Abstract P4-08-07: Inhibition of the NUDT5 phosphatase suppresses the growth of triple-negative breast cancers
Authors: Qian Jing , Brown Powel 
Published: March 2023

Abstract
Inhibition of the NUDT5 Phosphatase Suppresses the Growth of Triple-negative Breast Cancers Jing Qian1, Yanxia Ma1, Abhijit Mazumdar1, Cassandra Moyer1, Brent D. G. Page3, William Tahaney2, Jamal Hill1, Darian Coleman1, Powel. H. Brown1, 2 1 Department of Clinical Cancer Prevention, UT MD Anderson Cancer Center, Houston, TX 2 Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 3 Faculty of Pharmaceutical Sciences, University of British Columbia, Canada, Vancouver BC Background: 281,550 new cases of invasive breast cancer will be diagnosed in US this year. 15% of these patients will be diagnosed with triple-negative breast cancers (TNBCs), which is the most aggressive subtype of breast cancer. Non-specific chemotherapy remains the current standard of care for TNBCs, due to the lack of targeted therapy. We have previously conducted a whole phosphatase RNA microarray analysis of TNBCs compared to estrogen receptor (ER)-positive breast cancers. These studies identified phosphatases that were either over-expressed or under-expressed in TNBCs as compared to ER-positive breast cancers. In this study, we investigated one of the highly expressed phosphatases NUDT5, which hydrolyzes 8-oxo-dGDP and ADP-ribose, as a potential new target for the treatment of TNBCs. Hypothesis: NUDT5 is a critical phosphatase that is necessary for the growth of triple-negative breast cancers. Methods: We obtained NUDT5 mRNA expression levels from publicly-available TCGA, METABRIC, and the CCLE datasets, and compared NUDT5 mRNA level in TNBCs versus ER-positive breast cancers. To demonstrate the effect of NUDT5 inhibition on cell growth, we used siRNA, shRNA, sgRNA, and the small molecule inhibitor TH5427 on various ER-positive cell lines and TNBC cell lines. Cell number was counted on Day 1, 3, 5 and 7. We then investigated the biological mechanisms of growth inhibition by Annexin V-PI, DRAQ7,and BrdU proliferation assays. We studied the effect of NUDT5 loss on oxidative stress and DNA damage pathways by measuring 8-oxoG level and γH2AX positivity in the nucleus. Using nude mouse xenograft models, we also investigated the effect of TH5427 on TNBC growth in vivo. Results: NUDT5 mRNA was highly overexpressed in TNBCs as compared to ER-positive breast cancers in several publically-available datasets. NUDT5 loss significantly inhibited the growth of the TNBC cell lines MDAMB231 and MDAMB436, but not the ER-positive cell lines MCF7 and MDAMB361. NUDT5 inhibition via siRNA or TH5427 did not induce apoptosis or cell death, but did suppress growth as assessed by BrdU incorporation.. In the nucleus, loss of NUDT5 induces the accumulation of the oxidative DNA marker, 8-oxoG, and the DNA damage marker, γH2AX, in TNBCs cells, indicating that loss of NUDT5 induces oxidative DNA damage response. In the MDAMB231 xenograft models, the inhibitor of NUDT5 suppressed TNBC tumor growth in mice. Conclusions: Our results showed NUDT5 is highly expressed in TNBCs as compared to ER-positive tumors. inhibition of NUDT5 suppresses the growth of TNBC but not of ER-positive breast cancer cells. NUDT5 loss also induces oxidative DNA damage, with increased 8-oxoG and γH2AX positivity. These results demonstrate that NUDT5 is essential for the growth of TNBC cells and suggest that NUDT5 is a promising new target for the treatment of these aggressive breast cancers. This work was supported by Charles Cain Endowment (PB).
Citation Format: Jing Qian, Powel Brown. Inhibition of the NUDT5 phosphatase suppresses the growth of triple-negative breast cancers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-07.