The Characteristic Changes Of Circulating MicroRNA In The Bladder Cancer

BACKGROUND: The incidence of bladder cancer ranks the fourth malignancytumors worldwide, a large number of new cases occur every year. The ratio of men towomen that develop bladder cancer is approximately3:1. In China, the incidence ofbladder cancer stays at the first place in urinary malignancy tumors, more than90%of these cases are transitional cell carcinoma of the bladder with comparatively highrecurrence rate and invasive ability. The incidence and mortality of bladder cancer hasbeen obviously increased late years. Bladder cancer is a complex disease withmulti-reasons, multi-stages and multi-genes. More and more researches indicate thatenvironmental exposures and hereditary factors play important roles in thetumorigenesis, development as well as reoccurrence of bladder cancer. Meanwhile,early diagnosis and treatments could increase survival rate of bladder cancer patients.MicroRNA is a class of evolutionarily conservative endogenous non-coding smallRNA widespread in viruses, plants and animals. Accumulative studies had revealedthat miRNAs participated in human carcinogenesis as either tumor suppressors oroncogenes, which provided a novel tool for the development of bladder cancer. Thus,to screen suitable miRNAs as biomarkers for bladder cancer has important clinicalsignificance. Late researches revealed that the expression of miRNAs in tissues andcells appear to be tumor-related, tissue specificity and stability. Due to the difficultyin recruiting tumor samples, there are limitations in clinical applications of miRNAs in tumor tissues. However, it is comparatively easier in recruiting peripheral bloodsamples, if miRNAs with specific expression in bladder cancer could be tested inblood, which would be vital significance in early diagnosis of bladder cancer. To date,many reports have identified that serum miRNAs expressed abmormally in majorityof tumor patients. In this study, we aimed to find specific expression of serummiRNAs which as a novel biomarker in bladder cancer.METHODS: In the present study, we used the TaqMan Low Density Array to screenmiRNAs in plasma of10matched cases and controls. A two-stage retrospectivecase-control study was designed.175cases identified by histopathology and185cancer-free controls frequency-matched by age and sex were involved in this study.Furthermore, quantitative reverse transcription polymerase chain reaction assays(qRT-PCR) were used to analyze the expression of selected miRNAs, ROC analysisby SPSS17.0software was used to evaluate the value of miRNAs which expresseddifferentially in diagnosis of bladder cancer. On this basis, selected miRNAs werevalidated in tissues of which the targets were predicted by bioinformatics software.RESULTS: We selected miRNAs that had at most35of CTvalue and at least5ofabsolute value of CT. The results showed that the expression of3miRNAs(miR-505、miR-363、miR663b) significantly elevated while the expression of4miRNAs (miR-99a、miR-194、miR-100、miR-497) decreased in plasma of bladdercancer, miR-1reported by many researches was forced to include, which wasdown-regulated in the TLDA analysis. In the other hand, we found the expression ofmiR-16was more stable than U6, thus, we used miR-16as an endogenous control fordata normalization in the validation studies. In the two-stage independent validationstudies, expression of both miR-497and miR-663b was found to be differential inplasma, which was related to the progression of bladder cancer. ROC analysisdescribed that combined analysis of miR-497and miR-663b could contribute to theclinical diagnosis of bladder cancer. In addition, expression of miR-497in tissuesconsisted with that in plasma, while the expression of miR-663b was converse.CONCLUSION: miR-16was used as an endogenous control for data normalizationin the present study. Significant decreased expression of miR-497and increased expression of miR-663b was found in plasma of bladder cancer and both of themiRNAs could distinguish the cases from controls in clinical diagnosis. MiR-497andmiR-663b were supposed to be a promising circulating biomarker in clinicaldiagnosis in of bladder cancer.