Biological Characterization of 3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145) as a Selective Sphingosine Kinase-2 Inhibitor and Anticancer Agent

Kai Liu,Nitai C Hait,Sarah Spiegel,Glen E Kellogg,Steven Grant,Wenfang Xu,Tai L Guo,Jeremy Allegood,Shijun Zhang,Hardik I Parikh,Zhaozhong Han

doi:10.1371/journal.pone.0056471

Abstract

In our effort to develop selective sphingosine kinase-2 (SphK2) inhibitors as pharmacological tools, a thiazolidine-2,4-dione analogue, 3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145), was synthesized and biologically characterized. Biochemical assay results indicate that K145 is a selective SphK2 inhibitor. Molecular modeling studies also support this notion. In vitro studies using human leukemia U937 cells demonstrated that K145 accumulates in U937 cells, suppresses the S1P level, and inhibits SphK2. K145 also exhibited inhibitory effects on the growth of U937 cells as well as apoptotic effects in U937 cells, and that these effects may be through the inhibition of down-stream ERK and Akt signaling pathways. K145 also significantly inhibited the growth of U937 tumors in nude mice by both intraperitoneal and oral administration, thus demonstrating its in vivo efficacy as a potential lead anticancer agent. The antitumor activity of K145 was also confirmed in a syngeneic mouse model by implanting murine breast cancer JC cells in BALB/c mice. Collectively, these results strongly encourage further optimization of K145 as a novel lead compound for development of more potent and selective SphK2 inhibitors.

Highlights

Sphingosine-1-phosphate (S1P), a lipid metabolite, has been recently demonstrated to be an important signaling mediator for vital cellular and physiological processes, such as cell motility, invasion, proliferation, angiogenesis and apoptosis [1,2]
In vitro Studies After synthesis, we first examined the effects of K145 on recombinant sphingosine kinase-1 (SphK1) and sphingosine kinase-2 (SphK2)
Molecular modeling and docking studies suggested that K145 favorably binds to SphK2 but not SphK1 within their respective sphingosine binding pockets, consistent with the biochemical assay results

Summary

Introduction

Sphingosine-1-phosphate (S1P), a lipid metabolite, has been recently demonstrated to be an important signaling mediator for vital cellular and physiological processes, such as cell motility, invasion, proliferation, angiogenesis and apoptosis [1,2]. Evidence has accumulated that SphK1 promotes cell growth and survival, and has been associated with many aspects of cancer development and progression, such as proliferation, migration, invasion and angiogenesis [14]. HDAC has been identified as an intracellular target of S1P, which is mainly produced by SphK2 within the nucleus and indicates a potential role of SphK2 in histone acetylation, gene expression, and cancer pathology [6]. SphK2 has been demonstrated to play important roles in the function of mitochondria [21] Even with these very recent advances in understanding of SphK2, much is still unknown or controversial about this kinase. Development of selective SphK2 inhibitors would be of great value as pharmacological tools to complement the ongoing molecular and genetic studies, and help unravel the roles of SphK2 in different pathological and physiological conditions. It would be of great value to have new and adaptable chemical scaffolds available as selective SphK2 inhibitors as this would help unravel the structural requirements for designing new SphK2 inhibitors

Methods

Results

Conclusion