GRM8 and breast cancer: Figure 4(a) showed the putative binding sites between miR-33a-5p and GRM8. Upregulation of miR-33a-5p with mimic transfection significantly reduced the luciferase activity, whereas this effect was abolished when the binding sites were mutated, as determined by the luciferase gene reporter assay in SK-BR-3 cells (Figure 4(b)). To further confirm the relationship between miR-33a-5p and GRM8, we then performed the western blotting assay. The results showed that miR-33a-5p negatively regulated GRM8 expression in breast cancer HCC1937 and SK-BR-3 cells (Figures 4(c), 4(d)).