Abstract 1829: Potentiating antitumoral type 1 interferon immune signaling in triple-negative breast cancer (TNBC) via combination treatment of Aurora kinase B (AURKB) inhibition and radiation therapy

Abstract Purpose: Triple-negative breast cancer (TNBC) is an aggressive BC subset that is less responsive to standard therapies resulting in the need for novel treatment options. Radiotherapy (RT) is common for treating TNBC patients; however, locoregional recurrence remains a clinical issue. Modulation of the antitumoral immune response may improve tumor control in TNBC. Type 1 interferon (T1IFN) is a crucial regulator of antitumoral immunity that can activate cytotoxic immune cells. AURKB is upregulated in TNBC patients, yet it is unknown whether AURKB modulates T1IFN signaling. While our preliminary data suggests that AURKB inhibition makes TNBC cells more sensitive to RT, the effects on T1IFN are unknown. Here, we examined the effects of combined RT and AURKB inhibition on T1IFN signaling in TNBC. Methods: The half-maximal inhibitory concentrations (IC50) were calculated using cell viability assays with the treatment of AURKB inhibitors Barasertib-HQPA and SP-96 in human and murine TNBC cells. Micronuclei formation was assessed using DAPI stain and immunofluorescent microscopy following treatment with AURKB inhibitors and RT. T1IFN signaling was assessed via a T1IFNβ-GFP reporter transfected into human TNBC cells, rt-qPCR for T1IFN response genes, and flow surface staining for T1IFN markers. For these studies, TNBC cells were pretreated with AURKB inhibitor 24 hours prior to RT and harvested five days later. Results: Aurora kinase B inhibitors (Barasertib-HQPA and SP-96) reduced cell viability in human and murine TNBC cells (IC50 values: 500 nm - 5 µM). AURKB inhibition delivered before RT induced micronuclei—a known ligand of T1IFN signaling—in TNBC cells. Further, sub-IC50 concentrations of AURKB inhibitors (25 nM Barasertib-HQPA, 100 nM SP-96) and RT (6 Gy in 1 fraction) induced T1IFN signaling in the human Cal-51 T1IFN reporter system (p<0.0001). This was also observed in combination with fractionated RT (2 Gy in 3 fractions), suggesting that combined AURKB inhibition and RT potentiate T1IFN (p<0.0001). Combined treatment (6 Gy RT + 10 nM Barasertib-HQPA) also induced expression of the T1IFN response genes Cxcl10 and PD-L1 in human TNBC BT549 cells compared to vehicle control (p<0.001). Further, AURKB inhibition and RT also potentiated the T1IFN markers PD-L1 and MHC1 in human and murine TNBC cells. Conclusion: AURKB inhibition and RT induces T1IFN signaling in human and murine TNBC cells. Combination treatment also induces micronuclei formation, suggesting an upstream mechanism for the observed T1IFN signaling. These data suggest that AURKB inhibition and RT may be a promising strategy for the treatment of TNBC and can modulate the tumor immune microenvironment. Further studies are warranted to examine the extended effects of this treatment in vivo and further implications on the antitumoral immune response. Citation Format: Kassidy M. Jungles, Caroline R. Bishop, Cydnee Wilson, Meilan Liu, Corey W. Speers, Lori Pierce, James Rae. Potentiating antitumoral type 1 interferon immune signaling in triple-negative breast cancer (TNBC) via combination treatment of Aurora kinase B (AURKB) inhibition and radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1829.