Comparative analysis of h tid and HER-2/neu expression in breast tumors arising in transgenic Balb/c mice carrying the rat HER-2/neu oncogene revealed inverse correlation between the expression levels of the investigated targets. The detection of mtid was performed as described in the legend to Figure 1. ErbB-2 was detected using the monoclonal anti ErbB-2 antibody (AO85) (cf. Figure 2) cross reacting with the rat molecule. While early tumors, 22 week old, display high tid (A) and low HER-2/neu levels (B), those harvested at 30 weeks are characterized by a low tid expression (C) in contrast to high HER-2/neu (D) levels. (Original magnification: 250×).