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Leukemia. 2014 Nov;28(11):2197-205. doi: 10.1038/leu.2014.123. Epub 2014 Apr 4.

Feedbacks and adaptive capabilities of the PI3K/Akt/mTOR axis in acute myeloid leukemia revealed by pathway selective inhibition and phosphoproteome analysis.

Author information

1
1] Department of Surgery, Medicine, Dentistry and Morphology, University of Modena and Reggio Emilia, Modena, Italy [2] Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
2
Department of Surgery, Medicine, Dentistry and Morphology, University of Modena and Reggio Emilia, Modena, Italy.
3
Department of Woman's and Child's Health, University of Padova, Padova, Italy.
4
Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
5
Section of Hematology, Department of Medical and Surgical Science, University of Modena and Reggio Emilia, Modena, Italy.
6
Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, VA, USA.

Abstract

Acute myeloid leukemia (AML) primary cells express high levels of phosphorylated Akt, a master regulator of cellular functions regarded as a promising drug target. By means of reverse phase protein arrays, we examined the response of 80 samples of primary cells from AML patients to selective inhibitors of the phosphatidylinositol 3 kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) axis. We confirm that >60% of the samples analyzed are characterized by high pathway phosphorylation. Unexpectedly, however, we show here that targeting Akt and mTOR with the specific inhibitors Akti 1/2 and Torin1, alone or in combination, result in paradoxical Akt phosphorylation and activation of downstream signaling in 70% of the samples. Indeed, we demonstrate that cropping Akt or mTOR activity can stabilize the Akt/mTOR downstream effectors Forkhead box O and insulin receptor substrate-1, which in turn potentiate signaling through upregulation of the expression/phosphorylation of selected growth factor receptor tyrosine kinases (RTKs). Activation of RTKs in turn reactivates PI3K and downstream signaling, thus overruling the action of the drugs. We finally demonstrate that dual inhibition of Akt and RTKs displays strong synergistic cytotoxic effects in AML cells and downmodulates Akt signaling to a much greater extent than either drug alone, and should therefore be explored in AML clinical setting.

PMID:
24699302
DOI:
10.1038/leu.2014.123
[Indexed for MEDLINE]

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