Figure 4

Tet-On system-controlled sTRAIL expression suppresses the growth of MDA-MB-231 xenografts in nude mice. A xenograft MDA-MB-231 animal model was established in nude mice by subcutaneous transplantation. When the tumor size reached to about 50 mm³ (about 7 days post-inoculation), the animals were divided into six groups (n = 6). The rAAV-TRE-TRAIL&rAAV-Tet-On particles of 4 × 10¹¹ Gps were administered through tail vein injection and the animals (day 0) were fed with drinking water with or without doxycycline (1 mg/ml). (A) The tumor growth was observed by measuring the tumor size every four days for total 32 days. The rAAV-TRE-EGFP&rAAV-Tet-On and rAAV-CAG-TRAIL particles were administered as negative and positive control, respectively. The animals were sacrificed and the tumor weights (A) were measured 32 days after virus administration (day 32). Results are presented as the mean ± standard deviation of 6 mice in each group. *P <0.05. (B) The sTRAIL expression in tumor tissue was examined by reverse transcriptional PCR and Western blot assay. β-actin served as protein loading control. WPRE, woodchuck hepatitis virus posttranscriptional regulatory element, representing sTRAIL mRNA expression. NTC: No-Template Control. PTC: Positive Template Control.