SKI II is an inhibitor of sphingosine kinase with IC50 value of 0.5μM[1].
SKI II is selective against SK and has no inhibition of human protein kinases ERK2, PKC-I and the lipid kinase PI3K. It is reported that SKI II is not a competitive inhibitor at the ATP-binding site of SK. SKI II also inhibits endogenous SK in intact MDA-MB-231 cells [1].
As a SK inhibitor, SKI II prevents SK from catalyzing the generation of sphingosine 1-phosphate (S1P). The blockage of S1P formation leads to inhibition of proliferation, as well as the induction of apoptosis in cancer cells. SKI II shows cytotoxicity in T-24 human bladder carcinoma cells, MCF-7 human breast adenocarcinoma cells and the subline of MCF-7 cells, MCF-7/VP, with IC50 values of 4.6μM, 1.2μM and 0.9μM, respectively [1].
References:
[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.