We next confirmed the specific interaction between the tested miRNAs and the mRNA of MICA/B. All tested miRNA have the same predicted binding sites in MICA or MICB mRNA. We used miR-20a and miR-20b as models. We generated four firefly luciferase reporter vectors: two containing the wild-type MICA or MICB 3'-UTR and the other two containing the MICA or MICB 3'-UTR with a mutated binding site (Figure 3a). Transfecting BCap37 cells with wild-type MICA or MICB in combination with the miR-20a or miR-20b mimic revealed a clear downregulation of luciferase activity compared with the control miRNA group (Ctrl). In contrast, the miR-20a or miR-20b mimic did not effectively reduce the luciferase activity of the MICA or MICB construct with a mutated binding site (Figure 3b). These results indicated that miR-20a and miR-20b directly targeted MICA/B mRNA at the predicted 3'-UTR-binding sites.