PTEN and prostate intraepithelial neoplasia: Also, transgenic mice overexpressing ETV1 in the prostate presented with prostatic intraepithelial neoplasia (PIN), yet deficiency of the tumor suppressor PTEN, which is commonly observed in human prostate tumors, was additionally required for the development of prostate adenocarcinomas in ETV1 transgenic mice2,10,11,17.