Inhibition of Syk activity in a panel of human NHL cell lines. The R406 Syk inhibitor was tested against several human NHL cell lines. (A) Representative cell viability plots as determined by MTS assay by concentration of the Syk inhibitor R406. Plots are separated by cell type: BL (left), DLBCL (center), and MCL (right). (B) Representative plots of PI stains of RAJI and BJAB human tumor B cells treated with DMSO (gray) or 2 μM R406 (black). The bar shows apoptotic cells staining for subdiploid DNA. The top percentage is for DMSO treatment and the bottom for R406.