A genetic strategy involving a glycosyltransferase promoter and a lipid translocating enzyme to eliminate cancer cells.

The most common therapeutic strategy for the treatment of cancer uses antimetabolites, which block uncontrolled division of cancer cells and kill them. However, such antimetabolites also kill normal cells, thus yielding detrimental side effects. This emphasizes the need for an alternative therapy, which would have little or no side effects. Our approach involves designing genetic means to alter surface lipid determinants that induce phagocytosis of cancer cells. The specific target of this strategy has been the enzyme activity termed aminophospholipid translocase (APLT) or flippase that causes translocation of phosphatidylserine (PS) from the outer to the inner leaflet of the plasma membrane in viable cells. Efforts to identify the enigmatic, plasma membrane APLT of mammalian cells have led investigators to some P-type ATPases, which have often proven to be the APLT of internal membranes rather than the plasma membrane. By measuring kinetic parameters for the plasma membrane APLT activity, we have shown that the P-type ATPase Atp8a1 is the plasma membrane APLT of the tumorigenic N18 cells, but not the non-tumorigenic HN2 (hippocampal neuron x N18) cells. Targeted knockdown of this enzyme causes PS externalization in the N18 cells, which would trigger phagocytic removal of these cells. But how would we specifically express the mutants or antisense Atp8a1 in the cancer cells? This has brought us to a glycosyltransferase, GnT-V, which is highly expressed in the transformed cells. By using the GnT-V promoter to drive a luciferase reporter gene we have demonstrated a dramatic increase in luciferase expression selectively in tumor cells. The described strategy could be tested for the removal of cancer cells without the use of antimetabolites that often kill normal cells.

Association of plasma levels of F11 receptor/junctional adhesion molecule-A (F11R/JAM-A) with human atherosclerosis.

OBJECTIVES: The purpose of this study was to determine the association of the F11 receptor (F11R) with human vascular disease. BACKGROUND: A molecule identified as critical for platelet adhesion to a cytokine-inflamed endothelial surface in vitro is F11R. The F11R is known to be expressed in platelets and endothelium and reported recently to be overexpressed in atherosclerotic plaques. METHODS: A novel enzyme-linked immunosorbent assay was developed for the measurement of soluble F11R in human plasma. The F11R levels, along with a number of other biomarkers, were measured in 389 male patients with known or suspected coronary artery disease (CAD) undergoing coronary angiography at a Veterans Administration Medical Center. RESULTS: Patients with normal or nonobstructive disease (CAD angiographic score of 0), mild-to-moderate disease (score of 1 to 3), and severe disease (score of 4 to 6) had median F11R plasma levels of 38.6 pg/ml (mean 260 +/- 509.6 pg/ml), 45.2 pg/ml (mean 395.3 +/- 752.7 pg/ml), and 105.8 pg/ml (mean 629 +/- 831.7 pg/ml), respectively (p = 0.03). By multivariate analysis, the variables independently associated with CAD score were age, hyperlipidemia, chronic renal insufficiency, left ventricular function, and plasma F11R levels. The F11R was the only biomarker that was independently associated with CAD score. Consistent with the previously reported effects of tumor necrosis factor (TNF)-alpha on F11R expression in cultured endothelial cells, F11R levels correlated strongly with plasma TNF-alpha levels (r = 0.84; p < 0.0001). CONCLUSIONS: Plasma F11R is independently associated with the presence and severity of angiographically defined CAD. By virtue of its strong correlation to plasma TNF-alpha, F11R may be an important mediator of the effects of inflammation on the vessel wall. Strategies that block F11R may represent a novel approach to the treatment of human atherosclerosis.

The F11 receptor (F11R/JAM-A) in atherothrombosis: overexpression of F11R in atherosclerotic plaques.

F11R is the gene name for an adhesion protein, called the F11-receptor, aka JAM-A, which under normal physiological conditions is expressed constitutively on the surface of platelets and localized within tight junctions of endothelial cells (EC). Previous studies of the interactions between human platelets and EC suggested that F11R/JAM-A plays a crucial role in inflammatory thrombosis and atherosclerosis. The study reported here obtained in-vivo confirmation of this conclusion by investigating F11R/JAM-A protein and mRNA in patients with aortic and peripheral vascular disease and in an animal model of atherosclerosis. Molecular and immunofluorescence determinations revealed very high levels of F11R/JAM-A mRNA and F11R/JAM-A protein in atherosclerotic plaques of cardiovascular patients. Similar results were obtained with 12-week-old atherosclerosis-prone apoE-/- mice, an age in which atherosclerotic plaques are well established. Enhanced expression of the F11R/JAM-A message in cultured EC from human aortic and venous vessels was observed following exposure of the cells to cytokines. Determinations of platelet adhesion to cultured EC inflamed by combined cytokine treatment in the presence of F11R/JAM-A - antagonists provided data indicating that de novo expression of F11R/JAM-A on the luminal surface of inflamed EC has an important role in the conversion of EC to a thrombogenic surface. Further studies of these interactions under flow conditions and under in-vivo settings could provide a final proof of a causal role for F11R/JAM-A in the initiation of thrombosis. Based on our in-vitro and in-vivo studies to date, we propose that therapeutic drugs which antagonize the function of F11R/JAM-A should be tested as novel means for the prevention and treatment of atherosclerosis, heart attacks and stroke.

Isolation, sequencing, and functional analysis of the TATA-less murine ATPase II promoter and structural analysis of the ATPase II gene.

The P-type Mg2+-ATPase, termed ATPase II (Atp8a1), is a putative aminophospholipid transporting enzyme, which helps to maintain phospholipid asymmetry in cell membranes. In this project we have elucidated the organization of the mouse ATPase II gene and identified its promoter. Located within chromosome 5, this gene spans about 224 kb and consists of 38 exons, three of which are alternatively spliced (exons 7, 8 and 16), giving rise to two transcript variants. Translation of these transcripts results in two ATPase II isoforms (1 and 2) composed of 1164 and 1149 amino acids, respectively. Using RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE) we identified multiple transcription start sites (TSS) in messages obtained from heart, lung, liver, and spleen. The mouse ATPase II promoter is TATA-less and lacks a consensus initiator sequence. Luciferase reporter analysis of full and core promoters revealed strong activity and little cell type specificity, possibly because more flanking, regulatory sequences are required to cause such tissue specificity. In the neuronal HN2, N18, SN48 cells and the NIH3T3 fibroblast cells, but not in the B16F10 melanoma cells, the core promoter (-318/+193 with respect to the most common TSS) displayed significantly higher activity than the full promoter (-1026/+193). Serial 5' deletion of the core promoter revealed significant cell type-specific activity of the fragments, suggesting differential expression and use of transcription factors in the five cell lines tested. Additionally distribution of the TSS was organ specific. Such observations suggest tissue-specific differences in transcription initiation complex assembly and regulation of ATPase II gene expression. Information presented here form the groundwork for further studies on the expression of this gene in apoptotic cells.

Isolation, sequencing, and functional analysis of the TATA-less human ATPase II promoter.

Multiple lines of evidence indicate that the P-type Mg(2+)-ATPase, termed ATPase II, could play an important role in apoptosis. With the long-term objective of studying the regulation of this protein during apoptosis, we delineated the exon-intron organization of the human ATPase II gene (within chromosome 4). Subsequently, we used RNA ligase-mediated rapid amplification of cDNA ends to identify a major transcription start site at position -143 with respect to the translation start site. Luciferase reporter analysis of a 1.2-kb 5'-flanking sequence (-1222 to +94 with respect to the transcription start site) revealed strong promoter activity in three human cell lines, human oligodendroglioma (HOG), SHSY5Y (hybrid neuroblastoma), and EA.hy926 (endothelial cell line). Serial deletions from the 5' end of this sequence up to nucleotide -291 yielded some decrease in activity only in the EA.hy926 cells. Further deletion to -217 caused a drastic decrease in activity in all three cell lines, but a -148 fragment showed preferential reduction in activity in the EA.hy926 cells. The promoter activity was nearly equal in two sequence variants of the promoter, one of which (designated as Variant 2) contained a 15-bp direct repeat within a GC-rich region. Additionally, there were several single base-pair changes from the sequence reported by the human genome project. Despite the presence of enhancer/repressor elements, such as Sp1 and NFkappaB, relatively small differences in promoter activity were observed in the three cell lines. However, it is likely that such sequence elements could cause major regulation of promoter activity in cells subjected to conditions that trigger apoptosis. The ATPase II promoter sequence will provide valuable clues to the regulation and role of the ATPase II protein.

Signaling pathways of the F11 receptor (F11R; a.k.a. JAM-1, JAM-A) in human platelets: F11R dimerization, phosphorylation and complex formation with the integrin GPIIIa.

The F11 receptor (F11R) (a.k.a. Junctional Adhesion Molecule, JAM) was first identified in human platelets as a 32/35 kDa protein duplex that serves as receptor for a functional monoclonal antibody that activates platelets. We have sequenced and cloned the F11R and determined that it is a member of the immunoglobulin (Ig) superfamily of cell adhesion molecules. The signaling pathways involved in F11R-induced platelet activation were examined in this investigation. The binding of M.Ab.F11 to the platelet F11R resulted in granule secretion and aggregation. These processes were found to be dependent on the crosslinking of F11R with the Fc gammaRII by M.Ab.F11. This crosslinking induced actin filament assembly with the conversion of discoidal platelets to activated shapes, leading to the formation of platelet aggregates. We demonstrate that platelet secretion and aggregation through the F11R involves actin filament assembly that is dependent on phosphoinositide-3 kinase activation, and inhibitable by wortmannin. Furthermore, such activation results in an increase in the level of free intracellular calcium, phosphorylation of the 32 and 35 kDa forms of the F11R, F11R dimerization coincident with a decrease in monomeric F11R, and association of the F11R with the integrin GPIIIa and with CD9. On the other hand, F11R-mediated events resulting from the binding of platelets to an immobilized surface of M.Ab.F11 lead to platelet adhesion and spreading through the development of filopodia and lammelipodia. These adhesive processes are induced directly by interaction of M.Ab.F11 with the platelet F11R and are not dependent on the Fc gammaRII. We also report here that the stimulation of the F11R in the presence of nonaggregating (subthreshold) concentrations of the physiological agonists thrombin and collagen, results in supersensitivity of platelets to natural agonists by a F11R-mediated process independent of the Fc gammaRII. The delineation of the two separate F11R-mediated pathways is anticipated to reveal significant information on the role of this cell adhesion molecule in platelet adhesion, aggregation and secretion, and F11R-dependent potentiation of agonist-induced platelet aggregation. The participation of F11R in the formation and growth of platelet aggregates and plaques in cardiovascular disorders, resulting in enhanced platelet adhesiveness and hyperaggregability, may serve in the generation of novel therapies in the treatment of inflammatory thrombosis, heart attack and stroke, and other cardiovascular disorders.

Two regions of the human platelet F11-receptor (F11R) are critical for platelet aggregation, potentiation and adhesion.

The F11 receptor (F11R) was first identified on the surface of human platelets as a target for a stimulatory monoclonal antibody (M.Ab.F11) that induces secretion, followed by exposure of fibrinogen receptors and aggregation. Cloning of the gene of F11R has revealed that this protein is a cell adhesion molecule (CAM), a member of the Ig superfamily and an ortholog of the murine protein called junctional adhesion molecule (JAM). The present study has identified two domains through which M.Ab.F11 triggers a platelet response culminating with aggregation. M.Ab.F11-mediated platelet adhesion, and the potentiation of collagen and ADP-induced platelet aggregation by M.Ab.F11, were found to involve the same two domains. A F11R recombinant protein (sF11R) completely inhibited platelet aggregation, adhesion and potentiation induced by M.Ab.F11, indicative that the active conformation of the external domain of F11R is present in the soluble, secreted recombinant protein. Furthermore, a specific peptide containing the sequence of the N-terminal amino acids S-1 to C-23 of F11R, and a peptide with the sequence of K-70 to C-82 in the 1st immunoglobulin-like (Ig) fold of F11R, both inhibited M.Ab.F11-induced aggregation, adhesion and potentiation of the aggregation of human platelets. Modeling of the 3D structure of the extracellular domain of the human platelet F11R suggests that these two regions form an active site within the conformation of this CAM. The sequence of these functional domains of F11R (in the N-terminus and 1st Ig-fold) provide the basis for new drug development in the treatment of certain types of thrombocytopenia and inflammatory thrombosis.