Studies On DNA Polymerase β Gene Mutation In Human Cervical Cancer

Malignant transformation is a multistage, progressive process. Present studies indicate that multiple molecular changes, such as those found in tumor suppressor genes and proto-oncogenes, are involved in carcinogenesis. Cervical cancer is one of the most malignant diseases and is a serious threat to women' s health. The causes of cervical cancer are complicated because many gene mutations might contribute to its development. Furthermore, the molecular mechanisms that cause mutation accumulation and development ofcarcinomas are not yet clear. DNA polymerase is a repair enzyme, known to be involved in mammalian systems. .A close relationship has been established between the presence of defective DNA polymerase J5 and carcinogenesis. In order to clarify the molecular mechanism of human Cervical cancer , we collected fresh specimens from 12 normal cervixes , 18 CIN (cervical intraepithelial noeplasia)and 34 CC and examined the mutation of DNA polymerase P gene using polymerase chain reaction , single stand conformation polymorphism analysis of RNA, and sequencing analysis. Of the CC patients, there were 11 in stage I , 12 in stage 11,9 in stage 111,2 in stage IV according to the guidelines of the InternationalFederation of Gynecology and Obstetric (FIGO). According to their histological grading, the 34 cases of CC were divided into three groups: 9 cases of grade I , 14 cases of grade II, 11 cases of grade III. Of the CC patients, 10 accompanied with tumor diffusion, 14 accompanied with lymph node metastasis. Results:1. DNA polymerase 0 mutations were detected iin the tissues of CIN and CC. In normal cervix, CIN and CC, the mutated rates were0/12, 2/18, 13/34 respectively. The mutated rates in CC were significantly higher than those in CIN ,and the difference was significant (P<0. 05)2. The mutation of DNA polymerase ?has related with the histological differentiation of the CC. The mutated rates in low differentiation cancer were significantly higher than those in moderate and high ones, and the difference was significant (/'<0. 05) .3. The mutated rates of DNA polymerase in early stage ( 1 -II) and advanced stage (III-IV) were 30. 43%, 54. 55% respectively. This was not a significant difference. ( P>0. 05)4. No significant relationship was found between CC diffusion and no CC diffusion, lymph node metastasis and no lymph node metastasis (P >0.05).5. The sequencing of the PCR product showed an A to G at nucleotide 660, which resulted in a substitution of the amino acid from Arginine to Glycin at cordon 182. This impaired the catalytic activity of DNA polymerase 3 . As a result ,this may lead to observed accumulationof mutations in tumor cells. Conclusion:1. There were DNA polymerase 0 mutations in the tissues of CIN and CC and the mutated rates in CC were significantly higher than those in CIN.2. The mutation of DNA polymerase 0 has no correlation to clinical stage, tumor diffusion and lymph node metastasis of the CC, but it does relate to the histological differentiation of CC.3. . The sequencing of the PCR product showed an A to G at nucleotide 660, which resulted in a substitution of the amino acid from Arginine to Glycine at codon 182. This impaired the catalytic activity of DNA polymerase 0. .As a result, this may lead to observed accumulation of mutations in tumor cells.