To explore the mechanism of miR-21 involved in the development of renal cell carcinoma.

Cell proliferation and apoptosis were measured after repression of miR-21 expression by antisense oligonucleotides. miR-21 targets were scanned using target prediction programs. After reduction of miR-21, Fas ligand and metalloproteinase inhibitor 3 (TIMP3) expression and luciferase activity were detected by Western blot and luciferase reporter assay. The effect of TIMP3 on miR-21-induced cell survival was determined by transfection with TIMP3 lacking 3′ untranslated region and miR-21.

The reduction of miR-21 by antisense oligonucleotides inhibited cell proliferation and induced cell apoptosis by activation of caspase pathway in renal cell carcinoma cells. Moreover, bioinformatics analysis revealed that miR-21 has the potential to regulate multiple apoptosis-related genes. The reduction of miR-21 inhibited Fas ligand and TIMP3 expression by targeting the binding site within the 3′ untranslated region. Finally, the introduction of TIMP3 cDNA without 3′ untranslated region abrogated miR-21-induced cell survival.

Together, these findings indicate that miR-21 plays a key role in regulating cell apoptosis by targeting multiple genes in renal cell carcinoma.