Hypoxia- and dexamethasone-dependent HIF1α-glucocorticoid receptor interaction leads to degradation of glucocorticoid receptor in pituitary adenomas.

Cushing disease has a very high mortality rate and glucocorticoid resistance caused by GR down-regulation is one major reason of mortality. Although HIF1α signaling and GR signaling are involved in the pathogenesis of pituitary adenomas, it's unclear whether and how these two essential pathways could cross-talk with each other. Here, we performed a comprehensive study to investigate the reciprocal effects of HIF1α and GR on each other in AtT20 cell lines and explored the potential therapeutic effect of HIF1α inhibitor in in-vivo mouse model. We find that hypoxia up-regulated the promoter activity, mRNA and protein levels of GR and the induced GR protein was localized in cytosol. On the other hand, GR activation by its agonist DEX increased HIF1α protein through post-transcriptional mechanism. However, hypoxia and DEX show differential synergistic effects on HIF1α and GR. In hypoxia-DEX condition, HIF1α protein was further up-regulated but mainly localized in cytosol while GR was trapped and degraded in cytosol via UPS pathway. Further Co-IP experiments demonstrate that DNA binding domain of GR can interact with PASb domain of HIF1α. In a in-vivo mouse model of Cushing's disease, HIF1α inhibitor reduced HIF1α and GR protein levels, reduced tumor size and lowered the plasma concentrations of ACTH and corticosterone. In summary, we find that a novel HIF1α-GR crosstalk contributes to the pathogenesis of pituitary adenomas and HIF1α inhibitor shows potential therapeutic effects for Cushing's disease.

Effective inhibition of MYC-amplified group 3 medulloblastoma by FACT-targeted curaxin drug CBL0137.

Medulloblastoma (MB) is the most common malignant pediatric brain tumor that can be categorized into four major molecular subgroups. Group 3 MB with MYC amplification (MYCamp-G3-MB) has been shown to be highly aggressive and exhibited worst prognosis, indicating the need for novel effective therapy most urgently. A few epigenetic targeted therapeutic strategies have recently been proven to effectively treat preclinical models of MYCamp-G3-MB, including BET inhibition, HDAC inhibition and SETD8 inhibition, unveiling a promising direction for further investigation. In this study, we carried out systemic bioinformatic analyses of public-available MB datasets as well as functional genomic screening datasets of primary MYCamp-G3-MB lines to search for other potential therapeutic targets within epigenetic modulators. We identified SSRP1, a subunit of histone-chaperone FACT complex, to be the top drug target candidate as it is highly cancer-dependent in whole-genome CRISPR-Cas9 screening across multiple MYCamp-G3-MB lines; significantly upregulated in MYCamp-G3-MB compared to normal cerebellum and most of the rest MB subtypes; its higher expression is correlated with worse prognosis; and it has a blood-brain-barrier penetrable targeted drug that has entered early phase human clinical trials already. Then we utilized RNA-interference approach to verify the cancer-dependency of SSRP1 in multiple MYCamp-G3-MB lines and further confirmed the therapeutic efficacy of FACT-targeted curaxin drug CBL0137 on treating preclinical models of MYCamp-G3-MB in vitro and in vivo, including an orthotopic intracranial xenograft model. Mechanistically, transcriptome analyses showed CBL0137 preferentially suppressed cell-cycle and DNA-repair related biological processes. Moreover, it selectively disrupted transcription of MYC and NEUROD1, two critical oncogenic transcription factors of MYCamp-G3-MB, via depleting FACT complex from their promoter regions. In summary, our study demonstrates FACT-targeted CBL0137 works effectively on treating MYCamp-G3-MB, presenting another promising epigenetic-targeted therapeutic strategy against the most devastating form of MB.

Site-specific chemical fatty-acylation for gain-of-function analysis of protein S-palmitoylation in live cells.

Protein S-palmitoylation, or S-fatty-acylation, regulates many fundamental cellular processes in eukaryotes. Herein, we present a chemical fatty-acylation approach that involves site-specific incorporation of cycloalkyne-containing unnatural amino acids and subsequent bioorthogonal reactions with fatty-acyl tetrazines to install fatty-acylation mimics at target protein sites, allowing gain-of-function analysis of S-palmitoylation in live cells.

Tunable Cyclization Strategy for the Synthesis of Zizaene-, allo-Cedrane-, seco-Kaurane-, and seco-Atesane-Type Skeletons.

A versatile Lewis acid-mediated cyclization strategy has been developed for selectively establishing zizaene-, allo-cedrane-, seco-kaurane-, and seco-atesane-type skeletons. The zizaene- and seco-atesane-type skeletons can be obtained in a cascade manner, which involves Diels-Alder reaction of cyclic enones with bis-silyloxy dienes and carbocyclization of yne-enolates through Lewis acid dependent 5- or 6-exo-dig modes. This cyclization strategy was also employed for the core synthesis of tashironin.