Fig. 1: NEPC preclinical modes show modest response to EZH2i.

A Prostate cancer models (Top panel – AR-driven PRAD; bottom panel – AR-indifferent NEPC) were treated with vehicle (Veh; DMSO) or 5 μM of tazemetostat (Taz). CellTiter-Glo® luminescent cell viability assay was performed after 6 days of treatment. Columns, means of values (n = 5; 22Rv1, n = 4); white, vehicle treatment; red, tazemetostat treatment; bars, SEM values; –, p-value > 0.05 (not significant); *, p-value < 0.05, all statistical analyses used Wilcoxon two-sided tests. B (top) WCM12, NEPC patient-derived xenograft (PDX) model was grown subcutaneously in SCID mice. Mice were randomized into treatment groups when tumor volume reached 100 mm³. Mice were treated with vehicle (n = 4) or 250 mg/kg b.i.d. of tazmetostat (EPZ, n = 5) for 18 days. Two mice in the EPZ group were euthanized before experimental endpoint adhering to animal welfare guidelines. Connected dots, means of values obtained from independent biological replicates; gray, vehicle treatment; red, tazemetostat treatment; bars, SEM values. (bottom) MSKPCa4, NPEC organoid-derived xenograft model were grown subcutaneously in both flanks of the mice and randomized into treatment groups when tumor volume reached approximately 200 mm³. Mice were treated with vehicle (n = 5) or 150 mg/kg GSK126 (n = 5) for 6 weeks. Connected dots, means of values obtained from independent biological replicates; gray, vehicle treatment; magenta, GSK126 treatment; bars, SEM values. C Western blot analysis (Top panel – AR-driven PRAD; bottom panel – AR-indifferent NEPC) in a parallel experiment of (A) confirming the downregulation of H3K27me3 upon tazemetostat treatment in vitro. Blots were reprobed for total-histone-H3 as a loading control. Representative western blot from three independent experiments is shown. D Western blot analysis of tumor samples from (B - top) confirming the downregulation of H3K27me3 upon tazemetostat treatment in vivo. Blots were reprobed for total-histone-H3 and β-actin as loading controls. Representative western blot from two independent experiments is shown. E Immunohistochemistry of tumor samples from (B – bottom) confirming the downregulation of H3K27me3 upon GSK126 treatment in vivo. Scale bar = 100 μm.