| IntroductionTumor is a common kind of somatic inherited disease that severely influences human health. Both the incidence and mortality rate has been rising over the past several decades, and malignant tumor has become the first or second cause of human death. It is showed that tumor is the result of accumulation of multiple gene mutations that mainly occur at three kinds of genes, that is onco-gene, tumor suppressor gene and DNA mismatch repair gene. Among them, most are somatic cell variations, including mutation, amplification, rearrangement, deletion or changes of methylation status.Tumorigenesis is a complex multistep process involving multiple genes. The discovery of oncogene and tumor suppressor gene has deepened human beings understanding of the mechanisms of cell cycle and cell apoptosis as well as the mechanisms of tumorigenesis. It is the basis of the understanding of the molecular mechanism of tumorigenesis, gene diagnosis and gene therapy, to explore different types of tumor - related - genes. In the early 90th, in respond to many problems involved in the investigation of oncogene and tumor suppressor gene, especially the limitation of analysis of single gene, the Human Genome Project ( HGP) , especially Cancer Genome Anatomy Project ( CGAP) have been launched in order to explain the mechanisms of tumorigenesis and find effective methods for intervention and treatment. China has been participating in the clone and localization of tumor - related - genes actively.Gastric cancer is the first cause of death for patients with malignant tumor in China. Every year the number of patients died of gastric cancer amounts to nearly 160 000 and the incidence rate is rising in recent years, it severely influ-ences people's heath. So to clarify the mechanisms involved in the pathogenesis and progression of gastric cancer leading to prevention and treatment is of great importance and urgency.The tumorigenesis of gastric cancer is a multifactor and multistep process, including the activation of multiple oncogenes and inactivation of multiple tumor suppressor genes. It is known that the key issue of gastric cancer is the changes of normal cell genome underling the molecular basis of positive and negative regulation and function disorder for cell growth and development, while the spontaneous , chemical and physical, and viral factors are just the inducible factors. So to clone and identify the gastric cancer related genes, is of great importance.Materials and methodsSamplesSpecimens of gastric cancer and corresponding adjacent normal gastric mu-cosa were obtained from patients who had undergone surgical operations of gastric cancer at the Department of Tumor Surgery of the first affiliated hospital of China Medical University. All samples were confirmed by pathology diagnosis.LOH Analysis of Chromosome 18Select 9 pairs of SIDP marker of chromosome 18 for LOH analysis by combination of LCM - HF - WGA - DHPLC. The disappearance or 50% height reduction of chromatogram peaks of cancer tissue DNA PCR product compared to normal tissue can be identified as LOH. All the positive incidences are confirmed by denaturing polyacrylamide gel electrophoresis and silver stainingMutation Analysis of KLF6 GeneScreen the exon mutations of KLF6 gene in 35 patients with gastric cancer by the combination of PCR and DHPLC. Under the partial denaturing condition, elution profiles that differ from the normal reference DNA, such as shoulders on the leading edge homoduplex peaks or asymmetrical peaks, indicate the presence of variations. PCR products were purified and sequenced, then compared to the GenBank DNA sequence to confirm types of variation.Mutation Analysis of V599E locus at BRAF GeneWe use the traditional RFLP analysis method. After two times PCR, the large amount of purified PCR product containing the 1796th nucleotide of BRAF gene, was digested by Taa I restriction enzyme, then separated by polyacrylam-ide gel eletrophorsis. The second time PCR product that produced 59 bp enzyme - diges...
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