ID4 and benign prostatic hyperplasia: Collective results suggested that Id4-/- knockout (KO) mice display complex phenotypes that resemble or mimic Pten and Nkx3.1 combined KO in many respects but with no clear cancerous phenotype or prostatic hyperplasia observed in Nkx3.1+/-;Pten+/- [10] or Nkx3.1-/- [11] mice respectively.