To assess the requirement of LPP for breast cancer metastasis in vivo, we stably reduced LPP expression levels in NMuMG-ErbB2 cells and the NIC breast cancer model, which was derived from an ErbB2-expressing mammary tumour that arose in transgenic mice expressing an activated form of ErbB2 (ref. 22; Supplementary Fig. 1). Here, ERBB2 is linked to breast carcinoma.