Ethical statement
This study was conducted based on the protocols proposed by the commitment of China-Japan Union Hospital. All patients signed written informed consents and had the right to know about the experiment prior to the study.
Subjects
From June 2014 to June 2016, a total of 1021 patients with UBC under surgery in China-Japan Union Hospital were included in our study. All eligible patients were primary UBC patients with complete medical records and shall be excluded if they are complicated with kidney and liver diseases, other urinary system diseases (including renal pelvic carcinoma, ureteral carcinoma, urinary tract carcinoma and renal carcinoma) or other tumors, and if they had unclear pathological diagnosis. All included patients received urinary bladder irrigation chemotherapy at fixed period. The patients with high risk shall receive secondary surgery about 4 to 6 weeks after primary surgery.
Follow up
Follow up was conducted at a regular basis of three month within 2 years of the surgery, including DAPK methylation in urinary sediment, B ultrasound in bladder, detection exfoliated cells in urine and cystoscopy observation. The physician performing each test shall be blind to other detection results. The follow up shall be ended two years after primary surgery or when radical cystectomy is performed in case of invasion UBC.
DAPK methylation in urinary sediment
Urine (50 ml) at the morning of the day of cystoscopy shall be collected and subjected to centrifugation at 2000 rpm /min for 10 min at 4°C. The sediment of the urine shall be washed in PBS for twice and dissolved in 200 ul of pure water, after that the sediment are to be stored in refrigerator at -80°C. Tissue and genomic DNA kit (from Tiangen Bio-technology Ltd., Co, Beijing, China) was applied to extract DNA. Meanwhile, ultraviolet spectrophotometer was used to test the purity and content of the extracted DNA (A260/A280 > 1.8) which shall be preserved in a 1.5 ml centrifuge tube at -20°C. EpiTect Bisulfite Kits (from Qiagen Corporation, Germany) was utilized to modify genomic DNA using hydrosulphite, which shall be stored at -80°C and shall be used within one month. The modified genomic DNA shall be subjected to methylated specific polymerase chain reaction (PCR) and non-methylated specific PCR. Upstream primer for methylation: 5'-GGATAGTCGGATCGAGTTAACGTC-3', downstream primer for methylation: 5'-CCCTCCCAAACGCCGA-3', the product of amplification shall be 98 bp. Upstream primer for non-methylation: 5'-GGAGGATAGTTGGATTGAGTTAATGTT-3', downstream primer for non-methylation: 5'-CAAATCCCTCCCAAACACCAA-3', the product of amplification shall be 106 bp. All primers shall be synthesized by Shanghai Sangon Biotech. The reaction system of PCR (25 μl) includes 2 ul of modified DNA, 0.5 ul of upstream primer, 0.5 ul of downstream primer, 2.5 ul of 10×PCR buffer, 0.5 ul of Taq, 19 ul of ultrapure water. The condition for PCR amplification were pre-denature at 94°C for 5 min, 40 heating cycle of 94°C for 60 s, 54°C for 30 s, 72°C for 30 s, followed by extension at 72°C for 10 min. PCR products were subjected to electrophoresis by 2% sepharose gel and observation under a UV lamp (ultraviolet lamp) for photographing.
B ultrasound in bladder
Patients are told to hold their urine to receive transabdominal B ultrasound in bladder by one appointed associate chief physician in B ultrasound department.
Cytology observation
Cytology observation in urine was carried out at routine and each patient is required to check once every day for constant 3 days. Cells are stained by Pap staining method. Cytology shall be considered as positive if tumor cells were found in urine or negative in case of failing to observe any tumor cells.
Cystoscopy
The cystoscopy was performed by an appointed and experienced physician. Patients shall be in lithotomy position for local anesthesia or intravenous anesthesia. After that, cystoscope was inserted in an angle of 70° to check for tumor recurrence around the bladder. Any unidentified lesions shall be sent for pathological examination by biopsy.
Statistical analysis
SPSS 22.0 software was used for data analysis. Enumeration data shall be expressed as cases. The results of cystoscopy was considered as gold standard to compare the sensitivity, specificity, Youden index (YI), positive predict value, negative predict value of results of B ultrasound in bladder, DAPK methylation examination in urinary sediment and urinary cytology observation. Pairwise x2 and Kappa test was utilized for comparison. Meanwhile, the results of B ultrasound in bladder and DAPK methylation were combined together. Either of the two results being positive shall be considered as positive and both of the two detections being negative shall be considered as negative. P value of less than 0.05 was regarded as statistical significance.