At various stages during embryogenesis and cancer cells are exposed to tension, compression and shear stress; forces that can regulate cell proliferation and differentiation. In the present study, we show that shear stress blocks cell cycle progression in colon cancer cells and regulates the expression of genes linked to the Wnt/β-catenin, mitogen-activated protein kinase (MAPK) and NFκB pathways. The shear stress-induced increase of the secreted Wnt inhibitor DKK1 requires p38 and activation of NFκB requires IκB kinase-β. Activation of β-catenin, important in Wnt signaling and the cause of most colon cancers, is inhibited by shear stress through a pathway involving laminin-5, α6β4 integrin, phosphoinositide 3-kinase (PI 3-kinase) and Rac1 coupled with changes in the distribution of dephosphorylated β-catenin. These data show that colon cancer cells respond to fluid shear stress by activation of specific signal transduction pathways and genetic regulatory circuits to affect cell proliferation, and indicate that the response of colon cancers to mechanical forces such as fluid shear stress should be taken into account in the management of the disease.

Activation of the Wnt/␤-catenin and retinoid signaling pathways is known to tilt cartilage matrix homeostasis toward catabolism. Here, we investigated possible interactions between these pathways. We found that all-trans-retinoic acid (RA) treatment of mouse epiphyseal chondrocytes in culture did increase Wnt/ ␤-catenin signaling in the absence or presence of exogenous Wnt3a, as revealed by lymphoid enhancer factor/T-cell factor/ ␤-catenin reporter activity and ␤-catenin nuclear accumulation. This stimulation was accompanied by increased gene expression of Wnt proteins and receptors and was inhibited by co-treatment with Dickkopf-related protein-1, an extracellular inhibitor of Wnt/␤-catenin signaling, suggesting that RA modulates Wnt signaling at Wnt cell surface receptor level. RA also enhanced matrix loss triggered by Wnt/␤-catenin signaling, whereas treatment with a retinoid antagonist reduced it. Interestingly, overexpression of retinoic acid receptor ␥ (RAR␥) strongly inhibited Wnt/␤-catenin signaling in retinoid-free cultures, whereas small interfering RNA-mediated silencing of endogenous RAR␥ expression strongly increased it. Small interfering RNA-mediated silencing of RAR␣ or RAR␤ had minimal effects. Co-immunoprecipitation and two-hybrid assays indicated that RAR␥ interacts with ␤-catenin and induces dissociation of ␤-catenin from lymphoid enhancer factor in retinoidfree cultures. The N-terminal domain (AF-1) of RAR␥ but not the C-terminal domain (AF-2) was required for association with ␤-catenin, whereas both AF-1 and AF-2 were necessary for inhibition of ␤-catenin transcriptional activity. Taken together, our data indicate that the Wnt and retinoid signaling pathways do interact in chondrocytes, and their cross-talks and cross-regulation play important roles in the regulation of cartilage matrix homeostasis.Growth plate cartilage and hyaline cartilage have essential roles in skeletal growth and long term function. Growth plate cartilage mediates the formation and elongation of most skeletal elements during prenatal and early postnatal life via endochondral ossification, including vertebral bodies, cranial base, and long bones (1, 2). During this process, growth plate chondrocytes undergo a process of maturation during which the cells first proliferate and then enlarge and become hypertrophic, mineralize their extracellular matrix, and are finally replaced by bone and marrow. As the chondrocytes mature, they change their production of extracellular matrix that is mainly composed of aggrecan and collagens II and XI in upper growth plate zones but becomes enriched with collagen X and other macromolecules in the hypertrophic zone. In comparison with the transient nature of growth plate cartilage, hyaline permanent cartilage persists throughout life at important locations, such as joints and tracheal rings. This tissue also has a very abundant and unique extracellular matrix that is maintained in a stable and functional composition and structure by chondrocyte activity. It is well established that the ext...

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Structure-based virtual screening (SBVS) is a computational approach used in the early-stage drug discovery campaign to search a chemical compound library for novel bioactive molecules against a certain drug target. It utilizes the three-dimensional (3D) structure of the biological target, obtained from X-ray, NMR, or computational modeling, to dock a collection of chemical compounds into the binding site and select a subset of these compounds based on the predicted binding scores for further biological evaluation. In the present work, we illustrate the basic process of conducting a SBVS with examples using freely accessible tools and resources.

Although cardiovascular disease is a major health burden for patients with chronic kidney disease, most cardiovascular outcome trials have excluded patients with advanced chronic kidney disease. Moreover, the major cardiovascular outcome trials that have been conducted in patients with end-stage renal disease have not demonstrated a treatment benefit. Thus, clinicians have limited evidence to guide the management of cardiovascular disease in patients with chronic kidney disease, particularly those on dialysis. Several factors contribute to both the paucity of trials and the apparent lack of observed treatment effect in completed studies. Challenges associated with conducting trials in this population include patient heterogeneity, complexity of renal pathophysiology and its interaction with cardiovascular disease, and competing risks for death. The Investigator Network Initiative Cardiovascular and Renal Clinical Trialists (INI-CRCT), an international organization of academic cardiovascular and renal clinical trialists, held a meeting of regulators and experts in nephrology, cardiology, and clinical trial methodology. The group identified several research priorities, summarized in this paper, that should be pursued to advance the field towards achieving improved cardiovascular outcomes for these patients. Cardiovascular and renal clinical trialists must partner to address the uncertainties in the field through collaborative research and design clinical trials that reflect the specific needs of the chronic and end-stage kidney disease populations, with the shared goal of generating robust evidence to guide the management of cardiovascular disease in patients with kidney disease.

Eukaryotic initiation factor 6 (eIF6), an essential protein important in ribosome biosynthesis and assembly, was identified as an interacting partner of the b-catenin C terminus in the yeast two-hybrid assay. Independent studies identified Drosophila eIF6 (DeIF6) in a genetic screen designed to detect new genes involved in the regulation of the Wnt/Wg (wingless) pathway. Ectopic expression of DeIF6 in wing discs results in a Wg phenotype. Expression of eIF6 in adenomatous polyposis coli (APC)-mutant colon cancer cells, which express high levels of active b-catenin, showed that eIF6 selectively inhibits the Wnt pathway at the level of b-catenin protein independently of proteasomal degradation. Incorporation of radiolabeled amino acids into b-catenin was selectively decreased in cells that overexpressed eIF6. A similar inverse relationship of the two proteins was observed in the APC min/ þ mouse intestine, in which b-catenin levels are very high. Taken together these data reveal a link between eIF6 and Wnt signaling, perhaps at the level of ribosome recycling on b-catenin mRNA.

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