Figure 2.

Increasing tumor vascularization facilitates SNALP-mediated siRNA delivery. (a) The ability of SNALP liposome to deliver the TetR siRNA (siTetR) or the control siRNA (NTC) into TetR-ODC-Luc or TetR-ODC-Luc/VEGF cells in vitro was determined. Different amounts of SNALP liposomes containing siTetR or NTC were incubated with the TetR-ODC-Luc or TetR-ODC-Luc/VEGF cells for 72 h, and luciferase activity in cells was determined afterwards. The increase of luciferase activity indicates successful siRNA delivery. The x axis represents the dose of SNALP liposome in Log(nM of final siRNA concentration). SNALP-mediated delivery of TetR siRNA induced a similar dose–response curve in the TetR-ODC-Luc and the TetR-ODC-Luc/VEGF cells, indicating that high level of VEGF expression does not change the intrinsic response of the positive-readout system to siRNA delivery. (b) Representative tumor sections (hematoxylin and eosin staining) of the regular TetR-ODC-Luc tumors and the VEGF-expressing TetR-ODC-Luc/VEGF tumors. (c) The TetR-ODC-Luc or TetR-ODC-Luc/VEGF cells were used to create liver tumors via intrahepatic inoculation in scid mice. Mice were imaged on day 0, fed with regular water (Dox−) or doxycycline-containing water (Dox+) for 4 days, and reimaged on day 4. (d) Mice that bear TetR-ODC-Luc- or TetR-ODC-Luc/VEGF-derived liver tumors were administrated with SNALP liposomes containing the control siRNA (NTC) or the TetR siRNA (siTetR) via intravenous injection (2.5 mg siRNA kg⁻¹) on day 1 and day 2. Mice were imaged 1 day before the start of dosing (day 0) and 2 days after the last dose (day 4). For both (c, d) N=5 for each treatment group. Each bar in the graph represents the average signal ratio±s.e.m. for each group.