Expression Of DNA Polymerase β In Esophageal Cancer Tissues And Its Significance

Living cells face the tremendous task of maintaining an intact genome during their life span. This is necessary for cells to function in a complex environment, divide at the required time and die when appropriate. DNA synthesis is therefore necessary to duplicate the genome before cell division commences, which is also necessary during DNA repair. Generally, DNA synthesis is carried out by enzymes called DNA polymerases. The number of DNA polymerases has increased to 14 since the initial discovery of DNA polymerase a . Consequently, the cells seem to have evolved a well-defined set of DNA polymerases, each one uniquely adapted for a specific pathway. DNA polymerase a is required for the initiation of DNA replication and the priming of Okazaki fragments during elongation. DNA polymerase 8 ,which functions as a dimmer in both leading and lagging strand synthesis, is required for mismatch repair(MMR) and nucleotide excision repair(NER), as well as long-patch base excision repair(BER). DNA polymerase is thoughtto e restricted to the Okazaki fragment maturation function. According to the current consensus, DNA polymerase 逷 (pol ? is the BER polymerase that is expressed at a constant low level throughout the cell cycle and is inducible by some genotoxic treatments. Features that distinguish pol ?from other cellular polymerases are the lack of associated proofreading activity, its low fidelity in replicating DNA in vitro, and its poor abilityto discriminate nucleotides at the level of binding. Furthermore, pol 3 , found in some human tumors, could confer an increase in spontaneous mutagenesis and result in a highly mutagenic tolerance phenotype. So, our study is to study the expression of pol 3 in esophageal cancer tissues and investigate the role of pol 3 gene in the carcinogenesis and development of esophageal cancer.Methods35 pairs of esophageal cancer and corresponding adjacent tissues were examined for expression levels of pol 3 gene by semi-quantitative RT-PCR.Results1. 1.30 cases of esophageal cancer were determined to be overexpressed , 7 of which were early esophageal cancer , 23 of which were infiltrative cancer, Only 5 of normal esophageal tissues were determined to be overexpression of pol 3 gene. The expression level of pol 3 gene was higher in esophageal cancer than that in normal esophageal tissue ,but there was no difference between early esophageal cancer and infiltrative cancer tissues in the expression levels of pol 3 gene2. There were 31 cases of squamous cell cancer ,22 of which were highly expressed. 3 of 4 adenoma cancer tissues were found excess pol 3 . There was no difference between squamous cell cancer and adenoma cancer tissues in the expression levels of pol 3 gene.3. 25 patients whose cancer tissues were determined to be overexpressed, 9 of which were from 37-49 years old, 16 of which were more than 50 years old. Statistically significant differences were observed between the two groups.4. 25 patients whose cancer tissues were determined to be overexpressed, 17 of which were male ,8 of which were female . There were no difference between the two groups in the expression levels of pol 3 gene.Conclusion1. The results suggest that the overexpression of pol 3 gene is well related with the carcinogenesis and development of cancer.2. The overexpression is an early signal of esophageal cancer, which suggests the overexpression could be a early diagnostic standard.3. The expression of pol 3 gene may be related to the age of patient , but notrelated to clinical stage . the sex of patient and different histological types of esophageal cancer.