EWSR1-WT1 fusion

P2, N=24, Recruiting, Memorial Sloan Kettering Cancer Center | Trial completion date: Mar 2024 --> Mar 2025 | Trial primary completion date: Mar 2024 --> Mar 2025

BLK inhibition and knockdown reduced CSC-like properties, including abrogation of tumorsphere formation and stemness marker expression. Importantly, BLK knockdown reduced DSRCT CSC-like cell chemoresistance, making its inhibition a promising target for future combination therapy.

It shows the immunohistochemical features of DSRCT and documentation of EWSR1-WT1 fusion.A potential diagnostic pitfall is exerted when evaluating liver biopsy, in which DSRCT is a great mimicker and may be easily confused with more common liver malignancies of childhood, such as hepatoblastoma, calcifying nested stromal-epithelial tumor, undifferentiated embryonal sarcoma, and other small round cell tumors, as well as the fibrolamellar variant of hepatocellular carcinoma. This distinction is critical because an accurate therapeutic approach requires a correct diagnosis.

We further found higher expression of the EWSR1-WT1 upregulated gene set in the recurrent tumor as compared to the primary tumor and lower expression of the EWSR1-WT1 downregulated gene set, suggesting the EWSR1-WT1 fusion continues to play a prominent role in recurrent tumors. The identified pathways including upregulation of DNA repair and downregulation of immune system function may help explain DSRCT's high rate of recurrence and can be utilized to improve the understanding of DSRCT biology and identify novel therapies to both help prevent recurrence and treat recurrent tumors.

We further develop the first in vitro DSRCT CSC model which forms tumorspheres, expresses increased levels of stemness markers (SOX2, NANOG, KLF4, and OCT4), and resists doxorubicin chemotherapy treatment. This model is an important addition to the DSRCT tool kit and will enable investigation of this critical DSRCT subpopulation. Despite lower sensitivity to chemotherapy, the DSRCT CSC model remained sensitive to knockdown of the EWSR1-WT1 fusion protein, suggesting that future therapies directed against this oncogenic driver have the potential to treat both DSRCT bulk tumor and CSCs.

We analyzed the antitumor activity of the following drugs as single-agent: doxorubicin (2.5mg/Kg), pazopanib (100mg/Kg), larotrectenib (50mg/Kg), vinorelbine (5mg/Kg), eribulin (1mg/Kg), irinotecan (2.5mg/Kg) and trabectedin (0.15mg/Kg). Findings of this preclinical study strongly support to further investigate irinotecan in combination with either trabectedin or eribulin in DSRCT. The irinotecan-trabectedin combination appears particularly promising, and deserves to be investigated in prospective clinical studies. We plan to test effectiveness of lurbinectedn, a novel synthetic agent derived from trabectedin with a similar mechanism of action, which is currently under investigation in combination with irinotecan in sarcomas.

Treatment of JN-DSRCT cells with the PI3K inhibitor alpelisib and mTOR inhibitor temsirolimus reduced cell proliferation. In addition, the low mutation burden was associated with an immune-cold state in DSRCT. Together, these data reveal multiple genomic and immune features of DSRCT and suggest therapeutic opportunities in patients.

CCK-8 assay demonstrated an increased chemoresistance for tumorspheres versus normal adherent culture especially for doxorubicin, which was confirmed by reduction in PARP cleavage...BLK knockdown reduced CSC-like properties including abrogation of tumorsphere formation and reduction in the levels of SOX2 and NANOG. Together, this work for the first time identifies a CSC-like population in DSRCT and BLK as a potential DSRCT CSC target.

Inhibition of MERTK with the small-molecule inhibitor UNC2025 results in reduced proliferation of DSRCT cells in vitro, suggesting MERTK as a therapeutic target in DSRCT. This study underscores the usefulness of preclinical in vitro models for studying molecular mechanisms and potential therapeutic options.

Antagonizing EGFR function with shRNAs, small molecule inhibitors (afatinib, neratinib), or an anti-EGFR antibody (cetuximab) inhibited proliferation of DSRCT cells. Finally, treatment of mice bearing DSRCT xenografts with a combination of cetuximab and afatinib significantly reduced tumor growth. These data provide a rationale for evaluating EGFR antagonists in patients with DSRCT.

All pts underwent a multimodal approach including multiagent chemotherapy (ChT) (anthracyclines +/- alkylating agents +/- vinca alkaloids +/- etoposide +/- cisplatin +/- irinotecan), +/- surgery +/- HIPEC +/- abdominal radiation therapy (RT) +/- high-dose ChT. Although the outcome of pts with DSRCT is clearly unsatisfactory, in our series cure was likely achieved in a subset (16%; 25% in completely resected pts). All our long-term event-free survivors did not have liver/extra-abdominal extension, and all received multiagent ChT and complete surgical resection, while 3/5 had abdominal RT.

No abstract available

In combination with previous reports, our findings suggest pleiotropy of the EWSR1-WT1 fusion is possible and not limited to DSRCT. Subsets of non-DSRCT EWSR1-WT1 positive tumors may represent discrete entities, but further study is necessary.