Browsing by Subject "RNA-Binding Protein EWS"
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Item High-Throughput Chemical Screen for Inhibitors of EWS-FLI1 Using a Trangenic Zebrafish Model of Ewing Sarcoma(2015-01-26) Burton, Barbara; He, Christy F.; Neumann, Joanie C.; Zmau, Daniel P.; Amatruda, James F.Ewing Sarcoma is the second most common primary bone tumor of children and adolescents. With a lack of targeted therapies, survival remains poor despite remarkably intense chemotherapeutic regimens. 85% of Ewing cases are caused by a translocation between the EWS gene on chromosome 22 and the FLI1 gene on chromosome 11 [t(11;22)(q24;q12)]. The fusion EWS-FLI1 gene codes for a chimeric transcription factor which activates and suppresses expression of a diverse array of target genes, and is an enticing candidate for therapeutic investigation. EWS-FLI1 activity can be readily observed in a homozygous transgenic zebrafish model, in which the fusion gene is inserted downstream of the Microphthalmia-Associated Transcription Factor promoter, localizing EWS-FLI1 expression to melanocytes derived from the neural crest. These fish present with an increased melanocyte count on the dorsum of the head compared to wild type. We hypothesized that compounds which suppress EWS-FLI1 activity will prevent the formation of this phenotype in homozygous zebrafish larvae. A high-throughput chemical screen was performed using two libraries of FDA approved compounds. One compound was found to significantly reduce melanocyte count in EWS-FLI1 homozygous zebrafish compared to unexposed homozygous controls (p < 0.0001) in a dose-dependent manner. Furthermore, treated homozygous larvae displayed melanocyte phenotype similar to that of untreated wild type controls. From these results, we conclude that this compound interferes with EWS-FLI1 activity in the mitf:EWS-FLI1 homozygous zebrafish model. Further testing on Ewing Sarcoma cell lines will determine the potential significance of this compound as a specific inhibitor of tumor growth.Item Identification of EWS-FLI1 Regions Necessary for Ewing Sarcoma Proliferation(December 2021) Bremauntz Enriquez, Alberto; Amatruda, James F.; McFadden, David G.; McKnight, Steven L.; Yu, HongtaoEwing sarcoma is pediatric bone malignancy defined by a translocation between EWS and ETS family transcription factor. EWS-FLI1 (EF) is the most common translocation and codes for a novel transcription factor that combines the N-terminus of EWS, which contains LC domain comprised of tyrosine rich peptide repeats, and C-terminal portion of FLI1, which contains the ETS DNA binding domain. EF is a key transcriptional regulator known to both activate and repress genes. While understanding of the molecular mechanism by which EF controls transcription have become clearer, targeted therapeutic interventions against EF or its transcriptional program have yet to make clinical impact. This is due in part to a poor understanding of how the N-terminus of EWS is contributing to the oncogenic program and a disparate range of reported effects after EF depletion on Ewing sarcoma cells. This report shows the adaptation of two inducible degron systems, Small Molecule Assisted Shut-Off (SMASh) and Auxin-inducible degron (AID), into the endogenous locus of EF in a series of Ewing sarcoma cell lines to define the phenotype of EF depletion. Across multiple cell line and degradation mechanisms, EF depletion in Ewing sarcoma cells leads to decreased cell proliferation through G1/S arrest that can be rescued through re-expression of EF. Having established a baseline for EF depleted cells, I developed a proliferation-based assay to test the functionality of mutant EF constructs on their ability to drive proliferation in the setting of endogenous EF depletion. I tested a series of EF truncations, with single or multiple exon deletions in the EWS portion of the translocation. Expression of EF constructs with loss of any single exon was tolerated and allowed for continued proliferation, but loss of at least exons 1-4 on the N-terminus and loss of exons 5-7 from the C-terminus resulted in non-functional EF constructs. Given that there appear to be redundant elements within the N-terminus of EF, I tested truncated and mutant version of a minimal rescue construct containing only exon 1-5 of the N-terminus of EF. Mutation of only 3 tyrosines to serine within the minimal construct was sufficient to prevent proliferation in Ewing cell lines.Item Investigating the Functional Contributions and Tumorigenic Potential of Cancer/Testis Antigens and Their Interacting Partners(2019-07-29) Gallegos, Zachary Regino; Tagliabracci, Vincent S.; Whitehurst, Angelique Wright; Cobb, Melanie H.; Amatruda, James F.Cancer/Testis (CT) antigens are proteins whose presence is normally restricted to gametogenic cells but are aberrantly activated in cancer. Due to the normal expression in immune-privileged sites, CT antigens can induce an immune response when expressed elsewhere. As a result, several studies have investigated CT antigens' expression patterns in cancer and their use as immunotherapy targets but not their functional contributions. Here I describe my work on the CT antigen FATE1 in Ewing sarcoma and the CT antigen gain-of-function screen using immortalized human colonic epithelial cells (HCEC). Ewing sarcoma is characterized by a pathognomonic chromosomal translocation that generates the EWSR1-FLI1 chimeric transcription factor. The transcriptional targets of EWSR1-FLI1 that are essential for tumorigenicity are incompletely defined. Here, I found that EWSR1-FLI1 modulates the expression of FATE1 and associates with the GGAA repeats within FATE's proximal promoter. Importantly, I found that FATE1 is required for survival and anchorage-independent growth in Ewing sarcoma cells. Our data suggests FATE1 attenuates the accumulation of BNIP3L and IB, actions that appear to be mediated by the E3-ligase RNF183. Additionally, I found FATE1 regulates autophagy and mitochondrial fission/fusion dynamics. Overall, I propose that engaging FATE1 function can permit the bypass of cell death mechanisms that would otherwise inhibit tumor progression. Previously, our group has demonstrated that several CT antigens performed functional roles in various cancers. Through utilizing the HCEC cell lines, I found that a subset of tested CT antigens increased soft agar colony formation, including the kinase TSSK6. Interestingly, I found that TSSK6 activates WNT signaling, a pathway known to be aberrantly activated in colorectal cancer and is important for cancer cell viability. Further investigation revealed that several of TSSK family members and TSSK6 activating chaperone, TSACC, are enriched in cancer and are important for tumor cell viability. Overall, these studies demonstrate that CT antigens can be actively expressed in cancer by oncogenic transcription factors and have functional roles that promote tumorigenesis.