Drug resistance is a major hurdle for the effectiveness of tamoxifen (TAM) to provide clinical benefit. Therefore, it is essential to identify a sensitizer that could be used to improve TAM efficacy in treating TAM‐resistant breast cancer. Here, we investigated the ability of baicalein to reverse TAM resistance. We found that baicalein increased the efficacy of TAM in inhibiting proliferation and inducing apoptosis of TAM‐resistant cells. It also enhanced the TAM‐induced growth reduction of resistant cells from NOD/SCID mouse mammary fat pads, without causing obvious systemic toxicity. Analyses using the CellMiner tool and the Kaplan–Meier plotter database showed that HIF‐1α expression was inversely correlated with TAM therapeutic response in NCI‐60 cancer cells and breast cancer patients. HIF‐1α expression was increased in TAM‐resistant cells due to an increase in mRNA levels and reduced ubiquitin‐mediated degradation. Baicalein reduced HIF‐1α expression by promoting its interaction with PHD2 and pVHL, thus facilitating ubiquitin ligase‐mediated proteasomal degradation and thereby suppressing the nuclear translocation, binding to the hypoxia‐response element, and transcriptional activity of HIF‐1α. As a result, baicalein downregulated aerobic glycolysis by restricting glucose uptake, lactate production, ATP generation, lactate/pyruvate ratio and expression of HIF‐1α‐targeted glycolytic genes, thereby enhancing the antiproliferative efficacy of TAM. Furthermore, baicalein interfered with HIF‐1α inhibition of mitochondrial biosynthesis, which increased mitochondrial DNA content and mitochondrial numbers, restored the generation of reactive oxygen species in mitochondria, and thus enhanced the TAM‐induced mitochondrial apoptotic pathway. The HIF‐1α stabilizer dimethyloxallyl glycine prevented the baicalein‐induced downregulation of glycolysis and mitochondrial biosynthesis and reduced the effects of baicalein on reversing TAM resistance. Our results indicate that baicalein is a promising candidate to help overcome TAM resistance by sensitizing resistant cells to TAM‐induced growth inhibition and apoptosis. The mechanism underlying the effects of baicalein consists of inhibition of HIF‐1α–mediated aerobic glycolysis and mitochondrial dysfunction.

Purpose Oxymatrine, an alkaloid extracted from the Chinese herb Sophora flavescens Aiton, possesses anti-inflammatory, anti-immune, anti-hepatic fibrosis, and anti-cancer properties. However, the effects of oxymatrine on epithelial-mesenchymal transition (EMT) of breast cancer cells are still unclear. Aim The present study was performed to investigate whether oxymatrine reverses EMT in breast cancer cells and to explore the underlying molecular mechanisms. Materials and methods MTT assay was performed to evaluate cell viability. Wound-healing assay and transwell chamber assay were used to assess cell migration and invasion, respectively. Immunofluorescence and Western blot were used to study the expression of EMT-related molecules and α Ⅴ β 3 integrin/focal adhesion kinase (FAK)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling transduction. Fibronectin, a physiologic ligand of α Ⅴ β 3 integrin, was used to stimulate α Ⅴ β 3 integrin signaling. Results Our results demonstrated that oxymatrine effectively suppressed the viability of MDA-MB-231 and 4T1 breast cancer cells, and oxymatrine showed less cytotoxicity on normal breast mammary epithelial MCF-10A cells. In addition, oxymatrine reversed EMT in the MDA-MB-231 and 4T1 cells at nontoxic concentrations. Oxymatrine significantly inhibited cell migration and invasion, downregulated the expression of N-cadherin, vimentin, and Snail in MDA-MB-231 and 4T1 cells, but upregulated the expression of E-cadherin in 4T1 cells. The mechanism revealed that oxymatrine decreased the expression of α Ⅴ and β 3 integrin and their co-localization. It also inhibited α Ⅴ β 3 integrin downstream activation by suppressing the phosphorylation of FAK, PI3K, and Akt. Furthermore, oxymatrine prevented fibronectin-induced EMT and α Ⅴ β 3 integrin/FAK/PI3K/Akt signaling activation. Conclusion Our results revealed that oxymatrine effectively reversed EMT in breast cancer cells by depressing α Ⅴ β 3 integrin/FAK/PI3K/Akt signaling. Thus, oxymatrine could be a potential therapeutic candidate with anti-metastatic potential for the treatment of breast cancer.

The combination of chemotherapy with natural products is a common strategy to enhance anticancer effects while alleviating the dose-dependent adverse effects of cancer treatment. Oxymatrine (OMT) has been extensively reported as having anticancer activity. Doxorubicin (DOX) is a chemotherapeutic DNA-damaging agent used for the treatment of carcinoma. In this study, we investigated whether synergistic effects exist with the combination treatment with OMT and DOX using human colorectal cancer cell (CRC) lines and the potential mechanisms involved in in vitro and in vivo activities. The MTT and colony formation assay results showed that compared to either OMT or DOX monotherapy, the combination of OMT + DOX markedly inhibited the growth of HT-29 and SW620 cells. Wound healing assays showed significant inhibition of cell migration with co-treatment, supported by the change in E-cadherin and N-cadherin expressions in Western blotting. Furthermore, flow cytometry analysis revealed that OMT + DOX co-treatment enhanced cell apoptosis as a result of ROS generation, whereas NAC attenuated OMT + DOX–induced apoptosis. Similarly, the apoptosis-related proteins (cleaved caspase-3, cleaved caspase-9, and the ratio of Bax/Bcl-2) were determined by Western blotting, which showed that the expressions of these markers were notably increased in the co-treatment group. Furthermore, co-administration of a low dose of DOX and OMT inhibited xenograft tumor growth in a dose-dependent manner. TUNEL assay and Ki67 staining images indicated more apoptosis and less proliferation occurred in OMT plus DOX-treated xenograft tumors. Meanwhile, the combination strategy decreased cardiotoxicity, which is the most serious side effect of DOX. RNA sequencing was performed to explore the precise molecular alterations involved in the combination group. Among the numerous differentially expressed genes, downregulated FHL-2 and upregulated cleaved SPTAN1 were validated in both mRNA and protein levels of HT-29 and SW620 cells. These two proteins might play a pivotal role involving in OMT + DOX synergistic activity. Overall, OMT in combination with DOX presented an outstanding synergistic antitumor effect, indicating that this beneficial combination may offer a potential therapy for CRC patients.

A new minor quassinoid named bruceine M (1), together with 12 known quassinoids (2-13), was isolated from the fruits of Brucea javanica (Simaroubaceae). Their structures were determined by interpretation of NMR and HR-ESI-MS data. The structures of the known compounds were confirmed by comparison of their spectral data with those reported in the literatures. In vitro cytotoxicity of the isolated compounds against cancer cell lines Bel-7404, MCF-7 and A549 was evaluated. Compounds 4, 6 and 9 exhibited significant growth inhibitory activity against three cancer cell lines.