Aryl hydrocarbon receptor is critical for both AR-dependent and AR-indifferent enzalutamide resistance in castration-resistant prostate cancer.

The introduction of next-generation androgen receptor signaling inhibitors (ARSIs) like enzalutamide (ENZ), has improved the clinical management of castration-resistant prostate cancer (CRPC). However, acquired resistance to these therapies often develops rapidly, and the underlying resistance mechanisms remain largely unclear. Here, we identified the aryl hydrocarbon receptor (AHR) as a crucial operator of ENZ-resistant CRPC. AHR is upregulated in three ENZ-resistant human CRPC cell lines (C4-2BENZR, CWR-R1ENZR, and VCaPENZR) as well as in high-grade prostate tumors from patients receiving ENZ treatment. Stable knockdown of AHR substantially reduced the growth of ENZ-resistant CRPC cells and xenografts. Mechanistically, AHR engages in distinct transcriptional programs in a cellular context-dependent manner. AHR directly regulates the transcription and expression of androgen receptor (AR)/glucocorticoid receptor (GR) co-target genes in CWR-R1ENZR cells, suggesting an AR-dependent mechanism of ENZ resistance. AHR promotes neuroendocrine differentiation while suppressing the expression of AR/GR targets in C4-2BENZR cells, indicating an AR-indifferent mechanism of ENZ resistance. The diverse mechanisms triggered by ENZ were also manifested in clinical samples. Collectively, these findings characterize AHR's contribution to ENZ resistance in CRPC and illuminate the potential of targeting AHR for treating ARSI-resistant advanced prostate cancer.