Apoptosis induction by downregulation of survivin in nude mice. (A) P: pSIREN-S; Representative expressions of survivin (a and b), bcl-2 (c and d), bax (e and f) and caspase-3 (g and h) protein were shown. Positive expressions in serial sections were shown in representative photomicrographs (positive stain was brown). Magnification = 400×. (B) The scores were classified as 1 to 5, based on the intensity of staining and the percent of positive expression cells. The results indicated that inhibition of survivin by administration of shRNA plasmid by UTMD technique resulted in apoptosis induction by downregulating bcl-2 and survivin expression, and upregulating the activity of caspases-3 and bax. Furthermore, the combination of UTMD and PEI could lead to the most significant gene downregulation and cell apoptosis. *P < 0.001 vs control, †P < 0.001 vs P+UTMD group.