<p>An adrenocortical carcinoma in Patient NCI0226 with a de-novo germline TP53 mutation. Germline DNA samples from brother and parents were not noted to have the mutation. The mutation was a novel two base substitution at codon c.358_359delCGinsAA, leading to an amino acid change, A159K. The mutation was heterozygous in the germline, and homozygous in tumor exome and transcriptome due to loss of heterozygosity of the wild-type allele.</p>
<p>Killer Immunoglobulin-Like Receptors (KIRs) and Killer Cell Lectin-Like Receptors (KLRs) Prognosticate Favorable Survival in Group A, But Not Group B</p>
Abstract BACKGROUND Diffuse midline glioma (DMG), H3K27-altered, is a lethal pediatric brain tumor driven by epigenetic dysregulation. Histone deacetylase (HDAC) inhibitors have been identified as a promising drug class; however, the precise mechanism of efficacy for these agents in DMG has not been fully explored. Furthermore, their translational potential has been limited by off-target effects and poor CNS penetration of clinically available drugs. METHODS We investigated the genetic and chemical dependencies of HDAC isoforms in DMG cell lines using CRISPR/Cas9 screening and an HDAC inhibitor toolbox. We identified an HDAC inhibitor termed “Compound 26” with class I isoform selectivity and excellent CNS penetration (brain/plasma AUC of >7). Effects of Compound 26 on DMG cells was evaluated in-vitro through assessment of cytotoxicity, proliferation and apoptosis. Mechanistic studies were undertaken using bulk RNAseq and HiChIP (H3K27ac, H3K27me3). Efficacy of Compound 26 in-vivo was determined using an aggressive orthotopic xenograft model. RESULTS We confirmed that HDAC class I isoforms are dependencies in DMG cell lines, with HDAC2 representing a selective dependency that is highly expressed in patient tumors. Compound 26 is cytotoxic in DMG cells, reducing proliferation through cell cycle arrest. Differential expression analysis confirmed profound effects on cycling programs with Compound 26 treatment. Furthermore, analysis of genome structure using HiChIP revealed global increases in H3K27ac contacts, with notable spreading along key cell cycle gene bodies such as p16 (CDKN2A). Interestingly, treatment with Compound 26 also significantly increased global H3K27me3 contacts, which is canonically decreased in H3K27-altered DMG. Most importantly, Compound 26 was well tolerated, effectively crossed the blood-brain barrier, and significantly extended survival in an aggressive DMG-orthotopic xenograft model. CONCLUSIONS This study comprehensively outlines the reliance of DMG cells on HDAC class I isoforms, elucidates novel mechanisms for this dependency, and highlights a compelling new agent to bypass prior translational pitfalls
<div>Abstract<p>The PI3K–AKT pathway has pleiotropic effects and its inhibition has long been of interest in the management of prostate cancer, where a compensatory increase in PI3K signaling has been reported following androgen receptor (AR) blockade. Prostate cancer cells can also bypass AR blockade through induction of other hormone receptors, in particular the glucocorticoid receptor (GR). Here we demonstrate that AKT inhibition significantly decreases cell proliferation through both cytostatic and cytotoxic effects. The cytotoxic effect is enhanced by AR inhibition and is most pronounced in models that induce compensatory GR expression. AKT inhibition increases canonical AR activity and remodels the chromatin landscape, decreasing enhancer interaction at the GR gene (<i>NR3C1</i>) locus. Importantly, it blocks induction of GR expression and activity following AR blockade. This is confirmed in multiple <i>in vivo</i> models, where AKT inhibition of established xenografts leads to increased canonical AR activity, decreased GR expression, and marked antitumor activity. Overall, our results demonstrate that inhibition of the PI3K/AKT pathway can block GR activity and overcome GR-mediated resistance to AR-targeted therapy. Ipatasertib is currently in clinical development, and GR induction may be a biomarker to identify responsive patients or a responsive disease state.</p></div>
Sustained androgen receptor (AR) signaling during relapse is a central driver of metastatic castration-resistant prostate cancer (mCRPC). Current AR antagonists, such as enzalutamide, fail to provide long-term benefit for the mCRPC patients who have dramatic increases in AR expression. Here, we report AR antagonists with efficacy in AR-overexpressing models. These molecules bind to the ligand-binding domain of the AR, promote AR localization to the nucleus, yet potently and selectively down-regulate AR-target genes. The molecules BG-15a and the pharmacokinetically optimized BG-15n elicit a decrease in cell and tumor growth in vitro and in vivo in models of mCRPC. BG-15a/n treatment causes the collapse of chromatin loops between enhancers and promoters at key genes in the AR-driven epigenome. AR binding in the promoter, as well as 3D chromatin clustering, is needed for genes to respond. BG-15a/n represent promising agents for treating patients with relapsed AR-driven mCRPC tumors.
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