LSD1 Performs Demethylase-Independent and Context-Specific Roles in Ewing Sarcoma

Area of Science:

• Oncology
• Molecular Biology
• Epigenetics

Background:

• Lysine specific demethylase 1 (LSD1) is overexpressed in Ewing sarcoma, correlating with poor prognosis.
• LSD1 and EWSR1::FLI1 oncoprotein colocalize, indicating LSD1's role in driving sarcoma progression.
• Therapeutic targeting of LSD1 has shown mixed results, with unclear contributions of its enzymatic and nonenzymatic functions.

Purpose of the Study:

• To elucidate the enzymatic and nonenzymatic roles of LSD1 in Ewing sarcoma transcriptional regulation.
• To identify core genes regulated by LSD1 across multiple Ewing sarcoma cell lines.
• To evaluate the effectiveness of current assays in predicting Ewing sarcoma response to LSD1 inhibition.

Main Methods:

• Utilized multiple depletion methods across various Ewing sarcoma cell lines.
• Performed genome-wide analysis to identify LSD1-regulated genes.
• Employed 2D cytotoxicity and proliferation assays, alongside an irreversible inhibitor (OG-L002).

Main Results:

• Identified a core set of 22 genes commonly repressed by LSD1, impacting synapse and e-cadherin pathways.
• Demonstrated that LSD1 loss leads to early and sustained derepression of these core genes.
• Showcased nonenzymatic regulation of e-cadherin target genes, highlighting LSD1's noncanonical roles.
• Found that 2D cytotoxicity and proliferation assays may inadequately assess Ewing sarcoma response to LSD1 inhibition.

Conclusions:

• LSD1's nonenzymatic activity is critical for Ewing sarcoma progression, particularly in repressing e-cadherin targets.
• Understanding both enzymatic and nonenzymatic functions is essential for effective LSD1-targeted therapies.
• Current preclinical assays may not fully capture Ewing sarcoma response to LSD1 inhibition, necessitating novel assessment methods.