BAFF and APRIL activate NF-κB in malignant HRS cells and colocalize with TACI and BCMA receptors as well as TRAF2 signal transducer. (A) Cytoplasmic IKKγ, pIKKγ, pIκBα, IκBα, and actin (loading control) proteins in serum-starved HD-MyZ HRS cells incubated for 10 minutes (IKKγ and pIKKγ) or 2 hours (pIκBα, IκBα and actin) in the presence or absence of BAFF, APRIL, CD40L, or CD30L. pIKKγ bands were quantified (numbers below lanes) after normalization to IKKγ, while pIκBα and IκBα bands were quantified after normalization to actin. One of 3 experiments yielding similar results. (B) Nuclear p50, p65, and c-Rel proteins in HD-MyZ HRS cells incubated for 6 hours as in panel A. Bands were quantified (numbers below lanes) after normalization to Octamer-1 (Oct1), a ubiquitous nuclear protein (loading control). One of 3 experiments yielding similar results. (C) NF-κB and Oct1 binding to DNA in HD-MyZ HRS cells incubated for 6 hours as in panel A. Shifts correspond to p50-c-Rel and p50-p65 complexes as shown elsewhere.^31,39,58,65  One of 3 experiments yielding similar results. (D) Colocalization of BAFF, TACI, and TRAF2 (first column); BAFF, BCMA, and TRAF2 (second column); APRIL, TACI, and TRAF2 (third column); and APRIL, BCMA, and TRAF2 (fourth column) in L428 cells. DAPI (blue) stains nuclei in the last row. Turquoise (fourth row)–, yellow (fifth row)–, pink (sixth row)–, and white (seventh and eighth rows)–appearing areas indicate colocalization. Original magnification ×64. One of 4 experiments yielding similar results.