Ascertaining the biochemical basis of indirect negative regulation by ErbB2 is also likely to be worthwhile, since our data imply that the high responsiveness of HER2amp tumors to anti-receptor therapy may be a function not only of the addiction to the ErbB2 oncogene, but also of the suppression of other signaling pathways that might function as resistance mechanisms in other tumor types. Here, ERBB2 is linked to neoplasm.