Castration Determines the Efficacy of ETAR Blockade in a Mouse Model of Prostate Cancer Bone Metastasis

Area of Science:

• Oncology
• Endocrinology
• Bone Biology

Background:

• Bone metastasis is a painful complication of advanced prostate cancer.
• Endothelin-1 and endothelin A receptor (ETAR) signaling promote osteoblast activation and the osteosclerotic response in prostate cancer bone metastasis.
• ETAR antagonists show limited efficacy in clinical trials when combined with standard androgen deprivation therapy (ADT).

Purpose of the Study:

• To investigate the interaction between ETAR signaling and androgen signaling in prostate cancer bone metastasis.
• To determine if ETAR antagonists are more efficacious when androgen signaling is suppressed beyond standard ADT levels.

Main Methods:

• A mouse model of prostate cancer bone metastasis was established using intracardiac inoculation of ARCaPM cells.
• Mice were subjected to either castration or sham operation and treated with the ETAR antagonist zibotentan or vehicle control.
• Experimental groups included vehicle+sham, vehicle+castrate, zibotentan+sham, and zibotentan+castrate.
• Skeletal lesions and survival were monitored radiographically.

Main Results:

• Combined treatment with zibotentan and castration (complete androgen deprivation) resulted in significantly longer survival and a single incidental skeletal lesion.
• Treatment with zibotentan alone (in sham-operated mice) led to the shortest survival and the highest number of skeletal lesions.
• Vehicle-treated groups (both sham and castrate) exhibited intermediate survival and lesion burden compared to zibotentan-treated groups.

Conclusions:

• There is a complex interaction between ETAR and androgen signaling in prostate cancer bone metastasis.
• ETAR blockade is most efficacious when combined with complete androgen deprivation, suggesting a synergistic effect.
• These findings highlight a potential therapeutic strategy for advanced prostate cancer with bone metastasis.