Administration of lipidoid-formulated si156 results in a reduction in volume of established tumors. (A) HepG2. (B) SKOV3. Error bars denote SEM (n = 4). The size difference between the treatment and control groups is significant by two-tailed Student’s t test at day 20. P = 0.0005 and P = 0.0133, respectively. (C and D) TUNEL staining confirms induction of apoptosis in vivo. Sections of SKOV3 tumors from mice treated with lipidoid-formulated siControl (C) or si156 (D) are shown. Blue, DAPI; red, TUNEL. Bars, 250 µm.