NR4A1 and breast cancer: We therefore investigated Nodal expression in human breast cancer cell lines that exhibit different characteristics, including triple negative, highly invasive and metastatic MDA-MB-231 and BT-549 cells, triple negative, highly invasive and non-metastatic Hs578t cells, and hormone receptor positive, weakly invasive and non-metastatic MCF-7 cells (Fig. 5C).