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Screening for DAX1/EWS-FLI1 functional inhibitors identified dihydroorotate dehydrogenase as a therapeutic target for
Miwa Watanabe1,2, Hiromichi Kosaka1, Masamori Sugawara1
1Research and Development Division, Kyowa Kirin Co., Ltd., Shizuoka, Japan.
Objective:
EWS-FLI1 is the most common oncogenic fusion protein in Ewing's sarcoma family tumors (ESFTs). DAX1, an orphan member of the nuclear receptor superfamily, is up-regulated by EWS-FLI1 and plays a key role in the transformed phenotype of ESFTs.
Methods:
To discover a functional inhibitor of DAX1 and EWS-FLI1, we screened small-molecular inhibitors using a DAX1 reporter assay system.
Results:
K-234 and its derivatives, which were dihydroorotate dehydrogenase (DHODH) inhibitors, showed inhibitory effects in the reporter assay. K-234 inhibited the growth of Ewing's sarcoma with various fusion types, and K-234 derivatives altered the expression of EWS-FLI1-regulated genes. The DAX1 expression had no effect on the growth inhibitory effect of the K-234 derivatives, while DHODH overexpression or uridine treatment attenuated their inhibitory effects, suggesting that inhibition by K-234 derivatives occurs through DHODH inhibition. An in vivo study showed that a K-234 derivative clearly inhibited tumor growth in an Ewing's sarcoma xenograft mouse model.
Conclusion:
Taken together, the present results suggest that DHODH inhibitors can inhibit the function of DAX1/EWS-FLI1 in ESFTs and might be a therapeutic agent with potent anti-tumor activity for Ewing's sarcoma patients.
Insights
Dihydroorotate dehydrogenase (DHODH) inhibitors, like K-234, show promise in treating Ewing sarcoma by targeting the EWS-FLI1 oncoprotein and DAX1. These DHODH inhibitors effectively reduced tumor growth in preclinical models.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Ewing's sarcoma family tumors (ESFTs) are driven by the EWS-FLI1 fusion protein.
- DAX1, a nuclear receptor, is upregulated by EWS-FLI1 and crucial for ESFTs' transformed phenotype.
Purpose of the Study:
- To identify small-molecule inhibitors targeting DAX1 and EWS-FLI1 in ESFTs.
- To evaluate the therapeutic potential of identified inhibitors in preclinical models.
Main Methods:
- Screening of small-molecule inhibitors using a DAX1 reporter assay.
- Testing K-234 and its derivatives for anti-cancer activity in ESFT cell lines.
- Investigating the mechanism of action, including effects on DHODH and DAX1 expression.
- Evaluating efficacy in an in vivo Ewing sarcoma xenograft mouse model.
Main Results:
- K-234 and its derivatives, identified as dihydroorotate dehydrogenase (DHODH) inhibitors, demonstrated inhibitory effects in the reporter assay.
- K-234 inhibited the growth of various Ewing sarcoma types, while derivatives modulated EWS-FLI1-regulated gene expression.
- Inhibition by K-234 derivatives was confirmed to be through DHODH, as evidenced by attenuated effects with DHODH overexpression or uridine treatment.
- An in vivo study showed significant tumor growth inhibition in a xenograft model using a K-234 derivative.
Conclusions:
- DHODH inhibitors can effectively suppress DAX1/EWS-FLI1 function in ESFTs.
- These findings suggest DHODH inhibitors hold potential as potent therapeutic agents for Ewing sarcoma.
- Further development of DHODH inhibitors may offer a new treatment strategy for patients with Ewing sarcoma.
