The role of WSB-1 as a BRCAness biomarker in breast cancer

Li, Chun

Abstract

Background
Radiotherapy currently has become one of the major therapeutic approaches in the treatments for cancers. However, hypoxia presents a significant challenge to the effectiveness of radiotherapy and is associated with radio-resistance. Previous studies have shown that hypoxia can lead the alteration of DNA damage response pathways and genomic instability, which correlates with increased therapeutic resistance. Metastatic breast cancer is one of the most aggressive types of breast cancer and, unfortunately, with limited options regarding therapeutic strategies and reliable predictive biomarkers. Recent studies shown that DNA repair-deficient cancers, including BRCA1/2-deficient breast cancers, are sensitive to PARP inhibitors (PARPi), a phenotype described as BRCAness. We have previously found that the hypoxia-inducible factor WSB-1 is associated with increased breast cancer metastasis. However, its role in the DDR remains unclear. In this study, we evaluated the role of WSB-1 in DDR regulation in hypoxia in breast cancer.
Methodology
RNA-Sequencing analysis was performed after WSB-1 depletion on the MDA-MB-231 cell line to evaluate its impact on DDR pathways. Interesting hits were validated in vitro at mRNA and protein level using WSB-1 siRNA or overexpression. Moreover, the impact of WSB-1 on DNA damage response was evaluated by DNA damage biomarkers γH2AX and 53BP1 foci, cell cycle progression, as well as chromosome instability. In addition, in silico analyses of patient gene expression datasets were also performed for WSB1 vs DNA repair. Finally, sensitivity of DDR inhibitors (DDRis) such as PARP inhibitors (PARP1i), ATM inhibitors (ATMi), and ATR inhibitors (ATRi), were investigated using viability assays alongside WSB-1 expression modulation, either as single agents or in combination with radiotherapy.
Results
Transcriptome-wide RNA-Seq analysis showed that WSB-1 depletion was associated with upregulation of various DDR pathways. These were validated at mRNA and protein level in vitro after WSB-1 depletion, and reciprocally, WSB-1 overexpression downregulated these DDR factors. Further, γH2AX and 53BP1 foci were increased when overexpressed WSB-1 and decreased after WSB-1 depletion after IR under normoxia and hypoxia. cell cycle arrest and potentially chromosome instability were also observed when overexpressed WSB-1. Moreover, WSB1 expression correlation analysis in breast cancer patient gene expression datasets also been showed inversely correlated with DNA repair gene signature. Finally, it was observed that WSB-1 overexpression increased Olaparib (PARPi), KU-55933 (ATMi), and VE-822 (ATRi) sensitivity in vitro.
Conclusions
Our results show that WSB-1 expression in hypoxic breast cancer is associated with modulation of DDR factor expression. Furthermore, WSB-1 overexpression led to increased PARPi, ATMi, ATRi sensitivity alone or combined with radiation sensitivity in vitro. Therefore, we propose that elevated WSB-1 expression could be a potential BRCAness biomarker in metastatic breast cancer and could promote increased sensitivity to DDR targeted therapies.

Citation

Li, . C. The role of WSB-1 as a BRCAness biomarker in breast cancer. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4436228

• Thesis Type: Thesis
• Deposit Date: Nov 10, 2023
• Publicly Available Date: Dec 15, 2023
• Keywords: Medicine
• Public URL: https://hull-repository.worktribe.com/output/4436228
• Additional Information: Centre for Biomedical Sciences; University of Hull
• Award Date: Nov 7, 2023