We systematically verified the operation, usefulness, and specificity of our miRDREL system with miRNA-targeting cis-elements, including established oncomiRs [miR-21, let-7a, miR-7, miR-122, and miR-210 (data not shown)] and natural miRNA-targeting sites, such as those harbored in mRNAs encoding CDC34, PPP1R3B, SATB1, and GYS1 in various cancer cell lines and in animal tumor models. This evidence concerns the gene CDC34 and cancer.