Potentiation of the antitumor effects of topotecan by axitinib in an S1-M1-80 cell xenograft model in athymic nude mice. (A) Changes in tumor volume with time. Each point represents the mean ± standard deviation (SD) of tumor volumes from 10 mice in the group. (B) Tumor size. The picture was taken on the 70th d after implantation. (C) Changes in body weight with time after tumor cell inoculation. Each point represents the mean ± SD of body weight from 10 mice in the group. The various treatments were as follows: (a) saline (every 4 d × 9, IP); (b) topotecan (every 4 d × 9, IP 3 mg/kg); (c) axitinib (every 4 d × 9, PO, 25 mg/kg); (d) topotecan (every 4 d × 9, IP, 3 mg/kg) and axitinib (every 4 d × 9, PO, 25 mg/kg) (axitinib was given 1 h before topotecan administration). The whole administration process was divided into three cycles with a 10-d drug-free recovery period between every two cycles.