Search

Nasopharyngeal carcinoma ( NPC) is a cancer common in southern China and South East Asia that is causally linked to Epstein-Barr virus ( EBV) infection. Here, we demonstrate that NPC displays frequent dysregulation of the Hedgehog ( HH) pathway, a pathway implicated in the maintenance of stem cells, but whose aberrant activation in adult tissues can lead to cancer. Using authentic EBV-positive carcinoma-derived cell lines and nasopharyngeal epithelial cell lines latently infected with EBV as models for NPC in vitro, we show that EBV activates the HH signalling pathway through autocrine induction of SHH ligand. Moreover, we find that constitutive engagement of the HH pathway induces the expression of a number of stemness-associated genes and imposes stem-like characteristics on EBV-infected epithelial cells in vitro. Using epithelial cells expressing individual EBV latent genes detected in NPC, we show that EBNA1, LMP1, and LMP2A are all capable of inducing SHH ligand and activating the HH pathway, but only LMP1 and LMP2A are able to induce expression of stemness-associated marker genes. Our findings not only identify a role for dysregulated HH signalling in NPC oncogenesis, but also provide a novel rationale for therapeutic intervention. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Gene expression profiling has recently enabled the reclassification of aggressive non-Hodgkin lymphomas (aNHL) into distinct subgroups. In Burkitt lymphoma (BL) aberrant c-Myc activity results from IG-MYC translocations. However, MYC aberrations are not limited to BLs and then have a negative prognostic impact. In this study, we investigated to which extent aberrant c-Myc activity plays a functional role in other aNHL and whether it is independent from MYC translocations. Based on a combined microarray analysis of human germinal center (GC) B cells transfected with c-Myc and 220 aNHLs cases, we developed a 'c-Myc index.' This index measures the extent to which lymphomas express c-Myc responsive genes. It comprises genes that are affected in a variety of tumors compared to normal tissue. This supports the view that aberrant c-Myc expression in GC B cells triggers a tumor-like expression pattern. As expected, the 'c-Myc index' is very high in molecular Burkitt lymphoma (mBL), but more importantly also high within other aNHL. It constitutes a negative prognostic marker independent of established risk factors and of the presence of a MYC translocation. Our data provide new insights into the role of c-Myc activity in different lymphomas and raises the question of treatment changes for those patients under risk. [ABSTRACT FROM AUTHOR]