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Nuclear factor erythroid 2‐related factor 2 (Nrf2) is a transcriptional factor which acts as a regulator for cellular oxidative stress, and tightly regulated by Kelch‐like ECH‐associated protein 1 (Keap1). In this study, we found that auranofin and paclitaxel combination treatment increased TUNEL positive apoptotic cells and enhanced the DNA damage marker γ‐H2AX in MCF‐7 and MDA‐MB‐231 breast cancer cells. The immunoblotting analysis revealed the combination of auranofin and paclitaxel significantly increased the FOXO3 expression in a concentration dependent manner. Further we observed that auranofin and paclitaxel treatment prevents the translocation of Nrf2 in a concentration dependent manner. The increased FOXO3 expression might be involved in the cytoplasmic degradation of Nrf1‐Keap1 complex. Further, the molecular docking results confirm auranofin act as the agonist for Foxo3. Therefore, the present results suggest that auranofin sensitize the breast cancer cells to paclitaxel via regulating FOXO3/Nrf2/Keap1signaling pathway. Significance Statement: The present results show that auranofin enhances paclitaxel induced TUNEL positive apoptotic cells. Further, auranofin treatment increases FOXO3 which in turn inhibit the dissociation of Nrf2 and Keap1 in both MDA‐MB‐231 and MCF‐7 cell lines. Therefore, the present results clearly illustrate the chemosensitizing property of auranofin via regulating FOXO3/Nrf2/Keap1 signaling pathway in the breast cancer cells. Auranofin is already a Food and Drug administration approved drug and it could be considered for the clinical applications after preclinical experimentation. [ABSTRACT FROM AUTHOR]

The intrinsic redox status of cancer cells limits the efficacy of chemotherapeutic drugs. Auranofin, a Food and Drug Administration‐approved gold‐containing compound, documented with effective pharmacokinetics and safety profiles in humans, has recently been repurposed for anticancer activity. This study examined the paclitaxel‐sensitizing effect of auranofin by targeting redox balance in the MDA‐MB‐231 and MCF‐7 breast cancer cell lines. Auranofin treatment depletes the activities of superoxide dismutase, catalase, and glutathione peroxidase and alters the redox ratio in the breast cancer cell lines. Furthermore, it has been noticed that auranofin augmented paclitaxel‐mediated cytotoxicity in a concentration‐dependent manner in both MDA‐MB‐231 and MCF‐7 cell lines. Moreover, auranofin increased the levels of intracellular reactive oxygen species (observed using 2, 7‐diacetyl dichlorofluorescein diacetate staining) and subsequently altered the mitochondrial membrane potential (rhodamine‐123 staining) in a concentration‐dependent manner. Further, the expression of apoptotic marker p21 was found to be higher in auranofin plus paclitaxel‐treated breast cancer cells compared to paclitaxel‐alone treatment. Thus, the present results illustrate the chemosensitizing property of auranofin in MDA‐MB‐231 and MCF‐7 breast cancer cell lines via oxidative metabolism. Therefore, auranofin could be considered a chemosensitizing agent during cancer chemotherapy. Significance statement: In this study, auranofin, a Food and Drug Administration‐approved drug, has been repurposed for anticancer activity. The results illustrate that auranofin improved paclitaxel‐mediated cytotoxicity in breast cancer cell lines. The auranofin treatment altered the intracellular redox balance in the breast cancer cells, which contributes to paclitaxel‐mediated cell cycle arrest and subsequent apoptotic cell death. Thus, the present results illustrate the chemosensitizing property of auranofin in breast cancer cell lines via oxidative metabolism. Therefore, auranofin could be considered a chemosensitizing agent during cancer chemotherapy. [ABSTRACT FROM AUTHOR]

Studies were performed to examine the affect of nitric oxide (NO) on expression of the divalent metal transporter (DMT1) in undifferentiated P19 embryonic carcinoma cells. DMT1 has four known isoforms which differ in both the N- and C-terminals. Results demonstrate that exposure of P19 cells to the NO precursor, sodium nitro-prusside (SNP), resulted in a decrease in expression of both positive (+) and negative (–) IRE isoforms of DMT1 with no change in the 1A species. Regulation was not as a result of decreased stability of message but was caused by reduction in transcription of the DMT1 1B isoforms. Similar results were observed in other cell lines, including PC12 and SH-SY5Y cells and rat primary sympathetic neurons. Nuclear NF-κB was decreased after SNP treatment, suggesting that NF-κB may mediate this response. Luciferase reporter assays with normal and NF-κB mutated constructs of the 1B promoter confirm that the NF-κB site between −23 to −19 upstream from the transcription start site was responsible for regulating expression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays further demonstrate that the p65 subunit of NF-κB and not p50 binding is specifically decreased by NO treatment. Results of these studies provide a general mechanism responsible for regulating DMT1 expression induced by stress-related signaling processes in vivo. [ABSTRACT FROM AUTHOR]