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

Co-occurrence of aberrant hepatocyte growth factor (HGF)/MET proto-oncogene receptor tyrosine kinase (MET) and Wnt/β-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/β-catenin cascades in prostate tumorigenesis by using a newly generated mouse model in which both murine Met transgene and stabilized β-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 β-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 β-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 β-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 β-catenin-mediated prostate cancer cell growth and progression and implicate a molecular mechanism whereby nuclear MET promotes aberrant Wnt/β-catenin signaling-mediated prostate tumorigenesis.