Tumor heterogeneity impacts response to anti-neu antibody therapy. WT BALB/c mice (n = 6-8/group) were inoculated s.c. with a mixture of 5 × 105 TUBO and TUBO-P2J cells. The percentage of TUBO-P2J cells was either 0.1% or 0.01%. A) Immunochemistry staining of mixed tumors for Neu. B-C) Mice were treated i.p. with 200 μg anti-neu (α-neu) antibody or isotype control (Ctrl) on day 10, and 100 μg on day 13, 16, and 19. Tumors were resected on day 21. The therapeutic effects of anti-neu antibody were evaluated by measuring primary tumor growth (B) and overall survival (C). The sizes of tumor were measured twice a week. *P < 0.05, ** P <0.01 and ***P < 0.001 versus control group. One of two experiments is shown.