Vilimanovich Urosh, Bosnjak Mihajlo, Bogdanovic Andrija, Markovic Ivanka, Isakovic Aleksandra, Kravic-Stevovic Tamara, Mircic Aleksandar, Trajkovic Vladimir, Bumbasirevic Vladimir
Institute of Histology and Embryology, School of Medicine, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia.
Clinic of Hematology, Clinical Centre of Serbia, School of Medicine, University of Belgrade, Belgrade, Serbia.
Eur J Pharmacol. 2015 Oct 15;765:415-28. doi: 10.1016/j.ejphar.2015.09.004. Epub 2015 Sep 8.
Statins exhibit anti-leukemic properties due to suppression of the mevalonate pathway by the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase, and subsequent depletion of cholesterol, farnesylpyrophosphate, and geranylgeranylpyrophosphate. We investigated the role of autophagy, a controlled intracellular self-digestion, in the anti-leukemic action of statins. Treatment with low concentrations (≤6 µM) of statins, cholesterol depletion, and specific inhibition of cholesterol synthesis and protein farnesylation or geranylgeranylation, all inhibited proliferation of leukemic cell lines and primary leukemic cells without inducing overt cell death. Statins and agents that selectively reduce intracellular cholesterol levels, but not the inhibition of protein farnesylation or geranylgeranylation, induced autophagy in leukemic cells. The observed autophagic response was associated with the reduction of phosphorylated Akt levels in the lipid rafts, accompanied by a decrease in the activation of the main autophagy suppressor mammalian target of rapamycin (mTOR) and its substrate ribosomal p70S6 kinase (p70S6K). No significant autophagy induction and downregulation of mTOR/p70S6K activation were observed in normal leukocytes. Autophagy suppression by bafilomycin A1 or RNA interference-mediated knockdown of beclin-1 and microtubule-associated protein 1 light chain 3B induced apoptotic death in statin-treated leukemic cells, an effect attenuated by the addition of mevalonate or squalene, but not farnesylpyrophosphate or geranylgeranylpyrophosphate. Therefore, while the inhibition of cholesterol synthesis, protein farnesylation, and geranylgeranylation all contributed to anti-leukemic effects of statins, the inhibition of cholesterol synthesis was solely responsible for the induction of cytoprotective autophagy. These data indicate that combined treatment with statins and autophagy inhibitors might be potentially useful in anti-leukemic therapy.
他汀类药物通过抑制3-羟基-3-甲基戊二酰辅酶A还原酶来抑制甲羟戊酸途径，进而使胆固醇、法尼基焦磷酸和香叶基香叶基焦磷酸耗竭，从而展现出抗白血病特性。我们研究了自噬（一种受调控的细胞内自我消化过程）在他汀类药物抗白血病作用中的角色。用低浓度（≤6 µM）的他汀类药物处理、胆固醇耗竭以及对胆固醇合成和蛋白质法尼基化或香叶基香叶基化的特异性抑制，均能抑制白血病细胞系和原代白血病细胞的增殖，且不会诱导明显的细胞死亡。他汀类药物以及能选择性降低细胞内胆固醇水平的药物，但不是抑制蛋白质法尼基化或香叶基香叶基化的药物，可诱导白血病细胞发生自噬。观察到的自噬反应与脂筏中磷酸化Akt水平的降低相关，同时伴随着主要自噬抑制因子雷帕霉素哺乳动物靶标（mTOR）及其底物核糖体p70S6激酶（p70S6K）的激活减少。在正常白细胞中未观察到明显的自噬诱导以及mTOR/p70S6K激活的下调。用巴弗洛霉素A1抑制自噬或通过RNA干扰介导敲低贝克林1和微管相关蛋白1轻链3B可诱导他汀类药物处理的白血病细胞发生凋亡性死亡，添加甲羟戊酸或角鲨烯可减弱这种效应，但添加法尼基焦磷酸或香叶基香叶基焦磷酸则不能。因此，虽然胆固醇合成、蛋白质法尼基化和香叶基香叶基化的抑制均有助于他汀类药物的抗白血病作用，但胆固醇合成的抑制是诱导细胞保护性自噬的唯一原因。这些数据表明，他汀类药物与自噬抑制剂联合治疗可能在抗白血病治疗中具有潜在用途。
