Inhibitory effect of STAT3-decoy-ODN on A549 tumor – bearing nude mice. (A) Human A549 tumor-bearing nude mice were established as described in materials and methods. The mice were intratumorally injected daily with STAT3 decoy ODN (25 μg), scramble ODN (25 μg) or vehicle control (25 μl PBS) for total thirty injections, and the tumor volumes were measured at the indicated day. *p < 0.01 versus PBS treatment control. (B) After daily intratumoral injection of 25 μg STAT3 decoy ODN for thirty times, the xenografts were collected, sectioned and stained for apoptotic cells by TUNEL which performed as described in materials and methods. The brown stain represented the DNA fragmentation of apoptotic cells and the blue showed the nuclei stain with hematoxylin (original magnification ×400). The cumulative results showed the average number of apoptotic cells per High Power Field. **p < 0.001 versus PBS treatment control.