Moreover, in order to further evaluate the function of Tac2-N in vivo, we examined the liver metastasis of nude mice using H&E staining and found that Tac2-N overexpression dramatically increased the number of metastatic foci in the liver of nude mice (Additional file 1: Figure S1a and S1b) and above results were further confirmed by detecting human-specific β2-MG (beta-2-microglobulin) levels to quantify metastatic human cancer cells (Additional file 1: Figure S1c and S1d). This evidence concerns the gene B2M and cancer.