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

Area of Science:

• Oncology
• Molecular Biology
• Epigenetics

Background:

• Lysine specific demethylase 1 (LSD1), encoded by KDM1A, is overexpressed in Ewing sarcoma, correlating with poor prognosis.
• LSD1 and the EWSR1::FLI1 oncoprotein interact genome-wide, implicating LSD1 in Ewing sarcoma progression.
• Previous therapeutic targeting of LSD1 yielded mixed results, with unclear mechanisms of action.

Purpose of the Study:

• To elucidate the enzymatic and nonenzymatic roles of LSD1 in Ewing sarcoma transcriptional regulation.
• To identify specific genes regulated by LSD1 in Ewing sarcoma.
• To evaluate the efficacy of LSD1 inhibition strategies beyond standard cytotoxicity assays.

Main Methods:

• Utilized multiple depletion methods across various Ewing sarcoma cell lines.
• Performed genome-wide analysis to identify LSD1-regulated genes.
• Employed enzymatic and nonenzymatic LSD1 activity assays.
• Investigated drug response using 2D cytotoxicity and proliferation assays with an irreversible inhibitor (OG-L002).

Main Results:

• Identified a core set of 22 genes commonly repressed by LSD1, impacting synapse function and e-cadherin.
• Observed derepression of these genes upon LSD1 loss, consistent across all tested cell lines.
• Differentiated gene sets regulated by enzymatic versus nonenzymatic LSD1 activity.
• Found repression of e-cadherin target genes to be mediated by nonenzymatic LSD1 activity.
• Demonstrated that standard 2D assays may be insufficient for assessing Ewing sarcoma response to LSD1 inhibition.

Conclusions:

• LSD1 exerts both enzymatic and nonenzymatic functions in Ewing sarcoma, contributing to disease progression.
• Nonenzymatic roles of LSD1, such as regulating e-cadherin, are crucial and represent potential therapeutic targets.
• Standard cytotoxicity assays may not accurately reflect therapeutic responses to LSD1 inhibitors in Ewing sarcoma.
• Further investigation into the noncanonical functions of chromatin regulatory enzymes is warranted.