Layered material platform for surface plasmon resonance biosensing.

Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing.

Salinomycin inhibits prostate cancer growth and migration via induction of oxidative stress.

BACKGROUND: We have shown that a sodium ionophore monensin inhibits prostate cancer cell growth. A structurally related compound to monensin, salinomycin, was recently identified as a putative cancer stem cell inhibitor. METHODS: The growth inhibitory potential of salinomycin was studied in a panel of prostate cells. To get insights into the mechanism of action, a variety of assays such as gene expression and steroid profiling were performed in salinomycin-exposed prostate cancer cells. RESULTS: Salinomycin inhibited the growth of prostate cancer cells, but did not affect non-malignant prostate epithelial cells. Salinomycin impacted on prostate cancer stem cell functions as evidenced by reduced aldehyde dehydrogenase activity and the fraction of CD44(+) cells. Moreover, salinomycin reduced the expression of MYC, AR and ERG, induced oxidative stress as well as inhibited nuclear factor-κB activity and cell migration. Furthermore, profiling steroid metabolites revealed increased levels of oxidative stress-inducing steroids 7-ketocholesterol and aldosterone and decreased levels of antioxidative steroids progesterone and pregnenolone in salinomycin-exposed prostate cancer cells. CONCLUSION: Our results indicate that salinomycin inhibits prostate cancer cell growth and migration by reducing the expression of key prostate cancer oncogenes, inducing oxidative stress, decreasing the antioxidative capacity and cancer stem cell fraction.

Bmx tyrosine kinase has a redundant function downstream of angiopoietin and vascular endothelial growth factor receptors in arterial endothelium.

The Bmx gene, a member of the Tec tyrosine kinase gene family, is known to be expressed in subsets of hematopoietic and endothelial cells. In this study, mice were generated in which the first coding exon of the Bmx gene was replaced with the lacZ reporter gene by a knock-in strategy. The homozygous mice lacking Bmx activity were fertile and had a normal life span without an obvious phenotype. Staining of their tissues using beta-galactosidase substrate to assess the sites of Bmx expression revealed strong signals in the endothelial cells of large arteries and in the endocardium starting between days 10.5 and 12.5 of embryogenesis and continuing in adult mice, while the venular endothelium showed a weak signal only in the superior and inferior venae cavae. Of the five known endothelial receptor tyrosine kinases tested, activated Tie-2 induced tyrosyl phosphorylation of the Bmx protein and both Tie-2 and vascular endothelial growth factor receptor 1 (VEGFR-1) stimulated Bmx tyrosine kinase activity. Thus, the Bmx tyrosine kinase has a redundant role in arterial endothelial signal transduction downstream of the Tie-2 and VEGFR-1 growth factor receptors.

VEGFR3 gene structure, regulatory region, and sequence polymorphisms.

Vascular endothelial growth factor receptor 3 (VEGFR-3) is required for cardiovascular development during embryogenesis. In adults, this receptor is expressed in lymphatic endothelial cells, and mutant VEGFR3 alleles have been implicated in human hereditary lymphedema. To better understand the basis of its specific endothelial lineage-restricted expression, we have characterized the VEGFR3 gene and its regulatory 5' flanking region. The human gene contains 31 exons, of which exons 30a and 30b are alternatively spliced. The VEGFR3 proximal promoter is TATA-less and contains stretches of sequences homologous with the mouse Vegfr3 promoter region. In transfection experiments of cultured cells, the Vegfr3 promoter was shown to control endothelial cell-specific transcription of downstream reporter genes. This result was further confirmed in vivo; in a subset of transgenic mouse embryos, a 1.6 kb Vegfr3 promoter fragment directed weak lymphatic endothelial expression of the LacZ marker gene. This suggests that endothelial cell-specific elements occur in the proximal promoter, although further enhancer elements are probably located elsewhere. The sequence, organization, and variation in the VEGFR3 gene and its regulatory region provide important tools for the molecular genetic analysis of the lymphatic system and its disorders.

Tie receptors: new modulators of angiogenic and lymphangiogenic responses.

Angiogenesis is required for normal embryonic vascular development and aberrant angiogenesis contributes to several diseases, including cancer, diabetes and tissue ischaemia. What are the molecular mechanisms that regulate this important process? The Tie family of receptors and their ligands, the angiopoietins, are beginning to provide insight into how vessels make decisions such as whether to grow or regress--processes that are important not only during development but throughout an organism's life.

Role of ets factors in the activity and endothelial cell specificity of the mouse Tie gene promoter.

The Tie gene encodes an endothelial cell receptor tyrosine kinase necessary for normal vascular development. The Tie gene promoter targets expression of heterologous genes specifically to endothelial cells in transgenic mice. Here we have characterized the promoter sequences critical for endothelial cell-specific activity in cultured cells and transgenic mice. Progressive deletions and site-directed mutations of the promoter showed that the critical endothelial cell-specific elements are an octamer transcription factor binding site and several Ets binding sites located in two clusters within 300 bp upstream of the major transcription initiation site. Among members of the Ets transcription factor family tested, NERF-2 (a novel transcription factor related to the ets factor ELF-1), which is expressed in endothelial cells, and ETS2 showed the strongest transactivation of the Tie promoter; ETS1 gave lower levels of stimulation and the other Ets factors gave little or no transactivation. Furthermore, the Tie promoter directed the production of high amounts of human growth hormone into the circulation of transgenic mice. The secreted amounts correlated with transgene copy number, being relatively insensitive to the effects of the transgene integration site. These properties suggest that Tie promoter activity is controlled by endothelial cell Ets factors and that it has potential for use in vectors for endothelial cell-specific gene expression.