BRCA1 orchestrates the response to BI-2536 and its combination with alisertib in MYC-driven small cell lung cancer

Area of Science:

• Oncology
• Molecular Biology
• Cancer Therapeutics

Background:

• Polo-like kinase 1 (PLK1) is a promising target for small cell lung cancer (SCLC) therapy.
• Factors influencing PLK1 inhibitor efficacy in SCLC remain largely unknown.
• BRCA1 is identified as a critical determinant of SCLC cell response to the PLK1 inhibitor BI-2536.

Purpose of the Study:

• To elucidate the mechanisms underlying SCLC response to PLK1 inhibition.
• To investigate the role of BRCA1 and MYC/MYCN signaling in SCLC sensitivity to BI-2536.
• To evaluate the therapeutic potential of combining BI-2536 with an Aurora kinase A (AURKA) inhibitor.

Main Methods:

• Utilized cell-based assays and in vivo xenograft models.
• Employed gene expression analysis, including Gene Set Enrichment Analysis (GSEA).
• Performed loss- and gain-of-function experiments to assess gene roles.

Main Results:

• Co-targeting AURKA with alisertib reduced BRCA1/RAD51 accumulation, induced DNA repair defects, and caused mitotic cell death in SCLC cells.
• Combination therapy of BI-2536 and alisertib impaired DNA repair and significantly inhibited tumor growth in vivo.
• MYC/MYCN signaling was found to be crucial for SCLC sensitivity to BI-2536 and combination therapy, with RAD51 expression correlating positively with PLK1/AURKA and inversely with drug efficacy.

Conclusions:

• The BRCA1 and MYC/MYCN-RAD51 axes are critical regulators of SCLC response to BI-2536 and alisertib.
• Combining BI-2536 and alisertib represents a potential novel therapeutic strategy for SCLC patients with MYC/MYCN activation.
• RAD51 manipulation significantly impacts BI-2536 efficacy and can restore MYC/MYCN-mediated sensitivity enhancement in SCLC.