Abstract 708: Targeting aurora kinase B (AURKB) as a radiosensitizing strategy in syngeneic models of triple negative breast cancer (TNBC)

Abstract Purpose: Triple negative breast cancer (TNBC) is an aggressive breast cancer (BC) subtype with few treatment options. Radiation therapy (RT) is a mainstay therapy for the treatment of BC, but local recurrence following RT therapy is common. Consequently, decreasing local recurrence in patients with TNBC is a critical clinical need. Prior work demonstrated that AURKB is overexpressed in TNBC, and over-expression correlates with poor prognosis. Here, we examined the effects of AURKB inhibition as a novel radiosensitizing strategy in syngeneic TNBC models. Methods: Cell viability assays were used to determine the half-maximal inhibitory concentrations (IC50) of the AURKB inhibitors Barasertib-HQPA and SP-96 72 hours post treatment. Clonogenic survival assays were used to assess the radiosensitivity of TNBC murine cell lines to AURKB inhibition. In these assays, AURKB inhibitors were delivered at sub-IC50 concentrations 24 hours prior to RT, and radiation enhancement ratios (rERs) were calculated. Immunofluorescent microscopy using DAPI stain assessed micronuclei. Propidium iodide staining to assess aneuploidy was completed via flow cytometry. To assess the radiosensitizing effects of AURKB inhibition in vivo, the 4T1 syngeneic TNBC cell line was injected bilaterally into Balb/c mice and treated with Barasertib and RT. Tumor volume was recorded twice weekly throughout the study. Results: Aurora kinase B inhibitors (500-750 nM Barasertib-HQPA, 100-200 nM SP-96) delivered 24 hours prior to radiation therapy induced radiosensitization in the murine TNBC cells 4T1 (rER: 1. 24-1. 56) and Py8119 (rER: 1. 51-1. 72). Mechanistically, combined AURKB inhibition and RT significantly increased micronuclei formation in 4T1 cells 24 hours after RT compared to vehicle control (p0. 0001). Furthermore, combined AURKB inhibition and RT induced aneuploidy in murine TNBC cell lines 24 hours after radiation therapy compared to vehicle control. Combined AURKB inhibition (Barasertib 25 mg/kg, IP) and RT (8 Gy RT in 1 fraction) significantly decreased tumor volume compared to mice that had received vehicle control (777 ± 61 mm3 vs 1623 ± 126 mm3; p 0. 0001). Conclusion: AURKB inhibition induces radiosensitization in syngeneic models of TNBC and leads to increased micronuclei and aneuploidy, suggesting a mechanism of sensitization. These results suggest that AURKB is a potential radiosensitizing strategy for the treatment of triple negative disease. Ongoing studies are further refining the underlying mechanisms of AURKB inhibition and RT on the antitumoral immune response. Citation Format: Kassidy M. Jungles, Zhuwen Wang, Caroline Bishop, Cydnee Wilson, Meilan Liu, Jadyn James, Michael Green, James M. Rae, Corey W. Speers, Lori J. Pierce. Targeting aurora kinase B (AURKB) as a radiosensitizing strategy in syngeneic models of triple negative breast cancer (TNBC) abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 708.