At 13 weeks of age, there was no significant difference in the development of breast cancer between wild-type (WT) and Pgrmc1 knockout (KO) mice; however, Pgrmc1 KO mice had a significantly longer survival period and a significantly lower degree of lung metastasis compared with WT mice, thus suggesting the possible role of Pgrmc1 in the metastasis of breast cancer and its potential value as a therapeutic target. The gene discussed is PGRMC1; the disease is breast cancer.