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Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy. P‐glycoprotein (P‐gp) one of the ATP‐binding cassette (ABC) transporters plays an important role in MDR. In this study, we examined the sensitizing property of andrographolide (Andro) to reverse MDR in the drug‐resistant KBChR 8‐5 cells. Andro exhibited increased cytotoxicity in a concentration‐dependent manner in the P‐gp overexpressing KBChR 8‐5 cells. Furthermore, Andro showed synergistic interactions with PTX and DOX in this drug‐resistant cells. Andro co‐administration enhanced PTX‐ and DOX‐induced cytotoxicity and reduced cell proliferation in the MDR cancer cells. Moreover, reactive oxygen species (ROS) were elevated with a decrease in the mitochondrial membrane potential (MMP) during Andro and chemotherapeutic drugs combination treatment in the drug‐resistant cells. Furthermore, Andro and PTX‐induced cell cycle arrest was observed in the drug‐resistant cell. We also noticed that the expression of ABCB1 and AKT were downregulated during Andro (4 µM) treatment. Furthermore, Andro treatment enhanced the expression of caspase 3 and caspase 9 in the combinational groups that support the enhanced apoptotic cell death in drug‐resistant cancer cells. Therefore, the results reveal that Andro plays a role in the reversal of P‐gp‐mediated MDR in KBChR 8‐5 cells which might be due to regulating ABCB1/AKT signaling pathway. Significance statement: ATP‐binding cassette (ABC) transporters‐mediated multidrug resistance (MDR) is a major hindrance during cancer treatment. Efflux mechanism of P‐glycoprotein (P‐gp) decreases bioavailability and efficacy of chemotherapeutic drugs. Already known inhibitors of P‐gp exhibit higher toxicity to the untargeted cells. Phytochemicals have great potential to reverse the MDR mechanism in cancer cells with less toxicity. Andrographolide (Andro), a phytochemical of Andrographis paniculata, enhanced the efficacy of the chemotherapeutic drugs and reverses drug resistance in MDR cancer cells. Therefore, Andro can be considered as a potent candidate to overcome MDR after preclinical and clinical validations. [ABSTRACT FROM AUTHOR]

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]

Signal transducers and activators of transcription 3 ( STAT3) play a critical role in inflammation, proliferation and carcinogenesis. Inhibition of JAK- STAT3 signaling is proved to be a novel target for prevention of UVB-induced skin carcinogenesis. In this study, chronic UVB irradiation (180 mJ cm−2; weekly thrice for 30 weeks) induces the expression of IL-10 and JAK1 that eventually activates the STAT3 which leads to the transcription of proliferative and antiapoptotic markers such as PCNA, Cyclin-D1, Bcl2 and Bcl-xl, respectively. Caffeic acid ( CA) inhibits JAK- STAT3 signaling, thereby induces apoptotic cell death by upregulating Bax, Cytochrome-C, Caspase-9 and Caspase-3 expression in mouse skin. Furthermore, TSP-1 is an antiangiogeneic protein, which is involved in the inhibition of angiogenesis and proliferation. Chronic UVB exposure decreased the expression of TSP-1 and pretreatment with CA prevented the UVB-induced loss of TSP-1 in UVB-irradiated mouse skin. Thus, CA offers protection against UVB-induced photocarcinogenesis probably through modulating the JAK- STAT3 in the mouse skin. [ABSTRACT FROM AUTHOR]