Reversible epigenetic alterations mediate PSMA expression heterogeneity in advanced metastatic prostate cancer.

Purpose: Prostate-specific membrane antigen (PSMA) is a cell surface protein expressed in prostate cancer. PSMA targeted imaging and therapeutic approaches have shown clinical benefit, but there are limited data on the heterogeneity of PSMA tissue expression in metastatic castration-resistant prostate cancer (mCRPC) and the mechanisms involved in regulating PSMA expression are not well understood. Results: PSMA expression differed across molecular subtypes of CRPC. In a rapid autopsy cohort in which multiple metastatic sites per patient were sampled, we found that 13/52 (25%) of cases had no PSMA detected and 24/52 (46%) showed heterogeneous PSMA expression between individual metastases. Of these 52 cases, 35 (67%) cases harbored at least one PSMA negative metastatic site. Transcriptomic analyses of PSMA negative tumors revealed distinct differences relative to PSMA-positive tumors including expression of several drug targets. DNA methylation studies showed a tight correlation between CpG methylation and PSMA expression. Treatment with histone deacetylase (HDAC) and DNA methyl transferase (DNMT) inhibitors restored of PSMA expression in vitro and in vivo. Conclusions: Here, we document the extent of PSMA expression diversity in CRPC, highlight novel targeting approaches for PSMA-negative tumors and propose strategies to overcome resistance to PSMA-directed therapies. Collectively, these data can help to guide the clinical development of PSMA targeting agents for diagnosis and therapy. Experimental Design: Genome wide methylation changes were determined by whole genome bisulfite sequencing in prostate cancer patient derived xenografts (LuCaP 77,78, 93).