Endorepellin activates tyrosine phosphatases in tumor xenografts in vivo. (A) Tumor volume at day 19 of Lewis lung carcinoma xenografts in C57Bl/6 after PBS or endorepellin (100 μg/mice) treatment on alternate days. Values represent means ± SEMs (n = 8). (B) Fluorescence images of cryosections of Lewis lung carcinoma tumor xenografts treated as indicated and stained for the vascular marker CD31. (C) Quantification of vessels per field. Values represent the mean ± SEM (n = 40 each). (D) Surface plots of the images in panel B showing that the number of vessels is drastically reduced on endorepellin treatment. (E) Analysis of the total tyrosine phosphatase activity in the tumor extracts. Note the absence of a response to endorepellin in tumors from α2β1^−/− mice. (F) Representative immunoblots of immunoprecipitated SHP-1 in Lewis lung carcinoma xenografts from wild-type mice, probed with PY20 for tyrosine phosphorylation or with SHP-1. (G) Quantification of blots as in panel C with the Odyssey image software (LI-COR). Values represent the mean ± SEM (n = 3); **P < .01.