Expression and clinical significance of EphA8 in colon cancer / 国际肿瘤学杂志

Objective To investigate the expression of EphA8 in colon cancer and its clinical significance.Methods Real-time quantitative polymerase chain reaction (RT-PCR) and Western blot were respectively used to assess the expressions of EphA8 mRNA and protein in normal colon mucosa cell line and colon cancer cell lines.Immunohistochemistry for EphA8 and vascular endothelial growth factor (VEGF) were performed in 98 cases of colon cancer and 12 matched normal mucosa tissues.CD31 immunohistochemical staining was used for microvascular density (MVD) counting.The relationships between the expression of EphA8 and the expression of VEGF and MVD,the clinical pathological significance,and the prognosis of patients were analyzed by statistical methods.Results EphA8 mRNA expressions were significantly higher in colon cancer cell lines than those in normal mucosa cell line (t =11.98,13.54,P ＜0.001).EphA8 protein expressions were significantly higher in colon cancer cell lines than those in normal mucosa cell line (t =4.63,P =0.006;t =4.92,P =0.004).The high expression of EphA8 was closely related to tumor size (x2 =22.97,P＜0.001),TNM stage (P＜0.001),differentiated degree (P =0.007)and lymph node metastasis (P＜0.001),distant metastasis (x2 =6.97,P =0.008) and poor survival rote (x2 =17.3,P ＜0.001).But it was not associated with the gender and age (x2 =1.36,P =0.30; x2 =0.83,P=0.44).Besides,EphA8 had positive correlation with the VEGF and MVD (r =0.434,P ＜0.001; r =0.584,P ＜0.001).Conclusion EphA8 may play important roles in the development and metastasis of colon cancer,which has potential clinical values in the therapeutic intervention and prognosis of colon cancer.

Ectopic Expression of Ephrin-A5 Under the EphA8 Promoter at the Anterior Region of the Superior Colliculus

EphA/ephrin-A mediated signaling has emerged as a key mechanism regulating axon guidance and topographic mapping, particularly in the well-characterized visual system from the retina to the superior colliculus (SC). In this study, EphA8 bacterial artificial chromosome (BAC) was manipulated to contain a floxed eGFP and human ephrin-A5 expression cassette using homologous recombination method. In the mice containing the recombinant BAC, it was shown that GFP is expressed in an anterior>posterior gradient in the SC. Furthermore, when these mice were crossed with the transgenic mice expressing Cre under the EphA8 promoter, it was evident that a GFP expression cassette was eliminated, and that human ephrin-A5 was ectopically expressed in the anterior region of the SC. This transgenic model would be useful to analyze the role of ephrin-A5 in the SC during the retinocollicular topography formation.

Over-expression of EphrinA2 in the Anterior Region of the Developing Mouse Midbrain and Diencephalon / 대한해부학회지

The Eph family is thought to exert its function through the complementary expression of receptors and ligands. The dorsal mesencephalon appears to be segmented into two broad regions demarcated by the mutually exclusive expression of EphA receptors and ephrinA ligands. In this study, we analyzed transgenic embryos expressing ephrinA2 in the anterior region of the developing midbrain where the EphA8 receptor is expressed. First, 1% of transgenic embryos showed cephalic neural tube closure defects. Second, it was confirmed that mis-expression of ephrin-A2 in the anterior mesencephalon induced an increase in the EphA8 tyrosine kinase activity. Accordingly, an increased MAPK activity was also detected in the anterior mesencephalon of E14.5 transgenic embryo. Third, cell adhesion assay revealed that mis-expression of ephrinA2 promoted cell attachment to fibronectin. Taken together, these findings suggest that co-expression of EphA receptors and ephrinA ligands significantly alter cell behaviors including cell adhesion.

In vivo Mapping of the Cis-acting Element Responsible for Spatial Regulation of the EphA8 Gene Expression in Mesencephalon / 대한해부학회지

This study was aimed to map the 1 kb cis-acting DNA of ephA8 gene, which regulates the spatial and temporal expression in the anterior mesencephalon. It was demonstrated that the 1 kb ephA8 enhancer DNA was sufficient to drive the lacZ expression to the anterior mesencephalon under the human beta-globin minimal promoter. It was also found that a 180 bp within the 1 kb enhancer DNA was highly conserved between human and mouse, and that this 180 bp DNA was capable of inducing the lacZ expression in the anterior mesencephalon under the ephA8 or human beta-globin basal promoter. Further analysis using 5'-55 bp deleted or 3'-55 bp deleted mutant DNA revealed that the 55 bp portion present at the 3'-end of 180 bp DNA was critical for the regulation of ephA8 gene expression in the anterior mesencephalon. Taken together, these results indicate that 180 bp ephA8 enhancer DNA contains cisacting elements for the regulation of ephA8 gene expression in the anterior mesencephalon.