UC Irvine

Castration-resistant prostate cancer (CRPC) is a lethal disease and its progression is primarily driven by reactivation of androgen receptor (AR) signaling even after treatments with castration and multiple AR pathway inhibitors [CHAPTER 1]. In addition, epigenetic mechanisms, including lysine-specific demethylase 1A (LSD1) overexpression, have recently been appreciated as cell-fate determining drivers of the heterogeneity of CRPC and the associated treatment resistances [CHAPTER 2]. Therefore, we hypothesized that dual targeting of AR and LSD1 might be a more effective therapeutic approach in preventing or delaying the progression of CRPC. Through a series of structural similarity search of flavin adenine dinucleotide (FAD, a co-factor of LSD1) analogs, molecular docking studies and experimental screenings of inhibitors for LSD1 enzymatic activity and AR transcriptional activity, we have discovered for the first time that Sanguinarine, a naturally occurring compound from the root of Sanguinaria canadensis as well as other Fumaria species, is a potent dual inhibitor of both LSD1 and AR [CHAPTER 4]. In vitro Surface Plasmon Resonance (SPR) and in vivo Cellular thermal shift assay (CETSA) assays confirmed that Sanguinarine directly binds to both LSD1 and AR with equal or very close binding affinities. In addition, the growth inhibitory and anti-AR signaling effects of Sanguinarine are partially dependent on the expression levels of LSD1 as shown in LSD1 knockdown and overexpression experiments. To assess the effect of Sanguinarine on CRPC progression, we found that Sanguinarine inhibited the neuroendocrine trans-differentiation of prostate cancer cell lines induced by Dovitinib, a pan—tyrosine kinase inhibitor in prostate cancer clinical trials, both in vitro and in vivo in xenograft models and significantly enhanced the anti-tumor efficacy of Dovitinib [CHAPTER 6]. Furthermore, Sanguinarine more effectively reduce the growth and regeneration of spheroids from stem cell-like prostate cancer cells or cancer initiation cells than bulk prostate cancer cells both in vitro and in an vivo xenograft model and down-regulates the expression of cancer stem cell markers (i.e. .Nanog, Sox2 and Oct4) [CHAPTER 7]. Overall, the results we have gathered demonstrate that Sanguinarine is a structural model as a dual inhibitor of LSD1 and AR for preventing or delay CRPC progression through mechanisms of down-regulation of AR signaling and inhibition of neuroendocrine differentiation and cancer stem cells. Our studies have provided a new strategy for treatment of CRPC.