ESR1 and breast cancer: Additionally, co-culturing hyaluronic acid synthase 2 (HAS2) overexpressing, more stem-like MCF10A breast epithelial cells (HAS2-MCF10A) with HUVECs increased their migration through a transwell, while co-culturing estrogen receptor-positive MCF7 breast cancer cells with HUVECs did not show a significant difference in migration [Figs. S2(c) and S2(d)].