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Ewing sarcoma (EwS) is driven by the EWS-FLI1 (EF) oncoprotein and is assumed to originate from mesenchymal progenitors during bone development. Attempts to generate a EwS genetic mouse model by targeting EF expression to the mesenchymal lineage so far failed to result in tumorigenesis. Here, we investigated the influence of bone niche-derived factors on EF dependent transformation. We focused on IGF1 which is highly enriched in the bone during puberty when EwS incidence peaks, and which was previously proposed to play an essential role in EwS pathogenesis. We restricted EF expression to mesenchymal stem cells during endochondral bone formation by crossing an EF knock-in mouse with a mouse expressing Prx1-driven Cre recombinase. The resulting EFprx1 progeny died after birth as consequence of severe skeletal malformations resulting from differentiation arrest of early chondrocytes. In vitro, these embryonic EF transgenic chondrocyte-like mesenchymal stem cells (EFprx1 MSCLC) are immortal, but largely failed to form colonies in soft-agar as functional surrogate of full malignant transformation. In contrast, when treated with IGF1 for 4 weeks, a significant increase in soft-agar colony formation was observed, which was dependent on sustained EF expression. Strikingly, cells from these colonies maintained their transformed phenotype in absence of further IGF1 treatment and gave rise to aggressively growing tumors upon xenotransplantation in mice. Analysis of differentially expressed genes from these stably IGF1-reprogrammed, fully transformed EFprx1 MSCLC showed a significant enrichment for the EwS specific EF transcriptional signature with upregulation of Foxm1 and cell cycle-related pathways, and down-regulation of apoptotic gene sets. Cluster analysis of open chromatin regions in EF immortalized versus fully transformed and wildtype cells revealed five distinct chromatin modules. Of these, module 2 comprises genomic regions that open up exclusively in IGF1 reprogrammed EF expressing cells. Among associated genes, Yap1 was most highly induced in IGF1 reprogrammed EFprx1 MSCLC. Consistent with this finding, RNA-seq revealed enrichment of a Yap1 transcriptional signature in IGF1 reprogrammed versus parental EF expressing cells. In addition, chromatin module 4, which comprises regions open in parental and IGF1 reprogrammed EFprx1 MSCLC but not in wildtype MSC, is highly enriched in binding motifs for TEAD transcription factors, the functional effectors of YAP1 signaling. We therefore hypothesize that YAP1 induction by IGF1 reprogramming synergizes with EF in the activation of module 4 genes. Strikingly, modules 2 and 4 comprise hallmark genes of stemness and self-renewal which also characterize human EwS, including Bcl11b, Prkcb, Sox2, Ccnd1, and Klf5, as well as the top EwS dependency gene Igf2bp1. Our data suggest that transient IGF1 exposure in the bone microenvironment during puberty may be required for EF driven EwS tumor initiation, and we identify a central role of YAP1 in the early phases of EwS pathogenesis. Citation Format: Heinrich Kovar, Rahil Noorizadeh, Florian Halbritter, Utkarsh Kapoor, Wolfgang Mikulits, Richard Moriggl, Barbara Sax. YAP1 is a key regulator of EWS-FLI1-dependent malignant transformation upon IGF1 mediated reprogramming of bone mesenchymal stem cell-like cells [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr PR003.

Ewing sarcoma (EwS), an aggressive bone and soft tissue cancer predominantly occurring during adolescence, is driven by the chimeric EWS-FLI1 oncogene. It is assumed that a permissive cellular context or potentially additional complementing mutations are necessary for the EWS-FLI1 fusion to exert its full oncogenic effect. Prior efforts to generate genetic EwS mouse models failed because of high EWS-FLI1 induced apoptosis when expressed in various candidate progenitor cell types. In our study, we restricted EWS-FLI1 expression to mesenchymal stem cells during endochondral bone formation by crossing a mouse containing EWS-FLI1 knocked into the Rosa26 locus with a mouse expressing Prx1-driven Cre recombinase. However, the resulting EFprx1 progeny died after birth as functional consequence of severe skeletal malformations resulting from differentiation arrest of early chondrocytes. In vitro, these embryonic EWS-FLI1 transgenic chondrocyte-like mesenchymal stem cells (EFprx1 MSCLC) are immortal, but not fully transformed. However, we observed elevated levels of cleaved PARP-1, a surrogate marker of apoptosis. This apparent increased cellular turnover was paralleled by down-regulation of anti-apoptotic Bcl2a family genes as identified by RNA-seq analysis of EFprx1 MSCLC. The peak incidence of human EwS occurs during puberty, a developmental period in which several growth promoting hormones are highly enriched in the bone microenvironment. Among them is IGF1, which is known for its anti-apoptotic activity through upregulation of Bcl2 family genes. As previous studies implied IGF1 signaling essential in EwS pathogenesis, we speculated that IGF1 treatment may aid in the transformation process of EFprx1 MSCLC. In fact, a significant increase in soft-agar colony formation was observed upon IGF1 treatment for 4 weeks. To test whether IGF1 had irreversibly reprogrammed EFPrx1 MSCLC, we picked colonies grown in presence of IGF1, expanded and re-assayed them after 5 weeks in absence of the hormone. Strikingly, EFprx1 MSCLC retained their transformed phenotype not only in the soft-agar assay but also upon xenotransplantation in mice. Gene set enrichment analysis of upregulated genes from these stably hormone-reprogramed fully transformed EFprx1 MSCLC showed a significant enrichment for the EWS-FLI1 specific transcriptional signature and cell cycle-related pathways, while apoptotic gene sets were downregulated. Our data suggest that transient IGF1 exposure in the bone microenvironment may be required for EWS-FLI1 driven transformation. We propose that EwS formation could be influenced by hormonal changes during puberty. Based on these findings, we postulate that correct developmental timing of EWS-FLI1 expression may play a pivotal role for the generation of an EwS mouse model. Citation Format: Rahil Noorizadeh, Florian Halbritter, Barbara Sax, Wolfgang Mikulits, Richard Moriggl, Heinrich Kovar. Transient IGF1 exposure stably reprograms EWS-FLI1 immortalized embryonal limb-derived mesenchymal stem cell-like cells to full transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1669.

Purpose Aim of the study was to find out if gallic acid (GA), a common phenolic in plant foods, prevents obesity induced DNA damage which plays a key role in the induction of overweight associated cancer. Methods Male and female C57BL6/J mice were fed with a low fat or a high fat diet (HFD). The HFD group received different doses GA (0, 2.6–20 mg/kg b.w./day) in the drinking water for 1 week. Subsequently, alterations of the genetic stability in blood and inner organs were monitored in single cell gel electrophoresis assays. To elucidate the underlying molecular mechanisms: oxidized DNA bases, alterations of the redox status, lipid and glucose metabolism, cytokine levels and hepatic NF-κB activity were monitored. Results HFD fed animals had higher body weights; increased DNA damage and oxidation of DNA bases damage were detected in colon, liver and brain but not in blood and white adipose tissue. Furthermore, elevated concentrations of insulin, glucose, triglycerides, MCP-1, TNF-α and NF-κB activity were observed in this group. Small amounts of GA, in the range of human consumption, caused DNA protection and reduced oxidation of DNA bases, as well as biochemical and inflammatory parameters. Conclusions Obese animals have increased DNA damage due to oxidation of DNA bases. This effect is probably caused by increased levels of glucose and insulin. The effects of GA can be explained by its hypoglycaemic properties and indicate that the consumption of GA-rich foods prevents adverse health effects in obese individuals. Electronic supplementary material The online version of this article (10.1007/s00394-018-1782-2) contains supplementary material, which is available to authorized users.

Obesity as a multifactorial disorder involves low-grade inflammation, increased reactive oxygen species incidence, gut microbiota aberrations, and epigenetic consequences. Thus, prevention and therapies with epigenetic active antioxidants, (-)-Epigallocatechin-3-gallate (EGCG), are of increasing interest. DNA damage, DNA methylation and gene expression ofDNA methyltransferase 1,interleukin 6, andMutL homologue 1were analyzed in C57BL/6J male mice fed a high-fat diet (HFD) or a control diet (CD) with and without EGCG supplementation. Gut microbiota was analyzed with quantitative real-time polymerase chain reaction. An induction of DNA damage was observed, as a consequence of HFD-feeding, whereas EGCG supplementation decreased DNA damage. HFD-feeding induced a higher inflammatory status. Supplementation reversed these effects, resulting in tissue specific gene expression and methylation patterns ofDNA methyltransferase 1andMutL homologue 1. HFD feeding caused a significant lower bacterial abundance. TheFirmicutes/Bacteroidetesratio is significantly lower in HFD + EGCG but higher in CD + EGCG compared to control groups. The results demonstrate the impact of EGCG on the one hand on gut microbiota which together with dietary components affects host health. On the other hand effects may derive from antioxidative activities as well as epigenetic modifications observed on CpG methylation but also likely to include other epigenetic elements.

Since publication of the article, the authors became aware that Figure 6(A,D) contained errors in the bands and loading controls. The newly compiled Figure 6A and 6D is given below.

Obesity is associated with low-grade inflammation, increased ROS production and DNA damage. Supplementation with antioxidants might ameliorate DNA damage and support epigenetic regulation of DNA repair. C57BL/6J male mice were fed a high-fat (HFD) or a control diet (CD) with and without vitamin E supplementation (4.5 mg/kg body weight (b.w.)) for four months. DNA damage, DNA promoter methylation and gene expression of Dnmt1 and a DNA repair gene (MLH1) were assayed in liver and colon. The HFD resulted in organ specific changes in DNA damage, the epigenetically important Dnmt1 gene, and the DNA repair gene MLH1. Vitamin E reduced DNA damage and showed organ-specific effects on MLH1 and Dnmt1 gene expression and methylation. These results suggest that interventions with antioxidants and epigenetic active food ingredients should be developed as an effective prevention for obesity—and oxidative stress—induced health risks.

Ewing sarcoma (ES) is the second most frequent childhood bone cancer driven by the EWS/FLI1 (EF) fusion protein. Genetically defined ES models are needed to understand how EF expression changes bone precursor cell differentiation, how ES arises and through which mechanisms of inhibition it can be targeted. We used mesenchymal Prx1-directed conditional EF expression in mice to study bone development and to establish a reliable sarcoma model. EF expression arrested early chondrocyte and osteoblast differentiation due to changed signaling pathways such as hedgehog, WNT or growth factor signaling. Mesenchymal stem cells (MSCs) expressing EF showed high self-renewal capacity and maintained an undifferentiated state despite high apoptosis. Blocking apoptosis through enforced BCL2 family member expression in MSCs promoted efficient and rapid sarcoma formation when transplanted to immunocompromised mice. Mechanistically, high BCL2 family member and CDK4, but low P53 and INK4A protein expression synergized in Ewing-like sarcoma development. Functionally, knockdown of Mcl1 or Cdk4 or their combined pharmacologic inhibition resulted in growth arrest and apoptosis in both established human ES cell lines and EF-transformed mouse MSCs. Combinatorial targeting of survival and cell cycle progression pathways could counteract this aggressive childhood cancer.

Obesity as a multifactorial disorder involves low-grade inflammation, increased reactive oxygen species incidence, gut microbiota aberrations, and epigenetic consequences. Thus, prevention and therapies with epigenetic active antioxidants, (−)-Epigallocatechin-3-gallate (EGCG), are of increasing interest. DNA damage, DNA methylation and gene expression of DNA methyltransferase 1, interleukin 6, and MutL homologue 1 were analyzed in C57BL/6J male mice fed a high-fat diet (HFD) or a control diet (CD) with and without EGCG supplementation. Gut microbiota was analyzed with quantitative real-time polymerase chain reaction. An induction of DNA damage was observed, as a consequence of HFD-feeding, whereas EGCG supplementation decreased DNA damage. HFD-feeding induced a higher inflammatory status. Supplementation reversed these effects, resulting in tissue specific gene expression and methylation patterns of DNA methyltransferase 1 and MutL homologue 1. HFD feeding caused a significant lower bacterial abundance. The Firmicutes/Bacteroidetes ratio is significantly lower in HFD + EGCG but higher in CD + EGCG compared to control groups. The results demonstrate the impact of EGCG on the one hand on gut microbiota which together with dietary components affects host health. On the other hand effects may derive from antioxidative activities as well as epigenetic modifications observed on CpG methylation but also likely to include other epigenetic elements.

Ewing sarcoma (ES) is the second most frequent childhood bone cancer driven by the EWS/FLI1 (EF) fusion protein. Genetically defined ES models are needed to understand how EF expression changes bone precursor cell differentiation, how ES arises and through which mechanisms of inhibition it can be targeted. We used mesenchymal Prx1-directed conditional EF expression in mice to study bone development and to establish a reliable sarcoma model. EF expression arrested early chondrocyte and osteoblast differentiation due to changed signaling pathways such as hedgehog, WNT or growth factor signaling. Mesenchymal stem cells (MSCs) expressing EF showed high self-renewal capacity and maintained an undifferentiated state despite high apoptosis. Blocking apoptosis through enforced BCL2 family member expression in MSCs promoted efficient and rapid sarcoma formation when transplanted to immunocompromised mice. Mechanistically, high BCL2 family member and CDK4, but low P53 and INK4A protein expression synergized in Ewing-like sarcoma development. Functionally, knockdown of Mcl1 or Cdk4 or their combined pharmacologic inhibition resulted in growth arrest and apoptosis in both established human ES cell lines and EF-transformed mouse MSCs. Combinatorial targeting of survival and cell cycle progression pathways could counteract this aggressive childhood cancer.