Frequent RelB DNA-binding activity in ABC and GCB DLBCL cell lines. (A) Whole cell extracts from 26 DLBCL cell lines were analyzed for NF-κB activity by using EMSA. Three representative cell lines are presented (1 ABC, MD901; 2 GCB, K231 and OCI-Ly8). For supershifts, extracts were incubated with the indicated antibodies before incubation with the labeled probe. RelB- and RelA-containing complexes are indicated. (B) Distribution of RelB DNA-binding activity as defined by using EMSA among GCB and ABC DLBCL cell lines (n = 26). (C) Top: prevalence of RelB activation as defined by using EMSA within ABC and GCB DLBCL cell lines (n = 26). Bottom: prevalence of ABC and GCB DLBCL cell lines within the positive RelB DNA-binding subgroup (n = 16). (D) Correlation between TRAF3 inactivating mutation/deletion (M/D) with RelB DNA-binding status (n = 19). P value by Fisher’s exact test. Color codes indicate the presence or absence of TRAF3 inactivating genetic alterations. (E) Percentage of TRAF3 M/D vs TRAF3 wild-type (WT) DLBCL cell lines showing a positive RelB DNA-binding status (n = 19). P value by Fisher’s exact test.