Up-regulation of p21 gene expression enhanced cisplatin cytotoxicity in vivo. (A and B) Aliquots of 1.0 × 106 A549 cells were suspended in 1:1 PBS subcutaneously inoculated into the right flank of each mouse. When palpable tumors were observed, mice were stochastically assigned to 5 groups (n = 5). Mice were received PBS, scramble dsRNA, dsP21-322, cisplatin, or mixture of dsP21-322 and cisplatin intratumorally every 3 days for three weeks. During three weeks treatment, tumor volume was monitored and tumor growth was curved. (C) Expressions of p21 in tumor tissues treated with dsP21-322 were assessed by immunohistochemical staining.