Abstract P5-12-08: The role of a novel phosphatase NUDT5 in triple-negative breast cancer
Authors: Qian Jing , Tahaney William , Ma Yanxia , Mazumdar Abhijit , Brown Powel 
Published: March 2022

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 hypothesized that phosphatases are potential new drug targets for TNBCs and performed a whole phosphatase microarray analysis using TNBCs vs. estrogen receptor (ER)-positive breast cancers. NUDT5, the enzyme hydrolyzes 8-oxo-dGDP and ADP-ribose, is among the most highly expressed phosphatases in TNBCs. The goal of these studies is to investigate NUDT5 dependency and mechanism in TNBC development.Methods: In this study, we have obtained NUDT5 mRNA expression level from publicly available TCGA, METABRIC, and the CCLE datasets, and compared NUDT5 mRNA level in TNBC vs. ER-positive breast cancer. Next, we examined the association of overall survival with NUDT5 expression level dichotomized by median mRNA expression in breast cancer patients. We then engineered doxycycline-inducible NUDT5 knockdown and knockout systems in TNBC cell lines, and characterized cell growth features over 7 days with or without NUDT5 depletion. Growth inhibition effect is also confirmed by NUDT5 inhibitor. After 72 hours of doxycycline induction, cell growth was determined by cell count over 7 days. Using these TNBC cellular models, we also determined molecular phenotypes after NUDT5 depletion by immunofluorescent microscopy for 8-oxo-dGDP and γH2AX. ImageXpress Automated Cell Imaging System and CellReporterXpress were applied for image processing and data quantification. Results: NUDT5 RNA is highly overexpressed in TNBCs as compared to ER-positive breast cancers and normal breast tissue. Survival analyses indicated that increasing NUDT5 level is significantly correlated with worse clinical outcomes of breast cancer patients. NUDT5 protein is highly expressed in TNBC cell lines, compared to ER-positive breast cancer cell lines. NUDT5 knockdown or knockout both significantly inhibits the growth of TNBC cell lines. Loss of NUDT5 induced the oxidative DNA lesion 8-oxoG level in the nucleus, as well as the ratio of γH2AX-positive cells. The inhibitor of NUDT5 also suppressed TNBC cell growth in vitro. Conclusions: Our results showed that the level of NUDT5 negatively correlates with TNBC patient survival. NUDT5 is required for the TNBC cells growth and tolerance to endogenous DNA damage agents. Our findings have revealed the essential function of NUDT5, and will provide critical insights for the future development of NUDT5 inhibitors for the treatment of TNBC patients. This work was supported by Charles Cain Endowment (PB).

Citation Format: Jing Qian, William Tahaney, Yanxia Ma, Abhijit Mazumdar, Powel Brown. The role of a novel phosphatase NUDT5 in triple-negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-12-08.