To create the HuHER2 cell line that have a metastatic phenotype and can lead spontaneous metastasis ultimately to various distant organs, we established a cell line (HuHER2-TP) by serially transplanting a spontaneously developed mammary tumor into the mammary fat pad and interestingly, found that HER2 expression was upregulated in HuHER2-TP cells compared to HuHER2-6 and HuHER2-L2 (Figure 6A, 6B and Supplementary Figure 6). The gene discussed is ERBB2; the disease is breast cancer.