Project description:Background: Ewing sarcoma (EwS) are characterized by oncogenic chimeric EWS-ETS proteins. EZH2 is upregulated via predominant EWS-FLI1 in EwS. RNAi of EZH2 revealed an EZH2-maintained, undifferentiated, stemness phenotype. Herein, microarray analysis demonstrated that treatment with HDAC inhibitors (HDACi) entinostat or TSA resulted in the induction of a similar pattern of differentiation genes as observed after EZH2 RNAi. This indicates that EZH2-containing PRC2 complexes may serve as a building block of class I HDAC activity in EwS. Methods: The role of class I HDACs was determined using different inhibitors including TSA, romidepsin (FK228), entinostat (MS-275) and PCI-34051 as well as CRISPR/Cas9 class I HDAC knock outs and HDAC RNAi. To analyze resulting changes microarray and gene set enrichment analysis (GSEA), qRT-PCR, western blotting, Co-IP, proliferation, apoptosis, differentiation, invasion assays and xenograft-mouse models were used. Results: Class I HDACs are constitutively expressed in EwS. They seem regulated via EWS-FLI1. Interestingly, patients with high levels of individual class I HDAC expression show decreased overall survival. CRISPR/Cas9 class I HDAC knock out of individual HDACs such as HDAC1 and HDAC2 inhibited growth, invasiveness, and blocked local tumor growth in xenograft mice. Microarray and GSEA analysis demonstrated that treatment with individual HDAC inhibitors (HDACi) blocked an EWS-FLI1 specific expression profile, while entinostat in addition suppressed metastasis relevant genes. EwS cells demonstrated increased susceptibility to treatment with first line chemotherapeutics including doxorubicin in the presence of HDACi. Furthermore, HDACi treatment mimicked RNAi of EZH2 in EwS. Treated cells showed diminished growth capacity, but an increased endothelial as well as neuronal differentiation ability. HDACi synergizes with EED inhibitor (EEDi) in vitro and together inhibited tumor growth in xenograft mice. Co-IP experiments identified HDAC class I family members as part of a regulatory complex together with PRC2. Conclusion: Class I HDAC proteins seem to be important mediators of the pathognomonic EWS-ETS-mediated transcription program in EwS and in combination therapy, co-treatment with HDACi are interesting new treatment opportunities for this malignant disease.

Project description:Purpose: Gastric cancer remains one of the deadliest neoplasms worldwide, with a high need for new therapeutic options. Efficacies of targeted therapies are often limited owing to the inter- and intratumoral heterogeneity of gastric cancer. Thus, drugs with broader mechanisms of action rather than relying on the inhibition of a single specific oncogene are needed. Preclinical studies have identified histone deacetylases (HDAC) and their respective isoforms as potential therapeutic targets in gastric cancer. However, clinical efficacies are moderate and the mechanism(s) of action of HDAC inhibitors (HDACi) are only partially understood. Methods: In a panel of gastric cancer cell lines with different molecular characteristics, tumor cell inhibitory effects of different HDACi were studied. Lipid peroxidation levels were measured using flow cytometry. Proteome analysis was performed for the in-depth characterization of molecular alterations upon HDAC inhibition. HDACi effects on important ferroptosis genes were validated on the mRNA (RT-qPCR) and protein level (Western Blot). Results: Upon HDACi treatment, lipid peroxidation levels were found increased in all tested cell lines. Class-I HDACi (VK1, entinostat) showed the same toxicity profile as the pan-HDACi vorinostat. Proteome analysis revealed significant and concordant alterations in the expression of proteins related to ferroptosis induction. Key enzymes like ACSL4, POR or SLC7A11 showed distinct alterations in their expression patterns, providing an explanation for the increased lipid peroxidation. Alterations of POR and SLC7A11 levels upon treatment were also confirmed in primary human gastric cancer tissue cultures as relevant ex vivo model. Conclusion: We identify the induction of ferroptosis as a new mechanism of action of class-I HDACi in gastric cancer. Notably, these findings were independent of the genetic background of the cell lines, thus introducing HDAC inhibition as a more general therapeutic principle besides other, less broadly usable targeted drugs.

Dataset Information

Gene expression profiling of histone deacetylase inhibition in epithelioid sarcoma

Publications

HDAC Inhibition for the Treatment of Epithelioid Sarcoma: Novel Cross Talk Between Epigenetic Components.

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