Desmoplastic small round cell tumor is dependent on the EWS-WT1 transcription factor

Abstract

Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive soft-tissue malignancy with a poor overall survival and no effective therapeutic options. The tumor is believed to be dependent on the continued activity of the oncogenic EWS-WT1 transcription factor. However, the dependence of the tumor on EWS-WT1 has not been well established. In addition, there are no studies exploring the downstream transcriptional program across multiple cell lines. In this study, we have developed a novel approach to selectively silence EWS-WT1 without impacting either wild-type EWSR1 or WT1. We show a clear dependence of the tumor on EWS-WT1 in two different cell lines, BER and JN-DSCRT-1. In addition, we identify and validate important downstream target pathways commonly dysregulated in other translocation-positive sarcomas, including PRC2, mTOR, and TGFB. Surprisingly, there is striking overlap between the EWS-WT1 and EWS-FLI1 gene signatures, despite the fact that the DNA-binding domain of the fusion proteins, WT1 and FLI1, is structurally unique and classified as different types of transcription factors. This study provides important insight into the biology of this disease relative to other translocation-positive sarcomas, and the basis for the therapeutic targeting of EWS-WT1 for this disease that has limited therapeutic options.

Desmoplastic Small Round Cell Tumor: A Review of Main Molecular Abnormalities and Emerging Therapy

“…stromal production, inflammatory cells infiltration, specially macrophage chemotaxis and neo-angiogenesis [14], induces proliferation and is a chemo-attractant to fibroblasts and endothelial cells [14] [15]. The development and growth of DSRCT is primarily dependent on this translocation product [12]. The EWS-WT1 transcription factor translocation produces a chimeric protein that induces the expression of PDGFRα that can explain the histological characteristics of DSRCT that is marked by profuse stromal proliferation and increased vascular density [16] (Figure 2).…”

“…ASCL1 is an important player in mediating multiple WT1-responsive elements, suggesting that neural differentiation pathway could be tested as therapeutic agents for DSRCT [74]. A recent work described the dependence of EWS-WT1 in DSRCT survival [12]. Silencing EWS-WT1 causes proliferation loss, growth arrest and gene expression analysis indicates a repression of estrogen signaling and highlight therapeutic genetic vulnerabilities, such as FGFR4, JAK3, mTOR, PDGF, ERG, and TGFB1 genes [12].…”

“…A recent work described the dependence of EWS-WT1 in DSRCT survival [12]. Silencing EWS-WT1 causes proliferation loss, growth arrest and gene expression analysis indicates a repression of estrogen signaling and highlight therapeutic genetic vulnerabilities, such as FGFR4, JAK3, mTOR, PDGF, ERG, and TGFB1 genes [12]. Another study that evaluated potential therapeutic targets performed RNA sequencing of 12 tumor samples from pediatric patients with DSRCT found high expression of IGF2, FGFR4, CD200 and CD276, the latter two molecules are candidates for immune checkpoint inhibitor therapy [75] In terms of therapy, the first use of JN-DSRCT-1 cells was to test de effect of rapamycin induced in inducing apoptotic death [76].…”

“…The cell has tumorigenic capacity and the histology of heterotransplanted tumors in SCID mice maintains the characteristics of the original DSRCT, including the expression of immunohistochemical markers (vimentin, desmin, CD57, among others), a t(11; 22) translocation (p13; q12 ) and presence of EWS-WT1 fusion[69]. JN-DSRCT-1 cells are being used in a several studies that help to unveil DSRCT biology, specially the role of EWS-WT1 fusion protein and also to identify targets for therapeutic interventions[12,70] As mentioned before, EWS-WT1 translocation is the major driver in DSRCT and plays many roles in tumor biology that have the potential to be used as therapeutic targets. As already described in other studies, EWS-WT1 gene underwent RNA splicing and one variant lacks three amino-acids and was named EWS-WT1(-KTS) due the absence of Lys-Thr-Ser residues[71].…”

“…This activity is also observed in EWS-WT1 fusion protein, trabectedin reduces its binding on its target gene promoters and, thus, affects EWS-WT1-dependent gene expression in JN-DSRCT-1 cells[80]. Recently, the combination of PARP inhibitor olaparib with the alkylating agent temozolomide was tested in JN-DSRCT-1 cells in vitro and in vivo and the results indicates that the combination have synergistic effects upon cell viability, inducing cell cycle arrest which progress to apoptosis induction, causing tumor reduction[70].Additionally to JN-DSRCT-1 cells, Markides and collaborators established more DSRCT cell lines, including BER lineage that also presents EWS-WT1 fusion protein and have similar behavior of JN-DSRCT-1[12,82]. Together, this evidence shows the importance of obtaining tumor models to accelerate preclinical research, bring possibilities for investigating new therapeutic approaches for this rare but lethal malignancy.…”