NIK kinase protein accumulates in DLBCL tumor cells. (A) Cell lysates of normal/activated B cells and DLBCL cell lines were probed with NIK, TRAF2, TRAF3, BR3, c-IAP1, or c-IAP2 antibodies in Western blot analyses. Actin was used as a loading control. Box to the right indicates lighter exposure. (B) Cell lysates of DLBCL lymphoma patient biopsies were probed with NIK and BR3 antibodies in Western blot analysis. Actin was used as a loading control. Box to the right indicates lighter exposure. (C) DLBCL TMA analyzed for NIK and BR3 protein expression. Immunohistochemical analysis of DLBCL patient sample TMA of 43 primary DLBCL biopsies using antibodies against NIK and BR3 proteins. Tissue arrays with duplicate samples were scored using an automated analysis system for percentage of positive cells (> 30%) staining for NIK and BR3 protein in the DLBCL subgroups GCB, ABC, and non-profiled (NP; supplemental Figure 1). (D) Representative DLBCL TMA stained for NIK and BR3. Images are representative of the biopsy cores from the DLBCL TMA slides.