Downregulated miR-646 in clear cell renal carcinoma correlated with tumour metastasis by targeting the nin one binding protein (NOB1)

Background: Nin one binding protein (NOB1) was identified as a potential oncogene in human glioma and miR-646 plays an important role in human growth and development. However, the underlying molecular mechanisms of NOB1 in tumorigenicity and its correlation with miR-646 in renal cell carcinoma (RCC) have not been investigated. Methods: We performed bioinformatic analysis to explore miRNA targeting NOB1. The expression of NOB1 and miR-646 from 100 cases of clear cell RCC (ccRCC) and 30 cases of adjacent non-tumour tissues were detected by quantitative real-time PCR. The expression of miR-646 was correlated with NOB1 expression, tumour features and patient metastasis-free survival. The effect of overexpression of mir-646 on renal cancer cell proliferation was detected by colony formation in soft agar. Using a xenograft tumour model, we observed the in vivo tumorigenesis effect of miR-646 and NOB1. Results: miR-646 negatively regulated NOB1 and inhibited the proliferation and migration of renal cancer cells. There was a significant upregulation of NOB1 in ccRCC and it was further increased in metastatic cases, while miR-646 was downregulated in tumour tissues and further decreased in metastatic ccRCC. Additionally, expression of miR-646 was inversely correlated with the expression of NOB1. The downregulation of miR-646 also indicated a higher probability of developing metastasis. Most importantly, miR-646 expression was an independent predictor of ccRCC metastasis by the univariate analysis and binary logistic regression model (both P<0.05). Colony formation in soft agar and xenograft tumour model suggested that miR-646 and NOB1 are required for tumorigenesis in vitro and in vivo. Furthermore, suppression of NOB1 increased the phosphorylation of several proteins in MAPK pathway. Conclusions: Downregulated miR-646 in ccRCC was associated with tumour metastasis through MAPK pathway by targeting NOB1. miR-646 and NOB1 may play an important role in the development of ccRCC.