Abstract 1115: Enhancing lung cancer sensitivity to chemotherapy, radiation, and chemo-radiation through inhibition of a mitotic checkpoint kinase BUB1

Abstract

Abstract Non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) represent two major subtypes of lung cancer, marked by challenging treatment resistance. Our study explores the inhibition of BUB1, a critical mitotic checkpoint kinase, in conjunction with radiotherapy and chemotherapy. This approach has the potential to overcome resistance, thus enhancing the efficacy of treatment and improving treatment outcomes for lung cancer patients. We analyzed BUB1 expression in lung cancer using TCGA datasets and patient tissue microarrays (TMAs). In vitro experiments used four NSCLC and two SCLC cell lines with BUB1 inhibitor (BAY1816032), Paclitaxel, Cisplatin and Olaparib. Cells were irradiated (2, 4, or 6 Gy), and assays measured proliferation, long-term effects, DNA damage, and repair. Bioinformatic analysis in NSCLC subtype, lung adenocarcinoma (LUAD) demonstrated marked overexpression of BUB1, correlated with cancer stage, tumor grade and survival. Lung cancer TMAs revealed elevated expression of BUB1 protein in SCLC that correlated with poorer survival. BUB1 inhibition (BUB1i) induced cytotoxicity in LUAD cell lines at micromolar concentrations, while nanomolar concentrations enhanced cell death significantly when combined with radiation. Furthermore, BUB1i sensitized LUAD cells to different classes of chemotherapy (Paclitaxel, Cisplatin), and PARP inhibitor (Olaparib) alone (chemo-sensitization) or with radiation therapy (chemo-radiosensitization). H2030 and H1975 demonstrated higher chemo-radiosensitization efficacy compared to A549, likely due to genetic differences, potentially including a p53 mutation that improves sensitivity by affecting DNA repair and cell cycle regulation. Preliminary investigations revealed DNA double-strand breaks, indicated by prolonged γH2AX foci, and the inhibition of the NHEJ DNA damage repair pathway after BUB1 ablation. Among SCLC cell lines, NCI-H1876 demonstrated higher radiosensitivity upon BUB1 ablation compared to NCI-H2198, potentially due to genetic differences/mutations affecting radiation response. The study highlights the potential of BUB1i in enhancing the sensitivity of NSCLC and SCLC cells to radiotherapy and chemotherapy and provide rationale to explore BUB1i as a novel approach to enhance lung cancer therapy in clinical trials. Citation Format: Shivani Thoidingjam, Sushmitha Sriramulu, Stephen L. Brown, Farzan Siddiqui, Benjamin Movsas, Shirish Gadgeel, Shyam Nyati. Enhancing lung cancer sensitivity to chemotherapy, radiation, and chemo-radiation through inhibition of a mitotic checkpoint kinase BUB1 [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(6_Suppl):Abstract nr 1115.