Androgen Signaling Is a Confounding Factor for β-catenin-mediated Prostate Tumorigenesis

Emerging evidence has demonstrated the critical roles for both androgen and Wnt pathways in prostate tumorigenesis. A recent integrative genomic analysis of human prostate cancers has revealed a unique enrichment of androgen and Wnt signaling in early onset prostate cancers, implying their clinical significance in the disease. Additionally, interaction between the androgen receptor (AR) and β-catenin has long been detected in prostate cancer cells. However, the consequence of this interaction in prostate tumorigenesis is still unknown. Because mutations in adenomatous polyposis coli (APC), β-catenin, and other components of the destruction-complex are generally rare in prostate cancers, other mechanisms of aberrant Wnt signaling activation have been speculated. To address these critical questions, we developed Ctnnb1(L(ex3)/+)/R26hAR(L/+):PB-Cre4 mice, in which transgenic AR and stabilized β-catenin are co-expressed in prostatic epithelial cells. We observed accelerated tumor development, aggressive tumor invasion, and a decreased survival rate in Ctnnb1(L(ex3)/+)/R26hAR(L/+):PB-Cre4 compound mice compared to age-matched Ctnnb1(L(ex3)/+):PB-Cre4 littermate controls, which only have stabilized β-catenin expression in the prostate. Castration of the above transgenic mice resulted in significant tumor regression, implying an essential role of androgen signaling in tumor growth and maintenance. Implantation of the prostatic epithelial cells isolated from the transgenic mice regenerated PIN and prostatic adenocarcinoma lesions. Microarray analyses of transcriptional profiles showed more robust enrichment of known tumor and metastasis promoting genes: Spp1, Egr1, c-Myc, Sp5, and Sp6 genes in samples isolated from Ctnnb1(L(ex3)/+)/R26hAR(L/+):PB-Cre4 compound mice than those from Ctnnb1(L(ex3)/+):PB-Cre4 and R26hAR(L/+):PB-Cre4 littermate controls. Together, these data demonstrate a confounding role of androgen signaling in β-catenin initiated oncogenic transformation in prostate tumorigenesis.