The mRNA levels of both MMP-2 and MMP-14 in human hepatocellular carcinoma (HCC) cell SMMC-7721 were up-regulated by Cu2+ in a concentration dependent manner, whereas the mRNA levels for other tested MMPs (MMP-1, MMP-3 and MMP-9) were not changed when treated with up to 40 μM Cu2+ (Figure 1A and 1B, Supplementary Figure 1). Here, MMP14 is linked to hepatocellular carcinoma.