The Novel Phosphatase NUDT5 is a Critical Regulator of Triple-Negative Breast Cancer Growth

Abstract

Background: The most aggressive form of breast cancer is triple-negative breast cancer (TNBC) which lacks expression of the estrogen receptor (ER), progesterone receptor (PR), and does not have overexpression of the human epidermal growth factor receptor 2 (HER2). Treatment options for women with TNBC tumors are limited, unlike those with ER-positive tumors, that can be treated with hormone therapy, or those with HER2-positive tumors, that can be treated with anti-HER2 therapy. Thus, we have sought to identify novel targeted therapies for TNBC. In this study, we investigated whether a novel phosphatase, NUDT5, is a potential therapeutic target. Methods: TCGA and METABRIC (Curtis) datasets were used to investigate the mRNA expression levels of NUDT5 in breast cancers. NUDT5 ablation was achieved by targeting NUDT5 with siRNA, shRNA, and sgRNA and by inhibiting NUDT5 with the small molecule inhibitor TH5427. Xenograft animal models were used to determine the effect of NUDT5 inhibition on TNBC in vivo growth. Proliferation, death, and DNA replication assays were used to investigate the cell biologic effect of NUDT5 loss or inhibition. The accumulation of 8-oxoG and the induction of gH2AX after NUDT5 loss was determined by immunofluorescence staining. Results: In this study, we demonstrated the important role of an overexpressed phosphatase, NUDT5, in regulating oxidative DNA damage in TNBCs. We found that NUDT5 loss led to suppressed growth of TNBC in vitroand in vivo. This growth inhibition was not induced by death, but instead by suppressed proliferation. Loss or inhibition of NUDT5 induced an increase in 8-oxoG and gH2AX lesions in DNA and a stall in DNA replication, thus inhibiting proliferation. Conclusions: NUDT5 plays a critical role in preventing oxidative DNA damage in TNBC cells. Loss or inhibition of NUDT5 suppressed the growth of TNBCs. These biological and mechanistic studies provide a basic research foundation for the future development of NUDT5 inhibitors for the treatment of TNBC patients.