A). Effect of p53 knockdown on the response of 786-0 xenografts to sunitinib treatment. The expression of a p53 shRNA markedly reduced the antitumor effect of sunitinib. Each growth curve represents the mean tumor volume from 6 mice in each treatment group. B). p53 knockdown blocked the deposition of endostatin and arresten otherwise induced by sunitinib treatment. Lysates were from tumors on day 28 after the start of treatment. Lanes represent data from individual tumors for each treatment group. Blots were probed for p53, p21, endostatin, arresten and vinculin.