The involvement of mitochondria and the caspase-9 activation pathway in rituximab-induced apoptosis in FL cells

Abstract

Despite the wide use of anti-CD20 antibody rituximab in the cancer treatment of B cell malignancies, the signalling pathways of CD20-induced apoptosis are still not understood. By using dominant negative (DN)-caspase-9 overexpressing follicular lymphoma cells we demonstrated that the activation of caspase-9 was essential for rituximab-mediated apoptosis. The death receptor pathway mediated by caspase-8 activation was not involved in rituximab-mediated apoptosis since overexpression of FLIP(short) or FLIP(long) proteins, inhibitors of caspase-8 activation, could not inhibit rituximab-induced apoptosis. However, the death receptor pathway activation by anti-Fas antibodies showed an additive effect on rituximab-induced apoptosis. The stabilisation of the mitochondrial outer membrane by Bcl-x(L) overexpression inhibited cell death, showing the important role of mitochondria in rituximab-induced apoptosis. Interestingly, the rituximab-induced release of cytochrome c and collapse of mitochondrial membrane potential were regulated by caspase-9. We suggest that caspase-9 and downstream caspases may feed back to mitochondria to amplify mitochondrial disruption during intrinsic apoptosis.

The synthesized 2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one (CHM-1) promoted G2/M arrest through inhibition of CDK1 and induced apoptosis through the mitochondrial-dependent pathway in CT-26 murine colorectal adenocarcinoma cells

“…Activation of the caspase is the major mechanism that promotes apoptosis in response to death-inducing signals from cell surface receptors and mitochondria stress [21]. In this study, we observed the induction of caspase-9 and caspase-3 specific activities by CHM-1.…”

Anti-CD20 monoclonal antibodies: historical and future perspectives

“…When rituximab is sufficiently cross-linked it is capable of eliciting potent apoptotic responses in sensitive cell-lines via the intrinsic mitochondrial pathway. 54,55 However, cell death induced by non-hyper-crosslinked anti-CD20 mAb appears to be nonapoptotic and varies considerably depending on the mAb used, rituximab being relatively weak and tositumomab strong at inducing PCD. 56 It has never been formally shown what molecular process in vivo might mimic the high affinity crosslinking achieved with mAb reagents in vitro, although it is postulated that this could be performed by FcγR-bearing effector cells.…”

Cantharidin induces G2/M phase arrest and apoptosis in human colorectal cancer colo 205 cells through inhibition of CDK1 activity and caspase-dependent signaling pathways

“…Activation of caspase is one of the major mechanisms that promotes cell apoptosis responding to death receptor signal (extrinsic or death-receptor pathway) and mitochondrial stress (intrinsic or mitochondrial pathway) (34). In this study, we first demonstrated that CTD-reduced cell growth and cell death in colo 205 cells is through induction of cell apoptosis.…”