Department of Pediatrics Hematology and Oncology, University of Miami Miller School of Medicine, Miami, Florida, USA.
PLoS One. 2013 Aug 23;8(8):e74420. doi: 10.1371/journal.pone.0074420. eCollection 2013.
The outcome of patients with resistant phenotypes of acute lymphoblastic leukemia (ALL) or those who relapse remains poor. We investigated the mechanism of cell death induced by metformin in Bp- and T-ALL cell models and primary cells, and show that metformin effectively induces apoptosis in ALL cells. Metformin activated AMPK, down-regulated the unfolded protein response (UPR) demonstrated by significant decrease in the main UPR regulator GRP78, and led to UPR-mediated cell death via up-regulation of the ER stress/UPR cell death mediators IRE1α and CHOP. Using shRNA, we demonstrate that metformin-induced apoptosis is AMPK-dependent since AMPK knock-down rescued ALL cells, which correlated with down-regulation of IRE1α and CHOP and restoration of the UPR/GRP78 function. Additionally rapamycin, a known inhibitor of mTOR-dependent protein synthesis, rescued cells from metformin-induced apoptosis and down-regulated CHOP expression. Finally, metformin induced PIM-2 kinase activity and co-treatment of ALL cells with a PIM-1/2 kinase inhibitor plus metformin synergistically increased cell death, suggesting a buffering role for PIM-2 in metformin's cytotoxicity. Similar synergism was seen with agents targeting Akt in combination with metformin, supporting our original postulate that AMPK and Akt exert opposite regulatory roles on UPR activity in ALL. Taken together, our data indicate that metformin induces ALL cell death by triggering ER and proteotoxic stress and simultaneously down-regulating the physiologic UPR response responsible for effectively buffering proteotoxic stress. Our findings provide evidence for a role of metformin in ALL therapy and support strategies targeting synthetic lethal interactions with Akt and PIM kinases as suitable for future consideration for clinical translation in ALL.
耐药表型的急性淋巴细胞白血病（ALL）或复发患者的预后仍然较差。我们研究了二甲双胍在 Bp-和 T-ALL 细胞模型和原代细胞中诱导细胞死亡的机制，并表明二甲双胍能有效诱导 ALL 细胞凋亡。二甲双胍激活 AMPK，下调未折叠蛋白反应（UPR），主要 UPR 调节因子 GRP78 显著减少，并通过上调 ER 应激/UPR 细胞死亡介质 IRE1α 和 CHOP 导致 UPR 介导的细胞死亡。使用 shRNA，我们证明二甲双胍诱导的细胞凋亡依赖于 AMPK，因为 AMPK 敲低可挽救 ALL 细胞，这与 IRE1α 和 CHOP 的下调以及 UPR/GRP78 功能的恢复相关。此外，雷帕霉素，一种已知的 mTOR 依赖性蛋白合成抑制剂，可挽救细胞免受二甲双胍诱导的凋亡，并下调 CHOP 表达。最后，二甲双胍诱导 PIM-2 激酶活性，并用 PIM-1/2 激酶抑制剂和二甲双胍共同处理 ALL 细胞可协同增加细胞死亡，表明 PIM-2 在二甲双胍的细胞毒性中起缓冲作用。用 Akt 靶向药物与二甲双胍联合治疗也显示出类似的协同作用，支持我们最初的假设，即 AMPK 和 Akt 在 ALL 中对 UPR 活性发挥相反的调节作用。总之，我们的数据表明，二甲双胍通过触发内质网和蛋白毒性应激诱导 ALL 细胞死亡，同时下调负责有效缓冲蛋白毒性应激的生理 UPR 反应。我们的研究结果为二甲双胍在 ALL 治疗中的作用提供了证据，并支持针对 Akt 和 PIM 激酶的合成致死相互作用的策略，适合未来在 ALL 中进行临床转化的考虑。
