Abstract 1625: Role of EphB4 in esophageal cancer: Expression, amplification, and therapeutic inhibition

Abstract

EphB4 is a member of the largest family of receptor tyrosine kinases (RTKs), classically associated with neural development and vascular patterning in embryonic life. The cellular responses to Eph receptor stimulation by their ephrin ligands are important in mediating a wide range of biological activities, including angiogenesis, cell segregation, cell attachment, shape, and motility. EphB4 has been showed to play an oncogenic role in a number of tumors, and we report the first investigation into its role in esophageal cancer, a disease whose survival has not improved and would benefit from the identification of new targets in its treatment. We have addressed this need by exploring the Eph/ephrin receptor tyrosine kinase pathway. We utilized tissues archived at the University of Chicago as well as commercially purchased TMAs to evaluate the expression of EphB4 by IHC. Approximately 93 squamous cell carcinoma, 100 adenocarcinoma and 25 adjacent normal control samples were utilized. In addition, four adenocarcinoma and nine squamous cell carcinma cell lines were used for in vitro studies. Statistical analysis of IHC data showed a consistently higher expression of EphB4 in both squamous and adenocarcinoma compared to adjacent normal tissue. A statistically significant correlation was established between EphB4 expression and higher grades of squamous cell carcinoma, suggesting that overexpression of EphB4 in squamous cell carcinoma is directly linked to clinically aggressive tumors. The EphB4 gene was found amplified in 8/16 squamous cell carcinoma (30% with a gene copy number ≥ 3, 30% with >8 copies and 10% with a copy number of 20. Of the adenocarcinomas, 3/7 samples were amplified (43% with a gene copy number of ≥4, and 14% >8 copies). Three of 9 squamous cell carcinoma cell lines had a gene copy number ≥4 and rest of them had no significant variation. Only one of four adenocarcinoma cell lines had an increased gene copy number. In vitro experiments with EphB4 specific siRNA inhibited the motility and proliferation of cultured cells and the inhibition of EphB4 specifically abrogated the phosphorylation of functional proteins associated with cell motility and proliferation, especially that of phospho-FAK and phospo-AKT, the expression of which were abrogated completely by the inhibition of EphB4. Our data imply that EphB4 plays a crucial role in esophageal cancer and should be further evaluated as a therapeutic target in this disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1625. doi:10.1158/1538-7445.AM2011-1625

The role of Eph receptors in cancer and how to target them: novel approaches in cancer treatment

“…EphB4 has a few downstream effector molecules that contribute to its oncogenic role in some cancers. In ovarian cancer cell lines, the inhibition of EphB4 leads to increased apoptosis, possibly induced by an inhibition of the protein levels of Akt and mTor, which is similar to the role of EphB4 in esophageal cancer [105,106]. Moreover, in prostate cancer EphB4 stimulates integrin beta8, which could promote angiogenesis and in a breast cancer cell line, EphB4 promotes the Ras/c-Raf pathway, possibly through promoting protein phosphatase 2.…”