Abstract
We previously developed SKI-178 (N′-[(1E)-1-(3,4-dimethoxyphenyl)ethylidene]-3-(4-methoxxyphenyl)-1H-pyrazole-5-carbohydrazide) as a novel sphingosine kinase-1 (SphK1) selective inhibitor and, herein, sought to determine the mechanism-of-action of SKI-178–induced cell death. Using human acute myeloid leukemia (AML) cell lines as a model, we present evidence that SKI-178 induces prolonged mitosis followed by apoptotic cell death through the intrinsic apoptotic cascade. Further examination of the mechanism of action of SKI-178 implicated c-Jun NH2-terminal kinase (JNK) and cyclin-dependent protein kinase 1 (CDK1) as critical factors required for SKI-178–induced apoptosis. In cell cycle synchronized human AML cell lines, we demonstrate that entry into mitosis is required for apoptotic induction by SKI-178 and that CDK1, not JNK, is required for SKI-178–induced apoptosis. We further demonstrate that the sustained activation of CDK1 during prolonged mitosis, mediated by SKI-178, leads to the simultaneous phosphorylation of the prosurvival Bcl-2 family members, Bcl-2 and Bcl-xl, as well as the phosphorylation and subsequent degradation of Mcl-1. Moreover, multidrug resistance mediated by multidrug-resistant protein1 and/or prosurvival Bcl-2 family member overexpression did not affect the sensitivity of AML cells to SKI-178. Taken together, these findings highlight the therapeutic potential of SKI-178 targeting SphK1 as a novel therapeutic agent for the treatment of AML, including multidrug-resistant/recurrent AML subtypes.
Footnotes
- Received August 29, 2014.
- Accepted January 5, 2015.
T.E.D. and J.A.H. contributed equally to this work
Support for this study was provided by Penn State Hershey College of Medicine; Penn State Hershey Cancer Institute; Jake Gittlen Cancer Research Foundation; the National Institutes of Health National Cancer Institute [Grant P01-CA171983]; and the Pennsylvania Department of Health (SAP# 4100054865).
This work was previously presented as a poster at the following workshop: Dick T, Hengst J, Fox T, Colledge A, Kale V, Sung SS, Amin S, Loughran T, Kester M, Wang HG, and Yun J (2013) Novel sphingosine kinase 1 selective inhibitor, SKI-178, induces apoptotic cell death through prolonged activation of CDK1. 7th International Ceramide Conference; 2013 Oct 20–24; Montauk, NY.
↵This article has supplemental material available at jpet.aspetjournals.org.
- Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|