Kinase-inactive IKK mutants inhibit B-lymphoid transformation by BCR-ABL1. BM from non–5-FU–treated Balb/c donor mice was harvested and transduced with retrovirus expressing BCR-ABL1/GFP, BCR-ABL1/IKKαKM, or BCR-ABL1/IKKβKM. (A) Assessment of stromal-dependent B-lymphoid transformation and growth. Nomenclature is as in Figure 1E. (B) B-lymphoid colony formation in agarose. Transduced cells (2 × 106 per plate, in duplicate) were seeded in agarose as described in “Materials and methods.” Colony formation was assessed at day 14. Coexpression of IκBαSR (*P = .0063), IKKαKM (**P = .0082), and IKKβKM (***P = .0101) (Student t tests) significantly reduced B-lymphoid colony formation mediated by BCR-ABL1. (C) Quantification of nuclear RelA expression in primary B-lymphoid progenitors transformed by BCR-ABL1/GFP, BCR-ABL1/IKKαKM, or BCR-ABL1/IKKβKM (mean + SE). Cells were stained with antibody against RelA and analyzed by confocal microscopy. BCR-ABL1/IKKαKM– and BCR-ABL1/IKKβKM–transformed cells showed significantly reduced nuclear RelA compared with cells transformed by BCR-ABL1/GFP (*P < .0001, Student t test).
