| Summary: | 碩士 === 高雄醫學大學 === 醫學研究所碩士班 === 92 === Mutation of the tumor suppressor gene p53 has been reported occurring prevalently in a wide range of human tumors including urothelial tumor and colorectal cancer. Early detection of a mutated p53 gene is thought to provide useful information for the clinical treatment of urothelial tumor. To identify the role of the p53 gene in transitional cell carcinoma of urinary tract, we design this study.
In this study, a rapid screening test for mutation of the p53 gene by Polymerase Chain Reaction / Single-Strand Conformation Polymorphism (PCR/SSCP) and sequencing analysis in transitional cell carcinoma of urinary tract was performed.The genomic DNA of the specimens were purified using DNeasyTM Tissue Kit. Primer sets were designed to amplify fragments within the exon 4, 5, 6, 7, and 8 of p53 gene. SSCP analysis was carried out on a Genephor Electrophoresis Unit and visualized by silver staining. Sequencing was done on original PCR products of p53 in all patients. The statistical analysis adopts commercial computer software SPSS 10.0. Chi-square test and t-test are adopted to describe the relationship between p53 gene mutation and tumor stage, tumor grade, sex and age. P≤0.05 is defined as statistical significance.
From March 1992 to July of 2003, 94 surgical specimens collected from Kaohsiung Medical University hospital. A total of seventy-five patients were enrolled in this study finally. Fifty-four patients were male and 21 patients were female. The mean age was 66.85 years old. Fifty-eight patients had bladder cancer, 8 patients had ureteral cancer and 9 patients had renal pelvis cancer. At the time of pathological diagnosis, 37 tumors were classified as low grade and 38 tumors as high grade. As for tumor stage, ≤pT1 stages were noted in 29 cases and ≥pT2 were 46. Totally, 47 of 75 patients (62.7%) have p53 gene mutation. Moreover, 33 of 46 (71.7%) patients were found to have genetic alterations of p53 in invasive tumors. The analyzed results indicate that tumor grade, age and gender are not the important risk factors associated with p53 gene mutation (p>0.05). Conversely, tumors with invasive stage showed statistical significance with p53 gene mutation (p<0.05). Exon 4 presented with multiple mutation sites is the most common mutation gene among exon 4 -8 of p53 genes which was noted in 20/75(26.7%) patients. Besides, exon 5 mutation was noted in 5/75(6.7%) patients, exon 6 mutation was noted in 12/75(16%) patients, exon 7 mutation was noted in 17/75(22.7%) patients and exon 8 mutation was noted in 9/75(12%) patients. All of these exons also include multiple mutation sites. In addition, 14/75 patients with more than one exon mutation of p53 genes were also found in this study.
When talking about the exon 4 mutation of p53 genes, 15 patients (75%) with invasive tumor , 5 patients (25%) with superficial tumor , 9 patients(45%) with high grade tumor and 11 patients(55%) with low grade tumor were noted. Among 20 patients with exon 4 gene mutation, 6 patients coexisted with codon 72 polymorphism, but the others did not. Twenty patients with codon 72 normal polymorphism were found in this study. However, only 6/20 codon 72 polymorphism presented with other codon change of exon 4 and the others (14/20) existed independently. Among 20 codon 72 polymorphisms, 16 patients (80%) with invasive tumor and 14 patients (70%) with high grade tumor were found. Both of these two findings reached statistical significance.
In conclusion, we found that 62.7% of transitional cell carcinoma patients had p53 mutation. Invasive tumors are easy to be found to have p53 gene mutation. The p53 gene mutation may be used as a marker of transitional cell carcinoma. The simple analysis of p53 gene using PCR/SSCP is suitable for screening p53 abnormalities in transitional cell carcinoma at present. Besides, the relationship among multiple mutation sites existed in exon 4-8, highest exon 4 mutation rates, high codon 72 polymorphism and cancer risk need for further investigation.
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