The dynamic balance of cellular sphingolipids, the sphingolipid rheostat, is an important determinant of cell fate, and is commonly deregulated in cancer. buy pirinixic acid (WY 14643) for anti-cancer therapy, and represents an important experimental tool to study these enzymes. docking, molecular modeling, small molecule inhibitor, sphingosine kinase INTRODUCTION buy pirinixic acid (WY 14643) A number of sphingolipids, including ceramide, sphingosine and sphingosine 1-phosphate (S1P), are important signaling molecules controlling a diverse array of important cell processes [1]. S1P, in particular, has diverse cell signaling functions through its actions as both a ligand for a family of five S1P-specific G protein-coupled receptors (named H1P1C5), as well as a modulator of a range of intracellular protein [2C4]. S1P receptor-mediated signaling most particularly plays significant functions in immune cell trafficking and vascular honesty, while S1P in general confers pro-proliferative, pro-survival signaling [5]. Sphingosine and many ceramide species, however, are pro-apoptotic, modulating the activity of a range of enzymes involved in the control of cell survival [5]. Thus, the balance between the cellular levels of S1P and ceramide/sphingosine, the so-called sphingolipid rheostat, appears an important regulator of cell fate. The cellular levels of the sphingolipids are controlled by an array of bidirectional metabolic pathways that are subject to complex spatial and temporal rules [1, 6]. Some of the most important regulators of this system are the sphingosine kinases (SKs), which, through their action of phosphorylating sphingosine to generate S1P, play a vital role in controlling the sphingolipid rheostat [1], and therefore, cell fate. Two SKs exist in mammals; SK1 and SK2, which catalyze the same reaction and share a high degree of sequence similarity. The two SKs share some redundant and related functions, but also appear to possess some different functions, probably due to their different subcellular buy pirinixic acid (WY 14643) localizations, with SK1 predominantly localized to the cytoplasm while SK2 is usually mainly localized at the nucleus and other organelles [7]. The SKs have been widely implicated in carcinogenesis. SK1 manifestation is usually elevated in a wide array of human solid cancers, with higher levels of SK1 correlating with the severity of malignancy and shorter patient survival [8]. Similarly, SK2 was recently found to be elevated in human non-small cell lung malignancy, with high manifestation levels buy pirinixic acid (WY 14643) correlated with poor patient survival [9]. Furthermore, a large number of studies have shown that targeting SKs has considerable potential as an anti-cancer strategy. For example, RNAi-mediated Mouse monoclonal to SORL1 knockdown or inhibition of SK1 and SK2 has been widely exhibited to induce apoptosis and enhance sensitivity to chemo- or radiation therapy of many different malignancy cells [10, 11]. Similarly, genetic ablation of SK1 and SK2 in mice was found to reduce tumor growth in numerous malignancy models [12C19]. This body of evidence has secured the SKs as encouraging therapeutic targets in malignancy and has driven drug development to target the enzymes in a range of malignancy buy pirinixic acid (WY 14643) models [10, 11]. Initial SK inhibitor development used molecules produced from sphingosine including L-and decreases in S1P in cells, these inhibitors failed to induce apoptosis or show anti-neoplastic properties [25C27]. This has lead to the groups that developed these reagents to reach the contentious conclusion that SK activity is usually not required for tumor cell viability [26], despite the large body of evidence to the in contrast. Particularly, unlike other SK inhibitors or SK knockdown, these recent inhibitors failed to enhance cellular ceramide levels at low concentrations where SK1 was inhibited [25C27]. This suggests the similarity of these molecules to sphingosine may result in off-target inhibition of ceramide synthases which hindrances ceramide generation and associated pro-apoptotic signaling. Here we describe the finding and characterization of a novel SK inhibitor, MP-A08, using a structure-based approach to target the ATP-binding pocket of SK1. Via this approach we both exploit the known divergence of the SK ATP-binding site from other kinases [28] and also overcome common off-target effects of sphingosine-like molecules. Characterization of MP-A08 exhibited its high selectivity to SK1 and SK2 over other kinases, and importantly revealed its anti-neoplastic effects against a panel of malignancy cell lines and also in human lung tumor xenografts in mice. RESULTS Modeling and affirmation of the ATP-binding pocket of SK1 Until recently there was no structural information available for SK1. Therefore, we employed homology modeling to forecast the structure of the ATP-binding pocket of SK1 using the solved structures of two.