Liquid-biopsy transcriptomic profiling uncovers molecular mediators of resistance to androgen receptor signaling inhibition in lethal prostate cancer

Androgen receptor signaling inhibitors (ARSi) are a mainstay for patients with metastatic castration-resistant prostate cancer (mCRPC). However, patient response is heterogeneous and the molecular underpinnings of ARSi resistance are not well elucidated. Here we performed transcriptome analysis of circulating tumor cells (CTCs) and peripheral blood mononuclear cells (PBMC) in the context of a prospective clinical trial of men with mCRPC treated with abiraterone (Abi) or enzalutamide (Enza). CTC RNA-sequencing identified that RB loss and enhanced E2F signaling along with BRCA loss transcriptional networks were associated with intrinsic ARSi resistance, while an inflammatory response signature was significantly associated with acquired resistance. Transcriptomic analysis of matching PBMCs identified enrichment of inflammasome gene signatures indicative of activated innate immunity at progression, with concurrent downregulation of T and NK cells. Importantly, CTC gene signatures had a significant positive association with circulating immune macroenvironment (CIME) signatures. Taken together, these data demonstrate that liquid biopsy transcriptomics can identify molecular pathways associated with clinical ARSi resistance paving the way for treatment optimization in patients with mCRPC.