There is an opposite opinion indicating
There is an opposite opinion indicating that EphB plays a role as cancer suppressor. Batlle et al. showed that loss of EphB expression represented a critical step in CRC progression, and CRCs that lacked EphB2 expression have been correlated with more advanced tumour stage, poor differentiation, and poor survival (Batlle et al., 2005, Guo et al., 2006). No definitive conclusion has yet been reached regarding whether EphB4 acts as a tumour promoter or suppressor. In this study, we compared EphB4 expression in CRC tissues with paired normal mucosae using tissue microarrays and immunohistochemical staining. High EphB4 expression levels were observed in most CRC tissues and were significantly higher than that in normal tissue, demonstrating that EphB4 is overexpressed in CRC. Additionally, we showed that EphB4 is crucial for the growth of CRC Butaprost in vivo and that modulation of EphB4 protein expression has significant effects on CRC cell proliferation. No distant metastasis was detected in our xenograft models; however, there were other signs indicating the invasion and metastasis ability of tumours, such as vasculation, striated muscle, and connective tissue invasion at the tumour boundary. The tumour formation and metastasis ability of various cancer cell lines differ greatly. SW620, which is also a colorectal cell line, showed faster growth and more aggressive behaviour (data not shown). While western blot analysis showed that EphB4 was not expressed in SW620 cells and was moderately expressed in SW480 cells (Kumar et al., 2009), we choose SW480 as our experimental model. Overall, the pattern of EphB4 overexpression observed here in CRC tumours was remarkable. These results may indicate the heterogeneity of protein expression and functional mechanisms in tumour. An interesting study analysed the expression of all Eph and Ephrin variants in CRC. In all cases, at least one Eph gene was found in normal colons (EphA1, EphA2, EphB2, and EphB4), the expressions of which were observed at high levels in most CRCs. However, the expression of other Eph genes was lost in individual CRCs compared with corresponding normal tissues. This study suggested that expression of a single Eph gene was sufficient for effector function; however, individual CRCs need to be characterized to determine which Eph genes are highly expressed (Herath et al., 2012). The tumour microenvironment plays a crucial role in tumour initiation and progression. Angiogenesis is a procedure by which capillaries sprout from vessels and allow tumour cells to travel to distant sites from primary lesions, which is key to tumour progression. Given that angiogenesis involves a range of complex pathological processes, the precise mechanism remains unclear. This process involves three vital RTKs, including vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR), angiogenin/Tie receptor, and the Ephrin/Eph receptor systems. The VEGF/VEGFR system mainly induces the differentiation and angiopoiesis of vascular endothelia, yet the angiogenin/Tie system primarily affects maturation and quiescence of vasculature in later stages of angiopoiesis. The Eph/Ephrin system regulates vascular endothelial cell development and may play a vital role in the neovascularization assembly process by transmitting a bidirectional signal, transferring position guide information, and controlling asymmetric arteriovenous establishment (Heroult et al., 2006, Pasquale, 2010). EphB4/EphrinB2 is the specific growth factor of vascular endothelial cells in the Eph/Ephrin family. The Eph/EphrinB family plays an important role in vessel development and angiogenesis (Xue et al., 2014). Recent studies revealed that Eph is also involved in angiogenesis during the tumour pathogenesis and development (Li et al., 2015). There are limited studies focusing on the correlation between EphB4 in human CRC and microvascular patterns. Additionally, our data showed that EphrinB2 exhibited weakly positive staining, which did not change with the modulation of EphB4, either in human CRC tissues or in xenograft tumours. The study of Ferguson et al. (2013) described a similar phenomenon. Transfection of lung cancer cell line H661 with EphB4 resulted in a significant increase in cellular proliferation. When EphB4-transfected cells were treated with clustered EphrinB2/Fc, the degree of increased proliferation was similar to transfection with wild-type EphB4 alone. However, there was no statistically significant increase in proliferation in cells treated with ephrin-B2/Fc compared with non-treated cells, suggesting that the effects of EphB4 are ligand-independent. In contrast, the response to stimulation with EphrinB2/Fc on an EphB4-positive cell line (H446) and an EphB4-negative cell line (H526) indicated that EphrinB2/Fc-induced cellular proliferation was EphB4 dependent (Ferguson et al., 2013).