1969

EPHA2

EPH receptor A2;EPHA2;EPH receptor A2

ephrin type-A receptor 2|epithelial cell receptor protein tyrosine kinase|soluble EPHA2 variant 1|tyrosine-protein kinase receptor ECK

1p36

protein-coding

Eph receptor 2 (EphA2) overexpression is frequently accompanied by the loss of its cognate ligand during tumor progression. However, the molecular mechanism of this ligand-independent promotion of tumor by EphA2 remains unclear in highly malignant and fatal cholangiocarcinoma (CC). We examined the biological role of EphA2 in tumor growth and metastasis in CC tissues and cells according to the degree of differentiation and we explored the downstream signaling pathways of EphA2. Growth factor-mediated EphA2 overexpression itself leads to the activation of the mammalian target of rapamycin complex 1 (mTORC1) and extracellular signal-regulated kinase (ERK) pathways through ligand-independent activation of EphA2 (phosphorylation of S897). An in vitro soft agar assay and in vivo orthotopic or subcutaneous tumor model showed that EphA2 enhanced colony formation and accelerated tumor growth, and which seemed to be mainly associated with Akt (T308)/mTORC1 activation. Aberrant expression and activation of EphA2 was also associated with poorer differentiation and higher metastatic ability. Enhanced metastatic ability was also observed in an orthotopic tumor model or lung metastasis model, correlating with Pyk2(Y402)/c-Src/ERK activation in addition to activation of the canonical Raf/MEK/ERK pathway. The mTORC1 and Raf/Pyk2 pathways also appeared to affect each other. These results suggest that growth factor-mediated EphA2 might be involved in tumor growth and metastasis through activation of the mTORC1 and Raf/Pyk2 pathways. Therapeutic strategies that target EphA2 and its downstream effectors may be useful to control CC. (HEPATOLOGY 2013;57:2248-2260).

Recently, overexpression of EphA2, a member of the Eph family of receptor tyrosine kinases, has been reported in several cancers. Reduced expression of E-cadherin, an intercellular adhesion molecule of epithelial cells, has been reported to be associated with aggressive clinicopathological phenotypes in various cancers. In epithelial cells, EphA2 and E-cadherin co-localize to sites of cell-cell contact, and it has been shown that E-cadherin regulates EphA2. This study aimed to clarify the relationship between the expression of the EphA2 and E-cadherin proteins and clinicopathological characteristics, with reference to the expression levels of both EphA2 and E-cadherin, in patients with colorectal cancer. We performed immunohistochemical staining of EphA2 and E-cadherin with EphA2 and E-cadherin monoclonal antibodies in samples from 194 primary lesions of colorectal cancer. The expression level of EphA2 had a statistically significant relationship with liver metastasis, lymphatic vessel invasion and clinical stage (p=0.0477, 0.0316 and 0.0467, respectively). In addition, the positivity rate of EphA2 was significantly higher in primary lesions with lymph node metastasis than in those without metastasis (p=0.0014). However, the expression level of E-cadherin had an inverse relationship with both differentiation level of the tumor and lymphatic vessel invasion (p=0.0430 and 0.0320, respectively). Furthermore, a significant relationship between the expression of EphA2 and E-cadherin was observed. In conclusion, our study revealed that the overexpression of EphA2 protein in colorectal carcinoma tissue correlates closely with cancer progression and hematogenous and lymphogenous metastasis, suggesting that both EphA2 and E-cadherin may play an important role in tumor metastasis in colorectal cancer.

In this study, gastric cancer progression was correlated with the over-expression of erythropoietin-producing hepatocellular (Eph)A2 receptor and down-expression of epithelial cadherin (E-cadherin). Immunohistochemistry of EphA2 and E-cadherin were performed on these tumor samples from 165 primary lesions of gastric cancer. The results showed that expression of EphA2 was obviously increased in gastric cancer tissues (P < 0.01), which was positively correlated with the depth of cancer invasion, tumor-node-metastasis (TNM) stage and lymph node metastasis (P < 0.05). Meanwhile, the expression of E-cadherin was significantly reduced (P < 0.01), which was negatively correlated with the depth of cancer invasion, grade of tumor differentiation, TNM stage and lymph node metastasis (P < 0.05). The correlation between EphA2 and E-cadherin expression was negative (r = -0.198, P = 0.011). In conclusion, either the over-expression of EphA2 or the down-expression of E-cadherin is correlated with cancer progression and lymphogenous metastasis in gastric cancer, suggesting that both of them may play an important role in tumor progression and metastasis.

This study aims to investigate the significance of erythropoietin-producing hepatocellular (Eph)A2 expression and the mechanism by which EphA2 is involved in the epithelial-mensenchymal transition (EMT) of gastric cancer cells. EphA2 expression levels were upregulated and positively correlated with metastasis and EMT markers in human gastric cancer specimens. Modulation of EphA2 expression levels had distinct effects on cell proliferation, cell cycle, migration, invasion and morphology in the gastric cancer cell lines SGC7901 and AGS in vitro and in vivo. Overexpression of EphA2 resulted in the upregulation of the EMT molecular markers N-cadherin and Snail, as well as the Wnt/beta-catenin targets TCF4, Cyclin-D1 and c-Myc, while silencing EphA2 using short hairpin RNA had the opposite effect. Furthermore, inhibition of the Wnt/beta-catenin pathway by XAV939 negated the effect of EphA2 overexpression, whereas activation of the Wnt/beta-catenin pathway by LiCl impaired the effect of the EphA2 knockdown on EMT. These observations demonstrate that EphA2 upregulation is a common event in gastric cancer specimens that is closely correlated with cancer metastasis and that EphA2 promotes EMT of gastric cancer cells through activation of Wnt/beta-catenin signaling.

OBJECTIVE: To evaluate the expression of EphA2 protein in tissue specimens and cell lines of laryngeal squamous cell carcinoma (LSCC), and to further study the correlation of EphA2 protein expression with clinicopathological characteristics and prognosis in LSCC. METHODS: Western blot was applied to assess the EphA2 protein expression in LSCC cell line Hep-2 cells and the head and neck immortalized epithelial cell line NP-69 cells. Immunohistochemical staining was performed on paraffin sections of 88 cases of LSCC specimens and 16 cases of adjcent normal tissue samples to investigate the EphA2 protein expression, and to futher elucidate its correlation with clinicopathological characteristics. RESULTS: Compared with the NP-69 cells, EphA2 expression in LSCC cell line Hep-2 cells was upregulated. The positive rates of EphA2 expression in LSCC and adjcent normal tissues samples were 80.7% and 43.8%, respectively, with a significant difference between the two groups (P < 0.001). EphA2 overexpresion was closely correlated with clinical stage (I + II/III + IV, P = 0.005), metastasis (P = 0.025) and recurrence (P = 0.021) in LSCC. Furthermore, patients with EphA2 overexpression had poorer tumor-free survival and 5-year overall survival compared with that in patients with low EphA2 expression (33.3% vs. 63.2%, P = 0.003; 46.7% vs. 81.6%, P = 0.002). EphA2 expression combined with clinical stage provided a better predictive value in prognosis. Univariate and multivariate Cox regression analysis revealed that EphA2 expression is an independent prognostic factor for patients with LSCC (P = 0.019). CONCLUSIONS: The results of this study demonstrate that EphA2 protein expression is significantly increased in LSCC tissues and cell lines, and EphA2 protein overexpression is associated with tumor recurrence, metastasis and poorer prognosis in LSCC patients. These results suggest that EphA2 may play a critical role in the initiation and progression of LSCC, implicating EphA2 as a valuable marker for the prediction of recurrence, metastasis and prognosis in LSCC.

OBJECTIVE: To observe the expression of EphA2, and investigate its correlation with the development, progression, invasion, metastasis, angiogenesis and prognosis in nasopharyngeal carcinoma(NPC). METHOD: Immunohistochemical staining was used to determine the expression level of EphA2 protein in 61 cases NPC and 20 cases chronic nasopharyngitis samples. The clinically pathological data and results of follow-up were collected. Microvessel density (MVD) was also measured by immunohistochemical staining method with CD34 in NPC. RESULT: The positive rate of EphA2 protein staining in NPC was 60.66% (37/61), while that in nasopharyngitis samples was 10.0% (2/20). The positive rates of EphA2 protein in NPC were 27.27% (3/11) in stage I, 56.25% (9/16) in stage II, 68.19% (15/22) in stage III, and 83.33% (10/12) in stage IV. The positive expressions of EphA2 in T1 + T2 and T3 + T4 with neck lymph node and distant metastasis were 58.33% (7/12) and 88.89% (16/18) respectively, while those in T1 +T2 and T3 + T4 without metastasis were 31.25% (5/16) and 50.00% (6/12) respectively. The cumulative survival of patients in the EphA2 positive group at 5 years was only 0.324 (12/37), while 0.500 (12/24) in the EphA2 negative group. The positive expression of EphA2 protein was correlated with the clinical stage, the neck lymph node metastasis and distant metastasis, and prognosis of NPC, respectively (P < 0.05). MVD in EphA2 protein positive group (45.32 +/- 4.91) was significantly higher than that in EphA2 protein negative group (28.69 +/- 3.99, P < 0.01). CONCLUSION: EphA2 may play an important role in the development and progression of NPC. It is closely associated with the invasion, metastasis, angiogenesis and prognosis of NPC.

Ligand-activated Eph tyrosine kinases regulate cellular repulsion, morphology, adhesion, and motility. EphA2 kinase is frequently up-regulated in several different types of cancers, including prostate, breast, colon, and lung carcinomas, as well as in melanoma. The existing data do not clarify whether EphA2 receptor phosphorylation or its simple overexpression, which likely leads to Eph kinase-independent responses, plays a role in the progression of malignant prostate cancer. In this study, we address the role of EphA2 tyrosine phosphorylation in prostate carcinoma cell adhesion, motility, invasion, and formation of metastases. tumor cells expressing kinase-deficient EphA2 mutants, as well as an EphA2 variant lacking the cytoplasmic domain, are defective in ephrinA1-mediated cell rounding, retraction fiber formation, de-adhesion from the extracellular matrix, RhoA and Rac1 GTPase regulation, three-dimensional matrix invasion, and in vivo metastasis, suggesting a key role for EphA2 kinase activity. Nevertheless, EphA2 regulation of cell motility and invasion, as well as the formation of bone and visceral tumor colonies, reveals a component of both EphA2 kinase-dependent and -independent features. These results uncover a differential requirement for EphA2 kinase activity in the regulation of prostate carcinoma metastasis outcome, suggesting that although the kinase activity of EphA2 is required for the regulation of cell adhesion and cytoskeletal rearrangement, some distinct kinase-dependent and -independent pathways likely cooperate to drive cancer cell migration, invasion, and metastasis outcome.