Evidence that the NIK inhibitor 4H-isoquinoline-1,3-dione specifically targets the NCP. (A) Western blot analysis of 4H-isoquinoline-1,3-dione–treated L1236 HL cell line S100 cytoplasmic extracts for NIK and phospho-IKKα protein levels. (B) Western blot analysis of 4H-isoquinoline-1,3-dione–treated U-H01 HL cell line for NIK and phospho-IKKα protein levels. (C) Western blot analysis of 4H-isoquinoline-1,3-dione–treated L1236 HL cell line nuclear extracts for relB and p52 levels compared with TBP levels. (D) Western blot analysis of 4H-isoquinoline-1,3-dione–treated U-H01 HL cell line nuclear extracts for relB and p52 levels compared with TBP levels.