DSRCT # Overview DSRCT is invariably defined by a  [[Chromosomal Translocation]] involving chromosomes 11 and 22 leading to a fusion of two unrelated genes, [[EWS]] and [[WT1]], into a single [[chimeric gene]]. ## Morphology Important characteristic - Undifferentiated. Primitive cells. "***small, round and relatively undifferentiated primitive cells with scant cytoplasm" High nuclear/cytoplasmic (N/C) ratio Multiphenotypic differentiation Heterogenous Tumor mass - only ?10-20% tumor cells containing EWS-WT1 fusion? Pathology outlines slides - ![[Images Repository/DSRCT Pathology, Morphology/DSRCT_Slide1_PathologyOutlines.png|620]] *<font color="#7f7f7f">DSRCT Tumor cells with round or oval nuclei with dispersed chromatin and inconspicuous nucleoli.</font>* ![[DSRCT_Slide1_PathologyOutlines 1.png|520]] *Tumor cells arranged in nests and thin trabeculae separated by desmoplastic stroma.* ![[DSRCT_Slide1_PathologyOutlines 3.png.png|420]] *Uniform small round cells with small nuclei, scant cytoplasm and indistinct cytoplasmic borders.* ## DNA: Chromosomal Translocation - EWSR1-WT1 Fusion Normally, during cell division DNA is copied in the form of chromosomes. It is during this process that a chromosomal translocation occurs, fusing Chr11 to Chr22. This oncogenic event presumably originates in a progenitor cell and further cell divisions contain the mutation. t(11;22)(p13;q12) * Insert FISH visual The fusion protein product itself - implications Implications of chromosomal translocation - gene access etc > [!quote] > The most fundamental difference between compounds of low molecular weight and macromolecular compounds resides in the fact that the latter may exhibit properties that cannot be deduced from a close examination of the low molecular weight materials. Not very different structures can be obtained from a few building blocks; but if 10,000 or 100,000 blocks are at hand, the most varied structures become possible, such as houses or halls, whose special structure cannot be predicted from the constructions that are possible with only a few building blocks... > > Thus, ***a chromosome can be viewed as a material whose macromolecules possess a well defined arrangement***, like a living room in which each piece of furniture has its place and not, as in a warehouse, where the pieces of furniture are placed together in a heap without design. > > [**Hermann Staudinger, 1975**](https://todayinsci.com/S/Staudinger_Hermann/StaudingerHermann-Quotations.htm) ![[Chimeric Gene Fusion.png]] Chromosomal Translocations are found in many different cancers. ? The EWSR1 gene is particularly promiscuous as it is a fusion partner in a large list of different sarcomas, such as in Ewing's where there is a fusion of EWSR1-FLI1. ## Cell of Origin > [!info]+ [[Cell of Origin & Implications]] > Speculated that the initial oncogenic fusion event occurs in a specific cell type and environment which enables the cell to survive and proliferate. DSRCT characteristically shows a multiphenotypic lineage which complicates conclusively identifying a specific cell of origin. > ***Potential cells of origin in DSRCT***: > ? > Undifferentiated progenitor cells > ?Neural Crest Origin, Neuroectdermal Cell > ?MDSC's In the lab, some studies have shown that after inducing the fusion protein EWS-WT1 only certain cell types can then survive the toxic effect to then become proliferative. Adding to this, some factors may contribute to a 'balance' of fusion positive to non-fusion positive cells in the tumor mass, as if too many cells contain the fusion it may not be able to survive, proliferate, and thrive. ### ETV6 and Ewing Sarcoma example Evidence can be been seen for this in Ewing's Sarcoma and the ETV6 gene function- ETV6 mechanism in ES being pro tumorigenic by suppressing EWS-FLI1 function enough to provide a survival advantage. ## Undifferentiated, Primitive cell state Heterogeneity. Poorly differentiated ## Transcription Factor Proteins - General Overview > [!Abstract]+ DSRCT Study <font color="#002060">**A novel EWS-WT1 gene fusion product in desmoplastic small round cell tumor is a potent transactivator of the insulin-like growth factor-I receptor (IGF-IR) gene [Cancer Letters, 2007](https://www.sciencedirect.com/science/article/abs/pii/S030438350600190X)** </font> > > "Most biochemical and genetic evidence supports the notion that the translocation event in DSRCT **abolishes the RNA-binding activity of EWS**, **as well as the transcriptional repression activity of WT1,** and generates an oncogenic EWS-WT1 fusion protein." > Prototypical EWS-WT1 fusion proteins are capable of binding and transactivating WT1 molecular targets, including the IGF-IR gene, by virtue of the WT1-derived zinc-finger domain [^10](https://www.sciencedirect.com/science/article/pii/S030438350600190X#bib10), [20](https://www.sciencedirect.com/science/article/pii/S030438350600190X#bib20), [34](https://www.sciencedirect.com/science/article/pii/S030438350600190X#bib34). Footnote example [^1] ## Transcriptional activation of aberrant genes > The expression of the oncogenic chimeric EWSR1-WT1 protein has been shown to lead to transcriptional activation of at least 35 target genes, including those encoding growth factors and their receptors such as PDGFa, IGF1-R, and EGFR, and transcriptional regulators such as c-MYC and TP53. TSO500 Report PMID: 9354795, 29225486, 30486883 ## [[EWSR1 Gene]]: Chromosome 22 EWS is important to understand, being the fusion partner in a broad range of different tumor types. It is the highly potent N-terminal domain that gives the resulting fusion protein transcriptional activation (and repression) abilities. Given the wide variety of EWS-fusion driven cancers it is reasonable to assume that the conserved portion of the EWS transcript contributes to the oncogenic process. ### Normal (Wild Type) ESWR1 function Ubiquity? Low? Is it usually present in different types of normal cells? WT1 crucial in fetal development and kidney. >EWSR1 belongs to the TET family of proteins, and acts as a multifunctional molecule in various cellular processes, including gene expression, cell signaling, RNA processing and transport, and regulation of microRNA (miRNA) [[15](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR15 "Kovar H. Dr. Jekyll and Mr. Hyde: The Two Faces of the FUS/EWS/TAF15 Protein Family. Sarcoma. 2011;2011:83747"),[16](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR16 "Paronetto MP. Ewing sarcoma protein: a key player in human cancer. Int J Cell Biol. 2013;2013:642853."),[17](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR17 "Lee J, Nguyen PT, Shim HS, Hyeon SJ, Im H, Choi MH, et al. EWSR1, a multifunctional protein, regulates cellular function and aging via genetic and epigenetic pathways. Biochim Biophys Acta Mol Basis Dis. 2019;1865(7):1938–45."),[18](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR18 "Kim Y, Kang YS, Lee NY, Kim KY, Hwang YJ, Kim HW, et al. Uvrag targeting by Mir125a and Mir351 modulates autophagy associated with Ewsr1 deficiency. Autophagy. 2015;11(5):796–811."),[19](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR19 "Ouyang H, Zhang K, Fox-Walsh K, Yang Y, Zhang C, Huang J, et al. The RNA binding protein EWS is broadly involved in the regulation of pri-miRNA processing in mammalian cells. Nucl Acids Res. 2017;45(21):12481–95.")]. >In addition, EWSR1 interacts with Y-box-binding protein 1 (YBX1), which potently induces MYC and BCL2 [[21](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR21 "Park JH, Kang HJ, Kang SI, Lee JE, Hur J, Ge K, et al. A multifunctional protein, EWS, is essential for early brown fat lineage determination. Dev Cell. 2013;26(4):393–404."), [22](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR22 "Kuwano M, Shibata T, Watari K, Ono M. Oncogenic Y-box binding protein-1 as an effective therapeutic target in drug-resistant cancer. Cancer Sci. 2019;110(5):1536–43.")]. [EWSR1 overexpression is a pro-oncogenic event in multiple myeloma \| International Journal of Hematology (2020)](https://link.springer.com/article/10.1007/s12185-020-03027-0#ref-CR15) ## [[WT1 Gene]]: Chromosome 11 ## Chimeric Fusion Protein: EWS-WT1 One purported mechanism is the creation of a RNA binding protein (transcription factor) which interacts with the genome to support an oncogenic program in various ways. ?Promoter binding sites - Nature study 2024 IGF EWS-WT1 Fusion protein purported binding sites: IGF1R > Consistent with the postulate that the EWSR1-WT1 fusion protein is capable of modulating transcription of target genes containing WT1 binding motifs, we have shown that the chimera can recognize and transactivate the _IGF1R_ promoter in transient transfection assays (see below) [[65](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5817802/#CR65), [66](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5817802/#CR66)]. > [Oncogenic fusion proteins adopt the insulin-like growth factor signaling pathway (BMC Mol. Cancer 2018)](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5817802/) ### Fusion protein ubiquity / heterogeneity ## Heterogeneity ## +- KTS Alternate Splicing ## Phase transition properties ## Gene Access ## Nuclear Proteins and Difficulty for Treatment >Since EWS/FLI1 expression is restricted to tumor cells, it represents an ideal therapeutic target. However, it acts as transcription factor, **which in most cases are considered undruggable because of lack of enzymatic activity and their direct pharmacological inhibition is still challenging.** Indeed, EWS/FLI1 behaves as intrinsically disordered protein and so far cannot be directly targeted by small molecules in a classical sense. >Targeting IGFR1-PI3K-AKT-mTOR signaling has shown promising results in Ewing sarcoma [[42](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R42), [44](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R44), [45](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R45), [57](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R57)]. Our demonstration that inhibition of the pathway directly impairs expression of the fusion protein itself provides additional support for its therapeutic development [[58](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R58)]. Most promising appear to be combinations with other targeted agents that might modulate EWS/FLI1 activity such as YK-4–279 [[59](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/#R59)] or epigenetic modifiers that can potentially further suppress transcription of the fusion protein. Hence, elucidating the transcriptional regulation of EWS/FLI1 might provide additional molecular targets for this devastating disease. [PI3K/AKT signaling modulates transcriptional expression of EWS/FLI1 through specificity protein 1 | Oncotarget 2015](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745699/) [^1]: EDdvhj