The Expression And Functional Study Of Dicer In Clear Cell Renal Cell Carcinoma

Objective: Although multiple studies have shown that the deregulation of microRNA(miRNA) biogenesis machinery is involved in various human malignancies, this rolehas not been investigated in clear cell renal cell carcinoma (ccRCC). This study aims todetermine the expression of Dicer, a key enzyme responsible for biogenesis of miRNA,and its biological roles in ccRCC, investigating its correlation with tumorigenesis andmetastasis of ccRCC.Materials and Methods: The expression of Dicer in mRNA and protein levels weredetected in human kidney tubule epithelial cell line (HKC), non-metastatic786-OccRCC cell line, and metastatic ACHN ccRCC cell line, as well as in42cases ofccRCC surgical specimens including14cases with distant metastasis and theircorresponding adjacent normal renal tissues, by real-time quantitative polymerase chainreaction and western blot, respectively. Dicer expression levels in specimens were alsomeasured by immunohistochemical staining. Liposome-mediated method was used totransfect siRNA sequence targeting Dicer and mock sequence as control into786-O andACHN cells. The knockdown efficiency of Dicer in cell lines after transfection wasdetected by western blot. The effects of Dicer on cell growth rate and cell cycles weredetected by MTS assay and flow cytometric analyses, respectively, and the effects ofDicer on cell migration and cell invasion were detected by Boyden chamber Transwellassay.Results: Compared with HKC, Dicer expression levels were significantlydownregulated in786-O and ACHN ccRCC cell lines, with the metastatic ACHNccRCC cell line even lower (all p<0.05). Meanwhile, Dicer expression levels weresignificantly downregulated in ccRCC surgical specimens compared with adjacentnormal renal tissues, with the metastatic ones further reduced (all p<0.05), and DicermRNA levels were significantly correlated with overall TNM stage of ccRCC (p<0.05).In functional studies of786-O and ACHN cells, MTS assay showed that the growth rateof the Dicer-siRNA group was significantly promoted, flow cytometric analyses showedthat the Dicer-siRNA group increased in the S phase accompanied by a reduction in theG0/G1phase，and Transwell assay showed that the number of migrating cells and invading cells were significantly increased in Dicer-siRNA group (all p<0.05),compared with the untransfected and mock-siRNA groups.Conclusions: Reduced expression of Dicer may play a role in the tumorigenesis ofccRCC, and further decline may be associated with distant metastasis of ccRCC.