Due to halve Her2 expression and with FVB-C57BL/6 mixed background, both Her2t/w/Adamts18−/− mice (10 of 32, ~ 31%) and Her2t/w/Adamts18+/+ mice (2 of 36, ~ 5.6%) showed significantly lower incidence of spontaneous mammary tumors when compared with Her2t/t mice (12 of 12, 100%) (P < 0.001) (Fig. 2A). The gene discussed is ADAMTS18; the disease is breast cancer.