It was found that lipin-1 knockdown in the PDX cells of Luminal A (ER+ HER2−), HER2+ and triple-negative breast cancer (TNBC) rendered these cells less metastatic after tail vein injection into the immunocompromised NOD-SCID female mice (Supplementary Fig. 9m–o), indicating that lipin-1 exerts a general pro-malignancy effect among different breast cancer subtypes. The gene discussed is LPIN1; the disease is breast cancer.