Figure 2a shows the schematic diagram of two siRNAs of circ-0006091. The expression of circ-0006091 in the HCC cells was decreased by transfection of si-circ-0006091 (si-circ-0006091#1 and si-circ-0006091#2; Figures 2b and 2c; p < 0.001). In addition, silencing of circ-0006091 decreased the migration (Figures 2d–2g; p < 0.001) and invasion (Figures 2h and 2i; p < 0.001) of the HCC cells. Moreover, the expressions of metastasis-associated proteins MMP-2 and MMP-9 were down-regulated by knockdown of circ-0006091 (Figures 2j and 2k; p < 0.001). The gene discussed is MMP9; the disease is hepatocellular carcinoma.