Fuka G, Kantner HP, Grausenburger R, Inthal A, Bauer E, Krapf G, Kaindl U, Kauer M, Dworzak MN, Stoiber D, Haas OA, Panzer-Grümayer R. Silencing of ETV6/RUNX1 abrogates PI3K/AKT/mTOR signaling and impairs reconstitution of leukemia in xenografts.
Leukemia 2012;
26:927-33. [PMID:
22094587 DOI:
10.1038/leu.2011.322]
[Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 06/01/2011] [Accepted: 10/07/2011] [Indexed: 12/21/2022]
Abstract
The ETV6/RUNX1 (E/R) gene fusion is generated by the t(12;21) and found in approximately 25% of childhood B-cell precursor acute lymphoblastic leukemia. In contrast to the overwhelming evidence that E/R is critical for the initiation of leukemia, its relevance for the maintenance of overt disease is less clear. To investigate this issue, we suppressed the endogenous E/R fusion protein with lentivirally transduced short hairpin RNA in the leukemia cell lines REH and AT-2, and found a distinct reduction of proliferation and cell survival. In line with the observed concurrent inactivation of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, pharmacological inhibition diminished the phosphorylation of AKT and ribosomal protein S6, and significantly increased the apoptosis rate in E/R-positive leukemias. Moreover, PI3K/mTOR inhibitors sensitized glucocorticoid-resistant REH cells to prednisolone, an observation of potential relevance for improving treatment of drug-resistant relapses. Of note, knockdown of the E/R fusion gene also severely impaired the repopulation capacity of REH cells in non-obese deficient/severe combined immunodeficient mice. Collectively, these data demonstrate that the E/R fusion protein activates the PI3K/AKT/mTOR pathway and is indispensible for disease maintenance. Importantly, these results provide a first rationale and justification for targeting the fusion gene and the PI3K/AKT/mTOR pathway therapeutically.
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