ERBB2 and prostate intraepithelial neoplasia: Functional in vitro and in vivo studies have found a relationship between reduced or absent PSAP expression and the elevated phosphorylation of ErbB-2 and PI3K, increased cell growth, increased tumorigenicity, and the development of prostatic intraepithelial neoplasia (PIN) and adenocarcinoma in situ (CIS) (summarized in [5]).