The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

Lymphatic valves are essential for efficient lymphatic transport, but the mechanisms of early lymphatic-valve morphogenesis and the role of biomechanical forces are not well understood. We found that the transcription factors PROX1 and FOXC2, highly expressed from the onset of valve formation, mediate segregation of lymphatic-valve-forming cells and cell mechanosensory responses to shear stress in vitro. Mechanistically, PROX1, FOXC2, and flow coordinately control expression of the gap junction protein connexin37 and activation of calcineurin/NFAT signaling. Connexin37 and calcineurin are required for the assembly and delimitation of lymphatic valve territory during development and for its postnatal maintenance. We propose a model in which regionally increased levels/activation states of transcription factors cooperate with mechanotransduction to induce a discrete cell-signaling pattern and morphogenetic event, such as formation of lymphatic valves. Our results also provide molecular insights into the role of endothelial cell identity in the regulation of vascular mechanotransduction.

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Although chemokines are well established to function in immunity and endothelial cell activation and proliferation, a rapidly growing literature suggests that CXC Chemokine receptors CXCR3, CXCR4 and CXCR7 are critical in the development and progression of solid tumors. The effect of these chemokine receptors in tumorigenesis is mediated via interactions with shared ligands I-TAC (CXCL11) and SDF-1 (CXCL12). Over the last decade, CXCR4 has been extensively reported to be overexpressed in most human solid tumors and has earned considerable attention toward elucidating its role in cancer metastasis. To enrich the existing armamentarium of anti-cancerous agents, many inhibitors of CXCL12–CXCR4 axis have emerged as additional or alternative agents for neoadjuvant treatments and even many of them are in preclinical and clinical stages of their development. However, the discovery of CXCR7 as another receptor for CXCL12 with rather high binding affinity and recent reports about its involvement in cancer progression, has questioned the potential of “selective blockade” of CXCR4 as cancer chemotherapeutics. Interestingly, CXCR7 can also bind another chemokine CXCL11, which is an established ligand for CXCR3. Recent reports have documented that CXCR3 and their ligands are overexpressed in different solid tumors and regulate tumor growth and metastasis. Therefore, it is important to consider the interactions and crosstalk between these three chemokine receptors and their ligand mediated signaling cascades for the development of effective anti-cancer therapies. Emerging evidence also indicates that these receptors are differentially expressed in tumor endothelial cells as well as in cancer stem cells, suggesting their direct role in regulating tumor angiogenesis and metastasis. In this review, we will focus on the signals mediated by this receptor trio via their shared ligands and their role in tumor growth and progression.

Cyclooxygenase-2 (COX-2), a key enzyme in arachidonic acid metabolism, is overexpressed in many cancers. Inhibition of COX-2 by nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the risk of cancer development in humans and suppresses tumor growth in animal models. The anti-cancer effect of NSAIDs seems to involve suppression of tumor angiogenesis, but the underlying mechanism is not completely understood. Integrin alpha V beta 3 is an adhesion receptor critically involved in mediating tumor angiogenesis. Here we show that inhibition of endothelial-cell COX-2 by NSAIDs suppresses alpha V beta 3-dependent activation of the small GTPases Cdc42 and Rac, resulting in inhibition of endothelial-cell spreading and migration in vitro and suppression of fibroblast growth factor-2-induced angiogenesis in vivo. These results establish a novel functional link between COX-2, integrin alpha V beta 3 and Cdc42-/Rac-dependent endothelial-cell migration. Moreover, they provide a rationale to the understanding of the anti-angiogenic activity of NSAIDs.

The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway regulates multiple cellular processes. An overactivation of the pathway is frequently present in human malignancies and plays a key role in cancer progression. Hence, its inhibition has become a promising approach in cancer therapy. However, the development of resistances, such as the abrogation of negative feedback mechanisms or the activation of other proliferative signaling pathways, has considerably limited the anticancer efficacy of PI3K/AKT inhibitors. In addition, emerging evidence points out that although AKT is acknowledged as the major downstream effector of PI3K, both PI3K and AKT can operate independently of each other in cancer, revealing another level of complexity in this pathway. Here, we highlight the complex relationship between PI3K and AKT in cancer and further discuss the consequences of this relationship for cancer therapy.

We have recently reported that the inhibition of endothelial cell COX-2 by non-steroidal anti-inflammatory drugs suppresses ␣ V ␤ 3 -(but not ␣ 5 ␤ 1 -) dependent Rac activation, endothelial cell spreading, migration, and angiogenesis (Dormond, O., Foletti, A., Paroz, C., and Ruegg, C. (2001) Nat. Med. 7, 1041-1047). Here we investigated the role of the COX-2 metabolites PGE 2 and TXA2 in regulating human umbilical vein endothelial cell (HUVEC) adhesion and spreading. We report that PGE 2 accelerated ␣ V ␤ 3 -mediated HUVEC adhesion and promoted Rac activation and cell spreading, whereas the TXA2 agonist U46619 retarded adhesion and inhibited spreading. We show that the cAMP level and the cAMP-regulated protein kinase A (PKA) activity are critical mediators of these PGE 2 effects. ␣ V ␤ 3 -mediated adhesion induced a transient COX-2-dependent rise in cAMP levels, whereas the cellpermeable cAMP analogue 8-brcAMP accelerated adhesion, promoted Rac activation, and cell spreading in the presence of the COX-2 inhibitor NS-398. Pharmacological inhibition of PKA completely blocked ␣ V ␤ 3 -mediated adhesion. A constitutively active Rac mutant (L61Rac) rescued ␣ V ␤ 3 -dependent spreading in the presence of NS398 or U46691, but did not accelerate adhesion, whereas a dominant negative Rac mutant (N17Rac) suppressed spreading without affecting adhesion. ␣ 5 ␤ 1 -mediated HU-VEC adhesion, Rac activation, and spreading were not affected by PGE 2 , U46691, 8-brcAMP, or the inhibition of PKA. In conclusion, these results demonstrate that PGE 2 accelerates ␣ V ␤ 3 -mediated endothelial cell adhesion through cAMP-dependent PKA activation and induces ␣ V ␤ 3 -dependent spreading via cAMP-and PKA-dependent Rac activation and may contribute to the further understanding of the regulation of vascular integrins ␣ V ␤ 3 by COX-2/PGE 2 during tumor angiogenesis and inflammation.Tumor angiogenesis, i.e. the formation of new blood vessels in response to angiogenic stimuli, promotes tumor progression by stimulating tumor cell survival, tumor invasion, and metastasis formation (1). Many molecules involved in mediating or regulating angiogenesis have been identified (2). They include growth factors (i.e. vascular endothelial growth factors, VEGF) 1 and their cell surface receptors, matrix-degrading enzymes (e.g. matrix metalloproteinases), vascular remodeling ligands, and receptors (i.e. angiopoietins and Tie receptors) and adhesion receptors of the integrin and cadherin families. Integrins are the main receptors for extracellular matrix proteins and consist of two non-covalently associated ␣ and ␤ subunits (3). Integrin ligand binding affinity and adhesion-promoting activity are regulated by intracellular events ("inside out" signaling) (4). Upon ligand binding, integrins rapidly cluster and recruit structural (e.g. ␣-actinin, talin, vinculin) and signaling (e.g. focal adhesion kinase, paxillin, c-Src) proteins to form characteristic structures called focal contacts or focal adhesions (5). Integrins and focal adhesions propagate tensional ...

Recent studies have determined that mTOR mediates the activation of the protein kinase Akt in several cell types, but little is known about the association between mTOR and Akt in vascular endothelial cells. Furthermore, the functional significance of mTOR/Akt signaling has not been characterized in the endothelium. In these studies we treated endothelial cells with the mTOR inhibitor rapamycin, and we found that it decreases Akt phosphorylation and activity, as determined by phosphorylation of its substrate glycogen synthase kinase-3. This effect of rapamycin on Akt phosphorylation could not be demonstrated in endothelial cells transfected with a rapamycin-resistant mTOR construct. Also, in the presence of rapamycin, vascular endothelial growth factor, tumor necrosis factor, and insulin failed to phosphorylate Akt, further indicating that mTOR regulates Akt activation in endothelial cells. The activation of Akt is well established to mediate pro-survival signals. In part this is mediated via the phosphorylation and inactivation of the proapoptotic Akt substrates Foxo1 and Foxo3a. We find that rapamycin totally blocks vascular endothelial growth factor and Aktinducible phosophorylation of these transcription factors in endothelial cells. Furthermore, inhibition of Akt activity by rapamycin increased the number of endothelial cells undergoing apoptosis after serum withdrawal as well as after stimulation by vascular endothelial growth factor or tumor necrosis factor. Taken together these observations demonstrate first, that mTOR regulates the phosphorylation and activation of Akt in endothelial cells and, second, that a major effect of mTOR inhibition in endothelial cells is to suppress Akt-inducible pro-survival signals.Growth factors that are essential for angiogenesis, defined as the formation of new blood vessels from preexisting ones, induce protective genes in endothelial cells (EC) 3 (1). Analysis of the signaling pathways that facilitate growth factor-mediated EC survival have demonstrated a critical function for the serine/threonine kinase Akt in this response (2). For example, vascular endothelial growth factor (VEGF), insulin, and ligation of the Tie2 receptor by angiopoietin-1, which all promote angiogenesis, induce Akt-dependent signals (3-5). Akt is evolutionarily conserved and in mammalian cells consists of three highly homologous isoforms that share more than 80% of their amino acid sequence. Moreover, intracellular signals leading to Akt activation are conserved across species (6, 7). The binding of cytokines and growth factors to vascular EC increases phosphatidylinositol 3-kinase activity, resulting in the production of phosphatidylinositol 3,4,5-triphosphates and the recruitment and activation of phosphoinositide-dependent kinase 1 within the cell membrane. Akt is phosphorylated by phosphoinositidedependent kinase 1 (PDK1) at a threonine residue (Thr-308) in the activation loop and by another putative PDK2 kinase at a serine residue (Ser-473) in the carboxyl-terminal domain. Although several ...