By western blot, TNBC cell lines had higher expression of NPC1 relative to ER+ breast cancer cell lines (Figure 1H; Supplementary Figure S2B), and immunohistochemistry demonstrated NPC1 expression in both primary tumor and lung metastasis in an MMTV-driven mouse model of breast cancer (Supplementary Figure S2C). Here, NPC1 is linked to breast carcinoma.