IRF8 role in lymphomagenesis. (A) Real-time RT-PCR–based measurement of IRF8 expression in 21 nodal DLBCLs studied with the capture/sequence methodology demonstrates higher levels in the 2 tumors with the IGH-IRF8 fusion (ID #3271 and #6614). (B) Immunohistochemistry examination confirms the overexpression of IRF8 in a biopsy with an IGH-IRF8 fusion (#6614) compared with 2 DLBCLs lacking this rearrangement (600×). (C) Ectopic expression of IRF8 in 3 DLBCL cell lines led to the emergence of a lymphomagenic profile characterized by heightened expression of BCL6 and AID and suppression of PRMD1. (D) DLBCL cells ectopically expressing IRF8 became significantly resistant to apoptosis induced by H202 and serum deprivation (*P < .01, Student t test); ctrl (control) and 10% indicate the basal apoptosis rate in cells exposed to vehicle or grown in media supplemented with 10% fetal bovine serum, respectively. Bars labeled 2% or 0% correspond to cells grown in serum-deprived conditions. All data points were collected in triplicate at 24 hours, and the results were confirmed in 3 independent biological replicates; the results displayed represent the mean and standard deviation of a biological replicate.