R406 induces DLBCL apoptosis via the intrinsic apoptotic pathway. R406-sensitive DLBCL cell lines were cultured with 4 μM of R406 or vehicle alone for 96 hours. Thereafter, cells were lysed and lysates were size-fractionated and immunoblotted with antibodies directed against caspase-9 (top panel), caspase-3 (middle panel), and caspase-8 (bottom panel).