Everolimus enhances the cytotoxicity of bendamustine in multiple myeloma cells through a network of pro-apoptotic and cell-cycle-progression regulatory proteins  

作　　者：Bo Lu Juan Li Jingxuan Pan Beihui Huang Junru Liu Dong Zheng 

机构地区：[1]Department of Hematology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China [2]Department ofPathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510089, China

出　　处：《Acta Biochimica et Biophysica Sinica》2013年第8期683-691,共9页生物化学与生物物理学报（英文版）

摘　　要：Bendamustine is a bifunctional alkylating agent with some efficacy in the treatment of newly diagnosed and relapsed/re- fractory multiple myeloma （MM）. Everolimus, an mamma- lian target of rapamycin （mTOR） inhibitor, is a additional promising chemotherapeutic agent that has efficacy in a variety of cancers. We investigated the individual and com- binational cytotoxic effects of these drugs in MM cell lines （RPMI8226 and MM1.S） and primary MM cells. Our results demonstrated a synergistic effect of these drugs, which was effective for both p53-wild-type and p-53-deleted MM cells, but was minimal in mononuclear cells from a healthy donor. Combination treatment with the two agents inhibited prolif- eration and promoted cytotoxicity and apoptosis as assessed by Annexin-V/PI staining, caspase-3 degradation, and PARP cleavage. Cell death was associated with the up-regulation of the pro-apoptotic protein Bax and the down-regulation of the anti-apoptotic proteins Mcl-I and survivin. The combination drug treatment also promoted a decrease in the levels of the downstream target proteins of the mTOR pathway, p70s6k, and 4EBP-1, as well as an increase in the level of phosphoryl- ation of the tumor suppressor protein p53 in MM1.S cells. p21 was also down-regulated upon treatment with the two drugs, suggesting a mechanism of sensitization through the release of cell cycle arrest. Our results demonstrate a network of regulatory factors that may contribute to the syn- ergistic cytotoxicity of everolimus and bendamustine, and provide a rationale for application for the combinatorial treatment of MM with alkylating agents and mTOR inhibi- tors in future clinical practice.Bendamustine is a bifunctional alkylating agent with some efficacy in the treatment of newly diagnosed and relapsed/re- fractory multiple myeloma （MM）. Everolimus, an mamma- lian target of rapamycin （mTOR） inhibitor, is a additional promising chemotherapeutic agent that has efficacy in a variety of cancers. We investigated the individual and com- binational cytotoxic effects of these drugs in MM cell lines （RPMI8226 and MM1.S） and primary MM cells. Our results demonstrated a synergistic effect of these drugs, which was effective for both p53-wild-type and p-53-deleted MM cells, but was minimal in mononuclear cells from a healthy donor. Combination treatment with the two agents inhibited prolif- eration and promoted cytotoxicity and apoptosis as assessed by Annexin-V/PI staining, caspase-3 degradation, and PARP cleavage. Cell death was associated with the up-regulation of the pro-apoptotic protein Bax and the down-regulation of the anti-apoptotic proteins Mcl-I and survivin. The combination drug treatment also promoted a decrease in the levels of the downstream target proteins of the mTOR pathway, p70s6k, and 4EBP-1, as well as an increase in the level of phosphoryl- ation of the tumor suppressor protein p53 in MM1.S cells. p21 was also down-regulated upon treatment with the two drugs, suggesting a mechanism of sensitization through the release of cell cycle arrest. Our results demonstrate a network of regulatory factors that may contribute to the syn- ergistic cytotoxicity of everolimus and bendamustine, and provide a rationale for application for the combinatorial treatment of MM with alkylating agents and mTOR inhibi- tors in future clinical practice.

关 键 词：EVEROLIMUS BENDAMUSTINE MYELOMA SYNERGY apoptosis 

分 类 号：Q25[生物学—细胞生物学] Q255