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The orphan nuclear receptor Nur77 is a critical regulator of the survival and death of tumor cells. The pro-death effect of Nur77 can be regulated by its interaction with Bcl-2, resulting in conversion of Bcl-2 from a survival to killer. As Bcl-2 is overexpressed in various cancers preventing them from apoptosis and promoting their resistance to chemotherapy, targeting the apoptotic pathway of Nur77/Bcl-2 may lead to new cancer therapeutics. Here, we report our identification of XS561 as a novel Nur77 ligand that induces apoptosis of tumor cells by activating the Nur77/Bcl-2 pathway. In vitro and animal studies revealed an apoptotic effect of XS561 in a range of tumor cell lines including MDA-MB-231 triple-negative breast cancer (TNBC) and MCF-7/LCC2 tamoxifen-resistant breast cancer (TAMR) in a Nur77-dependent manner. Mechanistic studies showed XS561 potently induced the translocation of Nur77 from the nucleus to mitochondria, resulting in mitochondria-related apoptosis. Interestingly, XS561-induced accumulation of Nur77 at mitochondria was associated with XS561 induction of Nur77 phase separation and the formation of Nur77/Bcl-2 condensates. Together, our studies identify XS561 as a new activator of the Nur77/Bcl-2 apoptotic pathway and reveal a role of phase separation in mediating the apoptotic effect of Nur77 at mitochondria. XS561-induced mitochondrial-related apoptosis depends on Nur77 phase separation and the formation of Nur77/Bcl-2 condensates at mitochondria. [Display omitted] [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (Nano-ZnO) are widely used in sunscreens, clothes, medicine and electronic devices. However, the potential risks of human exposure and the potential for adverse health impacts are not well understood. Previous studies have demonstrated that exposure to Nano-ZnO caused liver damage and hepatocyte apoptosis through oxidative stress, but the molecular mechanisms that are involved in Nano-ZnO-induced hepatotoxicity are still unclear. Endoplasmic reticulum (ER) is sensitive to oxidative stress, and also plays a crucial role in oxidative stress-induced damage. Previous studies showed that ER stress was involved in many chemical-induced liver injuries. We hypothesized that exposure to Nano-ZnO caused oxidative stress and ER stress that were involved in Nano-ZnO-induced liver injury. To test our hypothesis, mice were gavaged with 200 mg/kg or 400 mg/kg of Nano-ZnO once a day for a period of 90 days, and blood and liver tissues were obtained for study. Our results showed that exposure to Nano-ZnO caused liver injury that was reflected by focal hepatocellular necrosis, congestive dilation of central veins, and significantly increased alanine transaminase (ALT) and aspartate transaminase (AST) levels. Exposure to Nano-ZnO also caused depletion of glutathione (GSH) in the liver tissues. In addition, our electron microscope results showed that ER swelling and ribosomal degranulation were observed in the liver tissues from mice treated with Nano-ZnO. The mRNA expression levels of ER stress-associated genes (grp78, grp94, pdi-3, xbp-1) were also up-regulated in Nano-ZnO-treated mice. Nano-ZnO caused increased phosphorylation of RNA-dependent protein kinase-like ER kinase (PERK) and eukaryotic initiation factor 2α (eIF2α). Finally, we found that exposure to Nano-ZnO caused increased ER stress-associated apoptotic protein levels, such as caspase-3, caspase-9, caspase-12, phosphorylation of JNK, and CHOP/GADD153, and up-regulation of pro-apoptotic genes (chop and bax). These results suggest that oxidative stress and ER stress-induced apoptosis are involved in Nano-ZnO-induced hepatotoxicity in mice. [ABSTRACT FROM AUTHOR]

Encouraged by our previous findings and in continuation of our ongoing study project in designing and synthesis of novel Nur77-targeting anti-cancer agents, a series of 5-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)-1H-indole-2-carboxamide derivatives were designed, synthesized and biologically evaluated as potent Nur77 modulators. Among synthesized compounds, 8b maintained good potency against different liver cancer cell lines and other types of cancer cell lines while exhibiting lower toxicity than the positive compound celastrol. Moreover, 8b displayed excellent Nur77-binding activity, superior to the lead compound 10g and comparable to the reference compound celastrol. The cytotoxic action of 8b towards cancer cells was associated with its induction of Nur77-mitochondrial targeting and Nur77-dependent apoptosis. Notably, 8b has good in vivo safety and anti-hepatocellular carcinoma (HCC) activity. Altogether, this study reveals that 8b is a novel Nur77 modulator with great promise for further research. [Display omitted] • New 5-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)-1H-indole-2-carboxamide derivatives are synthesized. • 8b is a good binder of Nur77 (K D = 354 nM) with broad-spectrum antitumor activity. • 8b induces Nur77-targeting mitochondria and Nur77-dependent apoptosis. • 8b displays a better safety than reference compound celastrol in vitro and in vivo. • 8b effectively inhibits tumor growth in a mice hepatoma HepG2 xenograft model. [ABSTRACT FROM AUTHOR]

[Display omitted] • 35 New Ph-C-DIM+Cl- derivatives were designed and synthesized, and A11, B5 and B15 were identified as new Nur77 modulators. • A11, B5 and B15 showed excellent pro-apoptosis activity in colon cancer cell lines HCT116 and SW620, while showed non-significant cytotoxicity against normal colon cell line NCM460. • A11, B5 and B15 bind Nur77 with high affinity, with a K d of 34 nM, 19 nM and 16 nM, respectively. • A11, B5 and B15 induced apoptosis of cancer cells by activating the Nur77/Bcl-2 apoptotic pathway. Nur77, an orphan nuclear receptor, is implicated in regulating diverse cellular biological processes including apoptosis and inflammation. We previously identified BI1071 (DIM-C-pPhCF 3 +MeSO 3 -), an oxidized methanesulfonate salt of (4-CF 3 -Ph-C-DIM), was a direct ligand of Nur77, which could activate the Nur77-Bcl-2 apoptotic pathway. To obtain more effective compounds targeting the Nur77-mediated apoptotic pathway, we designed and synthesized a series of BI1071 analogs by introducing various substituent groups in the indolyl-rings of BI1071. Structure-activity relationship study identified A11, B5 and B15 as improved analogs with stronger binding affinity to Nur77 and enhanced apoptotic activity compared to BI1071. Nur77-binding studies demonstrated that A11, B5 and B15 bind to Nur77 with a K d of 34 nM, 19 nM and 16 nM, respectively. Furthermore, mechanism studies showed that A11, B5 and B15 induced apoptosis through utilizing the Nur77-Bcl-2 pathway. [ABSTRACT FROM AUTHOR]