The combined effect of epigenetic inhibitors for LSD1 and BRD4 alters prostate cancer growth and invasion

Epigenetic modifications play an important role in prostate tumor development and progression. Epigenetic drugs are emerging as effective modulators of gene expression that act on pathways potentially important in the control of cancer clinically. We investigated two different epigenetic modulating drugs, SP-2509 and JQ1, that target histone lysine demethylase 1 (LSD1), and bromodomain-containing protein (BRD), respectively and their combined effect in three different prostate cancer (PCa) types: 1) androgen receptor (AR)-positive and androgen-sensitive; 2) AR-positive but castration-resistant; and 3) androgen-nonresponsive. We found combined treatment provided a synergistic growth inhibition in castration-resistant PCa cells but knockdown of AR reduced sensitivity to both inhibitors in these cells. In the androgen-sensitive cell lines, AR knockdown attenuated sensitivity to the LSD1 inhibitor but not the JQ1 inhibitor. Strikingly, treatment with SP-2509 slightly, and JQ1 markedly increased invasion in PCa cells with high AR expression but decreased invasion in PCa cells with low/negative AR expression. Our results suggest that these two epigenetic drugs are novel and promising compounds for the development of PCa therapeutics, particularly for castration-resistant disease. However, due to the potential risks, including metastasis, caution must be exercised in the clinical setting.