Gene therapy manipulates or modifies a gene that provides a new cellular function to treat or correct a pathological condition, such as cancer. The approach of using gene manipulation to modify patient’s cells to improve cancer therapy and potentially find a cure is gaining popularity. Currently, there are 12 gene therapy products approved by US-FDA, EMA and CFDA for cancer management, these include Rexin-G, Gendicine, Oncorine, Provange among other. The Radiation Biology Research group at Henry Ford Health has been actively developing gene therapy approaches for improving clinical outcome in cancer patients. The team was the first to test a replication-competent oncolytic virus armed with a therapeutic gene in humans, to combine this approach with radiation in humans, and to image replication-competent adenoviral gene expression/activity in humans. The adenoviral gene therapy products developed at Henry Ford Health have been evaluated in more than 6 preclinical studies and evaluated in 9 investigator initiated clinical trials treating more than100 patients. Two phase I clinical trials are currently following patients long term and a phase I trial for recurrent glioma was initiated in November 2022. This systematic review provides an overview of gene therapy approaches and products employed for treating cancer patients including the products developed at Henry Ford Health.

Triple-negative breast cancer (TNBC) is the most lethal type of breast cancer (BC). TNBC has a substantial risk of locoregional recurrence and is difficult to cure due to absence of molecular targets or intrinsic heterogeneity. As radiotherapy (RT) is crucial in the treatment of BC, there is a need to identify novel molecular targets for increasing the efficacy of radiation therapy. BUB1 (Budding uninhibited by benzimidazoles 1) is a serine/threonine kinase implicated in chromosomal segregation during mitosis. However, it is still uncertain how BUB1 contributes to radioresistance in TNBC. By performing expression analysis (Oncomine), we observed that BUB1 is overexpressed in BC and even more in TNBC, indicating that this overexpression could be a prognostic factor for TNBC. MTT assay in several TNBC cell lines demonstrated that pharmacological (BAY1816032) or genomic (CRISPR) ablation of BUB1 was cytotoxic. By performing clonogenic survival assays, we observed that BUB1 ablation led to clinically meaningful radiosensitization in TNBC cell lines (SUM159, MDA-MB-231, MDA-MB-468) with radiation enhancement ratios ranging from 1.1 - 1.38. In addition, we showed that inhibition of BUB1 kinase function is essential for the radiosensitization phenotype using siRNAs and CRISPR knockouts by depleting endogenous BUB1 and reintroducing wild-type (WT) or kinase-dead (KD) BUB1. We observed significant increase in tumor doubling time in SUM159 xenografts (mammary fat pads in CB17/SCID mice) when BUB1i was combined with RT (DT=29.6 vs 7.9 days). A reduction in Ki67 was observed in these tumors further confirming the effectiveness of combination treatment. The effect of BUB1 depletion on DNA double strand break repair was assessed using γ-H2AX foci formation assay, which revealed sustained increase in γ-H2AX foci following radiation in BUB1i-treated cells. Further, BLRR assays confirmed that BUB1i reduces non-homologous end joining (NHEJ) efficiency. Biochemical analyses showed that BUB1i increases and stabilizes radiation-induced DNAPKcs phosphorylation (S2056). To evaluate the recruitment of DDR proteins to the chromatin following irradiation (IR), soluble nuclear and the chromatin-enriched fractionation was performed which demonstrated that cells pretreated with BUB1i had increased recruitment of DDR proteins to chromatin suggesting that BUB1 may play a role in the initial recruitment of NHEJ proteins to DSBs. Our findings demonstrate that both genetic and pharmacological inhibition of BUB1 sensitizes TNBC cells to RT and that BUB1 mediated radiosensitization may occur through NHEJ pathway. Our results suggest that BUB1 may represent a novel molecular target for radiosensitization in women with TNBC. Citation Format: Sushmitha Sriramulu, Shivani Thoidingjam, Pin Li, Stephen L. Brown, Farzan Siddiqui, Benjamin Movsas, Michael Green, Corey Speers, Shyam Nyati. BUB1 inhibition radiosensitizes triple-negative breast cancer by targeting the DNA-damage repair pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2816.