Germano Concetta Anna, Clemente Giuseppe, Storniolo Antonello, Romeo Maria Anele, Ferretti Elisabetta, Cirone Mara, Di Renzo Livia
Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Rome, Italy.
Biology (Basel). 2023 May 2;12(5):676. doi: 10.3390/biology12050676.
mTOR is constitutively activated in acute myeloid leukemia (AML) cells, as indicated by the phosphorylation of its substrates, 4EBP1 and P70S6K. Here, we found that quercetin (Q) and rapamycin (Rap) inhibited P70S6K phosphorylation, partially dephosphorylated 4EBP1, and activated ERK1/2 in U937 and THP1, two leukemia cell lines. ERK1/2 inhibition by U0126 induced a stronger dephosphorylation of mTORC1 substrates and activated AKT. The concomitant inhibition of ERK1/2 and AKT further dephosphorylated 4EBP1 and further increased Q- or Rap-mediated cytotoxicity, compared to the single ERK1/2 or AKT inhibition in cells undergoing Q- or Rap-treatments. Moreover, quercetin or rapamycin reduced autophagy, particularly when used in combination with the ERK1/2 inhibitor, U0126. This effect was not dependent on TFEB localization in nuclei or cytoplasm or on the transcription of different autophagy genes, but did correlate with the reduction in protein translation due to a strong eIF2α-Ser51 phosphorylation. Thus, ERK1/2, by limiting 4EBP1 de-phosphorylation and eIF2α phosphorylation, behaves as a paladin of protein synthesis. Based on these findings, the combined inhibition of mTORC1, ERK1/2, and AKT should be considered in treatment of AML.
mTOR在急性髓系白血病（AML）细胞中持续激活，这可通过其底物4EBP1和P70S6K的磷酸化来表明。在此，我们发现槲皮素（Q）和雷帕霉素（Rap）抑制U937和THP1这两种白血病细胞系中P70S6K的磷酸化，使4EBP1部分去磷酸化，并激活ERK1/2。U0126对ERK1/2的抑制诱导mTORC1底物更强的去磷酸化并激活AKT。与在接受Q或Rap处理的细胞中单独抑制ERK1/2或AKT相比，同时抑制ERK1/2和AKT可进一步使4EBP1去磷酸化，并进一步增强Q或Rap介导的细胞毒性。此外，槲皮素或雷帕霉素可减少自噬，特别是与ERK1/2抑制剂U0126联合使用时。这种效应不依赖于TFEB在细胞核或细胞质中的定位，也不依赖于不同自噬基因的转录，但确实与由于eIF2α-Ser51强烈磷酸化导致的蛋白质翻译减少相关。因此，ERK1/2通过限制4EBP1的去磷酸化和eIF2α磷酸化，起到蛋白质合成保护者的作用。基于这些发现，在AML治疗中应考虑联合抑制mTORC1、ERK1/2和AKT。
