Effects of overexpression of ephrin-B2 on tumour growth in human colorectal cancer

Abstract

Eph receptor tyrosine kinases (RTKs) and their membrane-bound ligands, the ephrins, are essential for embryonic vascular development. Recently, it has been demonstrated that overexpression of specific Ephs and ephrins is associated with a poor prognosis in human tumours. Our group has shown that EphB and the ephrin-B subfamilies are coexpressed in human colorectal cancer, and ephrin-B2 is expressed at higher levels in human colorectal cancer than in adjacent normal mucosa. As the Eph/ephrin system is involved in embryologic vasculogenesis and ephrin-B2 is expressed ubiquitously in all colon cancers studied in our laboratory, we hypothesised that overexpression of ephrin-B2 in colon cancer cells may induce tumour angiogenesis and increase tumour growth. To investigate this hypothesis, we stably transfected KM12L4 human colon cancer cells with ephrin-B2 to study its effect on tumour growth in vivo. We found that overexpression of ephrin-B2 markedly decreased tumour growth in a mouse xenograft model. Immunohistochemical staining showed that ephrin-B2 transfectants produced higher tumour microvessel density and lower tumour cell proliferation than did parental or vector-transfected control cells. Using 51 Cr-labelled red blood cells (RBCs) to determine the functional blood volume in tumours, we demonstrated that tumours from ephrin-B2-transfected cells had significantly decreased blood volume compared with tumours from parental or vector-transfected control cells. Evaluation of in vitro parameters of cell cycle mediators demonstrated no alteration in the cell cycle. Although ephrin-B2 transfection increased tumour vessel density, the decrease in blood perfusion suggests that these vessels may be 'dysfunctional'. We conclude that overexpression of ephrin-B2 suppresses tumour cell growth and vascular function in this in vivo colon cancer model.

Gene expression profiling of human ovarian tumours

“…In situ hybridization confirmed the localisation of C7 mRNA in normal oesophageal epithelial cells and its disappearance in tumour cells. Two other genes that have been studied functionally with respect to growth suppression are ephrin-B2 and cold-inducible RNAbinding protein (Nishiyama et al, 1997;Liu et al, 2004). The latter has been shown to be downregulated in endometrial cancer in comparison to normal endometrium and tissue representing endometrial hyperplasia (Hamid et al, 2003).…”

Downregulation of EphA7 by hypermethylation in colorectal cancer

“…They also play a role in angiogenesis (Favre et al, 2003;Sullivan and Bicknell, 2003). In recent years, some of the Eph genes have been found to be overexpressed in human tumors, including neuroblastoma (Tang et al, 1999), lung carcinoma (Tang et al, 1999), gastric cancer (Kiyokawa et al, 1994;Kataoka et al, 2002), esophageal cancer (Miyazaki et al, 2003), breast cancer (Wu et al, 2004), and colorectal cancer (Stephenson et al, 2001;Liu et al, 2002Liu et al, , 2004Kataoka et al, 2004). Among the Eph family genes, relatively less attention has been directed toward EphA7 in human tumors, and the potential role of EphA7 in human oncology has not been addressed.…”

EphB2 is a Prognostic Factor in Colorectal Cancer

“…Nevertheless, it is not clear how Eph activity might make a functional contribution to the malignant phenotype. Indeed, notwithstanding reports implicating members of the EphB and ephrin B families in tumor progression (3,4,9), there is growing evidence to suggest that they may function as tumor suppressors (12,13). The aims of this study were to investigate the prognostic impact of EphB2 in colorectal cancer and to examine the relative levels of EphB2 expression across the adenoma to adenocarcinoma sequence.…”