ERBB2 and neoplasm: At the time of these studies, we interpreted the observed losses of HER-2 expression to be a special vaccine-induced form of the “immunoediting” phenomenon described previously by others [11, 12]; HER-2-specific CTL were presumably destroying the HER-2-overexpressing cell population within heterogeneous tumor masses and thus selecting for a residuum of disease that was HER-2low/neg and thus poor targets for continued destruction by the CTL.