IR induces apoptosis in an active Akt-overexpressing model of human DCIS in three-dimensional lrECM. (A) Experimental schema. (B) IR-induced apoptosis was specifically observed in the luminal compartment of MCF10A-Akt structures. (Green = α6-integrin; red = cleaved caspase-3; blue = nuclei) Bar = 50 μm. (C) High content image analysis confirmed an increasing percentage of cells positive for cleaved caspase-3 with increasing IR doses. (n = 200 acini, **, P < 1E-7) (D) Concentric measurements of mean intensity of cleaved caspase-3 showed significantly higher signal in the lumina of irradiated acini, compared to unirradiated controls. Dashed lines indicated edge of the acini. DCIS, ductal carcinoma in situ; IR, ionizing radiation; lrECM, laminin-rich extracellular matrix.