Bone metastasis of prostate cancer can be therapeutically targeted at the TBX2-WNT signaling axis

Identification of factors that mediate visceral and bone metastatic spread and subsequent bone remodeling events is highly relevant to successful therapeutic intervention in advanced human prostate cancer (PCa). TBX2, a T-box family transcription factor that negatively regulates cell cycle inhibitor p21, plays critical roles during embryonic development, and recent studies have highlighted its role in cancer. Here we report that TBX2 is overexpressed in human PCa specimens and bone metastases from xenograft mouse models of human PCa. Blocking endogenous TBX2 expression in PC3 and ARCaPM PCa cell models using a dominant negative construct resulted in decreased tumor cell proliferation, colony formation, and invasion in vitro. Blocking endogenous TBX2 in human PCa mouse xenografts decreased invasion and abrogation of bone and soft tissue metastasis. Furthermore, blocking endogenous TBX2 in PCa cells dramatically reduced bone colonizing capability through reduced tumor cell growth and bone remodeling in an intra-tibial mouse model. TBX2 acted in trans by promoting transcription of the canonical WNT (WNT3A) promoter. Genetically rescuing WNT3A levels in PCa cells with endogenously blocked TBX2 partially restored the TBX2-induced PCa metastatic capability in mice. Conversely, WNT3A neutralizing antibodies or WNT antagonist SFRP-2 blocked TBX2 induced invasion. Our findings highlight TBX2 as a novel therapeutic target upstream of WNT3A, where WNT3A antagonists could be novel agents for the treatment of metastasis and for skeletal complications in PCa patients.

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