Combined Aurora Kinase A and CHK1 Inhibition enhances radiosensitivity of triple-negative breast cancer through induction of apoptosis and mitotic catastrophe associated with excessive DNA damage

Purpose: There is an urgent need for biomarkers and new actionable targets to improve radiosensitivity of triple negative breast Cancer (TNBC) tumors. In this paper, we characterized the radiosensitizing effects and underlying mechanisms of combined Aurora Kinase A (AURKA) and Chk1 inhibition in TNBC.

Methods and materials: Different TNBC cell lines were treated with AURKA inhibitor (AURKAi, MLN8237) and CHK1i (CHK1i, MK8776). Cell responses to IR were then evaluated. Cell Apoptosis, DNA damage, cell cycle distribution, MAPK/ERK and PI3K pathways were evaluated in vitro. Transcriptomic analysis was performed to facilitate the identification of potential biomarkers. Xenograft and immunohistochemistry were carried out to investigate the radiosensitizing effects of dual inhibition in vivo. Finally, the prognostic effect of CHEK1/AURKA in TNBC samples in TCGA database and our center were analyzed RESULTS: AURKAi (MLN8237) induced overexpression of phospho-CHK1 in TNBC cells. Addition of MK8776 (CHK1i) to MLN8237 greatly reduced cell viability and increased radiosensitivity compared with either control or MLN8237 alone in vitro. Mechanistically, dual inhibition resulted in inducing excessive DNA damage by prompting G2/M transition as cell with defective spindles, leading to mitotic catastrophe and induction of Apoptosis after IR. We also observed that dual inhibition suppressed the phosphorylation of ERK, while activation of ERK with its agonist or overexpression of active ERK1/2 allele could attenuate the Apoptosis induced by dual inhibition with IR. Additionally, dual inhibition of AURKA and Chk1 synergistically enhanced radiosensitivity in MDA-MB-231 xenografts. Moreover, we detected that both CHEK1 and AURKA were overexpressed in TNBC patients and negatively correlated with patients' survival CONCLUSIONS: Our findings suggested that AURKAi in combination with CHK1i enhanced TNBC radiosensitivity in preclinical models, potentially providing a novel strategy of precision treatment for patients with TNBC.