Proteasome Addiction Defined in Ewing Sarcoma Is Effectively Targeted by a Novel Class of 19S Proteasome Inhibitors

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Ewing sarcoma is a rare bone cancer primarily affecting adolescents, driven by specific gene fusions.
• Current treatments for metastatic or recurrent Ewing sarcoma have poor outcomes, necessitating novel therapeutic strategies.
• Understanding the molecular vulnerabilities of Ewing sarcoma is crucial for developing effective treatments.

Purpose of the Study:

• To identify novel therapeutic targets and compounds for Ewing sarcoma through large-scale chemical screening.
• To investigate the mechanism of action of identified compounds and validate proteasome as a therapeutic target.
• To evaluate the efficacy of a novel therapeutic strategy in preclinical models of Ewing sarcoma.

Main Methods:

• High-throughput screening of 309,989 chemical compounds against Ewing sarcoma cells.
• Assessing compound-induced apoptosis and inhibition of proteasome deubiquitinating enzymes (USP14 and UCHL5).
• Genome-wide shRNA screening to identify Ewing sarcoma vulnerabilities and in vivo xenograft studies.

Main Results:

• Benzyl-4-piperidone compounds selectively inhibited Ewing sarcoma cell growth by inducing apoptosis.
• These compounds were found to disrupt 19S proteasome function by inhibiting USP14 and UCHL5.
• Proteasome and specific deubiquitinating enzymes (USP14, UCHL5) were confirmed as Ewing sarcoma vulnerabilities.
• Treatment with VLX1570, a related compound, significantly inhibited tumor growth in a mouse xenograft model.

Conclusions:

• 19S proteasome inhibitors represent a promising novel therapeutic strategy for Ewing sarcoma.
• Targeting USP14 and UCHL5 offers a potential approach to treat this aggressive bone cancer.
• Preclinical data support the further development of proteasome inhibitors for Ewing sarcoma patients.