HSP90 inhibition impairs the growth of mutant KRAS-dependent tumors in nude mice. (a) Immunoblot of HCT-116 tumors. After tumor formation, mice were injected once with 75 mg per kg body weight PU-H71 or PBS, and tumors were harvested after the indicated times. One mouse per condition and time point was analyzed. (b) Effects of PU-H71 on tumor formation of mutant KRAS-dependent (SW-480, HCT-116) and KRAS WT (Caco-2, Colo-320HSR) colon cancer cell lines in nude mice. Photographs of representative tumors and tumor volumes (error bars represent mean ± SEM of 7–14 tumors from 4–7 mice) are shown. (c) IHC analysis of tumors shown in b. Representative photographs of tissue sections and the proportion of TUNEL-positive cells (error bars represent mean ± SEM of four microscopic fields with 600–800 cells) are shown. NS, not significant. Bar, 125 µm. (d) Immunoblot of tumors shown in b demonstrating STK33 expression in treated mice. Tumors were harvested 24 h after the last injection.