-miR-146a C/G polymorphism may be associated with increased risk of gastric cancer. PartⅡ: A Study on the Association between MIF-173G/C Polymorphism and Susceptibility to Gastric CancerMacrophage migration inhibitory factor (MIF) is a T cell-derived cytokine that inhibits the migration of macrophages and play an important pathogenetic role in proinflammatory, enzymatic and hormonal activities. The MIF gene maps to chromosome 22q11.2, and its -173G/C (rs755622) polymorphism has been shown to influence susceptibility to several diseases. To investigate the association between MIF-173G/C polymorphism and gastric cancer risk, we conducted a hospital-based case-control study of 283 gastric cancer cases and 283 controls matched on age and gender. The genotype and allele frequencies were significantly different (P=0.008 and 0.015, respectively) between cases and controls. Further analysis showed that the variant CC genotype had a 3.49-fold increased risk of gastric cancer when compared with GG genotype (adjusted OR=3.49, 95% CI=1.53-7.97). The elevated gastric cancer risk associated with the variant genotypes ( GC + CC) was observed only in male subjects (adjusted OR=1.52, 95% CI=1.03-2.25), but not in females. Further analyses revealed that the variant genotypes (GC+CC) were associated with depth of tumor infiltration. These findings suggest that the MIF-173G/C polymorphism is a genetic predisposing factor for gastric cancer.In summary, we have suggested the polymorphisms of genes involved in different pathogenic pathways in gastric carcinogenesis. Further investigations of the combined effects of polymorphisms within these genes and risk factors may help to clarify the influence of genetic variation in the carcinogenic process.更多还原