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Prostate cancer is the most common malignant tumor in males, which frequently develops into castration-resistant prostate cancer (CRPC). CRPC metastasis is the main reason for its high mortality rate. At present, it lacks effective treatment for patients with CRPC. Raltitrexed (RTX) has been shown to be effective in the treatment of colorectal cancer. However, the effect of RTX on prostate cancer and the underlying mechanism remain unknown. In the current study, we found that RTX could dose-dependently inhibit proliferation, migration, colony formation and induce apoptosis in DU145 and PC-3 cells. RTX also increased ROS generation in prostate cancer cells. Pretreatment with N -acetyl-L-cysteine (NAC) significantly prevented RTX-induced cell apoptosis and endoplasmic reticulum (ER) stress signaling activation in prostate cancer cells. Additionally, we found RTX-induced ROS generation and ER stress activation depended on the expression of heat shock protein family A member 8 (HSPA8). Over-expression of HSPA8 could alleviate RTX-induced cell apoptosis, ROS generation and ER stress signaling activation. Finally, our study also showed that RTX attenuated the tumor growth of prostate cancer in the DU145 xenograft model and significantly downregulated HSPA8 expression and activated ER stress signaling pathway in tumor tissues. Our study is the first to reveal that RTX induces prostate cancer cells apoptosis through inhibiting the expression of HSPA8 and further inducing ROS-mediated ER stress pathway action. This study suggests that RTX may be a novel promising candidate drug for prostate cancer therapy. [Display omitted] • RTX suppressed the cell growth of prostate cancer both in vitro and in vivo. • RTX induced cell apoptosis through increasing ROS generation and activating ER stress signaling in CRPC cells. • RTX induced ROS generation and ER stress activation depended on inhibiting the expression of HSPA8 in CRPC cells. [ABSTRACT FROM AUTHOR]

The compound p -nitrophenol, which shows the anti-androgenic activity, can easily become anthropogenic pollutants and pose a threat to the environment and human health. Previous work indicates that the anti-androgenic mechanism of p -nitrophenol is complex and may involve several components in the AR signaling pathway, but the molecular details of how p -nitrophenol inhibits AR signaling are still not quite clear. Here, we characterized p -nitrophenol binds to the FK1 domain of an AR positive regulator FKBP51 with micromolar affinity and structural analysis of FK1 domain in complex with p -nitrophenol revealed that p -nitrophenol occupies a hydrophobic FK1 pocket that is vital for AR activity enhancement. Molecular dynamics simulation indicated that p -nitrophenol is stably bound to the FK1 pocket and the hotspot residues that involved p -nitrophenol binding are mainly hydrophobic and overlap with the AR interaction site. Furthermore, we showed that p -nitrophenol inhibits the androgen-dependent growth of human prostate cancer cells, possibly through down-regulating the expression levels of AR activated downstream genes. Taken together, our data suggests that p -nitrophenol suppresses the AR signaling pathway at least in part by blocking the interaction between AR and its positive regulator FKBP51. We believe that our findings could provide new guidelines for assessing the potential health effects of p -nitrophenol. [ABSTRACT FROM AUTHOR]