Functional analysis of serum microRNAs miR-21 and miR-106a in renal cell carcinoma

OBJECTIVE: microRNAs (miRNAs) plays an important role in tumor development and progression and act as oncogenes or tumor suppressor genes in the carcinogenesis process. miRNA is stable in serum, and recent studies have demonstrated the feasibility of using circulating miRNA as biomarkers in cancer patients. However, currently, no serum biomarkers for the early diagnosis and prognosis of renal cell carcinoma (RCC) have been reported. Therefore, a new molecular marker for early diagnosis and evaluation of recurrence after surgery is required. Our purpose was to identify miRNA signatures that could distinguish the serum of RCC patients from matched healthy controls and validate identified miRNAs as potential biomarkers for RCC. METHOD: Serum samples from 30 RCC patients were collected before and 1 month after surgery. 30 cancer-free blood donor volunteers with no history of any cancer were recruited from the same institute. miR-21 and miR-106a expression levels were determined by real-time PCR. RESULT: The serum miR-21 level was significantly higher in RCC patients (median, 8.34) than in healthy control individuals (median, 0.70; p = 0.001). A month after surgery, serum miR-21 levels (median, 0.69) were significantly reduced (p = 0.032). The serum miR-106a level was higher in RCC patients (median, 8.99) compared with controls (median, 0.96; p = 0.000), while miR-106a levels (median, 1.01) were reduced a month after surgery (p = 0.028). The expression level of miR-21 and miR-106 a in RCC patients increased significantly, while miR-21 and miR-106a decreased after surgery. This outcome suggests that serum miR-21 and miR-106a expression level was closely related with kidney cancer tissue. CONCLUSION: We conclude that serum miR-21 and miR106a are expected to be molecular markers for RCC.