Differential signaling pathways are activated in the Epstein-Barr virus-associated malignancies nasopharyngeal carcinoma and Hodgkin lymphoma.

Abstract

EBV is associated with the epithelial cancer, nasopharyngeal carcinoma (NPC), and the lymphoid malignancy, Hodgkin lymphoma (HL). The EBV latent membrane proteins 1 and 2A are expressed in these tumors. These proteins activate the phosphatidylinositol 3'-OH kinase (PI3K)/Akt pathway, which is commonly activated inappropriately in malignancy. In this study, the status of Akt activation and its targets, glycogen synthase kinase-3beta (GSK-3beta) and beta-catenin, was investigated in NPC and HL clinical specimens. In the majority of HL and NPC specimens, Akt was activated, indicating an important role for this kinase in the development and/or progression of these tumors. Akt phosphorylates and inactivates GSK-3beta, a negative regulator of the proto-oncoprotein beta-catenin that is aberrantly activated in many cancers. GSK-3beta was phosphorylated and inactivated with concomitant nuclear beta-catenin accumulation in the majority of NPC specimens. The malignant cells of the majority of HL cases, however, did not have inactivated GSK-3beta and lacked nuclear beta-catenin expression. These data indicate that this signaling arm of PI3K/Akt is universal and important in NPC pathogenesis but is apparently not affected in HL. These findings point to a divergence in pathways activated by EBV in different cellular contexts.