Eeva Jonna, Nuutinen Ulla, Ropponen Antti, Mättö Mikko, Eray Mine, Pellinen Riikka, Wahlfors Jarmo, Pelkonen Jukka
Department of Clinical Microbiology, University of Kuopio, Yliopistoranta 1C, 70210, Kuopio, Finland.
Apoptosis. 2009 May;14(5):687-98. doi: 10.1007/s10495-009-0337-7.
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.
尽管抗CD20抗体利妥昔单抗在B细胞恶性肿瘤的癌症治疗中被广泛使用，但CD20诱导凋亡的信号通路仍不清楚。通过使用过表达显性负性（DN）-半胱天冬酶-9的滤泡性淋巴瘤细胞，我们证明半胱天冬酶-9的激活对于利妥昔单抗介导的凋亡至关重要。由半胱天冬酶-8激活介导的死亡受体途径不参与利妥昔单抗介导的凋亡，因为过表达FLIP（短）或FLIP（长）蛋白（半胱天冬酶-8激活的抑制剂）不能抑制利妥昔单抗诱导的凋亡。然而，抗Fas抗体激活的死亡受体途径对利妥昔单抗诱导的凋亡具有累加效应。Bcl-x（L）过表达使线粒体外膜稳定，抑制细胞死亡，表明线粒体在利妥昔单抗诱导的凋亡中起重要作用。有趣的是，利妥昔单抗诱导的细胞色素c释放和线粒体膜电位崩溃受半胱天冬酶-9调节。我们认为，半胱天冬酶-9和下游半胱天冬酶可能反馈至线粒体，以在内在凋亡过程中放大线粒体破坏。
