Marina Wolfson

NEDD9 Promotes Oncogenic Signaling in Mammary Tumor Development

In the past 3 years, altered expression of the HEF1/CAS-L/NEDD9 scaffolding protein has emerged as contributing to cancer metastasis in multiple cancer types. However, whereas some studies have identified elevated NEDD9 expression as prometastatic, other work has suggested a negative role in tumor progression. We here show that the Nedd9-null genetic background significantly limits mammary tumor initiation in the MMTV-polyoma virus middle T genetic model. Action of NEDD9 is tumor cell intrinsic, with immune cell infiltration, stroma, and angiogenesis unaffected. The majority of the late-appearing mammary tumors of MMTV-polyoma virus middle T;Nedd9(-/-) mice are characterized by depressed activation of proteins including AKT, Src, FAK, and extracellular signal-regulated kinase, emphasizing an important role of NEDD9 as a scaffolding protein for these prooncogenic proteins. Analysis of cells derived from primary Nedd9(+/+) and Nedd9(-/-) tumors showed persistently reduced FAK activation, attachment, and migration, consistent with a role for NEDD9 activation of FAK in promoting tumor aggressiveness. This study provides the first in vivo evidence of a role for NEDD9 in breast cancer progression and suggests that NEDD9 expression may provide a biomarker for tumor aggressiveness.

The signaling hubs at the crossroad of longevity and age-related disease networks.

The established human age-related disease proteins (ARDPs) and longevity-associated proteins (LAPs) together with their first-order interacting partners form scale-free networks which significantly overlap. About half of the common proteins are involved in signal transduction. These proteins are strongly interconnected and in turn form a common signaling network which comprises over 40% of all hubs (proteins with multiple interactions) in the human interactome. Along with the insulin pathway, the common signaling network is remarkably enriched with the focal adhesion and adherens junction proteins whose relation to the control of lifespan is yet to be fully addressed. The examples of such candidate proteins include several hubs, focal adhesion kinase PTK2 and the extracellular proteins fibronectin FN1, paxillin PXN, and vinculin VCL. The results of the network-based analysis highlight the potential importance of these pathways, especially hubs, in linking the human longevity and age-related diseases.

Modified pectin-based carrier for gene delivery: cellular barriers in gene delivery course.

The use of polysaccharides as DNA carriers has high potential for gene therapy applications. Pectin is a structural plant polysaccharide heterogeneous with respect to its chemical structure. It contains branches rich in galactose residues which serve as potential ligands for membrane receptors interaction. In order to make the anionic pectin applicable for DNA complexation, it was modified with three different amine groups (cationic). Pectin-NH2 was prepared by modifying the galacturonic acids carboxyl groups with primary amine groups and further modified to generate pectin-T (T=N+H(CH3)(2)) and pectin-NH2-Q (Q=N+(CH3)(3)). All three modified pectins formed complexes with plasmid DNA as indicated by gel electrophoresis analysis. The size and morphology of pectin-NH2/DNA complexes were examined by transmission electron microscopy (TEM). Transfection experiments were carried out with human embryonic kidney cell lines (HEK293), using plasmid DNA encoding for green fluorescence protein (GFP). Transfection efficiency was analyzed by flow cytometry analysis, using FACS. Pectin-NH2-Q was the most efficient carrier. Addition of chloroquine (lysosomotropic agent) to transfection medium substantially enhanced the HEK293 transfection, indicating that endocytosis is the preferable internalization pathway and implies on the complex inability to escape the endosome. Pectins galactose residues contribution to transfection was examined by inhibiting pectin binding to membrane receptors (galectins), using galactose and lactose as competitive inhibitors to this interaction. Resulting reduction of transfection efficiency demonstrated the importance of pectins galactose residues to HEK293 transfection. Suggesting the modified pectin is a promising non-viral carrier for targeted gene delivery to cancer cells with galactose-binding lectins on their surface.

Rapid purification of extracellular and intracellular Moloney murine leukemia virus

SummaryThe present study demonstrates the advantages of a combination of concentration by polyethylene glycol-6000 and Sepharose Cl-4B chromatography as a rapid procedure for retroviruses purification. This procedure can be completed within 3 hours, providing a high degree of virus purification with minimal damage to its structural and biological properties. Using transmission electron microscopy we observed many intracellular type-C virions in cytoplasmic vacuoles of 3T3/NIH cells chronically infected with Moloney murine leukemia virus. There intracellular virions could be isolated from postmitochondrial cytoplasmic fractions prepared from the infected cells by a procedure which minimized its contamination by extracellular free or membrane-bound virions. SDS-polyacrylamide gel electrophoresis showed that the intracellular and extracellular virions contained similar protein composition.

Common gene signature of cancer and longevity

An association between aging/longevity and cancer has long been suggested, yet the evolutionary and molecular links between these complicated traits remain elusive. Here, we analyze the relationship between longevity- and cancer-associated genes/proteins (LAGs/LAPs and CAGs/CAPs, respectively). Specifically, we address the following questions: (1) to what extent the CAGs and LAGs are evolutionary conserved and how they (or their orthologs) are related to each other in diverse species? (2) Could they act in cooperative manner at a protein level via protein-protein interactions (PPIs) and, if so, by forming a PPI network? We found that (i) the common genes (both LAGs and CAGs) show the same remarkable trend from yeast to humans: tumor suppressors are associated with lifespan extension, whereas the oncogenes are associated with reduced lifespan; (ii) LAPs and CAPs have a significantly higher average connectivity than other proteins in the human interactome; and (iii) LAPs and CAPs may act in cooperative manner via numerous direct and indirect PPIs between themselves and eventually by forming a PPI network. Altogether, the results of this study provide strong evidence for the existence of evolutionary and molecular links between longevity and cancer.

Chronic treatment of human astrocytoma cells with lithium, carbamazepine or valproic acid decreases inositol uptake at high inositol concentrations but increases it at low inositol concentrations

Inositol uptake was measured at concentrations of 25, 40 and 50 microM in human astrocytoma cell cultures treated for 1-3 weeks with pharmacologically relevant concentrations of LiCl, valproic acid or carbamazepine as well as in control cultures that had not been treated with any drug. After at least 2 weeks of treatment, each of these 3 conventional anti-bipolar drugs increased the uptake significantly at 25 microM inositol, had no effect at 40 microM, and decreased it at 50 microM inositol. Reduction of the drug concentrations by 50% abolished the stimulation of uptake at 25 microM inositol by lithium and valproic acid and reduced that by carbamazepine. These findings may contribute to an understanding of the mechanisms of action for anti-bipolar medication, and explain the controversy in the literature whether or not brain inositol is reduced after chronic administration of lithium.

Enhanced genetic instability and dasatinib sensitivity in mammary tumor cells lacking NEDD9.

Elevated expression of the NEDD9/HEF1/Cas-L scaffolding protein promotes tumor cell invasion and metastasis in multiple cancer cell types. Conversely, generation of mammary tumors in the mouse mammary tumor virus (MMTV)-polyoma virus middle T (PyVT) genetic model is delayed by a Nedd9(-/-) genotype. These activities arise from the role of NEDD9 in assembling complexes and supporting activity of cancer signaling proteins, including FAK, Src, Shc, and AKT, and would support evaluation of NEDD9 expression as an unambiguous biomarker for tumor aggressiveness. However, we here show that despite the initial delay in tumor growth, cells derived from MMTV-PyVT;Nedd9(-/-) tumors are characteristically hyperaggressive versus MMTV-PyVT;Nedd9(+/+) cells in anchorage-independent growth, in growth on three-dimensional matrix produced by tumor-associated fibroblasts, and in formation of tumors after mammary orthotopic reinjection and of lung metastases after tail vein injection. This reversal suggests the specific selection of MMTV-PyVT;Nedd9(-/-) cells for growth in an in vivo microenvironment. Indeed, MMTV-PyVT;Nedd9(-/-) cells have increased cell cycle, centrosomal, and mitotic defects, phenotypes compatible with the increased selection of these cells for aggressive growth. Intriguingly, in spite of their aggressive phenotype, MMTV-PyVT;Nedd9(-/-) cells persistently have low levels of Src activation and are hypersensitive to the Src kinase inhibitor dasatinib. These studies identify NEDD9 as a complex modulator of different aspects of mammary tumor growth.

Senescing Cells Share Common Features with Dedifferentiating Cells

Dedifferentiation signifies the capacity of somatic cells to acquire stem cell-like properties. This process can be induced during normal development and as a response to various stimuli, such as pathogen infection and wounding. Dedifferentiation also characterizes the transition of differentiated leaf cells into protoplasts (plant cells devoid of cell walls), a transition accompanied by widespread chromatin decondensation. Transcriptome profiling of dedifferentiating protoplast cells revealed striking similarities with senescing cells; both display a large increase in the expression of genes of specific transcription factor (TF) families, including ANAC, WRKY, bZIP, and C2H2. Further analysis showed that leaves induced to senesce by exposure to dark display characteristic features of dedifferentiating cells, including chromatin decondensation, disruption of the nucleolus, and condensation of rRNA genes. Considering that premature senescence can be induced by various stress conditions both in plant and animal cells, our results suggest that the response of plant and also animal cells to certain stresses converges on cellular dedifferentiation whereby cells first acquire stem cell-like state prior to acquisition of a new cell fate (e.g., reentry into the cell cycle or death).

Chronic treatment with lithium and pretreatment with excess inositol reduce inositol pool size in astrocytes by different mechanisms

Chronic treatment with a lithium salt is the classical treatment for manic-depressive disorder. It is hypothesized that the therapeutic action of lithium is caused by its inhibition of inositol phosphatases which leads to a relative deficiency of inositol and, therefore, an impairment of inositol recycling and production of precursor for the second messengers inositol triphosphate (IP3) and diacylglycerol (DAG). However, peculiarly enough, treatment with high doses of inositol also has an antidepressant effect. In the present work, we have studied the acute and chronic effects of lithium and of excess inositol, in separation or together, on accumulation of 50 microM [3H]inositol (a physiologically relevant concentration) into primary cultures of mouse astrocytes. Two parameters were investigated: (1) rate of unidirectional uptake across the cell membrane (measured during short-term exposure to the radioisotope), and (2) magnitude of the intracellular pool of inositol, equilibrating with extracellular inositol (measured during long-term exposure to the radioisotope). Inositol uptake was highly concentrative and occurred with a Km of approximately 500 microM and a Vmax of 1.5 nmol/min/mg protein. The uptake rate was not affected by either acute or chronic treatment with LiCl (or both), but it was substantially reduced (down-regulated) after pretreatment with a high concentration of inositol. The inositol pool size was decreased to a similar extent as the uptake rate by previous exposure to excess inositol. In spite of the fact that inositol uptake rate was unaffected by lithium, the magnitude of the inositol pool was significantly decreased by chronic treatment with a pharmacologically relevant concentration of LiCl (1 mM), but not by treatment with lower concentrations. This decrease is likely to reflect a reduction in either inositol synthesis or replenishment of inositol from IP3, due to the inhibition of inositol phosphatases by the lithium ion. In agreement with the different mechanisms by which lithium and pretreatment with excess inositol appear to reduce the pool size of inositol, the effects of pretreatment with excess inositol and of LiCl were additive. It is noteworthy that both effects could be observed in astrocytes, suggesting that there might be a significant astrocytic target during clinical treatment.

A model of inositol compartmentation in astrocytes based upon efflux kinetics and slow inositol depletion after uptake inhibition

Intracellular compartmentation of inositol was demonstrated in primary cultures of mouse astrocytes, incubated in isotonic medium, by determination of efflux kinetics after “loading” with [3H]inositol. Three kinetically different compartments were delineated. The largest and most slowly exchanging compartment had a halflife of ∼9 hr. This slow release leads to retention of a sizeable amount of pre-accumulated inositol in the tissue 24 hr after the onset of uptake inhibition, as confirmed by the observation that the inositol uptake inhibitor fucose caused a larger inhibition of unidirectional inositol uptake than of inositol pool size, measured as accumulated [3H]inositol after 24 hr of combined exposure to the inhibitor and the labeled isotope. Based upon the present observations and literature data, it is suggested that the large, slowly exchanging compartment is largely membrane-associated and participating in signaling via the phosphatidylinositide second messenger system, whereas inositol functioning as an osmolyte is distributed in the cytosol and located in one or both of the compartments showing a faster release.