312636-16-1

Selective non-lipid inhibitor of sphingosine kinase (IC 50 = 0.5 μ M); does not act at ATP-binding site. Displays no inhibition of ERK2, PI 3-kinase, or PKC α at concentrations up to 60 μ M. Reduces levels of sphingosine-1-phosphate in MDA-MB-231 breast cancer cells. Induces apoptosis and inhibits proliferation in several other tumor cell lines in vitro (IC 50 = 0.9-4.6 μ M).

SKI II [2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole] is a small-molecule inhibitor originally identified as a selective sphingosine kinase 1 (SK1) inhibitor. Although initially considered to directly inhibit SK1 activity, later studies revealed that its primary mode of action is to induce lysosomal, cathepsin B-dependent degradation of SK1 protein without altering SK1 mRNA expression. As a result, SKI II suppresses cellular SK1 activity mainly by reducing protein abundance through a post-translational mechanism rather than by directly inhibiting enzyme catalysis[3].

Selective, non-ATP competitive inhibitor of sphingosine kinase (IC50 = 0.5μM GST-hSK; IC50 = 1.1μM intact JC mouse mammary adenovirus carcinoma cells) showing no inhibition of hERK2, hPI3k and hPKCα at concentrations up to 60μM. Cytotoxic effects have been demonstrated against various tumor cell lines including some overexpressing P-glycoprotein or MRP1 (T24, IC50 = 4.6μM; MCF-7, IC50 = 1.2μM; NCI/ADR, IC50 = 1.3μM, MCRF-7/VP, IC50 = 0.9μM). Induced apoptosis in T24 tumor cells.

ChEBI: 4-[[4-(4-chlorophenyl)-2-thiazolyl]amino]phenol is a substituted aniline.

Sphingosine kinase (SK) plays a pivotal role in regulating tumor growth and SK can act as an oncogene. Expression of SK RNA is significantly elevated in a variety of solid tumors, compared with normal tissue from the same patient. A number of novel inhibitors of human SK were identified, and several representative compounds were characterized in detail. These compounds demonstrated activity at sub- to micromolar concentrations, making them more potent than any other reported SK inhibitor, and were selective toward SK compared with a panel of human lipid and protein kinases. Kinetic studies revealed that the compounds were not competitive inhibitors of the ATP-binding site of SK. 4-[4-(4-chloro-phenyl)-thiazol-2-ylamino]-phenol (SKI-II) inhibitor is orally bioavailable, detected in the blood for at least 8 h, and showed a significant inhibition of tumor growth in mice with IC50 = 0.5 μM; SKI II does not act at ATP-binding site. Displays no inhibition of ERK2, PI 3-kinase, or PKCa at concentrations up to 60 μM.SKI II induces apoptosis and inhibits proliferation in several other tumor cell lines in vitro (IC50 = 0.9-4.6 μM).

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[1] french kj, schrecengost rs, lee bd, zhuang y, smith sn, eberly jl, yun jk, smith cd. discovery and evaluation of inhibitors of human sphingosine kinase. cancer res. 2003 sep 15;63(18):5962-9.