Stromal androgen signaling acts as tumor niches to drive prostatic basal epithelial progenitor-initiated oncogenesis.

The androgen receptor (AR)-signaling pathways are essential for prostate tumorigenesis. Although significant effort has been devoted to directly targeting AR-expressing tumor cells, these therapies failed in most prostate cancer patients. Here, we demonstrate that loss of AR in stromal sonic-hedgehog Gli1-lineage cells diminishes prostate epithelial oncogenesis and tumor development using in vivo assays and mouse models. Single-cell RNA sequencing and other analyses identified a robust increase of insulin-like growth factor (IGF) binding protein 3 expression in AR-deficient stroma through attenuation of AR suppression on Sp1-regulated transcription, which further inhibits IGF1-induced Wnt/ß-catenin activation in adjacent basal epithelial cells and represses their oncogenic growth and tumor development. Epithelial organoids from stromal AR-deficient mice can regain IGF1-induced oncogenic growth. Loss of human prostate tumor basal cell signatures reveals in basal cells of stromal AR-deficient mice. These data demonstrate a distinct mechanism for prostate tumorigenesis and implicate co-targeting stromal and epithelial AR-signaling for prostate cancer.

Aberrant activation of hepatocyte growth factor/MET signaling promotes ß-catenin-mediated prostatic tumorigenesis.

Co-occurrence of aberrant hepatocyte growth factor (HGF)/MET proto-oncogene receptor tyrosine kinase (MET) and Wnt/ß-catenin signaling pathways has been observed in advanced and metastatic prostate cancers. This co-occurrence positively correlates with prostate cancer progression and castration-resistant prostate cancer development. However, the biological consequences of these abnormalities in these disease processes remain largely unknown. Here, we investigated the aberrant activation of HGF/MET and Wnt/ß-catenin cascades in prostate tumorigenesis by using a newly generated mouse model in which both murine Met transgene and stabilized ß-catenin are conditionally co-expressed in prostatic epithelial cells. These compound mice displayed accelerated prostate tumor formation and invasion compared with their littermates that expressed only stabilized ß-catenin. RNA-Seq and quantitative RT-PCR analyses revealed increased expression of genes associated with tumor cell proliferation, progression, and metastasis. Moreover, Wnt signaling pathways were robustly enriched in prostate tumor samples from the compound mice. ChIP-qPCR experiments revealed increased ß-catenin recruitment within the regulatory regions of the Myc gene in tumor cells of the compound mice. Interestingly, the occupancy of MET on the Myc promoter also appeared in the compound mouse tumor samples, implicating a novel role of MET in ß-catenin-mediated transcription. Results from implanting prostate graft tissues derived from the compound mice and controls into HGF-transgenic mice further uncovered that HGF induces prostatic oncogenic transformation and cell growth. These results indicate a role of HGF/MET in ß-catenin-mediated prostate cancer cell growth and progression and implicate a molecular mechanism whereby nuclear MET promotes aberrant Wnt/ß-catenin signaling-mediated prostate tumorigenesis.