FOLR1 and breast cancer: The FRα-specific IgE therapeutic candidate, MOv18 IgE [41, 44–47], bound to FRα-expressing IGROV1 ovarian cancer cells in a concentration dependent manner (EC50 = 0.53 μg/ml), but not to non-FRα-expressing A2058 and SKBR3 melanoma and breast cancer cells (Fig. 6a).