Cell adhesion in zebrafish embryos is modulated by March 8.

March 8 is a member of a family of transmembrane E3 ubiquitin ligases that have been studied mostly for their role in the immune system. We find that March 8 is expressed in the zebrafish egg and early embryo, suggesting a role in development. Both knock-down and overexpression of March 8 leads to abnormal development. The phenotype of zebrafish embryos and Xenopus animal explants overexpressing March 8 implicates impairment of cell adhesion as a cause of the effect. In zebrafish embryos and in cultured cells, overexpression of March 8 leads to a reduction in the surface levels of E-cadherin, a major cell-cell adhesion molecule. Experiments in cell culture further show that E-cadherin can be ubiquitinated by March 8. On the basis of these observations we suggest that March 8 functions in the embryo to modulate the strength of cell adhesion by regulating the localization of E-cadherin.

Habenular commissure formation in zebrafish is regulated by the pineal gland-specific gene unc119c.

BACKGROUND: The zebrafish pineal gland (epiphysis) is a site of melatonin production, contains photoreceptor cells, and functions as a circadian clock pacemaker. Since it is located on the surface of the forebrain, it is accessible for manipulation and, therefore, is a useful model system to analyze pineal gland function and development. We previously analyzed the pineal transcriptome during development and showed that many genes exhibit a highly dynamic expression pattern in the pineal gland. RESULTS: Among genes preferentially expressed in the zebrafish pineal gland, we identified a tissue-specific form of the unc119 gene family, unc119c, which is highly preferentially expressed in the pineal gland during day and night at all stages examined from embryo to adult. When expression of unc119c was inhibited, the formation of the habenular commissure (HC) was specifically compromised. The Unc119c interacting factors Arl3l1 and Arl3l2 as well as Wnt4a also proved indispensible for HC formation. CONCLUSIONS: We suggest that Unc119c, together with Arl3l1/2, plays an important role in modulating Wnt4a production and secretion during HC formation in the forebrain of the zebrafish embryo.

Lithocholic acid upregulates uPAR and cell invasiveness via MAPK and AP-1 signaling in colon cancer cells.

The secondary bile acid lithocholic acid (LCA) induced expression of urokinase-type plasminogen activator receptor (uPAR) and enhanced cell invasiveness in colon cancer cells. A dominant negative mutant or a specific inhibitor of MEK-1 suppressed LCA-induced uPAR expression. Deletions and site-directed mutagenesis revealed that the AP-1 site was required for LCA-induced uPAR transcription. LCA-mediated enhanced cell invasiveness was partially abrogated by uPAR neutralizing antibody and inhibitors of both Erk-1/2 and AP-1. These results suggest that LCA induces uPAR expression via Erk-1/2 and AP-1 pathway and, in turn, stimulate invasiveness of human colon cancer cells.

Resveratrol inhibits tumor cell adhesion to endothelial cells by blocking ICAM-1 expression.

Resveratrol, a grape polyphenol, is thought to have anti-inflammatory, cardioprotective, and cancer preventive properties. However, the mechanisms by which resveratrol might produce these effects are not clearly defined. A study was performed on whether resveratrol could prevent tumor cells from adhering to endothelial cells, which is an essential step during tumor metastasis. Phorbol 12-myristate 13-acetate (PMA) induced human fibrosarcoma HT1080 cells to adhere to endothelial ECV304 cells. Resveratrol inhibited PMA-induced HT1080 cells adhesion in a dose-dependent manner. To further study the mechanisms of this resveratrol-mediated blockade of tumor cell adhesion, the expression of the cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin were examined. PMA induced ICAM-1 expression in HT1080 cells. In contrast, the expression of VCAM-1 and E-selectin were not altered by PMA treatment. The increase in tumor cell adhesion to endothelial cells following PMA treatment was partially inhibited by ICAM-1 siRNA or neutralizing antibodies. Resveratrol reduced the PMA-induced ICAM-1 expression in HT1080 cells as determined by RT-PCR, flow cytometry and ELISA. As the induction of ICAM-1 requires activation of the transcription factor NF-kappaB, the effects of resveratrol on the activation of this factor in HT1080 cells was also investigated. Resveratrol inhibited the PMA-induced NF-kappaB activation and NF-kappaB-dependent luciferase activity. These results suggest that resveratrol may exert an antimetastatic effect by inhibiting NF-kappaB activation and ICAM-1 expression, leading to suppression of tumor cell adhesion to endothelial cells.

Lysophosphatidic acid promotes cell invasion by up-regulating the urokinase-type plasminogen activator receptor in human gastric cancer cells.

There is a strong correlation between the overexpression of urokinase-type plasminogen activator receptor (uPAR) and gastric cancer invasion. This study examined the effect of phospholipid lysophosphatidic acid (LPA) on uPAR expression in human gastric cancer AGS cells and the underlying signal transduction pathways. Treating human gastric AGS cells with LPA induced the expression of uPAR mRNA and promoter activity in both a time- and dose-dependent manner. Small interfering RNA targeting for LPA receptors, dominant negative Rho-family GTPase (RhoA, Rac1, and Cdc42) and an expression vector encoding a mutated c-jun (TAM67) partially blocked the LPA-induced uPAR expression. Site-directed mutagenesis and electrophoretic mobility shift studies showed that the transcription factors activation protein-1 (AP-1) and nuclear factor (NF)-kappaB are essential for the LPA-induced uPAR transcription. In addition, AGS cells treated with LPA showed enhanced invasion, which was partially abrogated by the uPAR-neutralizing antibodies and inhibitors of Rho kinase, JNK, and NF-kappaB. This suggests that LPA induces uPAR expression through the LPA receptors, Rho-family GTPase, JNK, AP-1 and NF-kappaB signaling pathways, which in turn stimulates the cell invasiveness of human gastric cancer AGS cells.

Induction of apoptosis by the licochalcone E in endothelial cells via modulation of NF-kappaB and Bcl-2 Family.

Licochalcones have a variety of biological properties including anti-tumor, anti-parasitic and anti-bacterial activities. Recently, a new retrochalcone (licochalcone E, Lico-E) was isolated from the roots of Glycyrrhiza inflata (Chem. Pharm. Bull., 53, 2005, Yoon et al.) by cytotoxicity-guided fractionation. This study examined whether or not Lico-E-induced endothelial cell death occurs through apoptosis, and investigated molecular mechanisms involved in this process. Lico-E was found to suppress ECV304 cell growth and induce apoptosis. The induction of apoptosis by Lico-E was confirmed by the ladder-patterned DNA fragmentation, the presence of cleaved and condensed nuclear chromatin and the increased number of annexin V-positive cells. Lico-E could effectively inhibit the constitutive NF-kappaB activation, as revealed by the electrophoretic mobility shift assay and NF-kappaB-dependent luciferase reporter study. In addition, the Lico-E treatment caused a change in the Bax/Bcl-2 ratio that favored apoptosis. These results suggest that Lico-E induces endothelial cell apoptosis by modulating NF-kappaB and the Bcl-2 family.

SB203580, a P38 MAPK Inhibitor, Blocks in vitro Invasion by Human Gastric SNU-638 Cells.

PURPOSE: The role of P38 mitogen-activated protein kinase (MAPK) in gastric cancer invasion has not yet been determined. In this study, we examined the effects of SB203580, a specific P38 MAPK inhibitor, on the in vitro invasion of gastric cancer and upon the molecules involved in this process. MATERIALS AND METHODS: Human gastric cancer SNU-638 cells were maintained in RPMI 1640 supplemented with 10% FBS. BIOCOAT matrigel invasion chambers were used to examine in vitro invasiveness, zymography for gelatinase activity, CAT assay for uPA promoter activity and Western and Northern blotting to determine protein and mRNA levels, respectively. RESULTS: Treatment of SNU-638 cells with SB203580, a specific P38 MAPK inhibitor, reduced in vitro invasiveness, dose-dependently. SB203580 treatment was found to decrease both mRNA expression and uPA promoter activity in gastric SNU-638 cells. In vitro invasion of SNU-638 cells was partially abrogated by uPA-neutralizing antibodies. The activities of MMPs were not significantly altered by SB203580. CONCLUSION: Our results suggest that P38 MAPK is a potential therapeutic target for inhibiting uPA-dependent gastric tumor invasiveness and metastasis.