shRNA gene therapy inhibits growth of tumors. LS-174T tumors were established. When the tumors reached around 100 mm3 (indicated by a vertical arrow), they were injected with control vector, Del1-shRNA, VEGF-shRNA, or a combination of Del1-shRNA plus VEGF-shRNA, and their sizes (mm3) were monitored and recorded. The untreated tumors also served as controls. A significant difference in tumor volumes from control is denoted by "*", and a highly significant difference by "†". "‡" Indicates significant difference from Del1-shRNA or VEGF-shRNA monotherapies.