Xiang-Dan Cui1, Mi-Jin Lee1, Jong-Hyun Kim1, Pei-Pei Hao1, Lan Liu2, Goung-Ran Yu1, Dae-Ghon Kim1,*
1 Division of Gastroenterology and Hepatology, Department of Internal Medicine, Institute for Medical Science, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea
2 The Department of Pathology, Yanbian University Hospital, Yanji, Jilin, China.
*To whom correspondence may be addressed.
EphA2 over-expression 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 over-expression itself leads to the activation of the mTORC1 and 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. Enhance metastatic ability was also observed in 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.)
Keywords: Cholangiocarcinoma; EphA2; tumor growth; metastasis; mTORC1, Raf/Pyk2