Glioblastoma (GBM) is a highly malignant human brain tumor with limited treatment choices. The extremely aggressive characteristics of GBM result from GBM stem cells (GSCs), a subpopulation in tumor having self-renewal potential and resistance to chemotherapy and radiotherapy. Therefore, eliminating GSCs is an effective strategy to treat this fatal disease. In this study, we investigated the therapeutic effects of dietary flavonoids, including apigenin, quercetin, and naringenin, against cancer stem cell-like phenotypes of human GBM cell lines U87MG and U373MG. Among flavonoids studied, apigenin and quercetin significantly suppressed not only the self-renewal capacity such as cell growth and clonogenicity, but also the invasiveness of GBM stem-like cells. Notably, apigenin blocked the phosphorylation of c-Met and its downstream effectors, transducer and activator of transcription 3, AKT (Protein kinase B), and mitogen-activated protein kinase in the GSCs, thereby reducing the expression levels of GSC markers such as CD133, Nanog, and Sox2. These results suggest that the GSC inhibition effect of apigenin may be caused by downregulation of c-Met signaling pathway.

BackgroundCytochrome P450 monooxygenase constitutes a significant group of oxidative enzymes that can introduce an oxygen atom in a high regio- and stereo-selectivity mode. We used the Bacillus megaterium cytochrome P450 BM3 (CYP450 BM3) and its variants namely mutant 13 (M13) and mutant 15 (M15) for the hydroxylation of diverse class of flavonoids.ResultsAmong 20 flavonoids, maximum seven flavonoids were hydroxylated by the variants while none of these molecules were accepted by CYP450 BM3 in in vitro reaction. Moreover, M13 exhibited higher conversion of substrates than M15 and CYP450 BM3 enzymes. We found that M13 carried out regiospecific 3ʹ-hydroxylation reaction of naringenin with the highest conversion among all the tested flavonoids. The apparent Km and kcat values of M13 for naringenin were 446 µM and 1.955 s−1, respectively. In whole-cell biotransformation experiment with 100 µM of naringenin in M9 minimal medium with 2 % glucose in shake flask culture, M13 showed 2.14- and 13.96-folds higher conversion yield in comparison with M15 (16.11 %) and wild type (2.47 %). The yield of eriodictyol was 46.95 µM [~40.7 mg (13.5 mg/L)] in a 3-L volume lab scale fermentor at 48 h in the same medium exhibiting approximately 49.81 % conversion of the substrate. In addition, eriodictyol exhibited higher antibacterial and anticancer potential than naringenin, flavanone and hesperetin.ConclusionsWe elucidated that eriodictyol being produced from naringenin using recombinant CYP450 BM3 and its variants from B. megaterium, which shows an approach for the production of important hydroxylated compounds of various polyphenols that may span pharmaceutical industries.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0533-4) contains supplementary material, which is available to authorized users.

Glioblastoma stem cell targeted therapies have become a powerful strategy for the treatment of this deadliest brain tumor. We demonstrate for the first time that downregulation of mitochondrial ubiquinol-cytochrome c reductase binding protein (UQCRB) inhibits the cancer stem cell-like properties in human glioblastoma cells. The synthetic small molecules targeting UQCRB significantly suppressed not only the self-renewal capacity such as growth and neurosphere formation, but also the metastatic potential such as migration and invasion of glioblastoma stem‑like cells (GSCs) derived from U87MG and U373MG at subtoxic concentrations. Notably, the UQCRB inhibitors repressed c‑Met-mediated downstream signal transduction and hypoxia‑inducible factor‑1α (HIF‑1α) activation, thereby reducing the expression levels of GSC markers including CD133, Nanog, Oct4 and Sox2 in the GSCs. Furthermore, the UQCRB inhibitors decreased mitochondrial ROS generation and mitochondrial membrane potential in the GSCs, indicating that they regulate the mitochondrial function in GSCs. Indeed, the knockdown of UQCRB gene by UQCRB siRNA significantly inhibited the cancer stem cell-like phenotypes as well as the expression of stemness markers by blocking mitochondrial ROS/HIF‑1α/c‑Met pathway in U87MG GSCs. These findings suggest that UQCRB and its inhibitors could be a new therapeutic target and lead compounds for eliminating cancer stem cells in glioblastoma.

In the course of searching for angiogenesis inhibitors from microorganisms, two cyclic peptides, PF1171A (1) and PF1171C (2) were isolated from the soil fungus Penicillium sp. FN070315. In the present study, we investigated the antiangiogenic efficacy and associated mechanisms of 1 and 2 in vitro using human umbilical vein endothelial cells (HUVECs). Compounds 1 and 2 inhibited the proliferation of HUVECs at concentrations not exhibiting cytotoxicity. Moreover, 1 and 2 significantly suppressed vascular endothelial growth factor (VEGF)-induced migration, invasion, proliferation and tube formation of HUVECs as well as neovascularization of the chorioallantoic membrane in developing chick embryos. We also identified an association between the antiangiogenic activity of 1 and 2 and the downregulation of both the phosphorylation of VEGF receptor 2 and the expression of hypoxia inducible factor-1α at the protein level. Taken together, these results further suggest that compounds 1 and 2 will be promising angiogenesis inhibitors.

We evaluated and compared ultraviolet (UV) treatment and simvastatin (SIM) immersion effects on the osseointegration of sandblasted, large-grit, acid-etched (SLA) titanium dental implants at two different time points in rabbit tibias, with or without xenogenic bone graft materials. The surface alteration on simvastatin treatment titanium discs was analyzed using an infrared spectrometer. Implants were categorized into four groups according to the surface treatment type. Twelve rabbits received two implants per tibia. A tibial defect model was created using a trephine bur, with implants in contact with the bone surface and bovine bone graft materials for gap filling. The rabbits were sacrificed after 2 or 4 weeks. UV treatment or SIM immersion increased the bone-to-implant contact (BIC) on nongrafted sides, and both increased the BIC and bone area (BA) on grafted sides. The application of both treatments did not result in higher BIC or BA than a single treatment. At two different time points, BIC in the nongrafted sides did not differ significantly among the UV and/or SIM treated groups, whereas BA differed significantly. UV or SIM treatment of SLA titanium implants accelerates osseointegration in tibias with or without xenogenic bone graft materials. The combination of both treatments did not show synergy.