The in vitro cytotoxicity data show the anti-Her2 Cys-ADC, the anti-Her2 position 1 and the anti-Her2 position 2-ADCs had similar cytotoxicity against Her2 expressing HCC-1954 and NCI-N87 cells and were inactive against the MDA-MB-468 cells, which do not express Her2. This evidence concerns the gene ERBB2 and hepatocellular carcinoma.