Abstract 2629: Carfilzomib, an irreversible proteasome inhibitor, induces caspase-dependent apoptosis and inhibits the growth of mantle cell lymphoma <i>in vitro</i> and in tumor-bearing SCID mice
Authors: Liang Zhang, Jianfei Qian, Jing Yang, Monette Aujay, Susan Demo, Qing Yi, Michael Wang
Journal: Cancer Research (2010)

Abstract Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma subtype with poor clinical outcome. The proteasome is a clinically proven therapeutic target for MCL. Bortezomib is a reversible proteasome inhibitor approved for MCL therapy. Carfilzomib, the new irreversible proteasome inhibitor with the chymotrypsin-like selectivity, has been shown to be effective in multiple myeloma. The objective of our study was to evaluate the therapeutic efficacy of carfilzomib in MCL in vitro and in vivo and to elucidate the mechanism of carfilzomib-mediated cell apoptosis. Four human MCL cell lines, SP53, MINO, Granta 519, and Jeko-1; freshly isolated primary MCL cells from four MCL patients; and normal peripheral blood mononuclear cells (PBMCs) from five healthy donors were treated with carfilzomib. A 3H-thymidine incorporation assay showed that carfilzomib not only inhibited the growth of the MCL cell lines but also freshly isolated MCL cells from patients in a dose-dependent manner. Interestingly, carfilzomib also inhibited the proliferation of PMA/ionomycin or anti-CD3 mAb/anti-CD28 mAb-activated, but not resting PBMCs from healthy donors. Flow cytometry analysis with fluorescence-labeled Annexin V and propidium iodide showed that carfilzomib induced apoptosis in both the cell lines and primary MCL cells in time- and dose-dependent manners. Notably, carfilzomib did not induce apoptosis of normal PBMCs. Carfilzomib was also effective and therapeutic in a MCL mouse model established in severe combined immunodeficient (SCID) mice. MINO cells (5 × 106) were inoculated subcutaneously into the right flank of SCID mice. Three weeks later, after palpable tumors developed, mice were treated intravenously with either vehicle alone (10% captisol) or carfilzomib (5 mg/kg) on day 1 and day2, dosing repeated weekly for 5 cycles. Tumor growth was significantly inhibited after carfilzomib treatment compared with vehicle control, and the survival time of tumor-bearing mice was significantly prolonged in the treatment group. Western blot analysis showed that apoptosis of MCL cells was induced through the activation of caspase cascades and PARP pathway. Pretreatment of cells with pan-caspase inhibitor (z-VAD) but not caspase-8 inhibitor (z-IETD) alone or caspase-9 inhibitor (z-LEHD) alone completely blocked carfilzomib-induced apoptosis. In conclusion, carfilzomib inhibited growth and induced apoptosis of MCL cells in vitro and in vivo. Cell apoptosis was induced via caspase-dependent signaling pathway. Our preclinical data indicate that carfilzomib may be used as a therapeutic agent in MCL treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2629.