Compared with SG400-EGFP, infection with SG400-E2F1 and SG400-E2F/IL-15 both inhibited MDA-MB-231 cell growth in a dose-dependent manner (Figure 2C); SG400-E2F/IL-15 exhibited a stronger inhibitive effect than SG400-E2F1 (P=0.0000). This evidence concerns the gene E2F1 and infection.