Most posttransplantation lymphoproliferative disorders (PTLDs) are associated with Epstein-Barr virus (EBV) infection. The EBV latent membrane protein 1 (LMP-1) is important in the transformation of B lymphocytes through its interaction with intracellular tumor necrosis factor receptor-associated factors (TRAFs) that, in turn, can activate transcription factors such as nuclear factor kappa B (NFkappaB) and Jun-N-kinase. Of the 6 members of the TRAF family, TRAF-1, TRAF-2, and TRAF-3 are most commonly associated with LMP-1. Recently, it has been suggested that LMP-1-induced TRAF activation is important in the pathogenesis of PTLDs.
To characterize the expression patterns of these proteins in PTLDs, we studied a series of well-characterized cases for expression of LMP-1, TRAF-1, TRAF-2, TRAF-3, and NFkappaB by immunohistochemical analysis.
A total of 27 specimens from 25 patients were analyzed for LMP-1, TRAF-1, TRAF-2, TRAF-3, and NFkappaB (active form) by immunohistochemical analysis. Expression of EBV-encoded RNA (EBER) was evaluated by in situ hybridization. Correlation between the expression of the different markers was performed using the Mantel-Haenszel chi(2) test. Cox proportional hazards analysis and Kaplan-Meier analysis with log-rank testing were used to analyze antigen expression and clinical outcome.
Ninety-six percent of PTLDs expressed NFkappaB, 74% to 84% expressed TRAFs, 78% expressed EBER, and 77% expressed LMP-1. TRAF-1, TRAF-2, and TRAF-3 expression did not correlate with either EBER or LMP-1 expression. TRAF-2, but not TRAF-1 or TRAF-3, expression correlated with NFkappaB expression (P =.02).
These results suggest that TRAF molecules and active NFkappaB are expressed in PTLDs regardless of EBV positivity. Given the association of TRAF-2 and active NFkappaB expression, TRAF-2 may play an important role in regulating this transcription factor in PTLD.