Co-Administration Of The MTORC1/TORC2 Inhibitor INK128 And The Bcl-2/Bcl-XL Antagonist ABT-737 Kills Human Myeloid Leukemia Cells Through Mcl-1 Down-Regulation And AKT Inactivation

Authors

Mohamed Rahmani, Virginia Commonwealth UniversityFollow
Mandy Mayo Aust, Virginia Commonwealth University
Elisa Hawkins, Virginia Commonwealth UniversityFollow
Rebecca E. Parker, Virginia Commonwealth UniversityFollow
Masey Ross, Virginia Commonwealth UniversityFollow
Maciej Kmieciak, Virginia Commonwealth UniversityFollow
Leonid Borisovich Reshko, Virginia Commonwealth UniversityFollow
Kathryn A. Rizzo, Virginia Commonwealth UniversityFollow
Catherine I. Dumur, Virginia Commonwealth UniversityFollow
Andrea Ferreira-Gonzalez, Virginia Commonwealth UniversityFollow
Steven Grant, Virginia Commonwealth UniversityFollow

Document Type

Article

Original Publication Date

2015

Journal/Book/Conference Title

Haematologica

Volume

100

Issue

12

DOI of Original Publication

10.3324/haematol.2015.130351

Comments

Originally published at http://dx.doi.org/10.3324/haematol.2015.130351

Date of Submission

April 2016

Abstract

Effects of concurrent inhibition of mTORC1/2 and Bcl-2/Bcl-xL in human acute myeloid leukemia cells were examined. Tetracycline-inducible Bcl-2/Bcl-xL dual knockdown markedly sensitized acute myeloid leukemia cells to the dual TORC1/2 inhibitor INK128 in vitro as well as in vivo. Moreover, INK128 co-administered with the Bcl-2/xL antagonist ABT-737 sharply induced cell death in multiple acute myeloid leukemia cell lines, including TKI-resistant FLT3-ITD mutants and primary acute myeloid leukemia blasts carrying various genetic aberrations e.g., FLT3, IDH2, NPM1, and Kras, while exerting minimal toxicity toward normal hematopoietic CD34+ cells. Combined treatment was particularly active against CD34+/CD38−/CD123+ primitive leukemic progenitor cells. The INK128/ABT-737 regimen was also effective in the presence of a protective stromal microenvironment. Notably, INK128 was more potent than the TORC1 inhibitor rapamycin in down-regulating Mcl-1, diminishing AKT and 4EBP1 phosphorylation, and potentiating ABT-737 activity. Mcl-1 ectopic expression dramatically attenuated INK128/ABT-737 lethality, indicating an important functional role for Mcl-1 down-regulation in INK128/ABT-737 actions. Immunoprecipitation analysis revealed that combined treatment markedly diminished Bax, Bak, and Bim binding to all major anti-apoptotic Bcl-2 members (Bcl-2/Bcl-xL/Mcl-1), while Bax/Bak knockdown reduced cell death. Finally, INK128/ABT-737 co-administration sharply attenuated leukemia growth and significantly prolonged survival in a systemic acute myeloid leukemia xenograft model. Analysis of subcutaneous acute myeloid leukemia-derived tumors revealed significant decrease in 4EBP1 phosphorylation and Mcl-1 protein level, consistent with results obtained in vitro. These findings demonstrate that co-administration of dual mTORC1/mTORC2 inhibitors and BH3-mimetics exhibits potent anti-leukemic activity in vitro and in vivo, arguing that this strategy warrants attention in acute myeloid leukemia.

Rights

Copyright© Ferrata Storti Foundation

Is Part Of

VCU Internal Medicine Publications