EphA2 Expression Is a Key Driver of Migration and Invasion and a Poor Prognostic Marker in Colorectal Cancer

Abstract

Purpose: EphA2, a member of the Eph receptor tyrosine kinases family, is an important regulator of tumor initiation, neovascularization, and metastasis in a wide range of epithelial and mesenchymal cancers; however, its role in colorectal cancer recurrence and progression is unclear.Experimental Design: EphA2 expression was determined by immunohistochemistry in stage II/III colorectal tumors (N ¼ 338), and findings correlated with clinical outcome. The correlation between EphA2 expression and stem cell markers CD44 and Lgr5 was examined. The role of EphA2 in migration/invasion was assessed using a panel of KRAS wild-type (WT) and mutant (MT) parental and invasive colorectal cancer cell line models.Results: Colorectal tumors displayed significantly higher expression levels of EphA2 compared with matched normal tissue, which positively correlated with high CD44 and Lgr5 expression levels. Moreover, high EphA2 mRNA and protein expression were found to be associated with poor overall survival in stage II/III colorectal cancer tissues, in both univariate and multivariate analyses. Preclinically, we found that EphA2 was highly expressed in KRASMT colorectal cancer cells and that EphA2 levels are regulated by the KRAS-driven MAPK and RalGDS-RalA pathways. Moreover, EphA2 levels were elevated in several invasive daughter cell lines, and downregulation of EphA2 using RNAi or recombinant EFNA1 suppressed migration and invasion of KRASMT colorectal cancer cells.Conclusions: These data show that EpHA2 is a poor prognostic marker in stage II/III colorectal cancer, which may be due to its ability to promote cell migration and invasion, providing support for the further investigation of EphA2 as a novel prognostic biomarker and therapeutic target.

Evaluation of EphA2 and EphB4 as Targets for Image-Guided Colorectal Cancer Surgery

“…The higher EphB4 expression in colon cancer compared to normal mucosa was previously shown at the mRNA level in 62 tissue pairs, with validation at the protein level in only a few samples [14]. Although we did not find a significant correlation between EphA2 or EphB4 expression and the stage or differentiation grade of the tumors, earlier studies found both EphA2 and EphB4 to be preferentially up-regulated in the early cancer stages (stages I and II) [5][6][7][8][9]15]. Over-expression in early colorectal cancer stages is particularly advantageous for imaging during surgery, given the increased difficulty in distinguishing normal and tumor tissue morphologically and the fact that for early stage tumors surgery is often not accompanied by chemotherapy.…”

“…Multiple publications have shown that EphA2 overexpression is strongly correlated with tumor progression, and consequently high EphA2 levels are associated with worse patient survival [8,13,16]. High EphB4 expression has also been correlated with poor patient survival [17][18][19], although some studies have also found an opposite correlation [15].…”

Challenging the Cancer Molecular Stratification Dogma: Intratumoral Heterogeneity Undermines Consensus Molecular Subtypes and Potential Diagnostic Value in Colorectal Cancer

“…These data collectively challenge the general assumption that tumors classified as mesenchymal, or in the CMS4 subgroup, have undergone widespread EMT, resulting in lower levels of epithelial-associated traits in the tumor cell compartment, when actually these tumors have a higher component of stromal (particularly fibroblast) infiltration. Although IHC-based analysis of colorectal cancer tumors has shown that neoplastic epithelial cells expressing stem-like properties have a poor prognosis (15)(16)(17), our findings emphasize that the CMS4 subgroup represents tumors with higher transcription levels of mesenchymal-associated genes, which can be attributed to their overall stromal-rich, and in particular fibroblast, architecture.…”

Emerging and Diverse Functions of the EphA2 Noncanonical Pathway in Cancer Progression

“…64) Dunne et al found that EphA2 Ser-897 and EphA2 Tyr-772 as well as total EphA2 were upregulated in an invasive colorectal cancer cell line harboring the KRAS active mutation. 42) Of note, the stem cell markers CD44 and Lgr5 also were increased in these cells, suggesting EphA2 Ser-897 may be involved in cancer stemness. De Robertis et al reported that colon adenocarcinoma cells with high EphA2 expression levels isolated from the AOM/DSS mouse model showed higher levels of stem cell markers and lower levels of differentiation markers than the low-EphA2 population.…”

“…41) Many reports showed that patients with low ephrin-A1 expression had a poor prognosis, suggesting the existence of EphA2 tyrosine kinase-independent regulation. 31,42,43) Thirty-seven phosphorylation sites are identified within the intracellular domain of EphA2 in the PhosphoSitePlus database. 44) Among them, 25 phosphorylation sites are serine and threonine residues.…”