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Positron emission tomographic monitoring of dual phosphatidylinositol-3-kinase and mTOR inhibition in anaplastic large cell lymphoma

Authors Graf N, Li Z, Herrmann K, Weh D, Aichler M, Slawska J, Walch A, Peschel C, Schwaiger M, Buck A, Dechow T, Keller U

Received 17 December 2013

Accepted for publication 7 February 2014

Published 23 May 2014 Volume 2014:7 Pages 789—798

DOI https://doi.org/10.2147/OTT.S59314

Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 2


Nicolas Graf,1 Zhoulei Li,2 Ken Herrmann,2,4 Daniel Weh,2 Michaela Aichler,3 Jolanta Slawska,2 Axel Walch,3 Christian Peschel,1 Markus Schwaiger,2 Andreas K Buck,2,4 Tobias Dechow,1,* Ulrich Keller1,*

1III Medical Department, 2Department of Nuclear Medicine, Technische Universität München, Munich, Germany; 3Research Unit Analytical Pathology, Helmholtz Zentrum München, Munich, Germany; 4Department of Nuclear Medicine, Universitätsklinikum Würzburg, Würzburg, Germany

*These authors contributed equally to this work

Background: Dual phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibition offers an attractive therapeutic strategy in anaplastic large cell lymphoma depending on oncogenic nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) signaling. We tested the efficacy of a novel dual PI3K/mTOR inhibitor, NVP-BGT226 (BGT226), in two anaplastic large cell lymphoma cell lines in vitro and in vivo and performed an early response evaluation with positron emission tomography (PET) imaging using the standard tracer, 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and the thymidine analog, 3'-deoxy-3'-[18F]fluorothymidine (FLT).
Methods: The biological effects of BGT226 were determined in vitro in the NPM-ALK positive cell lines SU-DHL-1 and Karpas299 by 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, propidium iodide staining, and biochemical analysis of PI3K and mTOR downstream signaling. FDG-PET and FLT-PET were performed in immunodeficient mice bearing either SU-DHL-1 or Karpas299 xenografts at baseline and 7 days after initiation of treatment with BGT226. Lymphomas were removed for immunohistochemical analysis of proliferation and apoptosis to correlate PET findings with in vivo treatment effects.
Results: SU-DHL-1 cells showed sensitivity to BGT226 in vitro, with cell cycle arrest in G0/G1 phase and an IC50 in the low nanomolar range, in contrast with Karpas299 cells, which were mainly resistant to BGT226. In vivo, both FDG-PET and FLT-PET discriminated sensitive from resistant lymphoma, as indicated by a significant reduction of tumor-to-background ratios on day 7 in treated SU-DHL-1 lymphoma-bearing animals compared with the control group, but not in animals with Karpas299 xenografts. Imaging results correlated with a marked decrease in the proliferation marker Ki67, and a slight increase in the apoptotic marker, cleaved caspase 3, as revealed by immunostaining of explanted lymphoma tissue.
Conclusion: Dual PI3K/mTOR inhibition using BGT226 is effective in ALK-positive anaplastic large cell lymphoma and can be monitored with both FDG-PET and FLT-PET early on in the course of therapy.

Keywords: lymphoma, phosphatidylinositol-3-kinase, mammalian target of rapamycin, inhibition, positron emission tomography


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