| In the post-genome era, an important task facing researchers is to explore the impact of numerous genetic variations on life activities. In particular, the relationship between genetic variations and cancer has become a research hot spot. Progress in this research field will provide valuable clues for understanding the molecular basis of cancer occurrence and progression, and promote the development of personalized cancer diagnosis and treatment.Single nucleotide polymorphism (abbreviated SNP) is the most common type of genetic variation in individuals, and may contribute to individual cancer risk. In recent years, a good many studies of the relationship between SNPs and the risk of common cancers have emerged. However, due to the relatively small sample size, the results of most studies remain inconclusive. Meta-analysis is able to combine case-control data from different studies, and thus better able to assess the impact of SNPs on cancer risk.In order to explore the relationship between SNPs and cancer susceptibility, we carried out a series of meta-analyses in several cancers, and found that TNFα-308G/A polymorphism was significantly related with breast cancer risk, TGFB1-509C/T polymorphism as well as MDM2309T/G polymorphism were both significantly associated with colorectal cancer risk, and XRCC3T241M polymorphism might influence gastric cancer risk oppositely in Asians and Caucasians.Through those meta-analyses, we also noted that an information platform for the contribution of genetic variations to cancer developed to address time constraints of meta-analysis and meanwhile add information on the living environment and lifestyle of samples, would better meet the growing demand of researchers and clinicians for cancer genetic data. Therefore, in the second part of this thesis, we developed such a platform with hepatocellular carcinoma (abbreviated HCC) as the research object. We collected for the first time detailed information of all the genetic variations that have been investigated for their association with HCC, and constructed dbHCCvar online database-an information platform for the contribution of genetic variations to hepatocellular carcinoma. In the process of database construction, first we searched PubMed for related papers. The initial search results were then further screened and eligible publications were collected. Major research data from each eligible study were extracted and recorded in dbHCCvar. In addition, we also added several user-oriented designs in dbHCCvar. First, dbHCCvar provides for its users, a powerful search function, as well as a browse and download service for the entire dataset in this database. Second, information about additional factors (cirrhosis, hepatitis B virus (abbreviated HBV), hepatitis C virus (abbreviated HCV), aflatoxin, alcohol, and smoking) were also collected and recorded for each entry of dbHCCvar, making systematic analysis of multiple HCC-related factors more convenient. In addition, we established two different data update approaches in dbHCCvar, so as to add newly reported data in a timely manner. To date, there are820entries in dbHCCvar. These entries include information for636unique human genetic variations, according to235publications. dbHCCvar is free for all visitors at http://GenetMed.fudan.edu.cn/dbHCCvar.In conclusion, we explored the impact of SNPs on common cancers through a series of meta-analyses, and on this basis constructed for the first time an information platform for the contribution of genetic variations to hepatocellular carcinoma, which laid a solid methodological foundation for the development of similar platforms for other types of cancer. Our study will help scientists and clinicians obtain more comprehensive and systematic cancer genetic data, and then better understand the relationship between genetic variations and cancer, thus ultimately promoting the search and identification of new cancer genetic markers as well as the development of cancer prevention, diagnose and individualized treatment.
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