To assess the role of the tested miRNAs in the regulation of NKG2DL expression, BCap37 cells were transfected with control miRNAs (Ctrl), mimics or inhibitors of the tested miRNAs (Supplementary Figure 2a). Mimics of miR-20a, miR-20b, miR-93 and miR-106b decreased MICA/B and ULBP2 protein expression, whereas inhibitors of the tested miRNAs increased their expression in BCap37 cells (Figure 2e and f). However, the tested miRNAs showed limited influence on the expression of ULBP1/3. Among the four tested miRNAs, miR-20a showed the strongest influence on NKG2DL regulation in BCap37 cells (rMFI, mean±S.D., mimic versus Ctrl 47.2±5.7%, inhibitor versus Ctrl 202.0±10.1% for MICA/B, mimic versus Ctrl 76.1±2.3%, inhibitor versus Ctrl 136.4±3.3% for ULBP2, Figure 2f). In addition, these miRNA-mediated downregulations of NKG2DLs were typically associated with a decrease in related mRNA transcripts (Figure 2g). This finding indicated that the miRNA-mediated downregulation of NKG2DL expression was partially caused by enhancing degradation of related mRNA transcripts. We confirmed these results by assessing the effects of miR-20a and miR-93 on the BC cell line MDA-MB-231 and the normal breast cell line HBL-100 (Supplementary Figure 2b and c). Taken together, the tested miRNAs specifically downregulated MICA/B and ULBP2 expression in both BC and normal breast cell lines.