SMAD4 and neoplasm: To determine whether Smad4 levels would also increase in a Wnt/ β-catenin-driven tumor model using the Nkx3.1CreERT model (Nkx3.1CreERTApcflox, referred to as ApccKO [5]), we performed Smad4 immunohistochemistry (IHC) and quantitative reverse transcriptase PCR (qPCR) on Cre-negative (Apcflox) and Cre-positive (ApccKO) prostate tissue.