Abstract 2469: Brentuximab vedotin-mediated immunogenic cell death
Authors: Gardai Shyra J. , Epp Angela , Law Che-Leung 
Published: August 2015

Abstract
Brentuximab vedotin (ADCETRIS®) is an antibody-drug conjugate (ADC) directed against CD30. It consists of an anti-CD30 monoclonal antibody conjugated to monomethyl auristatin E (MMAE), a microtubule-disrupting agent. Brentuximab vedotin is approved for the treatment of relapsed Hodgkin lymphoma (HL) and systemic anaplastic large cell lymphoma (ALCL). Brentuximab vedotin antitumor activity is due to the binding of the ADC to CD30-expressing cells, followed by internalization, and release of MMAE after proteolytic cleavage resulting in apoptotic cell death. While Brentuximab vedotin induced cell death has been extensively studied, its potential immune modulatory activity has yet to be explored. Normal apoptosis is non-immunogenic, however multiple chemotherapeutic agents have been shown to induce a unique form of cell death termed Immunogenic Cell Death (ICD). ICD is characterized by exposure of danger-associated molecular patterns (DAMPs), many of which are Toll-like receptor ligands, which can reinitiate the immune responses suppressed by the tumor microenvironment. To test whether Brentuximab vedotin mediated tumor cell death induced ICD the phenotypic characteristics of Brentuximab vedotin-killed CD30+ HL tumor cell lines was examined. Brentuximab vedotin, dose-dependently induced surface exposure of the hallmark ICD markers calreticulin and HSP90 to similar levels induced by oxaliplatin, a chemotherapeutic agent known to mediate ICD. Since ICD is downstream of the ER stress response, Brentuximab vedotin was assessed for its ability to induce ER stress. Brentuximab vedotin treatment upregulated the apoptotic ER sensor C/EBP homologous protein (CHOP) and induced the cleavage and activation of ATF6, a transcription factor required for induction of the ER stress response. ER stress response occurred concurrently with induction of ICD markers and preceded the appearance of active caspase 3/7. These results indicate that Brentuximab vedotin mediated disruption of the microtubule network, in addition to perturbing the cell division cycle and mitosis, also induces ER stress contributing to ICD-dependent cellular toxicity. The functional consequence of ICD is activation of an immune reaction. Thus, exposure of dendritic cells to Brentuximab vedotin-killed tumor cells evoked an inflammatory phenotype including an increase in co-stimulatory markers CD86 and MHC Class II antigens, and activation of NFkB, an intermediate of inflammatory signaling pathways. Taken together, this report suggests that CD30-expressing tumor cells killed by Brentuximab vedotin may potentially activate the innate immune system to initiate antitumor immune response. It also provides a rationale for exploring therapeutic strategies that combine Brentuximab vedotin with other immune stimulatory regimens.
Citation Format: Shyra J. Gardai, Angela Epp, Che-Leung Law. Brentuximab vedotin-mediated immunogenic cell death. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2469. doi:10.1158/1538-7445.AM2015-2469