RB1 loss promotes a noncanonical activator function of LSD1 and sensitizes castration-resistant prostate cancer to LSD1 inhibition [ChIP-seq]

Genomic loss of RB1 is a common alteration in castration-resistant prostate cancer (CRPC) and is associated with poor patient outcomes. RB1-loss is also a driver event that promotes the neuroendocrine transdifferentiation of prostate cancer (PCa). The loss of Rb protein disrupts the Rb-E2F repressor complex and thus hyperactivates E2F transcription activators. While the impact of RB1-loss on PCa progression and linage plasticity has been previously studied, the underline mechanisms remain unclear. Using an integrated cistromic and transcriptomic analysis, we have characterized Rb activities in multiple CRPC models by identifying Rb directly regulated genes and revealed that Rb has distinct binding sites and targets in TP53-mutated CRPC. Significantly, we show that RB1-loss promotes the noncanonical activator function of LSD1/KDM1A, which stabilizes chromatin binding of E2F1, and hence sensitizes CRPC tumor to the LSD1 inhibitor treatment. These results provide new molecular insights of Rb activity in PCa progression and suggest LSD1 as a potential therapeutic target in CRPC with RB1-loss. RB ChIP-Seq were performed in both C4-2 and VCaP cells without any treatment. V5 (E2F1) ChIP-seq were performed in both C4-2-tetE2F1 WT and K185R mutant cell lines by treating with/out 50μM GSK2879552 for 24 hours under doxycycline pretreatment or not. All ChIP-seq samples contain replications.