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GSK-LSD1, Doxorubicin and AraC have no effect on KDM1A and KDM1B expression

Protein expression of ER-stress response genes following treatment with SP-2509

Targeted KDM1A inhibition and EWS/FLI knockdown induces similar transcriptional signatures

Hypersensitive SP-2509 cell lines display similar transcriptomic profiles

Cell line source/culture conditions, primer/shRNA sequences, antibodies utilized in this study and additional methods

Validation of KDM1A knockdown in Ewing sarcoma cells

Multi-agent chemotherapeutic regimes remain the cornerstone treatment for Ewing sarcoma, the second most common bone malignancy diagnosed in pediatric and young adolescent populations. We have reached a therapeutic ceiling with conventional cytotoxic agents, highlighting the need to adopt novel approaches that specifically target the drivers of Ewing sarcoma oncogenesis. As KDM1A/lysine-specific demethylase 1 (LSD1) is highly expressed in Ewing sarcoma cell lines and tumors, with elevated expression levels associated with worse overall survival (P = 0.033), this study has examined biomarkers of sensitivity and mechanisms of cytotoxicity to targeted KDM1A inhibition using SP-2509 (reversible KDM1A inhibitor). We report, that innate resistance to SP-2509 was not observed in our Ewing sarcoma cell line cohort (n = 17; IC50 range, 81 –1,593 nmol/L), in contrast resistance to the next-generation KDM1A irreversible inhibitor GSK-LSD1 was observed across multiple cell lines (IC50 > 300 μmol/L). Although TP53/STAG2/CDKN2A status and basal KDM1A mRNA and protein levels did not correlate with SP-2509 response, induction of KDM1B following SP-2509 treatment was strongly associated with SP-2509 hypersensitivity. We show that the transcriptional profile driven by SP-2509 strongly mirrors KDM1A genetic depletion. Mechanistically, RNA-seq analysis revealed that SP-2509 imparts robust apoptosis through engagement of the endoplasmic reticulum stress pathway. In addition, ETS1/HIST1H2BM were specifically induced/repressed, respectively following SP-2509 treatment only in our hypersensitive cell lines. Together, our findings provide key insights into the mechanisms of SP-2509 cytotoxicity as well as biomarkers that can be used to predict KDM1A inhibitor sensitivity in Ewing sarcoma. Mol Cancer Ther; 17(9); 1902–16. ©2018 AACR.

Cytotoxic effects of the irreversible KDM1A inhibitors GSK-LSD1 and Tranylcypromine

Multi-agent chemotherapeutic regimes remain the cornerstone treatment for Ewing sarcoma, the second most common bone malignancy diagnosed in pediatric and young adolescent populations. We have reached a therapeutic ceiling with conventional cytotoxic agents, highlighting the need to adopt novel approaches that specifically target the drivers of Ewing sarcoma oncogenesis. As KDM1A/lysine-specific demethylase 1 (LSD1) is highly expressed in Ewing sarcoma cell lines and tumors, with elevated expression levels associated with worse overall survival (P = 0.033), this study has examined biomarkers of sensitivity and mechanisms of cytotoxicity to targeted KDM1A inhibition using SP-2509 (reversible KDM1A inhibitor). We report, that innate resistance to SP-2509 was not observed in our Ewing sarcoma cell line cohort (n = 17; IC50 range, 81 –1,593 nmol/L), in contrast resistance to the next-generation KDM1A irreversible inhibitor GSK-LSD1 was observed across multiple cell lines (IC50 > 300 μmol/L). Although TP53/STAG2/CDKN2A status and basal KDM1A mRNA and protein levels did not correlate with SP-2509 response, induction of KDM1B following SP-2509 treatment was strongly associated with SP-2509 hypersensitivity. We show that the transcriptional profile driven by SP-2509 strongly mirrors KDM1A genetic depletion. Mechanistically, RNA-seq analysis revealed that SP-2509 imparts robust apoptosis through engagement of the endoplasmic reticulum stress pathway. In addition, ETS1/HIST1H2BM were specifically induced/repressed, respectively following SP-2509 treatment only in our hypersensitive cell lines. Together, our findings provide key insights into the mechanisms of SP-2509 cytotoxicity as well as biomarkers that can be used to predict KDM1A inhibitor sensitivity in Ewing sarcoma. Mol Cancer Ther; 17(9); 1902–16. ©2018 AACR.

Ewing sarcoma usually expresses the EWS/FLI fusion transcription factor oncoprotein. EWS/FLI regulates myriad genes required for Ewing sarcoma development. EWS/FLI binds GGAA-microsatellite sequences in vivo and in vitro. These sequences provide EWS/FLI-mediated activation to reporter constructs, suggesting that they function as EWS/FLI-response elements. We now demonstrate the critical role of an EWS/FLI-bound GGAA-microsatellite in regulation of the NR0B1 gene as well as for Ewing sarcoma proliferation and anchorage-independent growth. Clinically, genomic GGAA-microsatellites are highly variable and polymorphic. Current data suggest that there is an optimal “sweet-spot” GGAA-microsatellite length (of 18–26 GGAA repeats) that confers maximal EWS/FLI-responsiveness to target genes, but the mechanistic basis for this remains unknown. Our biochemical studies, using recombinant Δ22 (a version of EWS/FLI containing only the FLI portion), demonstrate a stoichiometry of one Δ22-monomer binding to every two consecutive GGAA-repeats on shorter microsatellite sequences. Surprisingly, the affinity for Δ22 binding to GGAA-microsatellites significantly decreased, and ultimately became unmeasureable, when the size of the microsatellite was increased to the sweet-spot length. In contrast, a fully functional EWS/FLI mutant (Mut9, which retains approximately half of the EWS portion of the fusion) showed low affinity for smaller GGAA-microsatellites but instead significantly increased its affinity at sweet-spot microsatellite lengths. Single-gene ChIP and genome-wide ChIP-sequencing (ChIP-seq) and RNA-seq studies extended these findings to the in vivo setting. Together, these data demonstrate the critical requirement of GGAA-microsatellites as EWS/FLI activating response elements in vivo and reveal an unexpected role for the EWS portion of the EWS/FLI fusion in binding to sweet-spot GGAA-microsatellites.

Many patients with stage I-II pancreatic adenocarcinoma do not undergo resection. We hypothesized that (1) clinical staging underestimates nodal involvement, causing stage IIB to have a greater percent of resected patients and (2) this stage-shift causes discrepancies in observed survival.The Surveillance, Epidemiology, and End Results (SEER) research database was used to evaluate cause-specific survival in patients with pancreatic adenocarcinoma from 2004-2012. Survival was compared using the log-rank test. Single-center data on 105 patients who underwent resection of pancreatic adenocarcinoma without neoadjuvant treatment were used to compare clinical and pathologic nodal staging.In SEER data, medium-term survival in stage IIB was superior to IB and IIA, with median cause-specific survival of 14, 9, and 11 months, respectively (P .001). Seventy-two percent of stage IIB patients underwent resection vs 28% in IB and 36% in IIA (P .001). In our institutional data, 12.4% of patients had clinical evidence of nodal involvement vs 69.5% by pathologic staging (P .001). Among clinical stage IA-IIA patients, 71.6% had nodal involvement by pathologic staging.Both SEER and institutional data support substantial underestimation of nodal involvement by clinical staging. This finding has implications in decisions regarding neoadjuvant therapy and analysis of outcomes in the absence of pathologic staging.

Numerous molecular abnormalities contribute to the genetic derangements involved in tumorigenesis. Chromosomal translocations are a frequent source of these derangements, producing unique fusion proteins with novel oncogenic properties. EWS/ETS fusions in Ewing sarcoma are a prime example of this, resulting in potent chimeric oncoproteins with novel biological properties and a unique transcriptional signature essential for oncogenesis. Recent evidence demonstrates that EWS/FLI, the most common EWS/ETS fusion in Ewing sarcoma, upregulates gene expression using a GGAA microsatellite response element dispersed throughout the human genome. These GGAA microsatellites function as enhancer elements, are sites of epigenetic regulation and are necessary for EWS/FLI DNA binding and upregulation of principal oncogenic targets. An increasing number of GGAA motifs appear to substantially enhance EWS/FLI-mediated gene expression, which has compelling biological implications as these GGAA microsatellites are highly polymorphic within and between ethnically distinct populations. Historically regarded as junk DNA, this emerging evidence clearly demonstrates that microsatellite DNA plays an instrumental role in EWS/FLI-mediated transcriptional regulation and oncogenesis in Ewing sarcoma. This unprecedented role of GGAA microsatellite DNA in Ewing sarcoma provides a unique opportunity to expand our mechanistic understanding of how EWS/ETS fusions influence cancer susceptibility, prognosis and transcriptional regulation.

Objective: Ewing sarcoma is a pediatric bone malignancy initiated by a t(11;22) chromosomal translocation that produces the EWS/FLI oncoprotein. EWS/FLI transcriptionally activates and represses its target genes to mediate oncogenic reprogramming. Expression of its upregulated targets correlates with EWS/FLI binding to associated GGAA-microsatellites, which show length polymorphisms. These microsatellite polymorphisms may critically affect EWS/FLI-responsiveness of key gene targets. For example, NR0B1 is necessary for EWS/FLI mediated oncogenic transformation, and we found a “sweet spot” of 18-26 repeat length as optimal for EWS/FLI mediated transcriptional activity at NR0B1 through clinical observations and in vitro studies. The mechanism underlying this optimal length is unknown. Methods: We explored the stoichiometry and binding affinity of EWS/FLI for different GGAA-repeat lengths through biochemical studies, including fluorescence polarization, ChIP-seq, and RNA-seq, combined with bioinformatics analysis. Additionally, use of mutant constructs of EWS/FLI has been critical for elucidating particular binding behavior of EWS/FLI at different microsatellite repeat lengths. Results: Our biochemical studies, using recombinant Δ22 (a version of EWS/FLI containing only the FLI portion) demonstrate a stoichiometry of one Δ22-monomer binding to every two consecutive GGAA-repeats on shorter microsatellite sequences. Surprisingly, the affinity for Δ22 binding to GGAA-microsatellites significantly decreased, and ultimately became unmeasurable, when the size of the microsatellite was increased to the “sweet spot” length. In contrast, a fully functional EWS/FLI mutant (Mut9, which retains approximately half of the EWS portion of the fusion) showed low affinity for smaller GGAA-microsatellites, but instead significantly increased its affinity at “sweet spot” microsatellite lengths. Single-gene ChIP and genome-wide ChIP-seq and RNA-seq studies extended these findings to the in vivo setting. Conclusion: Together, these data reveal an unexpected novel role for the EWS portion of the EWS/FLI fusion in DNA binding. Additionally, our data suggest a length-dependent biochemical mechanism for EWS/FLI binding and transcriptional regulation at GGAA-microsatellites. Citation Format: K. M. Johnson, S. L. Lessnick. A novel role for the EWS portion of EWS/FLI in binding GGAA-microsatellites required for oncogenic transformation in Ewing sarcoma [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr B32.

Objective: The purpose of this study is to investigate how EWS/FLI transcriptionally activates gene targets via polymorphic GGAA microsatellites. Ewing Sarcoma is a pediatric bone malignancy initiated by a t(11;22) chromosomal translocation that produces the EWS/FLI oncoprotein. EWS/FLI transcriptionally activates and represses its target genes to mediate oncogenic reprogramming. Expression of its up-regulated targets correlates with EWS/FLI binding to associated GGAA microsatellites, which show length polymorphisms. These microsatellite polymorphisms may critically affect EWS/FLI-responsiveness of key gene targets. For example, NR0B1 is necessary for EWS/FLI mediated oncogenic transformation, and we found a “sweet-spot” of 20-25 repeat length as optimal for EWS/FLI mediated transcriptional activity at NR0B1 through clinical observation and in vitro studies. The mechanism underlying this optimal length is unknown. Methods: We explored the stoichiometry and binding affinity of EWS/FLI for different repeat lengths through biochemical studies, including fluorescence polarization, and immunoprecipitation assays, combined with bioinformatics analysis. Additionally, use of EWS/FLI mutant constructs has been critical for elucidating particular binding behavior of EWS/FLI at different microsatellite repeat lengths. Results: Fluorescence anisotropy studies demonstrate that FLI binding affinity is independent of GGAA microsatellite length. In contrast, the stoichiometry of protein to DNA binding increases in specific incremental patterns with increasing microsatellite repeats. EWS/FLI mutants inform on binding, suggesting a complex relationship between microsatellite length and transcriptional activity. Conclusion: Overall our data suggests a model in which the DNA binding domain of multiple FLI monomers function as independent binding units to facilitate transcriptional activity in a length-dependent manner. The EWS portion appears to be critical for in vivo binding of genomic DNA globally. We propose that GGAA microsatellites are necessary and sufficient for EWS/FLI-mediated oncogenic transformation and that repeat length affects optimal DNA binding stoichiometry and transcriptional activity. Citation Format: Kirsten M. Johnson, Cenny Taslim, Stephen L. Lessnick. EWS/FLI regulates transcriptional activation via length-dependent GGAA microsatellites [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3509. doi:10.1158/1538-7445.AM2017-3509

Author(s): Monument, Michael J; Johnson, Kirsten M; McIlvaine, Elizabeth; Abegglen, Lisa; Watkins, W Scott; Jorde, Lynn B; Womer, Richard B; Beeler, Natalie; Monovich, Laura; Lawlor, Elizabeth R; Bridge, Julia A; Schiffman, Joshua D; Krailo, Mark D; Randall, R Lor; Lessnick, Stephen L | Abstract: BackgroundThe genetics involved in Ewing sarcoma susceptibility and prognosis are poorly understood. EWS/FLI and related EWS/ETS chimeras upregulate numerous gene targets via promoter-based GGAA-microsatellite response elements. These microsatellites are highly polymorphic in humans, and preliminary evidence suggests EWS/FLI-mediated gene expression is highly dependent on the number of GGAA motifs within the microsatellite.ObjectivesHere we sought to examine the polymorphic spectrum of a GGAA-microsatellite within the NR0B1 promoter (a critical EWS/FLI target) in primary Ewing sarcoma tumors, and characterize how this polymorphism influences gene expression and clinical outcomes.ResultsA complex, bimodal pattern of EWS/FLI-mediated gene expression was observed across a wide range of GGAA motifs, with maximal expression observed in constructs containing 20-26 GGAA motifs. Relative to white European and African controls, the NR0B1 GGAA-microsatellite in tumor cells demonstrated a strong bias for haplotypes containing 21-25 GGAA motifs suggesting a relationship between microsatellite function and disease susceptibility. This selection bias was not a product of microsatellite instability in tumor samples, nor was there a correlation between NR0B1 GGAA-microsatellite polymorphisms and survival outcomes.ConclusionsThese data suggest that GGAA-microsatellite polymorphisms observed in human populations modulate EWS/FLI-mediated gene expression and may influence disease susceptibility in Ewing sarcoma.

The purpose of this study is to investigate how EWS/FLI transcriptionally activates gene targets via polymorphic GGAA microsatellites. Ewing Sarcoma is a pediatric bone malignancy initiated by a t(11;22) chromosomal translocation that produces the EWS/FLI oncoprotein. EWS/FLI transcriptionally activates and represses its target genes to mediate oncogenic reprogramming. Expression of its up-regulated targets correlates with EWS/FLI binding to associated GGAA microsatellites. These microsatellites show length polymorphisms, suggesting that microsatellite polymorphisms may have critical effects on EWS/FLI-responsiveness of key gene targets. For example, NR0B1 is necessary for EWS/FLI mediated oncogenic transformation, and we found a “sweet-spot” of 24-25 repeat length as optimal for EWS/FLI mediated transcriptional activity at NR0B1. The mechanism underlying this optimal length is unknown. We therefore explored the stoichiometry and binding affinity of EWS/FLI for different repeat lengths through biochemical studies combined with molecular modeling simulation. Our data demonstrate a complex relationship between microsatellite length and transcriptional activity. Fluorescence anisotropy studies demonstrate that FLI binding affinity is independent of GGAA microsatellite length. In contrast, the stoichiometry of protein to DNA binding increases in specific incremental patterns with increasing microsatellite repeats. Gel shift binding assays elucidate the minimal microsatellite length critical for binding. Overall our data suggests a model in which the DNA binding domain of multiple monomers of FLI function as independent binding units to facilitate transcriptional activity in a length-dependent fashion. We propose that GGAA microsatellites are necessary and sufficient for EWS/FLI-mediated oncogenic transformation and that repeat length affects optimal DNA binding stoichiometry and transcriptional activity. Citation Format: Kirsten M. Johnson, Kunal Gangwal, James Robertson, Thomas E. Cheatham, Stephen L. Lessnick. EWS/FLI regulates transcriptional activation in Ewing sarcoma via length dependent GGAA microsatellites. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr A34.