BRCA1-associated RING domain-1 (BARD1) loss and GBP1 expression enhance sensitivity to DNA damage in Ewing sarcoma

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Ewing sarcoma is a primary bone tumor driven by fusion oncoproteins.
• Approximately 10% of Ewing sarcoma patients have germline variants in DNA damage repair genes.
• A germline mutation in BARD1 (BRCA1-associated RING domain-1) was recently identified in an Ewing sarcoma patient.

Purpose of the Study:

• To investigate the impact of BARD1 loss on Ewing sarcoma cell sensitivity to DNA damaging agents.
• To analyze the effect of BARD1 deficiency on the Ewing sarcoma transcriptome.
• To explore the role of GBP1 (guanylate-binding protein 1) in BARD1-deficient Ewing cells.

Main Methods:

• Utilized a novel patient-derived Ewing sarcoma cell line (PSaRC318) with a pathogenic BARD1 variant.
• Assessed sensitivity to poly(ADP-ribose) polymerase (PARP) inhibition and radiation therapy.
• Performed BARD1 depletion experiments in additional Ewing sarcoma cell lines.
• Conducted RNA-sequencing (RNA-seq) analysis to examine transcriptome changes.
• Investigated the contribution of GBP1 to DNA damage sensitivity in BARD1-deficient cells.

Main Results:

• Ewing sarcoma cells with a pathogenic BARD1 variant showed sensitivity to PARP inhibition.
• BARD1 depletion enhanced sensitivity to combined PARP inhibition and radiation in Ewing sarcoma cells.
• Loss of BARD1 led to the upregulation of GBP1 expression.
• GBP1 was demonstrated to contribute to the enhanced DNA damage sensitivity in BARD1-deficient Ewing cells.

Conclusions:

• Loss-of-function mutations in DNA damage repair genes like BARD1 significantly impact Ewing sarcoma treatment response.
• BARD1 deficiency sensitizes Ewing sarcoma cells to PARP inhibition and radiation, partly through GBP1 upregulation.
• Targeting DNA damage response pathways may offer novel therapeutic strategies for Ewing sarcoma patients with BARD1 variants.