Inhibition of BCR signaling suppresses cell recovery and NF-κB activation in ATMKO.CD3εKO B-cell lymphomas. ATMKO.CD3εKO B-cell lymphoma lines (closed symbols) and ATMKO T-cell lymphoma lines (open symbols) were cocultured with titrated amounts of PRT2667 (Syk inhibitor) (A), Ly317615 (PKCβ inhibitor) (B), or PCI-32765 (BTK inhibitor) (C). For panels A-C, viable cells were counted, and inhibition was calculated as described in “Materials and methods.” Data are representative of 3 independent experiments examining survival of 4 to 6 B-cell lymphomas and 2 to 4 T-cell lymphomas in each experiment. (D) Inhibition of BTK signaling suppresses NF-κB activation in ATMKO.CD3εKO tumors. Lymphoma cells were treated with DMSO or the BTK inhibitor PCI-32765 (100 nM) for the indicated time points and lysed, and sequential western blot analyses were performed to detect p-IkBα, total IkBα, and β-actin expression. Band intensities were quantitated and then normalized to β-actin. NF-κB activation was expressed as the p-Ikbα/IkBα ratio at each time point relative to the value at time = 0 hours. Data are representative 3 independent experiments examining NF-κB activation in 2 B-cell lymphomas. Signature analysis comparing genes downregulated in ATMKO.CD3εKO tumors (n = 2) treated with PCI-32756 (100 nM; 6 hours at 37°C) to genes downregulated in a human ABC DLBCL cell line similarly treated with PCI-32756 (E) or to an NF-κB signaling signature derived from human ABC DLBCL (F). Genes identified as downregulated in panels E-F were at least 1.3-fold downregulated in ≥50% of the samples analyzed at the 6-hour treatment point. P values for the overlaps and the genes common to both tumors are shown.