Open Access Research

Silvestrol exhibits significant in vivo and in vitro antileukemic activities and inhibits FLT3 and miR-155 expressions in acute myeloid leukemia

Houda Alachkar14, Ramasamy Santhanam14, Jason G Harb24, David M Lucas14, Joshua J Oaks24, Christopher J Hickey14, Li Pan3, A Douglas Kinghorn3, Michael A Caligiuri14, Danilo Perrotti24, John C Byrd14, Ramiro Garzon14, Michael R Grever146* and Guido Marcucci145*

Author Affiliations

1 Division of Hematology, Department of Medicine, The Ohio State University, Columbus, OH, USA

2 Department of Molecular Virology, Immunology and Cancer Genetics, The Ohio State University, Columbus, OH, USA

3 Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA

4 Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA

5 The Ohio State University Comprehensive Cancer Center, Biomedical Research Tower 460 W. 12th Ave, Columbus, OH, 43210, USA

6 395 West Twelfth Avenue, Rm. 392 North Doan Office Tower, Columbus, OH, 43210, USA

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Journal of Hematology & Oncology 2013, 6:21  doi:10.1186/1756-8722-6-21

Published: 16 March 2013

Abstract

Background

Activating mutations [internal tandem duplication (ITD)] or overexpression of the FMS-like tyrosine kinase receptor-3 (FLT3) gene are associated with poor outcome in acute myeloid leukemia (AML) patients, underscoring the need for novel therapeutic approaches. The natural product silvestrol has potent antitumor activity in several malignancies, but its therapeutic impact on distinct molecular high-risk AML subsets remains to be fully investigated. We examined here the preclinical activity of silvestrol in FLT3-ITD and FLT3 wild-type (wt) AML.

Methods

Silvestrol in vitro anti-leukemic activity was examined by colorimetric cell viability assay, colony-forming and flow cytometry assays assessing growth inhibition and apoptosis, respectively. Pharmacological activity of silvestrol on FLT3 mRNA translation, mRNA and protein expression was determined by RNA-immunoprecipitation, qRT-PCR and immunoblot analyses, respectively. Silvestrol in vivo efficacy was investigated using MV4-11 leukemia-engrafted mice.

Results

Silvestrol shows antileukemia activity at nanomolar concentrations both in FLT3-wt overexpressing (THP-1) and FLT3-ITD (MV4-11) expressing AML cell lines (IC50 = 3.8 and 2.7 nM, respectively) and patients’ primary blasts [IC50 = ~12 nM (FLT3-wt) and ~5 nM (FLT3-ITD)]. Silvestrol increased apoptosis (~4fold, P = 0.0001), and inhibited colony-formation (100%, P < 0.0001) in primary blasts. Silvestrol efficiently inhibited FLT3 translation reducing FLT3 protein expression by 80–90% and decreased miR-155 levels (~60%), a frequently co-regulated onco-miR in FLT3-ITD-positive AML. The median survival of silvestrol-treated vs vehicle-treated mice was 63 vs 29 days post-engraftment, respectively (P < 0.0001).

Conclusions

Silvestrol exhibits significant in vivo and in vitro antileukemic activities in AML through a novel mechanism resulting in inhibition of FLT3 and miR-155 expression. These encouraging results warrant a rapid translation of silvestrol for clinical testing in AML.