Towards an integrated cellular and molecular: definition of breast cancers

Breast cancer is a major health problem as well as scientifically poorly understood. Our knowledge of breast cancer is however rapidly progressing in several directions. First, genomic studies are establishing a new molecular classification of breast cancers. Molecular subtypes have been identified and are being associated with the histoclinical forms of breast cancers. Second, genetic alterations are discovered and classified, generating new potential therapeutical targets. Third, mammary stem cells have been identified in the normal mammary epithelium. Their altered counterparts have been identified in tumors and are being characterized. These combined studies allow a new integrated cellular and molecular definition of breast cancers and a conceptual basis that will help the management of the disease.     

Dietary antioxidants as inhibitors of the heme-induced peroxidation of linoleic acid: mechanism of action and synergism

In this work, a quantitative kinetic model for investigating the heme-induced peroxidation of linoleic acid and its inhibition by two important dietary antioxidants, quercetin and alpha-tocopherol, is developed. The main conclusions of this work are: (1) The time dependence of the lipid hydroperoxide concentration is critically dependent on the rate constant for lipid hydroperoxide cleavage, initial fraction of lipid hydroperoxides among the pool of conjugated dienes, and rate of heme degradation. (2) The lipophilic antioxidant alpha-tocopherol acts as a chain-breaking antioxidant that quickly reduces 1-2 eq of lipid peroxyl radicals (inhibition of propagation), whereas the more hydrophilic antioxidant quercetin is only marginally chain-breaking but capable of reducing 4-5 eq of iron-oxo initiator (inhibition of initiation). (3) Based on comparisons between experimental peroxidation curves and simulated curves assuming additivity, it can be concluded that combinations of alpha-tocopherol and quercetin are generally synergistic. The kinetic analysis and HPLC titrations of the antioxidants both suggest that synergism mainly arises from a capacity of alpha-tocopherol to regenerate some quercetin oxidation products still endowed with a reducing activity.     

Rab6 and the secretory pathway affect oocyte polarity in Drosophila

The Drosophila oocyte is a highly polarized cell. Secretion occurs towards restricted neighboring cells and asymmetric transport controls the localization of several mRNAs to distinct cortical compartments. Here, we describe a role for the Drosophila ortholog of the Rab6 GTPase, Drab6, in establishing cell polarity during oogenesis. We found that Drab6 localizes to Golgi and Golgi-derived membranes and interacts with BicD. We also provide evidence that Drab6 and BicD function together to ensure the correct delivery of secretory pathway components, such as the TGFalpha homolog Gurken, to the plasma membrane. Moreover, in the absence of Drab6, osk mRNA localization and the organization of microtubule plus-ends at the posterior of the oocyte were both severely affected. Our results point to a possible connection between Rab protein-mediated secretion, organization of the cytoskeleton and mRNA transport.     

pH-imprinted lipase catalyzed synthesis of dextran fatty acid ester

The application of enzymatic catalysis for the synthesis of polysaccharide-based surfactants was investigated. The polysaccharide dextran, a neutral bacterial polysaccharide consisting of -1,6 linked glucose units, was chemically modified by the attachment of hydrophobic groups through a transesterification reaction with a vinyl decanoate. A screening of commercially available lipases and protease for the synthesis of amphiphilic polysaccharides in DMSO suggested that lipase AY from Candida rugosa modified dextran T-40 with vinyl decanoate at the highest conversion. A pH-adjustment in a phosphate buffer at pH 7.5 prior to use is crucial to make this enzyme active in DMSO. The effect of enzyme concentration and mole ratio of fatty ester to dextran T-40 on the conversion and the rate of reaction were studied. Finally, investigation of the kinetics and regioselectivity of lipase AY-catalyzed modification offer a possibility to regulate the position and the extent of hydrophobic group attached to dextran. These two properties are fundamental for controlling the physico-chemical properties of the final polymeric surfactants.     

Bioactive microarrays immobilized on low-fouling surfaces to study specific endothelial cell adhesion

With the aim to study how to modulate the specific endothelial cell patterning and responses on biomaterials surfaces, bioactive microarrays were developed and validated for specific cell patterning. These microarrays were made of low-fouling surfaces, that prevent nonspecific cell adhesion, bearing bioactive molecules at given known locations by presenting specific ligands to cell receptors. Arrays of bioactive molecules (RGD, REDV, and SVVYGLR sequences and vascular endothelial growth factor (VEGF)) were immobilized on a carboxy-methyl-dextran low-fouling surface and were exposed to human endothelial cells and fibroblasts to screen for the effect of bioactive spot molecular composition on cell adhesion. Endothelial cells only were sensitive to RGD peptide co-immobilized with REDV or SVVYGLR sequences: they induced a reduction in cell spreading and a loss of actin stress fibers. RGD co-immobilized with VEGF also resulted in the reorganization of actin filaments and focal points in endothelial cells. Combination of RGD with these endothelial cell-selective biomolecules did not elicit a strong adhesion phenotype but rather one characteristic of migrating cells.